ng dung mang no ron nhan tao trong du bao ngan
DESCRIPTION
ung dung mang no ronTRANSCRIPT
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B GIO DC V O TO
TRNG I HC NNG NGHIP I ------------ c a -------------
DIP XUN TRNG
NG DNG MNG N RON NHN TO TRONG D BO NGN HAN PHU TI IN
KHU Vc TNH SC TRNG
LUN VN THC s K THUT
H NI - 2007
Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
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B GIO DC V O TO
TRNG I HC NNG NGHIP I ------------ c a -------------
DIP XUN TRNG
NG DUNG MANG N RON NHN TAO TRONG D BO NGN HN PH TI IN
KHU vc TNH SC TRNG
LUN VN THC s K THUT
Chuyn ngnh: in kh ho sn xut nng nghip v nng thn
M s: 60 52 54
N gi hng dn khoa hc: TSK H TR N H O I LINH
H NI - 2007
Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
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LI CAM OAN
Ti xin cam oan y l cng trnh nghin cu ca ring ti. Cc s liu, kt qu
nu ong lun vn l trung thc v cha tng c ai cng b ong bt k cng trnh
no khc.
Ti xin cam oan rng cc thng tin trch dn trong lun vn u c ch r
ngun gc.
Hc vin
Dip Xun Trng
iTrng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
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LI CM N
Sau hn hai nm hc tp v nghin cu ti Trng i hc Nng Nghip I vi
mc ch l nng cao kin thc ca bn thn v honh thnh lun vn cao hc, ti
nhn c s quan tm gip to ln v tn tnh ca cc thy c gio v bn b cng
lp. Cho php ti c by t cm n su sc n thy gio hng dn: Tin s khoa
hc Trn Hoi Linh, ngi tn tnh hng dn, ch bo v gip ti hon thnh
lun vn. Trong thi gian hc tp ti trng ti xin cm n n cc thy c gio trc
tip ging dy v ch bo ti.
Xin chn thnh cm n K s Nguyn Vn Nhim v cc anh ch vn hnh Trm
bin p 220 k v ca Cng ty in lc Sc Trng gip v to iu kin cho ti
lm vic.
Xin c by t s cm n n cc cn b khoa Sau i hc, Cc cn b b mn
Cung cp v S dng in cng nh cc hc vin lp cao hc C in 14 quan tm
gip , to iu kin cho ti hc tp v nghin cu.
Chn thnh cm n cc cn b Vin C in Nng Nghip v Cng ngh Sau thu
hoch n v qun l to iu kin tt nht cho ti hon thnh kho hc.
Ti v cng bit n nhng ngi thn trong gia nh quan tm, ng vin v l
ch da tinh thn vng chc gip ti hon thnh lun vn ny.
H ni, thng 9 nm 2007
Hc vin
Dip Xun Trng
iiTrng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
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Li cam oan i
Li cm n ii
Mc lc iii
Bng k hiu vi
Danh mc hnh vii
Danh mc bng X
M u 1
Chng l Nhu cu thc tin v d bo ph ti in v mt s phng
php d bo hin c 7
1.1 Nhu cu thc tin v d bo ph ti in 7
1.2 Cc phng php d bo ang c nghin cu v ng dng 9
1.2.1 Phn loi cc phng php d bo ph ti in 9
1.2.2 Mt s phng php d bo in hnh 10
1.3 C s xy dng phng php d bo ph ti mi s dng mng
n ron nhn to 13
Chng 2. Gii thiu v mng n ron nhn to 14
2.1 Tr tu nhn to 14
2.2 N ron sinh hc 15
2.3 Mng n ron nhn to 16
2.3.1 Lch s hnh thnh v pht trin 17
2.3.2 M hnh mng n ron nhn to 17
2.3.3 Cc hm kch hot 19
2.3.4 Phn loi cc mng n ron 21
2.4 Hun luyn mng n ron 22
2.5 Hm mc tiu 24
2.6 Mt s ng dng ca mng n ron 25
MC LC
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Chng 3 c im biu ph ti tnh Sc Trng 27
3.1 Biu ph ti in 27
3.2 Cc yu t nh hng n ph ti in 28
3.3 Dng biu ph ti 35
3.4 nh v y biu ph ti 3 6
Chng 4. n g dng mng n ron nhn to trong bi ton
phn loi kiu ngy 38
4.1 i tng phn loi 38
4.2 Phng php phn loi dng biu ph ti 38
4.3 Mng Kohonen v ng dng trong phn loi kiu ngy 39
4.3.1 Gii thiu 39
4.3.2 Thut gii SOM 40
4.4 Phng php trng tm m ng dng phn loi kiu ngy 41
4.5 n g dng thut ton v chy th mng 43
4.5.1 X l s liu thu thp 43
4.5.2 Phn nhm biu ph ti 44
4.6 Xy dng giao din d bo hnh dng biu ph ti 50
Chng 5. Xc nh cc thng s u vo cho mng MLP v thut ton
Levenberg - Martquardt 53
5.1 La chn cc thng s u vo phc v qu trnh hun luyn
mng n ron 53
5.1.1 Phn tch tng quan 54
5.1.2 Tm h s tng quan gia cng sut vi cng sut
trong qu kh 56
5.1.3 Mt s kt qu thu c 57
5.2 La chn mng n ron cho bi ton d bo nh v y BPT 62
5.2.1 Mng Perceptron MLP 62
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5.2.2 Thut ton Levenberg Marquardt 65
5.3 S lc v bi ton d bo d liu 68
Chng 6 Kt qu tnh ton m phng 73
6.1 Xy dng m hnh d bo ph ti cao im v thp im 73
6.2 Phng thc xy dng m hnh 73
6.3 Cc bc tin hnh hun luyn mng vi m hnh 3 75
6.3.1 Xy dng mng d bo nh BPT 75
6.3.2 Xy dng mng d bo y BPT 81
6.4 Xy dng mng cho m hnh 1 83
6.4.1 Cc m hnh d bo nh BPT 83
6.4.2 Cc m hnh d bo y BPT 84
6.5 Xy dng mng cho m hnh 2 85
6.5.1 Cc m hnh d bo nh BPT 85
6.5.2 Cc m hnh d bo y BPT 86
6.6 Tin hnh d bo Pmax Pmin v nh gi sai s 88
6.7 D bo ph ti cho 24 gi sau 91
6.8 Xy dng giao din phn mm d bo BPT 100
Kt lun v kin ngh 104
Ti liu tham kho 108
Ph lc I: 110
Ph lc II: 111
V
Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
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CC T VIT TT
HT: H thng in
MNR: Mng n ron
FCM: Phng php trng tm m (Fuzzy Clustering Method)
SOM: Self-Organizing Maps
MBU: Mau khp tt nht (Best Matching Unit)
Pmax: Ph ti cao im
Pmin: Ph ti thp im
Tmax: Nhit cao nht
Tmin: Nhit thp nht
BPT: Biu ph ti
MLP: Mng nhiu lp truyn thng (Multi Layer Percepon)
LVQ: Mng lng t ha vc t (Learning Vector Quantization network)
L-M: Levenberg - Marquardt
viTrng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
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DANH MC CC HNH
S hnh Tn hnh Trang
2.1 Cu to N ron sinh hc 15
2.2 N ron n v x l 18
2.3 Hm tuyn tnh 19
2.4 Hm ngng 19
2.5 Hm ngng tuyn tnh 19
2.6 Hm dc 20
2.7 Hm sigmoid 20
2.8 Hm Sigmoid lng cc 20
2.9 a) Mng mt lp b) Mng nhiu lp 21
2.10 Mng truyn thng 22
2.11 Mng hi qui 22
2.12 M hnh hun luyn mng c gim st 23
2.13 M hnh hun luyn mng khng gim st 23
2.14 M hnh hun luyn mng tng cng 24
3.1 Biu ph ti c trng ngy h thng in Sc Trng 28
3.2 Biu ph ti ong hai nm 2004 n 2005 29
3.3 Biu ph ti t 3/1 n 9/1 nm 2005 30
3.4 nh hng nhit n thi quen tiu th in 31
3.5 th ph ti mt ngy thng v ngy quc khnh 32
3.6 th ph ti mt ngy thng v ngy tt dn tc 32
3.7 th ph ti mt ngy thng v ngy c l hi 33
3.8 th ph ti m c chung kt Euro v m bnh thng 34
3.9 th ph ti ngy bnh thng v ngy c ct in
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3.10 Biu ph ti in hnh ca mt ngy 3 5
3.11 Biu ph ti mt ngy sau khi qui chun 36
4.1 Qu trnh dch chuyn ca cc trng tm t v tr ngu nhin ban u
v cc vng s liu 43
4.2 S khi d bo hnh dng th ph ti 50
4.3 Giao din chng trnh d bo hnh dng th ph ti 51
5.1 th ph thuc ca Pmax vo Pmax-1 57
5.2 th ph thuc ca Pmax vo Pmax-7 57
5.3 th ph thuc caPm in vo Pmin-1 58
5.4 th ph thuc ca Pmin vo Pmin-7 58
5.5 th tng quan gia Pmax v cc Pmax trong qu kh 59
5.6 th tng quan gia Pmax v cc Pmin ong qu kh 60
5.7 th tng quan gia Pmin v cc Pmin ong qu kh 60
5.8 th tng quan gia Pmin v cc Pmax trong qu kh 61
5.9 Cu trc mng MLP vi mt lp n 63
6.1 Cu trc mng d bo ph ti cao im Pmax 76
6.2 Sai s phn trm khi thay i phn t lp n vi s ln tnh lp 200 79
6.3 Sai s phn trm khi thay i s ln tnh lp vi 22 phn t c nh 79
6.4 Qu trnh hun luyn mng vi 22 phn t lp n 50 ln lp 80
6.5 Sai s luyn mng gim sau mi chu k tnh lp vi thut ton L-M 81
6.6 Sai s phn trm khi thay i s phn t lp n vi s ln tnh lp 200 83
6.7 Sai s phn trm khi thay i s ln tnh lp vi 9 phn t c nh 83
6.8 Sai s phn trm Pmax khi thay i s phn t lp n vi s ln tnh lp 200 84
6.9 Sai s phn trm Pmin khi thay i s phn t lp n vi s ln tnh lp 200 85
6.10 Sai s phn trm Pmax khi thay i s phn t lp n vi s ln tnh lp 200 86
6.11 Sai s phn trm Pmin khi thay i s phn t lp n vi s ln tnh lp 200 87
6.12 Sai s phn trm tt nht trn 3 m hnh khc nhau 88
viiiTrng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
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6.13 BPT d bo v thc t ca Pmax v Pmin t 1 n 31/7 nm 2006 91
6.14 Biu ph ti thc t v d bo ngy 19-23 thng 6 100
6.15 BPT H i cc ngy lm vic thng 2/2004, 2005 100
6.16 Giao din d bo biu ph ti cho 24 gi sau 101
ixTrng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
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DANH MC CC BNG
S bng Tn bng Trang
4.1 Kt qu phn nhm th su thng 7 47
4.2 Kt qu phn nhm ngy th by thng 7 48
4.3 Kt qu phn nhm ch nht thng 7 49
4.4 Kt qu phn nhm th hai thng 7 49
4.5 Kt qu phn nhm cho c hai nm 2004, 2005 50
5.1 Kt qu phn tch tng quan gia Pmax v 20 yu t 51
5.2 Kt qu phn tch tng quan gia Pmin v 20 yu t 58
6.1 S liu hun luyn cho hai nm 2004 v 2005 77
6.2 S liu dng kim tra nm 2006 77
6.3 Kt qu d bo Pmax v Pmin t 1/7 n 31/7 89
6.4 Kt qu d bo Pmax v Pmin t 13/2 n 19/2 92
6.5 Kt qu d bo ph ti 24 gi, ngy 13/2/2006 91
6.6 Kt qu d bo ph ti 24 gi, ngy 14/2/2006 92
6.7 Kt qu d bo ph ti 24 gi, ngy 15/2/2006 93
6.8 Kt qu d bo ph ti 24 gi, ngy 16/2/2006 94
6.9 Kt qu d bo ph ti 24 gi, ngy 17/2/2006 95
6.10 Kt qu d bo ph ti 24 gi, ngy 18/2/2006 95
6.11 Kt qu d bo ph ti 24 gi, ngy 19/2/2006 96
X
Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
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M U
l Tnh cp thit ca ti
Trong nhng nm gn y, thc hin tin trnh cng nghip ha, hin i ha
t nc y nhanh s pht in ca nn kinh t, ng dng cc thnh tu khoa
hc cng ngh dn n nhu cu s dng in tng cao. Theo d bo ca Tng cng
ty in lc Vit Nam nhu cu ph ti in ong giai on 2006-2010 tng 16-
17%/nm. Tnh n ht 12/2006 in li Quc gia ph n 97,84% s x, 98%
s huyn v hn 93% s h dn c dng in. Vi tc pht trin ph ti n
th cng tc d bo ph ti l mt trong nhng ti quan tm ch yu trong lnh
vc pht in, truyn ti v phn phi in nng.
Bn cnh vic xy dng thm nhiu nh my, ng dy ti in, trm bin p
nhm p ng nhu cu ngy cng tng cao ca cc trung tm ph ti, dn n cc h
thng truyn ti phn phi hot ng khng m bo k thut, thiu ng b, c
bit vic nng cp h thng in khng da trn qui hoch tng th vn cn mang
tnh t pht, ty tin. Hu qu li hng lot vn cn khc phc nh: mt cn
i ngun v li in, gia cung v cu, tinh cy cung cp in, cht lng
in nng khng cao, tn tht cng sut, tn tht in nng trong h thng qu ln
[2] cc nguyn nhn l do hn ch v vn u t, nhng nguyn nhn quan trng
ch yu l lp k hoch vn hnh HT. Trong k hoch ha vn hnh HT nh
phn phi mt cch kinh t, hiu qu, ln k hoch bo dng v sa cha,... nhiu
hot ng thng c thc hin da trn vic d bo ph ti.
D bo ph ti c th c phn thnh: D bo di hn t 10 n 30 nm, d
bo trung hn t 3 n 10 nm v d bo ngn hn (gi, ngy, thng, ma nm). D
bo ngn hn ch yu phc v vic iu hnh sn xut, truyn ti v phn phi nng
lng phc v cho nhu cu trc tip ca sn xut v i sng, lp k hoch sn xut
v kinh doanh.
1Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
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Nu d bo ph ti in qu tha so vi nhu cu thc t th dn n vic phi
huy ng mt s lng ln ngun pht, nhng thc t khng dng ht cng sut ca
chng s gy lng ph. Nu kt qu d bo ph ti in qu thp so vi nhu cu thc
t s dn n tnh trng thiu ngun in, nh hng n pht trin ca nn kinh t
quc dn. Khi kt qu d bo tt s gip cho vic huy ng ngun tt v iu
cng tt c li ch v kinh t.
nc ta d bo ph ti ngn hn cng thu ht s quan tm nht nh trong
ngnh in, cc trng i hc v Vin nghin cu. Mt vi cng ty in lc, c
quan iu quc gia bt u xy dng chng trnh d bo ph ti in. Ngoi
mt s nghin cu ng dng m hnh hi quy. C th thy rng nhu cu d bo ph
ti ngn hn cc cng ty in lc ch c thc hin bng phng php chuyn
gia da trn kinh nghim ca cc k s iu . Nn mang tnh ri ro v chnh
xc khng cao. Mc khc, d bo ph ti trc y ch tp trung d bo cho cc
thnh ph ln nh H Ni hay TP H Ch Minh cn cc tnh vng nng nghip,
nng thn m c bit l tinh Sc Trng cha c chng trnh d bo ph ti, hot
ng d bo da vo kinh nghim v iu hnh trc tip. Vic p dng mng n
ron nhn to cho d bo ph ti in cho mt tinh thun nng nghip nh Sc
Trng da n yu cu n gin, c tnh n nh hng ca nhit v c th
ngy, cho kt qu d bo vi sai s chp nhn c l hng ca nghin cu ny.
2 Kh nng ng dng mng n ron nhn to trong bi ton d bo
Bi ton d bo ph ti c pht in t rt lu vi rt nhiu m hnh
c xut. u thp nin 90 m hnh d bo bng cng ngh mng n ron bt
u c nghin cu v pht trin v cng c mng n ron c th p dng trong cc
d bo di hn, trung hn v c ong d bo ph ti ngn hn, cho kt qu kh
chnh xc. M hnh mng n-ron d bo ph ti ang c ng dng nhiu nc
c th trng in pht trin nh M, c, Anh, Php... Cc m hnh mng thng
c cu trc tng th ging nhau. Hin nay khng ch Vit Nam m ngay c cc
cng ty in lc v th trng in n th gii vn tip tc tm kim cc thut ton
mi phc v cng tc d bo t mc chnh xc v nhanh chng hn. Tuy nhin i
2Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
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vi tng h thng vi nhng c trng ring ta khng th s dng cc m hnh vi
cc thng s ca h thng khc m vn cn phi xc nh cc cu trc v thng s
ti u cho h thng ca ring mnh.
Vit Nam bi ton d bo ph ti ngn hn c gii quyt bng nhiu
phng php khc nhau nh: Phng php ngoi suy, phng php san bng hm
m, phng php hi qui a bin,... c xut ong d bo ph ti ngn hn.
C th nhn thy rng nhc im ca cc phng php trn l m hnh d bo
lng in nng tiu th ch hiu qu i vi mt s ngy bnh thng nhng li
khng hiu qu i vi tt c cc ngy. Vi nhc im n thc cc
chuyn gia vn hnh pht trin phng php chuyn gia: phng php da n mt
s qui tc (lut) ca cc chuyn gia v chuyn ngnh d bo, nn mang tnh kinh
nghim, nh hng, ph thuc vo nh ca c nhn chuyn gia. Thng cc
quy lut ny c m t bi quan h hm n gin nn khng th hin cc
mi lin h phc tp gia cc thng tin h thng in.
Cc phng php trn v ang c s dng nhng vn cn mt s hn ch
nh: Ph ti l mt i lng ph thuc (phi tuyn) vo rt nhiu yu t, c th k
ti s ph thuc ca lng in tiu th vo cc thng s thi tit nh nhit ,
Nn s gi chiu sng, cc s ph thuc ny c quan h rt mt thit nhng ht sc
phc tp, kh xc nh cc qui lut hm chnh xc. Hin nay, vic pht trin ca
my tnh cho php ta s dng cc m hnh phc tp m vn m bo thi gian tnh
ton ph hp.
Mt khc, h thng in l mt ong nhng h thng c tnh phi tuyn cao.
Phn tch, gim st v iu khin HT lm vic vi hng trm bin trung gian
khng phi lc no cng o lng c. Trong khi , mng n ron nhn to c
thit k tm hm quan h trc tip gia cc bin u vo v u ra, khng cn
phi tm cc mi lin h gia cc bin trung gian. Mng n ron l phng tin c
kh nng hc t cc s liu qu kh v tm ra cc mi quan h ph thuc phc tp
3Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
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gia cc bin thm ch khi khng xy dng c m hnh ton hc ca bi ton.
Mng n-ron c th lm vic vi cc d liu khng y hoc d liu b nhiu.
khc phc cc hn ch trong x l cc hm quan h phi tuyn, lun vn s
s dng cng ngh tr tu nhn to m mng n ron l mt i din ng dng
ong d bo ph ti Vit Nam. Cc nghin cu hin nay v lnh vc ny vn cn
giai on bt u pht trin. Cc nghin cu v ng dng cc cng c d bo
ong v ngoi nc vn ang c thc hin, nhng nhu cu thc t vn cha c
p ng y .
3. i tng, mc tiu v nhim v nghin cu
i tng nghin cu ca lun vn l d bo ph ti ngn hn da trn cc
biu ph ti ong qu kh, cc c im, tnh cht ca biu ph ti, cc thng
s kh tng. M hnh d bo mng n ron.
Mc tiu ca lun vn l nghin cu, xy dng m hnh d bo ph ti in c
chnh xc cao. M hnh s s dng mng n ron ong tnh ton, s c chng
trnh m phng vi giao din thun tin cho ngi s dng. t c mc tiu
n ti cn thc hin nhng nhim v sau:
1) Nghin cu v cc phng php d bo v ang c s dng trong bi
ton d bo ph ti in ngn hn, c xem xt cc u nhc im tng
phng php.
2) T xut gii php s dng MNR theo m hnh hai bc:
Bc 1: Phn nhm cc biu ph ti (BPT) trong qu kh d bo
hnh dng BPT da trn tng mng t t chc Kohonen (Self-
Organization Map) vi thut ton tm trng tm c p dng l Fuzzy
Clustering Method (FCM). Thut ton s xp cc BPT ong qu kh ca cc
ngy theo th trong thng tng i ging nhau vo mt nhm nh (th by,
ch nht, th hai - th su.. .)
4Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
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Bc 2: T BPT d bo, dng mng n ron nhiu lp Multi-layer
percepon (MLP) vi thut ton Levenberg-Marquardt c s dng xy
dng m hnh d bo cng sut cc i v cng sut cc tiu. Cc b thng s
u vo l cc cng sut cc i, cc cng sut cc tiu trong qu kh v
thng s thi tit (c th l nhit ). Vic tnh ton c thc hin n my
tnh vi phn mm Matlab.
3) Lp trnh tnh ton, m phng xc nh cc thng s ti u cho m hnh,
chnh xc ca kt qu d bo.
4) Nghin cu cc hng pht trin lun vn
ngha khoa hc: ng dng mt phng php mi phc v cng tc d bo
ph ti. Rt ngn thi gian d bo ph ti.
ngha thc tin lun vn: Xy dng phng php d bo ph ti mi cho
mt tnh thun nng nghip nh Sc Trng, l ti liu tham kho cho nhn vin iu
hnh h thng in.
Trong khun kh lun vn ny, ch nghin cu phng php d bo ph ti ngn
hn. i tng c th ca nghin cu l d bo ph ti cho 24 gi sau, nhm a ra
cc thng s ph ti ca ngy hm sau phc v cng tc vn hnh v iu HT.
Vic xy dng v kim tra m hnh d bo da trn s liu ph ti thc do in lc
Sc Trng cung cp, cng vi b s liu nhit cao nht, thp nht trong ngy do
Trung tm d bo kh tng thy vn tnh Sc Trng thu thp.
Gm nhng ni dung chnh sau:
Phn m u trnh by tm tt cc vn , ang v s gii quyt trong lun
vn, d kin cc gii php s dng, d kin cc kt qu ca lun vn.
Chng 1 trnh by c th nhu cu thc tin v m hnh d bo ph ti in v
cc phng php ang c ng dng trong v ngoi nc, kho st cc phng
php d bo in hnh ang c ng dng v nhu cu xy dng phng php mi.
5Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
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Chng 2 trnh by nhng nghin cu c bn v mng n ron nhn to: Qu
trnh hnh thnh pht in, mt s khi nim c bn, cu trc, cc loi mng v kh
nng ng dng ca mng n ron nhn to
Chng 3 tm hiu cc c im biu ph ti tinh Sc Trng bao gm cc
nguyn nhn nh hng n biu ph ti in nh thi quen sinh hot, thi v,
cc ngy l tt v nh hng ca thi tit n BPT in.
Trong chng 4 l phn ng dng tng mng Kohonen trong vic phn
nhm cc loi kiu ngy: Trnh by tng c bn mng Kohonen xut thut
ton FCM gii bi ton Kohonen, phn loi BPT v chng nh d bo hnh
dng th ph ti cho mt ngy.
Chng 5 i v phn xc nh cc thng s u vo cho mng MLP bng vic
xt mi tng quan gia cc yu t, k thut lan truyn ngc v thut ton
Levenberg - Marquardt.
Chng 6 l phn in khai m hnh thc t mng n ron ong d bo ph ti
ngn hn. Trn c s cc u vo xc nh kt hp vi yu t thi tit s xy
dng cc m hnh d bo khc nhau, mi m hnh c nh gi sai s, la chn
m hnh d bo cho sai s thp nht. Xy dng giao din d bo cho 24 gi trong
ngy.
Tip sau chng 6 l phn kt lun chung ca lun vn.
Cui cng l ti liu tham kho.
6Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
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NHU CU THC TIN V D BO PH TI IN V MT S
PHNG PHP D BO HIN C
l l Nhu cu thc tin v d bo ph ti in:
in nng l mt sn phm c bit quan trng i vi s pht trin kinh t,
x hi, i sng dn sinh v chnh i vi bt c quc gia no trn th gii.
Khng ging nh cc sn phm khc trong nn kinh t th trng vi mc tiu l li
nhun, khi khng c li nhun th ngng sn xut, in l mt sn phm c bit
khng th thiu c, nn ngnh in c xem l mt mt ngnh thuc c s h
tng. in nng khc vi cc sn phm hng ha nh n c kh nng p ng
nhanh chng nhng bin i ca nhu cu ti mi thi im v tnh hu nh khng
th d tr c. Do , vn d bo ph ti mt cch chnh xc cng nh ton b
cc khu sn xut, truyn ti, phn phi, phi lun tnh trng sn sng p ng
nhu cu ph ti l yu t c bn nh hng n hiu qu phc v khch hng ca h
thng.
Hin nay, vi s ra i ca Lut in lc, sc p v nng cao hiu qu kinh t
trong sn xut, truyn ti v phn phi i vi ngnh in ngy cng tng. c bit
trong thi gian ti, khi th trng in ra i v in nng tr thnh mt mt hng
mua v bn theo gi c th trng, d bo ph ti ong iu kin s ng vai
tr quan trng hng u trong vic hnh thnh gi in v v vy n thnh mt
vn sng cn ca ngnh in.
Trong cng tc vn hnh, lp phng thc vn hnh ngy v phng thc vn
hnh tun ca ngi lm cng tc iu , d bo ph ti ngn hn bao gm: d
bo trc mt gi, mt ngy hoc mt tun, ng mt vai tr v cng quan ng.
Nhng phng thc vn hnh c bn trong ngy nh huy ng ngun, phi hp
thy in v nhit in, truyn ti cng sut gia cc min, gii quyt cc cng tc
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sa cha n li in v nh gi an ton HT u i hi phi c d bo ph
ti chnh xc.
Chng ta bit rng nhu cu tiu dng in nng ph thuc vo trinh pht
trin ca nn kinh t quc dn, v th d bo ph ti in l mt b phn ca d bo
pht trin kinh t. Nu chng ta d bo cao hn thc t s lm chi ph tng mnh, do
phi huy ng khng cn thit cc ngun in d phng t tin nh diesel, cc
my pht chy du DO.. .Ngc li nu d bo thp hn thc t s dn n kt qu
ngun d phng thp, gim an ton cung cp in, c th phi ct in do vic
huy ng thiu ngun, khng nhng gy thit hi v kinh t, an ninh x hi, i
sng sinh hot nhn dn m cn m cn lm gim uy tn phc v khch hng.
Theo EVN, nm 2006 c cu tiu th in Vit nam c nhiu chuyn bin,
thnh phn ph ti sinh hot gim t 43,3%, cng nghip tng t 47,43%, tuy
nhin s chnh lch ph ti cao im (ph ti cao nht trong ngy Pmax l khong
7000MW) v thp im (ph ti thp nht ong ngy Pmax l khong 4500 MW)
c t s p max/ p min khong 1,6 y l mt s chnh lch ln. Pmax v Pmin
cng chnh l hai gi tr ph ti c bit trong th ph ti ngy v c ngi lm
cng tc iu quan tm nhiu nht trong qu trnh vn hnh, v mt vn hnh vi th ph ti bin ng ln, thnh phn thay i, qu trnh khi ng my pht
din ra thng xuyn nh hng n tui th v ch tiu kinh t k thut ca nh
my, tn tht cng sut v in nng cng s gy nhiu bt li. Ph ti cao im l
nhn t quyt nh vic huy ng cc ngun nhit in, tua bin kh, iesel d phng
nhm m bo ngun ph nh v d phng nng, tng an ton cung cp
in. Ph ti thp im quyt nh vic phi hp v iu chnh cc ngun tua bin
kh, nhit in, thy in m bo vn hnh kinh t. Trong d bo ph ti lc
cao im Pmax l khu quan trng nht.
Trong thi gian ti khi HT Vit Nam c u ni vi cc HT ca Trung
Quc, Lo v cc nc trong khu vc, th vn tng tin cy cung cp in, vn
hnh kinh t v an ton HT cng tr nn bc thit. Do , gii quyt tt vn
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cung cp in c vai tr v ngha v cng to ln. V vy, vic nghin cu v p
dng m hnh d bo khc nhau nhm tm ra m hnh d bo ti u cho vn d
bo ph ti l ti nghin cu khoa hc rt cn thit i vi cc trung tm iu
trong vn hnh ti u HT ca mnh.
l 2 Cc phng php d bo ang c nghin cu v ng dng
l 2l Phn loi cc phng php d bo ph ti in ngn hn [5]
D bo lun gi vai quan trng trong nhiu lnh vc, quyt nh k hoch
sn xut, hng u t pht in trong tng lai, do c rt nhiu cc m hnh
ton hc p dng cho d bo. Phng php thng c dng nht l phng php
tip cn v m i vi bi ton d bo v c gng lp m hnh ca ph ti ong
tng lai sao cho n phn nh hnh vi v tnh cht ca n trong qu kh.
C nhiu cch phn loi phng php d bo ph ti in ngn hn ta c th
ly v d mt s phn loi nh sau:
> Phn loi theo tnh ng. Chia lm hai loi c bn: Phng php m hnh thi
gian trong ngy v phng php m hnh ng.
Trong m hnh thi gian trong ngy, ph ti c biu din mt ln di dng
chui thi gian ri rc (discrete) cha cc gi tr d bo cho tng gi cho c giai
on d bo. Thng thng ph ti c m hnh ha di dng tng ca mt biu
ph ti tiu chuNi (Standard Load Curve - SLC) v phn d.
Cc m hnh ng th cho rng khng ch l hm ca thi gian trong ngy m
cn ph thuc vo hnh vi trong qu kh ca ph ti - cc gi tr ph ti ca cc gi
trc .
> Phn loi theo m hnh xc nh/bt nh (deterministic/stochastic)
Cc m hnh xc nh ch cung cp cc gi tr ph ti d bo m khng nh
gi sai s d bo. Trong khi , m hnh bt nh a ra gi ph ti d bo nh
gi tr k vng ca mt qu nh bt nh, ngu nhin. M hnh bt nh cho php
tnh cc c tnh thng k ca gi tr ph ti d bo, trong c sai s d bo.
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> Phn loi theo m hnh ph ti tng/ph ti theo thnh phn tiu th
Thng d bo ph ti ngn hn s dng m hnh ph ti tng. Mt s cng
trnh nghin cu cng chia ph ti thnh cc thnh phn tiu th khc nhau, tin
hnh d bo cho tng thnh phn tiu th, sau gp ph ti d bo ca tt c cc
thnh phn li thnh ph ti tng d bo. Phng php ny i hi s lng ln
cng vic cn xy dng m hnh hp l cho tng thnh phn tiu th.
1.2.2 Mt s phng php d bo in hnh:
a) Phng php hi qui tuyn tnh:
Hi qui tuyn tnh l m hnh ton hc xc sut v thng k, phn tch mi
tng quan gia hai hay nhiu bin. M hnh hi qui tuyn tnh c xy dng trn
c s gi thuyt quan h gia hai bin ngu nhin l tuyn tnh, sau xc nh
phng trnh ng thng biu din quan h v phng trnh ng thng ny
d bo bin m ta cn tm. M hnh hi qui tuyn tnh l m hnh kinh in, n
gin v kh hiu qu trong thng k v d bo, do c rt nhiu d bo da trn
phng php ny.
Phng php hi qui da trn vic phn tch bn cht hin tng hay s vic
cn nghin cu tm ra qui lut, d on c xu th bin ng ca hin tng, s
vic trong tng lai, l phn tch mi quan h ph thuc gia cc i lng
ngu nhin lin quan n hin tng, s vic cn nghin cu.
Theo nghin cu ca [1] phng php hi qui c ng dng trong d bo
ph ti Pmax v Pmzn ong ngy c xt n yu t nhit cho kt qu sai s trung
bnh l 4%. Phng php ny cho kt qu kh tt khi quan h gia cc bin ngu
nhin l tuyn tnh v ngc li.
b) Phng php chuyn gia:
Phng php chuyn gia d bo c kt qu l cc thng s do cc chuyn
gia a ra, da n trnh uyn bc v l lun, thnh tho v chuyn mn, phong
ph v kh nng thc tin cng vi kh nng mn cm, nhy bn v thin hng
su sc v tng lai (i vi i tng d bo) ca mt tp th cc nh khoa hc,
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cc nh qun l cng i ng cc nh cn b lo luyn thuc cc chuyn mn hay
nm ong min ln cn ca i tng d bo a ra cc d bo.
Phng php chuyn gia c u th hn hn khi d bo nhng hin tng hay
qu trnh c tm bao qut rng, cu trc ni chung phc tp nhiu ch tiu, nhiu
nhn t chi phi lm cho xu hng vn ng cng nh hnh thc biu din a dng,
kh nh lng bng con ng tip cn trc tip tnh ton, o c thng qua cc
phng php c lng v cng c chnh xc.
y l phng php tng i n gin, d p dng v c kh nng tm ra tc
thi cc thng s, m cc thng s ny khng d dng lng ha c v m t quy
lut vn ng di dng hm s.
Phng php chuyn gia thch ng c vi c im v yu cu ca mt d
bo nhu cu v tnh hnh hin ti l tnh kh thi cao, cho kt qu nhanh, to ngay
cn c ra cc quyt nh, ng x tc thi, ph hp vi din bin si ng v
trng thi mun v ca i tng. Mc khc, phng php ny cho php d bo
c nhng hin tng t bin ca i tng m thc t xy ra, nu s dng
cc phng php d bo khc rt kh v rt lu a ra kt qu v tin cy cng
khng cao.
Khng phi bt c trng hp no, bt c lc no cng i hi kt qu d bo
phi th hin di dng cc thng s xc nh, m nhiu khi kt qu d bo cng c
th tn ti di dng nhng nhn nh mang tnh cht nh tnh, nhng xu hng,
chiu hng vn ng. Phng php chuyn gia cng rt hu hiu i vi d bo
nng v cht hn lng. Tuy nhin phng php ny c nhc im l thng
mang tnh ch quan nu chn chuyn gia khng ng tiu chuNi th tin cy d
bo thp. Khi kin chuyn gia tn mn tri ngc nhau th qu trnh x l kin
chuyn gia s kh phc tp. Nhiu chuyn gia a ra s liu d bo, nhng c s l
gii li khng r rng, bin giao ng ln, kin cho vic nh gi sai s v
khong tin cy gp kh khn. Vic tp trung cc chuyn gia y ong mt cuc
hp, vic thu hi phiu tr li ng thi hn cng khng c d dng.
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c) M hnh thi gian trong ngy (time of day)
dng n gin nht, m hnh thi gian trong trong ngy ly mu ph ti thc
t tun trc lm m hnh d bo ph ti tun sau. Ngi ta c th s dng mt
cch khc l chn ly mt tp mu ph ti ca mt s tun c trng cho cc iu
kin thi tit khc nhau.
Mt m hnh thi gian trong ngy khc l phng php tch ph. Khc bit
gia phng php tch ph vi m hnh trn l hm thi gian. Theo [5] phng
php tch ph cho kt qu c chnh xc cao hn so vi cc hm thi gian.
d) Cc m hnh chui thi gian ngu nhin (bt nh)
Nguyn tc c bn ca phng php ny l u tin chui ph ti theo thi
gian c chuyn thnh chui thi gian dng (Stationary Time Series - tc chui
khng bin i theo thi gian), sau chui dng cn li s c lc nhiu trng.
M hnh ARIMA khng ph hp m t chui ph ti v chui ph ti c cha
yu t ma. V vy, tnh n yu t ma v c bin s nhit thng c gi
l SARIMAX.
Cc m hnh chui thi gian c nhiu u im. Trc ht, l thuyt m hnh
chui thi gian c c s ton hc cht ch v r rng nn d thc hin d bo n
c s l thuyt ny. Cc thng s ca m hnh cng c tnh ton mt cch d
dng. Th tc nh gi thng s m hnh cng khng kh.
Tuy nhin, m hnh chui thi gian c mt s im yu rt ln l tnh kh
thch nghi. V d nh khi ph ti in hay i rt nhanh mt s thi k nht nh
trong nm. Trong m hnh ARIMA, ph ti d bo cho mt gi no v nguyn
tc li l hm ca tt c cc gi tr ti trc , v vy m hnh khng th thch nghi
nhanh vi iu kin mi. gii quyt vn ny, tc tng tnh thch nghi ca m
hnh, ngi ta thng s dng h s qun a vo cc ng s ln hom cho cc
hnh vi gn nht ca ph ti.
Mt nhc im na ca m hnh chui thi gian l x l cc ph ti bt
thng. Nu hnh vi ca ph ti l bt thng trong mt ngy no th s sai lch
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ny s c phn nh ong chui ph ti d bo trong tng lai. V vy, gii
quyt vn ny, ngi ta ngi ta thng thay cc gi tr ph ti bt thng ong
chui ph ti qu kh bng gi tr d bo tng ng, tc gi khng bt thng
gi s ca ngy hm .
1.3 Ctf s xy dng phng php d bo ph ti mi s dng mng ntf ron
nhn to
D bo ph ti in ngn hn ong nhng nm gn y c quan tm nghin
cu bi v cc nguyn nhn sau y:
- S dch chuyn th trng in lc Vit Nam t c quyn ngnh in sang
mi trng cnh tranh cao hn trong th trng in, do i hi cc bi
ton d bo phi t c chnh xc cao;
- Khoa hc k thut ngy cng pht trin to nn tng cho mt s l thuyt
d bo mi pht in;
- S pht in ca cng ngh thng tin m ra cc kh nng trin khai cc m
hnh l thuyt cc h thng tnh ton trong thi gian thc.
Mng n ron nhn to c xy dng da n c s m phng hot ng ca
h thng n ron thn kinh sinh hc, do mng n ron nhn to c mt s c im
quan trng ging b no con ngi: l kh nng hc c nhng g c
dy. Qu trnh hc ny c a vo mng theo nhng mu cho trc. Trong qu
trnh ny cc mu th hin quan h gia cc bin c a vo trong mng n ron,
mng s nhn bit c cc quan h sau khi kt thc qu trnh hun luyn. Chnh
do c im ny m mng n ron c ng dng mnh trong lnh vc d bo. Hin
nay m hnh ny cng ang c p dng ph bin mt s nc pht in ong
d bo ph ti. Cc nghin cu ng dng mng n ron ong d bo ph ti cng
bt u thc hin cc trng, vin nghin cu. Tuy nhin, s lng nghin cu t
i cha c s xy dng mt phng php lun c bn ph hp cho cng tc
d bo ph ti ngn hn nc ta.
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CHNG 2
GII THIU V MNG N RON NHN TO
2l Tr tu nhn to
Con ngi t nhng ngy u hnh thnh thi k c i vi nhng con s
m nguyn dng c bn. Cho n tn thi im khong gia th k 20, khoa hc
vn ch mi dng li hnh thc cht ch, l gc, ong khi nhng vn thc t
do con ngi c th cm nhn c th ngy li cng phc tp. Chnh v vy, nhng
t tng v cch gii quyt vn hin thc bng hnh thc pht trin cao hn l
khoa hc tu nhn to c hnh thnh trong giai on t cui th k 20 n
nay ong giai on tin hc ang dn pht trin.
Tr tu nhn to c kh nng gii quyt vn bng cch bt chc li suy
ngh ca con ngi iu ny c thc hin da trn cc cng c hin i ngy nay
l cc phn cng x l cao, vi mi trng v kh nng tnh ton ph hp. C th
c ng dng thit k, ch to b no cho cc thit b iu khin thng minh.
Vi tn hiu u vo l nhng tham s qu trnh ca i tng cn iu khin, kt
hp vi nhng tc ng bn ngoi, loi thit b ny s a ra c nhng tn hiu
u ra thng minh, iu chinh thch hp nhng tham s ny a i tng lun
lm vic nh mong mun. Do , tr tu nhn to c bit hiu qu gii cc bi
ton nhiu bin a mc tiu c rng buc, ong khi khoa hc c bn cha th
hoc kh khn trong qu trnh tm li gii ng. Cc cng ngh tu nhn to
thng dng c th k ti l:
MngNron;
L thuyt l-gc m;
Gii thut di truyn.
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2.2 N ron sinh hc
T hng ngn nm trc y con ngi dy cng nghin cu phng cch
lm cho b no c kh nng t duy. Tuy vy, phi ti th k th 18-19 ngi ta mi
xc nhn c rng b no thc s ng vai tr quan ng bc nht trong nhn
thc v khng nh rng hot ng nhn thc ca con ngi cn gn lin vi hot
ng ca cc b phn c th khc.
B no ca con ngi c khong 15 t n ron thn knh l oa v c s m
nhim nhng chc nng x l nht nh trong h thn kinh bao gm no, tu sng
v cc dy thn kinh. Mi n ron c phn thn vi nhn bn trong, mt u thn
knh ra (gi l si trc axon) v mt h thng dng cy cc dy thn kinh vo (gi l
dendrite). Cc dy thn kinh vo to thnh mt li dy c xung quanh thn t
bo, chim din tch khong 0,25 mm2, cn dy thn kinh ra to thnh trc di c
th t lcm cho n hng mt. ng knh ca nhn t bo thng ch l 1(T* m.
Trc dy thn kinh ra cng c th phn nhnh theo dng cy ni vi cc dy thn
kinh vo hoc trc tip vi nhn t bo cc n ron khc thng qua cc khp n thn
kinh (gi l synapse). Thng thng, mi n ron c th gm vi chc cho ti hng
trm ngn khp ni ni vi cc n ron khc. Ngi t c lng rng li cc
dy thn kinh ra cng vi cc khp ni bao ph din tch khong 90% b mt n
ron (Hnh 2.1).
T hn t bna
Hnh 2.1: cu to n-ron snh hc
Cc tn hiu truyn trong cc dy thn kinh vo v dy thn kinh ra ca cc n
ron l ta hiu in p v c thc hin thng qua cc qu trnh phn ng v gii
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phng cc cht hu c. Cc cht ny c pht ra t cc khp ni dn ti cc dy
thn kinh vo s lm tng hay gim in th ca nhn t bo. Khi in th ny t
ti mt ngng no s to ra mt xung in dn ti trc dy thn kinh ra. Xung
ny c truyn theo trc, ti cc nhnh r khi chm ti cc khp ni vi cc n
ron khc s gii phng cc cht truyn in.
C th ni rng h thng thn kinh con ngi c tnh mm do do cho php
n c th pht trin thch nghi vi mi trng xung quanh. Tnh mm do c
th hin bi hai hot ng: s to ra cc khp ni thn kinh (synapse) mi gia cc
n ron v s bin i cc khp ni thn kinh hin c. Mi n ron c th nhn hng
vn tn hiu v cng c th gi hng vn tn hiu i. Cc n ron lin kt vi nhau
to thnh mng. Mt iu c bit l cc n ron rt n gin trong c ch lm vic,
nhng MNR lin kt vi nhau li c kh nng tnh ton, suy ngh, iu khin v lu
tr thng tin.
2.3 Mng ntf ron nhn to
2.3.1 Lch s hnh thnh v pht trin
Mt s cng trnh nghin cu c s cho lnh vc mng n ron c cng b
vo cui th k 19, u th k 20. Cc cng trnh ny tng hp v vt l, sinh l v
vt l hc n ron do cc nh khoa hc: Hermann von Helmholtz, Emst Mach v
Ivan Palov thc hin. Cng trnh u tin ny nhn mnh vo l thuyt hc tp, tm
nhn v hun luyn v.v... m khng c cc m hnh ton c th ca hot ng n
ron.
Nm 1943, khoa hc tr tu nhn to t ct mc hnh thnh vi s pht in
mng n ron u tin do Warren McCulloch v Walter Pitts a ra. K t ,
tng v vic xy dng mt h thng x l hin thc vi tn gi mng n-ron nhn
to {Artificial Neural Network) ra i; bi n c cu trc gn ging vi cu trc b
no con ngi v cch hc tp, lm vic ging nh con ngi.
Nhng nm 50 v 60 l thi k hng thnh ca mng n ron vi cc cng trnh
ca Rosenblan (1960) v mng Perceptron. Nm 1959, Bernard Widrow v Marcian
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Hoff pht trin mng ADALINE v bi bo bnh gii ca Minsky v Papert v
mng percetron.
Nhng nm 70 MNR ri vo trng thi im lng c v nghin cu v ng dng.
Tuy vy c th k n cc nghin cu v qu trnh hc ca mng nhiu lp, mng t
t chc ca Kohonen, mng kiu b nh kt hp (BAM) ca Anderson, mng
ART1 (Adaptive Resonace Theory NN ) ca Capenter.
Nhng nm 80 l thi k phc hng ca cc nghin cu v ng dng mnh
m ca cc MNR vi nghin cu v thut gii hc da n lan truyn ngc sai s
luyn cc mng nhiu lp c mt vi nh nghin cu c lp tm ra nh:
David Rumelhart, James McCelland... Ngoi ra cn c mt s mng khc nh
mng mt lp ca Hopfield, mng theo kiu my Boltzmann v mng Neoconitron
ca Fukushima.
T u nhng nm 90 n nay vic nghin cu MNR nhn to c nhng
thnh cng to ln v ng dng nhiu lnh vc khc nhau. Ngoi ra MNR cn c
kt hp vi cc k thut khc ca tr tu nhn to: gii thut duy truyn, logic m,
h chuyn gia phn tch d liu v thu thp tri thc phc v cho vic xy dng
cc h thng thng minh lai.
2.32 M hnh mng Ntf ron nhn to
m phng cc t bo thn kinh v cc khp ni thn kinh ca b no
con ngi, trong mng n ron nhn to cng c cc thnh phn c vai tr tng
t l cc n ron nhn to cng cc khp ni.
Mt n ron nhn to l mt n v tnh ton hay n v x l thng tin c
s cho hot ng ca mt MNR. S khi ca hnh 2.2 ch ra m hnh ca
mt n ron nhn to. Quan h gia cc n ron c th hin bng ng ni c
trng s gia chng. y, chng ta xc nh ba thnh phn c bn ca mt
m hnh n ron:
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Hnh 2.2: N-ron n v x l
Mt tp hp cc cc khp ni, m mi mt trong chng c c trng
bi mt trng s ca ring n. Tc l mt tn hiu Xn ti u vo ca khp ni
s c nhn vi trng s w n. Cc trng s w c th nhn c cc gi tr m v
cc gi tr dng.
Mt b cng tnh tng trng h cc tn hiu u vo ca n ron,
c nhn vi cc trng s tng ng, ri cng kt qu ny vi trng ngng
0, trng ny c lu trong b nh, theo [3] trng ngng c vai tr lm tng
tnh thch nghi v kh nng tnh ton c mng n ron. Php ton c m t
y to nn mt b t hp tuyn tnh.
Mt hm kch hot / (u) gii hn bin u ra ca n ron. Hm kch
hot cng c xem xt nh mt hm nn; n nn (gii hn) phm vi bin
cho php ca tn hiu u ra trong mt khong gi tr hu hn.
Di dng cng thc ton hc, chng ta c th m t mt n ron k bng
cp cng thc sau:
nu = + wx -
=1 *
V y = /( )
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Ging nh con ngi khi cha tip cn tri thc chuyn mn, MNR nhn
to khi mi hnh thnh cu trc cha c tri thc, c ngha l cc trng s ghp
ni cn c cc gi tr ngu nhin v u ra tn hiu ca n ron cng c gi tr
ngu nhin.
2.33 Cc hm kch hot:
Hm tuyn tnh (Linear funtion) fill)
y = f (u ) = au
Vi a l dc ca hm tuyn tnh, khi dc
a = 1 th hm tuyn tnh c gi l hm ng nht -
hm lp.
Hnh 2.3: Hm tuyn tnh
Hm ngng {Binary step function, Hard limiter
funtion).
u ra hm ny c gii hn vo mt trong
hai gi tr:
U
u
Hnh 2.4: Hm ngng
Hm ngng i xng (Symmetrical Hard limiter
funtion)+1
-1
Hnh 2.5: Hm ngng tuyn tnh
19
Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
-
Hm dc {Ramp function)
( 1 nu u < - 1y = f { u ) = j u n t - 1 > 1
( 1 nu u 1
Hm Sigmoid (Sigmoid function)
y = / ( ) = ~ rl + e_ *
Hm ny c bit iun li khi s
dng cho cc mng c hun luyn bi
thut ton lan truyn ngc (back-
propagation), bi v n d ly o hm, do
c th gim ng k tnh ton trong qu
trnh hun luyn. Hm ny c ng dng
cho cc chng trnh ng dng m cc u
ra mong mun rod vo khong [0,1].
Hm Sigmoid lng cc (Bsigmoid
function(tansig))
\ - e ~ xy = m = ^
l + e ~ x
Hm ny c cc thuc tnh tng t
hm sigmoid. N lm vic tt i vi cc
ng dng c u ra yu cu trong khong [-
1, 1].
Hnh 2.6: Hm dc
Hnh 2.8: Hm Sigmoid lng cc
i vi cc om v u ra, cc hm kch hot cn c chn sao cho ph hp
20
Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
-
vi s phn phi ca cc gi tr ch mong mun. Chng ta thy rng i vi cc
gi tr ra ong khong [0,1], hm sigmoid l c ch; i vi cc gi tr ch mong
mun l lin tc trong khong th hm ny cng vn c ch, n c th cho ta cc
gi tr ra hay gi tr ch c cn ong mt khong ca hm kch hot u ra.
Nhng nu cc gi tr ch khng c bit trc khong xc nh th hm hay
c s dng nht l hm ng nht (identity function). Nu gi tr mong mun l
dng nhng khng bit cn trn th nn s dng mt hm kch hot dng m
{exponential output activation function).
2.3.4 Phn loi cc mng Ntf ron:
a) Theo s lp ngi ta chia lm hai loi:
Trong hnh 2.9 (a) Mng mt lp (Perceptron) l mng ch c mt lp vo cng
l lp n v lp ra. Hnh (b), mng gm ba lp hay cn gi l mng (Multi layer
Perceptron). Lp nhp (input), lp n, v lp xut (output). Mi nt trong lp nhn
nhn gi tr ca mt bin c lp v chuyn vo mng. D liu t tt c cc nt
trong lp nhp c tch hp - ta gi l tng ng ha - v chuyn kt qu cho cc
nt trong lp n.
Tng vo Tng ra lang vo rngn rng ra(input) (ouput) (input) (hide) auput)
Hnh 2.9 a) Mng mt lp b) Mng nhiu lp
Gi l n, v cc nt ong lp ny ch lin lc vi cc nt trong cc lp nhp
xut, tng t nt trong lp xut cng nhn cc tn hiu tng trng ha t cc nt
n. Mi nt ong lp xut tng ng mt bin ph thuc. Phn ln cc bi ton ch
c mt bin ph thuc, nhng vi m hnh nh trn, M R cho php s bin ty .
21
Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
-
Th d, nu mng cn nhn dng cc ch s tn ta c th xy dng mt mng vi 10
nt xut; hoc d bo ph ti chi cn mt nt xut cho c chui gi cn d bo
b) Theo kiu lin kt c th phn thnh:
Mng truyn thng: Cc lin kt n ron i theo mt hng nht nh, khng
to thnh chu trnh vi cc nh l cc n ron
Mng hi qui: Cho php cc n ron to thnh chu trnh, trong mt hoc
nhiu u ra ca phn t lp sau truyn ngc ti u vo ca lp trc.
Hnh 2.10 Mng truyn thng Hnh 2.11 Mng hi qui
Mng t t chc: Xy dng da trn pto ging b no ngi, cc n ron
c phn b trong lp sao cho c mi lin h v khng gian, gha l tn hiu vo
tng t nhau s kch hot cc n ron gn nhau ong khng gian
2.4 Hun luyn mng Nor ron:
Mng n ron khi mi hnh thnh cha c tri thc, tr thc ca mng hnh thnh
dn sau mi ln hun luyn (hc). M R c dy bng cch a vo u vo
nhng kch thch v mng hnh thnh nhng p ng tng ng, nhng p ng
ph hp vi tng loi kch thch s c lu gi Cc k thut hc nhm vo vic
hiu chnh cc trng s v vic iu chnh, sa i cu trc ca mng nh s lp, s
n ron, kiu v cch m cc lp lin kt vi nhau l c nh trong sut qu trnh
hun luyn... M R khi hnh thnh tri thc c th gii quyt cc vn c th
mt cch ng n. l nhng vn rt khc nhau, c gii quyt da trn s
t chc hp nht gia thng tin u vo v p ng u ra ca mng. C rt nhiu
thut ton hc c pht minh tm ra tp trng s ti u lm gii php cho cc
22
Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-----------------------
-
bi ton. Cc thut ton c th chia lm ba nhm chnh: Hc c gim st, hc
khng c gim st, hc tng cng.
Hc c gim st: ln hc u tin mng c cung cp mt mu hc cng
vi b trng s t do, u ra thc t ca mng s c so snh vi u ra mong
mun, sai khc gia hai gi tr ny l c s cho vic hiu chinh trng s ca mng,
qu trnh hun luyn din ra lin tc cng vi b thng s u vo cho n khi
mng t c mt gi tr sai s nh mong mun.
u vo
=r>Mng N ron
u ra thc t
H iu chnh trng s
VSo snh
u ra m ong m un
Hnh2.12 M hnh hun luyn mng c gim st
Hc khng gim st: Trong hc khng gim st th khng c bt k mt thng
tin phn hi t mi trng. Mng phi t tm ra cc c tnh, quy lut, tng quan
trong d liu u vo v tp hp li to u ra. Khi t tm ra cc c im ny,
mng tri qua cc thay i v tham s ca n. Qu nh ny c gi l t t
chc.
u vo M ng N ron
A
u ra thc t
Hiu chnh trng s
Hnh2.13 M hnh hun luyn mng khng gim st
Hc tng cng: Trong lut hc c gim st, cc gi tr u ra c bit chnh
xc i vi mi u vo. Tuy nhin, ong thc t c mt s trng hp ch bit t
thng tin chi tit, chng hn mng ch bit rng gi tr u ra thc s qu cao hay c
th mng ch c c thng tin phn hi bo rng u ra ng hay sai. Thut hc
23
Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
-
da trn thng tin nh gi ny c gi l thut hc cng c, thng tin phn hi
c gi l tn hiu tng cng.
Hnh2.13 M hnh hun luyn mng tng cng
2.5 Hm mc tiu
hun luyn mt mng v xt xem n thc hin tt n u, ta cn xy dng
mt hm mc tiu (hay hm cht lng) cung cp cch thc nh gi kh nng
ca mng. Vic chn hm mc tiu l rt quan ng bi v hm ny th hin cc
mc tiu thit k v quyt nh thut ton hun luyn no c th c p dng.
pht trin mt hm mc tiu o c chnh xc ci chng ta mun khng phi l
vic d dng. Mt vi hm c bn c s dng rt rng ri.
Hm tng bnh phng li SSE (Sum of squares error function)
Hm trung bnh tng bnh phng li MSE (Mean sum of squares eor
function)
pal .=1
Trong :
P: S th t mu ong tp hun luyn
Z: S th t ca n v u ra
24
Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
-
tpi v yPi : Tng ng l u ra mong mun v u ra thc t ca mng cho
n v u ra th i n mu th p.
v mt hnh hc c th xem E nh mt mt li. Trong qu trnh luyn mng gi tr E cng nh cng tt.
2.6 Mt s ng dng ca mng n ron nhn to:
T khi ra i v pht trin M R tm v khng nh c v tr ca mnh
trong rt nhiu ng dng c th nh:
+ Mng n ron c th c hun luyn nhn bit vn phong vit ca cc c
nhn v cc nh nghin cu dng so snh cc tc phm ca
Shakespeare v cc nh vn ng thi vi ng do i hc Aston cng b.
+ Mt chng trnh truyn hnh khoa hc ph bin gn y a ra vic s
dng M R do mt vin nghin cu Italia kim a tinh khit ca du
liu.
+ Vin nghin cu in lc hoa k EPRI nghin cu v thng mi ha
phn mm A SLTF (Phn mm d bo ph ti in ngn hn dng M R
nhn to).
Cc v d ny cho thy cc ng dng rng ri ca M R. Cc ng dng ny
ngy cng m rng bi v M R gii quyt vn tt khng ch trong khoa hc, k
thut v ton hc m cn trong y t, kinh doanh, ti chnh, vn hc. ..Cc ng dng
ca M R ti nhiu bi ton trong cc lnh vc khc nhau lm cho M R thm
hp dn. My tnh tc cao hn v cc thut ton nhanh hn cng lm cho vic
s dng M R c th gii c cc bi ton phc tp m trc y i hi mt khi
lng tnh ton to ln.
+ Lnh vc dn dng: iu khin cc thit b gia nh nh my git, iu ha,
cc thit b cnh bo chng trm, bo ng bo chy, d bo thi tit, gi
c...
25
Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
-
+ Lnh vc cng nghip: Cnh bo pht hin s c, xy dng cc b iu khin
thch nghi, thng minh ha cc cm bin trong o lng, nhn dng v x l
tn hiu, phn loi mu, nhn dng ting ni. D bo ph ti in ngn hn,
trung hn, di hn, vn hnh h thng in. D bo gi in ...
+ Lnh vc y t: hn dng sng in tim, in no , cc t bo ung th.
Trong in no M R dng nhn dng cc sng Alpha, Beta, Theta v
Delta chn on bnh....
+ Lnh vc qun s: iu khin cc v kh thng minh, iu khin bm. hn
dng vn tai, hnh nh ting ni....
+ Lnh vc thng mi, kinh t: D bo tnh hnh kinh t, d on tin t, phn
tch mc ri ro, phn tch th trng, d bo mc tng trng...
Ring ong lnh vc h thng in c ng dng ong chun on s c
(thit b in, in t, c kh trm bin p, ng dy, nh my in), phn lp v
iu khin cc h thng ng ( h my in, trm bin p....), ti u ha, d bo,
nh gi an ton h thng in.
Mng n ron nhn to m chng ta s dng xy dng nn cc M R nhn
to thc s l cn rt th s so vi nhng g c tm thy trong b no. Cc M R
m chng ta xy dng c cng ch l mt s phc tho th kch nu em so
snh vi cc mch thn kinh trong b no. hng vi nhng tin b ng ghi nhn
trn rt nhiu lnh vc ong cc thp k va qua, chng ta c quyn hy vng rng
trong tng lai cc M R nhn to s tinh vi hn nhiu so vi hin nay.
26
Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
-
CHNG 3
C IM BIU PH TI TNH SC TRNG
3.1 Biu ph ti in
Ph ti ca h thng l mt hm theo thi gian, ph thuc vo nhiu yu t
nh c im ca qu trnh cng ngh, ch vn hnh.v.v.. Tuy nhin i vi mi
h thng ring s c dng biu ph ti in hnh.
Khi bit c biu ph ti in hnh th s c cn c chn cc thit b
in, tnh in nng tiu th. Lc vn hnh nu bit BPT in hnh th c th nh
phng thc vn hnh cc thit b in sao cho kinh t v hp l nht. Cc nh my
pht in cn nm c BPT ca tng h thng nh phng thc vn hnh
ca cc nh my pht in cho ph hp vi yu cu. V vy, BPT l mt ti liu
quan ng ong thit k cng nh vn hnh h thng cung cp in.
Ty theo nhu cu s dng m ngi ta xy dng cc loi biu ph ti in
khc nhau. ng biu din s thay i ca ph ti tc dng p, ph ti phn khng
Q hoc dng in I theo thi gian. Nu theo thi gian kho st c th ph ti
hng ngy, hng thng, hng nm.
Nghin cu BPT ngy ta c th bit c tnh trng lm vic ca h thng
in t nh qui trnh vn hnh mt cch hp l nht m bo vn hnh kinh t
ca h thng in.
Hnh 3.1 l BPT tc dng ngy in hnh ca cng ty in lc Sc Trng.
th bin thin theo gi tr ph ti 24 gi trong ngy. Ph ti Pmax ln gp 1,9-2 ln
so vi ph ti thp nht trong ngy Pmin. Cao im thng xy ra vo chiu ti
khong t 19h-20h. Thp im thng xy ra vo ban m khong 2h-3h.
27Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
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Hnh 3.1 Biu ph ti c trng ngy h thng in Sc Trng
Nu d bo c Pmax v Pmin cc k s iu hnh c th huy ng v iu
chinh ngun hp l, cng nh vn hnh ngun an ton v hp l hn.
3.2 Cc yu t nh hng n ph ti in:
D bo ph ti l mt bi ton kh. Bi v trc ht chui ph ti in l
chui s liu kh phc tp, ph thuc vo nhiu yu t. Ph ti in ca mt h
thng c cu thnh t cc om v tiu th in khc nhau m ch yu l cc thnh
phn nng nghip, cng nghip, sinh hot v dch v...
Cc yu t nh hng n ph ti ph thuc vo tnh cht ca om v tiu th
in. Ph ti cng nghip ph thuc ch yu vo mc sn xut. Ph ti ny
thng n nh tng i v c th nh gi s ph thuc ph ti cng nghip vo
trnh v quy m sn xut. Tuy nhin, t gc bn bn in, ph ti cng nghip
c tnh bt nh v gy tr ngi cho d bo, bi v c nhng s c my mc thit b
cng nghip hu nh khng d bo c v gy ra nhng bin ng ln trong tng
ph ti ca khu vc v ton h thng.
i vi ph ti nh sng sinh hot, l thnh phn ph ti ph thuc rt nhiu
vo hnh vi ca cc c nhn v cc nhm c nhn ring bit, do rt kh xc nh
28Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
-
nh hng n ph ti in. Mi c nhn thng hnh ng theo cch ring ca
mnh v hnh vi ca h nh hng n tiu th in nng. C th ch ra mt s yu
t hnh vi v x hi nh hng n ph ti nh: Cc ngy l ln, cc ngy ngh,
chng trnh truyn hnh, thi tit thay i lm tng hay gim nhu cu s dng iu
ha, qut in, t lnh...
Sc trng c khong 1,2 triu dn trong c 80% dn s lm nng nghip,
do ph ti in ch yu phc v sinh hot v ph ti nng nghip. i vi ph
ti nng nghip, y l loi ph ti c nh hng ln i vi cc ph ti in ca
a phng ch yu l sn xut nng nghip. y l loi ph ti phc v cc cng
vic nh ti tiu, chn nui, iu tit thy li, ch bin lng thc, ong nui
trng v ch bin thy hi sn l mt loi ph ti in c bit quan trng v s
dng mt lng ph ti ln v phi m bo cung cp lin tc ong mt thi gian
di khi vo ma thu hoch, do ph ti nng nghip thng mang tnh thi v
60
55
50
45
s 40
35
30
25
20
15 500 10000 15000
Gio
Hnh 3.2: th ph ti trong hai nm 2004 n 2005
Hnh 3.2 biu din biu ph ti lin tc trong 2 nm vi s liu c thu
thp ti trm bin p 220 k v ca Cng ty in lc Sc Trng. Ta c th nhn thy
mc dao ng ln trong ng th ph ti ny. Ngoi ra ta c th nhn thy
mt s c im sau:
29Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
-
Thi v:
Da vo ng th thy rng u nm th bt u tng v ph ti t cc
i khong thng 8-9 trng vi khong thi gian thu hoch v h-thu. Mt yu t
nh hng ln lm cho sn in tng cao l vo 2 thng ny v trng vi thi im
thu hoch tm mt sn lng in ln phc v cho ng c to dng chy, thp
sng v st kh oxi vo hai thng cui trc lc thu hoch, bn cnh cng vi vic
thu hoch tm, ph ti cung cp cho cc c s ch bin tm cng tng cao. Ngoi
ra, t thng 1 n thng 4 ng th tng nhanh sau mi gim tc y cng
trng vi thi im cui ma kh khong thng 4.
Biu ph ti ngy trong tun:
Thu hai Thu ba Thu tu Thu nam l iu sa u T1U b a y C hu nhat
Hnh 3.3 th ph ti t 3/1 n 9/1 nm 2005
Xt th ph ti HT hnh 3.3. y l biu ph ti cc ngy trong mt
tun t 3 n 9/1 nm 2005 c xy dng lin tc ong 168 gi. Khng ging nh
ph ti cc thnh ph ln nh H Ni hay TP HCM ph ti thng gim thp
cc ngy ngh th by, ch nht v tng cao cc ngy lm vic. Ph ti Sc Trng
khng tun theo chu k tun, s khc bit BPT trong mt tun cc ngy lm
vic (th 2 n th 6) v ngy ngh (th 7 v Ch nht) thng khng c s thay
30Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
-
i ln, ng BPT trong mt ngy c nhiu nh nhn. y cng l mt s khc
bit ca ph ti gia thnh ph ln v cc tinh nng nghip nh Sc Trng.
Thi tit trong ngy
Thi tit ong ngy l mt tp hp, bao gm cc thng thng s t nhin nh:
nhit , m, tc gi, hng gi v cng nh sng.. .trong tp hp cc
thng s , nhit l yu t nh hng mnh nht ti ph ti. C th xem ph ti
l mt hm s ph thuc vo nhit .
Gia ph ti v nhit l c qui lut ph thuc nh sau: hit tng th
ph ti tng v ngc li. Hnh 3.4 l th ph ti ngy ca hai ngy lm vic ca
HT Sc Trng c nhit khc nhau. Hnh 3.4 gi tr ph ti tng kh lm khi
nhit mi trng tng. Biu ph ti ngy 6/5/2005 l ngy c nhit cao (25.8-
36.2 c) v ngy 19/2/2005 c nhit thp (20.4-25.2 c). C s chnh lch gia BPT
gia hai ngy l l kh ln.
Hnh 3.4 nh hng nhit n thi quen tiu th in
Ngy c bit trong nm:
Sc Trng c 3 thnh phn dn tc l Kinh, Khmer v Hoa sinh sng, ngoi
ngi Kinh chim khong 65% dn s, ngi Khmer chim khong 29% v ngi
hoa chim 6%. Do c cc ngy c bit trong nm nh ngy l, ngy tt, nh tt
m lch, tt (Chn Chm My) v l hi ca ngi Khmer. Cc ngy l ln nh
31Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
-
30/4, 1/5 v 2/9... ph ti cc ngy ny trn u gim so vi ngy thng. S khc
bit trong biu ph ti gia ngy l 2/9 v mt ngy lm vic bnh thng ngy
5/9/2005 ti Sc Trng c th hin n hnh hnh 3.5.
Hnh 3.5 th ph ti mt ngy thng v ngy quc khnh
Hnh 3.6 th ph ti mt ngy thng v ngy tt dn tc
Hnh dng ng ph ti cc ngy tt dn tc hnh 3.6 cng b nh hng do
thi quen sinh hot ca khch hng thay i. D bo ph ti cho cc ngy c bit
khng p dng nh ngy thng m phi theo phng php ring, da vo s thay
i ph ti ca cc ngy ny so vi ngy thng trong cc nm trc. Biu ph
ti ngy mng mt tt ngy 6/2/2005 ng ph ti lc ban ngy thp trong khi ph
ti ban m li tng cao so vi ng ph ti cc ngy bnh thng.
32Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
-
Hnh 3.7 th ph ti mt ngy thng v ngy c l hi
Hnh 3.7 biu din ph ti b gim st ngy 16/10/2005 din ra l hi ua ghe
go (oc Om Bc) ca ngi Khmer v mt ngy bnh thng trc , ngy
15/10/2005.
Cc chng trnh truyn hnh trc tip cc s kin th thao vn ho ln, thu
ht ng o qun chng hm m, c bit l bng c nh hng khng nh n
nhu cu tiu th in nng. Hnh 3.8, dng biu ph ti trong cc ngy truyn
hnh trc tip cc s kin th thao vn ho cng thay i. Cng sut tiu th vo cc
gi truyn hnh trc tip (Cp bng th gii, cp Cl, Euro, Tiger Cup....) BPT
t ngt tng cao.
33Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
-
Hnh3.8 th ph ti m c chung kt Euro v m bnh thng
K hoch sa cha ln:
Sc Trng l mt tnh nh h thng in hin nay c xem l ang pht trin
do nhu cu nh ci to trm bin p, ct in ng dy ang vn hnh ko
ng dy mi, ci to nng cp ng dy.. .vn phi ct in trn din rng, dn
n in nng tiu th gim mt cch ng k.
Hnh 3.9 th ph ti ngy bnh thng v ngy c ct in
D bo cho cc ngy ny cn phi tnh ton khu tr ph ti do ngng cung
cp in. Dng biu ph ti trong ngy c ct in cng mang tnh c th ring,
thay i theo thi gian v khu vc ct in.
Nhn xt:
i vi nhng ngy l tt, cc ngy c bit, nht l nhng ngy ct in trong
nm nh hng n cng tc d bo ph ti. Cc ngy ny xut hin tng i t
ngoi tr nhng ngy ct in. Trong mt nm c khong 20 ngy iu ct in
mt s tuyn phn nh trong tp s liu thu thp c. e m bo tp s liu
hun luyn c lin tc. i vi nhng ngy b ct in ta c th ly trung hnh
ca hai ngy k cn. iu ny l cho php khi ta c tp s liu ln.
Qua qu trnh nghin cu, thng k s liu v kinh nghim vn hnh cc nh
nghin cu, chuyn gia iu i n kt lun: nhit mi trng - thng s thi
34Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
-
tit quan trng nht ong ngy, yu t ma v v cc ngy c bit nh ngy l l
bin nh hng mnh nht n gi ph ti ngy.
3.3 Dng biu ph ti:
Xt th ph ti HT hnh 3.10. y l biu ph ti HT Sc Trng ngy
lm vic 12/12/2004 c xy dng theo gi tr ph ti 24 gi trong ngy. th
ph ti phn b khng u, dng th nhn v chnh lch gia cng sut cc
Hnh 3.10 Biu ph ti in hnh ca mt ngy
t: Trong lun vn ta s s dng k hiu nh sau:
p = \p yP ^ ,...,p ^ - th ph ti ca ngy ang xt
pn = \PnVPnT",P n2A] " ^ chun ha t p
theo cng thc p (z) = Pmin p ^ n Pmax - Pmin
Vi Pmin = min P(i)
Pmax = max P(i)
Ta c th chun ha c max p n(i) = 1
min p(i)= 0
35Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
-
nh trn hnh 3.11
Hnh 3.11 Biu ph ti mt ngy sau khi qui chun
Hnh 3.11 l th ph ti c chun ho ca cc ngy trong tun c
xy dng theo cc bin i v bin P(). Biu ph ti c quy chun vn gi
nguyn dng bin thin ca mnh v cc gi tri ph ti c quy chun nm trong
khong t 0 -- 1, vi Pmax = 1 v Pm in = 0. c im ny khng ph thuc vo
gi tr nh v y ca biu ph ti gi trong ngy c quy chun nhn cc gi
tr ln hay nh n mc no.
3.4 nh v y biu ph ti (BPT):
Xc nh hai gi tr c bit trn th ph ti, ph ti cao im v thp im
l mc tiu quan trng hng u ca ngi lm cng tc d bo. Sau khi xc nh
c hai gi tri quan trng nht BPT Pmax v Pmin cn cc gi tr khc trong
ngy s c xc nh theo mi quan h ca chng vi nh v y ca BPT
thng qua dng BPT ca ngy d bo.
Vy nu bit dng biu ph ti qui chun cn gi l vc t BPT, tc l
bit Pn xc nh c Pmax v Pmin ca TPT trong ngy ta s tnh c ph ti
ca tng gi trong ngy nh sau:
36Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
-
P(i) = Pmn + (Pmax - Pmin)P i
Kt lun:
Da vo cc phn tch trn c th i n kt lun: d bo c ph ti tng
gi P(i) cho mt ngy c th, ta cn xc nh dng biu ph ti - vc t biu
ph ti p(i) vi i=,2,3...24 ca ngy cn d bo v d bo c gi tr ph ti
nh Pmax, gi tr ph ti y Pmn ca ngy .
Cng nh cc phng php d bo khc, d bo ph ti ngy phi da vo
thng k s liu, phn tch v p dng cc thut ton tm ra mi quan h gia ph
ti v cc yu t nh hng v t c th xy dng phng php d bo ph ti
ngy.
Phn tip theo, chng ta s nghin cu gii quyt bi ton d bo hnh dng
biu ph ti, thng qua vic s dng thut ton trng tm m. Tu thuc vo c
im ca b s liu thu thp c s tin hnh phn tch v la chn cch phn
nhm th ph ti sau cho ph hp nht.
37Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
-
CHNG 4
NG DNG MNG N RON NHN TO TRONG BI
TON PHN LOI KIU NGY
4.1 i tng phn loi
i tng phn loi l cc dng biu trong qu kh. Thng thng cc
s liu ny thng c o trong khong thi gian lin tc. tin hnh phn loi
t cc s liu o lng ban u, ngi ta tin hnh gia cng s liu, tm ra cc c
th ca i tng thuc cc nhm khc nhau xp cc biu tng i ging
nhau vo mt nhm. Khi tin hnh phn loi BPT in c th tm ra cc du hiu,
cc du hiu chnh l c s quyt nh s nhm n phn nh thi quen s dng in
ca h thng in , do n mang tnh c th ring i vi tng h thng in.
Bi ton phn loi BPT c hiu l i tm cc quy tc xp cc biu tng
i ging nhau vo cng mt lp.
4.2 Phng php phn loi dng BPT
Thng thng, bng kinh nghim vn hnh ca bn thn, cc chuyn gia lu
nm c th phn bit c cc kiu ngy gc c trng trong qu kh. Tuy nhin,
trong qu trnh vn ng khng ngng ca x hi, c cu kinh t v t ng cc
ngnh cng nghip thay i, thi quen sinh hot khch hng thay i..., theo thi
gian s xut hin mt s kiu ngy mi hoc mt s kiu ngy trong qu kh s
khng xut hin na trong tp hp cc kiu ngy gc c trng m ch vi kinh
nghim ca cc chuyn gia nhiu khi khng pht hin c v cp nht kp thi. V
chnh l nhc im ln trong qu trnh d bo theo kinh nghim ca chuyn
gia.
Vic s dng MNR nhn to phn loi kiu ngy l mt gii php khc
phc c hn ch n. Nh c ch hun luyn li MNR vi cc s liu c cp
nht nh k, h thng d bo c th tm ra v thch ng vi kiu ngy mi pht
38Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
-
sinh khng ging vi mt trong cc dng gc hoc loi b cc kiu ngy khng cn
xut hin na.
Trong qu trnh hun luyn mng, khi a cc mu dng biu ph ti vo
mng, ta hon ton khng a yu cu cn phi thu c kt qu g - bao nhiu
biu mu u ra. Qu trnh hc ny gi l hc khng gim st m MNR nh x
c trng t t chc Kohonen l mt i din mang trong vic phn loi cc biu
ngy trong nm.
Theo cc nghin cu ca [2,6,11] mng Kohonen c ng dng trong vic
phn loi BPT u cho kt qu tt. Hu ht cc nghin cu ny u s dng mng
Kohonen kinh in vi thut ton thng s dng l LQV, tuy nhin lut hc ny
cho kt qu hi t kh chm v mt kh nhiu thi gian hun luyn, hin nay xut
hin mt s thut ton hc mi c ng dng cho vic xy dng mng Kohonen
m in hnh l thut ton ng tm m Fuzzy Clustering Method (FCM) cho kt
qu hi t nhanh hn, thut ton ny s c ng dng phn loi BPT ong
lun vn ny.
4.3 Mng Kohonen v ng dng trong phn loi kiu ngy
4.3.1 Gii thiu
SOM {Self Organization Map) l k thut trc quan ha d liu. Gii thut
c xy dng bi gio s Teuvo Kohonen da trn kin trc mng Kohonen.
im ni bt ca thut gii SOM l n s chuyn cc dng quan h phc tp, thng
k ri rc gia cc i tng d liu a chiu (n chiu) v cc quan h hnh hc trc
quan om gin vi s chiu c rt gn i nhiu ln - thng l mt hoc hai
chiu, v bn cht thut gii c bit n nh l k thut nn d liu da trn vc- t trng s.
Thut gii s xy mng Kohonen lu tr thng tin nh l cch duy tr ca
cc quan h hnh hc bn trong tp hun luyn.
Mt trong nhng kha cnh th v nht l SOM l mt dng ca thut ton
hc phn loi d liu hun luyn m khng cn bt c s gim st bn ngoi no
39Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
-
so vi cc gii thut hc c s gim st truyn thng. Th nn SOM cn c
xem l mt gii thut hc khng gim st.
4.3.2 Thut gii SOM
Thut gii hun luyn SOM c th c m t theo cc bc c bn nh sau:
a. Khi to: Cc vc t trng s cho tng nt trong mng c khi to. Cc
gi tr khi to ny thng c chn mt cch ngu nhin v tha tiu
chun nh.
b. Chn phn t i din: Mt vc t s c chn ngu nhin t tp hun
luyn v tr thnh phn t i din ca nhm.
c. Tm mu khp tt nht (MBU-Best Matching Unit) - phn t neuron chin
thng: Mi nt trn mng s c kim tra tnh xem nt no c ng s
gn vi vector nhp nht. Phn t chin thng c xem l phn t so khp
tt nht MBU.
Thut gii tm mu khp tt nht c thc hin nh sau:
> Duyt tt c cc nt v tnh khong cch Euclide gia vector trng s ca
mi nt v vc t nhp hin hnh.
Cng thc tnh khong cch Euclide c cho nh sau:
V: vc t nhp hin hnh
W: vc t trng s ca phn t c chn
> t c vector trng s gn nht vi gi tr ca vc t nhp s c chn l
MBU
d. Xy dng cc phn t ln cn: Bn knh ln cn ca MBU s c tnh li.
Bn knh c xc nh ln nht thng s l bn knh ca mng, nhng sau
40Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
-
gi tr ny s gim dn sau nhng bc thc hin. Tt c nhng phn t
nm trong bn knh trn s c xem l phn t ln cn ca BMU.
4.4 Phng php trng tm m Fuzzy Clustering Method (FCM):
Thut ton nhm trung bnh (C-means clusterings) c cng b ln u tin
bi Duda v Hart c gi l thut ton Hard C-mean (hay cn gi l Hard
ISODATA). Phin bn ci tin cui cng ca thut ton c Bezdek gii thiu.
Khng ging nh thut ton Kohonen cc trng tm c lin kt bng mt
li, phng php trng tm m cc ng tm hon ton chuyn ng c lp
trong khng gian v ch ph thuc vo s liu.
Phng php trng tm m ngoi vic xt n nt c ta gn vi vc t u
vo nht, cn xt n c nhng nt khc nhng vi ng s nh hom, t l nghch
vi khong cch t nt ti vc t u vo. iu c ngha l mt vc t s ph
thuc vo nhiu nt trn mng, khong cch cng xa ph thuc cng thp. Trn
c s cc trng tm, khng gian s liu u vo c chia thnh nhiu nhm. Mi
nhm c i din bng ng tm ca chng. i din ca mt nhm c gi l
mt nguyn mu.
Trong thut ton ny cc d liu c tnh cht c bit gn nhau c tp hp
thnh nhm, chng c ma trn ph thuc u . Cho tp X mu vi X={xl,x2,..xj},
trong mi nhm xl,x2,..xj c ta 24 chiu. Vc t th xj thuc v nhm th i
vi quan h hm cho bi.
C - l vc t trng tm v r l thng s rng ca hm. Vc t X ph thuc
mt vi nhm vi bc khc nhau c gi tr t 0 n 1 (tng mc ph thuc ca mt
vc t X vo cc tt c cc trng tm bng 1).
= 1=1
41Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
-
Tng hp cc mc ph thuc, ta c ma n ph thuc u . Cc h s ca ma
trn ny cho bit khong cch t cc mu d liu n tng nhm, h s ph thuc
cng ln th khong cch gia trng tm v mu d liu cng gn nhau.
Cc trng tm c tm kim trn c s ti u ha hm chi ph. Hm ny c
nh ngha bi:
trong : d l khong cch Elt t trng tm Ci n vc t Xj
dkj l khong cch Elt t trng tm Ck n vc t Xj
Thut ton FCM c thc hin theo cc bc sau:
- u vo ma trn u c th khi to ngu nhin vi cc gi tr t 0 n 1;
- Tm K trng tm nhm m Cj s dng cng thc nh trn;
- Tm gi tr ca hm E. u E t ngng t trc hoc nu E khng c
ci tin so vi bc trc th kt thc qu trnh lp, ngc li thc hin bc
k tip;
- Tnh ton bc t do mi ca ma trn u s dng cc cng thc trn v v
ff
E II ci ~X1 II2
ta c th s dng
(4.1)1
bc 2.
42Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
-
Bc tnh lp ny c thc hin nhiu ln. chnh xc ca li gii c xc
nh bng cch la chn trng tm ca nhm t gi tr t do ca ma trn u . Cc
trng tm ny tp trung xung quanh ni c nhiu im d liu nht.
V d hot ng ca thut ton n c trnh by trn hnh 4.1 vi 3 trng tm
c khi to trng ti mt im. Sau khong 20 vng lp, cc trng tm dch
chuyn v cc trung im ca vng tp trung d liu v hi t ti .
(* Label Data
Clear Traj.
MF Plot
2- Fuzzy -Mpanc
File Edit V iew Insert Tools Desktop W indow Help
A A B I mm a | \ \ \ ^ T go -Hi
Close
Hnh 4.1: Qu trnh dch chuyn ca cc trng tm t v tr ngu nhin ban u v cc
vng s liu
4.5 ng dng thut ton v chy th mng
4.5l X l s liu thu thp
Trc khi d liu a vo phn loi, chng ta phi x l s b gip cho
gii quyt kt qu phn loi c tt hn. Tin x l c th gip lm gim kch
thc ca vc t u vo bng cch loi b nhng ngy ph ti b ct do sa cha
hoc iu .
43Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
-
Theo cc nghin cu trc y [1,2,4,9] vic phn loi th ph ti trong
nm phn ln da vo phng php ngy trong tun, biu ph ti ngy lm vic
ny thng khc vi ngy ngh cui tun. M hnh ny thng phn bit cho cc
nhm ngy lm vic t Th Hai cho n Th Su, v nhm ngy ngh cui tun v
l tt. Yu im ca phng php ny l cc ngy ngh cui tun v l tt thng
cho kt qu d bo c chnh xc kh thp, thnh thong cc ngy lm vic trc
Th by v Ch ht b nh hng bi cc ngy ngh ny. Vi cch phn loi ny
cng khng hon ton ng cho tt c cc vng. Vic phn loi cng cn da vo
c th iu kin, thi quen, tp qun s dng in ca tng a phng.
Vi c th th ph ti ca hai nm 2004 v 2005 ti Sc Trng vic p
dng phng php phn nhm theo ngy trong tun l khng hiu qu v BPT cc
ngy lm vic v ngy ngh hu nh khng thay i nhiu, gy kh khn trong vic
phn nhm. Mt trong nhng cch phn loi c th p dng cho h thng in t c
s thay i nhiu ong tun l m hnh th trong thng lnh hot.
452 Phn nhm biu ph ti:
Chn mng bao gm:
S u vo l c nh, ph thuc vo s nhn t s dng: ong bi ton phn
loi kiu ngy ta s dng 24 gi tr (ng vi 24 gi trn th ph ti), do s u
ra l 24. s n ron u ra bng s nhm cc kiu ngy khc nhau m ta cn phn
bit.
Cch thc phn nhm nh sau: Cc ngy cng th trong mt thng ca hai
nm c a vo mng tm trng tm cch thc tm ng tm theo tiu ch th t
u tin:
1. Cc ngy trong thng chia lm 4 nhm: t mng 1 n mng 7, t
mng 8 n 15, t 16 n 23, t 24 n cui thng.
2. Cc ngy ong thng chia lm 3 nhm: t mng ln mng 10, t 11
n 20, t 21 n cui thng.
44Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
-
3. Cc ngy ong thng chia lm 2 nhm: tng mng 1 n ngy 15,
tng ngy 16 n cui thng.
4. Cc ngy trong thng c dng th ph ti tng ng nhau v c
th xp chung trong 1 nhm.
Tm trng tm theo cch chia: Cc phn t thuc cng mt nhm ch t
[1 ..10], [11..20], [21..31] cc trng tm ca nhm s l i din cho nhm nu
ngy cn d bo ri vo nhm ca ngy no s ly trng tm lm th ph ti
mu.
Chn s liu thng 07 nm 2004 v 2005
2004_________________ ______ Thng 7 2005_________________ ______ Thng 7c Hai Ba T m Su By
1 2 34 5 6 7 8 9 1011 12 13 14 15 16 1718 19 20 21 22 23 2425 26 27 28 29 30
c Hai Ba T m Su By1 2
3 4 5 6 7 8 910 11 12 13 14 15 1617 18 19 20 21 22 2324 25 26 27 28 29 30
Kt qu phn nhm ngy th 6 thng 7 bao gm cc ngy 2,9,16,23,30,1,8,15,22,29
theo th t t l-> 10 trc khi a vo phn nhm vi:
> u chia lm 2 nhm:
Vi center l trng tm c ma trn 2x24: Vi hai trng tm (mi hng l mt
trng tm)
hm th nht bao gm cc ngy: 9,23,30,1,29 vi 1 trng tm lm i in
hm th hai bao gm cc ngy: 2,16,8,15,22 vi 1 trng tm lm i in
45Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
-
11 File Edit Debug Desktop Window Help
D c Jt % w H I f Current Directory: C: 'Program FilesyMATLAB704\wark i l j
c e n t e r = -1
C o lum ns 1 t h r o u g h 15
0 .04 0 .0 2 6 5 0 .0 4 8 2 . 24 5 0 057 0 . 3 1 5
0 .0 9 4 4 0 .0 8 1 0
0 . 20 93 Q .181 6
D.2 5 2 1 .2 4 4 7
0 . 321 Q .2 719
0 .4 8 3 5 .780 .3 9 5 3 0 .5 9 4 3
0 . S3 8 8 Q.5 5 66
0 .3 3 3 2 0 .3 3 1 0 .2 3 6 6 0 .2 0 8 5
C o lum ns 1 t h r o u g h 24
. 9 0 H 0 81210 0 .7 2 4 0 0 .B 15 0 . 8 3 2 0 .6 0 5
0 .9 4 0 8 0 .9 5 3 6
. 85 92 0 .8 9 4 2
.J457 0 .8 7 2 2
.3 8 2 3 0 . 5 071
0 .1 7 94 0 . 0 64 9 0 .2 8 1 1 0 .1 3 1
u =
.4 98 9 0 .5 3 1 4 0 .1 8 93 D.5 0 1 1 0 .4 8 6 0 .8 1 0 7
0 .8 7 9 3 0 .1 2 0 7
.8 3 4 8 0 . 152
0 . S 8 9 1
0 .3 1 0 90 . 391 0 .6 0 3 9
.2 0 0 3 0 .2 2 4 4 0 .7 9 9 7 0 .7 7 5
. 51&1 D.4 2 3 3
nhom =
2 4 5 6 10
nhom =
1 3 7 8 9
u chia lm 3 nhm
File Edt PtlHig 0#tQ p Window Hlp
t % * - - K Of CTwlCwoc1y. Trap m i j jA * =
c o lu m tn i icQUth S
0 .0 4 4 9 O .fttST G.OiOfl 0 .0 8 6 9 6 .0 4 S 0 . 491 0 - J l S i 0 . 4 ? O .S iS l 0 .M H 0 .1 * 5 1 0 -S 1 1 t . n t l0 .0 2 * 9 n .0514 0 .0 1 1 4 O .0 7 o . i e a ? 0 . S 9 0 .2 4 5 2 0.3 G.Q103 0 .7 5 5 1 0 ,3 9 3 0 0 .1 8 3 ? O-0S330 .7 9 2 0 .6 5 9 ? 0 . 5 ? 0 .9 3 9 3 0 12 0 . 9373 0 .5 1 2 1 a . 3262 0 .1 7 0 30 ,0 4 5 9 0 .727 0 .f i2 ? a 0 . S>S2i D.0557 0 .7 4 0 4 0 .3 1 9 0 0 .1 7 4 3 0 ,0 7 1 ?
a
0.2 5 4 4 O .3 5 0 0 .1 6 0 0 0.D.7 0 .70 a . *581 0 .1 3 9 9 O . n 0 .1 1 1 2 0 .4 3 3 20 . 0 5 l 0 ,2 1 7 3 0 .S 2 2 1 O.04T8 0.01ST 0 .1 7 2 0 0.1.344 O.KT7* 0 .7 2 0 0 0 , 0 0 3.S405 0 .12 S 0.31SG 0 . H i s 0.2119 0 3691 O .b S iS 0 .1 1 1 1 0.1B8 0,2862
* i 6 u>nlwn -
ft
n-lin =
I 1
* I I .JH T ,
Vi center l trng tm c ma n 3x24: vi ba trng tm (mi hng l mt
trng tm)
hm th nht bao gm cc ngy: 23,30,1,29
hm th hai bao gm cc ngy: 16,15,22
46Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
-
hm th ba bao gm cc ngy: 2,9,8
> u chia lm 4 nhm- MA71AB 377
Pile Kett Obq 0*5* top Window Mflp
D w f tULHMKHMbnk l l J B
...... ............. d
Colum ns l th ro u g h 24
0 ,9 0 4 1 0 ,8 1 3 3 D.7555 0 .9 0 4 2 0.0094 0 .7 0 0 6 0 .4 7 0 .1 9 2 0 0.Q3?O.B20? 0.B52 o . f i i n 0 .9 8 8 0 O.S7S> 0 ?BS6 0.414 0 .2 0 4 3 0 .0 9 3 10 .9 9 6 1 . 616 9 0 .-d 2 B .m & s t.4 3 f il O.OSU a . 11 48 n 0-T40 .7 5 0 2 0 . 6030 0.5 4 3 2 0 . 9264 .8Q 0 . STlO o . ta 0.334'? 0 .1 7 0 6
l
0,534 o . m s 0 ,* i2 IXTJ< O.OO 0-194 O-IS 0-093 9 . Ho.it 0.4516 0.0900 0.13? 0,001? 0.1639 Q.311 o . r m
0.0977 o .o s n 0.0508 0.0303 O-Cne 0.99*7 0 .0 W 0.0440 0 .0 iee 0*15 ?O.ISSS 0,1420 0.3X-J-? o .o s e s 0.CH 3 0 . 0 1 0 0 ,0 1 7 7 0 ,* 7 S o,S X i 0 .2 0 9 2
nJn -
4 5 10
t. =
3 7
SlttCO -
8 9
1 1 st*n P
Vi center l trng tm c ma trn 4x24: vi bn trng tm (mi hng l mt
trng tm)
hm th nht bao gm cc ngy: 9,23,30,29
hm th hai bao gm cc ngy: 2,16,8
hm th ba bao gm cc ngy: 1
hm th t bao gm cc ngy: 15,22
Bng 4.1 Kt qu phn nhm th su thng 7:
Th su: 2,9,16,23,30,1,8,15,22,29
2 nhm:
[1..15][16..30]
- 9,23,30,1,29
- 2,16,8,15,22
3 nhm:
[1..10][11..20][21..30]
- 23,30,1,29
- 16,15,22
4 nhm:
[1..7][8..15][16..21][22..30]
- 9,23,30,29
- 2,16,8
47Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
-
- 2,9,8 - 1
- 15,22
Phn tch:
- Trng hp 2 nhm: Vi kt qu hai nhm ta khng th chn c s nhm
nh mong mun vi nhm th nht bao gm cc ngy t 9,23,30,1,29 nhm
th hai bao gm 2,16,8,15,22.
- Trng hp 3 nhm: C th chia nhm th nht bao gm cc ngy
23,30,1,29 s i din cho cc ngy t [21...30], nhm th hai bao gm cc
ngy 16,15,22 s i in cho cc ngy t [11...20], nhm th ba c cc
ngy 2,9,8 s i din cho cc ngy t [1..10]. C th nhn thy vi cch chia
ny cc ngy cng kiu u c xp vo mt nhm mong mun, goi tr
ngy 1 ca nhm th nht c xp vo cc nhm ngy [21.. .30] v ngy 22
ca nhm th hai c xp vo cc nhm ngy [11 ..20], guyn nhn c th
do thi tit hoc do c s kin nh hng n ch tiu th in v cung
cp in.
- Trng hp 4 nhm: Vi kt qu phn loi bn nhm ta khng th chn
c s nhm nh mong mun vi nhm 1 bao gm cc ngy t 9,23,30,29
nhm th hai bao gm 2,16,8 nhm th ba ch c 1 ngy nhm th 4 bao
gm hai ngy 15,22.
h vy vi cch chia 3 nhm l ph hp nht v t c mc tiu nh yu cu.
Bng 4.2 Kt qu phn nhm ngy th by thng 7:
Th by: 10 17 24 9 16 23 30
2 nhm:[1..15][16..30]
- 17,24,9- 10,16,23,30
3 nhm:[1..10][11..20][21..30]
- 17,24,9- 30- 10,16,23
4 nhm:[1..7][8..15][16..21][22..30]
- 16- 17,24- 23,30- 10,9
48Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
-
Vi cch chia n ta c th chn cch chia 4 nhm chn 3: nhm 1 bao gm
hai ngy 17,24 s i din cho cc ngy t [11..20], nhm 2 bao gm hai ngy
23,30 s i din cho cc ngy t [21..30], nhm 3 bao gm hai ngy 10,9 s i
din cho cc ngy t [1..10],
Bng 4.3 Kt qu phn nhm ch nht thng 7:
Ch nht: 4 11 25 10 17 24 31
2 nhm:[1..15][16..30]
- 10,31- 4,11, 25,17, 24
3 nhm:[1..10][11..20][21..30]
- 4,11,24- 25, 17- 10,31
4 nhm:[1..7][8..15][16..21][22..30]
- 4,11- 10,31- 25, 17- 24
Vi cch chia trn c th chn cch chia 2 nhm chn 1: 1 nhm gm cc
ngy 4,11, 25,17, 24 s i din cho tt c cc ngy [1..30] trong th.
Bng 4.4 Kt qu phn nhm th hai thng 7:
Th hai: 5 12 19 4 11 18 25
2 nhm:[1..15][16..30]
- 12, 19,4- 5 ,11,18,25
3 nhm:[1..10][11..20][21..30]
- 12,4- 19,11- 5 ,18, 25
4 nhm:[1..7][8..15][16..21][22..30]
- 12,4- 11- 5,25- 19, 18
C th chn cch chia 3 nhm chn 2: nhm 1 bao gm hai ngy 12, 4 s i
din cho cc ngy t [1..15], nhm 2 bao gm hai ngy 5,18,25 s i din cho cc
ngy t [16..30].
49Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
-
Bng 4.5: Kt qu phn nhm cho c hai nm 2004, 2005
xThng
Th \1 2 3 4 5 6 7 8 9 10 11 12
c 3 2 2 3 3 1 1 2 2 3 2 1Hai 2 2 2 2 2 2 2 3 1 2 1 1
Ba 1 1 2 1 1 2 2 2 2 2 2 2
T 1 2 2 2 2 2 2 2 2 2 2 1
m 1 2 2 2 2 2 2 2 2 2 1 1
Su 2 1 2 3 2 2 3 3 1 2 2 2
By 1 2 2 2 1 2 3 1 1 1 1 1
h vy: Ty thuc vo kt qu ca mi ln phn nhm m s nhm c
chn c th l 1 nhm, 2 nhm, 3 nhm cho mt th. d bo hnh dng ph ti
cho mt ngy cc thng tin cn thit l th, ngy v thng.
4.6 Xy dng giao din d bo hnh dng biu ph ti:
Cc nhm sau khi c phn loi theo tiu ch th ong thng. Trng tm ca
mi nhm c lu li thnh c s d liu phc v cng tc d bo hnh dng biu
ph ti. Chng trnh d bo biu ph ti c xy dng n phn mm
Matlab, d bo biu ph ti mt ngy ta cn xc nh cc thng tin v Thng
v Th ca ngy cn d bo, hai thng tin ny l c s cho vic la chn cc nhm
trong th ca thng cn d bo, kt hp vi yu t gy cn d bo s cho ra biu
ph ti ngy cn d bo.
Hnh 4.2: S khi d bo hnh dng th ph ti
50Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
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V d d bo hnh dng BPT ngy 1 thng 1 nm 2006: Ta s chn ngy
v thng chng trnh s t ng cp nht th v hin th biu ph ti nh sau:
th bn tri hin th cc nhm ca thng 1 ngy ch nht, s c 3 nhm. Kt hp
vi yu t ngy s cho ta hnh dng biu ph ti. th bn phi, v ngy l ngy
1 nn chng trnh s cho ta hnh dng biu ph ti ca nhm 1. Chng trnh
tm trng tm c trnh by phn ph lc I.
Kt lun:
Mng Kohonen vi thut ton tm trng tm FCM cho kt qu phn nhm nhanh
do c th th nghim vi nhiu cc phn loi khc nhau, lun xp cc i
tng ging nhau vo cng mt nhm.
Vi cch phn loi ny mt mt c th tm ra cc du hiu ging nhau trong mt
th v xp chng vo mt nhm, mt khc vi cch phn loi ny cc gi tr ph
ti ca nhng ngy b ct ti hoc iu u b tch ra khi nhm do s loi
b c nhng ngy ph ti khng bnh thng.
51Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
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Khc vi cc thnh ph khc nh H i hay TP H Ch Minh ph ti tng cao
cc ngy lm vic v st gim ngy ngh do c th chia lm ba nhm
ong tun (cc ngy lm vic, th by v ch nht), m hnh trn c gi l
m hnh ngy ong tun. Tuy nhin, ph ti cc vng nng nghip nh Sc
Trng khng tun theo quy lut , yu t nh hng th ph ti l theo thi
v, thi quen sinh hot v iu kin thi tit do s dng phng php phn
loi theo th trong thng lnh hot l gii php hp l nht v m bo chnh
xc nht nh.
h vy nhn thy rng i vi tng vng tng a phng s phi xy dng
m hnh khc nhau ph hp vi tng a phng c th, ta khng th a mt
m hnh d bo thnh cng vng ny s dng cho vng khc.
52Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
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CHNG 5
XC NH CC THNG S U VO CHO MNG NHIU LP MLP
Trong lun vn ny, mng MLP (Multi Layer Perceptron) c s dng
tnh c lng gi tri cng sut cc i v cng sut cc tiu ca ngy hm sau da
trn cc thng s v cng sut cng nh nhit ca cc ngy trc . Mng MLP
ni ring v MNR ni chung c c trng bi cc thut ton hc - cc thut
ton cho php xc nh cc thng s mng ti u cho mt b s liu mu cho trc
no . Qu trnh hun luyn MNR nhn to c th c chia thnh: Hc c gim
st v hc khng gim st. Mng nh x c trng t t chc Kononen l loi mng
hc khng gim st, c dng phn loi biu ph ti chng 4, v trong
qu trnh phn loi ta khng nh r u ra mong mun cho mi biu u vo, v
khi bit c hnh dng biu ph ti ngy cn d bo th vic d bo c
cng sut cc i v cng sut cc tiu li cng quan trng hn na. i vi vn
d bo ph ti nh v y, khi ta bit r u ra (ph ti nh v ph ti y) ca
mi thng s u vo (d liu thi tit, biu ph ti trong qu kh v cc d liu
khc) ca cc mu hc, th cn s dng MNR vi qu trnh hun luyn c gim st.
MNR MLP vi k thut hun luyn lan truyn ngc sai s trong qu trnh hc
(Back - propagation Neural Network) s c dng gii quyt bi ton d bo
ph ti nh, ph ti y ca biu ph ti.
Chng 5 ny s trnh by cch chn la cc thng s u vo hun luyn
mng bng phng php phn tch tng quan gia hai yu t, mng MLP, l
thuyt thut ton L-M, nh by cu trc, v phng thc hun luyn mng.
5l La chn cc thng s u vo phc v qu trnh hun luyn mng n ronTheo cc nghin cu c thc hin [1,7,16] mt ong nhng mc tiu
trong vic la chn lm thng s u vo trong qu trnh hun luyn mng n ron l
53Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
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nhit max, Tmin, Taver), m, tc gi, biu ph ti trong qu kh (1
gi trc, 1 ngy trc, 2 ngy trc, 7 ngy trc..)... s l cc thng s u vo
phc v qu trnh hun luyn M R. Tuy nhin hu nh cc nghin cu ny cha
ch ra c ti sao li s dng cc thng s ny phc v qu trnh hun luyn v s
u vo cho mng bao nhiu l hp l.
Trong lun vn ny vi s liu thu thp c biu ph ti v nhit Tmax
Tmin trong ba nm ong s ch s liu ca hai nm u phc v qu trnh hun
luyn mng v mt nm cui dng chy th mng. Lun vn s da vo mi
tng quan ca biu ph ti trong qu kh, phn tch tng quan gia cng sut
cc i v cng sut cc tiu. S tng quan ny l c s la chn cc thng s
u vo phc v qu trnh hun luyn mng. Ring yu t thi tit c mi quan h
phi tuyn vi ph ti, do s khng xt mi tng quan gia thi tit v ph ti,
yu t thi tit s kt hp vi cc u vo ph ti hnh thnh cc m hnh mng
khc nhau.
5.1l Phn tch tng quan:Mt trong nhng mc tiu nghin cu ph ti v khoa hc ni chung l tm ra
mi nhng mi tng quan gia cc yu t ph thuc ln nhau v qua c th tin
lng mt yu t ph thuc t cc yu t c lp. Mi tng quan y bao gm
cc c im nh mc tng quan.
Chng hn tm mi lin h gia Cng sut Pmax v cng sut Pmin c
ngha l tm mi tng quan gia hai bin ny ra sao v c th s dng Pmax
tin lng Pmin cho mt ngy hay khng. Trong mi lin h ny, chng ta xc nh
Pmin l bin ph thuc v Pmax l bin c lp. Vy nu gi X l bin Pmax v y l
bin Pmin, chng ta tm hiu mi tng quan gia X v y, h s tng quan cng
cao mi quan h gia X v y cng ln v ngc li.
Gi X vyi l hai bin quan st c. Gi s ta c n i tng th i=l,2,3.. .n.
Gi X v l hai s trung bnh ca bin quan st c; S 2X v s 2y ln lc l
phng sai ca hai bin, c nh ngha nh sau:
54Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
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Hip phng sai:
1 nC O v(jC ,y ) = - = - r 2 , ( j C ( - * K > / - )
n 1 (= 1
H s tng quan:
c o v f o y ) _ cov(x,y) yjvax(x).vai(y) sx x s y
Cng thc trn cn c bit n nh l h s Pearson (Pearsons correlation
coeffcient) ngh nhn cng hin ca nh thng k hc ni ting Karl Pearson,
ngi u tin pht trin l thuyt tng quan vo u th k 20.
i vi X, y nh trn hnh (a) mi lin h ca X v y hon ton xc nh v
tuyn tnh; c ngha l cho bt c gi tr no ca X chng ta u c th xc nh
c gi tr ca y th ta s c r=l.
Kh mi lin h gia X v y hnh (b) l o ngc tc X tng th y gim kh
gi tr ca r l m.
V kh hai bin X v y l ton ton c lp hay nh trn hnh (c) gi tr c l
hng s v khng ph thuc gi tr ca X kh r=0
I----------1----------1----------1----------1----------1----------1
2 4 s s ID 12 1+
(a) (b) (c)
55Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
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Mi lin h gia X v y: (a) r=l, (b) r= -1, (c)=0 (c lp).
Trong thc t khoa hc thc nghim, t khi no chng ta c nhng mi lin h
xc nh nh va trnh by. Cc mi lin h gia X v y thng dao ng cao hn -
1 v thp hn 1.
5l 2 Tm h s tng quan gia cng sut vi cng xut trong qu khKhi xy dng bt k m hnh no th vic m hnh hot ng c tt hay khng
ph thuc rt ln vo mi quan h u vo v u ra, bn cnh ty thuc vo
tng bi ton m ta phi la chn cc thng s u vo khc nhau. Trong hm
tng quan l mt thc o la chn thng s u vo cho m hnh.
Vi s liu ph ti v nhit hai nm 2004 - 2005 cc thng s u ra cn
xc nh l cng sut cc i v cng sut cc tiu, chng ta s xem xt mi tng
quan cng sut cc i ca mt ngy vi cc ngy trc .
t:Pmax(d), Pmin(d)\ L cng sut ph ti cao nht, thp nht trong ngy d
Pmax(d-x), Pmn(d-x): L cng sut ph ti cao nht v thp nht cch ngy trc X
ngy (x=l, 2...7, 14,21,28)
Xt cc mi tng quan gia Pmaxd vi 20 yu t nh hng khc:
1. Pmax(d), Pmax(d-l): Cng sut cc i ngy hin ti vi cng sut cc i
ngy hm trc
2. Pmax(d), Pmax(d-2): Cng sut cc i ngy hin ti vi cng sut cc i
cch hai ngy
3. ...
7. Pmax(d), Pmax(d-7): Cng sut cc i ngy hin ti vi cng sut cc i
cch by ngy(l tun)
8. Pmax(d), Pmax(d-14): Cng sut cc i ngy hin ti vi cng sut cc i
cch 14 ngy (2 tun)
56Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-----------------------
-
9. Pmax(d), Pmax(d-21): Cng sut cc i ngy hin ti vi cng sut cc i
cch 21 ngy (3 tun)
10.Pmax(d), Pmax(d-28): Cng sut cc i ngy hin ti vi cng sut cc i
cch 28 ngy (4 tun)
11 .Pmax(d), Pmn(d-l): Cng sut cc i ngy hin ti vi cng sut cc tiu
gy hm trc
12. Pmax(d), Pmn(d-2): Cng sut cc i ngy hin ti vi cng sut cc tiu
gy hm trc
17.Pmax(d), Pmax(d-7): Cng sut cc i ngy hin ti vi cng sut cc i
cch by ngy(l tun).
18.Pmax(d), Pmax(d-4): Cng sut cc i ngy hin ti vi cng sut cc i
cch 14 ngy (2 tun)
19.Pmax(d), Pmax(d-21): Cng sut cc i ngy hin ti vi cng sut cc i
cch 21 ngy (3 tun)
20.Pmax(d), Pmax(d-28): Cng sut cc i ngy hin ti vi cng sut cc i
cch 28 ngy (4 tun)
5.13 Mt s kt qu thu c sau khi phn tch tng quan
Hnh 5.1 Hnh 5.2
57Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
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Hnh 5.1: th ph thuc ca Pmax(d) vo Pmax(d-l) vi h s tng quan r=0,81
Hnh 5.2: th ph thuc ca Pmax(d) vo Pmax(d-7) vi h s tng quan r=0,61
Tng t vi Pmin: Ta cng xt nh hng ca 20 yu t n Pmn kt qu xt tng quan c trnh by hnh bn di.
MW MW
Hnh 5.3 Hnh 5.4
Hnh 5.3: th ph thuc ca Pmin(d) vo Pmin(d-l) vi h s tng quan r=0,93
Hnh 5.4: th ph thuc ca Pmin(d) vo Pmin(d-7) vi h s tng quan r=0,81
Bng 5.1 Kt qu phn tch tng quan gia Pmax v 20 yu t
gy Pmaxd, Pmaxd-1 Pmaxd, Pmaxd-2 Pmaxd, Pmaxd-3 Pmaxd, Pmaxd-4
r 0,8058 0,7461 0,7023 0,6723
gy Pmaxd, Pmaxd-5 Pmaxd, Pmaxd-6 Pmaxd, Pmaxd-7 Pmaxd, Pmaxd-14
r 0,652 0,6166 0,6149 0,5164
gy Pmaxd, Pmaxd-21 Pmaxd,Pmaxd-28 Pmaxd, Pmind-1 Pmaxd, Pmind-2
r 0,5108 0,4243 0,7776 0,7337
gy Pmaxd, Pmind-3 Pmaxd, Pmind-4 Pmaxd, Pmind-5 Pmaxd, Pmind-6
r 0,7078 0,6704 0,6496 0,6322
gy Pmaxd, Pmind-7 Pmaxd, Pmind-14 Pmaxd, Pmind-21 Pmaxd,Pmind-2 8
r 0,6226 0,5422 0,526 0,458
Bng 5.2 Kt qu phn tch tng quan gia Pmin v 20 yu t
gy Pmind, Pmind-1 Pmind, Pmind-2 Pmind, Pmind-3 Pmind, Pmind-4
r 0,9312 0,8966 0,8678 0,8495
58Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-
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gy Pmind, Pmind-5 Pmind, Pmind-6 Pmind, Pmind-7 Pmind, Pmind-14
r 0,8314 0,8183 0,8090 0,7569
gy Pmind, Pmind-21 Pmind,Pmind-28 Pmin, Pmax-1 Pmind, Pmaxd-2
r 0,7495 0,6689 0,7492 0,7122
gy Pmind, Pmaxd-3 Pmind, Pmaxd-4 Pmind, Pmaxd-5 Pmind, Pmaxd-6
r 0,6817 0,668 0,6536 0,6407
gy Pmind, Pmaxd-7 Pmind, Pmaxd-14 Pmind, Pmaxd-21 Pmind,Pmaxd-28
r 0,6321 0,5918 0,598 0,5491
.9
0.8
0.7
.6
0.5
0.4
.3
0.2
0.1
0 1 2 3 4 5 6 7 8 9 10 11Pmax-1 Pmax-2 Pmax-3 Pmax-4 Pmax-5 Pmax-6 Pmax-7 Pmax-14 Pmax-21 Pmax-28
Hnh 5.5 th tng quan gia Pmax v cc Pmax trong qu kh
hn thy h s tng quan ca Pmax v cc ngy trong qu kh cng xa
cng gim, hng th h s tng quan gim nhanh Pmax(d-14), Pmax(d-21),
Pmax(d-28). Do c th chn Pmax(d-l) n Pmax(d-7) lm thng s u vo
d bo Pmaxd.
th biu din mi quan h Pmax v cc yu t u vo-------- 1--------1--------1--------1--------1-------- 1--------1--------1--------1
a a
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1 2 3 4 5 6 7 8 9 10 11
Pmin-1 Pmin-2 Pmin-3 Pmin-4 Pmin-5 Pmin-6 Pmin-7 Pmin-14 Pmin-21 Pmin-28
Hnh 5.6 th tng quan gia Pmax v cc Pmin trong qu kh
H s tng quan ca Pmax v cc Pmn trong qu kh cng xa cng gim,
hng th h s tng quan gim nhanh Pmn(d-14), Pmn(d-21), Pmin(d-28).
Do c th chn Pmin(d-l) n Pmn(d-7) lm thng s u vo d bo
Pmaxd.
1
.9
0.8
0.7
0.6
0.5
0.4
0 3
0.2
0.1
0 1 2 3 4 5 6 7 8 3 10 11
Pmin-1 Pmin-2 Pmin-3 Pmin-4 Pmin-5 Pmin-6 Pmin-7 Pmin-14 Pmin-21 Pmin-28
Hnh 5.7 th tng quan gia Pmn v cc Pmin trong qu kh
60Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-----------------------
th biu din mi quan h Pmin v cc yu t u vo~r~
I r ~--------------1-------------- 1--------------r
-
0 8 1------------------1------------------1----------------- 1------------------1----------------- 1------------------1------------------1----------------- 1------------------1----------------- r
9
0 5 -
0 4 -
0.3 -
0.2 -
0 1 -
0 1 2 3 4 5 6 7 0 9 10 11
Pmax-1 Prnax-2 Pmax-3 Pmax-4 Pmax-5 Prnax-6 Pmax-7 Ptnax-14 Pmax-21 Pmax-20
Hnh 5.8 th tng quan gia Pmn v cc Pmax ong qu kh
Tng t nh xt cc u vo d bo cho Pmax, chn thng s u vo cho
Pmin cng tng t nh vy.
Nhn xt: Qu vic tm h s tng quan ph ti cc i v cc tiu ca ngy
hin ti v cc ngy trc c th nhn ra rng h s tng quan s theo chu