by ron s,y.hui and chi kwan lee - iere · energy of battery storage (es) power of battery storage...
TRANSCRIPT
bybyRon S,Y.HUI and Chi Kwan LEE
D t t f El t i l & El t i E i iDepartment of Electrical & Electronic EngineeringThe University of Hong Kong
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k d h d h llBackground & The Grand ChallengeElectric Springs & Hardware TestsSimulation Studies in Power SystemsRemarks
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The intermittent power is causing destabilization of the electric The intermittent power is causing destabilization of the electric grids, causing potential blackouts, weakening voltage and causing damage to industrial equipment.g g q p
• The Oahu-Hawaii power system collapsed in April 2013 when 17 %
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the wind power reached 17 % ! [EPRI]
Important points:1.Wind and solar power is the best way to cut CO2 emission.2.Rapid increase of Wind and Solar Power is possible, but….S p ,3.there is a urgent need to cope with stability issues.
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Existing Power Generation Future Power GenerationgCentralized Distributed
One-way power flow Bi-directional power flowOne way power flow Bi directional power flow
Existing Control Paradigm Future Control ParadigmPower Generation follows Load
DemandLoad Demand follows Power
Generation
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A power electronics device adaptive toA power electronics device adaptive to◦ fluctuating mains voltage and/or frequency
It is low cost and autonomous◦ No need for centralized control systems
It can therefore be ‘distributed” over the power grid◦ eg. Households and industrial sites to stabilize the mains voltageeg. Households and industrial sites to stabilize the mains voltage
and/or frequency in real-time.
l h h h ll ll dAlthough they are all small power devices, ◦ many “small” but distributed electric springs should provide a
collectively robust stabilizing effect.collectively robust stabilizing effect.
Hooke’s Law
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(1660)
Non-critical load power P1 follows the intermittent powerNon critical load power P1 follows the intermittent power generationMains voltage VS is regulated to its nominal valueS
Pin-
Compensator as Electric Spring vs
P1v s_reftive wer
+PWM Power
Inverter
P2voow
Load
222
Rv
Rvv
P sasin +
−=
time
( ) ( )22
ReRe ZvZvP so⎟⎟⎞
⎜⎜⎛
+⎟⎟⎞
⎜⎜⎛
=
21
21
PPPRR
in +=
( ) ( )
21
22
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ReRe
PPP
ZZ
ZZ
P
in
in
+=
⎟⎟⎠
⎜⎜⎝
+⎟⎟⎠
⎜⎜⎝
=
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Signals feedback Signals output to
Vs , Is, ωs, Ps andQs
from the grid the converter
Gate PatternGenerator
Droop Control
Vs*(nominal) eg. 220V
From P and QM
Vs_ref
VsActive and
Reactive Power
Q
σ
Magnitude and Phase angle
VsIsError
Amplifier /
M
eVs ComputationsP
gControllerCompensator
Synchronization Circuit
Load Shedding (frequency) Control / Power Oscillation Damping Control
/ Transient Stability Control
Is, ωs, Ps andQs
Vs,ωs
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Thermal loads + Lighting systems = 40% ~ 50%Thermal loads + Lighting systems 40% 50%
Water heatingRefrigeration
Lighting
Air‐conditioning
Refrigeration
Air conditioning
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El t i S i b dd d Electric-Spring-embedded power supplies
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Stabilized mains voltage
Voltage of Electric Spring
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Load demand following power generation
Hui S.Y.R., Lee C.K. and Wu F.F., “Electric Springs: A New Smart Grid Technology”, IEEE Transactions on Smart Grid, 2012 15
2500
3000
G
1500
2000
2500
wer
(W
)
Total Input Power (PG+PR)
Battery Power (Ps)
Non-critical Load Power (P1)
Bidirectional ac-dc power converter
Non-critical load R1
Criticalload R2 0
500
1000
0 600 1200 1800 2400 3000 3600 4200
Po
Energy storage
-500
0 600 1200 1800 2400 3000 3600 4200
Time (sec)
18
27
600
900
PPPPP ++esSS EE ≥
PR 0
9
18
rgy
(Wh)
0
300
600
wer
(W
)
21 PPPPP RGS ++−−=
PG
PP1 P2
-18
-9
0 600 1200 1800 2400 3000 3600 4200E
ner
-600
-300
Po
Energy of Battery Storage (Es)
Power of Battery Storage (Ps)
PS-27
Time (sec)
-900
Pgen + Prenewable = Pcritical + Pnon-critical + Pstorage + PES Distributed Storage
Lee C.K. and Hui S.Y.R., “Reduction of energy storage requirements for smart grid using electric springs”, IEEE Transactions on Smart Grid, 2013 16
Yan S., Tan S.C., et al. “Electric springs for reducing power imbalance in three‐phase power systems”, IEEE Transactions on Power Electronics, 2015 17
Case study 2:Sa‐Lo Bay, Lantau Island, Hong Kong (11kV ‐> 220V)
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The total reactive capacity required for the ESs is about 14 times less for under‐voltage
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The total reactive capacity required for the ESs is about 14 times less for under voltage condition and 30 times less for over‐voltage condition than that required by the STATCOM.
Without considering the stability of the power systems, existing grid-connected power inverters could be ‘destabilizing” the power systems.With the stability of power system in mind, our patent-pending technologies make grid-connected power inverters a “stabilizing force”connected power inverters a “stabilizing force”.Electric Springs – a New Technology to:
tame the intermittent nature of wind/solar power–tame the intermittent nature of wind/solar power–achieve the new control paradigm of having the load demand to follow thepower generationpower generation–potentially push the intermittent renewable power generation well above 20%.
With fast P and Q control, the Electric Springs is a technology with hugepotential for both voltage and frequency stabilities of power systems.
Prof. Ron S. Y. HUI, email: [email protected]
Dr Chi kwan LEE email: cklee@eee hku hk
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Dr. Chi-kwan LEE, email: [email protected]