1 yang1 firuz zare2 and frede 1 - aalborg universitet · presenter: pooya davari 26 aug 2015 pooya...

PRESENTER: POOYADAVARI26AUG2015

WWW.NHTD.ET.AAU.DK

Pooya Davari 1, Yongheng Yang1, Firuz Zare2 and Frede Blaabjerg1

1DepartmentofEnergyTechnology,AalborgUniversity,Denmark2DanfossPowerElectronicsA/S,Grasten,Denmark

AMulti‐PulsePatternModulationSchemeforHarmonicMitigationinThree‐Phase

Multi‐MotorDrives

2

Introduction(StandardThree‐PhaseMotorDriveSystems)

ElectronicInductor

ProposedMethod(Multi‐driveconfiguration)

ExperimentalResults

Conclusion

Outline

3Introduction

Estimatedshareofelectricityconsumptionforallelectricmotors

From power quality point of view the main concern with ASD systems is the generation ofcurrent harmonics which may lead to high losses and stability issues in the grid

Developing energy efficientmotor drive systems holds agreat potential for reducing theworldwide energy consumption.

Introducing Adjustable SpeedDrive (ASD) based on powerelectronics technology leads tomore energy efficient motordrive systems.

4Introduction

StandardThree‐PhaseMotorDriveSystem

Diode rectifier: simple, cost effective and efficient solution. But it imposes high level of inputcurrent harmonics.

AC or DC side passive filtering (inductor): simple and effective to some extent. But they arebulky, costly, causes resonance, worsen system dynamic, and etc.

Active harmonic mitigation solutions have been introduced to improve the input current quality.But they are complex, costly and reduce system efficiency.

5Introduction

Three‐PhaseDiodeRectifierwithDCSidePassiveFiltering

Vph,rms = 3 X 220 Vfg = 50 HzPo = 3 kWCdc = 470 µF

20 mH4 mH

λ

LdcDiode Rectifier

Cdc

Non-sinusoidal current

iabc

ZgGrid

vabc

Vo

RL

Vr

6Introduction

Three‐PhaseDiodeRectifierwithDCSidePassiveFiltering

Vph,rms = 3 X 220 Vfg = 50 HzPo = 0.75 kW – 3 kWLdc = 8mHCdc = 470 µF

3 kW

1.5 kW

LdcDiode Rectifier

Cdc

Non-sinusoidal current

iabc

ZgGrid

vabc

Vo

RL

Vr

Theeffectiveimpedancereducesproportionallywiththereductionintheloadcurrent.

λ

7ElectronicInductor

BasicConcept

Emulatingthebehaviorofanidealinfiniteinductor

λ ≈0.95THDi ≈30%

THDi andPowerFactor(λ)independentoftheloadprofile.

4cos 30

8Multi‐Drive

Improvingtheinputcurrentqualitybycombiningthenonlinearloads

In many applications it is a common practice to employ parallel connected drive units. In thissituation the application demand is met using multiple modestly sized motor units ratherthan one single large unit.

The undesirable nonlinearity of theconventional AC‐DC conversion stagebecomes significant, when a largenumber of industrial converters andASD systems are connected to thePoint of Common Coupling (PCC).

The feasibility of this solution isattained only when suitable andaccessible communication amongthe nonlinear units can beperformed. Single‐Drive Multi‐Drive

9Multi‐Drive(Proposedmethod)

BasicConcept

Emulatingthebehaviorofanidealinfiniteinductor

THDi andPowerFactor(λ)independentoftheloadprofile.

2 2

s n ni n a b

0 0

0 0

2 2sin sin

3

2 2cos cos

3

dcn

dcn

I na n n

n

I nb n n

n

4cos

6dc

d

I ni n

n

22

g n d ni n a i n b

10

Squarewavecurrent

0 10 20 30 40 50 60

Firing angle αf (°)

0

5

15

10

20

25

30

35

THDig

5th

7th

11th13th

Lowest THDig = 15.85%

Multi‐Drive(Proposedmethod)

11

Pulsepatterncurrentmodulation(extendingthesystemflexibility)

Single‐Drive(Proposedmethod)

12

HarmonicElimination(αf=0o)

Addingorsubtractingphase‐displacedcurrentlevels

Single‐Drive(Proposedmethod)

4cos

4cos

4cos

4cos 30 cos cos

+

+

=

Pulsepatterncurrentmodulation

13

HarmonicElimination(αf≠0o)

Addingorsubtractingphase‐displacedcurrentlevels

Single‐Drive(Proposedmethod)

22

01

22

01

1

1

2 2sin sin 2

3

2 2cos cos 2

3

( 1)

( 1)

dcn j j

j

dcn j j

j

j

j

I na n n n

n

I nb n n n

n

10 0

10 0

2 2sin sin

3

2 2cos cos

3

dcn

dcn

I na n n

n

I nb n n

n

2 2

s n n n ni n a a b b

+

+

=

Pulsepatterncurrentmodulation

14Multi‐Drive(Proposedmethod)

Although an appropriate adjustmentof the phase angle of the SCR unit cancontribute to an improvement of thecurrent quality, a new currentmodulation technique is applied toeach DC‐DC converter in order tofurther improve the current quality.

Pulsepatterncurrentmodulation

15Multi‐Drive(Proposedmethod)

FFTequations

2 2

g n n d n ni n a a i n b b

22

01

22

01

1

1

2 2sin sin 2

3

2 2cos cos 2

3

( 1)

( 1)

dcn j j

j

dcn j j

j

j

j

I na n n n

n

I nb n n n

n

1 2 1 2 1

4 2cos cos cos

6 3d dc dc dc

n ni n I I n I n

n

0

0

1

n n

d n n

g ai

a a

i n b b

M

HarmonicElimination

0 0

0 0

2 2sin sin

3

2 2cos cos

3

dcn

dcn

I na n n

n

I nb n n

n

Pulsepatterncurrentmodulation

16Multi‐Drive(Proposedmethod)

OptimumHarmonicSolution

1 1(1)

(n)

(1)

a g

g

n n

g

Obj M i L

iObj L

i

2obj n n nF w Obj L

0 1 2 0 3m

where n = 6k±1 with k being 1, 2, 3, ….

Insteadoffullynullifyingthedistortions,theharmonicscouldbereducedtoacceptablelevelsbyaddingsuitableconstraints(Ln).

Constraint

ObjectiveFunction WeightingFactor

Here, Fobj is formed based on a squared error with more flexibility by adding constant weightvalues (wn) to each squared error function

17

SystemStructure

Employingconventionalboostconverter

Employingfastcurrentcontrolmethod

Boostingtheoutputvoltage

Multi‐Drive(Proposedmethod)

18Multi‐Drive(Proposedmethod)

AdjustableSwitchingFrequency

,

(1 ) 1 1whereosw sw

L pk pk sw on off

V D Df f

L I T T T

2

, ,

(1 )

(1 )where

osw

ripple o

L pk pk L pk pkripple

L o

V D Df

Lk I

I I Dk

I I

Independentoftheloadprofile

Lowswitchingfrequencyathighpowerandhighswitchingfrequencyatlowpower

19

ImplementedSetup

Multi‐Drive(Proposedmethod)

B6

SCR

Symbol PARAMETER Valuevg,abc Grid phase voltage 220 Vrmsfg Grid frequency 50 HzZg (Lg, Rg) Grid impedance 0.1 mH, 0.01 ΩLdc DC link inductor 2 mHCdc DC link capacitor 470 µFVo Output voltage 700 VdcKp, Ki PI controller (Boost converter) 0.01, 0.1Kf, ts, ξ PLL parameters 0.8, 0.2 s, 1.41HB Hysteresis Band 2APo_total Total output power ≈5.5 kW

Parameters of the multi-rectifier systemLs

Cdc RL1

Vos*

vos

PI

iLs

iLsums

iLs*

Ld

Cdc RL2

Vod*

vod

PI

iLd

iLdumd

iLd*

is

id

ig,abc

PLL1 Firing Driverα

vab

PCC

GridZg

ωt

Modulation Signal

ωtα

Modulation Signal ωt

vrec_s

vrec_d

vab

ωtPLL2

20ExperimentalResults

Harmonic Mitigation Strategy

Harmonic Distribution and THDi (%)

ia (5)/ ia (1) ia(7)/ ia (1) ia(11)/ ia (1) ia (13)/ ia (1) THDi

Square wave (αf = 36o) 2.4 9.3 9.6 4.3 16

Conventional method (square wave αf = 0o) 20.8 13.1 8.8 7 29

Flatcurrent(αf=36o)

5 X 36o = 180o

Vo = 700 Vdc

Ld = Ls = 2mH

21ExperimentalResults

Harmonic Mitigation Strategy

Harmonic Distribution and THDi (%)

ia (5)/ ia (1) ia(7)/ ia (1) ia(11)/ ia (1) ia (13)/ ia (1) THDi

Optimized I 1.7 0.4 1.9 6 11.4

Conventional method (square wave αf = 0o) 20.8 13.1 8.8 7 29

Ls

Cdc RL1

Vos*

vos

PI

iLs

iLsums

iLs*

Ld

Cdc RL2

Vod*

vod

PI

iLd

iLdumd

iLd*

is

id

ig,abc

PLL1 Firing Driverα

vab

PCC

GridZg

ωt

Modulation Signal

ωtα

Modulation Signal ωt

vrec_s

vrec_d

vab

ωtPLL2

Optimizedforloworderharmonics(5th,7th and11th)+THDi <12%

Diode Rectifier SCR

Idc1 Idc2 α1o Idc1 Idc2 α1

o αfo

0.4 0.22 50 0.4 0.22 50 36

Vo = 700 Vdc

Ld = Ls = 2mH

22ExperimentalResults

Harmonic Mitigation Strategy

Harmonic Distribution and THDi (%)

ia (5)/ ia (1) ia(7)/ ia (1) ia(11)/ ia (1) ia (13)/ ia (1) THDi

Optimized II 1.6 0.92 2.9 3 10

Conventional method (square wave αf = 0o) 20.8 13.1 8.8 7 29

Ls

Cdc RL1

Vos*

vos

PI

iLs

iLsums

iLs*

Ld

Cdc RL2

Vod*

vod

PI

iLd

iLdumd

iLd*

is

id

ig,abc

PLL1 Firing Driverα

vab

PCC

GridZg

ωt

Modulation Signal

ωtα

Modulation Signal ωt

vrec_s

vrec_d

vab

ωtPLL2

OptimizedforminimumTHDi

Diode Rectifier SCR

Idc1 Idc2 α1o Idc1 Idc2 α1

o αfo

0.41 0.2 50 0.41 0.2 49.9 38.7

Vo = 700 Vdc

Ld = Ls = 2mH

23Conclusion

Newharmoniceliminationapproachbycombiningdifferentnon‐linearloads.ByadjustingphaseangleofSCRunits.

_

_

cos( ) 1o df

o s

PP

Applying anovelcurrentmodulationschemetofurtherimprovethecurrentquality.

As long as the following equation holds true, therectifiers will draw equal amount of current form thegrid; otherwise it should be reflected in theoptimization process.

THDi isindependentoftheloadprofile

24

ThankYou