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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