slobodan lubura, milomir Šoja, srđan lale, marko ikić
DESCRIPTION
Experimental verification of single-phase PLL with novel two-phase generator for grid-connected converters. Slobodan Lubura, Milomir Šoja, Srđan Lale, Marko Ikić The Faculty of Electrical Engineering, University East Sarajevo, East Sarajevo, Bosnia and Herzegovina. Introduction. - PowerPoint PPT PresentationTRANSCRIPT
Projekt „ESSNBS“
Niš, November 4th – 7th, 2012 - 1 -
DAAD
Experimental verification of single-phase Experimental verification of single-phase PLL with novel two-phase generator for PLL with novel two-phase generator for
grid-connected convertersgrid-connected converters
Slobodan Lubura, Milomir Šoja, Srđan Lale, Marko Ikić
The Faculty of Electrical Engineering, University East Sarajevo, East Sarajevo, Bosnia and Herzegovina
Projekt „ESSNBS“
Niš, November 4th – 7th, 2012 - 2 -
DAAD
Introduction
Two-phase generator
Vgrid_measured
Vα
Vβ
Park’s transformation
Vq_est
Vgrid_magnitude_est
0
PI
ωnom
ωest
s
1 θest
The general structure of single-phase PLL based on SRF theory
Projekt „ESSNBS“
Niš, November 4th – 7th, 2012 - 3 -
DAAD
Novel two-phase generator with noise and DC offset rejection
2
Vbeta
1
Valfa
Product3
Product1
Product
1s
Integrator2
1s
Integrator1
1s
Integrator
ki
Gain1 0
Constant
Add
2
w
1
Vin
The new two-phase generator with DC offset rejection realized inSimulink environment
Projekt „ESSNBS“
Niš, November 4th – 7th, 2012 - 4 -
DAAD
Novel two-phase generator with noise and DC offset rejection
• Proposed structure of novel two-phase generator can be presented with following transfer functions:
𝑊𝑚𝛼ሺ𝑠ሻ= 𝜔𝑠2𝑠3 + (𝜔+ 𝑘𝑖)𝑠2 + 𝜔2𝑠+ 𝑘𝑖𝜔2 (1)
𝑊𝑚𝛽ሺ𝑠ሻ= 𝜔2𝑠𝑠3 + (𝜔+ 𝑘𝑖)𝑠2 + 𝜔2𝑠+ 𝑘𝑖𝜔2 . (2)
• Both (1) and (2) represent transfer functions of band-pass filters.
Projekt „ESSNBS“
Niš, November 4th – 7th, 2012 - 5 -
DAAD
Experimental results of proposed PLL
3
Estimated gridamplitude
2
Estimated gridangular frequency
1
Estimatedreference current
Vin
w
Valf a
Vbeta
Two-phasegenerator
cos
TrigonometricFunction
Valf a
Vbeta
teta
Vde
Vqe
Synchronousreference system
Rate Transition
In1 Out1
PI regulator
w
Nominal gridangular frequency
w teta
Integrator with reset
Irefm
Gain5
k
Gain
100
Constant
Band-LimitedWhite Noise
AnalogInput
Analog InputHumusof t
MF624 [auto]
Block-diagram of proposed PLL topology realized in Simulink using Real Time Windows Target library
Projekt „ESSNBS“
Niš, November 4th – 7th, 2012 - 6 -
DAAD
Experimental results of proposed PLL – continuous model of PLL
4.45 4.46 4.47 4.48 4.49 4.5 4.51
-300
-200
-100
0
100
200
300
time [s]
Vin
, V
alfa
, V
beta
[V
]
Vin
ValfaVbeta
The response of two-phase generator on grid voltage with noise
Projekt „ESSNBS“
Niš, November 4th – 7th, 2012 - 7 -
DAAD
Experimental results of proposed PLL – continuous model of PLL
a) Input grid voltage with 30% DC offset and estimated grid amplitude, without control loop for DC offset rejection
b) Input grid voltage with 30% DC offset and estimated grid frequency, without control loop for DC offset rejection
4 4.05 4.1 4.15 4.2-500
0
500
time [s]
Vin
[V
]
4 4.05 4.1 4.15 4.2200
300
400
500
time [s]
Vest
[V]
4 4.05 4.1 4.15 4.2-500
0
500
time [s]
Vin
[V
]
4 4.05 4.1 4.15 4.245
50
55
time [s]
fest
[Hz]
a) b)
Projekt „ESSNBS“
Niš, November 4th – 7th, 2012 - 8 -
DAAD
Experimental results of proposed PLL – continuous model of PLL
a) Input grid voltage with 30% DC offset and estimated grid amplitude, with control loop for DC offset rejection
b) Input grid voltage with 30% DC offset and estimated grid frequency, with control loop for DC offset rejection
a) b)
4 4.05 4.1 4.15 4.2-400
-200
0
200
400
600
time [s]
Vin
[V
]
4 4.05 4.1 4.15 4.2332
334
336
338
time [s]
Vest
[V]
4 4.05 4.1 4.15 4.2-500
0
500
time [s]
Vin
[V
]
4 4.05 4.1 4.15 4.249.6
49.8
50
50.2
time [s]fe
st
[Hz]
Projekt „ESSNBS“
Niš, November 4th – 7th, 2012 - 9 -
DAAD
Experimental results of proposed PLL – continuous model of PLL
0 0.5 1 1.5 2 2.5 3 3.5 4
-400
-200
0
200
400
600
time [s]
Vest
[V]
ki=100
ki=10ki=500
0 0.5 1 1.5 2 2.5 3 3.5 420
40
60
80
time [s]
fest
[Hz]
ki=100
ki=10
ki=500
Estimated grid frequency (top) and amplitude (bottom) for ki = 10, 100 and 500 (robustness against step changes of grid frequency and amplitude)
Projekt „ESSNBS“
Niš, November 4th – 7th, 2012 - 10 -
DAAD
Experimental results of proposed PLL – continuous model of PLL
Input grid voltage with 30% DC offset and generated referencevoltage.
2 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08-400
-300
-200
-100
0
100
200
300
400
500
time [s]
Vin
, V
out
[V]
Vin
Vout
Projekt „ESSNBS“
Niš, November 4th – 7th, 2012 - 11 -
DAAD
Experimental results of proposed PLL – discrete model of PLL
• Discretization of proposed PLL was performed in two ways:1𝑠 ≈ 𝑇𝑠2 ൬
𝑧+ 1𝑧− 1൰. (3)
1𝑠 ≈ 𝑇𝑠12ቆ5+ 8𝑧−1 − 𝑧−21− 𝑧−1 ቇ. (4)
Tustin approximation
Schneider approximation
Projekt „ESSNBS“
Niš, November 4th – 7th, 2012 - 12 -
DAAD
Experimental results of proposed PLL – discrete model of PLL
0 1 2 3 4 5 6-400
-300
-200
-100
0
100
200
300
400
time [s]
Ves
t [V
]
Schneider
Tustin
Estimated grid amplitude for two discrete models of PLL(step changes of grid parameters)
Ts=50μs
Projekt „ESSNBS“
Niš, November 4th – 7th, 2012 - 13 -
DAAD
Experimental results of proposed PLL – discrete model of PLL
Estimated grid frequency for two discrete models of PLL(step changes of grid parameters)
Ts=50μs
0 1 2 3 4 5 636
38
40
42
44
46
48
50
52
54
time [s]
fest
[H
z]
Tustin
Schneider
Projekt „ESSNBS“
Niš, November 4th – 7th, 2012 - 14 -
DAAD
Conclusion
• The results show that proposed PLL (both continual and discrete) can solve important issues of presence of DC offset and noise in measured values of grid voltage.
• Proposed PLL can be used for both, grid-connected systems (e.g. Photovoltaic and Wind turbines) and power condition equipment (uninterruptible power supply (UPS), active filters) which rely on PLL based synchronization.
• The further work should be implementation of proposed PLL topology on digital platform (using dsPIC).