ABSTRACT:
Now a day’s distributed generation (DG) system uses
current regulated PWM voltage-source inverters (VSI) for synchronizing the
utility grid with DG source in order to meet the following objectives: 1) To
ensure grid stability 2) active and reactive power control through voltage and
frequency control 3) power quality improvement (i.e. harmonic elimination) etc.
In this paper the comparative study between hysteresis and proportional
integral (PI) with hysteresis current controller is presented for 1-Φ grid
connected inverter system. The main advantage of hysteresis+PI current
controller is low total harmonic distortion (THD) at the point of common
coupling (PCC) at a higher band width of the hysteresis band. The studied system
is modeled and simulated in the MATLAB Simulink environment.
KEYWORDS:
1.
Hysteresis
current controller
2.
PI controller
3.
Point of common coupling (PCC)
4.
DG
5.
Utility grid
6.
THD
SOFTWARE: MATLAB/SIMULINK
BLOCK DIAGRAM:
Fig.1.
Block diagram for hysteresis current control of single-phase grid connected VSI
EXPECTED SIMULATION RESULTS:
Fig.2.
Simulation result of the hysteresis current controller for fixed band (a) grid
voltage (Vg) and grid current (Io) (b) reference current, actual current and
current error(c) switching frequency
Fig.3.
Simulation result of the hysteresis+PI current controller for fixed band (a)
grid voltage (Vg) and grid current (Io) (b) reference current, actual current
and current error(c) switching frequency
Fig.4.
Simulation result of hysteresis current controller for change in band (a) grid
current (b) switching frequency(c) current error
Fig.5.
Simulation result of hysteresis+PI current controller for change in band (a)
grid current (b) switching frequency(c) current error
Fig.6.
THD of grid current for hysteresis current controller (a) HB=1(b)HB=3(c)HB=5
Fig.7.
THD of grid current for hysteresis+PI current controller (a) HB=1(b) HB=3(c)
HB=5
CONCLUSION:
From
the study we observed that, hysteresis+PI current controller can enable to
reduce switching frequency even if the band width increased without any
significant increase in the current error. Hence it provides considerably less
THD at higher band width as compared to conventional hysteresis current
controller.
REFERENCES:
[1]
Blaabjerg, F.; Teodorescu, R.; Liserre, M.; Timbus, A.V., “Overview of Control
and Grid Synchronization for Distributed Power Generation Systems” IEEE
Transactions on Industrial Electronics,Vol.:53 , Issue:5, Page(s): 1398 –
1409, 2006
[2]
F.Blaabjerg, Zhe Chen, and S.B. Kjaer. “Power Electronics as Efficient Interface
in Dispersed Power Generation Systems”, IEEE Transactions on Power
Electronics, 19(5):1184–1194, Sept. 2004.
[3]
Ho, C.N.-M.,Cheung, V.S.P.,Chung, H.S.-H.” Constant-Frequency Hysteresis
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[4]
Rahman, M.A.; Radwan, T.S.; Osheiba, A.M.; Lashine, A.E.; “Analysis of Current
Controllers for Voltage-Source Inverter” IEEE Trans. On Industrial
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[5]
Tekwani, P.N, Kanchan, R.S., Gopakumar, K.; “Current-error spacevector- based
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