ABSTRACT:
This paper presents the control strategy for a three
phase LCL-filter type based grid connected inverter system for photovoltaic
(PV) applications. The control strategy proposed in the paper involves the
independent control of active and reactive power injected into the grid during
steady state and transient conditions. In addition to that, a comparative study
between active and passive damping configurations for LCL type filter resonance
damping is also analyzed. The control strategy implemented on a three-phase
grid connected PV inverter is studied and verified by computer simulation based
on MATLAB Simulink and the results are analyzed for effectiveness of the study.
KEYWORDS:
1.
Renewable
Energy Source (RES)
2.
LCL-Filter
3.
Proportional-Resonant
(PR) Controller
4.
Active damping
5.
Passive
damping
SOFTWARE: MATLAB/SIMULINK
SCHEMATIC DIAGRAM:
Fig.1.
Schematic diagram of grid-connected inverter system with LCL filter
CONTROL DIAGRAM:
Fig.2.
Over all control strategy of Grid-connected PWM VSI
EXPECTED SIMULATION RESULTS:
Fig.3.
Simulation results for active damping method under steady state condition (a)
grid voltage and grid Current waveforms (b) d and q-axis grid currents (c)
response of active and reactive Power (d) response of dc-link voltage (e) THD
of grid current.
Fig.4.
Simulation results for passive damping method under steady state condition (a)
grid voltage and grid Current waveforms (b) d and q-axis grid currents (c)
response of active and reactive Power (d) response of dc-link voltage (e) THD
of grid current.
Fig.5.
Simulation results for active damping method during step change in the input PV
power (a) step change in the input PV power (b) d and q-axis grid currents (c)
response of dc-link voltage (d) THD of grid current
Fig.6.
Simulation results for passive damping method during step change in the input
PV power (a) d and q-axis grid currents (b) response of dc-link voltage (c) THD
of grid current.
CONCLUSION:
The
paper discusses the control strategy for gridconnected PWM VSI with LCL-type
filter. The advantage feature of PR controller is the possibility of
implementing harmonic compensator without interfering with control dynamics,
achieving a high quality delivered current are explored. In addition, a
comparative study has been made between active and passive damping methods to
damp-out the LCL-filter resonance. From the above said discussions, it is found
that active damping method is better than passive damping method to inject
sinusoidal current into the grid with less THD. Also it ensures zero steady
state error with stable response. In addition to that, passive damping method involves
extra cost and losses due to additional circuit components. Nevertheless,
active damping method difficult to implement, but overall performance of
grid-connected PWM VSI is improved with higher efficiency
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[1]
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[3]
Bochuan Liu; Byeong-Mun Song, "Modeling and analysis of an LCL filter for
grid-connected inverters in wind power generation systems," In Proc. 2011
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[4]
Wenqiang Zhao; Guozhu Chen, "Comparison of active and passive damping
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[5]
Hoff, B.; Sulkowski, W., "Grid connected VSI with LCL filter — Models and
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