Design of LCL Filter for the Single-Phase Inverter in Photovoltaic Applications

The increase in demand for renewable energy sources the demand of grid-connected inverter is increasing rapidly. The grid-connected inverter must follow the IEEE 1547 standard. In the grid-connected photovoltaic system, the LCL filter is frequently used to interconnect the inverter with the utility grid. The LCL filter is designed to reduce the switching frequency ripples generated due to use of high PWM switching frequency. Compare to traditional filter L and LC filter, LCL filter pull off effective filtering effect, leads to achieve the IEEE 1547 standard. However, design the LCL filter is complex task needs many considerations takes into to account while designing the filter. This paper proposed the simple and practical design formulas of LCL filter for the photovoltaic inverter. The LCL filter undergoes problem of stability. To tackle the problem of stability either passive damping (by inserting the damping resistor) or an active damping algorithm has to use. Both the damping methods have own advantages and disadvantages. Meanwhile, the lots of literature propose the range of resonance frequency by which the LCL filter stability problem can be avoided. On the same line, the proposed design process gives the inherent stability of LCL filter design. Using the proposed design formulas LCL filter is design for the 1KW inverter of h-bridge topology with high-frequency unipolar PWM. The design is verified by performing the simulation using MATLAB/Simulink and PLECS blockset of the inverter. The simulation results show the effectiveness of the proposed design in terms of the low-value passive component and a small value of THD and inherent stability of the inverter.