Multiloop control strategy for grid-interfaced three-phase voltage source inverter with passively damped LLCL-filter

In inverter-based distributed generation (IBDG) and similar to the conventional third order LCL filter, the high order LLCL filter is difficult to stabilize, and may cause a resonance between the inverter and the grid. Passive damping techniques were explored in literature by connecting a resistor in different locations of the LLCL filter. This paper presents the performance of the high-order LLCL-filter with RC passive damping circuit through evaluating the system stability using dual-loop control strategy that has been applied to the LCL-filter. Comparative analysis regarding PI and PR controllers used in the proposed control strategy is offered. Simulation results using Matlab are conducted, presented, and discussed.