Feedforward Control of Grid-Tied Inverters for Harmonic Elimination using MSRF PLL

Presence of harmonics in grid voltage introduces considerable harmonic distortions in the injected grid current in grid-tied inverters. In presence of harmonics, Multiple Synchronous Reference Frame PLL gives superior performance in angle estimation. However, the harmonics caused in the grid current still need to be addressed. A novel compensation scheme is proposed in this paper which modifies t he inverter output voltage in a feedforward manner. The compensation voltages are derived from the equivalent circuit model. Simulations of a grid-tied inverter operation with the proposed scheme are validated in Matlab/Simulink. The performance of the proposed approach in the presence of non-idealities in the system is also studied. Further, an improvement is proposed to the compensation approach in the form of a closed loop structure to get enhanced performance. This is validated by simulation studies.