An Improved Current Controller for Grid Connected Voltage Source Converter in Microgrid Applications

This paper proposes an improved control scheme for grid interactive voltage source converter (VSC) feeding nonlinear and unbalanced loads connected at the point of common coupling (PCC). A gain scheduling multiresonating controller is proposed to cope with step changes in the reference power commands. The gain scheduling laws are presented under different conditions of reference and load powers. A variable window Fourier transform (VWFT) is employed to compute the average grid power under grid frequency variation and instantaneous symmetrical components theory (ISCT) is used for generation of VSC reference currents. This scheme is also used to facilitate the power flow control along with additional power quality compensation features under distorted grid conditions. The proposed control scheme provides good compensation and tracking performance under step changes in the reference power, grid frequency, and load disturbances. The effectiveness of the proposed control scheme is tested using MATLAB/Simulink simulations and is validated experimentally on a laboratory prototype.