Simultaneous voltage and current harmonics compensation in islanded/grid-connected microgrids using virtual impedance concept

Power quality improvement is an essential aspect of microgrids. In this paper, a cascaded voltage and current control scheme using the virtual impedance concept is proposed, which is capable of simultaneous quality improvement of local load voltage and grid-injected current. Also, the proposed control scheme is capable of working in both islanded and grid-connected modes with the ability of seamless transfer between them. In the proposed control scheme, the current controller is designed using H∞ repetitive control and voltage controller is designed based on a novel control technique that uses the inherent virtual impedance of the inverter. The proposed control scheme causes a clean current injection to the grid and enhances the quality of local load voltage even in case of nonlinear local load connection and nonsinusoidal grid voltage condition. The effectiveness of the proposed control scheme and its superiority over other methods are proven through several real-time case study simulations using SIMULINK Real-Time in MATLAB software.