Power quality improvement of the grid-tied hybrid AC-DC microgrids by adding the bi-directional series converter

The power quality problems of the utility voltage are transferred to the grid-tied microgrid. With the conventional organisation of a hybrid AC-DC microgrid, the controller cannot compensate the voltage of the AC bus. The paper offers the bi-directional series converter between the common DC bus and the utility to compensate the sag/swell/harmonics of the utility voltage. The controllers are designed based on the instantaneous reactive power theory and predictive control. The interfacing converter compensates the reactive power and harmonics components of the nonlinear AC load and the voltage of the DC bus along with bi-directional transmission power. The performance verification is done by simulating the typical microgrid in MATLAB/Simulink. The AC bus voltage and utility current become pure sinusoid. The results show improvement in the THD of source current and load voltage while the voltage of the DC bus is controlled at the reference voltage.