A grid-tied power factor corrector microinverter without electrolytic capacitor by the control of voltage in a DC-link for a non-linear load

A novel control strategy is proposed for a bidirectional multiport single phase two stage microinverter without electrolytic capacitor. The application of this converter is for power factor correction under non-linear grid tied load. The converter is composed of a triple active bridge series-resonant DC/DC converter cascaded with a voltage source inverter where a film capacitor is used in the DC-Link. Power decoupling is obtained due to a high ripple low frequency voltage in the DC-Link. The proposed controller has three cascaded loops to control the DC-Link average voltage, the instantaneous grid current and the point of common coupling voltage respectively. This strategy allows having a high speed steady-state response, good stability, low harmonic distortion in the grid, bidirectional power flow and low computational cost unlike other controllers. Two different cases have been tested, the first one when only the grid delivers power to the non-linear load, and the second one when the power flow is shared between the grid and any other DC source (renewable source or battery). Simulation results validate the controller functionality.