Research on Two-Stage Three-Phase Photovoltaic Grid-Connected System with MPPT

Abstract

This paper is about three-phase photovoltaic gridconnected system with MPPT, including pre-stage DC-DC and post-stage DC-AC. The pre-stage circuit selects the Boost circuit to achieve maximum power point tracking(MPPT). In order to better track the maximum power point of the PV array, a new MPPT technology is proposed, that is, the conductivity increase method + PI adjustment. The latter stage DC-AC adopts a three-phase full-bridge inverter circuit. The control method is to use a voltage-oriented vector control, converting the output currents ia, ib, and ic into id, iq through $abc/\alpha \beta/dq$ coordinate transformation. Then a 40kW photovoltaic grid-connected model was built in MATLAB. The results show that the method can accurately achieve the MPPT, and the grid-connected inverter can realize the function of stable DC voltage and unit power factor grid-connected.