Frequency conversion control of photovoltaic grid-connected inverter based on LCL filtering

Abstract

Abstract Aiming at the problem that the filtering effect of inductor capacitance inductor (LCL) filter becomes worse when the Photovoltaic (PV) system works at low power, this paper presents a control strategy to change the switching frequency according to the instantaneous output power of the inverter. By analyzing the design method of each parameter of LCL filter, a single-stage PV grid-connected inverter structure is used to establish the frequency loop based on grid voltage-oriented vector control to determine the optimal switching frequency under the current power state. The design methods of power detector, frequency calculation and frequency hysteresis comparator are analyzed in detail. Finally, the waveforms of grid-connected current before and after frequency conversion are contrasted by MATLAB simulation to verify the feasibility and effectiveness of the inverter control strategy.