Abstract:Compared with traditional L-type and LC type filters, the LCL type filter of photovoltaic grid connected inverters has better suppression ability for high-order harmonics injected into the grid under the same inductance, and the harmonic attenuation is very obvious. However, using LCL type filters as photovoltaic grid connected interfaces can easily generate resonance peaks, affecting the stability of the entire system. In view of this, this article proposes a design scheme for a photovoltaic grid connected inverter based on LCL filters. The scheme analyzes and studies the direct torque control strategy of the photovoltaic grid connected inverter. Simulation tests show that the inverter effectively suppresses the resonance problem of LCL filters and improves the control ability of photovoltaic grid connected voltage and current. The inverter requires parameters of voltage source type, 750V DC side, 380V AC side, 50kVA, LCL filtering. This design is divided into five parts: main circuit, LCL filter, control system, three-phase phase-locked loop, and simulation. The simulation results show that the total harmonic distortion rate (THD) of the grid connected current is 2.44%, which meets the industry standard of THD<5%. The peak grid connected current is 10.22V, which can meet the preset requirements.