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In PV grid-connected applications, a grid-connected converter is usually used to connect with the grid to realize dc/ac conversion and power flow control. How to improve the quality of grid-connected current of power equipment so that the harmonic content injected into the grid is as little as possible has become a hot research topic in the field of PV grid-connected applications. By analyzing the causes of grid-connected harmonic currents during the grid-connection process, a two-segment high-performance grid-connected inverter topology is proposed. This structure makes the main inverter basically equal to the grid voltage through the simplest closed-loop control. Since the voltage sensitivity of the auxiliary inverter is low, utilizing the auxiliary inverter for the compensation of grid-connected voltage and grid-connected control of power flow will lead to an improvement in the quality of grid-connected current. A 3.3 kW grid-connected inverter system prototype is fabricated and tested, and the experimental results verify the stability and effectiveness of the theoretical analysis and the proposed control scheme.
Liu et al. (Tue,) studied this question.