研究适合低压使用的并网逆变器，直流稳压电源作为逆变器的输入，能够将400V的直流电压转换成有效值为220V，工频为50Hz的电网电压，实现并网。(A grid connected inverter suitable for low voltage operation is studied. The DC regulated power supply is used as the input of the inverter, and the DC voltage of 400V can be converted to a grid voltage of 220V and 50Hz.)