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 th