To suppress harmonics in the mains, it is necessary to connect a filter on the inverter side. This type of inverter has two types L and LCL. The LCL filter is used in this article because it has the following two advantages: ①LCL The type filter has a third-order low-pass filter characteristic. With the same filtering effect, the LCL type can be supplemented with a lower filter inductance, so that its size will be smaller and the cost will be reduced, so the LCL type inverter will be more Economic; LLCL type filter belongs to the third order system, the effect of suppressing high-frequency harmonics is better.