According to the coupling mode, the energy storage inverter can be divided into two types: DC side coupling and AC test coupling. According to the application scenario, it can also be divided into household energy storage, industrial and commercial energy storage, power station energy storage. DC side energy storage system draws electricity from the bus, charges and discharges the battery through the DC-DC converter. The topology of AC coupling energy storage circuit and hardware topology is similar to that of photovoltaic inverter. The main difference is that the energy storage system needs bi-direction charging and discharging, so the converter needs to work in four-quadrant mode, which has higher requirements on IGBT anti-parallel diode specification. 400V,1000V,1500V battery voltage class are common seen for general ESS. Low-power (<50kW) PCS mainly use 650V and 1200V discrete solutions. While three-level module solutions are widely used in high-power ESS.