Energy storage inverter (PCS) is a key device between energy storage devices and the power grid. Due to different application scenarios, the functions and technical parameters of energy storage inverters vary greatly. When selecting, attention should be paid to system voltage, power factor, peak power, conversion efficiency, switching time, etc. The selection of these parameters has a significant impact on the functionality of the energy storage system.

1、System voltage：The voltage of the energy storage system is the voltage of the battery pack and the input voltage of the energy storage inverter. Different energy storage inverters with different technologies have significant differences in system voltage. A single-phase two-stage structure energy storage inverter is around 50V, while a three-phase two-stage structure energy storage inverter is between 150V-550V. The energy storage converter with three-phase power frequency isolation transformer is between 500V-800V, and the energy storage converter without power frequency isolation transformer is between 600V-900V.

2、Switching time: There are two types of switching time for energy storage inverters. Firstly, charging and discharging switching. Large energy storage inverters should be able to quickly switch operating states, usually requiring a switching time of no more than 200ms between 90% rated power grid connected charging state and 90% rated power grid connected discharging state. Secondly, it is applied for switching between grid connected mode and off grid mode, with a switching time of no more than 100ms.

3、Power factor: When the energy storage inverter is operating normally, the power factor should be greater than 0.99. When adjusting the system parameters and power factor, the power factor range should be as wide as possible.

4、Capacity matching: The capacity configuration of the energy storage system is 1.2 times the load capacity. If the user's load reaches 100kW, it is recommended to install a 120kW energy storage inverter. If there are other off grid loads, increase the energy storage power ratio accordingly.

In summary, the selection of transformers in energy storage systems is crucial as it directly affects the normal operation of the system. It is recommended to measure the actual electrical load value on site before selection, in order to accurately select the energy storage system.