The inverter changes the DC electricity generated by solar modules into pure sine wave current which has same frequency and phases with the national grid. Part of the electricity will power local loads and the rest will be sent to national grid.
General Principle:

1. The general principle is to keep the basic frame of the original circuit, we should embed the solar power system into the original circuit with a low voltage distribution cabinet. 
2. Considering the security and reliability of this grid-connected system ,we should add DC distribution cabinet at the input port of inverter. 
3. The output of grid-connected inverter is three-phase four-wire system. 

System Configuration：

1. PV array 
2. DC-AC inverters 
3. Step-up equipments 
4. Controlling &Testing System 
5. Ancillary facilities