The centralized control parallel scheme of inverters is an earlier proposed scheme. In this scheme, the parallel control module detects the frequency and phase of the commercial power supply, and gives a synchronization signal to each inverter at the same time. When the mains power fails, the phase-locked loop circuit of each inverter ensures that the frequency and phase of the output voltage are consistent. The parallel control module also detects the load current and divides it by the number of inverters participating in parallel as the current reference command for each inverter. At the same time, each inverter detects its own output current, and calculates the error with the average current to compensate the reference voltage command and eliminate the circulating current.

The centralized control parallel scheme is simple to implement, and the current sharing effect is good, but it does not achieve true redundancy. Once the parallel controller fails, the entire system will collapse and the reliability will be greatly reduced.