Efficient Parallel Control Scheme of Single Phase Inverters

In order to parallel several single phase inverters to increase power capacity and system reliability, several control schemes are proposed: a parallel control scheme, a voltage control scheme and a load sharing control scheme. The parallel control technique is based on preemptive priority, which makes no absolute master or slave inverter into reality. In order to ensure N+1 redundant structure, synchronization signal generating mechanism, a parallel digital bus and a no-conflicted protocol on the bus also are introduced. In order to control voltage, the voltage control scheme employs a local feedback controller. To implement load sharing, the load sharing control scheme introduces an improved droop method to droop voltage and frequency. The analysis of the proposed method and design procedure are provided. Based on the simulation and experiment results, it shows that the proposed scheme can implement load sharing effectively. The experimental results with different type loads show that the output current error is less than 1% rating current for each inverter.