Modeling, analysis, and implementation of real time network controlled parallel multi-inverter systems

In this paper, a real time network controlled multi-inverter parallel system by using a newly published network protocol Ethercat is discussed. Compared to the traditional communication method, the advantage of real time networked control is gained from providing a high-quality synchronization signal, high speed communication rate (100Mbps), real-time central control, and signal immunity to analogue disturbance induced by long distance communication. Delay effect introduced by networked control is investigated in detail and controller design process is presented. Besides, a generalized model of network controlled multi-inverter parallel system is presented to facilitate current sharing controller design. The experiments validate that real time networked control has a promising future in implementing multi-inverter parallel system in either a multi-UPS system or a microgrid.