Instantaneous current-sharing control scheme of multi-inverter modules in parallel based on virtual circulating impedance

Parallel multi-inverter modules are characterised by expandable output power and improved reliability. A current-sharing control scheme has to be employed to achieve equally load current sharing of paralleled inverters. At present, circulating active/reactive power are applied to control the voltage in some current-sharing control schemes; however, the size and weight are increased owing to the extra inductor. In this study, the concept of virtual circulating impedance is proposed and introduced into current-sharing control scheme to achieve ideal performance without increasing size and weight in multi-inverter modules in parallel. The mathematical model of circulating impedance is established and the relationship between the phase and the amplitude of circulating current, the phase of inverter module's output reference voltage is decoupled. Simulation and experimental inverter modules are built and operated in parallel system. The results of simulation and experiment verify that the current-sharing control scheme based on circulating impedance is available and efficient.