Analysis of current characteristics of parallel three-phase voltage source inverters

The current characteristics of two types of parallel three-phase voltage source inverter configurations are analyzed, and the suitability of different pulse width modulation methods in the control of parallel inverters is discussed. The analysis and discussion are based on state-space models derived in this paper and presented for the parallel connection of n units. For the sake of repeatability, a systematic derivation procedure applying Luenberger´s shuffle algorithm is also presented. The main purpose of the current characteristics analysis is to highlight the major differences between the considered parallel inverter configurations. Thus, the analysis is basically a circulating current characteristics analysis. The suitability of sinusoidal PWM, space vector PWM, and 60deg discontinuous modulation in the control of parallel inverters is studied by simulations. The purpose of the simulations is also to illustrate the differences between the parallel inverter configurations in practice.