Modeling and coordinate control of circulating currents in parallel three-phase boost rectifiers

In this paper, definition of the circulating currents of multiphase paralleled converters is first presented, and the circulating-current-generating mechanism is clearly explained. Thus, based on this definition, an averaged model of the circulating current is proposed. It is seen from this model that the circulating current consists of not only the zero-sequence but also the nonzero-sequence components. The governing differential equation also shows explicitly the relation between the circulating currents and the affecting factors such as different pulse width-modulation strategies. With this understanding, a simple coordinate control is then presented to reduce the circulating current. The phenomenon of the intrinsic circulating current is also explained. Furthermore, a prototype system is constructed, and the proposed control is implemented using TMS320F2812 DSP. Both simulation and experimental results verify the validity of the proposed theory and control.