The zero-sequence circulating currents between parallel three-phase inverters with three-pole transformers and reactors

It is well known that a zero-sequence circulating current could exist in parallel three-phase converters with common DC bus. However, this conclusion is normally drawn out while the magnetic coupling between phases being neglected. In fact, for the cost and size, the cores of reactors and transformers that used in three-phase inverters are normally three poles. The magnet couple between three poles makes the zero-sequence circulating currents change significantly from that of three-phase inverters with three single-phase reactors and three single-phase transformers. This paper established the instantaneous zero-sequence model of three-phase inverters with three-pole reactors and transformers. The analyses based on this model indicate that the three-pole reactors and transformers have great influence on the zero-sequence circulating currents. The simulations and experiments validated the above conclusion.