Parallel operation of one-cycle controlled three-phase PFC rectifiers

Parallel operation of three-phase power factor corrected (PFC) rectifiers extends the power range to a much higher level and allows modular design. However, circulating current among the modules could be a potential problem. This paper studies the circulating current phenomenon within two paralleled rectifiers and proposes a new current sharing method based on one-cycle control with vector operation and bipolar operation. With some minor addition to the original one-cycle control circuit and a simple add-on communication path among the individual modules, the circulating current is eliminated, while the OCC advantages, such as constant switching frequency, no multipliers, and simple circuitry, are preserved. Two one-cycle controlled rectifiers of 2.5 kW each were built and tied together using the proposed parallel operation method. Experiments have shown the simplicity and the effectiveness of this method.