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

Parallel operation of three-phase power-factor-corrected (PFC) rectifiers is a critical issue for high-power applications, since it extends the power range to a much higher level and allows modular design. The technical challenges are current sharing and circulating current control among the modules. This paper studies these phenomena within two paralleled rectifiers and proposes a new current-sharing method based on One-Cycle Control (OCC) with vector operation and bipolar operation. With some minor additions to the original OCC circuit and a simple add-on communication path among the individual modules, the input current is shared and the circulating current is limited, while the OCC advantages, such as constant switching frequency, no multipliers, and simple circuitry, are preserved. Two OCC PFC rectifiers of 2.5 kW each were built and tied together using the proposed parallel operation method. Experiments have demonstrated the simplicity and the effectiveness of this method.