An Improved Control Strategy for the One Cycle Control Three-Phase PFC Rectifier under Unbalanced Source

One cycle control three-phase boost rectifier proposed in literature has many advantages. By modifying the main topology, it has capability of controlling three-phase PFCs, APFs, STATCOMs, and grid connected inverters. But under unbalanced source, it is difficult to control input currents flexibly in case of keeping constant input power, keeping balanced input currents, or keeping the input currents fully in-phase with each own voltages. In this paper, an improved control strategy which can control the input currents flexibly is presented. By selecting different current control parameters (CCP), we can get four methods under unbalanced source: (1) constant CCP method, (2) in-phase currents control method, (3) constant input power method, (4) and balanced input currents method. In the four methods, the relationships among input voltages, input power and effective power factor are analysed respectively. In a typical DSP system, the digital implementation of the proposed control strategies is described. The control block and experimental results are shown in order to verify that the improved control strategy may realize the four goals and get better performances