Application of single-switch three-phase boost rectifier to the direct-drive system

Direct-drive wind power generator has been receiving increasing attention due to their inherent efficiency. In order to allow the variable speed operation of the PMSG, a conventional three-phase bridge rectifier (BR) with a bulky capacitor associated with voltage source current controlled inverter (VS-CSI) is used. This simple scheme introduces a high intensity low frequency current harmonic content into the PMSG and consequently increase the total loss in it, subsequently, decreases the power capability of the system. In this paper, in order to decrease the current harmonic of the PMSG, correct the power factor, boost the voltage and increase the capacity of the system, a single-switch three-phase Boost rectifier (PFC) which interleaved running is applied to the systems. Although each path current is DCM, the complex current is CCM. It can correct the power factor of the PMSG without increasing the system cost, decrease the current harmonic content of the PMSG, subsequently, increase the real power ability and efficiency of system. The system has simple structure and is reliable. The single-switch three-phase Boost PFC circuit has many merits, such as: constant switch frequency, few elements, low cost, simple controller and high reliability. When applying in direct-driven wind generation system, it can correct the power factor of the generator output and increase the system efficiency. Adopting carrier phase shifted modulation can implement the effect of higher equivalent switch frequency when working at the lower switch frequency, increase equivalent switch frequency by counteraction of lower harmonics, but process harmonics to high order simply, so it has good harmonic characteristic and descend the output harmonics with increasing the equipment capacity, increase the signal transmission band of the whole equipment. The validity was verified by simulation.