A single-switch three-phase boost rectifier to reduce the generator losses in wind energy conversion systems

Low and medium power wind energy conversion systems (WECS) are expected to be simple, low cost and reliable. They are usually implemented with fixed pitch wind turbines. In such a case, operation with variable speed for increased capture of wind energy requires a power electronics converter capable of adjusting the shaft speed. This is done by controlling the active power drawn from the generator. Permanent magnet synchronous generators (PMSG) are a good option for low power variable speed WECS since they do not require external excitation nor reactive power to operate. Typically, an ac-dc converter composed of a diode rectifier and a capacitive filter, connected to a voltage source inverter is used as an interface to a grid or to a load. The highly distorted input currents of the diode rectifier with capacitive filters produce additional power losses in the generator that can reduce its lifetime. This paper discusses the use of a single-switch three-phase boost rectifier in the front end of the power electronic interface. It provides means for regulating the shaft speed by duty cycle variation while reducing the generator losses when compared to the standard diode and capacitive filter scheme. Simulation and experimental results show the effectiveness of the proposed scheme for reducing the generator copper and core losses and also the internal temperature.