Power Electronics Reliability Comparison of Grid Connected Small Wind Energy Conversion Systems

Abstract

This work presents a power electronics reliability comparison of the power conditioning system for both the Permanent Magnet Generator (PMG) and Wound Rotor Induction Generator (WRIG)-based small Wind Energy Conversion Systems (WECS). The power conditioning system for grid connection of the PMG-based system requires a rectifier, boost converter and a grid-tie inverter, while the WRIG-based system employs a rectifier, a switch and an external resistor in the rotor side with the stator directly connected to the grid. Reliability of the power conditioning system is analyzed for the worst case scenario of maximum conversion losses at a predetermined wind speed. The analysis reveals that the Mean Time Between Failures (MTBF) of the power conditioning system of a WRIG-based small wind turbine is much higher than the MTBF of the power conditioning system of a PMG-based small wind turbine. The investigation is extended to identify the least reliable component within the power conditioning system for both systems. It is shown that the inverter has the dominant effect on the system reliability for the PMG-based system, while the rectifier is the least reliable for the WRIG-based system. This research indicates that the WRIG-based small wind turbine with a simple power conditioning system is a much better option for small wind energy conversion system.