A comparative study of the reliability of the power electronics in grid connected small wind turbine systems

This work presents a reliability analysis of the power conditioning system (PCS) for both the permanent magnet generator (PMG) and wound rotor induction generator (WRIG)-based small wind turbine generation systems. The PCS 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 chopper and an external resistor in the rotor side with the stator directly connected to the grid. Reliability of the PCS 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 PCS of a WRIG-based small wind turbine is much higher than the MTBF of the PCS of a PMG-based small wind turbine. The investigation is extended to identify the least reliable component within the PCS 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 PCS is a much better option for small wind energy conversion system.