A three-level MPPT capability rectifier for high power direct drive WECS

In this study, power factor correction rectifier is proposed for wind turbines with three phase permanent magnet synchronous generators to provide maximum energy conversion efficiency. Reference values for the rectifier are controlled by a fuzzy logic based algorithm to track maximum power point of the wind turbine which varies with turbine characteristics, wind speed, temperature, etc. The proposed maximum power point tracking algorithm removes the requirement of knowledge about the wind generator optimal power characteristics, or measurement of the wind speed, and provides variable speed operation of wind turbine. Therefore, wind energy conversion system with higher reliability, lower complexity and cost, and less mechanical stress are obtained. Maximum power point tracking algorithm and phase locked loop circuit determining the current reference values are determined, and PI regulators are used to control of the DC voltage and line currents of the rectifier. Three level neutral point clamped rectifier topology is used as main converter. Because this topology does not require isolated DC sources and power switch modules for a leg of the rectifier are commercially available, design and implementation of the neutral point clamped rectifier is simple. Simulation results show that proposed rectifier tracks the maximum power point of the wind turbine either in variable frequency and power levels. Also line currents of the rectifiers are in same phase and frequency with permanent magnet synchronous generator voltage. In addition, THD levels of the rectifier input currents and power factor are obtained as <;5% and 0.99, respectively.