Optimal Efficiency Control Strategy in Wind Energy Conversion System With Induction Generator

This paper presents an optimal efficiency control strategy for wind energy conversion systems (WECSs) with squirrel cage induction generators (SCIGs). The developed control scheme provides an optimal efficiency of the induction generator and maximum power extraction from the wind turbine. Thus, maximum power harvesting from the whole WECS is achieved and additionally expansion of the exploitable wind speed region toward the lower speed range is accomplished. A minimum electric loss (MEL) controller is introduced to minimize the generator electric loss and a maximum power point tracking (MPPT) controller is used to maximize the wind turbine output power. Common input to the two optimal controllers is only the generator speed, while the measurement of the wind speed is not required. The controllers determine the optimal d- and q-axis stator current components of the SCIG through optimal conditions and, therefore, fast dynamic response of the WECS is accomplished. An experimental procedure is proposed to determine the MEL and MPPT controller parameters. Therefore, neither the knowledge of SCIG loss model, nor the characteristic curves of the wind turbine are required. The effectiveness and the operational improvements of the suggested optimal control scheme have been verified experimentally.