Maximum efficiency of a Wind Energy Conversion system with a PM Synchronous Generator

In this paper, a control strategy for a Wind Energy Conversion System (WECS) is introduced aiming in both maximum power operation of the wind turbine and minimum power loss of the electrical generator. The conventional configuration of ac-dc-ac topology for Permanent Magnet Synchronous Generator (PMSG) is used. The PMSG is driven by a Pulse-Width Modulation (PWM) rectifier, an intermediate delink circuit and a PWM inverter for the connection to the utility grid. Field oriented control technique is applied at the rectifier for the separate control of d- and q-axis stator current components of the PMSG. For this purpose, two search controllers are utilized. One search controller regulates the q-axis stator current and through this the generator speed. Thus, the reference speed of the generator is dynamically modified according to the wind speed in order to maintain the wind turbine at its maximum power operating point. The second search controller regulates the d-axis current component for controlling the excitation flux of the generator, and therefore for minimizing the electrical loss of the PMSG. For the implementation of the above control method, the knowledge of neither the wind turbine parameters nor the generator loss model is required. The proposed control method has been simulated in Matlab/Simulink software, and several simulation results are presented in order to validate its effectiveness and the operational improvements.