The speed control of a direct-drive PMSG-based wind energy conversion system

In the development and application of all kinds of the renewable energy, wind energy becomes one of the most widely used energy and grows very fast. Direct-driven configuration based on permanent-magnet synchronous generator (PMSG) is an attractive choice for wind energy conversion systems (WECS) which has advantages of the gearbox elimination, no additional excitation equipment and low maintenance requirements. In this paper, a two-mass model is applied for the drive train to research the dynamic of the drive train. During the dynamics of the variation of wind speed, drive train oscillation will produce torque pulsation and cause operation loss because of the low inherent damping of the drive train, which reduce the lifetime of the machine. In this paper, a vector control is proposed, which is based on maximum torque per ampere (MTPA) operation. The speed oscillation will be damped by controlling the electromagnetic torque that can vary the generator speed. In addition, the stability of the WECS can be improved.