Application of Electrical Variable Transmission in Wind Power Generation System

In the widely applied non-direct-driven wind power generation system, a gearbox is connected between the wind turbine and high-speed doubly fed induction generator so that the system can supply power with constant voltage and constant frequency as the wind turbine speed varies. However, the multilevel mechanical gearbox is rather vulnerable and poses many difficulties to maintain. Electrical variable transmission (EVT), an electrical continuous variable gearbox, is a very competitive alternative for the vulnerable constant speed-ratio mechanical gearbox. In this paper, the application of this machine in wind power generation system with its operational modes and control strategy is presented. The working principle of the EVT-based system is introduced, and the unique power conversion characteristics are investigated. A control algorithm with maximum power point tracking for the outer rotor is developed and implemented in a prototype machine. Both computer simulation and experimental results verify the working principle and the unique features of the EVT-based wind power generation system.