Modeling and control strategy for direct-drive wind power generation without grid voltage sensors

A wind turbine is directly connected to a generator in the direct-drive wind power generation system to improve efficiency and reliability. The topology of back-back PWM was adopted. The indirect torque vector control was used for machine-side converters, which achieved the maximum wind power tracking by adjusting the speed of permanent magnet synchronous generator. In order to improve reliability and to resist grid voltage fluctuation, and to further reduce the cost for grid-connected inverters, a new method was proposed based on phase lock loop (PLL) and virtual grid flux without grid voltage sensors, which was applied in the direct-drive wind power generation system. The simulated results show that the control strategy realizes the maximum wind power tracking and the unity power factor, which verifies the feasibility and correctness for the control strategy.