Speed Sensorless Direct Torque Control of Brushless Doubly-Fed Generator for Wind Power Generation

Based on speed sensorless technology, a direct torque control strategy suitable for variable speed constant frequency brushless doubly-fed wind power generator is proposed in this paper. An advanced flux observation method is presented to avoid flux drift phenomenon. Furthermore, the synchronous rotating speed and slip speed are estimated by observing the rotor flux to obtain the generator speed, and further to implement speed sensorless control. Simulations show that the proposed observation method can enhance flux and speed observation precision, and greatly improve low speed performance of speed sensorless direct torque control system, which is helpful to the direct-drive type development of brushless doubly-fed wind power generation system and to the utilization of low speed wind power.