The Research On Direct Torque Control Of Doubly Fed Induction Generator

With the exhaustion of traditional fossil fuels such as coal and oil, and the environmental pollution problem is becoming increasingly serious. Renewable clean energy has become an important support for sustainable development. As one of the renewable clean energy, wind energy has great potential for development in the field of power generation technology. The share market of the permanent magnet direct-drive generator and doubly-fed induction generator(DFIG) is growing in the current wind turbine type, and the DFIG occupy the majority market of the new large wind turbines. But capacity is small of DFIG excitation converter that control ability has been weaken of the doubly-fed wind turbine. So the stability of the converter control strategy has occupied an important position. Now, the vector control technology has become mature at home and abroad in the application of the DFIG, but the control response too slow and the control process is relatively complex. Experts hope that through more simple control strategy, to realize the operation control of the DFIG. Of course, the first choice is the direct torque control(DTC) that have study more in the present. The main idea of DTC is to direct control the generator electromagnetic torque and flux linkage. The control process is more simple and response is more rapidly. But there are still deficiency existing of DTC technology, and the research is not mature yet. The article aim to research the direct torque control technology that be useful for DFIG of the future control technology development and application.Firstly, the current research status and development trend of wind power generation is Summarized comprehensively. The mainly control method of doubly fed wind power generator is introduced. And the current present research situation and the deficiencies of direct torque control technology is summarized in the domestic and foreign.Secondly, through understanding of the basic principle knowledge of aerodynamics related and structure wind generator, the mathematical model of wind generator is established under the three-phase static coordinate system and two-phase rotating coordinate system.Again, the traditional direct torque control principle of doubly fed wind power generator is analyzed deeply. After the summary of the existed problems in the direct torque control system, a novel method of direct torque control of rotor voltage magnitude and phase angle estimation is proposed that the reference of rotor voltage and rotor voltage phase angle is estimated by the flux and the torque error, then the PWM/SVPWM modulated signal is produced, and used for the rotor side inverter to realize the control of the rotor side of the generator operation.Finally, in the Simulink, traditional and new type of DTC method are compared, the simulation results show that the control effect is still not ideal of the new direct torque control system in low speed running, but when the wind speed changes of the above rated wind speed and near the rated wind speed, and under the condition of power grid failure, adjust time have reduced of the wind power system; and have avoid the converter switching frequency is not fixed when compared traditional DTC, achieved ideal Control effect for the converter. The research has a certain guiding significance to the actual the control system of doubly-fed asynchronous wind turbine design and debugging.