Research On The Direct-drive Permanent Magnet Wind Power Converter System Of Direct Torque Control

With the energy shortage problems emerge in an endless stream,wind power as a kind of better green energy has get the favour of people, which is distributed on the surface of the earth widely. Wind power generation technology is one of the effective utilization of wind energy method. The research of control strategy is important ways to solve how to improve the system’s working efficient quickly in the system of high power level and especially in the MW of wind power.First of all, this thesis introduced the permanent magnet direct-drive wind turbines which was based on the direct torque control(DTC) and carried on the detailed analysis and research. In view of the method of voltage integral was used to calculate the stator flux linkage typically in the traditional direct torque control. Which has the disadvantages of error accumulation and saturation and lead to inaccurate stator flux estimation and torque ripple is larger. Because using of the speed sensor reduced the system reliability and increased the system cost, etc. Therefore, the EKF observer of stator flux linkage and speed are designed by using the principle of extended kalman filter(EKF).which improved the precision of flux observation and realized the speed sensorless in direct torque control of permanent magnet synchronous generator(PMSG) at the same time. The ripples on flux linkage and torque of the direct torque control are reduced effectively.Secondly, in view of the problem that hardware sensor was often used to measure the wind speed for the maximum wind power tracking(MPPT) control in wind power system. The strategy of a permanent magnet direct-drive wind power system’s maximum power tracking control was designed without wind speed sensor in this paper. By estimate the optimal given torque with the generator speed directly and through the generator torque and stator flux linkage of permanent magnet synchronous generator direct control to complete the maximum power tracking.RT- LAB semi-physical real-time simulation software which is able to realize the seamless connection with MATLAB/Simulink could complete the modeling and simulation of the real-time control system. The control algorithm was developed on the RT- LAB that can be applied to the practice directly and reduce the development cycle and the workload of the system greatly. In this paper, according to the software development process of the RT-LAB hardware real-time simulation technology, a permanent magnet direct-drive wind power system simulation model of direct torque control is set up. At last, through a large number of simulation experiments proved that the control scheme is correctness and effectiveness.