Performance Optimization Of Low-speed Permanent Magnet Direct Drive Wind Turbine Based On Direct Torque Control

With energy crisis become increasingly serious, new energy development and utilization should take action immediately. As a green inexhaustible energy wind power is one of the most promising new energy in future. To use the wind power effectively wind turbine should be accurately designed with control system needed. Wind power generation system can be divided into constant speed constant frequency generating system and variable speed constant frequency generation system. Early wind power systems are mainly constant speed constant frequency system with simple design and control system. With the development of technology, especially the rapid development of power electronics technology, wind power systems evolved into VSCF system, the wind turbine speed can track the wind to make optimal use of wind energy. Variable speed constant frequency wind power systems have many different kinds of configuration. Different generators equipped with the appropriate power electronic devices can compose of a wide variety of different characteristics of the wind power generation system. A permanent magnet synchronous generator with corresponding inverter can be composed of direct-drive permanent magnet synchronous wind power generation system. In the case below the rated wind speed, direct-drive permanent magnet synchronous control of wind power generation system is mainly reflected in the speed control of the generator. In this paper, the content of wind turbine speed control is mainly shown below:Firstly, it introduces the research background and current state of development of wind power industry in this paper. Analyze several commonly used wind power systems and their characteristics. Among the wind power system control system wind turbine speed control strategies are briefly introduced and analyzed below the rated wind speed situation.Secondly, it introduces the composition of the direct-drive permanent magnet synchronous wind power generation system. And important parts of the wind power generation system are analyzed in detail with the establishment of a mathematical model. The mathematical model of permanent magnet synchronous generators is analyzed in detailed. First make its model in the stationary 3-phase coordinate and then simplify mathematical model with coordinate transform for better control. The maximum power point tracking strategies are further described in the end.Then, the basic principles of the basic direct torque control and its concrete application in permanent magnet synchronous generator were introduced. The simulation result shows that the basic direct torque control had problems with torque ripple and other issues. To solve these problems space vector modulation(SVPWM) method id used to optimize the direct torque control system. The simulation results show that the torque ripple has been significantly improved, while the direct torque control system maintains rapid response characteristics. And finally for the system parameters change during operation the stator flux observer is designed based on extended Kalman filter making the system for better anti-interference ability and robustness. The simulation results show that the optimized direct torque control system can track rapidly changing wind speed and maintain good control performance.