Study On The Maximum Power Point Tracking Characteristics Of Variable Speed Constant Frequency Doubly-Fed Wind Turbines

With the increasingly severe energy and environmental problems, the world vigorously develops renewable energy. Wind energy is a renewable, pollution-free green energy. With its advantages such as green environmental protection, resource-rich, easy to develop, cost-effective, wind energy has been recognized the world's fastest-growing renewable energy sources. With increasing capacity of wind turbines, to improve the wind energy utilization and operating efficiency of units has become an important aspect of the study.Firstly, the development of wind power at home and abroad and maximum power point tracking technology are introduced in this paper. Then the mathematical model of wind speed and wind turbine is given. After coordinate transformation, the mathematical model of doubly-fed wind turbine is further gained at rotor coordinate system. Secondly, direct torque control principles based on rotor flux-oriented are studied and the the corresponding models are established.Due to the stochastic and uncertainty of wind speed, the output power of wind farm is caused into continuously fluctuations and shocks. Connecting to grid will inevitably produce a series of adverse effects. As a result, wind turbine operating characteristics especially its dynamic response characteristics become extremely important for the larger wind power penetration grid. In order to improve the wind energy utilization and keep output power stable for rapid fluctuations of the wind, BP neural network PID controller was adopted in this paper in a low wind speed to maximize follow an ideal curve, to achieve the largest output power. At the same time, direct torque control technology was adopted for doubly-fed wind turbines. Direct torque control has advantages including robust, fast torque dynamic response, simple structure, etc. which largely resolved the problems like complex structure, large computing amount ,sensitivity to parameter changes for vector control.The complete VSCF doubly-fed wind turbine simulation model is established including different wind speed models, wind turbine model, DFIG model, DTC model and MPPT model. Finally, the simulation is taken under different wind speed to analyze its dynamic property and then the BP algorithm is improved for further verification, the simulation results show that when changes in wind speed, output power of VSCF wind turbine has better tracking effects, stable system performance which verifies the correctness and effectiveness of control systems.