Research Of Wind Turbine Speed Control System

Worldwide energy shortage and environmental degradation has promoted the rapid development of wind power generation industry. Variable Speed Wind Turbines (VSWTs) can change the speed in a wide range, track the wind speed variation to work on the tip speed ratio (TSR) and capture the maximum wind power. So control strategies for VSWTs draw much attention of researcher from all over the world. Research on wind turbine speed control has important theoretical and practical value.In this paper, improved PI control driven by virtual unmodeled dynamics for the tip speed ratio was proposed. Software simulation platform and semi-physical simulation platform were developed for the validation of advanced control strategies. Simulation results and comparison studies showed the effectiveness of the proposed methods. The main research contents are as follows:(1) To deal with the model structure and parameter uncertainties, strong disturbance and strong nonlinearity of the wind turbine system, a PI controller driven by virtual unmodeled dynamics was proposed in this paper. The controller consists of PI controller, feedforward controller, virtual unmodeled dynamics estimator and compensator and a filter. The proposed controller can reduce the effect of wind disturbance and that of virtual unmodeled dynamic and improve tracking performance; the control structure is simple and easy for implementation.(2) To deal with the uncertainty in the mechanism model, a curve fitting method was given to build the function relationship between power efficiency and TSR. Thus, the proposed control method can be implemented for real wind turbines.(3) Improved virtual unmodeled dynamics driving PI control method with a filter was proposed. Simulation results showed the importance of the filter.(4) To deal with the large measurement error of anemometers, wind estimator based on Kalman filter and Newton-Raphson method was designed. It uses the wind turbine itself as a wind speed measuring device; the estimated wind speed was used to calculate reference generator speed to improve wind energy capturing ability. It was also used as the input of feedforward controller to reduce the effect of wind disturbance.(5) In order to verify the proposed algorithm performance, a software simulation platform and a semi-physical simulation platform were developed. The software platform consists of virtual wind turbine module, communication interface module, data interaction module, controller module and post-processing module and so on. Functional user interface was designed for the convenience of operation. The semi-physical platform uses the real industrial controller, it consists of virtual wind turbine module, communication module, signal processing module, controller module, real-time data monitoring module and so on. It has Simulink programming interface and supply a platform for industrial implementation simulation of advanced control algorithms. The platforms were tested and show efficiency in wind turbine control simulation. The PI control method and the proposed control algorithm in this paper with the same parameters as the PI controller were simulated. Simulations and comparative studies show the good tracking performance of the proposed algorithm. The simulation also shows that the proposed method is easy for implementation in industrial applications.