Research On Generator-side Control Strategy Of Permanet Magnet Direct-drive Wind Power Generator System

In recent years, with the development of economy and construction, the resources and environment become the two key issues of human society’s survival and development.Cleaning energy becomes the main development direction in the future. The wind power with the advantages of clean, renewable, and no pollution has emerged among so much new energy resources. The proportion of wind power capacity in our country is becoming higher and higher in global development. And at this moment, the efficiency of wind power has become the principal problem that researchers concern. How to effectively improve the utilization rate of wind energy is a significant issue.This topic is based on the permanent magnet direct-drive wind turbine as the research object and takes the maximum wind energy capture as research purposes. Carry on the research and analysis in view of the wind turbine control strategy and give corresponding control strategy respectively to achieve the high efficiency of wind power conversion. Verify the rationality of the wind turbine control strategy through the modeling and simulation analysis.Firstly, determine the wind power system’s overall structure and the corresponding converter topology structure; analyze the control principle of each part respectively, and establish the corresponding mathematical model. Present the simulation model of wind turbine, the parameters simulation model of the generator and the mathematical model of current transformer; determine the overall control scheme, and at the same time provide theoretical basis for following research.Secondly, study the machine side part of permanent magnet direct drive wind turbine .When the wind speed is lower than the rated wind speed, in order to achieve the maximum wind energy capture that main is maximum power point tracking and two control methods is given in this chapter-variable step hill-climb searching algorithm and sliding mode variables structure (SMC) control method. Expound and comparative analys of the principle,mathematical modeling, simulation and result analysis respectively.Then, study the machine side part of permanent magnet direct drive wind turbine aim at the condition of the wind speed is higher than the rated wind speed. When the wind speed is higher than the rated wind speed. Adopt the variable pitch control in order to alleviate the pressure of the system load. Use the generator speed as feedback to implement PI regulating to gain the pitch angle signal. And base on this in order to make the control system has better rapidity and stability. Apply the power output as the feedback signal to implement PI regulating, in order to gain the pitch angle signal as compensation signal. Verify the running effect through simulation modeling analysis.Finally, study of the machine side converter control strategy. Adopt SVPWM technology and introduce the method of modulation principle and the implementation process in detail. And gain the accurate and stable simulation model through simulation verification. Provides accurate module for the machine side joint simulation. At the same time, introduce PR control into the direct-drive wind turbine system’s current regulation according to the problem of machine side converter harmonics. Realize the system’s harmonic compensation through the simple superposition approach.