Research On Design And Control Of PMSM Used In Independent Pitch System Of MW Wind Turbines

With the development of national energy security utilization andrenewable energy technology, large-scale utilization of the wind powersystem becomes one of the worldwide hot topics. The number of megawattwind turbines installation increases rapidly, their technologies are more andmore mature, and the utilizing rate of wind resources is more efficient.Furthermore, the wind farms are continuously developed from inland oronshore to offshore.The actual wind speed affected by ambient climate and shapes of landsis non-uniformly distributed, that is, it may be overtake the rated windvelocity or occur gust, which will cause relatively large impact on the bladesof the wind turbine. In order to ensure the reliable, safe and stable operationof the blades and make full use of wind energy, large wind power systemsrely on pitch control system, which is installed inside the hub on the top ofthe tower, by adjusting the blade pitch angle to reduce the peak stress of theblade to the acceptable range and moreover to capture wind power in higherefficiency.However, the union method of simultaneous control of the bladescannot maximize the wind power capture for non-uniform wind distribution,and the pneumatic method responses slowly to the outside impact. Thus,electric pitch control system is proposed in this dissertation. The proposedmethod adopts permanent magnet synchronous motor (PMSM) andreduction gear and power electronics to realize servo-driving for each blade.This article presents design and control of PMSM for independent pitchsystem of MW wind turbines based on the project pitch technology research of large wind turbine (No.50709040) supported by NationalNatural Science Fund of China. With the features of wide range of speed-torque characteristics of the independent pitching control system andvoltage fluctuations of power supply, the special structure, simple butefficient control strategy of PMSM are adopted in this article. Performancesand parameters are obtained by2D finite element analysis (FEA) based oncommercial software, namely Ansoft. Meanwhile, the magnetic fielddistribution under different load conditions and simulation results areobtained to ensure the performances of the designed PMSM to satisfy therequirements of independent pitch system.Finally, space vector pulse width modulation (SVPWM) is applied tomathematical model and simulation of PMSM control system. Based on theresults of simulation, independent pitch servo driving system is set upincluding DSP instruction stream, IGBT power module, power supply andmagnetic powder testing load. Experimental results verify the correctness ofthe proposed control strategy and useful information of PMSM is collectedunder different operating conditions, which supports the reliability of theelectric independent pitch system for practical wind turbine application innatural ambient.