Research On Control Strategy Of Permanent Magnet Synchronous Wind Generator

Because of increasing pollution level and decreasing fossil fuels, the clean andrenewable energy resources have attracted worldwide interest. As the most cost-effectiveway to generate electricity from renewable resource, wind energy generation has gotrapidly development since21stcentury, and the variable-speed constant-frequency windenergy generation system(VSCF-WEGS) is being the most widely used in modern windpower system. Owe to its simple structure, flexible control, and high fault ride-throughcapability and so on, the permanent magnet synchronous wind generation system has beenwidely used, also been a research focus in Power Electronics field. Therefore, this studyfocuses on the research of the control strategy of permanent magnet synchronous windgenerator.Firstly, the topology and working principle of the back-to-back pulse widthmodulation (PWM) converter are introduced. Then mathematic model of the permanentmagnet synchronous generator (PMSG) is built, and several vector control strategies ofPMSG are compared. By comparison, zero direct-axis current control is used in this paper.Based on the mathematic model of the wind turbine, the maximum power point tracking(MPPT) principle of the WEGS is introduced. After analyzing several MPPT algorithms,the optimal torque control is applied to realize the MPPT. The mathematic model of thegrid-side filter is built. According to the performance inverter aimed to achieve, the gridvoltage-oriented vector control is used as the inverter’s control strategy.Configuration rules of the criticalmain circuit parameters of the system areintroduced. A1.5MW simulation module is developed in MATLAB/Simulink, the resultson simulation module under different wind speeds verify that the WEGS built in this papercan realizezero direct-axis current control, MPPT and the other design indexes. Based on ainduction motor and a PMSG, a experimental platform of WEGS is developed. The vectorcontrol of PMSG and the control of the back-to-back converter are carried out on theplatform, and the experimental results further demonstrate the validity of the designedsystem.To deal with the output power fluctuations of wind generator, an improved optimal torque control with a low pass filter (LPF) is proposed. After analyzing the impact of theLPF on the system, the requisite amplitude-frequency characteristic of it is given. Thenpole-zero configuration approach is used to design the LPF. Finally, a comparison studybetween the general optimal torque control strategy and the improved is carried out on the1.5MW simulation module. It can be concluded from the simulation results that theimproved optimal torque control has superior performance in smoothing the powerfluctuations.