Research Of Grid Connected Control Strategy Of Direct Drive Permanent Magnet Wind Power Generation System

With the coal, oil, natural gas and other fossil fuel resources are drying up day byday; the problem of energy security has been paid on more and more attention all overthe world. The influence of global air pollution and greenhouse is becoming more andmore serious; using green power is being one of the most important parts in our dailylife. Considering the advantages of its inexhaustible and no pollution, wind energy hasbeen paid on more and more attention. In recent years, the wind energy market inChina continues to expand; the wind power industry is developing rapidly. In the windpower system, power converters based on power electronic technology is the coredevice mainly. By controlling the converter, the flexible connection between thegenerator and the power grid is realized, and the speed of the generator can be alsoadjusted. The converter has an important significance for the stable, efficientoperation wind power system.In this paper, the research is mainly based on the grid connected inverter of windturbine system with direct drive permanent magnet synchronous generator (PMSG).Compared with double fed wind power generation system, it eliminates the gear box.The fault rate of gear box is a little higher; thereby using “direct drive permanentmagnet synchronous generator” can reduce the cost of generating units in operationand maintenance, improve the reliability of the system and the efficiency of the wholesystem. You can also decouple the active power and the reactive power under theflexible control of direct drive wind power system. At the same time the full powerconverter between the generator and the grid can reduce their interaction withexcellent performance and low voltage ride through (LVRT). The first part, make a comparative study of two kinds of topological structure ofthe direct drive wind power generation system and make a cooperation between theadvantages and disadvantages of them. Select the "uncontrollable rectifier+Boostchopper circuit+PWM inverter" as our own topology. At the same time, make asimple introduce about Maximum Power Point Tracking (MPPT) control theory onthe machine side, Bates theory and Space Vector Pulse Width Modulation (SVPWMrelated) on the grid side.The second parts, according to the topology structure of direct drive wind powersystem on the machine side, establish the mathematical model of the system. Firstly,make a research of the maximum wind energy tracking points acquisition method onthe machine side and Maximum Power Point Tracking (MPPT) control algorithm;then, according to the method of control boost chopper circuit, choose the controlstrategy of double closed loops as the control system of the direct drive wind powersystem machine side, which is the choice of speed loop and current loop; finally,make the control structure figure of the total.The third part, according to the topology structure of direct drive wind powersystem on the grid side, build the two mathematical models of the three-phase staticcoordinates and two-phase rotating coordinates. Firstly, according to the principle ofgrid connected inverter, choose the double loops control strategy of voltage loop andcurrent loop as the control strategy of grid connected inverter. Then, for the voltageouter loop control, use fuzzy control to improve the PI controller, for the current innerloop control, use direct current control and PR control to realize the control goal ofthe inner. Finally, make the control structure figure of the total. The fourth parts, in the MATLAB/SIMULINK environment, make models andSimulations of the rectifier and inverter for permanent magnet direct-drive windpower system, respectively. Analysis of the simulation results of them, then verify thecorrectness and effectiveness of control strategy of this paper.