Research Into Control System For Permanent-magnet And Direct-drive Wind Power Generation

Energy shortage has become a worldwide problem.New energy sources such as wind energy,solar energy and other research has received widespread attention.As a renewable and directly usable energy source,wind energy has developed rapidly and become one of main methods of power generation.Permanent-magnet and direct-drive wind power generation has become a main power generation mode because of its high efficiency,and excellent performance.The control of a permanent-magnet and direct-drive wind power generation system consists of the control of the grid side converter and that of permanent magnet generator on the motor side.The grid-side converter control strategy is directly related to the reactive power regulation between the generator and the grid active power transmission and power generation system;and motor generator control strategy to the motor stator output active power and wind energy utilization rate of power generation system.Therefore,it is key to improve the performance of power generation system by adopting the appropriate control strategy of permanent-magnet and direct-drive wind power generation.In this paper,the control strategy of permanent magnet direct drive wind power converter is studied.Firstly,with the grid side converter as the research object,the key technique of grid connected inverter PLL is analyzed to solve the voltage distortion problems may occur,and a double-synchronous coordinate decoupling software PLL is introduced.At the same time the control strategy for grid current is analyzed deeply.Secondly,with the motor-side permanent-magnet motor as the research object,a power topology,a mathematical model,and a double closed-loop control mechanism of the permanent magnet motor are analyzed;and vector control technology is analyzed.Aimed at the practical applications of wind power generation,the speed sensorless control technology for permanent-magnet synchronous motor(PMSM)is studied emphatically.The application to speed sensorless of sliding-mode observer is analyzed.Aimed at the shortcomings of application of sliding mode observer,speed sensorless control technology based on the disturbance observer is introduced in order to avoid the high frequency interference from the state variable current differential and the phase delay caused by digital filter design which be needed for the high frequency harmonics produced by the inherent chattering of sliding-mode observer.Finally,by use of PSIM and Microsoft Visual C++ 6.0,Simulation is performed.The simulation method is used to simulate the performance of the phase locked loop,the two kinds of speed sensorless control and the whole control strategy of the power system..Based on the experimental platform,the control software is written and experiments are carried out.The simulation and experiment results indicate that the proposed control strategy for permanent-magnet and direct-drive wind power system can realize VSCF operation system,grid voltage fault under precise phase-locked,independent regulation system output active power and reactive power,permanent magnet motor speed sensorless and stable operation,good sinusoidaloutput current.The simulation and experiment results accord with the theory,and that lay the foundation for engineering application.