Study On Grid-connected Inverter For Permanent Magnet Directly Driven Wind Power Generator System

Energy and environment issues have led to a worldwide fever to pursue green power, wind power is overwhelming deemed the nicest renewable energy because it is inexhaustible and unpolluted. The outstanding advantages of distributed generation make the research on grid-connected wind power generation a hotspot, and inverter is the key component which connects wind power generator system and grid. The destination of this paper is to investigate the grid-connected inverter for permanent magnet directly driven wind power generator system.Firstly, operational principle and characteristics of wind power generator system are analysed in detail and a complete mathematical model is established. Then a variable speed variable pitch control strategy is developed, the parameters of circuit are designed, and its simulation models are built in Matlab. Simulation results prove the rationality of the models and the feasibility of the control strategies.Secondly, the main circuit structure, which is composed of three-phase full bridge rectifier and Z-source inverter is presented based on the analysis of power conversion devices in existence. Some parameters of the circuit are designed by analysing the working principle and operating status of three-phase Z-Source inverter. Contrastive analysis between SPWM and SVPWM is carried out in order to achieve the function of inversion, especially the principle and realizing method in Matlab of SVPWM are researched. Aiming at boost voltage function, special methods of adding shoot-through zero vectors are studied, expression among main parameters are derived. Then the simulation models are built in Matlab, simulation results show the simple model can effectively put out waves of SVPWM with shoot-through zero vectors, it realizes the functions of inversion and voltage up.Finally, in order to meet the grid-connected control needs, a control strategy which combines double closed-loop control and vector control based on phase locked loop(PLL) is presented. It achieves a unity power factor grid-connected aim. Then TMS320LF2407A is adopted as the system controller, programs which control the switch of Z-Source inverter on and off are wrote and the design of the soft phase locked loop is completed.