Research On Control Of Converter For Direct-driven Permanent Magnet Synchronous Wind Generation System

As the world's fastest growing renewable energy source, wind energy has drawn worldwide attention. Direct-driven wind generation system is considered to be an important research direction in wind generation technology area due to its superiorities of being gearless, no slip rings and brushes, flexible power control ability, etc. This thesis has studied on the modeling, control strategy of the direct-driven Permanent magnet synchronous Generator based wind turbine. Simulations demonstrate the correctness of the research results. Following are the major research work of this dissertation. The main content of this thesis are as follows:Firstly, mathematical model of permanent-magnetic direct-drive wind power generation system is built, including wind speed, wind turbine, Permanent magnet synchronous Generator and converter. And the device parameters of main circuit of dual PWM converter are designed.Secondly, research on control strategies of grid-side converter and generator-side. Based on the deep analysis of the operation principle and mathematic model of the grid-side converter, double closed loop control scheme based on a grid voltage oriented vector is designed. Based on analysis of modulation principle of SVPWM, PSCAD simulation module is built. For generator-grid converter, based on deep analysis of the mathematic model of PMSG, a d axis flux oriented vector control strategy is designed,the algorithm of the optimal tip-speed ratio is also designed to realize Maximum power tracking in Variable wind speed.Simulation platform of Direct-driven wind generation system was built in PSCAD/EMTDC. After that, the simulation was made on the platform respectively in constant wind speed and variable wind speed. The simulation results show that the grid-side converter can achieve keeping dc-link voltage in constant, low output harmonic current, utility operating, independent regulation of active and reactive power, etc, and show that the correctness and feasibility of the algorithm of the optimal tip-speed ratio.Finally, Analyses the necessity and the methods of realization of LVRT. And mainly research on the power dissipative Crowbar circuit. The simulation of LVRT was made in PSCAD and its validity is confirmed.