The Research On The Low Voltage Through Technology Of Direct-driven Grid-connected Wind Turbine

Towards the end of20th and beginning of the21st centuries, interest has risen in the research and development of using renewable alternative energy sources. Among the renewable alternatives, wind energy has an important potential role, and wind power farms are becoming widely used all over the world. Variable speed generation systems show higher energy capturing and better converting efficiency than the fixed speed systems. The direct drive permanent magnet synchronous motor (DD-PMSM) provides Low speed, high efficiency, high power factor, thus making DD-PMSM suitable for variable speed generating system such as wind power.At first, this thesis has introduced the current technologies and low voltage ride through technologies of wind power around the world. Then, the relevant rules for low voltage ride through Low-voltage technology have been introduced. Analysis of instant power transients of on-grid wind power systems in different ways when voltage dipped and the corresponding low-voltage ride through technologies have been made, too. It describes in detail three main low-voltage protection programs of grid-side converter based on energy Crowbar, storage-based Crowbar and secondary-side converter, such several methods, which were often used in on-grid D-PMSM wind power system, comparing advantages and disadvantages of those different programs. It has introduced the related principle of wind turbine and established the model of the wind turbine.This paper studies about the implementation of low voltage ride through control on the direct drive wind generator. Then, the mathematical model of the DD-PMSM and double PWM converter model and DC link mathematical model have been derived. PMSM control mode based on rotor flux oriented and dual PWM converter control strategy have been derived as well. And then it presents a control strategy for reactive power when at failure, and introduces the direct drive permanent magnet wind power system control logic of low voltage ride through intermediate DC link based on energy storage Crowbar.Finally, MATLAB/simulink toolbox is used to simulate the proposed control strategy, and analysis of simulation results. The simulation results and analysis show that the control system of direct-drive permanent magnet synchronous wind power on Low voltage ride through is reasonable.