| Along with the increasing installed capacity of wind power enegy in the whole power electric system, grid codes of different countries haved been strengthened on the requirement of low voltage ride through capacity of wind energy power system. Under certain circumstances, during voltage sags, wind turbine should not break away from the power grid, ans should provide reactive power to the power system.With the advancement of material science and manufacturing capability of power electronic devices, the price of permanent magnetic material and power electronic devices of power converter are decreasing, which stimulates the attention on research on permanent magnetic synchronous power generation system among experts and researchers from both industry and university.The thesis focus on the low voltage ride-through technology of permanent magnetic synchronous wind power generation system. Firstly, a 1.5MW direct-driven synchronous wind power system simulation model is built on the platform of MATLAB/SIMULINK. Then, simulation analysis is performed on the STATCOM operation mode of grid-side converter of Permanent Magnetic Synchronous Generator (PMSG). In the following analysis, grid-side converter is set to operate at STATCOM mode. After that, LVRT based on Crowbar circuit and LVRT based on rotor energy storage are analysed.Taking consideration of characteristic of PMSG wind power system, the thesis proposed a control strategy of Series Dynamic Braking Resistor(SDBR) to complete low voltage ride-through, which has been verified by simulation.Then,incorporating SDBR with traditional LVRT scheme of PMSG, an coorinated control scheme is proposed based on SDBR and Crowbar circuit, which will keep the Crowbar switch from frequently activated.In the end, an coorinated control scheme is proposed based on SDBR and rotor energy storage, which will decrease unbalanced torque on the rotor, and decelerate the rotor speed during voltage sag. |
