The Research On Technologies Of Low Voltage Ride Through For Direct-driven Permanent Magnet Wind Power System

In the recent years, with the increasing environmental pollution and the increasing demand for energy, wind power generation as a resource-rich, clean and renewable energy has caught attention from various countries in the world. The wind power makes up a growing percentage of power grid, which has a big influence to each other. Therefore, wind power system should have low voltage ride through(LVRT) capability to keep connecting to the grid during the fault period.This paper dose in-depth analysis and research focusing on LVRT of the direct-drive permanent magnetic wind power system. Thems are verified to be effective by simulation.Firstly, to summarizes and analyze the background and development situation of wind power in the worldwide. To introduce the development present situation and necessity of LVRT of the direct-drive permanent magnetic wind power system. The principle of components of direct-drive wind power system are researched carefully, including wind turbine, variable-pitch control system, generator, dc-link and converters. Mathematics model are established. The effectiveness of the control methods is proved by simulation results.Secondly, the DC-link crowbar protections are added to solve the LVRT problem, according to regulation of our country’s wind farm access power system technology, making the grid-side running on the reactive power supporting priority mode.Thirdly, to change the generator-side control strategy, making the power the generator-side and grid-side balance. And making the grid-side converter running on the reactive power supporting priority mode, improving the voltage of PCC, achieving the control of LVRT.At last, during voltage fluctuations, to Perfect the LVRT capability, the active power output priority control strategy is proposed, to meet the requirements of grid.