When the low voltage ride-through(LVRT) method of combining rotor energy storage with a discharging resistance for a wind turbine with permanent magnet synchronous generator(PMSG) is adopted, with the traditional control strategy, there are the shortcomings of the rotor energy storage function not exerted to the maximum extent and the large discharging current flowing through the discharging resistance. On the above shortcomings, a LVRT control strategy for a wind turbine with PMSG based on operating simultaneously of rotor energy storage and a discharging resistance is presented. On the basis of the rotor motion equation, the setting calculation formula of the active power of machine-side converter for maximizing the performance of the rotor energy storage is derived, and the switching method of the discharging resistance is designed. Simulation examples of a wind turbine with PMSG rating of 1.5MW are constructed using PSCAD/EMTDC to compare the proposed LVRT control strategy with the traditional control strategy according to the LVRT requirements of China National Standard for a wind turbine generator system. The simulation results show that the proposed LVRT strategy can not only exert the rotor energy storage function to the maximum extent, but also significantly reduce the discharging current, which verifies the effectiveness of the proposed LVRT control strategy.
针对海拔3 500 m以上的超高海拔地区,±800 kV特高压直流输电线路设计经验欠缺的问题,按照典型的±800 kV直流输电线路工程设计条件,通过电磁环境、绝缘子串长和V串夹角、空气间隙的边界条件,对直线塔极间距进行研究,计算不同海拔、V串夹角和冰区条件下直线塔的最小极间距取值.结果表明:电磁环境对超高海拔±800 kV特高压直流线路的极间距选择基本无影响;超高海拔轻中冰区直线塔的极间距受空气间隙、绝缘子串长及V串夹角影响较大;超高海拔重冰区直线塔的极间距主要由绝缘子串长控制.
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