考虑风电机组故障穿越特性的电压反复波动机理分析与抑制

Mechanism Analysis and Suppression of Repeated Voltage Fluctuation Considering Fault Ride Through Characteristics of the Wind Turbine

近年来,大规模风电汇集系统实际运行中频繁出现电压反复波动现象,具有波动幅度大、波动峰谷值切换速率达秒级的特点,与风能随机性、无功补偿装置动作引起的电压波动现象具有显著区别,运行中多次造成风电机组因连续穿越失败而脱网,严重威胁了电网安全稳定运行。上述现象涉及风电机组故障穿越策略与弱电网功率-电压特性的耦合作用,难以通过传统电力系统电压稳定分析方法直接解释。提出了考虑风电机组低电压穿越特性的系统有功-电压曲线(PV曲线)分析方法,准确刻画波动过程中系统运行点轨迹变化规律,并通过仿真进行了验证。在此基础上,提出了抑制电压反复波动的风电机组低电压穿越优化控制策略,基于实际算例的仿真分析表明,提高风电机组退出低电压穿越阈值及采用穿越期间维持有功的策略可以有效抑制电压反复波动现象。

In recent years,the large-scale wind power collecting system has frequent voltage fluctuation in actual operation,and has the characteristics of large voltage fluctuation range and the fluctuation speed reaching the second level.It is significantly different from the voltage fluctuation caused by wind randomness or switching of reactive power compensation device.In operation,the wind turbines have been disconnected due to continuous low voltage ride through(LVRT),which seriously threatens the safe and stable operation of the power grid.The above phenomena involve the coupling effect of wind turbine LVRT strategy and power-voltage characteristics(PV curve)of weak power grid,which is difficult to be explained directly by the traditional voltage stability analysis method.This paper presents a method of analyzing the PV curve of wind turbine considering the characteristics of LVRT.The changing track of the system operating point is accurately described in the fluctuation process,and verified by simulation.Based on the analysis of the simulation results,the paper proposes the optimal control strategy of wind turbine LVRT to restrain the repeated voltage fluctuation.The simulation analysis based on the actual calculation shows that the strategy of increasing the threshold value of wind turbine exit LVRT and maintaining active power during LVRT can effectively suppress the phenomenon of voltage fluctuation.