基于动态无功支撑的全功率变流风电机组高电压穿越改进控制

High Voltage Ride Through Improved Control of Full Power Converter Wind Turbines Based on Dynamic Reactive Power Support

高比例新能源电网中因系统故障引发的风电机组脱网事故时有发生。增强风机故障穿越能力,降低脱网频率对电网稳定运行至关重要。该文首先通过分析变流器矢量控制原理,从理论上得出:电网暂态过电压易导致网侧变流器达到其交流电压调节上限,从而造成交直流功率耦合振荡,引发失稳或过压切机保护。然后参照相关标准要求,确立了基于功率因数调节的高电压穿越(high voltage ride through,HVRT)改进控制策略。该策略通过在故障期间向电网注入无功电流,利用滤波电感的分压作用缓冲过电压冲击,以此满足变流器电压矢量的控制要求;与此同时增加了机组的无功支撑能力,利于电网电压恢复。改进控制根据电压不同,采取分段优化设计,并通过在直流侧加装储能辅助电感分压,提升变流器无功支撑能力和穿越电压上限。最后以风电机组典型参数为依据通过数值定量计算做理论验证,并结合MATLAB/Simulink仿真平台做实验验证,理论和实验结果证明了该文基于暂态过电压故障特性分析的准确性以及对应改进策略的可行性。

In a high proportion of new energy power grid,wind turbine off grid accidents caused by system faults occur from time to time. It is very important to enhance the fault ride through ability of wind turbine and reduce the off grid frequency for the stable operation of power grid. Based on the analysis of the vector control principle of converter, it is oretically concluded that the transient overvoltage of power grid is easy to cause the converter on the grid side to reach the upper limit of its AC voltage regulation, resulting in AC/DC power coupling oscillation and causing instability or overvoltage trip protection. In this paper, based on the requirements of relevant standards, the(HVRT) transient optimal control was established. By increasing the reactive power support, the filter inductor was used to mitigate the overvoltage impact. It not only met the requirements of voltage vector control of the converter, but also increased the reactive current injected into the grid, which was conducive to voltage recovery. The improved control adopted subsection optimization was designed according to different voltages in order to improve the reactive power support and the upper limit of ride through voltage, and energy storage was added to the DC side. The theoretical analysis based on typical parameters and the simulation experiment based on MATLAB/Simulink proved the correctness of the fault characteristic analysis and transient optimal control.