抑制高压直流故障引起风电场暂态过电压控制策略

Control Strategy for Suppressing Transient Overvoltage in Wind Farm Caused by HVDC Faults

针对高压直流系统故障时引起送端风电场暂态过电压问题,分析了直流故障对送端暂态电压变化的影响机理,发现故障后交流系统无功盈余是造成电压骤升的根本原因。提出了一种基于分布式调相机和双馈风机(DFIG)无功电压协调控制策略,在风电场并网母线处配置新能源分布式调相机,利用其独特的无功调节特性稳定风电场并网电压,提高风电场的低压或高压穿越能力;在直流系统发生换相失败和直流闭锁严重故障时,DFIG通过改变网侧和转子侧变流器无功参考参与系统无功调节,配合分布式调相机改善故障期间系统电压,并在故障后稳态期间控制DFIG风电场退出无功调节,确保故障恢复后风电场的经济运行。通过PSCAD软件仿真结果表明:在系统发生换相失败和直流闭锁故障后,提出的无功协调控制策略可有效抑制故障后风电场暂态电压变化,提升了风机运行可靠性和经济性。

To address the issue of transient overvoltage at the sending end of the wind farm caused by faults in conventional high-voltage direct current systems system,the impact mechanism of DC faults on transient voltage changes at the sending end was analyzed.It was discovered that the reactive power surplus of the AC system after the fault was the root cause of the sudden voltage rise.To address this,a reactive power coordination control strategy based on distributed synchronous condensers and doubly fed induction generators(DFIG)was proposed.A distributed synchronous condenser was installed at the grid-connected bus of the wind farm to stabilize the grid-connected voltage and improve the low-voltage or high-voltage ride-through capability of the wind farm using its unique reactive power regulation characteristics.During various severe fault scenarios in the DC system,the DFIG participated in reactive power regulation by changing the reactive power reference value,and improved system voltage during the fault period with the distributed synchronous condenser.The DFIG wind farm was controlled to exit reactive power regulation during steady-state after the fault,to ensure economic operation after fault recovery.Simulation results using PSCAD software demonstrate that the proposed reactive power coordination control strategy effectively suppress transient voltage variations of the wind farm after faults,improving the reliability and economy of the wind farm,particularly during commutation failure and direct current blocking in the system.