整流侧控制方式对特高压直流输电系统换相失败影响研究

特高压直流输电系统发生换相失败时，会引起直流电压和直流电流突变，严重影响直流系统的安全稳定运行。控制系统是特高压直流输电系统的核心部分，其控制方式对系统的输出响应有重要影响。分析特高压直流输电系统换相失败的原因，介绍整流侧的控制方式，建立了云广特高压直流输电系统仿真模型，研究云广特高压直流输电系统整流侧采用定电流控制方式和定功率控制方式对换相失败的影响。仿真结果表明：当逆变侧换流变压器变比K改变时，整流侧采用定电流控制与采用定功率控制相比，系统发生换相失败时的临界变比较大；当逆变侧交流母线发生三相对称接地故障、两相短路故障及单相接地故障时，整流侧采用定电流控制与定功率控制相比，系统不发生连续换相失败的临界电阻较小。整流侧采用定电流控制方式时，对换相失败的控制能力优于定功率控制方式。

Study of the Effect of Rectifier Side Control Modes on UHVDC Commutation Failure

Commutation failure in UHVDC transmission system causes sudden change of DC voltage and current and operation stability problems. As core part of UHVDC transmission system, control modes of control system has huge impact on system output. Based on commutation failure analysis, different rectifier side control modes are introduced. The simulation model of Yunnan-Guangdong UHVDC transmission system is built in order to study impacts of constant current control and constant power control on commutation failure in Yunnan-Guangdong UHVDC transmission system. The simulation results show that when rectifier side is under current control mode, the critical voltage ratio of inverter transformer threshold is greater than that of constant power control mode. Also, when rectifier side is under current control mode, the critical resistance value threshold is smaller than that of constant power control mode when three-phase grounding fault, two-phase short circuit fault or single-phase ground fault happens at inverter side AC bus. In summarization, as far as control ability for commutation failure is concerned, constant current control in the rectifier side is better than constant power control.