随着新能源发电的大规模接入,交直流输电系统“强直弱交”特点日益突出。当直流输电系统发生换相失败时,弱送端系统会产生暂态过电压。静止同步补偿器(static synchronous compensator, STATCOM)响应电网电压的变化时,其控制环节的滞后性会导致STATCOM对暂态过电压产生助增作用。针对该现象,文章首先分析了换相失败下弱送端系统暂态过电压的产生机理,接着通过分析频率响应特性,对STATCOM响应滞后时间给出了理论推导,最后针对STATCOM响应滞后特性提出了一种基于阻尼投切的优化策略,以抑制STATCOM对过电压的助增作用,并通过仿真验证了优化策略的有效性。

With the large-scale access of new energy, the power grid presents the characteristics of strong DC system and weak AC system. When commutation failure occurs in HVDC transmission system, transient overvoltage will appear in weak sending end system. Since STATCOM responds to the change of grid voltage through the command of control link, the lag of its control link will lead to the enhancement of transient overvoltage by STATCOM. Firstly, in view of this phenomenon, this paper analyzes the generation mechanism of AC transient overvoltage in weak sending end system under commutation failure. Secondly, by analyzing the frequency response characteristics, theoretical derivation of STATCOM response delay time is given. Finally, an optimization strategy based on damped switching is proposed to suppress STATCOM’s increasing effect on overvoltage response, and the effectiveness of the optimization strategy is verified by simulation. This work is supported by National Natural Science Foundation of China (No. 51277066) and State Grid Corporation of China Research Program (No. 5102-201956301A-0-0-00).

特高压直流输电系统直流闭锁故障及交流系统短路故障引起的暂态过电压,对系统稳定性造成严重冲击。量化评估交直流系统暂态性能指标,对确定交直流电力系统规划设计和调度运行具有指导意义。对交流系统暂态过电压机理进行分析,推导出基于无功补偿和短路比的暂态过电压计算方法,基于系统短路比与补偿电容和交流滤波器参数的比值定义了暂态电压评估指标R_r。研究表明,随着该暂态电压评估指标R_r减小,系统故障后送端换流母线暂态电压升高,受端也会发生不同程度的换相失败。最后,基于国际大电网会议直流标准测试系统,验证了所提指标的有效性。

<p id="p00010">The transient overvoltage caused by the DC blocking fault of the UHVDC transmission system and the short-circuit fault of the AC system has a serious impact on the stability of the system. Quantitative assessment of the transient performance index has important guiding significance for the dispatching operation of AC/DC power system. This paper analyzes the mechanism of transient overvoltage in AC system, deduces the calculation method of transient overvoltage on the basis of reactive power compensation and short-circuit ratio, and then defines the transient voltage evaluation index <i>R</i>_r. Research shows that, as the index <i>R</i>_r decreases, the transient voltage of the commutation bus at the sending end will increase after a system fault, and commutation failures will also occur at the receiving end. Finally, on the basis of the CIGRE benchmark HVDC standard test system, the effectiveness of the proposed index <i>R</i>_r is verified.</p> <p id="p00015">This work is supported by State Grid Science and Technology Project (No. 5230HQ21000S).</p>

目的 针对直流故障后并网点电压大幅度骤升致使风电场面临严重的高电压穿越(high voltage ride-through，HVRT)问题，提出计及保护动作时间协调配合的“有功优先平衡-无功动态补偿”恢复机制。 方法 基于双馈风机的双闭环控制函数，揭示了转子侧变流器无功响应速度优于网侧变流器的动态特性，在减载模式下，提出考虑有功无功协调恢复的风电场HVRT策略。 结果 通过平衡有功功率与无功功率动态补偿，实现了故障期间电压稳定与能量平衡的双重目标。仿真结果表明，该策略可有效抑制暂态过电压风险，提升风电场HVRT能力。 结论 所提策略通过有功-无功协同调控机制，有效破解了高电压穿越过程中系统功率失衡与设备安全运行的矛盾，为含大规模风电的电力系统暂态电压稳定控制提供了新思路。

Objectives To address the serious high voltage ride-through (HVRT) problem faced by wind farms as a result of the large voltage surge at the grid-connected point after a DC fault, a recovery mechanism of “active priority balancing - reactive power dynamic compensation” considering the coordination of protection action time is proposed. Methods Based on the double closed-loop control function of doubly-fed wind turbine, the dynamic characteristics of the reactive power response speed of the rotor side converter is better than that of the grid side converter are revealed. Under the load shedding mode, a HVRT strategy of wind farm considering coordinated recovery of active and reactive power is proposed. Results By balancing active power and reactive power dynamic compensation, the dual objectives of voltage stabilization and energy balance during faults are achieved. Simulation results show that this strategy can effectively suppress the risk of transient overvoltage and improve the HVRT capability of wind farms. Conclusions The proposed strategy effectively solves the contradiction between system power imbalance and safe operation of equipment during HVRT through the active-reactive synergistic regulation mechanism, which provides a new idea for transient voltage stabilization control of power systems containing large-scale wind power.