直流整流站最小α限制器对系统稳定性的影响

Influence of DC Rectifier Alpha Min Limiter on System Stability

摘要:

特高压直流输电系统（ultra high voltage direct current，UHVDC）是一个将直流和交流互相转化进行长距离、高电压、大容量传输的系统。UHVDC输电系统动态特性主要取决于电压受控电流指令限制器（voltage dependent current order limiter，VDCOL）和电流控制放大器（current control amplifier，CCA）。当整流站发生交流故障，α角快速降低到允许的最小值；但当故障消失，交流电压恢复后，如果α太小直流电流会很大。为防止这种情况的发生，引入整流站最小α角限制器功能（rectifier alpha min limiter，ＲAML）。ＲAML的存在会对送端交流系统电压稳定性产生影响。对ＲAML的结构和功能进行说明，分别用戴维南等值系统或者单机无穷大系统和一个发电机组代替交流系统，分析ＲAML的存在对于直流系统和交流系统的影响并用等面积法则进行解释说明。最后，用 IEEE 10机39节点模型模拟实际的交流系统，仿真结果验证了ＲAML对系统稳定性的影响。

Abstract:

The ultra high voltage direct current ( UHVDC) , which is responsible for the transformation between DC and AC, can deliver long-range, high-voltage and large-capacity power. The dynamic characteristics of the UHVDC transmission system mainly depend on the voltage-dependent current order limiter (VDCOL) and current control amplifier (CCA). When an AC fault occurs at the rectifier station, the α angle is rapidly reduced to the minimum allowable value. However, when the fault disappears and the AC voltage is restored, the DC current will be very large if the α is too small. To prevent this from happening, the function of the rectifier station’s minimum α angle limiter (RAML) is introduced. The existence of RAML will affect the voltage stability of the sending-end AC system. The structure and functions of RAML are described. By replacing the AC system with a Thevenin equivalent system or a single machine-infinite bus system and a generating unit, the influence of RAML on the DC and AC systems is analyzed and explained using the equal-area rule. Finally, the IEEE 10-machine 39-bus model is used to simulate the actual AC system, and the simulation results verify the effect of RAML on system stability.