SVC对电力系统频率稳定性影响的仿真分析

用Matlab软件建立电力系统仿真模型,负荷模型包括异步电动机模型和恒阻抗静态模型,静止无功补偿器(SVC)采用一阶线性化实用模型,对系统遭受双回线永久断一回线和系统负荷突然剧增这2种典型大干扰后SVC动作对系统频率造成的影响进行仿真和分析,包括SVC出力大小、动作时间及控制策略的影响。针对断一回线故障,当负荷端电动机比重较小时,SVC可使频率稳定在额定值。对系统在不同调频能力下负荷剧增时所做的频率变化仿真表明,SVC对系统的频率稳定性产生负面影响,SVC无功出力越大,则频率质量越差,当系统调频能力较弱而SVC无功出力很大时,会加速系统的频率崩溃。因此,在SVC的控制系统中应引入频率反馈,当监测频率低于某一定值时,应减少SVC出力至合理值。

Influence of SVC on power system frequency stability

The simulation model of power systems is established with Matlab,in which the induction motor model and static constant impedance model are included as loads.The SVC(Static Var Compensator) adopts the first-order linear practical model,and its influence on system frequency,such as the compensating capacity,operating time and control strategy,are simulated and analyzed for two disturbances:one of parallel lines breaks off permanently;system load increases sharply.For the former condition,SVC can stabilize the frequency at rating value when the motor load takes a small proportion.For the latter condition,SVC brings negative impact on frequency stability.The more reactive power SVC outputs,the worse the frequency quality becomes.When the frequency adjustment capability of system is poor and the output of SVC is very large,the collapse of frequency will be accelerated.So the frequency feedback should be introduced into SVC control system,and the output of SVC should be reduced to a reasonable value when the monitored frequency is under a fixed value.