电力系统低压减载和低频减载协调控制策略

低压减载和低频减载是分别解决电力系统中电压稳定问题和频率稳定问题的最常用手段。实际系统中，电压稳定问题和频率稳定问题往往是互相耦合、共同存在的，单独采用一种策略难以同时解决2个问题。文中提出了一种可以实现低压减载和低频减载协调控制的方法。该方法将切负荷控制中的优化问题转化成一个可满足性校验问题，然后采用“搜索+校验”的思路进行求解。求解过程中先采用有序二元决策图（OBDD）等快速搜索算法缩小决策空间，然后针对其中的策略进行可满足性校验。该方法不用求解复杂的多目标、混合整数优化问题，直接得到可行的切负荷策略。最后给出了基于此方法的仿真算例，并通过时域暂态仿真验证了结果的准确性。

A Coordinated Load Shedding Scheme for Both Under-voltage and Under-frequency Load Shedding

Under-voltage and under-frequency load shedding are two common emergency control approaches to ensure the voltage stability and the frequency stability in power systems.Because the under-voltage and under-frequency phenomena are often coupled with each other in practice,single scheme for only one situation is not capable of resolving both frequency and voltage problems at the same time.Therefore,a coordinated load shedding scheme in which both situations are considered is proposed.Adopting the idea of 'searching and verifying',this scheme formulates load shedding as a satisfiability checking problem.First,based on their own complexity,the constraints which are determined by voltage stability and frequency stability requirements are divided into two parts and assigned to either 'searching' or 'verifying' stage respectively.The ones which can be easily depicted by a set of Boolean expressions should be put into the 'searching' stage,while the others should be put into the 'verifying' stage.Second,OBDD algorithm is applied in searching,and the solutions that do not satisfy the constraints in the 'searching' stage are filtered out,therefore,strategy space is reduced.Third,any strategy from the reduced strategy space is further checked by the remaining constraints in the verifying stage in order to get a satisfying control strategy.In the last part of the paper,some simulation results are exhibited to demonstrate the feasibility of the scheme.