Transient stability constrained optimal power flow using trajectory sensitivities

Abstract

为将暂态稳定约束最优潮流问题转化为最优潮流和暂态稳定两个子问题,根据暂态稳定计算结果求出 发电机转角及转速相对于机械输入功率的轨迹灵敏度。基于轨迹灵敏度,计算出在最领先发电机和最落后发 电机之间转移的有功功率,据此修改其在最优潮流模型中的有功功率上下限,从而实现两个子问题的交替求 解。并且推导出准确的轨迹灵敏度及初值计算公式,利用上述公式,得更小的转移功率值,从而使功率转移后 系统的优化程度更高。同时在惯性中心坐标下采用最大转角判据找出最领先机和最落后机,并以3机9节点和 10机39节点系统为例,验证了该方法的可行性。 Transient stability constrained optimal power flow(TSC-OPF) problem is divided into two sub-problems,which are optimal power flow(OPF) and transient stability control.Trajectory sensitivities of both velocities and rotor angles of generators with respect to their mechanical input power are calculated according to the results of transient stability simulation.Shifting active power between the most critical machine and the least critical one to regain transient stability is obtained according to trajectory sensitivities,based on which upper and lower active power limits of generators in OPF model are modified and thus OPF problem and transient stability control can be performed iteratively.Accurate expressions of trajectory sensitivities and their initial values have been derived instead of using approximate ones by which smaller shifting active power can be obtained and thus a more optimal operation point of power system can be given.A biggest rotor angle criterion under the center of inertia reference frame is used to determine critical order of generators.Furthermore,results obtained from 3-machine 9-bus system and 10-machine 39-bus system validate the proposed method.