适应于多场景频率特性的低频减载优化方法

Optimization methods of under frequency load shedding schemes adapted to multi-scene frequency characteristics

分析电力系统解列对频率特性及低频减载方案的影响,通过实际区域电力系统的仿真计算,表明现有低频减载方案不适应于系统解列后频率特性的变化,会导致负荷过切。针对各种运行方式下严重故障导致系统解列的有限个场景,提出考虑多场景频率特性的低频减载多目标优化问题,以每轮负荷切除比例为优化变量,建立以平均频率偏差以及切负荷量最小为目标函数、以每轮切负荷量和系统动态频率约束为约束条件的优化模型,并采用NSGA-Ⅱ优化算法求解。实际区域电网算例表明优化后的低频减载方案能使系统具有更好的频率稳定性,并减少切负荷量。

The frequency characteristics of multi-machine power system and its influencing factors were analyzed in this paper, and the influences of a system splitting on frequency characteristics and under frequency load shedding（UFLS） were also analyzed. By simulating calculation of practical regional power grid, it is pointed out that the existing UFLS scheme may not be adapted to the variation of frequency characteristics, which may cause over load shedding after a system splitting. According to all operation modes, the UFLS multi-objective optimization problem adapted to multi-scene frequency characteristics under the serious faults was proposed. The cut ratio of each round was set as optimization variables, the system dynamic frequency and load shedding of each round were set as constraints, and the NSGA-Ⅱ algorithm was applied to solve the opti mization problem which took both the minimum average frequency deviation and load shedding as objective function. By simulation comparing the adaptability of the existing and optimized UFLS scheme based on the practical regional power system, it was found that the optimized scheme has a better frequency characteristics and avoid load over-cut.