中文摘要：

动态无功优化是保障电网安全经济运行的重要手段之一。然而,动态无功优化属于大规模、多时段、强耦合的非线性混合整数规划问题,直接求解困难。为处理无功优化问题中包含的离散变量及时段耦合约束,基于动态无功优化问题的物理本质,提出了动态无功优化模型的多阶段求解方法。第1阶段以系统网损最小化为目标,松弛离散变量和无功设备全天动作次数约束,基于内点法计算得到动态无功优化问题的初始解。第2阶段以网损增量最小化为目标,基于目标函数对控制变量的灵敏度,将子问题在当前解附近线性化,构建以无功控制设备全天动作次数为约束的混合整数规划模型,由此决策无功设备全天动作次数约束下的离散控制变量优化解。在此基础上,将第2阶段得到的优化结果代入到第1阶段的优化模型当中,得到多阶段动态无功优化问题的优化结果。Ward＆Hale 6节点算例系统和国内某省网实际系统计算结果验证了所提模型和求解方法的高效性和适用性。

英文摘要：

Dynamic reactive power optimization（DRPO） is a significant approach to ensure safe and economic operation of power systems. It is a large-scale, multi-period and strongly coupled nonlinear mixed-integer programming（MIP） problem, which is difficult to solve directly. Therefore, based on physical insight of DRPO, this paper proposes a multi-stage modelling and solution approach for DRPO, especially focusing on handling discrete variables and switching operation constraints.It divides a complicated mixed-integer non-linear programming（MINLP） problem into a non-linear programming（NLP） and a MIP problem. In the first-stage, the objective is to minimize total system loss. Interior point method is adopted to obtain continuous initial solutions by relaxing discrete variables and switching operation constraints. In the second-stage, the objective is to minimize incremental system loss. Its sub-problem is linearized near current solutions based on sensitivities of control variables corresponding to objective function. A MIP model is formulated to optimize discrete variables subject to switching operation constraints. Next, results of the second-stage problem are substituted in the first-stage problem to complete whole DRPO. Finally, Ward Hale 6 bus test system and a practical system of some province of China are presented to verify effectiveness and applicability of the proposed model and approach.