计及静态电压稳定约束的无功优化规划

选择无功补偿设备投资和系统有功网损的综合费用作为目标函数,同时考虑满足电压水平和电压稳定性两个约束条件来探讨无功规划问题。选取用电压稳定裕度不低于某一个允许的最小稳定裕度来表示电压稳定约束。分别对正常运行工作点和电压崩溃点引入2组变量和潮流方程,从而使得电压稳定裕度可以用临界运行状态下负荷的总视在功率与正常运行状态下负荷的总视在功率之差来显式表达。该模型相对于传统无功规划模型的优势表现在能够根据稳定裕度的目标值直接求得在合理电压水平下的最佳无功补偿配置方案,但其优化模型的等式和不等式约束及变量的数目却大幅增加,使得计算量远大于传统的无功规划问题。在IEEE 14节点和118节点2个试验系统的计算表明,采用非线性原对偶内点法求解该模型时,其计算精度及收敛性都比较好。

Optimal Reactive Power Planning Incorporating Steady State Voltage Stability Constraints

The cost that integrates investment of reactive equipments with active-power loss of electric power network is selected as objective function. The two sets of constraints concerning voltage profile and voltage stability are simultaneously considered to investigate reactive-power planning problem. A voltage stability margin that is not lower than a certain minimum permissible stability margin is chosen to express the voltage stability constraint. Two groups of variables and power-flow equations are introduced respectively for the normal state and the critical state so that the voltage stability margin can be represented explicitly by the difference between total apparent power of load in the critical state and that in the normal state. Compared with conventional reactive power planning model, this model can obtain optimal reactive power configuration scheme directly under a suitable voltage profile according to a target value of the stability margin. However, the number of equality and inequality constraints and variables increases obviously, which makes computational efforts greater than that in the conventional reactive power planning model. Results on IEEE 14-bus and IEEE 118-bus test systems show that nonlinear primal-dual interior-point method can be used for solving this model with satisfactory precision and convergence.