Factors such as the stochastic nature of weather condition and arbitrariness of loads make power flow have both probability and interval properties. In order to solve power flow considering probability and interval uncertainties for power distribution systems, an approximate method, which combines affine linear three-phase power flow and Latin hypercube sampling (LHS) method, is proposed. The formulation of affine node voltage is derived based on affine inverse operation and conservative estimation method. Bound influences of interval variables (BIIVs) of affine node voltage are used to determine the upper bound and lower bound of the result of probabilistic power flow. Further decomposition of BIIVs, which contributes to reduce the conservation of results, is given. The effectiveness of the proposed method is verified using the modified IEEE 13-bus system and IEEE 123-bus system by comparing with LHS-Monte-Carlo simulation method.

为解决配电网故障定位问题,提出了一种基于果蝇优化算法的故障定位方法.将原先果蝇优化算法中连续的位置坐标和搜索步长离散化,使其与馈线区段的状态信息相联系.对于单电源辐射状配电网和多电源复杂配电网建立了相应的目标函数,分别针对单一故障、含信息畸变的单一故障、多重故障、含信息畸变的多重故障等四种场景进行了测试,测试结果验证了所提出方法的准确性和有效性.与蝙蝠算法、粒子群算法、遗传算法相比,果蝇优化算法在多重故障定位问题中表现出了良好的寻优能力和更快的收敛速度.

现有配电网区间潮流计算大多是以迭代法为基础扩展得到的,需要进行多次区间迭代以获取收敛的潮流解,因而存在收敛性和计算效率低下问题.为此,文中将线性三相潮流算法与仿射求逆方法相结合,提出了一种配电网区间线性三相潮流的非迭代仿射求逆计算方法.所提方法采用仿射数描述区间变量间的相关性,将潮流方程转化为仿射线性潮流方程,并引入仿射矩阵求逆方法对其进行求解.该方法无须迭代,不存在收敛性问题.最后采用多个三相不平衡系统作为算例,通过与其他3种方法的分析比较,验证了所提算法的性能.结果表明,所提算法兼具高效性和低保守性优点,且性能稳定.

Linearized method was used to calculate the power flow of distribution network.And then reactive power optimization model was established by minimizing the voltage stability factor and network loss.The model was solved by particle swarm optimization with an aging and competitive mechanism.Simulation results of IEEE33 and PG&E69-bus system show that reactive power optimization based linearization method in the order of magnitude error of 10-4,its calculation speed is faster than that of forward and backward sweep method and Newton Laphson method.

Many cases, such as distribution network reconfiguration and reactive power optimization, involve large amount of power flow calculations. However, iterative process exists in most of existing power flow algorithms, consuming a lot of time and increasing computational burden. In order to improve power flow calculation efficiency, two simplification methods were used to linearize ZIP load model based on quantitative analysis of simplified conditions of distribution network, and two new versions of linear single-phase power flow method (LSPF) and linear three-phase power flow method (LTPF) based on linear load model were proposed. Performance of the two versions of LSPF and LTPF was tested and compared using several balanced and unbalanced distribution systems, respectively.

On the basis of considering reactive power injections and line resistance, a novel DC power flow algorithm, which takes into account the influence of grounding branches without losing the linearity of DC power flow equations and is suitable to calculate reactive power flow in transmission system, is proposed. The shunt elements in grounding branches are included by utilizing the complete nodal admittance to form corresponding admittance item,and the linearity of DC power flow equations is retained. Nodal voltage amplitude of PQ node could be obtained by the back substitution of modified voltage phase angles. The active power flow and reactive power flow could be solved using the complex power flow equations. IEEE 118-bus test results indicate that compared with DC power flow method without the consideration of grounding branches, the proposed method retains the performance of current DC power flow algorithm in the calculation of active power flow while improving the accuracy of reactive power flow and nodal voltage amplitude, which makes DC power flow method be suitable for calculating reactive power flow in transmission system.

A non-revisited NSGA-II algorithm, which integrates BSP (binary space partitioning)-based non-revisiting mechanism and the non-dominated sorting genetic algorithm-II (NSGA-II) based on the ideology of multi-objective Pareto optimization, is constructed and is then used to solve the problem of distribution networks multi-objective reconfiguration with the consideration of loss minimization and the improvement of reliability. The proposed algorithm achieves a strictly non-revisited research, which avoids the recalculation of power flow and reliability of revisited schemes and saves the computing resources. The test results of IEEE 16-bus and IEEE 33-bus sample systems indicate that the proposed method can obtain the optimal solution in every target direction as well as an optimal Pareto frontier aggregates including a lot of non-dominated solutions in less iterations. According to incidence relations between network losses and reliability goals, along with the topology construction analysis of corresponding reconfiguration schemes, conclusions can be drawn that network losses are in apparent consistency with reliability goals in global scope of solution space, and whether out of the consideration of network loss optimization or reliability optimization, the topology of networks should be close to breadth-first tree rather than depth-first tree.