Network reconfiguration and capacitor placement have been widely employed to reduce power losses and maintain voltage profiles within permissible limits in distribution systems. Reconfiguration method proposed in this paper is based on a simple branch exchange method of single loop. In this simple method of branch exchange, loops selection sequence affects the optimal configuration and the network loss. Therefore, this method has been improved by optimizing the sequence of loops selection for minimizing the energy losses in this paper. Also, a joint optimization algorithm is proposed for combining this improved method of reconfiguration and capacitor placement and therefore maximum loss reduction. For more practical application of the proposed method, different load patterns are considered and a fast method of total energy loss calculation is employed for the economic optimization of energy losses during the planning horizon. Discrete genetic algorithm (GA) is used to optimize the location and size of capacitors and the sequence of loops selection. In fact, the capacitor sizes have been considered as discrete variables. Simulated annealing (SA) is also applied to compare the performance of convergence. The proposed algorithm is effectively tested on a real life 77-bus distribution system with four different kinds of load patterns.

Reconfiguration and Capacitor Placement Simultaneously for Energy Loss Reduction Based on an Improved Reconfiguration Method

http://ehsan3050.persiangig.com/document/10.pdf

Optimal reconfiguration and capacitor allocation in radial distribution systems for energy losses minimization

Different types of distributed generation (DG) are broadly used and optimally placed in a distribution system to improve its performance. Since the network configuration affects the system operational conditions, the network reconfiguration and DG placement should be manipulated simultaneously. Nevertheless, the complexity of the problem may prevent from achieving the optimal solution. This paper presents a novel hybrid method of metaheuristic and heuristic algorithms, in order to boost robustness and shorten the computational runtime to achieve network minimum loss configuration in the presence of DGs. The developed backward/forward power flow is adopted to consider the PV(Q) model of DG. Moreover, different patterns of load types are taken into consideration to perform a practical study. To assess the capabilities of the proposed method, simulations are carried out on IEEE 33-bus and 83-bus practical distribution network of Taiwan Power Company. Furthermore, the proposed method is applied to a 33-bus unbalanced distribution network to verify its applicability in unbalanced distribution systems. The obtained results demonstrate the effectiveness of the proposed method to find optimal status of switches, as well as locations and sizes of DG units, in a rather shorter time than other approaches in the literature.

Energy Loss Minimization in Distribution Systems Utilizing an Enhanced Reconfiguration Method Integrating Distributed Generation

This paper deals with the distribution network reconfiguration problem in a multi-objective scope, aiming to determine the optimal radial configuration by means of minimizing the active power losses and a set of commonly used reliability indices formulated with reference to the number of customers. The indices are developed in a way consistent with a mixed-integer linear programming (MILP) approach. A key contribution of the paper is the efficient implementation of the ${\mmb\varepsilon}$ -constraint method using lexicographic optimization in order to solve the multi-objective optimization problem. After the Pareto efficient solution set is generated, the resulting configurations are evaluated using a backward/forward sweep load-flow algorithm to verify that the solutions obtained are both non-dominated and feasible. Since the ${\mmb\varepsilon}$ -constraint method generates the Pareto front but does not incorporate decision maker (DM) preferences, a multi-attribute decision making procedure, namely, the technique for order preference by similarity to ideal solution (TOPSIS) method, is used in order to rank the obtained solutions according to the DM preferences, facilitating the final selection. The applicability of the proposed method is assessed on a classical test system and on a practical distribution system.

Multi-Objective Reconfiguration of Radial Distribution Systems Using Reliability Indices

This study presents a comprehensive optimisation model that combines reactive power (VAR) optimisation and network reconfiguration to minimise power losses and eliminate voltage violations. In this model, the reactive power of distributed generators (DGs), VAR compensators, the position of tap-changer and the states of branches are formulated as continuous and discrete decision variables. The original non-convex three-phase optimisation model was converted to a mixed-integer second-order cone programming model using the second-order cone relaxation, big-M method and piecewise linearisation. The results of numerical tests showed that the proposed model can achieve significant additional gains in network loss reduction and voltage violation mitigation. This developed method can be used as a basic analysis tool for active distribution networks operation schedule or planning.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/iet-gtd.2015.1228

Mixed-integer second-order cone programing model for VAR optimisation and network reconfiguration in active distribution networks

In distribution systems, network reconfiguration and capacitor control, generally, are used to reduce real power losses and to improve voltage profiles. Since both capacitor control and network reconfiguration belong to the complicated combinatorial optimization problems, it is hard to combine them efficiently for better optimization results. In this paper, a joint optimization algorithm of combining network reconfiguration and capacitor control is proposed for loss reduction in distribution systems. To achieve high performance and high efficiency of the proposed algorithm, an improved adaptive genetic algorithm (IAGA) is developed to optimize capacitor switching, and a simplified branch exchange algorithm is developed to find the optimal network structure for each genetic instance at each iteration of capacitor optimization algorithm. The solution algorithm has been implemented into a software package and tested on a 119-bus distribution system with very promising results.

Joint Optimization for Power Loss Reduction in Distribution Systems

Protection distance of surge protective devices (SPDs) is an important problem in designing a good location scheme of SPDs in low voltage distribution systems for protecting electrical equipments against over-voltage caused by lightning stroke. The simplified lumped-parameter circuit model and the circuit method were used to study the protection distance problem of SPDs. The analytical solutions of the load voltage and general equations of the protection distance of SPDs under different load conditions were given. Simulation results of examples proved the validity of the proposed analytical method.

Protection distance of surge protective devices in low voltage distribution systems

In c-C4F8 and c-C4F8/CO2 mixtures, the swarm parameters including ionization coefficient, attachment coefficient and effective ionization coefficient were obtained at the ratio of the electric field strength to the gas density between 150–550 Td by the steady-state Townsend (SST) method. Static breakdown voltages at each ratio were also measured at the SST condition. The limiting field strengths were obtained by two methods: computing the density-normalized effective ionization coefficient as a function of the overall density-reduced electric field strength; and measuring static breakdown voltages as a function of the product of gas density and electrode separation. Good agreement was obtained by these two methods, which ensures the correctness of the former method. The limiting field strengths of c-C4F8 and c-C4F8/CO2 mixtures were compared with those of pure SF6, SF6/CO2 mixtures and pure c-C4F8. It is found that buffer gas CO2 does not reduce the limiting field strengths of c-C4F8 greatly, the limiting field strengths of c-C4F8/CO2 mixtures are higher than those of SF6/CO2 mixtures or even pure SF6, and so c-C4F8/CO2 mixtures are suggested to be possible substitutes for SF6.

Measurement of swarm parameters of c-C4F8/CO2 and its insulation characteristics analysis

Based on a per-unit model of STATCOM (Static Synchronous Compensator), STATCOM controllability for an arbitrary operating point is proved in this paper. First the nonlinear per-unit model of STATCOM is derived. Then, using the method of Jacobian matrix, the per-unit model of the STATCOM is linearized around a given operating point. Last, based on the linearized per-unit model, the conclusion that the STATCOM can be controlled at arbitrary operation point is obtained. The conclusion is consistent with the one based on the nominal model of STATCOM, and ensure the viewpoint that the STATCOM controllability at an arbitrary operating point is acceptable.

http://www.wseas.us/e-library/conferences/2005tenerife/papers/502-532.pdf

Dong Zhang

Papers

Joint Optimization for Power Loss Reduction in Distribution Systems

Protection distance of surge protective devices in low voltage distribution systems

Measurement of swarm parameters of c-C4F8/CO2 and its insulation characteristics analysis

Proving the STATCOM Controllability at Arbitrary Operating Point Based on Per-unit Model