Minimum Loss Configuration Research Articles

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

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.

Distribution Loss Minimization With Guaranteed Error Bound

Determining loss minimum configuration in a distribution network is a hard discrete optimization problem involving many variables. Since more and more dispersed generators are installed on the demand side of power systems and they are reconfigured frequently, developing automatic approaches is indispensable for effectively managing a large-scale distribution network. Existing fast methods employ local updates that gradually improve the loss to solve such an optimization problem. However, they eventually get stuck at local minima, resulting in arbitrarily poor results. In contrast, this paper presents a novel optimization method that provides an error bound on the solution quality. Thus, the obtained solution quality can be evaluated in comparison to the global optimal solution. Instead of using local updates, we construct a highly compressed search space using a binary decision diagram and reduce the optimization problem to a shortest path-finding problem. Our method was shown to be not only accurate but also remarkably efficient; optimization of a large-scale model network with 468 switches was solved in three hours with 1.56% relative error bound.

Transmission and Distribution Losses Minimization using Hierarchy Control Method of Transmission System Circuit Breakers and Distribution System Switches for Various PV Penetration Cases

Distribution system has huge number of configuration candidates because the network configuration is determined by state of many sectionalizing switches (SW: opened or closed) installed in terms of keeping power quality, reliability and so on. Transmission system also has huge number of configuration candidates and circuit breakers (CB: opened or closed) as same objective as distribution system. Since feeder current and voltage depend on the network configuration, losses of transmission and distribution systems can be reduced by controlling states of CB and SW. So far, various methods to determine the loss minimum configuration of transmission and distribution systems have been researched. However, a method that hierarchically determines the loss minimum configuration of transmission and distribution system with PV has not been proposed. In addition, power flow of whole system is changed by various PV penetration distribution patterns. Therefore, transmission and distribution losses must be evaluated in various PV penetration cases.In this paper, a hierarchy control method to determine a transmission and distribution loss minimum network configuration by controlling on-off states of CB and SW is proposed. The validity of the proposed method is evaluated to calculate the reduction of whole network loss in a transmission and distribution model with 48 CB and 1404 SW in two kinds of PV penetration cases.

Determination method for loss‐minimum configuration considering reconnection of distributed generators

AbstractIn the field of electrical power system, various approaches, such as utilization of renewable energy, loss reduction, and so on, have been taken to reduce CO2 emission. So as to work toward this goal, the total number of distributed generators (DGs) using renewable energy connected into 6.6‐kV distribution systems has been increasing rapidly. The DGs can reduce distribution loss by appropriate allocation. However, when a fault occurs such as distribution line fault and bank fault, DGs connecting outage sections are disconnected simultaneously. Since the simultaneous disconnection of DGs influences restoration configuration and normal configuration after the restoration, it is necessary to determine the system configuration in the normal state considering simultaneous disconnection of DGs.In this paper, the authors propose a computation method to determine the loss minimum configuration in the normal state considering reconnection of DGs after simultaneous disconnection by fault occurrence. The feature of determined loss minimum configuration is satisfying with operational constraints even if all DGs are disconnected from the system. Numerical simulations are carried out for a real‐scale distribution system model with 252 sectionalizing switches (configuration candidates are 2252) and 120 DGs (total output is 38.46 MW which is 23% of total load) in order to examine the validity of the proposed algorithm. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 176(4): 7–14, 2011; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21142

A new heuristic approach for optimal reconfiguration in distribution systems

This paper presents a novel approach for optimal reconfiguration of radial distribution systems. As an integral part of the distribution system configuration, a load flow algorithm based on graph theory is presented. The algorithm follows changes in system structure by traversing a directed graph of the system to find the depth-first search discovery order. For each switching-iteration, this discovery order generates down-stream-nodes vectors necessary for dynamic generation of two matrices: one is the branch node incidence matrix and the other the relationship between the bus current injection and branch currents. Thus avoiding creation of unconnected branches or forming closed loops. The developed load flow program is integrated with known heuristic techniques in a new heuristic search methodology for determining the minimum loss configuration of a radial distribution system. The technique consists of two parts; one is to determine the best switching combinations in all loops with minimum computational effort while the other is a power loss and voltage profile calculation of the best switching combination found in part one by load flows. Compared to other published articles, the efficient developed load flow reduces the switching combinations searched and gives the optimum solution in few number of load flow runs. To demonstrate the validity of the proposed algorithm, computer simulations are carried out on 33-bus system. The results show that the performance of the proposed method is better than that of the other methods.

分散型電源の再連系を考慮した配電損失最小構成決定手法

In the field of electrical power system, various approaches, such as utilization of renewable energy, loss reduction, and so on, have been taken to reduce CO2 emission. So as to work toward this goal, the total number of distributed generators (DGs) using renewable energy connected into 6.6-kV distribution systems has been increasing rapidly. The DGs can reduce distribution loss by appropriate allocation. However, when a fault occurs such as distribution line fault and bank fault, DGs connecting outage sections are disconnected simultaneously. Since the simultaneous disconnection of DGs influences restoration configuration and normal configuration after the restoration, it is necessary to determine the system configuration in the normal state considering simultaneous disconnection of DGs. In this paper, the authors propose a computation method to determine the loss minimum configuration in the normal state considering reconnection of DGs after simultaneous disconnection by fault occurrence. The feature of determined loss minimum configuration is satisfying with operational constraints even if all DGs are disconnected from the system. Numerical simulations are carried out for a real-scale distribution system model with 252 sectionalizing switches (configuration candidates are 2252) and 120 DGs (total output is 38.46 MW which is 23% of total load) in order to examine the validity of the proposed algorithm. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 176(4): 7–14, 2011; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21142

Distributed Generation Planning Strategy with Load Models in Radial Distribution System

This paper proposes a new approach for distributed generation (DG) planning from the perspective of a distribution company (disco). Optimal sizing and siting decisions for distributed generator is obtained through different approaches: Power loss minimization, System MVA minimization, System cost minimization and System Energy loss minimization. The methodology adopted permits the planner to decide optimal location and size of DG with compromise between Power loss, System MVA, System cost and System energy loss. Normally a constant power (real and reactive) load model is assumed in most of the studies. It is shown that load models can significantly affect the optimal location and sizing of DG resources in distribution systems. A comparative study of optimal location and size of distributed generator provided by installing DG resources with different type of loads models has been performed. utility scenarios as an optimization problem. The objective function was based on supply-demand chain which aimed to minimize the investment and operating costs of local candidate DGs, payments towards purchasing the required extra power by the DISCO, payments toward loss compensation services, as well as the investment cost of other chosen new facilities for different market scenarios. Caisheng Wang et al. (4) proposed an analytical method to determine the best location of candidate DGs for minimum loss configuration. A rigorous analysis for uniformly distributed, centrally distributed, and increasingly distributed loads has been carried out for constant and time varying loads on a feeder. The proposed approach was non-iterative unlike power flow programs. Therefore, there is no convergence problem involved, and results could be obtained quickly. However, authors have indicated that other constraints such as voltage and line limits may affect the DG placement. V ictor H. M endez Quezada et al. (5) discussed such knowledge gap, through the analysis of the impact of DG on distribution losses by studying different scenarios with several DG penetration and concentration levels. Losses are evaluated on an annual basis. Different DG technologies, such as CHP, wind power, and photovoltaic cells, are modeled. For each type of technology, different penetration levels, corresponding with different amounts of DG installed capacity, and different concentration levels, corresponding with several DG units connected along the feeder, are studied.

パレート最適解を用いた配電ネットワーク構成の多目的最適化手法

Distribution network has huge number of configuration candidates because the network configuration is determined by state of many sectionalizing switches (opened or closed) installing in terms of keeping power quality, reliability and so on. Since feeder current and voltage depends on the network configuration, distribution loss, voltage imbalance and bank efficiency can be controlled by changing state of these switches. In addition, feeder current and voltage change by out put of distributed generators (DGs) such as photovoltaic generation system, wind turbine generation system and so on, connected to the feeder. Recently, total number of DGs connected to distribution network increases drastically. Therefore, many configuration candidates of the distribution network must be evaluated multiply from various viewpoints such as distribution loss, voltage imbalance, bank efficiency and so on, considering power supply from connected DGs.In this paper, the authors propose a multi-objective optimization method from three evaluation viewpoints ((1) distribution loss, (2) voltage imbalance and (3) bank efficiency) using pareto optimal solution. In the proposed method, after several high-ranking candidates with small distribution loss are extracted by combinatorial optimization method, each candidate are evaluated from the viewpoints of voltage imbalance and bank efficiency using pareto optimal solution, then loss minimum configuration is determined as the best configuration among these solutions. Numerical simulations are carried out for a real scale system model consists of 72 distribution feeders and 234 sectionalizing switches in order to examine the validity of the proposed method.

数理的最適性が保証された3分割3連系配電損失最小構成の決定手法

数理的最適性が保証された3分割3連系配電損失最小構成の決定手法

Loss Minimum Configuration of Distribution System Considering N-1 Security of Dispersed Generators

Dispersed generators (DGs), such as fuel cells and solar cells, etc., are going to be installed in the demand side of power systems. The dispersed facilities can reduce distribution system loss by the appropriate allocation. However, when a DG that has a large capacity is disconnected from a distribution network by fault, violation of operational constraints, such as line current capacity and voltage drop, may occur. From a viewpoint of system reliability, robust system configuration for suddenly disconnecting DG from the distribution network must be determined, since system operators cannot control DG connection to the distribution network online. In this paper, the authors propose an algorithm to determine loss minimum configuration of a distribution system with DGs while maintaining system reliability. Namely, in the proposed algorithm, N-1 contingencies for DGs are considered as an operational constraint, when the loss minimum configuration is determined under the constraints for line current capacity and voltage drop. In order to determine the loss minimum configuration effectively, an algorithm based on tabu search with strategic oscillation is proposed. Numerical simulations are carried out for a distribution system model with 118 sectionalizing switches in order to examine the validity of the proposed algorithm in comparison with the conventional approach.

Calculation of the loss‐minimum configuration in the IEEJ local power system model

AbstractIn Japan, local power systems (77 kV) are served from the 275‐ or 154‐kV substations. For enhancement of power supply reliability, the transmission lines are connected to several substations, and the operational configuration is radial. The local power system's configuration is determined by connecting and disconnecting transmission lines so as to keep the radial structure and satisfy the operation constraints. When a local power system has a number of transmission lines, many configuration candidates occur. Recently, an IEEJ committee made a practical scale local system model (IEEJ Local System Model). Since the IEEJ Local System Model has 76 transmission lines, the total number of configuration candidates is 276 (approximately 7.5 × 1022). In this paper, the authors try to strictly obtain the loss‐minimum configuration under constraints such as substation capacity, line capacity, and radial structure in the IEEJ Local System Model. In order to obtain the optimal configuration, a new computation algorithm is proposed. In the proposed algorithm, the configuration determination problem is replaced as two combinatorial optimization problems based on the operational constraints [(1) substation capacity, (2) line capacity, and (3) radial structure]. One combinatorial optimization problem (subproblem 1) is to pick up all partial configurations so as to minimize total line loss under the substation capacity constraint. By using the enumeration method, subproblem 1 is solved. Subproblem 2 is solved by using the reduced ordered binary decision diagram (ROBDD). Since the proposed method is based on enumeration and Boolean function, the optimality of obtained solution is guaranteed. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 146(4): 34–42, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10226

電気学会地域供給系統モデルにおける線路損失最小系統構成の算出

電気学会地域供給系統モデルにおける線路損失最小系統構成の算出

A new approach of distribution system reconfiguration for loss minimization

Feeder reconfiguration for loss minimization is a network optimization problem and the solution for the problem involves a search over the configuration. This paper presents a systematic feeder reconfiguration technique that develops an optimal switching scheme to achieve a maximum reduction of losses in a distribution network. The technique restructures the distribution feeders by changing the open/closed status of the sectionalizing and tie switches. A minimal tree-search is proposed in this paper to find the possible switching-options for loss reduction. A loss change formula has been derived and used to determine the switching option that gives the maximum loss reduction in the system. The proposed technique can identify the most effective switching-options for loss reduction, and can achieve minimum loss configuration with minimum computational effort. The performance of the proposed technique is tested on a 33-bus system and the results are compared with that of Baran and Wu's method [Baran ME, Wu FF. Network reconfiguration in distribution systems for loss reduction and load balancing. IEEE Trans. Power Delivery, 1989;4(2):1401–1407].

Artificial neural network approach to network reconfiguration for loss minimization in distribution networks

Network reconfiguration of distribution systems is an operation in configuration management that determines the switching operations for a minimum loss condition. An artificial neural network (ANN)-based network reconfiguration method is developed to solve the network reconfiguration problem to reduce the real power loss in distribution networks. Training-sets for the ANN are generated by varying the constant P-Q load models and carrying out the off-line network reconfiguration simulations. The developed ANN model is based on the multilayer perceptron network and training is done by the back propagation algorithm. The trained ANN models determine the optimum switching status of the dynamic switches along the feeders of the network, which thereby reduce real power loss by network reconfiguration. The proposed ANN method is applied to the 16-bus test system. Test results indicate that the developed ANN models can provide accurate and fast prediction of optimum switching decisions for minimum loss configuration. The proposed ANN method is compared with Kim's method [IEEE Transactions on Power Delivery 8, 1356–1366 (1993)] and a comparative study is presented. The proposed method can achieve minimum loss configuration with drastic reductions in the number of ANNs and less computational time.

Analysis of a dual-receiver node with high fault tolerance for ultrafast OTDM packet-switched shuffle networks

In this paper, we present a high-performance dual-receiver transparent optical node configuration suitable for two-connected multihop transparent optical networks operating at ultrafast bit rates. The steady-state behavior of optical shuffle networks is analyzed with this configuration and a minimum-loss node configuration. Deflection routing is employed as the means for contention resolution. Both analytical results and simulation results are presented on the network performance in terms of network throughput and delay. We also propose modified routing schemes for network fault tolerance. Applying both store-and-forward and deflection routing techniques, the networks can operate without packet loss in the presence of faults.

A new algorithm for the reconfiguration of distribution feeders for loss minimization

The authors report a power-flow-minimum heuristic algorithm for determining the minimum loss configuration of radial distribution networks. The algorithm is based on the concept of optimum flow pattern which is determined by solving the KVL and KCL (Kirchoff's voltage and current laws) equations of the network. The optimum flow pattern of a single loop formed by closing a normally open switch is found, and the flow pattern is established in the radial network by opening a closed switch. This process is repeated until the minimum loss configuration is obtained. A simple, fast and approximate power flow method has also been developed to assist the reconfiguration algorithm. The proposed reconfiguration algorithm has been found to give better network configuration than those obtained by some other methods. >

Loss minimization of distribution feeders: optimality and algorithms

Determining open switch positions for the minimum-loss configuration of a radial distribution system is a discrete optimization problem. The authors present a global optimality condition of the problem and two algorithms: one is based on the uniformly distributed load model and the other on the concentrated current (or power) demand model. The derivation of the optimality condition relies on a concept of 'basic' current profiles of feeder sections and a transformation of the optimization problem. In the first algorithm, a closed form of the minimum-loss open point of a feeder pair can be found since the loss function is piecewise-parabolic. The algorithm obtains the optimal solution when the minimum is obtained for every feeder pair. In the second algorithm, a similar procedure is performed by moving open points, one at a time, from an actual switch position to another until no further loss reduction can be achieved. The proposed algorithm can be utilized as an online aid to distribution system operators.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Loss Minimization of Distribution Feeders: Optimality and Algorithms

Determining open switch positions for the minimum-loss configuration of a radial distribution system is a discrete optimization problem. The authors present a global optimality condition of the problem and two algorithms: one is based on the uniformly distributed load model and the other on the concentrated current (or power) demand model. The derivation of the optimality condition relies on a concept of 'basic' current profiles of feeder sections and a transformation of the optimization problem. In the first algorithm, a closed form of the minimum-loss open point of a feeder pair can be found since the loss function is piecewise-parabolic. The algorithm obtains the optimal solution when the minimum is obtained for every feeder pair. In the second algorithm, a similar procedure is performed by moving open points, one at a time, from an actual switch position to another until no further loss reduction can be achieved. The proposed algorithm can be utilized as an online aid to distribution system operators. >