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This paper presents allocation of energy losses to consumers connected to radial distribution networks in a deregulated environment. A detailed comparison of the proposed 'Exact Method' with three alternative algorithms, namely, pro rata, quadratic allocation and proportional allocation are presented. Pro rata procedure is based on the load demand of each consumer, quadratic and proportional allocations are based on identifying the real and reactive parts of current in each branch and the losses are allocated to each consumer, and the proposed 'Exact Method' is based on the actual contribution of real power loss by each consumer. A case study based on a 30-node distribution system is provided. Index Terms--Deregulation, energy loss allocation, radial distribution systems.

A new approach to improve the reconfiguration operations of distribution systems is presented in two papers. In this first part n economic dispatch (ED) through radialization method for medium voltage (MV) distribution networks with several alternative supply points and several energy prices is presented. The optimization criterion is based on energy purchase cost minimization to supply both the load and the loss. The ED through radialization (EDR) method assesses the economic impact of different energy prices for alternative supply points on the operative radial topology for a specific load level. Capacity limits of supply points and MV lines are considered, as well as the quality technical product using ac power flow calculations. The results obtained for a distribution network widely used in the literature show the effectiveness of the proposed methodology. The second part presents a methodology to determine the optimal reconfiguration plan for short and medium terms. This approach integrates purchase and switching costs associated to the reconfiguration plan. Index Terms--Ac power flow, economic dispatch, energy price, loss, minimization costs, network reconfiguration, radialization.

This paper presents a very efficient, two-stage method for the distribution system reconfiguration for loss minimization. The efficiency of the method stems from the use of real power loss sensitivity with respect to the impedances of the candidate branches. The proposed method uses these sensitivities in the first stage. A branch exchange procedure is used in the second stage to refine the solution. Results for five test systems have been obtained with the proposed method in order to demonstrate the effectiveness of the algorithm. Index Terms--Distribution system, loss minimization, network reconfiguration, sensitivity.

In this paper, the concepts related to loss partitioning among the phase currents in three-phase distribution systems are revisited in the light of new findings identified by the authors. In particular, the presence of a paradox in the classical loss partitioning approach, based on the use of the phase-by-phase difference between the input and output complex power, is highlighted. The conditions for performing effective loss partitioning without the occurrence of the paradox are thus established. The corresponding results are then used to extend the branch current decomposition loss allocation method for enabling its application to three-phase unbalanced distribution systems with distributed generation. Several numerical examples on a three-phase line with grounded neutral and on the modified IEEE 13-node test system are provided to assist the illustration and discussion of the novel conceptual framework. Index Terms--Distributed generation, distribution systems, loss allocation, loss partitioning, losses, paradox, unbalanced systems.

The reactive power capability of wind generation (WG) producers can be used to provide volt/voltampere reactive (var) support in electrical distribution systems. In practice, the distribution network operator (DNO) is not able to dispatch reactive power of all generators, and such units are referred to as nondispatchable generators. Then, the reactive power of these nondispatchable generators is not a defined value, and it should accomplish the limits settled by national grid codes. This paper addresses the optimal reactive power provision of nondispatchable WG units under a loss allocation strategy based on incremental generation use of the system (GUoS) tariffs. The optimization problem is set from generators' viewpoint aiming to find the reactive power provision that minimizes the loss charges subject to operational constraints. Optimal solutions are compared with the DNOs mandatory dispatches using a reactive optimal power flow tool. Two test systems are analyzed: a 10-kV 28 bus and 60-kV 55-bus system throughout 672 and 168 h, respectively. The proposal permits to identify which units can be dispatched by the DNO due to its effect on the network. Index Terms--Loss allocation, losses, mathematical programming, reactive power, wind power generation.

At high-frequency applications, the gate drive loss of the power metal oxide semiconductor field-effect transistor (MOSFET) becomes quite significant. A new dual-channel low side resonant gate drive circuit is proposed in this paper. The proposed drive circuit can provide two symmetrical drive signals for driving two MOSFETs. It charges and discharges the MOSFET gate capacitor with a constant current source. Both gate drive loss and, more importantly, switching loss can be reduced significantly. The proposed resonant gate drive circuit can be used to drive the synchronous MOSFETs in a current doubler or full-wave rectifier configuration. It can also be used to drive the primary MOSFETs in push-pull converters. Analysis, computer simulation, and experimental results show that significant power loss reduction is achieved by the proposed circuit. Index Terms--Gate drive loss, MOSFET driver, resonant gate drive circuit, switching converters, switching loss.

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. Index Terms--Capacitor control, genetic algorithm, joint optimization, loss minimum, network reconfiguration.

This paper deals with distribution network (DN) reconfiguration for loss minimization. To solve this combinatorial problem, a genetic algorithm (GA) is considered. In order to enhance its ability to explore the solution space, efficient genetic operators are developed. After a survey of the existing DN topology description methods, a theoretical approach based on the graph and matroid theories (graphic matroid in particular) is considered. These concepts are used in order to propose new intelligent and effective GA operators for efficient mutation and crossover well dedicated to the DN reconfiguration problem. All resulting individuals after GA operators are claimed to be feasible (radial) configurations. Moreover, the presented approach is valid for planar or nonplanar DN graph topologies and avoids tedious mesh checks for the topology constraint validation. The proposed method is finally compared to some previous topology coding techniques used by other authors. The results show smaller or at least equal power losses with considerably less computation effort. Index Terms--Distribution network (DN), genetic algorithm (GA), graph theory, matroid, minimal loss reconfiguration, planar graph, spanning tree.

This paper presents a new method for transmission loss allocation. The method is based on tracing the complex power flow through the network and determining the share of each load on the flow and losses through each line. Transmission losses are taken into consideration during power flow tracing. Unbundling line losses is carried out using an equation, which has a physical basis, and considers the coupling between active and reactive power flows as well as the cross effects of active and reactive power on active and reactive losses. A tracing algorithm which can be considered direct to a good extent, as there is no need for exhaustive search to determine the flow paths as these are determined in a systematic way during the course of tracing. Results of application of the proposed method are also presented. Index Terms--Deregulation, open access transmission, power flow tracing, transmission loss allocation.

This paper first investigates a local voltage and reactive power control (local control) in a distribution system based on local control of on-load tap-changer (OLTC), substation capacitors, and feeder capacitors, and how the presence of induction machine based distributed generation (DG) affects it. A proper coordination among those available voltage and reactive power control equipment to minimize losses in the distribution system, with and without DG, is formulated. Secondly, a combined local and remote voltage and reactive power control (local-remote control), which is based on automated remote adjustment to the local control in order to minimize the losses even more, is proposed. The automated remote adjustment in the local-remote control is also intended to keep the operating constraints fulfilled all the time, which cannot be achieved by using the local control when DG is present in the system. The OLTC and substation capacitors are assumed to be remotely controllable, while the feeder capacitors are not. DG with both constant power and varying power are investigated. Index Terms--Capacitor, distributed generation, distribution system, induction machine, losses, on-load tap-changer, reactive power control, voltage control.

To get the distribution network to operate at its optimum performance in an automated distribution system reconfiguration was been proposed and researched. Considering, however, that optimum performance implies minimum loss, no overloading of transformers and cables, correct voltage profile, and absence of phase voltage and current imbalances, network reconfiguration alone is insufficient. It has to be complemented with techniques for phase rearrangement between the distribution transformer banks and the specific primary feeder with a radial structure and dynamic phase and load balancing along a feeder with a radial structure. This paper contributes such a technique at the low-voltage and medium-voltage levels of a distribution network simultaneously with reconfiguration at both levels. While the neural network is adopted for the network reconfiguration problem, this paper introduces a heuristic method for the phase balancing/loss minimization problem. A comparison of the heuristic algorithm with that of the neural network shows the former to be more robust. The approach proposed here, therefore for the combined problem, uses the neural network in conjunction with a heuristic method which enables different reconfiguration switches to be turned on/off and connected consumers to be switched between different phases to keep the phases balanced. An application example of the proposed method using real data is presented. Index Terms--Distribution automation, distribution control, heuristic algorithm, load balancing, neural network, optimal control, phase arrangement, phase current imbalance, phase voltage imbalance, power loss, reconfiguration.

This paper presents allocation of power losses to consumers connected to radial distribution networks before and after network reconfiguration in a deregulated environment. Loss allocation is made in a quadratic way and it is based on identifying the real and imaginary parts of current in each branch, and losses are allocated to consumers. The network reconfiguration algorithm is based on the fuzzy multiobjective approach and the max-min principle is adopted for the multiobjective optimization in a fuzzy framework. Multiple objectives are considered for real-power loss reduction in which nodes voltage deviation is kept within a range, and an absolute value of branch currents is not allowed to exceed their rated capacities. At the same time, a radial network structure is maintained with all loads energized. The three objectives considered are modeled with fuzzy sets to evaluate their imprecise nature and one can provide his or her anticipated value of each objective. A 69-node example is considered to demonstrate the effectiveness of the proposed method. Index Terms--Fuzzy multiobjective optimization, loss allocation, network reconfiguration.

High power conversion efficiency is an important requirement of the front-end power-factor-corrected (PFC) boost rectifier that is used in shaping the ac input current in a typical modern switch-mode power supply. A reasonably accurate estimate of the power losses in individual components is essential in order to improve the efficiency of the PFC rectifier. In this paper, difficulties in the measurement of individual component power losses with particular reference to an ac--dc converter are brought out. A method of loss evaluation by measurement of temperatures of individual components and surrounding ambient is presented. Experimental results that are carried out on the front-end boost PFC rectifier of a commercial ac-dc converter are presented to validate the loss estimation method. Index Terms--Loss measurement, power factor, pulsewidth-modulated power converters, rectifiers, switch-mode power supplies.

The fabrication of low-loss transmission line structures with an air dielectric layer is described. The channels are characterized at low frequency (10 and 100 kHz) using capacitance and loss tangent and at high frequency (500 MHz to 10 GHz) using S-parameter measurements. The incorporation of an air gap resulted in structures with effective dielectric constants between 1.5-1.8 and significantly lower loss tangents. The fabrication technique could be used to create more complicated air gap transmission line structures for use in monolithic microwave integrated circuits. Index Terms--Air gaps, dielectric losses, multiprocessor interconnection, transmission lines.

The installation and operation of distributed generators (DGs) has great potential for local utilities to improve distribution system reliability and lower their operating and expansion planning costs. To evaluate this potential, distribution system analyses must reflect its new operating environment with significant DG. Resulting tools can be utilized by both utilities and DG owners to improve their decision making algorithms. As such, this work investigates two different slack bus models for unbalanced distribution power flow and their impacts on subsequent cost analysis. The models include the traditional single slack bus model which assigns the substation as the slack bus and a distributed slack bus model which assigns slack to the substation and DGs according to network-based participation factors. Detailed expressions for cost analysis which directly depend on the distributed slack bus model are presented and discussed. Simulations illustrate that the different slack bus models have significant impacts on cost analysis. The difference in estimated annual profit for local utilities reached up to 265% using the different slack models. DOI: 10.1061/(ASCE)0733-9402(2007)133:3(111) CE Database subject headings: Energy; Energy sources; Electric power loss; Electric power supply; Cost analysis.

Grid Computing is a promising infrastructure and technology that involves the integrated and collaborative use of Computers, networks, databases and scientific instruments owned and managed by multiple organizations. In this context our research primarily aims at developing an application framework for monitoring the Performance of Power Transmission and Distribution System using Grid Computing. Power Transmission and Distribution System of Electrical Network supplies power to millions of consumers. The demand for electrical energy is ever increasing. Today over 21% of the total electrical energy generated in India is lost in transmission and distribution. It is possible to bring down the distribution losses to the minimum level in India with the help of newer technological options in information technology called Grid Computing in the electrical power distribution sector which will enable better monitoring and control. By monitoring and controlling the parameters such as voltage, load, frequency and power factor in electrical power transmission and distribution systems the line loss will be reduced. When the Power factor is monitored using this Grid computing method, the Substations can maintain their norms by giving proper instructions to the operators dynamically to add the capacitor banks to maintain the power factor so that the line loss will be reduced and the revenue will automatically be increased. Key Words: Grid computing, Transmission and Distribution system, monitoring and control, Line loss, INTRODUCTION The Growth of the Internet, along with the availability of powerful computers and high-speed Networks as low-cost commodity components, is changing the way scientists and engineers do computing, and [...]

The aim of the Spanish voltage control ancillary service is the minimization of the transmission losses while keeping the system away from voltage instability. The latter target can be achieved maintaining an adequate voltage profile in normal operating condition and assuring that generators exhibit enough reactive margins that guarantee that the system voltages will remain under acceptable values in case of contingencies. The service has been designed in Spain to be partially mandatory and partially subject to payment based on market-driven rules and performance evaluation. In the annual time scope, the optional reactive offers submitted by the service suppliers are selected analyzing a number of forecasted scenarios. This paper explains the implementation of the Spanish voltage control ancillary service (VCAS) that is provided by generators in the annual time scope. For this purpose, a mixed-integer linear programming optimal power flow (OPF) is used. Reactive bids of generators are modeled within each scenario by modifying the reactive limits of the generators. The use of the proposed OPF in the assignment of the voltage control ancillary service is explained and illustrated using actual scenarios of the Spanish power system. Index Terms--Ancillary services (AS), linear programming (LP), optimal power flow (OPF), power loss reduction, reactive power dispatch, VAR/voltage control.

The introduction of distributed generation (DG) is leading to a fundamental change in how distribution networks are utilized and viewed. Distribution networks are now used as a means to connect geographically dispersed energy sources to the electricity system, thereby converting what were originally energy delivery networks, to networks used both for the delivery and harvesting of energy. This paper presents a methodology which maximizes the amount of energy that may be reaped from a given area, while taking account of the available energy resources, connection costs, losses, frequency of constraint breaches, and other technical constraints. The optimal energy allocation is determined for a sample section of network, illustrating the implementation of the methodology and the scope for non firm access to the distribution network. Index Terms--Dispersed storage and generation, energy resources, linear programming, losses, power distribution planning.

In rural power systems, the automatic voltage regulators (AVRs) help to reduce energy losses and to improve the energy quality of electric utilities, compensating the voltage drops through distribution fines. In order to help electric companies in the decision-making process, this paper presents a method to define the optimal location of a set of AVRs in electric distribution networks. The optimization process is treated as a multiobjective problem considering the total power losses and the voltage drops in the system as the objectives to be optimized. A novel technique called micro genetic algorithm ([micro]GA) is used to solve the multiobjective problem. This technique is capable of finding, in a very efficient way, the Pareto optimal solutions, giving the decision maker a set of possible (trade-off) solutions from which to choose. Index Terms--Evolutionary algorithms, losses, micro genetic algorithms, multiobjective optimization, optimization methods, power distribution, voltage control, voltage regulators.

Mathematical modeling for power dc-dc converters is a historical problem accompanying dc-dc conversion technology since the 1940s. The traditional mathematical modeling is not available for complex structure converters since the differential equation order increases very high. We have to search for other ways to establish mathematical modeling for power dc-dc converters. We have defined energy factor (EF) and new mathematical modeling for power dc--dc converters that have attracted much attention in recent years. This paper describes the small signal analysis of EF and mathematical modeling for power dc-dc converters in continuous conduction mode and discontinuous conduction mode. EF and the subsequential parameters can illustrate the unit-step response and interference recovery. This investigation may be helpful for system design and dc-dc converters characteristics. Two dc--dc converters: Buck converter and super-lift Luo-converter as the samples, are analyzed in this paper to demonstrate the applications of EF, pumping energy, stored energy (SE), capacitor/inductor SE ratio, energy losses, time constant r, and dumping time constant [[tau].sub.d]. Index Terms--Capacitor/inductor SE ratio (CIR), energy factor (EF), energy losses (EL), impulse response, mathematical modeling, pumping energy (PE), stored energy (SE), time constant [tau] and damping time constant [[tau].sub.d], unit-step response.

Nonsinusoidal voltage waveforms are quite common in high frequency power conversion magnetics. Low frequency nonsinusoidal waveforms are also common in ac motor applications with waveforms such as pulsewidth modulation and six-step. Previous attempts to model these losses, based on the Steinmetz equation, can work only in a limited range of frequencies, flux density excitations, and waveforms. In this paper, we present a very practical, yet very general and accurate model, for core loss calculations in case of nousinusoidal voltage waveforms. We show the model is equally applicable to low and high frequencies, metallic as well as nonmetallic (e.g., ferrites) core materials, by comparing the model prediction with measured data for various waveforms, frequencies, and flux densities. The model can be used for the design of high frequency transformers and inductors for use in switched mode power supplies. The model can also be used for ac motors where it is hard to estimate 'derating factor' and to avoid uncontrolled temperature rise. Index Terms--Pulsewidth modulation (PWM).

In this letter, we point out an ambiguity in the mathematical formulation of the optimization problem for the system loss using loss sensitivities treated in a recent IEEE publication and provide a concrete mathematical interpretation of the optimization procedure to clear up the ambiguity. Index Terms--Mathematical formulation, optimization, system loss.