J.J. Grainger

Bio: J.J. Grainger is an academic researcher from North Carolina State University. The author has contributed to research in topics: Voltage regulator & Voltage regulation. The author has an hindex of 6, co-authored 6 publications receiving 2225 citations.

Distribution feeder reconfiguration for loss reduction

Abstract: Feeder reconfiguration is defined as altering the topological structures of distribution feeders by changing the open/closed states of the sectionalizing and tie switches. A scheme is presented that utilizes feeder reconfiguration as a planning and/or real-time control tool to restructure the primary feeder for loss reduction. The mathematical foundation of the scheme is given. The solution is illustrated on simple examples. >

Optimum Size and Location of Shunt Capacitors for Reduction of Losses on Distribution Feeders

Abstract: New generalized procedures are developed for optimizing the net savings associated with reduction of power and energy losses through shunt capacitor placement on primary distribution feeders. These procedures are applied to realistic problems to facilitate their immediate use by the electric utility distribution system designer. It is shown that a basic principle, called here "The Equal Area Criterion", offers significant computational and physical insight into numerous problems outside the bounds of studies previously reported and widely accepted in industry

Volt/Var Control on Distribution Systems with Lateral Branches Using Shunt Capacitors and Voltage Regulators Part I: The Overall Problem

Abstract: In this paper (Part I) and two companion papers (Part II and Part III) the problem of volt/var control on general radial distribution systems is formulated, simplified and solved. The objective is to minimize the peak power and energy losses while keeping the voltage within specified limits under varying load conditions. The decision variables to be optimally determined are (i) the locations, sizes and the real-time control of the specified number of ON/OFF switched and fixed capacitors and (ii) the locations and real-time control of the minimum number of voltage regulators. It is shown in this paper (Part I) that the regulator (volt) and the capacitor (var) problem may be treated as two decoupled problems. Part II of this set of three papers, conjoined with Part 1. provides the analytical tools by which optimal solutions for both problems may be determined. Application of the theory to representative radial systems is shown in Part III whhich also illustrates the economic benefits and numerical results achievable through both regulation and compensation schemes.

Volt/Var Control on Distribution Systems with Lateral Branches Using Shunt Capacitors and Voltage Regulators Part III: The Numerical Results

Abstract: In this paper, the numerical results obtained through the application of the optimal design and control schemes of the capacitor and voltage regulator problems (which are formulated and solved on an analytical basis in the previous paper, Parts I and II) are demonstrated on a thirty-bus test system with six lateral branches. The results are discussed in order to demonstrate the applicability of the theory and the bases underlying the modeling of the overall problem.

Optimum Placement of Fixed and Switched Capacitors on Primary Distribution Feeders

Abstract: New generalized procedures are developed for optimizing the net monetary savings associated with the reduction of power and energy losses through placement of fixed and switched shunt capacitors on primary distribution feeders. The computer-based optimization techniques are structured around three subproblems which encompass a wide range of design problems of interest to the distribution engineer. Realistic reactive load distributions on nonuniform feeders of commonly encountered wire sizes are accommodated within the modeling. A wide range of numerical examples is presented to reflect net dollar savings for typical applications

Network reconfiguration in distribution systems for loss reduction and load balancing

Abstract: A general formulation of the feeder reconfiguration problem for loss reduction and load balancing is given, and a novel solution method is presented. The solution uses a search over different radial configurations created by considering switchings of the branch exchange type. To guide the search, two different power flow approximation methods with varying degrees of accuracy have been developed and tested. The methods are used to calculate the new power flow in the system after a branch exchange and they make use of the power flow equations developed for radial distribution systems. Both accuracy analysis and the test results show that estimation methods can be used in searches to reconfigure a given system even if the system is not well compensated and reconfiguring involves load transfer between different substations. For load balancing, a load balance index is defined and it is shown that the search and power flow estimation methods developed for power loss reduction can also be used for load balancing since the two problems are similar. >

Optimal capacitor placement on radial distribution systems

Abstract: The problem of capacitor placement on a radial distribution system is formulated and a solution algorithm is proposed. The location, type, and size of capacitors, voltage constraints, and load variations are considered. The objective of capacitor placement is peak power and energy loss reduction, taking into account the cost of the capacitors. The problem is formulated as a mixed integer programming problem. The power flows in the system are explicitly represented, and the voltage constraints are incorporated. A solution method has been implemented that decomposes the problem into a master problem and a slave problem. The master problem is used to determine the location of the capacitors. The slave problem is used by the master problem to determine the type and size of the capacitors placed on the system. In solving the slave problem, and efficient phase I-phase II algorithm is used. >

Optimal sizing of capacitors placed on a radial distribution system

Abstract: A capacitor sizing problem for capacitors placed on a radial distribution system is formulated as a nonlinear programming problem, and a solution algorithm is developed. The object is to find the optimal size of the capacitors so that the power losses will be minimized for a given load profile while considering the cost of the capacitors. The formulation also incorporates the AC power flow model for the system and the voltage constraints. The solution algorithm developed for the capacitor sizing problem is based on a Phase I-Phase II feasible directions approach. Novel power flow equations and a solution method, called DistFlow, for radial distribution systems are introduced. The method is computationally efficient and numerically robust, especially for distribution systems with large r/x ratio branches. DistFlow is used repeatedly as a subroutine in the optimization algorithm for the capacitor sizing problem. The test results for the algorithm indicate that the method is computationally efficient and has good convergence characteristics. >

Real-Time Coordination of Plug-In Electric Vehicle Charging in Smart Grids to Minimize Power Losses and Improve Voltage Profile

Abstract: This paper proposes a novel load management solution for coordinating the charging of multiple plug-in electric vehicles (PEVs) in a smart grid system. Utilities are becoming concerned about the potential stresses, performance degradations and overloads that may occur in distribution systems with multiple domestic PEV charging activities. Uncontrolled and random PEV charging can cause increased power losses, overloads and voltage fluctuations, which are all detrimental to the reliability and security of newly developing smart grids. Therefore, a real-time smart load management (RT-SLM) control strategy is proposed and developed for the coordination of PEV charging based on real-time (e.g., every 5 min) minimization of total cost of generating the energy plus the associated grid energy losses. The approach reduces generation cost by incorporating time-varying market energy prices and PEV owner preferred charging time zones based on priority selection. The RT-SLM algorithm appropriately considers random plug-in of PEVs and utilizes the maximum sensitivities selection (MSS) optimization. This approach enables PEVs to begin charging as soon as possible considering priority-charging time zones while complying with network operation criteria (such as losses, generation limits, and voltage profile). Simulation results are presented to demonstrate the performance of SLM for the modified IEEE 23 kV distribution system connected to several low voltage residential networks populated with PEVs.

Reconfiguration of electric distribution networks for resistive line losses reduction

Abstract: The authors describe a heuristic method for the reconfiguration of distribution networks in order to reduce their resistive line losses under normal operating conditions. The proposed approach is characterized by convergence to the optimum or a near-optimum solution and the independence of the final solution from the initial status of the network switches. The methodology has been implemented in a production-grade computer program, DISTOP (Distribution Network Optimization). The compensation-based power flow technique developed at Pacific Gas and Electric Company for the efficient solution of weakly meshed distribution networks is an essential part of this loss reduction methodology. Important implementation aspects of the methodology and the results of its application to several realistic distribution networks are presented. Numerous test results have indicated that the proposed technique is computationally robust and efficient and, hence, suitable for both planning and operations studies. >