Topic
Voltage regulation
About: Voltage regulation is a research topic. Over the lifetime, 35375 publications have been published within this topic receiving 472949 citations.
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TL;DR: In this paper, a new control method for the parallel operation of inverters operating in an island grid or connected to an infinite bus is described, where each inverter supplies a current that is the result of the voltage difference between a reference ac voltage source and the grid voltage across a virtual complex impedance.
Abstract: In this paper, a new control method for the parallel operation of inverters operating in an island grid or connected to an infinite bus is described. Frequency and voltage control, including mitigation of voltage harmonics, are achieved without the need for any common control circuitry or communication between inverters. Each inverter supplies a current that is the result of the voltage difference between a reference ac voltage source and the grid voltage across a virtual complex impedance. The reference ac voltage source is synchronized with the grid, with a phase shift, depending on the difference between rated and actual grid frequency. A detailed analysis shows that this approach has a superior behavior compared to existing methods, regarding the mitigation of voltage harmonics, short-circuit behavior and the effectiveness of the frequency and voltage control, as it takes the R to X line impedance ratio into account. Experiments show the behavior of the method for an inverter feeding a highly nonlinear load and during the connection of two parallel inverters in operation.
1,528 citations
TL;DR: In this article, two types of pulsewidth-modulated modular multilevel converters (PWM-MMCs) with focus on their circuit configurations and voltage balancing control are investigated.
Abstract: A modular multilevel converter (MMC) is one of the next-generation multilevel converters intended for high- or medium-voltage power conversion without transformers. The MMC is based on cascade connection of multiple bidirectional chopper-cells per leg, thus requiring voltage-balancing control of the multiple floating DC capacitors. However, no paper has made an explicit discussion on voltage-balancing control with theoretical and experimental verifications. This paper deals with two types of pulsewidth-modulated modular multilevel converters (PWM- MMCs) with focus on their circuit configurations and voltage-balancing control. Combination of averaging and balancing controls enables the PWM-MMCs to achieve voltage balancing without any external circuit. The viability of the PWM-MMCs, as well as the effectiveness of the voltage-balancing control, is confirmed by simulation and experiment.
1,506 citations
TL;DR: In this paper, the authors extend the Dommel-Tinney approach by incorporating exact outage-contingency constraints into the method, to give an optimal steady-state-secure system operating point.
Abstract: The Dommel-Tinney approach to the calculation of optimal power-system load flows has proved to be very powerful and general. This paper extends the problem formulation and solution scheme by incorporating exact outage-contingency constraints into the method, to give an optimal steady-state-secure system operating point. The controllable system quantities in the base-case problem (e.g. generated MW, controlled voltage magnitudes, transformer taps) are optimised within their limits according to some defined objective, so that no limit-violations on other quantities (e. g. generator MVAR and current loadings, transmission-circuit loadings, load-bus voltage magnitudes, angular displacements) occur in either the base-case or contingency-case system operating conditions.
1,487 citations
Book•
31 Aug 2001TL;DR: In this paper, the authors present an approximate method of analysis Voltage Drop Line Impedance K Factors Uniformly Distributed Loads Lumping Loads in Geometric Configurations.
Abstract: Introduction to Distribution Systems The Distribution System Distribution Substations Radial Feeders Distribution Feeder Map Distribution Feeder Electrical Characteristics Summary The Nature of Loads Definitions Individual Customer Load Distribution Transformer Loading Feeder Load Summary Approximate Method of Analysis Voltage Drop Line Impedance K Factors Uniformly Distributed Loads Lumping Loads in Geometric Configurations Summary References Series Impedance of Overhead and Underground Lines Series Impedance of Overhead Lines Series Impedance of Underground Lines Series Impedances of Parallel Lines Summary References Shunt Admittance of Overhead and Underground Lines General Voltage Drop Equation Overhead Lines Concentric Neutral Cable Underground Lines Tape-Shielded Cable Underground Lines Sequence Admittance The Shunt Admittance of Parallel Underground Lines Summary References Distribution System Line Models Exact Line Segment Model The Modified Line Model The Approximate Line Segment Model The General Matrices for Parallel Lines Summary References Voltage Regulation Standard Voltage Ratings Two-Winding Transformer Theory Two-Winding Autotransformer Step-Voltage Regulators Summary References Three-Phase Transformer Models Introduction Generalized Matrices The Delta-Grounded Wye Step-Down Connection The Ungrounded Wye-Delta Step-Down Connection The Grounded Wye--Grounded Wye Connection The Delta-Delta Connection Open Wye--Open Delta Thevenin Equivalent Circuit Summary Load Models Wye Connected Loads Delta Connected Loads Two-Phase and Single-Phase Loads Shunt Capacitors The Three-Phase Induction Machine Summary References Distribution Feeder Analysis Power-Flow Analysis Short-Circuit Studies Summary References Center-Tapped Transformers and Secondaries Center-Tapped Single-Phase Transformer Model Ungrounded Wye-Delta Transformer Bank Leading Open Wye--Open Delta Transformer Connection Lagging Open Wye--Open Delta Connection Four-Wire Secondary Putting It All Together Summary Reference Appendix A Appendix B Index
1,449 citations
TL;DR: In this paper, a nonlinear programming problem for capacitors placed on a radial distribution system is formulated and a solution algorithm is developed to find the optimal size of capacitors so that the power losses will be minimized for a given load profile while considering the cost of the capacitors.
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. >
1,391 citations