Operation Of Electric Distribution Systems Research Articles

Impact of widespread photovoltaics generation on distribution systems

Prompted by the need for clean energy sources, increasing numbers of photovoltaic (PV) generators are being connected to electricity distribution systems around the world. There is thus a growing imperative to understand and quantify the technical impact that high penetrations of such generators may have on the operation and performance of electricity distribution systems. Detailed simulations of a very high penetration of PV within a typical UK urban distribution network (11 kV, 400 V and 230 V) are reported. The study performed unbalanced three-phase load-flow analysis on an entire feeder within a time-domain simulation framework using load and generation data at 1 minute intervals. The results indicate that even at very high penetrations of PV, network voltage rises are small and unlikely to cause problems. Effects on network power flows and losses are also quantified and discussed

Utilização de computação móvel para qualificação de rotinas de operação e manutenção de redes de distribuição

O objetivo deste artigo é discutir a utilização de um conjunto de tecnologias de computação móvel (Mobile Computing) para auxílio nas rotinas de planejamento da operação e manutenção de sistemas de distribuição de energia elétrica. Apresenta-se um resumo das principais tecnologias, discutindo-se definições, serviços e aplicações em potencial na área de sistemas de energia. Para ilustrar o artigo é apresentado um caso de utilização prática da tecnologia de Personal Digital Assistant - PDA, para coleta e validação de dados de eventos não programados em sistemas de distribuição, um sistema para auxílio de rotinas de inspeção e manutenção em redes de distribuição e um sistema de comunicação de dados via telefonia celular para uma pequena central hidrelétrica.

Integration of multiple PV units in urban power distribution systems

The amount of power and energy that can be injected into the distribution system by dispersed generation (DG) is constrained by technical issues related to electrical components rating and distribution system operation. In this context, the aim of the paper is to study the voltage profile of a LV feeder in order to assess the maximum value of the power that can be injected into multiple load points of the feeder by PV units without violating the voltage constraints. To perform this study an analytical method with integral approach is used: the distribution of generators and loads along the feeder is represented by means of continuous functions and constant current model. The main result of the proposed study is that, with reference to a set of contiguous generation units, it is possible to derive analytical relationships between the position of the point of maximum/minimum voltage on the feeder and the characteristics of the distributed generation (e.g. length of the concerned feeder portion, position of the generators and overall current injected by the generators).

The effect of variable-speed wind turbines on the operation of weak distribution networks

This paper analyzes the repercussions from the connection of wind parks (WPs) on the operation of weak electric distribution systems, based on simulation results. The effects on the voltage profile caused by variable-speed (VS) wind turbines (WTs) are compared to the effects caused by fixed-speed (FS) WTs. Both types of WTs are assumed to be equipped with asynchronous machines. In the VS mode of operation, a voltage-source converter cascade is used, employing field-oriented control for the generator-side converter and three independent hysteresis controllers for the grid-side converter. The distribution system studied is an actual feeder located in a rural area at the southeastern part of mainland Greece. For the simulation of the WP and the grid a library of WTs, electrical grid components were developed. By using the developed simulation tool, two cases concerning high and low wind speed are studied. General conclusions are drawn concerning the voltage fluctuations, harmonic content, and the penetration of harmonics through the network. The advantages of the studied VS operation scheme are confirmed and the possible increase in the installed capacity of the WP over the FS mode, maintaining the same power quality standards, is estimated.

Comparison between Types of Generation for Wind Turbines Operating in Stochastic Wind

This paper analyses the repercussions from the connection of Wind Parks on the operation of weak electricity distribution systems, based on simulation results. Three different cases concerning Fixed Speed Wind Turbines are studied. Also Variable Speed Wind Turbines are examined, using (i), doubly-fed induction machines, and (ii), a dual voltage-source converter cascade. All these types of wind turbines are assumed to be equipped with asynchronous machines. The effects on the voltage profile caused by both Fixed and Variable Speed Wind Turbines are compared. The advantages of the variable speed operation are confirmed. The possible increase in the installed capacity of a Wind Park with variable speed turbines, as compared with fixed speed turbines maintaining the same power quality standards, is estimated. The distribution system studied is an actual feeder located in a rural area at the southeast of mainland Greece. This area presents excellent wind potential and as a result independent power producers have expressed a considerable interest for the installation of Wind Parks.

The Effect of Variable Speed Wind Turbines on the Operation of Weak Distribution Networks

This paper analyzes the repercussions from the connection of wind parks (WPs) on the operation of weak electric distribution systems, based on simulation results. The effects on the voltage profile caused by variable-speed (VS) wind turbines (WTs) are compared to the effects caused by fixed-speed (FS) WTs. Both types of WTs are assumed to be equipped with asynchronous machines. In the VS mode of operation, a voltage-source converter cascade is used, employing field-oriented control for the generator-side converter and three independent hysteresis controllers for the grid-side converter. The distribution system studied is an actual feeder located in a rural area at the southeastern part of mainland Greece. For the simulation of the WP and the grid a library of WTs, electrical grid components were developed. By using the developed simulation tool, two cases concerning high and low wind speed are studied. General conclusions are drawn concerning the voltage fluctuations, harmonic content, and the penetration of harmonics through the network. The advantages of the studied VS operation scheme are confirmed and the possible increase in the installed capacity of the WP over the FS mode, maintaining the same power quality standards, is estimated.

A Graph Oriented Knowledge-Based System to Assist Restoration of Distribution Systems

This paper describes a knowledge-based system designed to assist electrical distribution system operators in restoring the network after a fault. A hybrid approach that links symbolic and numerical computation algorithms is proposed. Features that depend on system operators’ experience and norms of the utiIity arc included in a knowledge base. The reasoning process is guided by an inference engine with backward chaining strategy. Electrical overload checks are carried out by a simulator based on the method of momentums. The adoption of concepts and data structure borrowed from network flow algorithms leads to the development of a very effcient procedure.

Magnetic amplifier step regulator

PROPER VOLTAGE regulation is now becoming an increasingly important factor in efficient operation of electric power distribution systems. The degree to which a voltage regulator performs its function on these systems depends upon the accuracy and reliability of its controls. Because of fluctuating voltage conditions on most systems, the voltage-regulating and time-delay elements of the controls are subjected to many more operations than the regulator itself. A new control system has been developed employing the unique features of bistable magnetic amplifiers to perform the functions of the voltage regulating and time delay elements.