Showing papers on "Islanding published in 1998"

Anti-islanding method and apparatus for distributed power generation

Abstract: The invention in the simplest form is a method and apparatus for reliably protecting against island situations with one or multiple power sources connected to an electric distribution grid. The method and apparatus detects variations in the voltage and frequency of the grid. An observed change in grid voltage causes a change in output power that is sufficient to cause an even larger change in grid voltage when the utility AC power source is disconnected. An observed change in grid frequency causes a change in phase or reactive output power that is sufficient to cause an even larger change in grid frequency. If several shifts in voltage or frequency happen in the same direction, the response to the change is increased in an accelerating manner.

Application of STATCOMs to wind farms

Abstract: Effective reactive power control in distribution networks can have an important influence on the level of embedded generation that is acceptable and on the costs of its connection. A comprehensive study was undertaken to investigate how STATCOMs could be used with fixed-speed wind turbines, which use induction generators, to improve both the steady-state and dynamic impact of a wind farm on the network. An optimal power flow model based on loss minimisation was developed and used to show that operation of a wind farm at unity power factor is unlikely to allow maximum penetration of wind energy into a weak distribution circuit. The results of the electromagnetic simulations showed that the use of a STATCOM improves the steady-state stability limits of the network. They also showed that the use of a STATCOM with an appropriately designed control strategy can prevent damaging overvoltages that may occur under islanding conditions. The results also demonstrated that a STATCOM can be used to mitigate voltage fluctuations at blade passing frequency, which may occur if the rotors of a number of wind turbines fall into synchronism.

Management and dynamic performances of combined cycle power plants during parallel and islanding operation

Abstract: The subject of a cogeneration plant modeling has already been discussed in the past, but mostly from the thermal and energy point of view. There are several aspects to be considered for assuring that the plant will operate satisfactorily. Furthermore, the increasing number of energy producers poses more and more attention to these types of plants and to their regulation mode. Among these aspects, particular care is devoted in this paper to the modeling and setting-up of gas turbine regulators, also because it is not generally such a trivial work to adapt existing software for large power systems' dynamic analysis to the requirements of combined-cycle power plants. On the basis of the specialized literature, a detailed model for the regulator of a gas turbine unit is adopted, which includes speed, acceleration and temperature controls as well as inlet guide vanes' control. The proposed regulator is tested on a realistic industrial power plant with particular attention to parallel and isolated operation.

Determining the Sufficiency of Standard Protective Relaying for Islanding Prevention in Grid-Connected PV Systems

Abstract: Presented at the 2nd World Conference on Photovoltaic Solar Energy Conversion; Vienna, Austria; July 6-10, 1998.

Individual operation prevention device of inverter for coordinating system

Abstract: PROBLEM TO BE SOLVED: To quickly and accurately detect an islanding phenomenon and to suppress the voltage and power factor fluctuation of a consumer service wire by setting a reactive power fluctuation command to zero, when a power reception point power value becomes a power reception side for the power system SOLUTION: The DC power of a DC power supply 2 is converted into an AC power, that is matched to the frequency and voltage of a system by an inverter 3 and is supplied to a load 5 via circuit breakers 6 and 7 Then, when an islanding phenomenon in which switcher at the side of the power system 14 is released occurs, a frequency fluctuates due to the reactive power fluctuation of the inverter 3 and a frequency signal (c) of a voltage/frequency converter 11 fluctuates from a rated value Consequently, a comparator operates and an OR gate is turned on, a relay is excited and a trip signal (a) is set In this case, a frequency detection level by the comparator is one step each, thus preventing a detection time from being extended long Also, since the parallel-off circuit breaker 6 a line is released and the line of a generation device 1 is undone, an islanding state is eliminated immediately

Integration of distributed resources in electric utility systems: Current interconnection practice and unified approach. Final report

Abstract: Deregulation of the electric utility industry, new state and federal programs, and technology developments are making distributed resources (DR) an increasingly utilized option to provide capacity for growing or heavily loaded electric power systems. Optimal DR placement near loads provides benefits not attainable from bulk generation system additions. These include reduced loading of the T and D system, reduced losses, voltage support, and T and D equipment upgrade deferments. The purpose of this document is to review existing interconnection practices and present interconnection guidelines are relevant to the protection, control, and data acquisition requirements for the interconnection of distributed resources to the utility system. This is to include protection performance requirements, data collection and reporting requirements, on-line communication requirements, and ongoing periodic documentation requirements. This document also provides guidelines for the practical placement and sizing of resources as pertinent to determining the interconnection equipment and system control requirements. The material contained herein has been organized into 4 sections dealing with application issues, existing practices, a unified interconnection approach, and future work. Section 2 of the report discusses the application issues associated with distributed resources and deals with various engineering issues such as overcurrent protection, voltage regulation, and islanding. Section 3more » summarizes the existing utility interconnection practices and guidelines as determined from the documents provided by participating utilities. Section 4 presents a unified interconnection approach that is intended to serve as a guide for interconnection of distributed resources to the utility system. And finally, Section 5 outlines possible future areas of study to expand upon the topics discussed in this report.« less