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Showing papers on "Islanding published in 1989"


Journal ArticleDOI
TL;DR: In this paper, a detailed account of analytical work carried out to determine the parameters of power system stabilizers (PSS) for the Darlington nuclear generating station presently under construction in eastern Ontario is presented.
Abstract: This paper provides a detailed account of analytical work carried out to determine the parameters of power system stabilizers (PSS) for the Darlington nuclear generating station presently under construction in eastern Ontario. The results presented are, however, of general interest and provide a comprehensive analysis of the effects of the different stabilizer parameters on the overall dynamic performance of the power system. They show how stabilizer settings may be selected so as to enhance the steady-state and transient stability of local plant modes as well as inter-area modes in large interconnected systems. In addition, it is shown that the selected parameters result in satisfactory performance during system islanding conditions, when large frequency excursions are experienced. Darlington GS, when completed by 1992, will comprise four 1100 MVA, 0.85 p.f., 1800 RPM turbine generators with "CANDU-PHW" reactors, moderated and cooled by heavy water. The station will be incorporated into the 500 kV network through three double-circuit lines. The units will be equipped with transformer-fed thyristor excitation systems and Delta-P-Omega type PSS [1, 2].

854 citations


Journal ArticleDOI
Abstract: This paper provides a self-healing strategy to deal with catastrophic events when power system vulnerability analysis indicates that the system is approaching an extreme emergency state. The system is adaptively divided into smaller islands with consideration of quick restoration. Then an adaptive load shedding scheme based on the rate of frequency decline is applied. The proposed scheme is tested on a 179-bus, 20-generator sample system and shows very good performance.

181 citations


Journal ArticleDOI
TL;DR: In this article, the authors presented simplified computer models for predicting the run-on time of self-commutated inverters operating in a utility interactive mode, where the inverter receives DC power from a photovoltaic (PV) array and delivers AC power to a local load or the utility lines.
Abstract: Simplified computer models are presented for predicting the run-on time of self-commutated inverters operating in a utility interactive mode. The inverter receives DC power from a photovoltaic (PV) array and delivers AC power to a local load or the utility lines. The models represent the dynamics of a phase-locked loop control circuit that is designed to destabilize the inverter operation and shut down the power-conditioning subsystem when a phase discrepancy between the line and some reference signal is detected. The sustained isolated operation (or islanding) of the PV system poses a possible safety concern to utility personnel and potential damage to utility-connected equipment. Two computer models, the TESLACO model and the APCC model, were implemented on an IBM PC using Pascal. They provide results compatible with experimental evidence and more elaborate computer modeling techniques. >

57 citations


Journal ArticleDOI
TL;DR: In this article, the authors developed simple analytical methods to determine if islanding is possible in a system consisting of one or more Power Conditioning System (PCSs) connected to a single-phase distribution lateral.
Abstract: Residential, utility-interactive, photovoltaic systems consist of a photovoltaic (PV) array, and a Power Conditioning System (PCS), or inverter, which converts the dc array energy to an ac voltage or current at the proper frequency for connection to an electric utility distribution feeder. One of the concerns wth such an interconnection is the potential for "islanding." This is a phenomenon in which one or more PCSs continue to operate, and keep the system energized even after the utility supply is disconnected. The loss of utility may be related to a scheduled outage, or the operation of circuit breakers, sectionalizers, or fuses in response to a system disturbance. Since the electric utility company cannot exert direct control on residential photovoltaic systems, islanding is generally considered to be undesirable. Concern is primarily related to the safety of personnel attempting to restore service in a system energized by islanded PCSs. Additionally, there is cause for concern as to the effect of transients and off-nominal frequency and/or voltage on connected load and on the PCS itself. Therefore, an understanding of the islanding problem is extremely important to the commercialization of utility-interactive PV systems. The objective of the work described in this paper and its companion [1] is to develop simple analytical methods to determine if islanding is possible in a system consisting of one or more PCSs connected to a single-phase distribution lateral. Attention is focused on three commercially available PCSs, the 'Gemini' manufactured by Windworks, Inc., the 'Teslaco' manufactured by Teslaco, Inc.

30 citations


Journal ArticleDOI
01 Sep 1989
TL;DR: In this paper, models and methods for the analysis of this phenomenon are presented and used in a companion paper to explore the possibility of islanding in practical photovoltaic systems.
Abstract: Islanding is the continued operation of a group of utility-connected photovoltaic systems even after loss of the utility source. Such operation can be hazardous to both utility personnel as well as to components in the system. Models and methods for the analysis of this phenomenon are presented in this paper. The methods are used in a companion paper to explore the possibility of islanding in practical systems. Although all such systems have a natural propensity to island, it is shown that the controls used in many commercially available units make islanding a rather unlikely phenomenon.

27 citations


Journal ArticleDOI
TL;DR: In this paper, the authors describe problems associated with the performance characteristics of nuclear generating stations which do not have their overall unit control design functions co-ordinated with the other grid controls.
Abstract: This paper describes problems associated with the performance characteristics of nuclear generating stations which do not have their overall plant control design functions co-ordinated with the other grid controls. Some design changes to typical nuclear plant controls are presented which can result in a significant improvement in both the performance of the grid island and reduce the need to isolate nuclear units during the disturbance. Four areas of the overall unit controls and turbine governor controls which could be modified to better co-ordinate the control functions of the nuclear units with the electrical grid are discussed. Some simulation results are presented to show the performance of a typical electrical grid island containing a nuclear unit with and without the changes. By reviewing data from two islanding events and supplementing that with computer simulation studies, some conclusions are made. The first of these is that overall unit controllers which are not designed with grid disturbances and islanding requirements in mind can cause frequency control problems. On detection of grid islanding the turbine power should be regulated by the speed governor only while the overall unit controls maintain appropriate operation of the reactor and steam bypass system. As well, turbine auxiliary governors whose settings and time delays are not co-ordinated with the operation of the main governors and underfrequency load shedding relays on the system can cause frequency oscillation and limit cycles. Turbine auxiliary governor design and settings should be co-ordinated with other grid controls, including other unit governors.

17 citations


Journal ArticleDOI
TL;DR: In this paper, the authors extended the analysis of power flow analysis to the case of multiple power conditioning systems (PCS) and defined models for power-flow analysis, describing functions analysis and small-signal stability analysis.
Abstract: The phenomenon wherein a group of residential, utility-connected, photovoltaic inverters continue to operate even after loss of the utility source is known as 'islanding.' Islanded operation is undesirable since it can jeopardize the safety of utility personnel as well as cause damage to connected equipment. Analytical methods for the study of islanding have been presented in the companion paper [1]. It has been shown therein that a power-flow analysis type of method can be effectively used to identify the electrical frequency at which a power balance can be achieved in an islanded system. If such a frequency exists then islanding is possible. At this predicted frequency, largesignal Describing Function analysis and small-signal stability analysis can be used to determine if islanding will actually occur. In the present paper the methods are extended to the analysis of systems containing multiple power conditioning systems (PCS). Beginning with a general state-variable format, models are defined for power-flow analysis, describing functions analysis, and small-signal stability analysis. The methods above are used to study islanding in several test systems. Three types of PCSs are studied-the Gemini manufactured by Windworks, Inc., the Teslaco manufactured by Teslaco, Inc., and

15 citations


Journal ArticleDOI
TL;DR: In this paper, the development of a model for a commercially available self-commutated static power converter (SPC) to investigate the conditions under which isolated operation (islanding) occurs is described.
Abstract: The development of a model for a commercially available self-commutated static power converter (SPC) to investigate the conditions under which isolated operation (islanding) occurs is described. The approach used in modeling the SPC is unique in islanding studies. It is based on solving complex-AC system equations and phase-locked loop differential equations simultaneously to determine the SPC response. The model accurately and optimistically predicts the islanding performance of the self-commutated SPC, as verified in laboratory experiments and detailed computer simulations. >

9 citations




Dissertation
01 Jan 1989
TL;DR: In this article, a real-time power systems simulator is used to test the algorithms and numerical results obtained by the authors in their paper "Assessment of security of power systems in realtime operation", where the main objective is to develop a package to be incorporated in the University of Durham On line Control of Electrical Power Systems (OCEPS) suite to cater for network islanding and analyse the features and the feasibility of a realtime'security package' for modern energy control centers.
Abstract: The increasing complexity of modern power systems has led to a greater dependence on automatic control at all levels of operation. Large scale systems of which a power system is a prime example, is an area in which a wide gap exists between theoretical mathematically based research and engineering practice. The research programme at Durham is directed towards bridging this gap by linking some of the available and new theoretical techniques with the practical requirements of on-line computer control in power systems. This thesis is concerned with the assessment of security of power systems in real-time operation. The main objective of this work was to develop a package to be incorporated in the University of Durham On line Control of Electrical Power Systems (OCEPS) suite to cater for network islanding and analyse the features and the feasibility of a real-time 'security package’ for modern energy control centres. The real-time power systems simulator developed at Durham was used to test the algorithms and numerical results obtained are presented.

Journal ArticleDOI
TL;DR: In this paper, the authors describe a power system simulation and energy management system with particular reference to operation under dynamic conditions, with particular emphasis on the performance of the simulation, analysis and control algorithms during emergency conditions.

Book ChapterDOI
V.F. Carvalho1, P.N. Acchione1
01 Jan 1989
TL;DR: In this article, the overall unit control (relative to the need from a grid viewpoint) of nuclear units in Ontario Hydro and examines their response during grid emergencies including frequency control, system islanding and restoration.
Abstract: This paper describes overall unit control (relative to the need from a grid viewpoint) of nuclear units in Ontario Hydro and examines their response during grid emergencies including frequency control, system islanding and restoration. Proposed design modifications to Improve nuclear unit participation are outlined. Recordings from a System disturbance are used to illustrate power plant controls under nuclear unit islanding conditions. Key Words. Power System Control; Frequency Control; Dynamic Stability; Integrated Plant Control.