Search

The isolated power system in Kinmen Island, Taiwan has already implemented the special protection system (SPS) to prevent various critical contingencies that occurred during the past decade. However, when a severe N-2 contingency occurred on July 26, 2013, the SPS has not properly armed its under-frequency load shedding. After reexamining transient recorded waveforms, it was observed that the system still has sufficient spinning reserve and the coordination between the under-frequency relay and the current SPS was not well considered. In this article, the current SPS is further modified in order to avoid the occurrence of the excessive load shedding under similar N-2 contingencies. Extensive time-domain dynamical simulations are performed first to study the relationship between the amount of the load shedding and frequency deviations under these extreme N-2 contingencies. Based on these simulation results, the remediation scheme of the SPS will be proposed by modifying the existing SPS design logic and the amount of load shedding. More comprehensive input triggered states are proposed for identifying these severe N-2 contingencies. Both simulation verifications under the proposed remedial scheme and actual transient recorded waveforms under a severe contingency after commissioning this remediated SPS are provided to demonstrate the effectiveness of this proposed remediation scheme. [ABSTRACT FROM AUTHOR]

This article develops, implements, and tests a method for selecting the locations and sizes of battery storage systems (BSSs) for power systems with distributed power generation. The developed method is based on calculating the coherency index for each bus to determine its contribution to the frequency of the center of inertia (COI) during and post a transient event. Once the coherency index is calculated for all buses, the principle component analysis (PCA) is used to identify the buses with consistent low values of the coherency index. These buses are considered as candidate locations for BSSs. In addition, the lowest values of the coherency index are used to determine the required sizes of BSSs to be connected at the buses with low contributions to the frequency of the COI. The performance of the PCA with COI (PCA-COI) method is evaluated for the Barbados power system for various transient events. Performance results show that BSSs (selected using the proposed method) can effectively improve the frequency stability with minor sensitivity to the levels of distributed power generation, loading levels, and/or type or location of transient events. [ABSTRACT FROM AUTHOR]

In this paper, the static and dynamic behaviors of a power system feeding an oil/gas plant with superconducting (SC) cables are investigated. SC cables have been expected to provide more efficient power supply and less space utilization for power systems compared to conventional cables. On the other hand, their compatibility with the existing power systems has not yet been clarified. In this paper, taking a typical distribution system in an oil/gas plant as an example, we designed high-voltage SC cables and investigated their compatibility with the system from the viewpoint of static and dynamic performances. The voltage distribution under steady-state operation and the transient voltage and current during fault conditions were examined and compared with the case of conventional cables. The results show that, in addition to the efficiency enhancement, SC cables could be applied without any further constraint on circuit breaker duties and insulation coordination requirements. [ABSTRACT FROM AUTHOR]

In order to enable voltage ride-through operation, fast and reliable voltage dips detection is necessary. It has been noticed by the analysis of a huge number of measurement results recorded in-field, in laboratory, and obtained by simulation that the voltage dips may be characterized by specific low-order voltage harmonics pattern, which appears at the beginning and at the end of the voltage dips. This feature is named harmonic footprint. This paper proposes a new method of voltage dips detection based on harmonic footprint as part of smart algorithm for detection and classification of power quality events. The aim is to achieve reliable smart voltage dips detection in 1 ms range. Several methods for harmonic estimation in real time were compared in order to choose the optimal one. The footprint is modeled by mathematical function and applied for voltage dips smart detection using recurrent neural network. The proposed method was tested for voltage dips detection analyzing signals from measurement in the real distribution grid (680 records), computer simulations using IEEE-13 bus test grid, and testing in the laboratory. The reliability (detection rate) and speed of voltage dips detection are tested and verified. Furthermore, the future research directions for presented method are outlined. [ABSTRACT FROM AUTHOR]

This paper presents the development and performance evaluation of a new approach for detecting voltage flicker events in power systems hosting distributed generating units. The proposed approach is based on extracting the magnitudes and phases of the different frequency sub-band contents present in the voltage signal(s). Desired magnitudes and phases are extracted by processing the voltage signal(s) using nine phaselet frames that are realized by a modulated filter bank. The modulated filter bank is designed using nine digital high-pass filters (HPFs), each of which implements one phaselet frame. The coefficients of HPFs are determined by bi-orthogonal phaselet basis functions. Extracted high-frequency sub-band contents provide signature information for accurate detection and quantification of voltage flickers. The performance of a phaselet transform based approach is experimentally tested for different conditions, including voltage flicker events that are triggered by an interconnected photovoltaic system. Performance results show accurate, reliable, and fast detection and quantification of voltage flickers, along with a negligible sensitivity to the source producing voltage flicker events. [ABSTRACT FROM AUTHOR]

Power quality (PQ) monitoring has been an important issue in smart grid (SG). PQ study involves the detection of the disturbances/events in different power system signals of the SG communication. Detecting disturbances in power system signals itself is a very difficult task and it becomes even more difficult when there are noises in the signal. The detection efficiency of the disturbances is highly downgraded by the noise, which corrupts the detection capability of the system, and hinders the localization and classification of the disturbances. In this work, a PQ monitoring system based on wavelet packet decomposition (WPD) is proposed to detect five different types of disturbances in the presence of noise. The proposed system utilizes the interscale and intrascale relationship of the WPD coefficients for the detection of the PQ disturbances upon noise removal. The correlation among the WPD coefficients exits both within its own scale and across its adjoining scales. For the evaluation, the presented method is applied both on the simulated and real SG disturbance signals obtained from frequency disturbance recorder (FDR), phasor measurement unit (PMU), and power system load. Comparative results are presented with wavelet decomposition. [ABSTRACT FROM AUTHOR]

Historically, failures of distribution transformers due to transient overvoltage phenomena have led to the development of resistor–capacitor snubber circuits for the protection of the transformer and winding insulation. These transients are most often observed when dry-type transformers are close coupled to vacuum switching devices. Typically, snubber circuit design has been specific for the particular application, and complex engineering studies were required. However, the design of a snubber circuit itself may be performed without these detailed studies. If snubber studies are required, the procedures for system modeling and simulation are explained in a step-by-step manner. [ABSTRACT FROM AUTHOR]

This is the second part of a two-paper series. The first paper presented the transient modeling methodology for various components of wind power plants (WPPs). This paper presents a general methodology for transient analysis of WPPs and discusses case studies which investigate some of the most important high-frequency interactions between different components of the WPP. The focus has been on switching transients, and lighting transients have been excluded. Transient case studies conducted on a typical WPP are presented which discuss the impact of fast system surges on the performance of the circuit breaker and impact of fast surges caused by the circuit breaker on the adjacent power components. These case studies investigate the opening and closing of the collector grid vacuum circuit breaker for loaded and unloaded conditions. Simulation results provide a close match with the field measurements conducted on a laboratory prototype of a typical WPP. Differences caused by modeling assumptions or insufficient accuracy of measurement devices are highlighted. To understand the most onerous overvoltages that can be experienced in the test system, a couple of additional simulation case studies are reported. These case studies discuss the interruption of inrush current with an unloaded transformer and interruption of a small inductive current following the transformer energization. [ABSTRACT FROM PUBLISHER]

This is the first part of a two-paper series and presents the modeling methodology for all of the main components of a typical wind power plant for power system transient studies. The models developed are intended for investigation of the temporary overvoltages, switching overvoltages, and lightning overvoltages. The component models developed include the high-frequency models of the vacuum and SF6 circuit breakers, three core cables for the collector grid, and quad core cables for the wind turbine tower, turbine transformer, doubly fed asynchronous generator, and surge arrester. The models developed are wideband in nature and can be used for all studies, except the transformer model which requires two variations for the low–mid frequency range and mid–high frequency range. Detailed user-defined models developed for both vacuum and SF6 circuit breakers take account of the restrikes, reignitions, prestrikes, low-frequency high-current interruption, and high-frequency low-current interruption. The generator and transformer transient models include a representation of the various high-frequency capacitive couplings. The success criteria for each individual component model are discussed, and the model performance is validated against these criteria. [ABSTRACT FROM AUTHOR]

The U.S. Navy is looking for methods to maximize the survivability of combat ships during battle conditions. A shipboard power distribution system is a stiff isolated power system that is vulnerable to voltage sags, which arise due to faults or pulsed loads, which can cause interruptions of critical loads. A series voltage injection type flywheel energy storage system (FESS) is used to mitigate voltage sags and maximize the survivability of the ship. The basic circuit consists of an energy storage system, power electronic interface, and a series injection transformer. In this case, the energy storage system consists of a flywheel coupled to an induction machine. The stored energy is used for sag correction for the critical load. Indirect field-oriented control (IDFOC) with space-vector pulsewidth modulation (SVPWM) is used to control the induction machine. Sinusoidal PWM is used for controlling the power system side converter. This paper presents the modeling, simulation, and analysis of a FESS with a power converter interface using PSCADIEMTDC. [ABSTRACT FROM AUTHOR]

A significant banter to improving, the power quality at industrial facilities is the lack of contemporaneous and historical power quality and reliability data. A new Web-enabled near-real-time power quality and reliability monitoring system, termed 1-Grid, has been developed to provide such information on a nationwide basis. The ultralow-cost sensors record power events and send event data via the Internet to the system database servers using an internal modem. Data display, e-mail event notification, site administration, and summary reporting of the data are achieved via a Web browser. In cooperation with the U.S. Department of Energy, the Electric Power Research Institute, and leading utilities and manufacturers, the deployment of these sensors has begun, with a target deployment of 50 000 monitors across the U.S. and Canada over the next 2-4 years. This paper discusses the implementation of this grid information resource, and discusses data captured by the network since early monitors were deployed in 2001. [ABSTRACT FROM AUTHOR]