Power System Quantities Research Articles

Modeling and Simulation of a Large-Scale Wind Power Plant Considering Grid Code Requirements

The load demand to a power grid, as well as the interest in clean and low-cost energy resources, has led to the high integration of wind power plants into power system grids. There are grid code standards that are set for the design and integration of these wind power plants. These codes often look at the design operation of the wind power plant in islanded mode, where possible analysis of the most sensitive power system quantities such as voltage, frequency, reactive power, etc. is carried out. Therefore, in this study, attention was paid to the application of these codes to keep the design and integration of wind power plants well standardized as much as possible. The purpose of this paper is to review and discuss the literature and theory about the design of wind turbine generators and model and simulate a large-scale wind power plant. The modeling was successfully carried out on RSCAD, and the results obtained show that the wind power plant can be further used for other studies such as voltage stability improvement in power grids.

Space Vector Taylor–Fourier Models for Synchrophasor, Frequency, and ROCOF Measurements in Three-Phase Systems

Taylor–Fourier (TF) filters represent a powerful tool to design phasor measurement unit (PMU) algorithms able to estimate synchrophasor, frequency, and rate of change of frequency (ROCOF). The resulting techniques are based on dynamic representations of the synchrophasor, and hence, they are particularly suitable to track the evolution of its parameters during time-varying conditions. Electrical quantities in power systems are typically three-phase and weakly unbalanced, but most PMU measurement techniques are developed by considering them as a set of three single-phase signals; on the contrary, this peculiarity can be favorably exploited to improve accuracy and reduce the computational cost. In this respect, this paper proposes to directly perform the TF expansion of the space vector (SV) samples obtained from three-phase measurements. A new paradigm allows to independently estimate positive and negative sequence synchrophasors along with system frequency and ROCOF, leveraging the three-phase characteristics. The performance of the proposed technique is assessed by using test signals inspired by the standard IEEE C37.118.1-2011, including noise as well as magnitude and phase unbalance. Achieved results highlight the flexibility of the enhanced SV-based approach, which is capable to combine excellent dynamic performance together with an accurate estimation of both positive and negative sequence components.

Evaluation of Harmonics Impact on Digital Relays

This paper presents the concept of the impact of harmonic distortion on a digital protection relay. The aim is to verify and determine the reasons of a mal-trip or failure to trip the protection relays; the suggested solution of the harmonic distortion is explained by a mathematical model in the Matlab Simulink programming environment. The digital relays have been tested under harmonic distortions in order to verify the function of the relays algorithm under abnormal conditions. The comparison between the protection relay algorithm under abnormal conditions and a mathematical model in the Matlab Simulink programming environment based on injected harmonics of high values is provided. The test is separated into different levels; the first level is based on the harmonic effect of an individual harmonic and mixed harmonics. The test includes the effect of the harmonics in the location of the fault point into distance protection zones. This paper is a new proposal in the signal processing of power quality disturbances using Matlab Simulink and the power quality impact on the measurements of the power system quantities; the test simulates the function of protection in power systems in terms of calculating the current and voltage values of short circuits and their faults. The paper includes several tests: frequency variations and decomposition of voltage waveforms with Fourier transforms (model) and commercial relay, the effect of the power factor on the location of fault points, the relation between the tripping time and the total harmonic distortion (THD) levels in a commercial relay, and a comparison of the THD capture between the commercial relay and the model.

Measuring basic electrical quantities on the model of distribution line

In this paper, a practical laboratory exercise performed at the Laboratory for Electrical Engineering in the Higher Education Technical School of Professional Studies in Novi Sad, as an integral part of the subject Practicum is presented. The aim of the exercise is to introduce students to the phenomena of transfer of complex power along the distribution line, voltage drop, power losses, types of consumption, but also the methodology for the measurement and calculation of basic electrical quantities on the distribution line. The test network is a single-phase model of the three-phase low-voltage cable line. As a part of the exercise, measurements of voltage, current, active and reactive power and power factor are performed. The exercise analyzes the impact of X/R of the line and the type of consumption (resistive, resistive-inductive, resistive-capacitive, and motor) on the basic power system quantities.

A Novel Unity-Gain Phase Shifter for Measuring Power System Quantities

The paper presents a novel unity-gain phase shifter. Based on the voltage control all-pass filter using an analogue multiplier along with a frequency-to-voltage converter, this approach can theoretically both provide unity-gain and maintain a predetermined phase shift constant over a wide frequency range. As no complicated calculation circuit is required, the proposed scheme can be implemented using a simple hardware circuit. Some experimental results are provided to verify the validity of the proposed scheme.

Improving Power Quality in a Multi bus Multi Feeder System Using MC-UPQC

A b s t r a c t : This paper presents a new Unified Power-Quality Conditioning System (MC-UPQC), capable of simultaneous compensation for voltage and current in multi-bus/multi-feeder systems. By using one shunt Voltage-Source Converter (VSC) and two or more series VSCs the configuration is made. The system can be applied to adjacent feeders to compensate for supply-voltage and load current imperfections on the main feeder and full compensation of supply voltage imperfections on the other feeders. The configuration will be designed as all converters are connected back to back on the dc side and share a common dc-link capacitor. The system is also capable of compensating for interruptions without the need for a battery storage system and consequently without storage capacity limitations. By the simulation the performance of MC-UPQC as well as the adopted control algorithm will be illustrated. Index- terms: Voltage-Source Converter (VSC), Interline Power Flow Controller (IPFC), Unified PowerQuality Conditioning System (UPQC), I. Introduction When the power flows of two lines starting in one substation need to be controlled, an Interline Power Flow Controller (IPFC) can be used. An IPFC consists of two series VSCs whose dc capacitors are coupled. This allows active power to circulate between the VSCs. With this configuration, two lines can be controlled simultaneously to optimize the network utilization. The GUPFC combines three or more shunt and series converters. It extends the concept of voltage and power-flow control beyond what is achievable with the known two-converter UPFC. The simplest GUPFC consists of three converters—one connected in shunt and the other two in series with two transmission lines in a substation. The basic GUPFC can control total five power system quantities, such as a bus as well. By using GUPFC devices, the transfer capability of transmission lines can be increased significantly. Furthermore, by using the multiline-management capability of the GUPFC, active power flow on lines cannot only be increased, but also be decreased with respect to operating and market transaction requirements. In general, the GUPFC can be used to increase the transfer capability and relieve congestions in a flexible way. This concept can be extended to design multiconverter configurations for PQ improvement in adjacent feeders. For example, the interline unified power-quality conditioner (IUPQC), which is the extension of the IPFC concept at the distribution level, has been proposed in the IUPQC consists of one series and one shunt converter. It is connected between two feeders to regulate the bus voltage of one of the feeders, while regulating the voltage across a sensitive load in the other feeder. In this configuration, the voltage regulation in one of the feeders is performed by the shunt-VSC. However, since the source impedance is very low, a high amount of current would be needed to boost the bus voltage in case of a voltage sag/swell which is not feasible. It also has low dynamic performance because the dc-link capacitor voltage is not regulated. In this paper, a new configuration of a UPQC called the multiconverter unified power-quality conditioner (MC-UPQC) is presented. The system is extended by adding a series-VSC in an adjacent feeder. The proposed topology can be used for simultaneous compensation of voltage and current imperfections in both feeders by sharing power compensation capabilities between two adjacent feeders which are not connected. The system is also capable of compensating for interruptions without the need for a battery storage system and consequently without storage capacity limitations.

The Compression of Electric Signal Waveforms for Smart Grids: State of the Art and Future Trends

In this paper, we discuss the compression of waveforms obtained from measurements of power system quantities and analyze the reasons why its importance is growing with the advent of smart grid systems. While generation and transmission networks already use a considerable number of automation and measurement devices, a large number of smart monitors and meters are to be deployed in the distribution network to allow broad observability and real-time monitoring. This situation creates new requirements concerning the communication interface, computational intelligence and the ability to process data or signals and also to share information. Therefore, a considerable increase in data exchange and in storage is likely to occur. In this context, one must achieve an efficient use of channel communication bandwidth and a reduced need of storage space for power system data. Here, we review the main compression techniques devised for electric signal waveforms providing an overview of the achievements obtained in the past decades. Additionally, we envision some smart grid scenarios emphasizing open research issues regarding compression of electric signal waveforms. We expect that this paper will contribute to motivate joint research efforts between electrical power system and signal processing communities in the area of signal waveform compression.

Power System Oscillation Modes Identifications: Guidelines for Applying TLS-ESPRIT Method

Abstract Fast measurements of power system quantities available through wide-area measurement systems enables direct observations for power system electromechanical oscillations. But the raw observations data need to be processed to obtain the quantitative measures required to make any inference regarding the power system state. A detailed discussion is presented for the theory behind the general problem of oscillatory mode indentification. This paper presents some results on oscillation mode identification applied to a wide-area frequency measurements system. Guidelines for selection of parametes for obtaining most reliable results from the applied method are provided. Finally, some results on real measurements are presented with our inference on them.

A decoupled power flow algorithm using particle swarm optimization technique

A robust, nondivergent power flow method has been developed using the particle swarm optimization (PSO) technique. The decoupling properties between the power system quantities have been exploited in developing the power flow algorithm. The speed of the power flow algorithm has been improved using a simple perturbation technique. The basic power flow algorithm and the improvement scheme have been designed to retain the simplicity of the evolutionary approach. The power flow is rugged, can determine the critical loading conditions and also can handle the flexible alternating current transmission system (FACTS) devices efficiently. Test results on standard test systems show that the proposed method can find the solution when the standard power flows fail.

Accurate Prediction of Damping in Large Interconnected Power Systems With the Aid of Regression Analysis

This paper introduces the use of regression analysis in the study of small signal stability in large interconnected power systems. Results demonstrate the usefulness of this approach in better understanding the nature of dominant electromechanical modes of oscillation and in accurately predicting the damping on these modes. The usefulness of this approach in identifying strong correlations between system damping and distinct measurable and adjustable power system quantities such as generator output, line flows, bus voltages, and bus angles is presented. Results suggest that this approach may be useful in optimizing the location of traditional power system online recording devices, such as dynamic swing recorders (DSRs) as well as real-time monitoring devices such as phasor measurement units (PMUs). Sensitivity studies show that power system information obtained may be useful in providing an additional tool to help system operators optimize the dispatch of generating resources. It would also be useful in providing more realistic feedback from the power system and aid in the decision making regarding dynamic stability and its effect on appropriate system topology, loading levels, and allowable transfer levels in real time.

Estimating Electromechanical Mode Shape From Synchrophasor Measurements

A theoretical basis and signal-processing approach for estimating a power system's electromechanical mode-shape properties using time-synchronized phasor measurements are presented. The relationship between modal eigenvectors and measurable power system quantities are derived. Spectral correlation analysis is used to implement the approach with demonstrative examples. This includes simulation examples as well as measured data from the western North American power system.

A statistical model for estimating the trend of electrical quantities in power systems

A statistical approach to estimate the trend, over a long time interval, of electrical parameters is proposed in this paper. The trend is determined by processing a limited number of parameter values measured at instants randomly chosen. Experimental results are reported, which show the good performance of the method proposed when it is applied to estimate customers' loads profiles and the trend of some parameters providing information on power quality.

AUTOMATIC CONTINGENCY SELECTION AND RANKING USING AN ANALYTIC HIERARCHICAL PROCESS

ABSTRACT A new approach in the power system analysis to automatic contingency selection (ACS) and ranking, using an analytic hierarchical process (AHP) is developed. ACS for the real and reactive power subproblems is solved by network flow programming, based on the existence of weak coupling between real and reactive quantities in power systems. The performance indices to assess the severity of contingencies are defined as the total real and reactive load to be curtailed. In the rank calculation, this paper takes into consideration the relative importance of transmission lines and the situation that the real and reactive power security constraints may be violated as the line outage appears, so that the precise information for the real time security analysis can be provided. The results on IEEE-14 bus test system are given in the paper

Fuzzy-based adaptive digital power metering using a genetic algorithm

This paper describes an innovative, fuzzy-based, adaptive approach to the metering of power and rms voltage and current employing a genetic algorithm. The fuzzy-based adaptive metering engine adjusts the number of points per cycle to be processed and the location of these points. Adjustments are based on the optimal fuzzy rules constructed by a genetic algorithm to satisfy overall metering-error criteria under different operating environments while minimizing the number of points actually employed in the metering computation. This results in a reduction in the metering-computation effort, which frees up the processor for other tasks such as communication or power quality measurements. The fuzzy-based adaptive metering algorithm has been implemented on a microcontroller-based power metering system that employs a multitasking operating system which exploits the efficiencies achieved by the reduced metering rate. The fuzzy-based adaptive metering algorithm has been tested with a variety of actual and synthesized power-system waveforms and the experimental evaluations have demonstrated excellent accuracy in the metered power system quantities.

A unified model and automatic contingency selection algorithm for the P and Q subproblems

Abstract A new approach to automatic contingency selection (ACS) and ranking is presented in this paper. ACS for the P and Q subproblems is solved by a unified network flow model and algorithm. It is based on the existence of weak coupling between real and reactive quantities in power systems. The performance indices to assess the severity of contingencies are defined as the total real and reactive load to be curtailed. The proposed model and its algorithm are examined numerically with IEEE 5-bus, 14-bus, 30-bus, 57-bus and 118-bus test systems on an M-340 computer.

Optical measurement of power system quantities

The adoption of optical-fibre signalling by the electricity supply industry has left the way open for a wide range of measurement techniques to be adopted using those fibres, but the demands for equipment are outstripping optoelectronic technology.

Fast response detection of mean value of power system quantities

A fast response detecting method of mean value of power system quantities such as, voltage, current, power, torque angle and shaft speed deviation is proposed. The detected value, which is linearly proportional to the input signal, represents the mean value of each half cycle of the input signal that is held as a dc voltage as soon as that half cycle is over. The detection is stable against the random noise included in the signal, and does not have drooping characteristic.

A Fast Response Device for Measurement of Power, Reactive Power, Volt-Amperes and Power Factor

A solid state device using sampling techniques is described for measurement of power system quantities such as power, reactive power, voltamperes and power factor. An output voltage linearly proportional to the above quantities is provided for continuous control and recording purposes. The speed of response is less than one cycle.