Fundamental Power System Research Articles

A Review of Various Optimization Strategies for Handling Optimal PMU Placement Problems

Abstract: The Phasor Measurement Unit (PMU) is the most fundamental power system technology that is utilized to protect, monitor, and control power networks. It not only allows real-time, synchronized voltage measurements on the buses but also the current phasor of lines connected to the buses where these PMUs are placed. The positioning of PMUs at each bus node is unnecessary and is restricted by the installation's high cost and complexity. As a result, the fundamental goal of Optimal PMU placement (OPP) is reducing the total no. of PMUs along with maximum observability, while simultaneously considering measurement redundancy. There are several methods for fixing this problem, and they fall into two categories: Metaheuristic methods and mathematical approaches. This study examines a variety of optimization strategies for handling OPP problems

Reactive power control in renewable rich power grids: A literature review

AbstractRecently, there is vast progress in the integration of renewable energy generators (REGs) into the power grid. The reactive power, which is indeed a fundamental power system factor is being influenced highly by the renewable power penetration levels. As a consequence, this has paved the way toward the generation of steady‐state voltage and dynamic/transient stability issues. Therefore, to provide a sustainable and dependable power grid, it is indeed important to maintain and control adequate reactive power reserves. This study introduces a comprehensive literature survey on “management of reactive power in renewable‐rich power networks”. A total of 75 research publications have been collected for this study, and a concise summary of each article is offered. The articles are categorized according to the types of REGs used, type of control, grid code consideration, controller device, implementation tools, grid type, load type as well as various reactive power support systems. In addition, this study examines the advantages and drawbacks of existing models. The performance recorded in each of the collected papers are discussed. Ultimately, the most critical challenges related to management of reactive power in renewable‐rich power grids are identified, along with some essential methodological suggestions for the electricity sector, regulators, and research scientists.

Simplifying the Design of Lipschitz Observers by Applying a Novel Batch Pole Assignment Approach

Abstract A novel, analytic design method for full state observers of nonlinear Lipschitz systems with their nonlinear term bounded, is considered. In standard procedures, the Lipschitz constant of the nonlinear term imposes strict restrictions on the observer gain matrix stable selection and introduces a further uncertainty in the design, caused by the heuristic manner of this selection. As shown in the paper, when the system nonlinear term is additionally bounded, which is a common situation for many real world systems such as manipulators in robotics and generators in power systems, the Lipschitz constant restriction is fully relaxed. Under these circumstances, a direct design approach is proposed that assigns the observer linear part eigenvalues at a common, specific, negative real position on the left of the system poles. The whole procedure is conducted by simply solving a Lyapunov-type equation that simultaneously constructs the suitable corresponding gain matrix of the observer. The validity of the method and the enhanced observer performance are verified by simulation results conducted on a fundamental power system example.

Chaos and bifurcation behavior in a fundamental power system with electromagnetic disturbance and load disturbance

With the increasing scale of the power grid and increasingly complex structure, the power system is always affected by various disturbances and parameter changes. The power system containing electromagnetic and load power disturbance simultaneously can exhibit rich behaviors, which accords with the reality. The chaotic oscillation caused by the power disturbance may lead to unstable operation of the power grid. Therefore, a fourth-order power system model with power disturbance is established in this paper. The nonlinear characteristic of the system under multiple disturbances is studied through the bifurcation diagram, Lyapunov exponent spectrum and the phase plane. The influence of the disturbance amplitude and frequency on the system under the condition of different frequency ratio is presented through the basin of attraction with parameter mapping, and the states of different motions of the system are given more intuitively, which is helpful for better understanding the chaotic behaviors of power system.

Chaos control of a four-dimensional fundamental power system using pole placement-based proportional integral sliding mode control

In this paper, the problem of chaos control for a four-dimensional fundamental power system (FDFPS) model is investigated. Pole placement-based proportional integral sliding mode control (PISMC) is designed to control the chaos present in the system. Proportional integral sliding mode control law is derived by placing the poles at appropriate location to control the chaotic behaviour in four-dimensional fundamental power systems. The sufficient condition is derived for the asymptotic stability of the sliding manifold using Lyapunov stability theory. The proposed controller reduces the chattering, simplifies the design of power system stabiliser. Further the proposed pole placement-based PISMC is compared with conventional SMC approach. MATLAB is used for simulation. Simulation results show the effectiveness of proposed PISMC scheme.

Chaos control of a four-dimensional fundamental power system using pole placement-based proportional integral sliding mode control

In this paper, the problem of chaos control for a four-dimensional fundamental power system (FDFPS) model is investigated. Pole placement-based proportional integral sliding mode control (PISMC) is designed to control the chaos present in the system. Proportional integral sliding mode control law is derived by placing the poles at appropriate location to control the chaotic behaviour in four-dimensional fundamental power systems. The sufficient condition is derived for the asymptotic stability of the sliding manifold using Lyapunov stability theory. The proposed controller reduces the chattering, simplifies the design of power system stabiliser. Further the proposed pole placement-based PISMC is compared with conventional SMC approach. MATLAB is used for simulation. Simulation results show the effectiveness of proposed PISMC scheme.

Probabilistic Forecasting Model of Solar Power Outputs Based on the Naïve Bayes Classifier and Kriging Models

Solar power’s variability makes managing power system planning and operation difficult. Facilitating a high level of integration of solar power resources into a grid requires maintaining the fundamental power system so that it is stable when interconnected. Accurate and reliable forecasting helps to maintain the system safely given large-scale solar power resources; this paper therefore proposes a probabilistic forecasting approach to solar resources using the R statistics program, applying a hybrid model that considers spatio-temporal peculiarities. Information on how the weather varies at sites of interest is often unavailable, so we use a spatial modeling procedure called kriging to estimate precise data at the solar power plants. The kriging method implements interpolation with geographical property data. In this paper, we perform day-ahead forecasts of solar power based on the probability in one-hour intervals by using a Naïve Bayes Classifier model, which is a classification algorithm. We augment forecasting by taking into account the overall data distribution and applying the Gaussian probability distribution. To validate the proposed hybrid forecasting model, we perform a comparison of the proposed model with a persistence model using the normalized mean absolute error (NMAE). Furthermore, we use empirical data from South Korea’s meteorological towers (MET) to interpolate weather variables at points of interest.

An Extended Kalman Filter Approach for Accurate Instantaneous Dynamic Phasor Estimation

This paper proposes the application of a non-linear Extended Kalman Filter (EKF) for accurate instantaneous dynamic phasor estimation. An EKF-based algorithm is proposed to better adapt to the dynamic measurement requirements and to provide real-time tracking of the fundamental harmonic components and power system frequencies. This method is evaluated using dynamic compliance tests defined in the IEEE C37.118.1-2011 synchrophasor measurement standard, providing promising results in phasor and frequency estimation, compliant with the accuracy required in the case of off-nominal frequency, amplitude and phase angle modulations, frequency ramps, and step changes in magnitude and phase angle. An important additional feature of the method is its capability for real-time detection of transient disturbances in voltage or current waveforms using the residual of the filter, which enables flagging of the estimation for suitable processing.

Future security of power supply in Germany-The role of stochastic power plant outages and intermittent generation

Many power plants in Germany and Europe are approaching the end of their technical lifetime. Moreover, the increasing wind and solar power generation reduces the operation times of thermal power plants, making future investments in new generation capacity uncertain under current market conditions. Consequently, the future development of security of power supply is unclear. In this paper, we assess the impact of stochastic fluctuations in power plant availability, renewable generation, and grid load on the future security of supply in Germany. We model variations in power plant availability by application of a combined Mean-reversion Jump-diffusion approach. On the basis of that and using Monte-Carlo methods, we simulate 300 different time series of availability. These profiles are fed into the fundamental power system model REMix, applied to evaluate the appearance of supply shortfalls in hourly resolution. We assess 6 scenarios for the year 2025, differing in renewable generation and demand profiles, as well as grid infrastructure. Geographical focus of the analysis is Germany, but the electricity exchange with its European neighbours is modelled as well. Our results show that the choice of the power plant availability profile can change the loss of load expectation and loss of load hours by up to 50%. However, the influence of load and renewable generation profiles is found to be significantly higher. Assuming that no new conventional power plants are built and existing plants are decommissioned at the end of their empirical lifetime, we identify supply gaps of up to 2.7 GW in Germany.

Generator Dynamic Response Analysis and Improvement Following Distribution Network Disturbance

<p>Use of renewable energy sources for the purposes of electricity generation is increasing throughout the world. Connection of new generators, however, introduces significant challenges to power network operators and managers. The power system transient stability is affected by the grid connection of new generation units. The objective of this paper is to investigate asynchronous generator dynamic response issues and capabilities under three phase symmetrical fault conditions and to propose a methodological approach to designing a generator transient stability solutions. Analysis and methodology are introduced through a realistic generator connection example. Simulations show that power system stability can be significantly affected by the connection of new generators and that this phenomena needs to be carefully considered during the connection planning process. This paper is a part of an ongoing research on the distributed generation impact on power network and its aim is to provide two main contributions to the existing body of knowledge. Firstly, it is expected that this paper will contribute toward a better understanding of the influence that generators have on the power system transient stability. Secondly, this paper is expected to contribute towards the practical understanding of fundamental power system transient stability improvement solutions.</p>

Studying the Effect of Non-Linear Loads Harmonics on Electric Generator Power Rating Selection

Non-linear loads connected to an electric power system produce Harmonic currents, harmonics are introduced into the system in the form of currents whose frequencies are the integral multiples of the fundamental power system frequency (50/60 Hz). The harmonic currents interact with the supply system impedance causing distortions in supply output voltage and current, which has a very bad effect on all other loads connected to the system and the power supply itself, such as overheating, increasing powers losses in the system, and malfunction of protection and control devices connected to the system. This paper presents a study to analyze the effect of voltage and current harmonics resulting from non-linear loads such as variable frequency drive, uninterruptable power supply, and battery chargers on operation and power rating of synchronous generator. The study introduces an optimized method for selecting the suitable generator power rating to withstand harmful harmonics effects for a safe operation of the generator, saving its lifetime, and to improve the power quality of the power system. The method depends on analyzing the effect of increasing the supply generator power rating on the THVD produced from non-linear loads harmonics connected to the system. By calculating the THVD for each case of a generator power rating, a mathematical relationship between generator power rating and TVHD can be found. So, the relationship between generator power rating and total harmonic distortion in the power system will be discussed clearly.

Modeling and Maximum Power Point Tracking Control of Wind Generating Units Equipped with Permanent Magnet Synchronous Generators in Presence of Losses

This paper focuses on the modeling of wind turbines equipped with direct drive permanent magnet synchronous generators for fundamental frequency power system simulations. Specifically, a procedure accounting for the system active power losses to initialize the simulation starting from the load flow results is proposed. Moreover, some analytical assessments are detailed on typical control schemes for fully rated wind turbine generators, thereby highlighting how active power losses play a fundamental role in the effectiveness of the wind generator control algorithm. Finally, the paper proposes analytical criteria to design the structure and the parameters of the regulators of the wind generator control scheme. Simulations performed with Digsilent Power Factory validated the proposed procedure, highlighting the impact of active power losses on the characterization of the initial steady state and that the simplifying assumptions done in order to synthesize the controllers are consistent with the complete modeling performed by the aforementioned power system simulator.

Chaos suppression for a four-dimensional fundamental power system model using adaptive feedback control

In this paper, the problem of chaos suppression for a four-dimensional fundamental power system (FDFPS) model is considered via the design of a novel adaptive feedback controller. The period doubling bifurcation route to chaos and some dynamical behaviors of the power system are investigated in detail. Based on stability analysis using an energy-type Lyapunov function, a single adaptive feedback controller is derived to suppress chaotic oscillation in four-dimensional fundamental power systems. The proposed controller simplifies the design of power system stabilizer and provides an easy way to implement in practical power system control. In addition, effectiveness of damping out chaotic oscillation and robustness against parameter uncertainty and external disturbance also make the proposed control scheme applicable for industrial application. Simulation results illustrate the effectiveness, the robustness and the superiority of proposed control method.

A Study on Adequate Level of Generation Reserve Margin Based on Stochastic Evaluation of Operational Cost with Large Penetration of Photovoltaic Generations

Photovoltaic generation (PV) systems are growing as one of renewable energy resources in the world from their merits of low greenhouse effect gas exhaustion and less fossil fuel consumption. However, PV output widely varies depending on the insolation condition and is uncontrollable. When huge amount of PV systems are interconnected to a grid, the supply and demand balancing, one of the most important and fundamental power system operations, might become more difficult. In such situation, PV output forecast should be taken in to account in the unit commitment process and/or the online balancing operation. Particularly, the generation reserves should be set aside so that the PV output fluctuation and PV output forecast error can be compensated. From this viewpoint, this paper proposes an operational cost evaluation method considering the probabilistic feature of forecast error. Furthermore, a method for estimating the adequate reserve required for large PV installations is presented.

Mitigating Electric Shock and Arc-Flash Energy: A Total System Approach for Personnel and Equipment Protection

This article provides a comprehensive discussion of the application and selection of various techniques and technologies available for the reduction and mitigation of arc-fault hazards to personnel and equipment. It also presents a broad approach that considers the total electrical system configuration and design. No technology can address all safety concerns. Current available technologies, such as optical light detection, pressure detection, temperature detection, and current signatures, for reducing arcflash hazard are discussed, and the advantages and disadvantages of each technique are outlined. An analysis is presented about how a total system approach can optimize the benefits of various technologies by using complementary technologies such as impedance grounding, equipment construction, and operational techniques. The importance of the fundamental power system configuration selection, equipment design aspects, and maintenance is also discussed.

A novel frequency tracking method based on complex adaptive linear neural network state vector in power systems

This paper presents the application of a Complex Adaptive Linear Neural Network (CADALINE) in tracking the fundamental power system frequency. In this method, by using stationary-axes Park transformation in addition to producing a complex input measurement, the decaying DC offset is eliminated. As the proposed method uses first-order differentiator to estimate frequency changes, a Hamming filter is used to smoothen the response and cancel high-frequency noises. The most distinguishing features of the proposed method are the reduction in the size of observation state vector required by a simple Adaptive Linear Neural Network (ADALINE) and increase in the accuracy and convergence speed under transient conditions. This paper concludes with the presentation of the representative results obtained in numerical simulation and simulation in PSCAD/EMTDC software as well as in practical study.

Dynamical Behavior and Singularities of a Single-machine Infinite-bus Power System

This paper uses the geometric singular perturbation theory to investigate dynamical behaviors and singularities in a fundamental power system presented in a single-machine infinite-bus formulation. The power system can be approximated by two simplified systems S and F, which correspond respectively to slow and fast subsystems. The singularities, including Hopf bifurcation (HB), saddle-node bifurcation (SNB) and singularity induced bifurcation (SIB), are characterized. We show that SNB occurs at P Tc = 3.4382, SIB at P T0 = 2.8653 and HB at P Th = 2.802 for the singular perturbation system. It means that the power system will collapse near SIB which precedes SNB and that the power system will oscillate near HB which precedes SIB. In other words, the power system will lose its stability by means of oscillation near the HB which precedes SIB and SNB as P T is increasing to a critical value. The boundary of the stability region of the system can be described approximately by a combination of boundaries of the stability regions of the fast subsystem and slow subsystem.

Numerical investigation of the main factor promoting chaotic power swing in a single‐machine, infinite‐bus power system model with the AVR

AbstractThis paper presents numerical results on bifurcations and chaotic behavior in a fundamental power system model, a single‐machine infinite‐bus system model with generator excitation control by the first‐order lag AVR. The numerical analysis mainly focuses on revealing the parameter value region where the chaotic behavior is observed. It is shown that the partially linearized model, which is derived by linearizing all of the nonlinear elements except the AVR limiter, exhibits similar bifurcations and chaos. Several simulation results indicate that the mechanisms producing the chaotic behaviors and the bifurcations are the same both in the linearized model and in the original single‐machine infinite‐bus system model for parameter value variation which does not move the equilibrium point from the reference point used for the linearization. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 142(2): 21–28, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10090

A fast and accurate distance relaying scheme using an efficient radial basis function neural network

The paper presents a new approach for classification and location of faults on a transmission line using a newer version of radial basis function neural network (RBFNN) which provides a more efficient approach for training and computation. The input data to the RBFNN comprise the normalised peak values of the fundamental power system voltage and current waveforms at the relaying location obtained during fault conditions. The extraction of the peak components is carried out using an extended Kalman filter (EKF) suitably modelled to include decaying d.c., third and fifth harmonics along with the fundamental. The fault training patterns required using the efficient version of RBF neural network are much less in comparison to the conventional RBF network and the choice of neurons and the parameters of the network are systematically arrived without resorting to trial and error calculations. The new approach provides a robust classification of different fault types for a variety of power system operating conditions with resistance in the fault path. Further a new fault location strategy is formulated using four neural networks, one each for the major category of faults like LG, LL, LLG and LLL faults. The proper feature selection for the networks results in an accurate and fast distance relaying scheme. © 2001 Published by Elsevier Science B.V.

Coexistence of four different attractors in a fundamental power system model

This paper reports the occurrence of a rare phenomenon in dynamical systems when four different attractors namely a stable equilibrium, a stable limit cycle and two strange attractors coexist in a fundamental power system model. The paper shows that power system operation could get trapped into sustained chaotic oscillations after a large disturbance even when there exists a viable stable equilibrium point in the model.