Operation Of Electric Power Systems Research Articles

Detailed simulation of distance protection for its testing and setting

Abstract A significant part of severe accidents (blackouts) in electric power systems (EPS) is associated with incorrect operation of relay protection and automation (RPA). One of the main reasons for the incorrect actions of the RPA devices is its rough settings, which often does not correspond to the real operating conditions for specific device. An analysis of currently used methods and tools for RPA setting up, shown that they are largely relied on the guidelines of previous decennaries. Respectively modern techniques have the same drawbacks associated with accounting the processes in specific RPA and primary transducers and its errors by approximate coefficients. It is possible to solve the indicated problem with a highly detailed analysis of the operation of key elements of RPA schemes in the specific operating conditions. The obtained results allow to estimate the processes in protected objects, processing errors in instrumental current (ICT) and voltage (IVT) transformers, as well as in RPA itself. Such possibility could be achieved by the detailed RPA mathematical modeling. The combination of an adequate EPS simulator and RPA models allows configuring parameters of the RPA settings ensuring its correct operation in real EPS. The article presents result of this research for distance protection

Synchro-Measurement Application Development Framework: An IEEE Standard C37.118.2-2011 Supported MATLAB Library

Electrical power system monitoring, protection, operation, and control schemes are undergoing significant changes toward the next generation fully automated, resilient, and self-healing grids. At present, there still exists a lack of available user-friendly tools for the synchronized measurement technology supported application design. This paper presents a synchro-measurement application development framework (SADF) to promote a simplified design and thorough validation of synchro-measurement (IEEE Standard C37.118.2-2011) supported user-defined applications under realistic conditions. The proposed SADF supports online receiving of a phasor measurement unit (PMU) or phasor data concentrator (PDC) provided data stream and enables simultaneous use of processed machine-readable synchro-measurements in advanced user-defined applications. This paper fills the scientific gap between the IEEE Standard C37.118.2-2011 specifications and its implementation by proposing a novel robust communication technique and efficient synchro-measurement data parsing methodology. As a proof of concept, the proposed SADF is implemented as a novel open-source MATLAB library. Combining this library with MATLAB’s signal processing and visualization functions allows mastering the design and validation of complex wide-area monitoring, protection, and control applications, as well as PMU/PDC performance and compliance verification. Finally, this paper verifies the proposed library against the standard specifications, assesses its interoperability and performance via a cyber-physical simulation platform, and presents online voltage magnitude monitoring as an example application.

Identifying and Characterizing Non-Convexities in Feasible Spaces of Optimal Power Flow Problems

Optimal power flow (OPF) is an important problem in the operation of electric power systems. The solution to an OPF problem provides a minimum cost operating point that satisfies constraints imposed by both the non-linear power flow equations and engineering limits. These constraints can yield non-convex feasible spaces that result in significant computational challenges. This brief proposes an algorithm that identifies and characterizes non-convexities in OPF feasible spaces. This algorithm searches for a pair of feasible points whose connecting line segment contains an infeasible point. Such points certify the existence of a non-convexity in the OPF feasible space. Moreover, the constraint violations at the infeasible point along the connecting line segment physically characterize a cause of the non-convexity. Numerical demonstrations include a small illustrative example as well as applications to various test cases.

Analysis, Comparison and Study on Mitigation of Harmonics by using Active and Passive Harmonics Filters by using MATLAB Simulation

In this Paper Harmonics Distortion problems counter many of the conventional rules of Electric power system design and operation that consider only the fundamental frequency. The engineer is faced with unfamiliar phenomena that require their unfamiliar tools to analyse, study and unfamiliar equipment to solve. This paper is basically concerned with the Analysis and Study of Harmonics generated and Destroyed by Power Electronic Converters. The investigation and analysis of harmonics has been carried out using Fast Fourier Transform (FFT) to evaluate the Total Harmonic Distortion (THD) of the converters with and without filters. MATLAB/SIMULINK have been employed for their presenting the simulation results because it is well established and recognized simulation software for the power system. Next, the designing of Passive Filter (Single tuned), is carried out after a literature review and have been applied to the converters for harmonics mitigation. In the future, we would proceed to work on Active as well as Passive (combination types) Filters for Harmonics Mitigation. The harmonic distortion solution chosen was to design a passive filter to decrease the distortion by shifting the resonance point of the network. This Paper includes the method to design the passive filter and its impact on efficiency and energy usage.

Technologies for estimation and forecasting of photovoltaic generation output supporting stable operation of electric power system

In recent years, Japan has rapidly extended its use of electricity obtained via photovoltaic (PV) generation. When the proportion of PV in the generation mix was small, its unpredictable output fluctuations had little effect on the supply and demand operation. However, as the role of PV in grid supply grows, predicting these fluctuations becomes increasingly necessary to ensure stable and economical operation of the electric power system. In this study, we discuss the current approaches of estimating and forecasting the PV output. © 2018 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Power Quality Analysis of Electrical Distribution Systems with Asynchronous Generators

In recent times, it has been observed that the implementation of well-organized Distribution Systems are the back bone of smart grids. Further, the need of the hour is to realize a more flexible system involving energy savings and favorable environmental factors leading to development of Distributed Generation Systems (DGs). Such systems are expected to play an important role in efficient operation of Electric Power Systems. In this context, efforts are made to determine the effect of DGs on the electrical distribution networks. Different Electrical configurations of asynchronous generator - wind turbines have been considered leading to an algorithm developed to determine the influence of optimally placed DGs at various buses in the system. The behavior of the system is analyzed through different Power Quality Indices (PQIs), which are calculated by applying probability concepts, that overcome the limitations associated with traditional methods of calculating the Total Harmonic Distortion (THD). Additionally, a new PQI based on Total Demand Distortion (TDD) is also presented. An intelligent control algorithm based on machine learning concepts is incorporated, enabling to initiate power quality improvement/control strategies to be adopted by the distribution manager. A 17-bus test system is considered and modeled using Open Distribution System Simulator (OpenDSS). The results obtained are analyzed by MatLab - OpenDSS Component Object Model (COM) interface. The efficacy of the results is imminent based on a comparison with similar results obtained by the authors in the related literature.

Анализ развития системной аварии в ОЭС Востока 1 августа 2017 г.

The large-scale collapse occurred in the Russia’s UES East Power Pool caused the power pool to separate into two isolated sub-areas at the cut set “Transition through the Amur River”. Generally, the collapse was mainly attributed to poorly coordinated operation of the power pool elements, including the set of closed-loop and automatic control devices. The key factors and events involved in the course of this system collapse are analyzed. Explanations of certain events and processes specific to this collapse are suggested. Conclusions and recommendations derived from the analysis of this system collapse are formulated. To ensure coordinated development of different components of the East Power Pool and their coordinated operation under the conditions when there are many entities participating in these processes, it is necessary to develop and adopt a number of regulatory documents, one of which is the “Regulations for Process Operation of Electric Power Systems”.

Parametric identification of fuzzy model for power transformer based on real operation data

The research is devoted to the development of a fuzzy model for assessing the technical condition of power oil transformers based on the DGA. The parametric identification of optimal values of membership functions of fuzzy terms for linguistic variables is carried out to increase the reliability and objectivity of fault identification. For this purpose, it is proposed to use the theory of fuzzy sets, the nonlinear optimization method. A comparative analysis of the fuzzy simulation results for the technical condition with the fault diagnostic results on existing power transformers has confirmed high efficiency. The diagnostic accuracy of the adapted fuzzy model for the technical condition assessment of power transformers is 97 %, which is acceptable in the power transformers diagnostic. The developed model will be used for further research on the development of an algorithm for making effective decisions regarding the operation strategy of power transformers and preventive control of the subsystem operation of electric power systems. The obtained results of the fuzzy simulation for the technical condition assessment of power transformers give grounds to assert regarding the possibility of implementation in software of operation risk analysis of electric power systems for power supply companies

On the Coordination of Current Transformers and Relay Protection and Automation Operation of Electric-Power Systems in Transient Short-Circuit States

Due to the increasing number of incorrect actions of relay protection in transient processes accompanied by saturation of current-transformer (CT) cores, there is a need for developing a domestic standard for protective CTs designed to operate in transient states. The following ways to provide proper relay protection operation in transient states accompanied by saturation of CTs in operation are considered: (a) CT shedding that includes an increase in control cables’ cross sections, (b) development of relay-protection and automation algorithms based on the recognition of crash conditions in an appropriate CT transformation time interval of 2–3 ms, (c) development of relay-protection and automation algorithms with virtual CT error compensation, and (d) development and introduction of new primary-current converters. It is concluded that, for existing large power plants with installed TPX current transformers, it is advisable to use improved digital relay-protection algorithms for information processing obtained from CTs, for example, by methods (b) and/or (c).

Experimental thermal investigation of an ONAN distribution transformer by fiber optic sensors

Transformers are considered as one of the main and high cost components of the power systems. This is due to the fact that their failure may have negative influence on sustainability and quality of energy. In addition, some failures may lead to high cost for replacement or repair and an unplanned outage of a power transformer is highly uneconomical. As a result, as a major equipment in power systems, its correct functioning is vital to enable efficient and reliable operation of electric power system. A transformer can fail due to any combination of electrical, mechanical or thermal stresses. The normal operation life of a transformer is partially related to the deterioration of its insulation through thermal ageing, which is determined mainly by its daily cyclic loadings. In this paper, heat analysis of a 1.5MVA Oil-Natural Air-Natural cooling mode distribution transformer is experimentally investigated by equipped fiber optic sensors. The density of the fiber optic sensors is increased at the active parts in critical spots. Temperature measurements are realized according to the transformer losses variation and load variation tests. The thermal behavior of the distribution transformer is obtained. Contrary to the existing studies, the obtained results show that also the structure and the design of the transformer affects the hot-spot position and temperature.

Optimal sizing of a wind/solar/battery hybrid grid‐connected microgrid system

Higher cost and stochastic nature of intermittent renewable energy (RE) resources complicate their planning, integration and operation of electric power system. Therefore, it is critical to determine the appropriate sizes of RE sources and associated energy storage for efficient, economic and reliable operation of electric power system. In this study, two constraint-based iterative search algorithms are proposed for optimal sizing of the wind turbine (WT), solar photovoltaic (PV) and the battery energy storage system (BESS) in the grid-connected configuration of a microgrid. The first algorithm, named as sources sizing algorithm, determines the optimal sizes of RE sources while the second algorithm, called as battery sizing algorithm, determines the optimal capacity of BESS. These algorithms are mainly based upon two key essentials, i.e. maximum reliability and minimum cost. The proposed methodology aims to avoid over- and under-sizing by searching every possible solution in the given search space. Moreover, it considers the forced outage rates of PV, WT and utilisation factor of BESS which makes it more realistic. Simulation results depict the effectiveness of the proposed approach.

Parallel operation of triple- and double-wound transformers with difference transformation ratios

During the operation of electric-power systems, there is often a problem of splitting up the capacity of transformers installed on substations, which, as a rule, entails mounting two or more transformers in parallel instead of a single one, the total capacity of which is the same. In such replacement, there is a problem of uniform distribution of the load between transformers. When using transformers that have the same capacity and are structurally similar, uniformity of load distribution is reached achieved owing to symmetry of parallel circuits. However, if transformers with of different designs and various transformation ratios are connected, then uniformity of a capacity distribution between transformers is violated. With an increase in the total load current, in the case of double-wound transformer I and triple-wound transformer II connected in parallel, the secondary current of transformer I increases, as does its primary current, while the primary and secondary currents of transformer II decrease. In addition, the total current from the mains is less than the current of the primary winding of transformer I. With an increase in the loading current, the secondary current of transformer I increases and the secondary current of transformer II decreases. At the highest value of the secondary current of transformer II, the vector of primary current of this transformer advances the voltage vector by more than by 90°. In addition, the secondary winding of transformer II consumes active power from transformer I and returns it to its primary winding.

It's Indisputable: Five Facts About Planning and Operating Modern Power Systems

An indisputable fact cannot be rebutted. It is supported by theory and experience. Over the past 25 years, wind and solar generation has undergone dramatic growth, resulting in a variety of experiences that model the integration of wind and solar into the planning and operation of modern electric power systems. In this article, we bring together examples from Europe, North America, and Australia to identify five indisputable facts about planning and operating modern power systems. Taken together, we hope these experiences can help build consensus among the engineering and public policy communities about the current state of wind and solar integration and also facilitate conversations about evolving future challenges.

Smart Grid Simulations and Their Supporting Implementation Methods

In this tutorial we present the state-of-the-art as well as new methods for simulating various planning, operation, stability, reliability, and economic models of electric power systems. The discussion is driven by both first-principle models and empirical models. First-principle models result from the fundamental physics and engineering principles that govern the behavior of various components of a grid. Empirical models, on the other hand, are models that result from statistics and data analysis. We overview a wide spectrum of applications starting from planning models with a time-scale of simulation in years to real-time models where the time-scale can be in the order of milliseconds. We present a list of simulation software popularly used by the power engineering research community across the world. The increasingly important roles of power electronics, communication and computing, model aggregation, hybrid simulation, faster-than-real-time simulation, and co-simulation in emulating the daily operation of a grid are enumerated. The importance of research testbeds for testing, verification and validation of complex grid models at various temporal and spatial scales is also highlighted. The overall goal is to provide a vision on how simulations and their supporting implementation methods can help us in understanding the evolving behavior of tomorrow’s power networks as a truly intelligent cyber-physical system.

Inter-temporal R&D and Capital Investment Portfolios for the Electricity Industry’s Low Carbon Future

ABSTRACT A pressing question facing policy makers today in developing a long-term strategy to manage carbon emissions from the electric power sector is how to appropriately balance investment in R&D for driving innovation in emerging low- and zerocarbon technologies with investment in commercially available technologies for meeting existing energy needs. Likewise, policy makers need to determine how to allocate limited funding across multiple technologies. Unfortunately, existing modeling tools to study these questions lack a realistic representation of electric power system operations, the innovation process, or both. In this paper, we present a new modeling framework for long-term R&D and electricity generation capacity planning that combines an economic representation of endogenous non-linear technical change with a detailed representation of the power system. The model captures the complementary nature of technologies in the power sector; physical integration constraints of the system; and the opportunity to build new knowledge capital as a non-linear function of R&D and accumulated knowledge, reflective of the diminishing marginal returns to research inherent in the energy innovation process. Through a series of numerical experiments and sensitivity analyses— with and without carbon policy—we show how using frameworks that do not incorporate these features can over- or under-estimate the value of different emerging technologies, and potentially misrepresent the cost-effectiveness of R&D opportunities.

Smart Grid is the Key to Enhance the Penetration of Renewable Energy into Electric Power Systems

Dear researchers, Due to the rapid development of renewable energy technologies because of environmental concerns, the electric power grid is experiencing a significant change. The electrical power structure is no longer a vertically integrated structure due to the large grid parity of renewables and as a result, smart grid is the key to enhance the penetration of renewable energy into electric power systems. However, due to the intermittent probabilistic nature of renewable energy sources, design and management of power are a great challenge to both power and computing industry. Furthermore, it has been anticipated that future energy structure will be “two-way streets”, allowing every energy user to be not only a customer, but an energy provider as well. So, a smart grid structure is the need in the present scenario. This transition from classical power structure inevitably demands significant research for many rapidly rising issues. This Special Issue focuses on smart grid that can accommodate renewable energy into electric utility systems. The Special Issue is interested but not limited to the following issues relevant to increased renewable energy penetration: 1) Prediction of sustainable energy resources. 2) Stability and control of sustainable energy in supporting grid frequency and voltage. 3) Steady-state and transient assessment of system, etc. 4) Extent to which dispatchable generation reserves required and under what circumstances. 5) Effect on reliability be compromised with increased sustainable energy penetration. 6) Cost considerations with renewable’s variability 7) Effect on system operating strategies with sustainable energy generation 8) Effect on various measuring devices for effective monitoring and evaluation of electric power system operation, etc. Dr. Neeraj Gupta

Fuzzy logic approach to modelling trust in cloud computing

Despite the growing deployment of mission critical applications on computing systems, trust and security continues to hinder its full adoption and deployment on cloud computing platforms. In addition to accountability and non-repudiation on the cloud deployment, end-users want to be confident of availability and reliability of services. For any cloud platform to be secure and trusted, the individual layers of the platform must be secure as there is no `one fits all solution' for securing all the layers. This work presents a multi-layer trust security model (MLTSM) based on unified cloud platform trust that employs a fuzzy logic combination of on-demand states of several different security mechanisms, such as identification, direct and in-direct trust, across all cloud layers. In addition, results from a MATLAB-based simulation of the model are also presented. A MLTSM can improve the secure deployment of cloud infrastructure in mission critical sectors such as electrical power system operation, as it provides empirical evidence that allows direct (on-demand) determination and verification of the trust state of any given cloud computing platform or service. Such a modelling approach is useful for comparison, classification and improving end-user confidence in selecting or consuming cloud computing resources.

AGC of restructured multi-area multi-source hydrothermal power systems incorporating energy storage units via optimal fractional-order fuzzy PID controller

Owing to nonlinear structure and uncertain load demand characteristics, expert and intelligent automatic generation control (AGC) is inevitable for coherent operation and control of electric power system. Hence, in this paper, to mitigate the frequency and power deviations efficiently under sudden load demand conditions, a novel fractional-order fuzzy PID (FOFPID) controller is suggested in AGC of restructured multi-area multi-source hydrothermal power systems. The parameters of FOFPID controller are optimized by utilizing bacterial foraging optimization algorithm. The controller is implemented on restructured two- and three-area systems. It is observed that the advocated method shows superiority over fuzzy PID, fractional-order PID and conventional PID control schemes. Energy storage units such as redox flow batteries (RFB) which show extremely long charge–discharge life cycle and outstanding quick response to alleviate the system oscillations under disturbances have further been incorporated into the studied systems to analyze their efficacy in boosting AGC performance. Analysis of results reveals that with RFB, system transient performance improves significantly. It is also observed that the obtained results satiate the AGC requirement under different power transactions taking place in a deregulated market in the presence/absence of appropriate generation rate constraint treated for thermal and hydro plants. Finally, the robustness of the presented approach is demonstrated against the wide variations in the system parameters and initial loading condition.

Coordinated Distributed MPC for Load Frequency Control of Power System With Wind Farms

Load frequency control (LFC) is crucial for the operation and design of modern electric power systems. This becomes quite challenging, as more wind power is included into the power system. This paper proposes a coordinated distributed model predictive control (DMPC) for the LFC of a power system that includes inherently variable wind-power generations. This DMPC communicates power system measurement and prediction data, and considers the information of other controllers for their local objective to realize effective coordination. The controllers solve the optimization problem while considering given constraints, e.g., generation rate constraints, wind speed, pitch angle, and load input constraints for each area. Since the wind-power output depends largely on the wind speed, different optimization modes for the DMPC were used. Both simulation and experimental tests of a four-area interconnected power system LFC, which consists of thermal plants, hydro units, and a wind farm, demonstrate the improved efficiency of the coordinated DMPC.

Evaluation of the performance of different firefly algorithms to the economic load dispatch problem in electrical power systems

The planning, operation and control of electric power systems has attracted the attention of many researchers. Thus, effort is put in improving the efficiency of generation and operation of power plants. Economic load dispatch (ELD) is crucial since it is required to schedule committed generating units so as to meet load demand at minimum operating cost. In addition to satisfying all system equality and inequality constraints as well as limitations imposed on the generating units during operation. To solve the economic load dispatch problem, traditional and intelligent techniques were applied. Researchers have shown interest in utilizing metaheuristic methods to solve complex optimization problems in real life applications. In this paper, three alternatives of firefly algorithms are applied to solve the nonlinear ELD problem. A comparative study is carried out on the solution of ELD problem using those recent variants and the classical firefly algorithm for different test cases. Efficiency is evaluated by comparing best solutions obtained in terms of execution time, fuel cost and power loss.Keywords: Economic load dispatch, Firefly algorithm, Modified firefly, Memetic firefly, and Variable step size firefly