Operation Of Electric Power Systems Research Articles

Investment equilibrium of an integrated multi–stakeholder electricity–gas–hydrogen system

The coordinated planning and operation of electric power and natural gas systems contribute significantly toward the integration of renewables and decarbonization of energy systems. The coupling between the two systems will be further increased due to the potential use of hydrogen that represents an indispensable terminal energy source. Thus, this study proposes an investment equilibrium model for an integrated electricity–gas–hydrogen system (IEGHS) constituting electric power systems, natural gas systems, and hydrogen fuel stations. Specifically, electricity, gas, and hydrogen energy trading are considered in this model. A triangular coupling relationship is formulated in the IEGHS with the objective of maximizing each stakeholder's profit. Furthermore, two trading mechanisms with different energy prices are built and compared. In particular, the equilibrium model with locational marginal energy prices (LMEPs)-based trading is further solved via a direct approach based on the Karush–Kuhn–Tucker conditions and strong-duality theory. Case studies indicate that the LMEP-based trading provides the highest overall benefit in the case of multiple stakeholders. Additionally, the impact of energy price, investment equipment price, and equipment conversion efficiency on the investment equilibrium of IEGHS is investigated.

Economical Reliability Level for Electrical Power Systems.(Dept.E)

This paper introduces a mathematical model for having the optimum operation of electrical power system with different values of reliability levels. The start-up costs of the units, minimum-up times and minimum-down times of the units are of the factors considered Based on the reserve requirements and reliability analysis, a suggested method is presented for economical reliability computation of electrical power systems.

Evaluating Multitimescale Response Capability of EV Aggregator Considering Users’ Willingness

With the wide deployment of charging piles and the development of vehicle-to-grid technology, electric vehicles (EVs) will have more opportunities to participate in the operation and scheduling of electric power system through the EV aggregator (EVA), an intermediate agent between the power grid and EV users. Quantitatively evaluating the response capability (RC) of EVA, i.e., charging and discharging power ranges, is of fundamental importance for its trading with the operator of power grid. This article proposes a user-aware method to obtain a more accurate range of multitimescale RC considering the response willingness of EV users. First, a temporal RC evaluation model of a single EV considering charge-discharge state and state of charge (SOC) is established. Second, based on the user psychology model, which reflects the relationship between users' responsivity and incentive price, a multitimescale RC evaluation model of EVA considering users' willingness is built. The day-ahead RC of EVA is evaluated by the state prediction data of EVs. According to the control strategy which considers response time and SOC indicators comprehensively, the RC evaluation is updated intraday. Finally, using the statistical data from the EU MERGE project, the effectiveness of the proposed evaluation model is verified, and the impact of incentive price and scheduling time scale on the RC of EVA are analyzed. The results indicate that the proposed model can effectively track the scheduling goals of the system and realize the dynamic update of the RC of EVA.

Модель минимизации дефицита мощности электроэнергетических систем с учетом ограничений по контролируемым сечениям

A steady trend towards the development of electric power systems leads to their continuous enlargement and sophistication. As a result, new ways of their control appear. In this regard, the existing models and complexes for adequacy assessment may work inadequately and ineffectively in terms of the obtained results adequacy. To assess the current state of the existing models and complexes, we reviewed and analyzed the domestic and foreign software and computer systems. In particular, we considered mathematical models of minimizing the power shortage. This work is based on the problem of modifying mathematical models of minimizing the power shortage used in adequacy assessment of the electric power systems of one of the complexes under consideration. As a modification of mathematical models, it is proposed to exclude the existing method of using the line capacities and start use correct accounting for the maximum permissible active power flow in controlled sections. The experimental part reflected in the paper concerns the testing of options for models to minimize the power shortage, as well as the proposed modifications on various systems, including those consisting of three and seven reliability zones with a variable number of controlled sections and power lines included in them. The results of the study have shown that the proposed modifications are efficient and can be used in the future. The authors also obtained the most adequate results in terms of the physical laws of electric power system operation due to the model of minimizing the power shortage with quadratic losses which takes into account the limitations of power transmission over controlled sections.

Monitoring of ice formation of overhead power line wires

Reliable operation of electric power systems is impossible without the creation of modern monitoring devices that control all processes of production and distribution of electric energy. The authors of the article developed an intelligent system for monitoring ice formation and determining the wire sag boom using machine vision technology. The monitoring system under consideration is placed on a support in close proximity to the wire and consists of the following main elements: an electronic unit, an optical sensor, a solar panel and a GSM antenna. The developed monitoring system in close proximity to the thickness of the ice wall and indirectly, by the angle of deviation of the wire relative to the horizontal position, to determine the mass of ice deposits and the arrow of the wire sag.

Laboratory Evaluation of a Phasor-Based Islanding Detection Method

Constantly growing distributed energy generation based on renewable sources creates a number of new challenges for electrical power system operation. One of the challenges is islanding detection. Unintentional islanding, which can cause health and safety hazards for the personnel, is currently being experienced by a growing number of consumers/prosumers especially in the case of photovoltaic inverters. This work presents a new islanding detection method based on synchrophasor measurements. The proposed method works in either a passive or hybrid mode. In a passive mode, a single phasor measurement unit (PMU) in the island region is used. In a hybrid mode, one PMU in the island and another one outside the island are exploited. The proposed method was verified in conducted laboratory tests that confirmed the applicability of PMUs data for effective detection and monitoring of unintentional islanding.

A multi-objective formulation of improving flexibility in the operation of electric power systems: Application to mitigation measures during the coronavirus pandemic

The coronavirus pandemic has infected more than 23 million people worldwide by August 2020 along with more than 800,000 deaths. To face this pandemic, a joint effort among different areas has been required. In this context, the correct supply of basic services is the key to enhance the complex circumstance. The operation of the electric power systems is needed to ensure the answer to the situation. Basic services in areas of health, security, food, and communications depend on the electricity supply. Consequently, this paper introduces a multi-objective procedure that enhances the operations of power systems under these circumstances. It considers geographical areas that are affected by coronavirus cases and their effects on the personnel of power plants. To obtain the best combinations of total cost and protection of the workers, lexicographic optimization is implemented. The effectiveness of this approach is studied by solving two test cases: a 6-bus system and the Argentine Electric System with real data about the infection cases. The effects on the electricity generation and transportation stages are studied. The results allow identifying critical areas and proposing corrective actions. The method can reach feasible solutions with a low computational requirement.

A Full-Newton AC-DC Power Flow Methodology for HVDC Multi-Terminal Systems and Generic DC Network Representation

The use of Direct Current (DC) transmission links in power systems is increasing continuously. Thus, it is important to develop new techniques to model the inclusion of these devices in network analysis, in order to allow studies of the operation and expansion planning of large-scale electric power systems. In this context, the main objective of this paper is to present a new methodology for a simultaneous AC-DC power flow for a multi-terminal High Voltage Direct Current (HVDC) system with a generic representation of the DC network. The proposed methodology is based on a full Newton formulation for solving the AC-DC power flow problem. Equations representing the converters and steady-state control strategies are included in a power flow problem formulation, resulting in an expanded Jacobian matrix of the Newton method. Some results are presented based on HVDC test systems to confirm the effectiveness of the proposed approach.

Impact of wind and solar power plants on the reliability of the IPS

One of the most promising areas in the development of the electric power industry is generally regarded to lie in expanding the share of renewable energy sources (RES) in the electric energy balance of power systems in the form of wind and solar power plants (WPP and SPP), the saving of organic fuel (coal, gas, fuel oil) and the reduction of environmentally harmful emissions into the atmosphere considered to be their most important advantages. However, the impact of RES on the controllability of the modes of operation of electric power systems and on the reliability of the IPS operation remains quite unexplored.Currently, the global energy industry uses 318 million kW of WPP and about 142.4 million kW of SPP, of which the major West European countries account for about 227 million kW, or 49.3%. On average, wind and solar power plants account for almost 30% of the total generating capacity in Western Europe, with Denmark having the largest share of WPP (47%) and Germany having the highest share of SPP (18.6%). However, an uncontrolled growth in the share of WPP and SPP in the structure of generating capacities of power systems begins to manifest itself in a sharp decline in the reliability of the power industry due to the fact that a number of negative properties of WPP and SPP have not been taken into account (at least, to a sufficient extent), which manifested themselves in practice in a system accident in the UK power system that occurred on August 09, 2019, when, as a result of an "ordinary" short circuit, a system accident occurred, with up to 1.1 million consumers with a total load of 1690 MW disconnected from the power supply system for a period of 15 to 45 minutes. This is estimated to have resulted in economic losses for consumers amounting to 12.3–15.0 million USD.The reason for this is that the high sensitivity of WPP, SPP, CCGT and gas piston units to voltage and frequency drops is not properly considered in conditions of insufficient capacity of the rotating (mobile) generation reserve. Damage can be prevented by increasing the rotating reserve within the available reserve of the power system, which will require an increase in funds for maintaining the same due to additional fuel consumption. The ratio of reduction of probable damage to consumers and the cost of additional fuel consumption for maintenance of a required rotating reserve in the power system allows to economically substantiate the strategy and scale of introduction of renewable energy sources to the power industry.

Optimal Stochastic Operation of Integrated Electric Power and Renewable Energy With Vehicle-Based Hydrogen Energy System

The renewable energy-based hydrogen production can lead to the integrated electric power and hydrogen system (IPHS) and offer a pathway to a sustainable energy utilization. Hydrogen is mainly transported via hydrogen tube trailers (HTs), making the hydrogen energy system (HES) operation quite different from those of other energy technologies. This paper proposes an optimal IPHS operation strategy which utilizes HT for transportation. The proposed strategy coordinates hydrogen generation, transportation, and storage stages considering constrained operations of electric power system (EPS), transportation system, and variable renewable energy. The proposed solution method is based on the alternating direction method of multipliers (ADMM) in which HES and EPS constraints are managed individually and the respective solutions are coordinated accordingly. The case studies using the modified IEEE-RTS79 have verified the validity of the proposed IPHS model and its solution method and confirmed the necessity of considering HES in enhancing the EPS operation. The synergies between EPS and HES are studied via numerical examples and the impact of the flexibilities in hydrogen generation, transportation and demand are highlighted.

Modeling of Ultra-Short Term Offshore Wind Power Prediction Based on Condition-Assessment of Wind Turbines

More accurate wind power prediction (WPP) is of great significance for the operation of electrical power systems, as offshore wind power penetration increases continuously. As the offshore wind turbines (OWT) are a key system in converting offshore wind power into electrical power, maintaining their condition plays a pivotal role in WPP. However, it is seldom considered in traditional WPP. This paper proposes an ultra-short term offshore WPP methodology based on the condition assessment (CA) of OWTs. Firstly, a modified fuzzy comprehensive evaluation (MFCE) based CA of the OWT is presented with a new defined deterioration of indicators calculated by the relative errors. Long short-term memory (LSTM) neural network is introduced to deal with the complicated interactions between the various monitoring data of an OWT and the dynamic marine environment. Then, with the classifications of the health conditions of the OWT, the historical operation data is classified accordingly. An OWT-condition based WPP with a backpropagation (BP) neural network is developed to deal with the non-linear mapping relations between the numerical weather prediction (NWP) information, health conditions of OWT, and the output power. The results of the case study show the influences of the OWT health conditions to its output power and verifies the effectiveness and higher accuracy of the proposed method.

Electric Vehicle Ultra-Fast Battery Chargers: A Boost for Power System Stability?

As a consequence of the exponential growth of the electric vehicle (EV) market, DC fast-charging infrastructure is being rapidly deployed all around the world. Ultra-fast charging (UFC) stations are starting to pose serious challenges to the electric power system operation, mostly due to their high peak power demand and unregulated discontinuous operation. To address these issues, local energy storage can be installed, ensuring a smoother grid power absorption profile and allowing to provide grid-supporting features. In this work, a control solution for the grid-side AC/DC converter of next-generation EV UFC stations is proposed. A virtual synchronous compensator (VSC) control algorithm is implemented, in order to lessen the impact of the charging station on the utility and to provide the full spectrum of grid ancillary services (i.e., frequency regulation, reactive power compensation, harmonic reduction, short circuit current generation, etc.). The proposed control strategy is verified experimentally on a downscaled 15 kVA three-phase inverter, emulating the grid front-end of the charging station.

A review of the potential of district heating system in Northern China

In Northern China, coal-fired power plants play a key role in electricity and heat generation, significantly intensifying air pollution. Meanwhile, a large percentage of wind power is curtailed every year owing to its conflict with heat supplies during the winter period, leading to a huge amount of energy waste. The flexibility of district heating systems has the potential to solve this problem and has attracted considerable attention from electric power system operators, thermal power plant owners, and policy makers. In this paper, a comprehensive survey on the potential of district heating systems in accommodating fluctuating heat supply and demand is proposed. The work first provides an overview of district heating systems in Northern China and how to quantify the flexibility of district heating systems. Next, the flexibility requirements and enhancement strategies of the district heating systems in northern China are thoroughly reviewed. The survey indicates that there is still great potential for the development of a flexible heating system. Moreover, state-of-the-art topics are addressed, including the challenges to be overcome and the status quo of clean heating provision, wind curtailment mitigation, and industrial waste heat utilization. Finally, this paper discusses future directions for deploying the flexibility of district heating systems in northern China, including new heat sources, digitalization, demand-side management, heat market deregulation, and energy policy reform.

Комплекс обработки и анализа метеорологических данных в АО "СО ЕЭС" (АС "Метео")

To ensure the operation of Electric Power Systems the System Operator requires significant amount of rapidly updated meteorological data affecting power consumption. The present paper describes Automated system (AS) Meteo software that provides storage and processing of various types of meteorological data, performing analytical calculations, generating reports for daily work and for reporting periods.

Методика построения интегральных показателей комплексной оценки свойств узлов электроэнергетических систем

The problem of selecting the electric power system control nodes is studied. By performing control of these modes, matters concerned with providing reliable power supply of the required quality to consumers can be settled in the most efficient manner. As an example, a fragment of the electric power system mathematical model used in the Finist mode-setting simulator for a power system dispatch control center operator is considered, which represents a highly branched electrical network consisting of eleven 110 kV nodes, three 220 kV nodes connected with the system, and two generator nodes. A new procedure for selecting the control nodes is proposed, which takes into account a combination of different indicators having different measurement units, dimensions and scales is proposed. These indicators characterize the following properties of power system nodes: the reactive power fraction absorbed at a node, the sensitivity of voltage to reactive load variations, the number of connected power lines, and statistical indicators characterizing the change of voltage at the nodes and reactive power flows for different options of installing the reactive power compensation devices. For combined use of these indicators, they were ranked according to the efficiency of installing reactive power compensation devices in the system. For each indicator, a scale of five ranks (intervals) is set, which determine the preferences (qualitative judgments) of the researcher in evaluating the reactive power compensation devices installation efficiency at the system nodes. The highest rank (5) corresponds to the maximum efficiency, and the lowest rank (1) corresponds to the minimum efficiency. To calculate the individual (integral) priority indicator of installing reactive power compensation devices, the ranks of indicators are added together, and their sum is divided by the product of the number of ranks by the number of the used indicators (features). Based on the calculation results, the rating (location) of each node is determined, and the nodes for installing the reactive power compensation devices are selected according to their effect on ensuring the electric power system operation reliability, active power losses in the network, and voltage regulation. Thus, a new procedure is presented for determining the integral indicators for comprehensively estimating the properties of complex electric power system nodes and selecting the controlled nodes using a system of various indicators. These indicators characterize the studied nodes in terms of the efficiency of installing reactive power compensation devices to reduce active power losses in the network, voltage regulation, and ensuring the electric power system operational reliability. The validity of the results obtained in the study is confirmed by their comparison with the indicators of the balance-conductivity method, which has proven itself in solving problems connected with determining the nodes for controlling electric power system operation modes.

Probabilistic Dynamic Optimal Energy Flow Calculation for the gas-electric coupling system

Due to pollution and energy shortage, the multi-energy interconnected system formed by natural gas and electricity coupling has attracted a lot of attention because of its cleanness and high efficiency. The operation of natural gas system and electrical power system belong to different time scales. At the same time, more and more new energy sources such as wind and photovoltaic power generation in the electrical power system increase the uncertainty of power supply. The operation of gas-electric coupling system must consider the impact of these factors. In response to these problems, this paper considers the impact of timing on the operating state of gas-electric coupling system based on the multi-period optimization model, and proposes a probabilistic energy flow calculation method, namely the Latin Hypercube sampling Markov Chain simulation (LHMCS). This method can quickly obtain the influence of random factors on the operating state of gas-electric coupling system. Finally, a simulation example verifies the rationality and effectiveness of the method proposed.

Оценивание состояния воздушной линии переменного тока методом релинеаризации

As is well known, dispatch control centers receive information about the electric power system operation mode from a supervisory control and data acquisition system (SCADA) and phasor measurement units (PMU) in the form of remote measurements and remote signals. The remote measurements contain information on the power system operating parameters, and remote signals contain information on the positions of switching equipment. The controlled facility state estimation problem is conventionally solved using iteration methods because the system of state equations is nonlinear in nature. The application of the Kipnis-Shamir method makes it possible to transform the nonlinear system of algebraic equations into a linear system in a non-iterative manner by replacing quadratic state variables, after which the obtained linear system is solved parametrically. By applying a second transformation of variables, the system of algebraic equations is transformed into a second system of linear equations, after which the solution of this system and the quadratic system of linear equations, and, hence, also the initial system of nonlinear equations are found. The application of the non-iterative approach is considered on the example of estimating the state of a 500 kV overhead power line.

Расстановка ветровых электростанций в электроэнергетической системе

Specific conditions of wind farms operation require special treatment of the wide range of aspects, in particular, calculation of the parameters characterizing the influence of wind farms on the power system operation regime and efficient practical representation of data calculated for a long period of time. The aim of the study is to formulate a method for placing the totality of wind farms in the electric power system (EPS). To this end, it is necessary to estimate the influence of wind farms on the EPS operation regime main parameters. For carrying out the study, methods for statistical processing of big databases, optimization methods, and numerical methods were used. Computational experiments were carried out in the Microsoft Office Excel software package. Based on the study results, criteria have been obtained using which it is possible to determine the most suitable places for the installation of wind farms, for example, to reduce the fluctuations in the EPS generation schedule. In addition, the values of the revealed indicators are used to evaluate the possibility of controlling the existing conventional power plants and identify measures for widening the adjustment range. The larger the capacity of wind farms, the more significant their influence is; however, the negative component of this influence decreases if many wind farms operate in the power system. By using the developed method, the most rational nodes of the EPC can be selected using the identified criteria at the design stage in determining the wind farms installation places. The accomplished studies have yielded a simple and practically applicable approach to determining the most optimal wind farm placement sites.

Расстановка ветровых электростанций в электроэнергетической системе

Specific conditions of wind farms operation require special treatment of the wide range of aspects, in particular, calculation of the parameters characterizing the influence of wind farms on the power system operation regime and efficient practical representation of data calculated for a long period of time. The aim of the study is to formulate a method for placing the totality of wind farms in the electric power system (EPS). To this end, it is necessary to estimate the influence of wind farms on the EPS operation regime main parameters. For carrying out the study, methods for statistical processing of big databases, optimization methods, and numerical methods were used. Computational experiments were carried out in the Microsoft Office Excel software package. Based on the study results, criteria have been obtained using which it is possible to determine the most suitable places for the installation of wind farms, for example, to reduce the fluctuations in the EPS generation schedule. In addition, the values of the revealed indicators are used to evaluate the possibility of controlling the existing conventional power plants and identify measures for widening the adjustment range. The larger the capacity of wind farms, the more significant their influence is; however, the negative component of this influence decreases if many wind farms operate in the power system. By using the developed method, the most rational nodes of the EPC can be selected using the identified criteria at the design stage in determining the wind farms installation places. The accomplished studies have yielded a simple and practically applicable approach to determining the most optimal wind farm placement sites.

Methodology of optimum unit commitment of energy systems with renewable energy sources

One of the promising ways to improve the reliability and efficiency of power supply for customers in the areas remote from central electrical grid is the use of hybrid power systems with renewable energy sources. The primary task of designing such systems is the unit commitment of the generating equipment that provides the optimal technical and economic indexes of the electric power system. The stochastic nature of generation and nonlinearity of the characteristics of power plants cause a high complexity of solving this problem, which, from a mathematical point of view, is formulated as an optimization problem. An accurate and reliable solution of this optimization problem increases the efficiency of design and operation of hybrid electric power systems with renewable energy sources. And it is a vital task of modern power industry. A probabilistic-statistical methods and models for the analysis of experimental data are used to construct climatic time series and graphs of electrical loads. In addition, to study the operating modes of the electric power system the MatLab system is used for the simulation and modeling, and an evolutionary particle swarm algorithm is used to solve the optimization problem. The original model of solar radiation is used as a part of this methodology. This model provides forecasting the key characteristics of solar radiation in any geographical point of Russia including the areas that have no results of routine actinometric observation. Weibull distribution function is used to forecast daily variations of wind speed. It enhances the validity of forecasting of electricity generation of wind-driven power plant at daily time interval. As a result of the research, a method of optimum unit commitment has been developed for the equipment of electric power systems based on renewable energy sources. The use of the particle swarm algorithm as a part of the methodology provides reliable and accurate determination of the extremum of the objective function, which increases the efficiency of design and operation of hybrid electric power systems with renewable energy sources. The method has been tested on practical examples of optimum unit commitment for the equipment of electric power systems of various configurations and has proven its effectiveness. The technique is implemented as a software application, which ensures the convenience of its practical application. The obtained results can be used by companies involved in the design and operation of electric power systems using renewable energy generating units.