Reactive Power Balance Research Articles

A Review on the Impact of Transmission Line Compensation and RES Integration on Protection Schemes

South Africa is currently experiencing an energy crisis because of a mismatch between energy supply and demand. Increasing energy demand necessitates the adequate operation of generation and transmission facilities to maintain the reliability of the power system. Transmission line compensation is used to increase the ability to transfer power, thereby enhancing system stability, voltage regulation, and reactive power balance. Also, in recent years, the introduction of renewable energy sources (RES) has proven to be effective in supporting the grid by providing additional energy. As a result, the dynamics of power systems have changed, and many developing nations are adopting the integration of renewable energy into the grid to increase the aspect ratio of the energy availability factor. While both techniques contribute to the grid’s ability to meet energy demand, they frequently introduce technical challenges that affect the stability and protection of the systems. This paper provides a comprehensive review of the challenges introduced by transmission line compensation and the integration of renewable energy, as well as the various techniques proposed in the literature to address these issues. Different compensation techniques, including fault detection, classification, and location, for compensated and uncompensated transmission lines, including those connected to renewable energy sources, are reviewed. This paper then analyzes the adaptive distance protection schemes available in the literature to mitigate the impact of compensation/integration of RES into the grid. Based on the literature reviewed, it is essential for protection engineers to understand the dynamics introduced by network topology incorporating a combination of RES and heavily compensated transmission lines.

Use of reactive power compensation devices in implementation of distributed generation

In Ukraine, a gradual reduction of electricity production at thermal power plants is planned due to the development of renewable sources of electricity. Small hydraulic power plants are being restored, solar power plants and wind power plants are being built. This will allow solving the existing problems of the domestic energy industry regarding the shortage of fuel resources, energy security and reducing the level of harmful effects on the environment caused by the operation of traditional sources of electricity. There is a trend of transition from a purely centralized electricity supply to a combined one, when the number of local decentralized sources of electricity directly in distribution networks is increasing. In this way, distribution electric networks are gradually transformed into a network with features characteristic of a local electric system, which receives power both from its own distribution electric networks and from a centralized source - the electric power system. Renewable energy has a number of advantages compared to traditional energy, but there are also disadvantages. Among them, the complications of the functioning of electrical networks should be highlighted in the event of an increase in the capacities of renewable sources of electricity installed in them and the instability of generation due to their natural dependence on meteorological conditions, if we talk more specifically about technical shortcomings, then this concerns - sinusoidal of voltages and currents and voltage deviations, quality assurance of electricity, which directly depends on ensuring the balance of active and reactive power in the electrical system. Hence the need for coordinated power supply from renewable sources of electricity and substations of the power system. At the same time, there is a gradual transition from the wholesale electricity market of a single buyer to the balancing market of electricity and electricity supply under bilateral agreements, as well as the introduction of market management methods. This article discusses measures to reduce electrical energy losses, limit voltage deviation, improve the quality of electrical energy, and compensate for the reactive power of local loads due to the introduction of reactive power compensation devices together with renewable sources of electricity and facilitating their integration into the power grid.

ВИЗНАЧЕННЯ ЗАРЯДНОЇ ЄМНОСТІ ПОВІТРЯНИХ ЛІНІЙ ЕЛЕКТРОПЕРЕДАЧІ З УРАХУВАННЯМ ПРОВИСАННЯ ПРОВОДУ

The paper presents the results of studying the effect of wire sagging on the charging capacity of an overhead power line. A refined mathematical model of the overhead line charging capacity is obtained. The results of the study of the error of neglect of wire sagging for typical structures of overhead power lines with voltage from 35 to 750 kV with the arrangement of wires in 2-3 tiers and horizontal arrangement are presented. The influence of changes in the wire sagging boom on the value of the power line charging capacity due to changes in the operating temperature of the wire and due to ice deposits is investigated. It is shown that for 750 kV power lines, such a change can reach 1-1.5%, which, in combination with the long length of the main power lines, can cause a change in the balance of reactive power in the line itself and in adjacent power systems. The possibility of monitoring the wire sagging boom in a run is investigated and the requirements for the accuracy of such measurements are determined. Bibl. 14, fig. 3, table.

Selection of Asynchronized Turbogenerators Parameters Taking into Account the Operating Mode

The purpose of the work is to develop an algorithm for calculating currents in the asynchro-nized turbogenerator rotor windings when it operates at a power system with a variable load. Typically, synchronous turbogenerators of thermal power plants are used to maintain the balance of active and reactive power in the power system. But they cannot fully ensure the maintenance of balance by switch-ing to non-nominal modes: during periods of power consumption dips, reduce power to 50-70% and switch to under-excitation mode to compensate for reactive power. Therefore, it is promising to install asynchronized turbogenerators at power plants in parallel with synchronous turbogenerators, which re-main stable over a wide range of changes in active and reactive power. The work analyzed data from the operation of asynchronous turbogenerators in different countries. The subject of the study was an ASTG-200-2U3 asynchronized turbogenerator with two identical field windings. The goal of the work was achieved by calculating the field windings currents using the finite element method and modeling in the FEMM program when the load magnitude and nature changes. The most important results of the work are the proposed algorithm for calculating the asynchronized turbogenerators field currents de-pending on the load size and nature in order to maintain the frequency and voltage nominal values. The significance of the results obtained lies in the fact that practical recommendations have been obtained for choosing the asynchronized generator load angle depending on the load size and nature, including in the modes of consumption of reactive energy.

An innovative fuzzy logic frequency regulation strategy for two-area power systems

Modern environmentally friendly power system designs offer several application benefits, but they also generate losses. In order for this structured power system to operate reliably, the total generation, total load demand, and system losses must be balanced. Changes in load demand disrupt both the real and reactive power balances. As a result, the system frequency and tie-line interchange power differ from their planned values. A large variance in system frequency can cause the system to crash. Multiple connected area systems use clever load frequency control techniques in this scenario to deliver dependable and high-quality frequency and tie-line power delivery. In this case, a freestanding hybrid power system is considered, with generated power and frequency intelligently managed. In addition to the unpredictability of the wind, frequent changes in the load profile can result in significant and damaging power variations. The output power of such renewable sources may fluctuate to the point where major frequency and voltage variations occur in the system. The fuzzy logic PID controller (FLPIDC) is an intelligent approach recently proposed to address the load frequency control (LFC) issue of an interconnected power system. Standard proportional integral derivative (PID) controllers operate each section of the system.

Steady-state analysis of a hybrid power supply system using an induction generator with a shunt AC/DC converter

Hybrid power supply systems (HPSSs) are considered as a good option for electric power supply of remotely located from the grid consumers due to significant fuel savings compared to diesel sets. Quick development and improvement of HPSSs may be achieved using specialized methodologies and programs. In the paper a schematic diagram is proposed and operation principles of a 400 V / 50 Hz HPSS were developed. The system’s main component is the master generating unit of the hydropower plant using a 250 kW induction generator (IG). The voltage of the system is controlled by the controller of the AC/DC power converter. The electrical frequency of the system is controlled by the speed controller of the hydropower turbine. A wind turbine, an energy storage system and a regulated dump load are connected to the IG through the AC/DC converter. Goal. The paper aims to develop a methodology for steady state performance analysis of the hydraulic turbine driven isolated IG operating in parallel through an AC/DC power converter with additional sources and consumers of active power. Methodology. The methodology for evaluation of performance characteristics of the IG operating in the proposed system has been developed. The methodology is based on the equivalent circuit of the system, equations of active and reactive power balance in the system and the superposition method. Results. The equations of frequency, voltage and power regulators of the system are given. The performance characteristics of the IG operating in the system supplying resistive and RL load in «constant voltage – constant frequency» mode are obtained. Novelty. The developed methodology is innovative in taking into account the control algorithms of the system. The comparative analysis of the IG’s performance operating in the stand-alone generating unit and in the generating unit connected to the proposed system is performed. Practical value. The developed methodology can be used for development and performance improvement of hybrid AC power systems.

Agglomerative Hierarchical Clustering Methodology to Restore Power System considering Reactive Power Balance and Stability Factor Analysis

Despite there are significant advancements in modern power systems, blackouts remain a potential risk, necessitating efficient restoration strategies. This paper introduces an innovative concept for power system restoration, focusing on balancing active and reactive power while ensuring voltage stability. For instance, this paper employs an agglomerative clustering technique, which partitions the power system into segments with balanced reactive power, facilitating swift restoration postblackout. Central to this methodology is the use of the line stability factor, which assesses the voltage stability of individual lines, identifying the system’s stronger and weaker sections based on voltage stability levels. This paper demonstrates the effectiveness of the proposed methodology through case study analysis, comparing voltage stability levels across agglomerative clusters and their geographical locations. The power system is divided into two stable partitions, considering the number of black-start generators, available reactive power, and voltage stability levels. This partitioning reveals that the clusters formed by the agglomerative method are inherently stable, suggesting enhanced system stability, dependability, and availability during the restoration phase following a blackout. In addition, this paper discusses the potential causes of blackouts, offering insights into their prevention, and finishes with a novel clustering methodology for power systems, considering reactive power and voltage stability. This method facilitates the parallel restoration of the system’s independent partitions, significantly reducing restoration time; it addresses critical challenges and outcomes, underscoring the methodology’s potential to revolutionize blackout recovery processes in modern power systems.

Model for Minimizing Energy Consumption of Electric Power Systems Taking Into Account the Balance of Active and Reactive Power

The work covers the developed model of minimization of active power shortage taking into account the balance of active and reactive power. The motivation for the formation and testing of this model is the need to improve the adequacy of models of this class, as well as the need to implement it in the developed methodology for assessing planned reliability. The article specifies the requirements for the model and the process of its formation, which is based on the models of minimization of active power shortage and the optimal power flow format models. When forming the model, the required set of parameters was specified, namely, the modules of busbar voltages, phase angles of voltages, active and reactive resistance, and balance constraints of active and reactive power were formed. As a result of the analysis of experiments using circuits with 3 nodes, a difference in the result of the minimum power shortage (from 3.05 to 4.46%) was revealed compared to the problem based on the model of minimization of active power shortage without taking into account reactive power in balance constraints.

Reactive power optimization control for multi-energy system considering source-load uncertainty

Reactive power control in power systems is an important way to ensure stable system operation. However, as the coupling between multi-energy systems increases, the uncertainty of supply and demand in the power system poses new challenges for reactive power control. Therefore, the main objective of this study is to perform reactive power balance control of the grid in a multi-energy system. Firstly, we studied the characteristics of reactive power demand during the energy transport of a multi-energy system. In addition, we studied the reactive power output characteristics of various power sources and their uncertainties. The reactive power balance of the multi-energy system and its uncertainty model are established. Then, we studied the adjustable pressure limits of the energy medium transmission pipelines of the heat supply network and the gas pipeline network. The reactive power demand capacity of the system is determined according to the system's energy condition and safe operation boundary. Finally, we established a reactive power optimization simulation model of the multi-energy system, considering the heat-gas network constraints. The study proposes that the optimal reactive power control method can improve the voltage stability of the multi-energy system.

CONCEPTUAL MODEL OF A MICRONЕTWОRK WITH DISTRIBUTED ENERGY RESOURCES

Mіcrоnеtwоrk configurations are considered regarding the form of electricity transmission and distribution. The structures of connected units of dіstrіbutеd еnеrgy rеsоurcеs under different operating modes are described, in which special attention is paid to the primary control elements of dіstrіbutеd еnеrgy rеsоurcеs units for the instantaneous balance of active and reactive power, as well as to dispatch control architectures for long-term energy management. The characteristics of static and dynamic load are studied, the simulation of which is carried out by building physical models of typical loads. The parameters of the system of instantaneous balances of active and reactive power in mіcrоnеtwоrks determined by instantaneous load tracking and load distribution between blocks of distributed energy resources are obtained. The circuit of resistive active filtering of blocks of distributed energy resources for active compensation of distorted loads is given. The presented method effectively suppresses harmonic voltage distortions at the output of blocks of dіstrіbutеd еnеrgy rеsоurcеs. Ref. 10, fig. 2. Keywords: mіcrоnеtwоrk, еlеctrіcіty cоnvеrtеr, dіstrіbutеd еnеrgy rеsоurcе, lоаd dіstrіbutіоn, cоntrоl systеm.

Stability Analysis of Autonomous Microgrid Operated at Constant-Frequency with the Consideration of Reactive Power Balance

Large-scale autonomous microgrids have potential application values as they can increase renewable energy penetration level without compromising the stability of the existing large power systems. Before their widespread implementation, critical issues like stability analysis etc need to be solved. This paper analyses the stability in an autonomous microgrid operated at constant frequency with the consideration of reactive power balance. Difference equations of reactive power for the grid-forming generator are constructed separately from those for the grid-supporting and grid-feeding generators while the difference equations of the real power for all the generators are the same. For the voltage source inverter with its current controlled by proportional resonant controller, at the fundamental frequency, its output current is disentangled from its terminal voltage and is controlled to trace its reference accurately, namely . Therefore, each inverter can be modelled as an equivalent current source and the equivalent circuits for d-component and q-component can be separated from each other. Then, the nodal equations in matrix form for the microgrid system can be established readily. With these, the system level state-space equations are built to study the distribution of eigenvalues. By choosing proper coefficients for real power and reactive power reference generations and controller’s parameters, one can make all the eigenvalues falling in the left-hand-side of the complex plane. Therefore, the system is stable. Such a research paves the way for systematically searching good sets of coefficients and controller’s parameters which make system operate safely away from unstable region with necessary margin.

Analysis of Novel Energy-Efficient Converters to Ensure the Required Quality of Electrical Energy

This article proposes several solutions for the use of novel AC voltage regulators as electrical energy quality conditioners and for the use of a half-bridge voltage inverter circuit as an active filter. This study was carried out with a real object, and more attention was paid to it. Structural models of electrical energy quality assurance systems, the calculation of control system elements and experimental results are presented. In particular, the use of a half-bridge voltage inverter circuit was considered as a replacement for the passive filter of the battery charger and rectifier device. AC voltage regulators are also used as compensators for higher-current harmonics, namely active filters and reactive power, voltage drop, voltage unbalance and flicker effect compensators. Block diagrams of power quality conditioners are presented, control algorithms are developed and the results of the current high-frequency harmonics compensation, reactive power and signal balancing are presented. The results of an active filter experiment based on the NRT 160.220 charge-rectifier device circuit showed a reduction in ripple of up to 1% with smaller dimensions compared to a passive filter. The control characteristics and external characteristics of the regulators are removed. The dependences of the current THD factor and the power factor are presented depending on the modulation depth for AC voltage regulator circuits used as power quality conditioners.

Resilience-oriented planning strategy for the cyber-physical ADN under malicious attacks

With the increasing coupling between the communication network and the power system, malicious cyber-physical attacks pose a serious threat to the security of cyber-physical systems (CPS). Besides the direct failures caused by the attacks on the corresponding systems, the indirect failures caused by the physical attacks on the cyber side are also of concern. Therefore, this paper proposes a resilience-oriented planning strategy for the cyber-physical active distribution network (ADN) under the malicious attacks. The strategy first coordinates the planning of line hardening and signal protection to reduce the size of direct and indirect failures. In addition, the energy consumption of base stations (BSs) in wireless communication networks is adjusted based on communication reliability (CR) to improve the controlled state of resilience resources during the recovery process. Finally, the controllable distributed generations, capacitor banks and soft open points are scheduled considering the response capability differences to ensure the balance of active and reactive power during the emergency response and restoration dispatch. The proposed strategy is modeled as a D-A-Multi-D model. To evaluate the strategy, simulations are implemented on the 33-bus and 123-bus ADNs. The results show that neglecting the impact of indirect failures leads to an underestimation of the unserved load cost of about 21.7% compared to the proposed strategy. Moreover, BS adjustment and temporal recovery processes are more applicable to the resilience enhancement of the ADN.

A New Soft Computing Fuzzy Logic Frequency Regulation Scheme for Two Area Hybrid Power Systems

Modern renewable energy power system designs provide significant application benefits, but they also produce losses. The total generation, total load demand, and system losses must be balanced in order for this structured power system to operate reliably. The actual and reactive power balances are disturbed as a result of changes in load demand. System frequency and tie line interchange power deviate from their planned values as a result of this. A high system frequency deviation can cause the system to crash. In that case, multiple connect area systems use intelligent load frequency control techniques to deliver dependable and high-quality frequency and tie line power flow. Here, a standalone hybrid power system is taken into consideration, with generated power and frequency being controlled intelligently. In addition to the unpredictable nature of the wind, frequent adjustments in the load profile can produce sizeable and detrimental power variations. The output power of such renewable sources may fluctuate to the point that it causes significant frequency and voltage changes in the grid. An intelligent approach recently proposed to address the load frequency control (LFC) issue of an interconnected power system is known as fuzzy logic PID controller (FLPIDC). Standard proportional integral derivative (PID) controllers are used to control each section of the system.

Super-twisting sliding mode control of a static synchronous compensator: An application in a wind–diesel hybrid system

The dynamic nature of load and wind power could lead to reactive power imbalance, and hence the voltage deviations in a wind–diesel power system. These deviations, if not controlled, may drive the system to operate in an unstable manner. Therefore, in this paper, a static synchronous compensator (STATCOM) is interconnected to the system to achieve reactive power balancing and minimize voltage deviations. To improve the dynamic performance of STATCOM and achieve the effective operation of the system, an optimized sliding mode controller (SMC) is designed. With the help of the design of a first-order switching manifold, an SMC is designed, which generates a control law to control the converter firing angle, and hence the reactive power output of the STATCOM. To eliminate the chattering drawback of SMC and improve the convergence characteristics, a second-order super-twisting sliding mode controller (STSMC) is proposed. The asymptotic stability of the proposed controller is guaranteed through the Lyapunov stability analysis. Particle swarm optimization (PSO) is employed to fine-tune controller parameters and achieve optimal performance. Validation of the improved performance of the system through this proposed scheme has been carried out in the MATLAB/Simulink environment and presented in the simulation studies.

A Second-Order Cone Programming Model of Controlled Islanding Strategy Considering Frequency Stability Constraints

Controlled islanding is an important defense mechanism for avoiding blackouts by dividing the system into several stable islands. Sustainable systems that incorporate a high proportion of renewable energy are prone to frequency instability or even severe blackout events due to extreme weather conditions. Thus, it is critical to investigate controlled islanding considering frequency stability constraints to reduce the risk of a sustainable system collapse in extreme weather conditions. Here, the frequency constraint of islands is derived based on the law of energy conservation, and the island connectivity constraint is proposed based on the idea of network flow. A controlled island second-order cone programming model with frequency stability constraints is proposed for the islanding strategy. The consideration of frequency constraints can help to avoid islands with too low inertia generated by the islanding strategies, ensuring that the frequency nadir of the island remains within a safe range after disturbance. Connectivity constraints can ensure connectivity within the island and no connectivity between different islands. The model also meets the reactive power balance and voltage limits in the system. Simulations of the three test systems show that this island model, which takes frequency stability into account, is effective in reducing the risk of sustainable power system collapse in extreme weather conditions.

Analysis of reactive power loadability and management of flexible alternating current transmission system devices in a distribution grid using whale optimization algorithm

AbstractThe optimal injection of reactive power to minimize power loss and manage voltage profiles is a difficult task that must be addressed and managed effectively for the power system's reliability. The distribution network indices like voltage stability, loss minimization, and power quality enhancement can be improved by the effective management of reactive power regulation. Aside from its interaction with reactive power management, the best location and sizing in a cost‐effective strategy have an impact on overall performance. As a broadly accepted swarm intelligence method in various engineering fields due to its simple assembly, less entails operator constraints, wild convergence speed, and better harmonizing ability between exploration and exploitation faces, the Whale Optimization Algorithm (WOA) is used in conjunction with a Flexible Alternating Current Transmission System (FACTS) device in this paper to manage reactive power effectively. The WOA was implemented and compared with Differential Evolution (DE), Particle Swarm Optimization (PSO), and Genetic Algorithm (GA) at 100%, 150%, and 200% load in the IEEE 30 test system. The results reveal that the suggested WOA produces a greater impact on cost management, power loss, and reactive power balance than any previous evolutionary algorithm.

Active Power Distribution Networks with Decentralized Multi-Agent Control Mode. Part 2

The article considers the solution of system tasks concerned with controlling the overall mode of an electric network with distributed generation: maintaining active and reactive power balances in normal modes, emergency control when large disturbances of the normal mode occur, maintaining the power supply system operability in post-emergency modes, restoring the power system integrity and normal operation after it was disintegrated into isolated parts by an accident or emergency control system operation. Methods of solving these tasks in a decentralized manner are proposed, which have been tested on physical models of power systems and in a pilot project on Minigrid. The developed Minigrid is integrated with an external electric network using a control system that is an agent of a multiagent system. A conclusion is made about the possibility of developing a technology for decentralized control of the modes of electric networks with distributed small generation sources. In the first part [1], the terminology used is given, the concept of a subject of the multiagent control system of electric networks with distributed generation is given, and matters concerned with multiagent decentralized control of frequency and voltage in such networks are considered. The second part of the article presents the results of a study, on an active electric network physical model, of decentralized multiagent restoration of the integrity and normal operation of the network after its disintegration into isolated parts by an accident or emergency control system operation.

Active Power Distribution Networks with Decentralized Multi-Agent Control Mode. Part 1

The article focuses on decentralization and multi-agent automatic control as applied to the key system tasks of managing the general mode of an electric grid with distributed generation. The list of these tasks includes maintaining active and reactive power balances in normal modes, emergency control, maintaining the power supply system operability in post-emergency modes, etc. The methods for decentralized solution of these tasks, which have been tested on power system physical models and in a pilot MiniGrid project, are proposed. The developed MiniGrid is integrated with an external electrical network using a control system that is an agent of a multi-agent system. A conclusion about the possibility of developing a technology for decentralized control of operation modes in electric networks with distributed small generation is drawn. In the first part of the article, the terminology used is given, and the concept of the subject of a system for multi-agent control of operation modes in electric networks with distributed generation is given. Matters concerned with multi-agent decentralized frequency and voltage closed-loop control in an electric network with distributed generation are considered.

Reactive Power Compensation Configuration of Offshore Wind Power Based on Economic Differential Pressure Theory

The conventional reactive power balance analysis method for offshore wind power transmission projects can be used to obtain many feasible solutions for reactive power compensation configuration, which requires a large number of simulation calculations to eliminate unreasonable schemes. The work is tedious and lacks theoretical guidance. In this paper, the main influencing factors, such as the current carrying capacity of offshore wind power and submarine cable, the mode of real-time power generation, and the reactive power output regulation of the wind turbine itself, are considered. The reactive power balance of offshore wind power transmission projects is derived. Combined with the economic differential pressure theory, the sea-side and land-side configuration methods of high reactance and dynamic reactive power compensation are put forward. On the basis of realizing real-time reactive power balance, the recommended reactive power compensation configuration scheme effectively reduces the active power loss of the transmission project, and at the same time, lowers the bus voltage of each node at sea, thus reducing the high risk of the excessive voltage of offshore wind farm. This project is supported by the Science and Technology Project of State Grid Corporation of China under “Research on multiple temporal and spatial coordinated optimal control theory for medium and long-distance large-scale offshore wind power transmission system” (No. 5100-202155305A-0-0-00).