Reactive Power Sources Research Articles

Optimal allocation of EV charging station and capacitors considering reliability using a hybrid optimization approach

This paper proposes a novel approach for strategically placing EV charging stations (EVCS) and capacitors within electrical distribution networks (EDN) to mitigate issues arising from the widespread adoption of Electric Vehicles (EVs). The goal is to maximize the net present value (NPV) by reducing energy losses and minimizing system interruption costs while ensuring reliability. To achieve this, the paper introduces a hybrid optimization technique called HGP_CS, which combines Grey Wolf Optimization (GWO), Particle Swarm Optimization (PSO), and Cuckoo Search optimization methods. By employing various compensation coefficients to assess failure rates and identify strategies for enhancing NPV, the approach aims to optimize the placement of EVCS and capacitors within the EDN. Validation is carried out in IEEE 33-bus and 118-bus systems to demonstrate the performance of the proposed approach. It is found that the proposed approach, compared to the base case, reduced the energy loss cost by 34.19% and 31.57% and also the Expected Interruption Costs (EIC) by 17.26% and 13.41%, for IEEE 33-bus and 118-bus system, respectively. Additionally, the proposed method is economically beneficial as it can attain higher profits. In IEEE 33- bus and 118 bus systems, the annual net profit using the proposed approach is 36,805 $/year and 271,670.72 $/year, respectively. Thus, the proposed technique enhances the overall system performance and significantly boosts profitability, making it a compelling choice for optimizing the placement of charging stations and reactive power sources in networks.

Assessment of the quality of electricity by applying reactive power sources

In the quest to enhance electricity quality, various states and parameters play crucial roles, particularly in assessing the significance and capabilities of reactive power sources. The evolution of electricity systems in developed nations is marked by a vigorous pursuit of cutting-edge technologies to boost energy system efficiency, lower construction and operational costs of network infrastructure, and enhance power supply reliability. The issue of reactive power compensation and electricity quality is intricately linked to diverse consumer loads, voltage, and frequency considerations. This process entails elevating the system's active power factor to harmonize total power within the AC network, maintaining voltage levels, and mitigating harmonic distortions stemming from nonlinear industrial loads. Voltage stability measures are typically essential to curtail fluctuations along power transmission lines. Enhancing the system's operational reliability involves augmenting the maximum active power that reactive power compensation mechanisms can adjust.

A real-time PMU-based optimal operation strategy for active and reactive power sources in smart distribution systems

A real-time PMU-based optimal operation strategy for active and reactive power sources in smart distribution systems

Limits of reactive power compensation of a doubly fed induction generator based wind turbine system

The doubly fed induction generator (DFIG) systems feature a significant amount of free power capacity that may be used for reactive power adjustment when they are put into practical use. This change, which is occasionally overlooked, is a significant one. Using DFIG systems for wind turbines (WT), this paper explored strategies for reducing and using reactive power. In order to investigate the power characteristic and how it is regulated in DFIG systems, a mathematical model for the steady-state performance of DFIG WT has been developed and presented. Here is a detailed derivation of the limiting range of DFIG's reactive power capacity as well as the physical constraints on reactive power output. The distribution of the DFIG WT at a distribution network's end is demonstrated by a simulation example. Within this simulation, reactive power management strategy, load fluctuation, and the change in wind speed are all taken into consideration. Due to the possibility of a rise in the voltage at the access point, can concluded that both acceptable and efficient to use DFIG WT's reactive power capabilities as an additional continuous reactive power source for effectiveness.

Simulation of Voltage Stability Enhancement at Primary Substation Using Static VAR Compensator

For the voltage stability enhancement of power system, the reactive power compensation is vital important. With the advancement in technology, the Flexible AC Transmission System Devices (FACTS) are widely used for stability improvement. In the primary substation, the stability is poor due to load conditions and system faults. In this research, the voltage stability enhancement for a Primary Substation using Static VAR (volt-amp reactive) compensator (SVC) is presented. SVC can be used to improve system voltage stability and addition of damping control. With the application of SVC, the voltage stability can be improved under normal condition as well as under contingency conditions. Shunt reactive power sources, including capacitive and inductive, are controlled by high power electronic switching devices in an SVC to enhance voltage stability. The goal of this attempt is to use SVC to improve the voltage stability of the 230/33 kV system. To evaluate the voltage stability improvement by SVC, a simulation model is implemented in Matlab/Simulink and performance analysis are carried out based on the simulation results.

A Dual Fundamental Current Extraction Controller for DSTATCOM in the Distribution System for Power Quality Improvement Under Non-Ideal Source Voltage Condition

Most of the controllers often fail to work properly when encountered with power quality (PQ) issues like unbalanced and distorted grid voltage conditions in three-phase distribution system (TPDS). To address this problem, usually a dynamic static compensator (DSTATCOM) is utilized in TPDS. For enhanced performance, a novel dual fundamental component extraction (DFCE) technique is proposed for generating reference currents (RC) in a TPDS exhausting DSTATCOM. The proposed controller is highly effective for reactive power compensation and source current harmonic suppression under source unbalanced voltages condition with nonlinear load conditions. For computation of RC and phase synchronization, the controller extracts the required fundamental voltage and current at the same time. Consequently, the controller is able to control DSTATCOM operation in TPDS without any phase locked loop (PLL) and low pass filter (LPF). For generation of fundamental components of voltage and current, projected controller utilizes the self-tuning filter (STF). The efficacy of the controller is established in comparison to existing controllers like synchronous reference frame theory, p-q theory and STF-p-q under different grid voltage conditions. To enhance PQ, the suggested controller works efficiently for fundamental current component extraction without using PLL and low/high pass filter in case of grid distorted voltage condition.

Improving and warning the static stability limit of complex power grid tie-line based on WAMS

In order to solve the technical problems of traditional power system classic formulas that are difficult to explain the static stability limit changes of power grid interconnection lines, as well as the difficulties in improving and warning the static stability limit power of interconnection lines, this paper provides a method for improving and warning the static stability limit of power grid interconnection lines. Firstly, based on the electrical quantities measured by the wide-area measurement system (WAMS) of the power grid, the equivalent reactance of the power grid interconnection lines, and the equivalent impedance from the high voltage side and medium voltage side of the three coil transformers on both sides of the interconnection line are determined. Secondly, under pre-set operation mode and constraint conditions, the configuration quantity and capacity of the dynamic reactive power sources on the medium voltage side of the three coil transformers on both sides of the interconnection line are determined. Finally, based on the determined configuration and pre-set operation mode of the dynamic reactive power sources on the medium voltage side of the three coil transformers on both sides of the interconnection line, the historical electrical quantities measured by WAMS. The static stability limit and static stability margin of the interconnection line are calculated, and warnings are provided.

Modeling of modes of traction power supply systems equipped with renewable energy sources

The article presents the results of research aimed at developing digital models for power flow analysis of railway power supply systems (RPSS) equipped with distributed generation (DG) units based on renewable energy sources. We employed the technique of modeling in the phase reference frame, which has the following features: system-wide consistency, which enables modeling power flows in a way that takes into account the properties and characteristics of a complex RPSS and the feeding power system; versatility, which allows for modeling of traction networks of various designs; comprehensiveness, which consists in the possibility of power flow analysis of normal, emergency, and special states of a RPSS, such as those occurring during de-icing of overhead contact system wires. Three groups of models have been developed. The first one was designed for power flow analysis RPSSs with DG units based on synchronous generators driven by mini-HPP turbines. It is also possible to apply this model in the case of inverter generation that uses photovoltaic panels. The second group of models provided simulation of RPSS power flows with induction generators. The third group enabled power flow analysis in the case where there are three-phase generators connected to a single-phase traction network by means of Steinmetz converters. Active harmonic conditioners and controlled reactive power sources were used to reduce the negative impact of inferior power quality on voltage deviations and harmonic distortion. Simulation results produced by the software package Fazonord showed that the following positive effects can be obtained on the basis of the use of RES-based DG units: reduced costs of power supply; reduced imbalance on the buses of district windings of traction substations, stabilization of voltage levels on bow collectors of electric locomotives.

GA-Based Voltage Optimization of Distribution Feeder with High-Penetration of DERs Using Megawatt-Scale Units

In this paper, genetic algorithm (GA)-based voltage optimization of a modified IEEE-34 node distribution feeder with high penetration of distributed energy resources (DERs) is proposed using two megawatt-scale reactive power sources. Traditional voltage support units present in distribution grids are not suitable for DER-rich feeders, while voltage support using small-scale DERs present in the feeder requires considerable communication effort to reach a global solution. In this work, two megawatt-scale units are placed to improve the voltage profile across the IEEE 34-node feeder, which has been modified to include several PV units and an energy storage unit. The megawatt-scale units are optimized using GA for fast and accurate operation. The performance of the proposed scheme is verified using simulation results with a multi-platform setup where the modified IEEE-34 node feeder is modeled in OpenDSS while the GA optimization scheme is programmed in MATLAB.

A Novel Voltage/var Sensitivity Calculation Method to Partition the Distribution Network Containing Renewable Energy

Abstract: As the current calculation method of voltage/var sensitivity (VVS) could not reflect the temporal variations of power sources and load, the paper proposes a novel VVS calculation method to partition the distribution network containing renewable energy. Firstly, the defects of the existing VVS calculation methods are analyzed, and a novel VVS calculation method is proposed by adding reactive power output perturbation to the reactive power source. Secondly, the VVS matrix is fuzzified to obtain the membership matrix between each node. Based on the membership relationship between the reactive power source nodes, the nodes with a strong coupling relationship are merged to determine the initial number of partitioning. Then, the final partitioning result is determined according to the affiliation between each load node and each reactive power source. Finally, the partitioning result is evaluated based on the partitioning membership indexes. The proposed approach is tested on the IEEE 33-node distribution test system, and numerical simulations verify the high efficiency of partitioning. The simulation results show that the proposed method can reflect the temporal variations of power sources and load, and ensure the reasonable distribution of voltage and reactive power in each zone. Background: The voltage/var control of the power system is an important means to ensure the safe and economically stable operation of the system. Objective: The paper proposes a novel VVS calculation method to partition the distribution network containing renewable energy. Method: Firstly, the existing problems of electrical distance index are analyzed. A novel VVS matrix calculation method is proposed, which calculates the VVS of each reactive power source to the remaining nodes by adding voltage/var output perturbation to the reactive power source. Secondly, the VVS matrix is fuzzified to obtain the membership matrix between each node. Based on the membership relationship between the reactive power source nodes, the power supply nodes with strong coupling relationship are merged to determine the initial number of the partitioning. Then, the final partitioning result is determined according to the affiliation between each load node and each reactive power source. Finally, the partitioning result is evaluated based on the sensitivity index of membership degree. Results: The proposed approach is tested on the IEEE 33-node distribution test system and numerical simulations verify high efficiency of the partitioning. The simulation results show that the proposed method can reflect the temporal variations of power sources and load, and ensure the reasonable distribution of voltage and reactive power in each zone. Conclusion: The proposed method can reflect the temporal variations of power sources and load, and ensure the reasonable distribution of voltage and reactive power in each zone. This paper proposed a fuzzy clustering partitioning based on a novel calculation method of VVS, which is suitable for the problem of variable voltage /var running state of the system under high-proportion DG access.

Reactive power potential of converter-connected renewables using convex power flow optimization

Converter-connected renewable energy sources (RES) in the distribution network alter the power flow in the network. Often, grid reinforcements and additional local reactive power sources are needed to maintain steady state network operation. Converter-connected RES is an accessible local reactive power source for distribution system operators to optimize network operations. However, the non-linearity and non-convexity in the converter equations make their modelling challenging, which further results in the under-utilization of the reactive power capability from these sources. Oftentimes, the converter-connected generator is partially modelled using only apparent power constraints. This paper presents an approach based on Schur’s complement and piecewise planar approximation to incorporate the converter equations in a convex power flow optimization routine. The advantages of employing complete converter capabilities for optimal operation of the distribution network are studied via simulations on a real distribution network dataset. A comparison between deploying reactive power according to the minimum grid codes requirement, partial modelling of the converter, and complete converter capabilities is correspondingly presented. Active power losses decrease by 4.1% over 10 month period with high penetration of renewable generation. Furthermore, the voltage profile in the distribution network is improved and the reactive power dependency on the transmission network is reduced.

THE DIFFERENT APPROACHES TO THE TRANSFORMATION OF REACTIVE POWER INTO AN ACTIVE POWER

The relevance of the development of modern problems of the electric power industry in connection with the depletion of the planet’s natural resources is undeniable and initiates the development of new physical and technical solutions with the practical use of known natural phenomena. The method of this work is to propose, justifying the expediency of a possible scheme of a resonant converter of reactive power into activity and conducting an analysis of the electromagnetic processes occurring in them. The proposed schemes combine the presence of resonant parallel and resonant circuit complexes. The difference is in the way they are implemented. For the data of the joint circuit, the feature is the presence of two inductively coupled active-reactive circuits, but different in the ways of creating resonance conditions. For a circuit without an additional power source, it is shown that the successful implementation of resonance conditions is possible by choosing the appropriate element base. For a circuit with an additional source of harmonic voltage, it is shown that for a suitable setting it is possible to completely eliminate the negative influence of the converter circuit on the source of reactive power. Calculations for the experimental model show that with the appropriate selection of the element base, it is possible to obtain a conversion factor of ~ 1.0 with a minimal effect on the current in reactive power sources. Given the calculated ratios, the mathematical apparatus of the theory of electric circuits was used to substantiate the principle possibility of resonant transformation of electrical energy. Thus, methods of calculating the characteristics of transient processes in closed circuits with active-reactive elements. For the first time, with the justification of practical power, we offer the possibilities of the scheme of resonant transformation of reactive power into active power, and an analysis of the electromagnetic processes occurring in them is carried out. The proposed work was initiated by the current needs of the electric power industry, caused by the depletion of natural resources and the rapidly growing needs of the world economy. The results of the work illustrate the practical possibilities of creating real schemes for converting reactive electricity into active electricity.

Transient voltage stability emergency control strategy for HVDC receiving end power grid based on global orthogonal collocation

When asynchronous motors, especially double-fed asynchronous motors in large capacity pump storage are the main loads in the high voltage direct current (HVDC) receiving end power grid, the increase of the equivalent slip of asynchronous motor load may cause transient voltage instability. In order to recover the voltage rapidly in the grid, the emergency reactive power support needs to be quick and accurate. A method for transient voltage stability emergency control by temporarily reducing DC current is proposed, the inverter station is used as emergency reactive power source for the HVDC receiving end power grid. In detail, firstly, aiming at the quantitative calculation of DC current, a nonlinear optimization model with the optimization variable of DC current and the objective of minimizing energy transmission reduction of HVDC is established. Further, in order to achieve fast solution and meet the accuracy requirements, global orthogonal collocation (GOC) is incorporated into the optimization model to transform the differential equations of both objective function and constraints into algebraic equations, thus the optimization is transformed into a nonlinear programming (NLP) problem, by which the emergency control strategy, in specific, the optimal DC current control scheme is obtained. Finally, the modified IEEE 14 benchmark is used to verify the effectiveness and superiority of the proposed strategy.

Post-emergency reconfiguration of a distribution network as a method for restoring power supply to consumers

The work is aimed at solving the problem of using reconfiguration and additional reactive power sources to restore power to consumers of the medium-voltage distribution network in the case of emergency disconnections of connections by bus section circuit breakers. The reconfiguration problem for a 118-node test distribution network is solved using a high-speed algorithm involving the construction of a maximum spanning tree on a network graph as the basis for determining information about the composition of branches and chords of independent circuits necessary to restore power following disconnection. To ensure acceptable voltage levels following power restoration, additional reactive power sources determined using singular Jacobian matrix analysis methods are installed in the sensor nodes of the network. For the test circuit, the modes for single disconnections of individual sectional switches, including in dead-end sections, are analysed. By optimally reconfiguring the network in the normal mode, it is possible to reduce voltage deviations from 13% to 7%. For the modes caused by disconnections of individual bus section circuit breakers that lead to unacceptable voltage deviations, the set-down locations and reactive power of additional sources are selected. In the most severe of the considered disconnection scenarios, the installation of additional sources provided a reduction in voltage deviations from 18 to 8%. Thus, the methods proposed by the authors make it possible to restore the test network mode following emergency disconnections and ensure that the voltages in the network nodes are maintained within acceptable limits, both in normal and in post-emergency modes.

Забезпечення енергоефективних режимів роботи в системах електрозабезпечення промислових і цивільних об’єктів шляхом регулювання напруги

The development of voltage regulation methods in the energy supply system of industrial and civil facilities using continuous and discrete sources of reactive power, tap-changer of GPP transformers and PBZ of shop transformers is an urgent task. It allows maintaining energy-efficient modes of powerconsuming equipment, elements of power supply and power consumption systems and reduce financial expenses for payment for electric energy. The article presents approaches to solving the task of determining energy-efficient voltage levels at different hierarchical levels of the power supply system and ensuring them by using voltage regulators (TAPs) of GPP transformers, PBZ switches of workshop transformers, as well as power regulation of reactive power sources. For the calculation of energy-efficient voltages, an appropriate algorithm has been developed, which provides the separate execution of operations for calculating the parameters of the current mode of the power supply system and its optimization. This allows to monitor the state of the power supply system and ensure the maximum efficiency of the use of voltage regulation devices. A method of determining the static load characteristics of asynchronous motors by voltage is proposed, taking into account their design features, mechanical load characteristics and magnetizing currents. A method of de termining the static characteristics of the load by voltage at the levels of the shop transformer, RP and GPP has been developed. With the use of the MATLAB/SIMULINK package, calculation studies of static characteristics by voltage at different levels of the hierarchical power supply system were carried out. The selection of the method for calculating the modes of shop and distribution electric networks of an industrial enterprise was reasoned. The static characteristics of the load according to the voltage, the action of the voltage regulators of the GPP trans formers, the position of the PBZ of the shop transformers, the power of the reactive power sources were taken into account. Algorithm for controlling discrete and continuous sources of reactive power and voltage regulators of GPP transformers was proposed taking into account static load characteristics to ensure energy-efficient operation modes of shop and distribution electrical networks of an industrial enterprise.

Optimal selection of single tuned passive filters to enhance post‐fault voltage recovery and power quality in a renewable integrated microgrid

AbstractThe harmonic currents produced by nonlinear loads and renewable energy sources (RES) like PV and wind energy have had a growing impact on industrial distribution networks in recent times. Along with harmonic distortions, lack of adequate reactive power support in a heavily loaded renewable‐rich industrial network has made the operation vulnerable to fault‐induced delayed voltage recovery (FIDVR). Due to poor post‐fault voltage recovery, an industrial microgrid is exposed to cascading loss of distributed generators (DGs). Dynamic var sources are being used to prevent cascade tripping. However, they may result in deterioration of the network's THD scenarios. Single tuned passive filters are widely used to suppress harmonic contents. The goal of this work is to design filters so that these become capable to lower overall harmonic distortion while also minimizing the risk of blackouts caused by inadequate post‐fault voltage recovery. To determine the allocation and rating of single tuned passive filters in a renewable‐penetrated industrial microgrid, an optimization model is developed. To show the feasibility and efficacy of the proposed formulation, simulations are performed on a modified IEEE 43 bus system. The findings suggest that the proposed design methodology produces effective solutions to minimize the necessity of additional reactive power sources.

Effective Utilization of Distributed Power Sources under Power Mismatch Conditions in Islanded Distribution Networks

The integration of distributed generation (DG) into a power distribution network allows the establishment of a microgrid (MG) system when the main grid experiences a malfunction or is undergoing maintenance. In this case, the power-generating capacity of distributed generators may be less than the load demand. This study presents a strategy for the effective utilization of deployed active and reactive power sources under power mismatch conditions in the islanded distribution networks. Initially, the DGs’ and capacitors’ optimal placement and capacity were identified using the Jaya algorithm (JA) with the aim to reduce power losses in the grid-connected mode. Later, the DG and capacitor combination’s optimal power factor was determined to withstand the islanded distribution network’s highest possible power demand in the event of a power mismatch. To assess the optimal value of the DG–capacitor pair’s operating power factor (pfsource) for the islanded operation, an analytical approach has been proposed that determines the best trade-off between power losses and the under-utilization of accessible generation. The test results on 33-bus and 69-bus IEEE distribution networks demonstrate that holding the islanded network’s load power factor (pfload) equal to pfsource during the power imbalance conditions allows the installed distributed sources to effectively operate at full capacity. As expected, the proposed strategy will assist the utility companies in designing efficient energy management or load shedding schemes to effectively cope with the power mismatch conditions.

Achieving Optimal Reactive Power Compensation in Distribution Grids by Using Industrial Compensation Systems

This paper presents a method for integrating industrial consumers owning compensation systems as alternative reactive power sources into grid operating processes. In remuneration, they receive a market-based provision of reactive power. The aim is to analyze the potential of reactive power compensation systems of industrial companies connected to medium-voltage (10 kV–30 kV) AC grids in order to increase the reactive power ability of distribution grids. Measurement methods and reactive power potential results of six industrial companies are presented to characterize the amount and temporal availability of their reactive power potential. The presented approach for using the decentralized reactive power potential is a centralized reactive power control method and is based on optimal power flow (OPF) calculations. An optimization algorithm based on linear programming is used to coordinate a reactive power retrieval tuned to the actual demand. The influencing quantities are the current grid status (voltage and load flow capacity reserves at grid nodes and power lines) and the current reactive power potential of the reactive power sources. The compensation impact of six measured industrial companies on an exemplary medium-voltage grid is shown by an application example.

Intelligent Optimized Voltage Control for Hybrid Off-Grid Power Systems

Hybrid off-grid power systems with different renewable and non-renewable energy sources, such as wind, photovoltaics, and diesel generation, have a wide application scope in regions where grid extension is not possible. To supply quality power, hybrid off-grid power systems need proper reactive power management to deal with randomly changing load and supply. In particular, to realize dependable and quality power supply, hybrid off-grid power systems require suitable and efficient control techniques. A properly tuned controller of reactive power sources is crucial to maintain a prescribed voltage profile. Computational intelligence techniques such as particle swarm optimization can provide desired and acceptable solutions for optimization problems. In this study, we applied computational intelligent techniques for optimal control of reactive power sources, such as photovoltaic inverters and automatic voltage regulators for synchronous generators in diesel engines, to investigate dynamic voltage profile stability through reactive power management.

Analysis of the Influence of Nodal Reactive Powers on Voltages in a Power System

The paper deals with finding power system nodes where reactive powers have the greatest influence on system voltages. The problem to be solved is important in reactive power planning. Its proper solution indicates in which nodes new sources of reactive power should be installed in order to achieve the assumed goals in the aforementioned planning. So far, the problem formulated earlier has not been satisfactorily resolved. The paper presents an original method, which, based on the entire history of the system operation states, allows a solution to the problem mentioned above to be found. The proposed method assumes the use of measurement data of nodal-voltage magnitudes and nodal reactive power. Correlational relationships between the above-mentioned quantities are investigated. The paper shows that the considered correlational relationships are not linear. In this situation, Kendall’s rank correlation coefficient is used to evaluate the strength of these correlational relationships. Analysis of the strongest relationships allows us to identify those nodal reactive powers that have the greatest influence on the voltages in the power system. The results of the analysis are the basis for determining the location of additional reactive power sources in the power system, which is very essential in reactive power planning. The proposed method is relatively easy to implement and does not require complicated calculations. The paper additionally shows that failure to use the entire spectrum of representative system states when solving the problem under consideration can adversely affect the result.