Search

The work reported in this paper aims at developing an algorithm for system operators to solve a robust security-constrained AC optimal power flow (R-SC-ACOPF) problem, which also optimizes the settings of discrete controllers including load tap changers (LTCs) and shunt capacitor banks (SCBs). An iterative algorithm involving a master problem and a number of sub-problems is proposed. The master problem selects the optimal discrete controllers’ settings by taking into account primal SC-ACOPF constraints based on the single-component worst contingencies identified by the sub-problems. Each sub-problem is a bi-level max-min problem used to find the current worst contingency. The overall objective is to minimize the total cost, including generation and load shedding cost, while satisfying all relevant constraints. The master problem and sub-problems allow representing LTC tap positions, SCB status, and contingencies using binary variables. Two case studies are presented as applications of this novel technique. [ABSTRACT FROM AUTHOR]

The paper presents the results of experimental studies on the developed bone degreasing stand. The object of the study is the production of valuable components from organic raw materials. Fractions of cattle crushed to the size of 2.5 mm, 5.2 mm and 10.5 mm were used to identify the effective mode of operation of an electrohydroimpulse installation. Physical and chemical methods of fat extraction are currently not relevant from the point of view of economy, due to environmental damage and labor intensity. In this regard, new effective methods of extracting fat from bone mass are needed. Therefore, the proposed method of extracting fat by spark discharge is an actual and alternative method for today. During the study, an acceptable temperature regime for fat production was obtained. Next, a laboratory stand was assembled, with which you can degrease the bone mass without changing the properties of fat. Experimental studies show that with an increase in the capacity of the capacitor bank in energy storage devices and the length of the discharge gap, the bone degreasing process becomes more efficient. During the study, it was found that at a liquid temperature of 38 °C and a pulse voltage of 25 kV on a switching device of an electrohydroimpulse installation, the degree of fat extraction increases without destroying the morphological structure of bone mass. Using the hexane extraction reaction, we determined the efficiency of fat extraction at a temperature of 38 °C, at which the fat mass from the bones is effectively broken down, and using the UV-1800 spectrophotometer, we determined the amount of protein in the bones before and after treatment. The study also showed that with a capacitor bank capacity of 0.5 uF, crushed to a fraction of 10.5 mm of pelvic bone, the separated fat is 18.7 %, and with constant grinding of the capacitor bank to a fraction of 2.5 mm – 19.4 % [ABSTRACT FROM AUTHOR]

This study presents an energy regeneration model and some theory required to construct a regeneration braking system. Due to the effects of carbon dioxide (CO2) emissions, there is increasing interest in the use of electric vehicles (EVs), electric bikes, electric bicycles, electric buses and electric aircraft globally. In order to promote the use of electric transportation systems, there is a need to underscore the impact of net zero emissions. The development of EVs requires regenerating braking system. This study presents the advantages of regenerative braking. This system is globally seen in applications such as electric cars, trams, and trains. In this study, the design specification, design methodology, testing configurations, Simulink model, and recommendations will be outlined. A unique element of this work is the practical experiment that was carried out using 1.5 Amps with no load and 2.15 Amps with a load. The discharge voltage was purely from the 22 W bulb load connected to the capacitor bank as we limited this study to the use of 1.5 Amps and it took 15 min for a full discharge cycle, after which no charge was left in the capacitor bank. The results showed that the discharge rate and charging rate for the regenerative braking system were effective but could be improved. The objective of this paper is to investigate how a supercapacitor works alongside a battery in regenerative braking applications. This study demonstrates that the superconductor used can deliver maximum power when required. Also, it can also withstand elevated peaks in charging or discharging current via the supercapacitor. Combining a battery with a supercapacitor reduces the abrupt load on the battery by shifting it to the capacitor. When these two combinations are used in tandem, the battery pack's endurance and lifespan are both boosted. [ABSTRACT FROM AUTHOR]

The high resistance connection fault of the stator is a common fault in doubly fed induction generators, which causes a three-phase imbalance in the stator circuit. Since the stator winding is directly connected to the power grid, interference from the asymmetric power grid must be eliminated in order to achieve the accurate diagnosis of stator resistance imbalance faults. Therefore, a new diagnosis method based on filter shunt capacitor banks is proposed in this paper. By introducing shunt capacitor banks, an artificial neutral point is constructed to replace the neutral point of the power grid. Then, the neutral point voltage of the stator winding relative to the artificial neutral point is selected as a fault characteristic signal. In this paper, the change in three-phase stator currents after a high-resistance connection fault is analyzed in detail, and by comparing the fault characteristic signal with three-phase stator currents, the fault phase location and fault severity of high-resistance connection can be accurately obtained. Finally, simulations are carried out via the field-circuit coupling method to validate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

The protection of traditional high‐voltage capacitor banks relies on an unbalance relay which operates when an internal fuse is blown. However, the unbalance relay cannot indicate the cause of the fault. Thus, an operator wastes time and human resources investigating the fault issues. In this paper, a fault which occurred in a 230‐kV power system of Electricity Generating Authority of Thailand was observed by performing simulations using the Power Systems Computer Aided Design (PSCAD) program. The study system based on the double bus station and 72 MVAR capacitor banks was installed in the form of a back‐to‐back topology. Three scenarios were considered: normal condition, fault occurrence in one capacitor bank and fault occurrence in both capacitor banks. Current characteristics such as the current phase and difference in unbalance current were considered. In addition, discrete wavelet transform was applied to solve the ambiguity of current generated from the PSCAD. The authors' results suggest that identifying fault events using a coefficient of wavelet is more efficient than relying on the current amplitude. The findings mentioned in this paper can be applied in a traditional power system protection scheme to enhance a system's reliability. [ABSTRACT FROM AUTHOR]

As the electricity market expands with increasing demand, power systems are under more pressure to operate within secure limits. One way to ensure this is through load flow studies, which analyze the steady-state conditions of a power system under various load and generator scenarios. However, the complexity of power systems and the growing demand for electricity make it difficult to accurately predict and analyze power flow. The use of simulation software like electrical transient and analysis program (ETAP) can improve the accuracy and efficiency of load flow studies, but it still poses challenges such as complexity and lack of standardization in use. This paper focuses on voltage stability, voltage regulation, and the impact of capacitor banks on buses through load flow studies. Real data from four hydropower plants is used to analyze voltage drop, voltage regulation and power losses at each bus. The findings highlight the effectiveness of capacitor banks in improving voltage profiles and reducing power losses, thus proposing an optimized system design. These enhancements facilitate better planning, operation, and expansion of power systems, ensuring more reliable and efficient electricity supply. [ABSTRACT FROM AUTHOR]

Protection relays are important equipment used for protection, control, and metering functions in the power grid. These relays are used to protect critical and difficult-to-replace equipment, like generators, transformers, and capacitor banks. Once the protection devices are disturbed or damaged, a high risk of power generation interruption occurs. Therefore, it is important and necessary to study the relay's immunity to electromagnetic pulse (EMP) events. As a preliminary step toward empirical experimentation on actual equipment, this manuscript outlines an economical and efficient methodology for evaluating the impact of an EMP. An impedance measurement strategy was employed to model the equipment, setting the stage for subsequent immunity analyses. These analyses included the pulse current injection (PCI) method, which utilized an injecting probe to introduce the transient, and frequency domain electromagnetic (FEKO) simulation, which integrated electromagnetic coupling effects into the transient simulation. The impedance measurement and simulation results in this paper provide a reliable basis for gauging equipment performance in the face of HEMP threats. The results obtained using the PCI and FEKO simulations demonstrated the performance of different port responses under a high-altitude EMP, indicating the requirement for some protection to ensure the reliable operation of relays. [ABSTRACT FROM AUTHOR]

In power engineering, the importance of maintaining a high power factor in low-voltage electrical installations is known. In power substations for industry, the usual method of coupling is to use an automatic power factor controller which connects capacitors banks (with electromagnetic contactors). Sometimes, AC reactors are connected to the phases of the capacitors banks (to reduce transient phenomena and the deforming regime), depending on the desired value of the power factor. This paper presents an analysis (more focused on experimentation) of a low-cost system for automatic regulation of the power factor with a reduction in transients and an increase in the life of contactors (eliminating the electric arc during switching on), with capacitors banks for low-voltage three-phase installations that connect the capacitors banks by means of one three-phase solid-state relay (an expensive device for a quality device; one is used for all capacitors banks) and using several electromagnetic contactors. The automatic power factor adjustment system has a controller with a microprocessor with six outputs, controlled by the phase shift between the current (measured with a current transformer proportional to the current in a bar) and the phase voltage, which is part of a system of distribution bars (L1,2,3, N) from which electrical consumers (e.g., induction motors) are supplied. To reduce transients when connecting capacitors banks, a three-phase solid-state relay and two related electromagnetic contactors are used for each capacitors bank. The automatic power factor controller is connected to two low-capacity PLCs that control the logic of connecting the capacitors banks to reduce transients. By using the proposed regulation system, a cheaper control solution is obtained compared to the use of one solid-state relay for each capacitors banks, under the conditions in which the power factor adjustment is made as in the classic solution. If twelve capacitors banks are used, the proposed installation is 22.57% cheaper than the classical power factor regulation installation. [ABSTRACT FROM AUTHOR]

Integrating Renewable Energy (RE) into Distribution Power Networks (DPNs) is a choice for efficient and sustainable electricity. Controlling the power factor of these sources is one of the techniques employed to manage the power loss of the grid. Capacitor banks have been employed to control phantom power, improving voltage and reducing power losses for several decades. The voltage sag and the significant power losses in the Iraqi DPN make it good evidence to be a case study proving the efficiency enhancement by adjusting the RE power factor. Therefore, this paper studies a part of the Iraqi network in a windy and sunny region, the Badra-Zurbatya-11 kV feeder, in the Wasit governorate. A substation of hybrid RE sources is connected to this feeder to compensate for the low voltage and high power losses within three different electricity demand conditions: low, medium, and high. The results are compared with a case when an optimum capacitor placement is applied. By using the CYME 9 software for analysis, the research shows the benefits of adding RE to the grid. The results have approved the hybrid RE penetration benefits as the power losses are reduced in low, medium, and high scenarios by 36.26%, 43%, and 48.4%, respectively, besides the voltage sag elimination. [ABSTRACT FROM AUTHOR]

Power distribution systems (PDS) are the infrastructure and equipment used to distribute electricity from the transmission system to end-users, such as homes and businesses. PDS are usually designed to operate in a radial mode, where power flows from one substation to the end user through a series of feeders. The extension of distribution lines to attend new customers along with the growing demand for electricity result in increased energy losses and voltage reductions. Various solutions have been proposed to solve these issues, such as selecting the optimal set of conductors, optimizing the placement of voltage regulators, using capacitor banks, reconfiguring the distribution system, and implementing distributed generation. A well-known approach for reducing energy losses and enhancing voltage profile is the optimal conductor selection (OCS). While this can be beneficial, it may not be sufficient to fully reduce technical losses and improve the system voltage profile; therefore, it must be combined with other strategies. This paper presents a new approach that combines the OCS with the optimal placement of capacitor banks (OPCB) to minimize technical losses and improve the voltage profile in PDS. The main contribution of this paper is the integration of these two problems into a single mixed integer linear programming (MILP) model, therefore guaranteeing the achievement of globally optimal solutions. Three test systems of 27, 69, and 85 buses were used to illustrate the effectiveness of the proposed modeling approach. The results indicate that the combination of OCS and OPCB effectively minimizes energy losses and enhances the voltage profile. In all cases, the solutions obtained by the proposed MILP approach were better than those previously reported through metaheuristics for the combined OCS and OPCB problem. [ABSTRACT FROM AUTHOR]

The railway traction loads produce massive harmonics that are injected directly into the traction power system. This causes serious waveform distortion in the supply voltage and even invokes a harmonic parallel resonance, which may lead to significant harmonic current and voltage amplification. Consequently, severe electrical equipment failures and feeder tripping problems occurred frequently in the traction substation. A clear harmonic parallel resonance at a 27.5‐kV feeder can be observed from the field measurement result of the traction substation without filter banks. This paper proposes a high‐performance single‐tuned 3rd passive filter for harmonic mitigation and harmonic resonance suppression in the traction power system. In the ST filter design process, the impact of the quality factor (Qf) design of the filter reactor on the filtering performance is considered. Furthermore, the driving point impedance as seen from the traction load is also studied. The design and the engineering consideration of the harmonic filter are also presented, which comply with the recommendations of the IEEE and IEC standards. Besides, the unbalance‐current protection of a capacitor bank is introduced in this paper. Finally, the proposed filter is implemented in an actual traction substation, from the field measurement results; the proposed harmonic filter delivers very good performance. [ABSTRACT FROM AUTHOR]

In this paper, it is proposed that a two-terminal high voltage direct current (HVDC) be integrated into the power system. Line-commutated converter (LCC)-HVDC is used because of its ability to reduce line losses, which improves overall system efficiency. Shunt capacitors also aid in voltage maintenance by compensating for the reactive power demand. In essence, limiting voltage drops in electrical networks promotes a more efficient power transmission and distribution by lowering resistive losses. In power system investigations, it was discovered that the HVDC link and SCB exist separately. So, for the first time, the backtracking search algorithm (BSA) is used to solve the optimal reactive power flow (ORPF) of a power system with a HVDC link and shunt capacitor banks (SCB). Although BSA simulations on a modified IEEE 30 bus yielded successful results, ABC was also utilized for comparing the outcomes of different methods. Overall, three separate cases of the modified IEEE 30 bus system were examined. When the acquired results are compared to other methods, the suggested algorithm is found to be better at concerning effectiveness as well as performance. [ABSTRACT FROM AUTHOR]

In this paper, an optimization approach based on an arithmetic optimization algorithm (AOA) is proposed for specifying the optimal allocation of distribution generations/generators (DGs) and capacitor banks (CBs) in radial distribution systems. The AOA is a new population-based meta-heuristic algorithm that is essentially based on using basic arithmetic operators in mathematics. The proposed approach is employed to specify the optimum placement, capacity, and power factor of DGs and CBs to decrease the distribution systems' total power loss and voltage deviation. To state the performance of the proposed approach, DGs and CBs are placed in IEEE 33-bus and 69-bus systems separately or together. When only DGs are used and the parameters of location, capacity, and power factor of DGs are determined simultaneously, the total active power loss reductions in the IEEE 33-bus and 69-bus systems are achieved at 94.42% and 98.03%, respectively. When the results of other optimization algorithms are examined, it is seen that better results are obtained with AOA. [ABSTRACT FROM AUTHOR]

This research paper addresses the limitations inherent in conventional volt-VAR control (VVC) mechanisms, such as on-load tap changers (OLTC) and voltage and capacitor banks (CBs), when applied to the implementation of efficient conservation voltage reduction (CVR) strategies within active distribution networks. In this paper, we present a cost-effective strategy that synergizes the rapid-response capabilities of PV smart inverters with traditional VVC mechanisms to enhance CVR operations. This study delves into the optimal coordination between photovoltaic smart inverters and conventional VVC systems for effective CVR operations. The investigation takes into account the implications of distribution network reconfiguration (DNR) on the overall operational costs, encompassing grid power procurement, emissions, losses, and switching expenses related to OLTC, CB, and remote controlled switches (RCS). To attain the optimal solution, we leverage the recent advancements of the white shark optimization (WSO) technique, meticulously validating its performance through extensive trials conducted on the 119-bus distribution system. The empirical results vividly showcase the substantial advantages of integrating VVC devices and smart inverters, particularly in scenarios characterized by fluctuating load conditions. Notably, the synergistic approach achieves a remarkable 6.51% reduction in energy consumption. Additionally, active and reactive power loss reductions of up to 33.67% and 28.55%, respectively, underscore the potency of the proposed strategy. [ABSTRACT FROM AUTHOR]

Copyright of Ingeniería (0121-750X) is the property of Ingenieria and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The capacitor bank and synchronous condenser have been the only available sources of reactive power. Nowadays, most of the appliances use a power electronic interface for their connection. Applying a power electronic interface addsmany features to these appliances. One of the promising features is their capability to interact with Volt-VAR programs. In this paper was investigated the reactive power interaction of the end-user appliances. For this purpose, the distribution network buses are ranked based on their effectiveness, followed by studying their interaction in the Volt-VAR program. To be able to consider the uncertainties, Probability Density Function (PDF) curve was discretized to represent different scenarios, and the reduction method was utilized to reduce the situations. [ABSTRACT FROM AUTHOR]

This paper presents a dual active bridge DC/DC converter used as an AC current compensator in a hybrid energy storage application. The AC current in the DC link appears when a three-phase, four-wire inverter operates with unbalanced output currents—for example, when trying to compensate for grid voltage unbalance. This AC current has adverse effects on the operation of the electrochemical energy storage, and it should be compensated. To achieve this, a compensator is introduced into the DC link circuit of the inverter—a DC/DC converter with a capacitor bank. The DC/DC converter is responsible for compensating the AC pulsation by creating its own pulsation with the opposite phase. In the paper, the genesis of this pulsation is explained, and a compensation circuit is proposed along with a sensorless compensation algorithm. The algorithm is based on symmetrical decomposition and is used to generate a reference signal for the compensator. The numerical analysis of the algorithm is presented, and the operation of the compensator is verified on the laboratory bench. [ABSTRACT FROM AUTHOR]

This paper exhibits the coordinated control of 30 kVAr Distribution STATic synchronous COMpensator (DSTATCOM) with 125 kVAr Switchable Capacitor Banks for compensation of reactive power in a 750 kVA secondary radial distribution system. With the control of reactive power in a radial distribution system, the power factor can be improved near to unity. The selected radial distribution system mainly feeding power to vital loads of an Educational Institution. In this paper, the study of 750 kVA secondary radial distribution system is analyzed in terms of electrical power system of institute, power consumption pattern and tariff related issues. Some conclusions to improve the system performance in terms of power factor and reduction in tariff were drawn. The coordinated control of switchable capacitor bank and DSTATCOM performance depends on the calculation of the reference source currents that generates the gating pulses of the voltage source converter-based DSTATCOM. For this purpose, the control strategy adopted is Real and Reactive power (PQ) control, Synchronous Reference Frame theory, Back Propagation Control algorithm and Adaptive Linear (ADALINE) control is implemented in this system using MATLAB/SIMULINK software. Generation of the PWM pulses triggers the IGBT of the VSI-based DSTATCOM. This is achieved using DSP TMS 320 F 2812, a 32-bit processor that is programmed with CCS V3.3 and C2000 embedded code generation tool using MATLAB/Simulink, and the same is being executed with code composer studio V 6.0.1. The performance of the selected secondary radial distribution system is analyzed experimentally in a hardware prototype to evaluate the effect of DSTATCOM and switchable capacitor bank. [ABSTRACT FROM AUTHOR]

This paper introduces the design and fabrication of a versatile capacitor bank developed specifically for its integration within the innovative flash joule heating (FJH) technique, aimed at synthesizing graphene. The capacitor bank offers two adaptable configurations, providing options for capacitance at 180,000 µF and 68,000 µF, combined with a maximum charging capability of 400 V. This equipment facilitates the swift conversion of carbon-containing materials into graphene by harnessing transient current discharges. The proposed capacitor bank facilitates the execution of comprehensive research pertaining to graphene production from diverse carbon sources, opening an opportunity for advancing exploration within this rapidly evolving field of study in Ecuador. [ABSTRACT FROM AUTHOR]

Power distribution systems (PDS) comprise essential electrical components and infrastructure that facilitate the delivery of electrical energy from a power transmission system to end users. Typically, the topology of distribution systems is radial, so that power goes from the substations to end users through main lines or feeders. However, the expansion of new feeders to accommodate new users and ever-growing energy demand have led to higher energy losses and deterioration of the voltage profile. To address these challenges, several solutions have been proposed, including the selection of optimal conductors, allocation of voltage regulators, utilization of capacitor banks, implementation of distributed generation, and optimal reconfiguration. Although reconfiguring the network is the most cost-effective approach, this solution might not be sufficient to completely minimize technical losses and improve system performance. This paper presents a novel approach that combines optimal distribution network reconfiguration (ODNR) with optimal conductor selection (OCS) to minimize power losses and enhance the voltage profiles of PDS. The key contribution lies in the integration of the ODNR and OCS into a single MILP problem, ensuring the attainment of globally optimal solutions. The proposed model was tested with benchmark 33-, 69-, and 85-bus test systems. The results allowed us to conclude that the combined effect of ODNR and OCS presents better results than when any of these approaches are applied either separately or sequentially. [ABSTRACT FROM AUTHOR]

The structure complexity and the extended geographical area are among the factors that create challenges in accurate fault location and detection in distribution networks. The single‐phase to ground (SPG) faults are considered as most frequent reasons for distribution network interruption, which can threaten the network's reliability. Signal processing methods are usually used as common approaches to distinguish and locate faults in distribution networks. This paper proposes a novel scenario to select optimal wavelet packet transform (WPT) coefficients for SPG fault location and a method based on superimposed voltage energy to distinguish the faulty phase according to these coefficients. Furthermore, employing the energies of the superimposed voltages helps to minimize the effects of high resistance faults (HRFs) and load encroachment on the efficiency of the faulty phase detection part. Comparing the obtained results with other scenarios demonstrates the considerable efficiency of the proposed scenario. Finally, with the help of general regression neural networks (GRNN) as machine‐learning tools, a new algorithm is derived for detecting and locating the SPG fault and capacitor bank switching overvoltage (COV). Simulation results are implemented on the IEEE 34‐bus standard distribution network, demonstrating the efficiency and superiority of the suggested method. [ABSTRACT FROM AUTHOR]

In this paper, a graph theory-based allocation methodology of capacitor bank is proposed for unbalanced distribution system. A single-stage optimization procedure using electrical centrality measure concept to identify the best suitable locations for the multi-point connection of capacitor is described with its significance. The electrical centrality measure approach gives ranking of all the buses, single capacitor or multiple capacitors can be placed in unbalanced distribution system (UDS) using these indices to fulfill the reactive power demand and maintain voltage profile of the system. To evaluate the performance of the UDS due to capacitor bank connection two parameters are considered – improvement of overall voltage profile and reduction of active power loss. The contribution of the paper is – first, electrical centrality measure is used for identifying the capacitor bank location in the unbalanced distribution system and second it optimizes the size of the capacitor using two different objectives to improve the system voltage profile and reduce the active power loss. The proposed methodology is tested on a modified 123 bus unbalanced distribution system. The active power loss reduction up to 16.50% and total voltage deviation reduction up to 71.53% were achieved using the proposed method. The obtained results corresponding to the two objectives are also compared. [ABSTRACT FROM AUTHOR]

Islanding is one of the important challenges in power networks in the presence of distributed generation which is considered an undesirable incident due to the possibility of damage to operators, network equipment, and consumers. Therefore, it is necessary to quickly detect islanding and make a decision regarding the connection status of local distributed generation units in the network. In this paper, a passive islanding detection method is proposed using adaptive threshold-based instantaneous frequency droop characteristic. The proposed threshold limit is dynamically changed depending on under-studied conditions to discriminate the island from load changes, capacitor bank switching, motor start-up, and short circuit types. Two medium voltage networks of Cigre and 34-bus IEEE are used to evaluate the proposed method. The simulations are performed in Digsilent software and the proposed method is implemented in MATLAB software. The simulation results indicate that the island is correctly detected with appropriate accuracy in a short period of time from other disturbances in the presence of wind, solar and diesel types of distributed generations. [ABSTRACT FROM AUTHOR]

With the increasing proportion of wind power access year by year, it brings many challenges to the voltage stability of power systems. In order to maintain the stability of the voltage in the power grid, it is impossible to take into account the regulation ability and economy when a single reactive power compensation device is installed. In this paper, a combined reactive power compensation device was installed, which is composed of a static var generator (SVG) and a parallel capacitor bank. The SVG has the characteristics of fast and smooth adjustment, and the application of the capacitor bank reduces the overall investment cost and has a great economy. The modal analysis method was used to find the optimal installation position for the reactive power compensation device. The improved particle swarm algorithm was used to optimize the capacity of the optimal reactive power compensation device to ensure the best performance of the compensation device. Finally, by formulating the control strategy of the combined reactive power compensation system, the reliable switching of the compensation device is controlled. The PSCAD simulation software was used to model the power grid in the Hami area, and six different configuration programs were set for static voltage stability simulation verification and three different configurations. The program was simulated and verified for transient voltage stability, and comparative analysis showed that the proposed method was correct, which strongly supports the voltage stability of the region and meets the demand of reactive power compensation of the power grid. This provides a good reference program for other wind power gathering areas. [ABSTRACT FROM AUTHOR]

Shunt capacitors are usually installed in distribution grids for power factor correction. On the other hand, the number of harmonic‐producing sources such as wind turbines (WTs), photovoltaic (PV) panels, storage units, and electronic loads is rapidly growing in distribution grids. Since improper placement and sizing of shunt capacitors in harmonic‐polluted grids may aggravate power quality conditions and lead to harmonic resonance, special attention should be paid to this optimization problem when harmonics are present. In this paper, a framework based on shuffled frog leaping algorithm (SFLA) is proposed for optimal placement of fixed capacitor banks. Moreover, a resonance index (RI) is proposed for assessment and mitigation of potential harmonic resonance based on resonance mode analysis (RMA). The resonance mitigation method helps in avoiding power quality constraint violations and directs the algorithm toward the feasible solution space. It thus results in a higher efficiency, and the chance of reaching (near) globally optimum solutions increases. The proposed algorithm is particularly useful when detailed data regarding the harmonic injection pattern of nonlinear sources is not available. The proposed framework is implemented on the IEEE 18, 34, and 69‐bus test systems, and the results demonstrate its advantages, especially in larger grids. [ABSTRACT FROM AUTHOR]

This paper describes the upgradation of power supply systems for the improved performance of a small spherical tokamak (MT-I) with an aspect ratio of 1.67 in operation at the Pakistan Tokamak Plasma Research Institute (PTPRI), Islamabad. Three mutually independent power supplies are designed to generate current pulses of desired shape and magnitude in central solenoid (CS), toroidal field (TF) and vertical field (VF) coil systems. The main parts of a power supply are capacitor banks as energy storage devices, ignitrons and thyristors as fast switches for controlled power switching. A double capacitor bank topology with enhanced second capacitor bank voltage is found to be suitable for CS to improve the plasma startup conditions. Simulations are performed in MATLAB Simulink for confirmation of the designed power supply system. The Rogowski coil and current transformers are employed to measure plasma current and the coil’s current waveforms during the experiment in the presence of hydrogen as working gas. An ocean spectrometer and a photron high-speed camera (SA-8) are used for optical measurements and fast plasma imaging. An improvement in startup conditions is observed, enhancing the plasma current duration and light emission intensity recorded in the high-speed camera masked with a Hα filter. [ABSTRACT FROM AUTHOR]

This paper investigates the strategic placement of capacitor banks in the distribution network of Gračanica, with a specific focus on the medium-voltage feeder Grades. The primary objective is to optimize voltage profiles, minimize power losses, and enhance the overall performance of the distribution network. The significance of this research lies in its thorough examination of optimal capacitor placement within the medium-voltage (MV) branch of distribution networks, specifically considering the intricate interplay between capacitor banks and MV branch components, underlining the necessity for informed decisions in the context of distributed generators (DG) integration to enhance overall network performance. The study further investigates the impact of integrating DGs on these objectives on capacitor placement in the MV feeder. Employing the DIgSILENT PowerFactory software tool for modelling the MV feeder and utilizing a genetic algorithm for capacitor placement optimization, the study underscores the robustness of this approach in handling various conditions and seeking optimal solutions. Simulation results demonstrate that strategically placing capacitor banks and integrating DGs can significantly improve the voltage profile and reduce power losses within the distribution system. The findings of this research support 2MVA of concentrated DGs at the middle of the line as the most efficient and most economically beneficial situation on the medium-voltage feeder Grades study case and contribute valuable insights, serving as a reference for future studies on optimal capacitor placement. [ABSTRACT FROM AUTHOR]

This paper develops a novel two-stage coordinated volt-pressure optimization (VPO) for integrated energy systems (IES) networked with energy hubs considering renewable energy sources. The promising power-to-gas (P2G) facilities are used for improving the interdependency of the IES. The proposed VPO contains the traditional volt-VAR optimization functionality to mitigate the voltage deviation while ensuring a satisfying gas quality due to the hydrogen mixture. In addition to the conventional voltage regulating devices, i.e., on-load tap changers and capacitor banks, P2G converter and gas storage are used to address the voltage fluctuation problem caused by renewable penetration. Moreover, an effective two-stage distributionally robust optimization (DRO) based on Wasserstein metric is utilized to capture the renewable uncertainty with tractable robust counterpart reformulations. The Wasserstein-metric based ambiguity set enables to provide additional flexibility hedging against renewable uncertainty. Extensive case studies are conducted in a modified IEEE 33-bus system connected with a 20-node gas system. The proposed VPO provides a voltage-regulated economic operation scheme with gas quality ensured that contributes to high-quality but low-cost multi-energy supply to customers. [ABSTRACT FROM AUTHOR]

Aging of power system assets challenges utilities to maintain reliable service while minimizing their maintenance costs. Although malfunction of devices in the transmission or distribution networks can have catastrophic consequences, their failure is seldom unforeseen. Typically, the device aging occurs gradually over time until its health condition reaches a point of complete breakdown. The overall objective of this paper is to devise a non-invasive, online condition monitoring technique of circuit switchers for shunt capacitor banks. It aims to detect abnormal operation of these devices based on features derived from raw voltage and current waveforms, such that a predictive maintenance strategy may be employed before a complete failure occurs. The data analyzed in this paper are collected at a transmission capacitor bus, where the banks are equipped with pre-insertion impedance. Through a baseline range of values for selected parameters, the proposed technique is able to detect missing pre-insertion impedance during the capacitor energizing and failure of pre-insertion impedance switch out a few cycles after the energizing operation. [ABSTRACT FROM AUTHOR]

Copyright of Przeglad Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to generate high-voltage high-pulsed power, klystron modulators necessarily contain at least one capacitor bank charging structure supplying the energy to be released during the pulse. Conventional charging structures are based on ac/dc front-end units typically based on diode rectifiers combined with power charging structures operated in on/off mode as a second stage, producing prohibitive levels of grid flicker and harmonic contents on the ac grid side while operating at suboptimal power factor. These problems are usually corrected by both costly and spacious external grid compensators. Today, the increased demand on both accelerator peak power and pulselength (translating into higher average power), in conjunction with stricter regulations and standards represent additional challenges also in modulator design. An alternative method for capacitor bank charging, in a steady state allowing for the complete reduction of grid flicker as well as ac line current harmonics and reactive power, was presented by the authors in a preceding publication. This paper presents in further detail the benefits of the proposed power electronic structure and associated control scheme in the context of a review of other solutions suggested for constant power charging and flicker mitigation. This paper also contains a complete description of the proposed control scheme as well as further experimental results, including a thorough assessment of its performance under transient conditions. All experimental results were obtained on a klystron modulator prototype rated for long pulses (3.5 ms), high voltage (115 kV), and high pulsed power (peak power > 2 MW). [ABSTRACT FROM AUTHOR]

This paper describes the characteristics of a plasma-based pressure pulse generator and its potential use as a simulator for studying pellet–cladding mechanical interaction (PCMI) during reactivity-initiated accidents (RIAs). In this device, a transient pressure pulse is generated by rapid heating and expansion of hot, dense plasma inside a nuclear fuel cladding. Thus, the parameters of a pressure pulse, such as peak pressure and pressure rise-rate, can be controlled by modifying the electrical parameters of a pulse discharge circuit. The pulse discharge circuit utilizes a capacitor bank comprising several energy storage capacitors connected in parallel and a high-power solid-state switch. A pressure loading system is attached as a load to the pulse discharge circuit. The power and energy delivered to the load are calculated by measuring the voltage and current waveforms at one end of the loading system. A piezoelectric sensor is connected at the other end of the loading system to simultaneously measure the pressure pulse inside the cladding tube. Preliminary experiments are carried out with a stainless-steel tube to characterize the performance of the device as well as with a pre-hydrided ZIRLO™ cladding tube to demonstrate the potential of the device as a simulator for studying the failure characteristics of the cladding as a result of an RIA. The high pressurization rate of the device is expected to offer unique advantages for studying the PCMI mechanism. [ABSTRACT FROM AUTHOR]

This paper proposes a systematic method using the hybrid automata (HA) model for supervisory management design of power systems to increase stability. The HA model monitors the behavior of the power system and derives a model from which the system's stability is evaluated. In the modeling framework, the hybrid system formalism regulates continuous dynamics and discrete switching behavior. The proposed method extracts a system's control graph, state space, and transfer function, facilitating voltage stability evaluation. A discrete event system (DES) is employed to manage disturbances resulting from load surges, generator outages, capacitor banks, and under-load tap changer (ULTC) transformers. The ULTC transformer and the capacitor bank are utilized to examine the feasibility and effectiveness of the proposed supervisory controller design approach in the presence of distributed generation (DG). Simulation results showed the effectiveness of the HA-based supervisory controller in improving the control and voltage stability, as demonstrated by the generator rotor angle and bus voltage responses, power system eigenvalues, and the stability theorem of linear switching systems. The proposed method provides a promising solution for managing power system stability. [ABSTRACT FROM AUTHOR]

To perform a capacitive current switching test (CCT) at AC extra-high-voltage (EHV) and above level, this paper proposes a new multi-transformer synthetic circuit (MTSC) test method that replaces the general synthetic test method using capacitor banks. An MTSC method has a simpler circuit structure compared to other synthetic testing methods and has higher equivalence (especially recovery voltage and TRV) and validity. Using this method, CCTs for circuit breakers (CBs) of the AC 420 kV voltage class were performed as a field test using the IEC 62271-100 standard. To verify that the test method was valid, test results were analyzed and compared with the requirements of a standard. Consequently, the MTSC method completely covered the requirements of the standard. [ABSTRACT FROM AUTHOR]

The proposed methodology aims at the identification of multiple and multi-stage power quality (PQ) disturbances along with their underlying causes. To this end, a computationally efficient S-Transform with decision tree (DT) based online PQ monitoring algorithm has been presented in this paper. This online algorithm provides a sample-based analysis of 40-dB noisy multiple and multi-stage PQ disturbance signals simulated in MATLAB environment with the different combinations of underlying causes as per the IEEE-1159 standard. The features like residual voltage, instantaneous phase-angle jump (IPAJ), and number of zero crossings (NZC) have been extracted from the transformed contours, viz., maximum voltage amplitude versus time (MVAVT) and phase-angle versus time (PAVT). Henceforth, the accurate recognition of most common underlying causes like three-phase fault, induction motor starting, and capacitor bank energizing has been achieved. For the first time, an online PQ monitoring algorithm is effectively assessing the type and underlying cause of a multiple or multi-stage disturbance simultaneously. The proposed methodology has also been experimentally validated with real-time PQ disturbance signals acquired in the laboratory. [ABSTRACT FROM AUTHOR]

In power systems, capacitor banks play a significant role in improving voltage profiles, reducing losses, and adjusting power factors. Security measures must be implemented quickly and reliably to protect them from a wide range of threats. As a consequence of capacitor bank failures, finding and fixing the damaged units/elements is more difficult, which may lead to voltage control difficulties or the loss of any of these benefits. The paper shows the application of system-based testing methods for protection systems using RelaySimTest software, which works with OMICRON injection test sets. System-based testing methods are applied to test voltage differential protection for center-tapped shunt capacitor banks. The use of system-based testing methods has many advantages over conventional testing methods, which include distributed testing, transient state conditions testing, etc., which in turn result in cost savings during the commissioning and testing phase. The impact of external faults on bank installation has been tested successfully. [ABSTRACT FROM AUTHOR]

Optimal reactive power dispatch plays a key role in the safe operation of electric power systems. It consists of the optimal management of the reactive power sources within the system, usually with the aim of reducing system power losses. This paper presents both a new model and a solution approach for the multi-period version of the optimal reactive power dispatch. The main feature of a multi-period approach lies on the incorporation of inter-temporal constraints that allow the number of switching operations in transformer taps and capacitor banks to be limited in order to preserve their lifetime and avoid maintenance cost overruns. The main contribution of the paper is the constraint handling approach which consists of a multiplication of sub-functions which act as penalization and allow simultaneous consideration of both the feasibility and optimality of a given candidate solution. The multi-period optimal reactive power dispatch is an inherently nonconvex and nonlinear problem; therefore, it was solved using the metaheuristic mean-variance mapping optimization algorithm. The IEEE 30-bus and IEEE 57-bus test systems were used to validate the model and solution approach. The results allow concluding that the proposed model guarantees an adequate reactive power management that meets the objective of minimizing power losses and keeping the transformer taps and capacitor bank movements within limits that allow guaranteeing their useful life. [ABSTRACT FROM AUTHOR]

This paper presents a new fault location algorithm for radial distribution networks employing synchronized distributed voltage traveling wave (TW) observers. A robust and accurate fault location algorithm significantly improves the distribution networks reliability and reduces the risk of bush fires and electrocution resulting from sustained undetected faults. The medium voltage distribution networks include numerous junctions and many shunt and series connected devices, such as capacitor banks, transformers and cables, which makes fault location far more complicated. This paper investigates the effect of power system components on the propagation of traveling waves and proposes a method for a fault location in heavily branched radial distribution feeders. Results show that parasitic shunt capacitances in transformers have a significant impact on traveling time of incident waves to the location of the TW observers and compensation for this effect will improve the accuracy of fault location. [ABSTRACT FROM AUTHOR]

Memristors have been recently proposed as an alternative to incorporate switching along with traditional CMOS circuits. Adaptive impedance and frequency tuning are an essential and challenging aspect in communication system design. To enable both, a matching network based on switchable capacitors with fixed inductors is proposed in this paper where the switching is done by memristive switches. This paper analyzes the operation of memristors as a switch and a matching network based on memristors which adaptively tunes with impedance and frequency. With three capacitor banks of each 0.5 pF resolution and two fixed inductors, matching for antenna impedance ranging from 20 to 200 Ohms and for frequencies ranging from 0.9 to 3.2 GHz is reported. Thereafter, an adaptive planar band-pass filter is implemented on CMOS technology with two metal layers. This adaptive frequency tunable band-pass filter uses a π network with resonator tanks in both arms that operates at 2.45 GHz. It is tunable from 2.8 GHz to 7.625 GHz range. This tunability is achieved using tunable spiral inductor based on memristive switches. The proposed filter layout is implemented and simulated in ANSYS Designer. The initialization and the programming circuitry to enable adaptive switching of the memristive devices has to be addressed. Since RF memristive devices are not commercially available, circuit level simulations are done as a proof of concept to validate the expected results. [ABSTRACT FROM AUTHOR]

The grasshopper heuristic optimisation algorithm (GOA) is one of the newest heuristic techniques. It attempts to imitate locust's behaviour in solving different problems. In this paper, first, optimal location and size of fixed capacitor banks on distribution systems have been obtained using the GOA. Determination of the optimal number of capacitor banks and their optimal locations and sizes represent one of the major challenges facing distribution system operators. Therefore, second, a combined power loss sensitivity and GOA technique has been introduced to obtain the optimal number, location and size of the capacitor banks on distribution systems. Third, a proposed technique for optimal placement of fixed and switched capacitor banks considering daily load variations is introduced. Finally, a new technique of combined rough set theory and GOA is proposed to minimise daily switching of the capacitor banks and minimise daily power losses. Four test systems with different sizes and complexities are considered to evaluate the proposed techniques which are the 33, 69, 85 and 141-bus systems. To clarify the validation and effectiveness of the proposed solution techniques, the obtained results have been compared with other previously used solving techniques. The obtained results demonstrate the accuracy and effectiveness of the introduced techniques. [ABSTRACT FROM AUTHOR]

Summary: In this paper, for standalone and grid‐connected PV systems, a three‐phase simplified split‐source inverter (SSI) is proposed and controlled using a model‐predictive control (MPC). The maximum power point tracking (MPPT) approach used is an incremental conductance method based on a PI controller for both systems. The standalone system is composed of PV modules, a three‐phase SSI, and a bidirectional power DC–DC converter that connects a battery bank and a DC‐side capacitor. The output AC voltages of SSI are controlled using MPC. The bidirectional power DC–DC converter regulates the DC‐link voltage (DCLV). The grid‐connected system consists of PV modules, a three‐phase SSI, and an AC‐side L‐filter. The DC‐link PI controller generates reference currents for the MPC algorithm. The MPC uses these reference currents to adjust and deliver the PV power to the grid while regulating the DCLV. The PI controllers' parameters are selected for both systems using the Harris Hawks optimization method. Both PV systems simulation results show that under various operating conditions, they have succeeded in fixing a DCLV and producing a high‐quality AC output voltage and current at low THD. Experimental results for the three‐phase standalone PV system used to verify the system's performance. [ABSTRACT FROM AUTHOR]

The conventional topological approach to eliminate the multiple-input DC voltage requirement in multilevel inverter configurations for synthesizing high-output voltage levels is to deploy split capacitor banks at the input terminal. This method stipulates a less expensive, light weight, and reduced size inverter system. However, the excessive demand for several capacitor banks and the complex voltage balancing strategy associated with this conceptual approach poses numerous limitations in their deployment. In view of these drawbacks, this study proposes a self-balanced, single-phase, nine-level switched-capacitor-based inverter topology consisting of a single-input DC voltage, an auxiliary circuit, and an H-bridge circuit unit. A commensurate single carrier-based sinusoidal pulse-width modulation scheme is developed for the proposed power circuit control, enabling the synthesis of a nine-level output voltage waveform whose amplitude is four times the input voltage value. Detailed power circuit operations and switching functions are adequately provided in the proposed topology. A comparison between the proposed inverter and its recent counterparts in terms of component count, cost involvement, and output voltage-boosting ability is duly carried out using Python data visualization. Results reveal that the proposed inverter competes well in these three criteria. For varying R–L load values, the inverter has the capability of high active and reactive power delivery. Its dynamic response for step changes in the modulation index under these power-mode operations is presented in this paper. For high active power-mode operation, efficiencies of 98.27% and 98.92% under light- and heavy-load conditions, respectively, are obtained on a 3-kW-rated inverter prototype. [ABSTRACT FROM AUTHOR]

With the accelerating penetration of photovoltaics (PVs) and electric vehicles (EVs), distribution networks face the risks of voltage violations and fluctuations. On the one hand, conventional voltage regulation resources like OLTC transformers and capacitor banks feature slow response and limited lifetime duration, making them incapable of quickly responding to the temporary voltage issues created by PVs and EVs. On the other hand, EVs and PVs interact with the power grid via fully controllable power electronic converters capable of real-time adjusting their operating settings, making them ideal voltage support resources. To exploit the voltage support capability of PVs and EVs, this paper proposes a two-stage control scheme for the voltage regulation of distribution networks, consisting of the day-ahead and intraday control stages. The day-ahead control mitigates potential voltage violations via day-ahead scheduling of the operation settings for OLTC transformers and capacitor banks. The intraday control further alleviates voltage deviations and voltage fluctuations based on the reactive power support of PV systems and the rational EV charging/discharging scheduling. A rolling optimization-based control technique is proposed in the intraday control stage to achieve real-time control of EVs and PVs with the stochastic nature of EV charging behaviors inherently considered. The proposed two-stage voltage regulation scheme is validated via case studies performed on the IEEE 123-node test feeder integrated with PVs and EVs. [ABSTRACT FROM AUTHOR]

This paper presents a novel strategy for online parameter estimation in a hybrid active power filter (HAPF). This HAPF makes use of existing capacitor banks which it combines with an active power filter (APF) in order to dynamically compensate reactive power. The equipment is controlled with finite control set model predictive control (FCS-MPC) due to its already well-known fast dynamic response. The HAPF model is similar to a grid-connected LCL-filtered converter, so the direct control of the HAPF current can cause resonances and instabilities. To solve this, indirect control, using the capacitor voltage and the inverter-side current, is applied in the cost function, which creates high dependency between the system parameters and the equipment capability to compensate the load reactive power. This dependency is evaluated by simulations, in which the capacitor bank reactance is shown to be the most sensitive parameter, and, thus, responsible for inaccuracies in the FCS-MPC references. In order to minimize this problem without increasing the complexity of the FCS-MPC algorithm, an estimation technique, based on adaptive notch filters, is proposed. The proposed algorithm is tested in a laboratory prototype to demonstrate its ability to follow variations in the HAPF capacitor reactance, effectively correcting the reactive power reference and providing dynamic reactive power compensation. During the tests, the proposed algorithm was capable of keeping the supplied reactive power within a 1 % error, even in a situation with 33 % variation in the HAPF capacitor reactance. [ABSTRACT FROM AUTHOR]

The problem regarding the optimal integration of efficient reactive power compensation in radial and meshed distribution networks using fixed-step capacitor banks and distribution static compensators (D-STATCOMs) is addressed in this research paper by proposing a master–slave optimization methodology. Radial and meshed distribution topologies are considered for the grid structure while including variable active and reactive demand curves. An economic analysis is performed, considering the net present value of the optimization plan, as well as the costs of energy losses and the capacitor banks' acquisition, installation, and operation. In the case of the D-STATCOMs, an annualized costs analysis is presented. In the master stage, the discrete version of the generalized normal distribution optimization (GNDO) algorithm selects the nodes and the sizes of the capacitor banks. In the slave stage, the successive approximations power flow approach is implemented. Numerical results in the IEEE 33-bus grid (with both radial and meshed topologies) and the IEEE 85-bus grid (with a radial configuration) demonstrated the proposed master–slave optimization's effectiveness in minimizing the project's expected net present value for a planning period of five years. Moreover, a simulation in the IEEE 69-bus grid under peak operation conditions showed that the GNDO approach is an excellent optimization technique to solve the studied problem when compared to combinatorial and exact optimization methods. In addition, numerical validations considering D-STATCOMs in the IEEE 85-bus grid confirmed the effectiveness and robustness of the GNDO approach in addressing problems associated with optimal reactive power compensation in medium-voltage distribution systems. [ABSTRACT FROM AUTHOR]