Voltage Limits Research Articles

АНАЛІЗ ЕЛЕКТРОМАГНІТНИХ ПРОЦЕСІВ В КОЛІ «ОБМЕЖУВАЧ НАПРУГИ – ФІЛЬТР НИЖНІХ ЧАСТОТ» ЗА ДІЇ ВИСОКОВОЛЬТНОЇ ІМПУЛЬСНОЇ ЗАВАДИ З МЕРЕЖІ ЕЛЕКТРОЖИВЛЕННЯ

In the work, a theoretical analysis of high-voltage surge (HVS) passing from a power supply network through the path "voltage limiter - low-pass filter" is carried out, with the aim to evaluate the effectiveness of the filter on reducing the amplitude of the residual HVS at the input of electrical and/or radio-electronic equipment. As a low-pass filter (LPF), an L-shaped filter was chosen. Typical means of limiting the amplitude of the HVS (gas-filled arresters, varistors, and suppressors) are analyzed, and their shortcomings are shown. The justification of the equivalent scheme for theoretical analysis is given. The analysis revealed a direct relationship between the cut-off frequency of the LPF, which is deter-mined by the nominal values of its elements, and the amplitude of the residual HVS at the mains input of the equipment, and also showed the effectiveness of inserting the LPF between the output of a typical HVS voltage limiter and the mains input of the mentioned equipment from the point of view of additional reduction of the residual HVS amplitude. References 18, figures 6.

Golden Jackal Algorithm for Optimal Size and Location of Distributed Generation in Unbalanced Distribution Networks

The Golden Jackal Optimization algorithm (GJO) is used in this study to address the problem of optimal placement and sizing of single and multiple distributed generators (DGs) on the IEEE123 test system. The proposed approach attempts to minimize the total power loss of the system while respecting the voltage and power limits. The GJO algorithm is a new meta-heuristic algorithm inspired by the behavior of the golden jackal in the wild. The GJO algorithm is used to find the ideal location and sizing of DGs, and the results are compared with those obtained by other meta-heuristic techniques. According to the simulation results, the GJO method outperforms other metaheuristic algorithms in terms of problem-solving, while satisfying all constraints of the system. The proposed approach also demonstrates the effectiveness of the GJO algorithm in the solution of complex optimization problems in power systems

Performance Stabilization of Lithium-Sulfur Batteries Containing Sulfolane-based Electrolyte and Microporous Cathode by Controlling Working Voltage Range

For lithium-sulfur (Li-S) batteries, high-concentration electrolyte that inhibits the dissolution of Li polysulfide has been widely studied; one such electrolyte contains sulfolane. This study investigates the conditions under which a microporous activated carbon cathode, derived from azurmic acid, operates stably in a sulfolane-based electrolyte. We expected this cathode to maintain a stable capacity in a sulfolane-based electrolyte because its micropores stabilize the S species. However, Li-S batteries containing this cathode and electrolyte exhibit significant capacity decay during cycling. The cutoff voltage during charge-discharge cycling is varied to suppress the capacity decay. At a discharge voltage of 1.4 V or lower, the cycle life of the Li-S batteries is significantly reduced. Conversely, increasing the cutoff voltage during discharge suppresses the capacity decay of Li-S batteries. On the other hand, increasing the upper voltage limit during charging increases the reversible capacity. Thus, the operating voltage range is optimized. This study indicates that the voltage range of Li-S batteries should be carefully determined depending on the type of cathode material and electrolyte.

Achieving the high-energy-density asymmetric supercapacitor by hierarchical molybdenum-vanadium-sulphide@covalt sulphide core–shell nanoporous hybrid as cathode and iron oxide@carbon-nanofibers/nitrogen-doped reduced graphene oxide aerogel as anode

In recent decades, supercapacitors have attracted much research as low-cost, reliable, and environment-friendly energy storage devices. However, the low energy density and low operating voltage limit its wide applications. Herein, a novel 1D–2D constructed 3D multicomponent Mox:Vy–S@Co9S8 core–shell nanowires array is designed and fabricated as the cathode material through a simple and economical two-step hydrothermal reaction and electrodeposition process. The constructed 3D Mo0.5V0.5–S@Co9S8 electrode exhibits excellent charge storage capability; an area capacity of 0.91 mA h cm−2 with a corresponding specific capacity of 480.9 mA h g−1 at 2 mA cm−2. Moreover, a solid-state ASC (SS–ASC) is assembled with the as-obtained Fe2O3@CNFs/N–rGO aerogel as the anode, the constructed 3D Mox:Vy–S@Co9S8 NWAs as cathode, and KOH–PVA–gel as a gel electrolyte. As proof of concept, the assembled SS–ASC display an excellent operating voltage window of ~1.7 V and an outstanding energy density of ~108.47 W h kg−1 at ~520.65 W kg−1 power density. Also, when connected in series, the two SS–ASC devices can run an electronic clock for 30 min, demonstrating the practicability of the constructed 3D Mox:Vy–S@Co9S8 NWAs as a promising electrode material for the development of the high energy density ASC.

A coordinated control scheme for VSC-MTDC system with multiple renewable energy sites based on voltage margin and adaptive drooping control

This paper designs a novel coordinated control scheme to improve the control performance of voltage source converters (VSC) based multi-terminal high voltage direct current (MTDC) transmission network by merging the benefits of adaptive drooping and voltage margin controllers. In this proposed scheme, the droop coefficient is used to manage the DC voltage and maintain power sharing by shifting the control modes of the rectifiers and inverters in the presence of considerable power disturbances. The droop coefficient is planned based on the stability limit of DC voltage. The performance of the designed control scheme is compared to that of existing coordinated control and voltage margin droop control approaches. A ±400 kV five-terminal VSC-MTDC network is developed in PSCAD to verify the planned control method. The simulation results indicate that the proposed control scheme can achieve good performance for controlling the DC voltage and maintaining active power in the MTDC system.

Sodium Nitrate/Formamide Deep Eutectic Solvent as Flame‐Retardant and Anticorrosive Electrolyte Enabling 2.6 V Safe Supercapacitors with Long Cyclic Stability

Safe operation of electrochemical capacitors (supercapacitors) is hindered by the flammability of commercial organic electrolytes. Non‐flammable Water‐in‐Salt (WIS) electrolytes are promising alternatives; however, they are plagued by the limited operation voltage window (typically ≤2.3 V) and inherent corrosion of current collectors. Herein, a novel deep eutectic solvent (DES)‐based electrolyte which uses formamide (FMD) as hydrogen‐bond donor and sodium nitrate (NaNO3) as hydrogen‐bond acceptor is demonstrated. The electrolyte exhibits the wide electrochemical stability window (3.14 V), high electrical conductivity (14.01 mS cm−1), good flame‐retardance, anticorrosive property, and ultralow cost (7% of the commercial electrolyte and 2% of WIS). Raman spectroscopy and Density Functional Theory calculations reveal that the hydrogen bonds between the FMD molecules and ions are primarily responsible for the superior stability and conductivity. The developed NaNO3/FMD‐based coin cell supercapacitor is among the best‐performing state‐of‐art DES and WIS devices, evidenced by the high voltage window (2.6 V), outstanding energy and power densities (22.77 Wh kg−1 at 630 W kg−1 and 17.37 kW kg−1 at 12.55 Wh kg−1), ultralong cyclic stability (86% after 30 000 cycles), and negligible current collector corrosion. The NaNO3/FMD industry adoption potential is demonstrated by fabricating 100 F pouch cell supercapacitors using commercial aluminum current collectors.

A streamlined and enhanced iterative method for analysing power system available transfer capability and security

Available Transfer Capability (ATC) is a crucial indicator for ensuring the reliable and efficient electric grid as it helps to manage congestion and ensure that the power flows are kept within safe operating limits. This article presents a novel approach named as modified repeated alternating current power flow (MRACPF) with step-size control mechanism and compares it with the existing techniques like direct current power transfer distribution factors (DCPTDF) and repeated alternating current power flow (RACPF) for analyzing the ATC of the power system during bilateral wheeling transactions in MATLAB environment. The study further assesses the ATC in different multilateral wheeling transactions of two standard test systems (IEEE 30-bus and IEEE 118-bus) and evaluates inter-area ATCs for the IEEE 118-bus system under various operational scenarios. The Composite Security Index (CSI) which is based on both line flow limit and bus voltage limit violations is used to identify and rank the most severe (k-1) line contingencies, and is able to differentiate between secure and insecure state of the power system and furthermore, MRACPF with step-size control mechanism is used to assess ATC during the severe (k-1) line outage and generator outage scenarios for various power transactions. The MRACPF method produces comparable results to the RACPF method for obtaining the Available Transfer Capability (ATC), but it takes less time. This time savings can be significant, especially for larger power systems, where the execution time can be reduced by more than 50%.

Metal–Organic Framework‐Derived MnO Nanocrystals Embedded in a Spindle Carbon for Rechargeable Aqueous Zinc Battery with a Molten Hydrate Electrolyte

Rechargeable aqueous zinc batteries (RAZBs) are emerging candidates for large‐scale energy storage. However, the lack of high‐capacity cathodes because of the electrostatic interactions between Zn2+ and cathode and the inferior electronic conductivity restricts their performance. The operating voltage limitation imposed by water is another barrier for RAZBs. Herein, manganese oxide (MnO) nanocrystals embedded in a spindle carbon matrix (MnO@C) synthesized from a metal–organic framework are used as a cathode. The uniform distribution of fine‐sized MnO (≈100 nm) in the carbonized matrix (≈5 μm) and the intimate connection between them not only increase the utilization of electroactive material but also eliminate the use of conductive additive. By utilizing the molten hydrate electrolyte, ZnCl2·2.33H2O, a discharge voltage plateau approaching 1.60 V and a high reversible capacity of 106 mAh g−1 after 200 cycles are achieved. This research proposes an approach for affordable RAZBs to fulfill large‐scale energy storage.

A non‐isolated step‐up common‐ground cost‐effective microinverter for AC‐module application

AbstractThis research proposes a cost‐efficient microinverter. The proposed microinverter can eliminate the leakage current using common‐ground configuration. It uses three switches and only one of them operates at high frequency. In addition, a passive lossless snubber is applied to limit voltage stress and provide soft‐switching performance for the high‐frequency switch. A pair of coupled inductors is used to provide higher voltage gain which makes it possible to keep the operating duty cycle in the normal range and makes the proposed inverter suitable for AC module application. The input current of the proposed microinverter is continuous which reduces the loss of the input capacitor by high‐frequency current component reduction. The operating principle of the proposed inverter is described in both positive and negative current modes. In positive current mode, the proposed microinverter works similar to SEPIC converter and in negative current mode its performance is similar to CUK converter. The dynamic behavior of the proposed microinverter is analyzed through simulation and a simple PI controller is designed to accommodate the worst case. Theoretical loss analysis is applied and finally the results of this research are compared with other researches. The performance of the proposed inverter is justified by simulation and practical results of a 300‐watts prototype.

A novel hybrid algorithm based optimal planning of solar PV and battery energy storage systems

The adoption of renewable energy sources (RES) such as solar photovoltaic distributed generation (SPVDG) has been at its peak in the present decade owing to their positive impact on the environment and the grid. However, these sources’ ratings and placement need to be optimally estimated before their accommodation in the power distribution system (PDS) to prevent increased power loss and voltage profile aberrations. In this article, SPVDG is integrated with battery energy storage systems (BESS) to compensate for the shortcomings of SPVDG, such as intermittency and uncertainty, and to reduce peak demand. This paper presented a novel hybrid algorithm, which is a combination of the enhanced elephant herding algorithm and the Jaya algorithm. This developed algorithm properly controls the searching algorithm from global exploration to local exploitation to obtain the near-global optimum solution. The problem formulation is centered on the optimal accommodation of SPVDG and BESS to alleviate the power loss and improve the voltage profile of the PDS. Further, the voltage limits, maximum current limits, and BESS charge–discharge constraints are validated throughout the optimization process. Moreover, the hourly variation of SPVDG generation and demand profile with seasonal impact is examined in this study. IEEE 69 bus PDS is tested for the development of the presented work. The suggested algorithm demonstrated its effectiveness and accuracy when compared to different optimization approaches in the literature.

Method of static stability dominant identification

AbstractTwo extreme cases of static stability are voltage stability and power angle stability. The general stability analysis only focuses on one of the voltage stability or power angle stability. The stability limit and state change are studied for a certain kind of stability characteristics. In this paper, the stability limits of static voltage and power angle are derived, respectively. Therefore, different stability characteristics and their interrelationships can be further studied. The index to judge the dominant stability characteristic is defined. The proposed index only needs the system wide‐area measurement information to quickly and accurately judge the dominant static stability characteristics. The dominant instability (DI) characteristic index proposed in this paper is equal to 1 or −1, which can help to quickly identify whether the power angle stability or voltage stability is dominant. The effectiveness of the method is proved by a simple system.

Optimization for position and rating of distributed generating units using bacteria foraging algorithm to reduce power losses

Distributed generation (DG) units, which include solar panels, wind turbines, and fuel cells, are gaining in popularity as a result of the fact that they are dependable and produce no harmful emissions when they generate electricity. However, the integration of these new power sources into the current power grid may result in several technical difficulties, including voltage fluctuations, power imbalances, and increased power losses. The use of optimization methods may assist to solve these difficulties by determining the best position and size of DG units. This will help to reduce the amount of power that is lost and will enhance the power system's overall performance. Therefore, the Bacteria Foraging Optimization (BFO) method was used for DG in this study. This approach helps to decrease phase jump during symmetrical and unsymmetrical faults, as well as power losses, controls voltage magnitude and angle, and regulates voltage magnitude. In addition, nonlinear restrictions that are regarded to be forward factors include voltage limitation, DG capacity limitation, and phase jump limitation. On the IEEE 69 bus radial distribution scheme, both single and double DGs are taken into consideration for the allocation process. Because of its worldwide convergence and decreased calculation liability, the BFO algorithm is used in the optimization process for both position and rating. The suggested procedure is tested on the IEEE 69 bus radial distribution system in a MATLAB environment; the results demonstrate the efficiency of the suggested approach. In this case, the proposed system was successful in achieving the triple line-to-ground fault-based phase jump of 26.3° without DG and 0.52° with DG; the line-to-line (AB) fault-based phase jump of 0.01° without DG and 0.001° with DG; the single line (A) to ground fault-based phase jump of 0.0027° without DG and 0.001° with DG; and the line to ground fault-based phase jump of 0.001° with DG.

A Variable-Mode Bidirectional Isolated Power Converter for Wide Voltage-Transfer Ratio Applications

Lithium battery charging require a wide voltage gain range. Due to the limited voltage gain range of LLC converter, it is limited in battery storage application scenarios. In this paper, A interleaved parallel LLC converter is proposed to realize the charging and discharging processes of bidirectional battery energy storage systems. The converter extended range of voltage gain required for battery recovery area by mode switching control. For the interleaved parallel mode power equalization problem, a gain compensation control strategy is proposed to solve the power equalization problem of the converter in this mode. This results in more uniform thermal and current stresses on the charger, as well as smaller input and output ripple. Moreover, with the proposed variable-mode control strategy, the efficiency of the charging process remains above 90%. A 1.5-kW experimental platform was developed to validate the performance of the proposed converter.

Direct Instantaneous Torque Control of SRM Based on a Novel Multilevel Converter for Low Torque Ripple

The torque ripple of a switched reluctance motor (SRM) limits its application in electric vehicles. This paper proposes a DITC system for SRMs based on a novel multilevel converter (MLC), which aims at the problem that the torque ripple cannot be effectively suppressed for the conventional direct instantaneous torque control (DITC) of an SRM due to the limitation of the DC bus voltage in the asymmetric half-bridge converter (AHBC) and the single control strategy formulated in the commutation region. Based on the advantages of fast excitation and fast demagnetization for the proposed MLC and the torque distribution characteristics for each phase winding in the commutation region, a novel torque hysteresis control strategy is developed to improve the torque-following ability of the DITC and achieve the purpose of minimizing the torque ripple in the commutation region. In addition, multiobjective optimization control of the motor is carried out to improve the efficiency of the DITC system while suppressing the torque ripple. The effectiveness of the proposed SRM drive scheme is verified by experiment, which is of great significance for the application of SRMs in electric vehicles.

Determination of maximum additional load for EV charging station considering practical security limits

Nowadays, the allocation of electric vehicle charging stations (EVCS) for the charging of electric vehicles (EVs) is essential, as random allocation may cause significant energy loss for the radial distribution system (RDS). Uncoordinated charging of EVs dominates the load profile of the RDS. Although a single EV has a negligible impact on the system, the combined effect of charging an EV cluster may violate the voltage security constraints of the RDS. Therefore, to avoid such circumstances, the loadability limit of each node of the RDS must be determined. Previously, conventional analytical methods were used to calculate the maximum loadability of the RDS node, where voltage magnitudes become less than the critical voltage limit. However, these approaches are not acceptable for the power industry, as it may push the system towards a blackout. Therefore, the appropriate capacity of the EVCS can only be determined if the voltage security limit of each node of the RDS follows its critical limit. Hence, in this paper, a modified forward-backward sweep (MFBS) algorithm is formulated to find the maximum additional load (MAL) of each node of the RDS considering non-unity power factor during the EV charging process. This algorithm may help the EVCS to determine its capacity or optimal number of charging ports directly during installation at an optimal location of RDS. For validation, the 33-bus and 69-bus RDSs have been used, and it can be seen that the EVCSs have been successfully installed in the optimal location of the test systems mentioned above without violating the voltage security limit of each node of the RDS.

An energy management system model with power quality constraints for unbalanced multi-microgrids interacting in a local energy market

As multi-microgrids become readily available, some limited models have been proposed that study operational and power quality constraints with local energy markets independently. This paper proposes a convex optimization model of an energy management system with operational and power quality constraints and interactions in a Local Energy Market (LEM) for unbalanced microgrids (MGs). The LEM consists of a pre-dispatch step and an energy transactions step (ETS). The ETS combines the MGs’ objectives while considering two strategies: minimize the cost of buyers or maximize the revenue of sellers. Our proposed model considers harmonic distortion and voltage limit power quality constraints in both steps. Moreover, we model operational constraints such as power flow, power balance, and distributed energy resources behaviors and capacities. We numerically evaluate the proposed model using three unbalanced MGs with residential, industrial, and commercial load profiles, where each microgrid manages its resources locally. Furthermore, we create two groups of cases to analyze the interactions in the local energy market. In the first group, the price of the DSO energy and the surplus from MGs to DSO are the same. The numerical results show that using the increasing revenue strategy promotes MGs to interact more while encouraging them to have high energy prices. When the reducing cost strategy is used, fewer energy interactions occur, and the price of MGs energy is encouraged to be lower.

Probabilistic approach to investigate the impact of distributed generation on voltage deviation in distribution system

The increasing penetration of renewable-based generation in the distribution network adds randomness to the bus voltage due to its stochastic characteristics. Consequently, the distribution network faces voltage limit violations at multiple buses. In this scenario, the traditional voltage control method fails to maintain the voltage profile of the network due to its slow response time. A fast and dynamic voltage control technique can be achieved by utilizing the voltage-controlling capability of available DGs in the network with the information about the impact of DG-integrated bus on change in voltage at any bus in the network. Evaluating this information using the traditional probabilistic load flow method is computationally inefficient for real-time applications. Therefore, in this paper, a principal component analysis (PCA)-based novel probabilistic voltage sensitivity index (PVSI) is proposed. It ranks the DG-integrated buses by evaluating the impact of power perturbation at DG-integrated buses on changes in voltage at any bus in the network. The PVSI is analytically derived to reduce the computation time for ranking. Further, the proposed PVSI is validated on the 69-bus and the 141-bus distribution systems by comparing it with the traditional Monte Carlo simulation (MCS) and joint differential entropy (JDE) in terms of accuracy and computation time. From the simulation, it is observed that PVSI gives a similar ranking as both methods in less computation time. Due to the advantage in computation time, the proposed method enables the distribution system operator (DSO) to use this information for fast and dynamic voltage control in a real-time scenario.

Quantifying the benefits of shared battery in a DSO-energy community cooperation

Local energy communities are forming as a way for prosumers and consumers to invest in distributed renewable energy sources, community storage and share electricity. Meanwhile, several distribution grids have voltage problems at certain hours of the year. Local energy communities consisting of generation and storage units might be valuable flexible assets that the distribution system operator (DSO) can make use of. This article aims to study how a battery in an energy community can provide services to the distribution grid, by creating a linear optimisation model which includes power flow constraints and a battery degradation model. First, we investigate how the battery operation of an energy community impacts the voltage in the nearby buses. We find that when including the degradation model, the voltage limits are violated much less than when not including the degradation model. Next, we investigate how the battery operation differs when the energy community cooperates with an active DSO to share the battery use, and quantify how much the DSO should remunerate the energy community. We find that the energy community should get 15 € per year due to an increase in electricity and degradation costs, which equals an increase of 0.12%, compared to when the community is not providing a service. Finally, a sensitivity analysis is performed to determine which parameters are more important to consider. We find that voltage violations in the grid are sensitive to the battery replacement cost, electric vehicle charging peak and the average spot price, while the remuneration from the DSO is sensitive to the battery replacement cost. For small battery sizes and a low power-to-energy ratio, the community is not able to improve the voltage at all hours of the year.

Competition between the Ni and Fe Redox in the O3-NaNi1/3Fe1/3Mn1/3O2 Cathode Material for Na-Ion Batteries

Sodium-ion batteries are attracting great attention due to their low cost and abundance of sodium. The O3-type NaNi1/3Fe1/3Mn1/3O2 layered oxide material is a promising candidate for positive electrodes (cathodes) in Na-ion batteries. However, its stable electrochemical performance is restricted by the upper voltage limit of 4.0 V (vs Na/Na+), which allows for reversibly removing 0.5–0.55 Na+ per formula unit, corresponding to the capacity of 120–130 mAh·g–1. Further reduction of sodium content inevitably accelerates capacity degradation, and this issue calls for a detailed study of the redox reactions that accompany the electrochemical (de)intercalation of a large amount of sodium. Here, we present operando and ex situ studies using powder X-ray diffraction and X-ray absorption spectroscopy combined with 57Fe Mössbauer spectroscopy. Our approach reveals the sequence of the redox transitions that occur during the charge and discharge of O3-NaNi1/3Fe1/3Mn1/3O2. Our data show that in addition to nickel and iron cations oxidizing to M+4, a part of iron transforms into the “3 + δ” state owing to the fast electron exchange Fe3+ + Fe4+ ↔ Fe4+ + Fe3+. This process freezes upon cooling the material to 35 K, producing Fe4+ cations, some of which occupy tetrahedral positions.

Power Feedback Control Unit for Closed-Loop Wirelessly Powered Biomedical Implants

Effective power management is crucial in designing wirelessly powered implants that have a long operational lifetime. It ensures that the received power is optimized for efficient operation and prevents damage caused by excessive or insufficient powering. This paper presents a power feedback control unit for wirelessly powered implanted biomedical devices, which includes an implanted voltage level detector and limiter. The feedback control bits can be transmitted through the link to the external unit as uplink data communication, or used to autonomously prevent overvoltage in worst-case scenarios. This design is implemented and fabricated in a 180nm CMOS process, which can be used for the power conversion chain of wirelessly powered biomedical implanted devices. The system consumes 144 μW at a supply voltage of 1.8V and a chip area of 0.02255mm2.