Voltage Variations Research Articles

Maximizing energy transfer of solar-battery charge controller using voltage balancing strategy

Off-grid and grid-connected photovoltaic (PV) systems with battery storage rely heavily on efficient energy transfer to maximize PV power utilization and battery lifespan. However, existing literature often overlooks the crucial role of energy transfer efficiency in these systems. This paper proposes a novel, fundamental-based PV power flow strategy that addresses this gap by employing a concept of source-load voltage matching. The proposed strategy ensures optimal voltage matching between the PV array and the battery bank. This is achieved by configuring the battery bank voltage range (between nominal and fully charged states) to closely align with the variation in PV voltage at its Maximum Power Point (MPP) across different operating temperatures. This systematic approach requires specifying the DC load voltage, configuring the battery bank, and selecting PV modules with compatible Vmp (voltage at maximum power) parameters. The system utilizes a high-current blocking diode and current limiter for safe connection between the PV array and battery bank. Additionally, the strategy protects against battery overcharge by controlling parallel fans used for PV panel cooling. Experimental results with a 1.62 kW PV system employing lead-acid batteries demonstrate improved efficiency compared to traditional methods. This innovative approach has the potential to significantly enhance energy transfer efficiency, contributing to improved energy sustainability in PV systems.

Grid-Forming Control for Solar Generation System with Battery Energy Storage

Solar generation systems with battery energy storage have become a research hotspot in recent years. This paper proposes a grid-forming control for such a system. The inverter control consists of the inner dq-axis current control, the dq-axis voltage control, the phase-locked loop (PLL) based frequency control, and the DC voltage control. The proposed control embeds the PLL into the grid-forming inverter control, offering the advantages of better synchronization and fault current-limiting capability. With the proposed control, the battery energy storage is able to provide inertial and primary frequency support during the grid frequency disturbance. Simulation models are established in PSCAD/EMTDC, and the results during the active power variation and AC voltage variation, the grid frequency disturbance, grid fault, and mode switch validate the effectiveness of the proposed control.

Laboratory-Based Investigation of Contactors Susceptibility to Short Duration Voltage Sags

Voltage sags pose substantial challenges in electrical systems, disrupting power supply and adversely impacting equipment. This paper outlines the issues arising from voltage sags, emphasizing their detrimental effects on electrical installations powered by relays and contactors. The study delves into the susceptibility of these critical components when faced with voltage fluctuations, exploring how sags influence their functionality. Additionally, the research presents experimental results from laboratory tests, focusing on contactors of different power exposed to voltage sags lasting less than one cycle. These assessments provide insights into the performance of contactors under short-duration voltage variations, offering valuable contributions to enhancing the reliability of electrical systems.

A quadrilateral non-classical microplate element considering the voltage effect

A quadrilateral non-classical Mindlin element that incorporates voltage effects was introduced for examining the bending and free vibration of piezoelectric multilayer plates. The model was developed to examine multilayer plates in the presence of voltage effects. Hamilton’s principle was initially employed to formulate the equation of motion for a multilayer Mindlin plate, considering both size and voltage effects. The equations of motion were resolved through the Galerkin’s method. The suggested element is a rectangular element featuring four-nodes, each possessing 15 degrees of freedom, accounting for both bending and stretching deformations. This element meets the requirements for C0 continuity and C1 weak continuity, and incorporates size and voltage effects. The results were examined with both experimental and analytical data. Upon investigating the voltage effect, it was found that the stiffness matrix depends on both the magnitude and sign of the voltage. Furthermore, it has been demonstrated that the natural frequencies of higher modes are less affected by voltage variations compared to lower modes. In the end, the model was compared to experimental results obtained from a multilayer microcantilever.

Power quality and efficiency functionalities for a three-level Dynamic Voltage Restorer on low voltage grids

Back-to-back PWM inverter based bidirectional dynamic voltage restorers (DVR) may have worse efficiency than mechanical or SCR based solutions, but they are able to provide a continuously variable voltage in series with the grid. As the injected waveform does not need to be sinusoidal, additional features may also be implemented in software. In this paper it is shown that the compensation of voltage harmonics, flicker, and even voltage transients are all possible to some extent. The power required for the series voltage injection does not need to originate from the same phase where it is injected. Drawing power from the less problematic phases can also be used to increase the voltage symmetry on the unregulated side of the device. It is shown in the paper, that at partial load the complete deactivation of one phase in the active rectifier stage can not only help with asymmetry, but can also increase the efficiency of the system. A method is proposed for the seamless transfer in the active rectifier stage from 3-phase to 2-phase operation and back. It is also shown in the paper, that phase deactivation and electronic bypass of the injection transformer is possible in the output stage as well. The three level half bridge circuit configuration enables this without additional components.

An Approach for Hybrid Optimal Power Flow Strategies with Optimal Allocation of Distributed Generators for a Power Network

The OPF difficulties are characterized by the presence of four distinct objective functionswhich are: active powerlosses,fuel operating costs and voltage variations. The volatile and variable nature of distributed generator (DG) sources contributes to the convolutionof the optimum power flow (OPF) issue. This paperemployed bat algorithms to tackle the issue of optimumpower flow (OPF)and PSO algorithm to optimal allocation of DG. The goal was to enhance the effectiveness of energy use, environmental sustainability, and cost efficiency of the electricity grid. The test cases include a wide range of scenarios, including the existence of Distributed Generation (DG), different locations of DG within the network, various kinds of load expansion, and occasional breakdowns of transmission lines. These possibilities are considered in order to address the problem presented by the suggested solution OPF. The incidents are assessed utilizing bus systems, such as the 30 bus systemin MATLAB.

Small-Signal Modeling and Frequency Support Capacity Analysis of Power Load Considering Voltage Variation Effect

Small-Signal Modeling and Frequency Support Capacity Analysis of Power Load Considering Voltage Variation Effect

Ensuring grid resilience: Voltage stability analysis and contingency ranking in electric power systems

Modern-day power systems are highly stressed and operate close to the stability limit. The bus voltage variation in power systems generally infringes on the researcher's mind about voltage stability. The main focus of this manuscript is the voltage stability problem and voltage security assessment rather than the angle stability problem. Voltage security can be determined by running a full-load AC load flow with contingency analysis. In real-time analysis, running thousands of contingencies in online mode is quite a cumbersome task, so here in this manuscript, we have proposed a functional link-based ANN for voltage security assessment and then predicted the weakest voltage control area by the entropy concept along with the placement of FACTS devices according to the voltage control area weakness factor and contingencies ranking. The novel technique is then tested with IEEE-14 Bus and IEEE-30 Bus systems with voltage stability performance indicators.

The effect of switching and cycle-to-cycle variations of RRAM on 4-bit encryption/decryption process

The resistive RAM (RRAM) based in-memory computation is a promising technology to overcome the Von-Neumann bottleneck to provide fast and efficient computation. The RRAM is the most appropriate choice for cryptographic applications like encryption/decryption in which the data is computed and stored in the memory itself which enhances the security. The variability issue of RRAM namely switching or device parameter variations and cycle-to-cycle variations deteriorates the functionality of RRAM based circuits. In this paper, the XOR gate with V/R-R logic and a 4-bit encryption/decryption process are implemented using the RRAM Stanford model integrated in the Cadence circuit simulator. The output voltage variations of XOR gate and the encryption/decryption by varying switching and cycle-to-cycle parameters are analyzed. The range of switching parameters of the model that provides the accurate outputs of XOR gate and encryption/decryption is determined.

Fault Handling and Localization Strategy Based on Waveform Characteristics Recognition with Coordination of Peterson Coil and Resistance Grounding Method

To address challenges in locating high-impedance grounding faults (HIGFs) and isolating fault areas in resonant grounding systems, this paper proposes a novel fault identification method based on coordinating a Peterson coil and a resistance grounding system. This method ensures power supply reliability by extinguishing the fault arc during transient faults with the Peterson coil. When a fault is determined to be permanent, the neutral point switches to a resistance grounding mode, ensuring regular distribution of zero-sequence currents in the network, thereby addressing the challenges of HIGF localization and fault area isolation. Fault calibration and nature determination rely on recognizing neutral point displacement voltage waveforms and dynamic characteristics, eliminating interference from asymmetric phase voltage variations. Fault area identification involves assessing the polarity of zero-sequence current waveforms attenuation during grounding mode switching, preventing misjudgments in grounding protection due to random initial fault angles and Peterson coil compensation states. Field experiments validate the feasibility of this fault location method and its control strategy.

The Impact of Wide Discharge C-Rates on the Voltage Plateau Performance of Cylindrical Ternary Lithium-Ion Batteries

Battery voltage plateau characteristics are crucial for designing and controlling battery management systems. Utilising the plateau period attributes to their fullest extent can enable optimal battery control, enhance battery performance, and prolong battery lifespan. This research aimed to investigate the performance of cylindrical ternary lithium batteries at various discharge rates, focusing on the variations in terminal voltage, capacity, and temperature. The battery performance at different discharge rates was meticulously examined through cyclic charge/discharge experiments. The convexity of the voltage curve was used to analyse the voltage plateau characteristics at different rates. The findings revealed significant differences in battery performance under varying discharge rates. Higher discharge rates resulted in shorter discharge times and lower battery voltages at corresponding residual capacities. The discharge time, capacity, and voltage during the plateau phase decreased as the discharge rate increased. At discharge rates of 1 C, 3 C, 5 C, 7 C, 9 C, and 11 C, the proportion of discharged battery capacity ranged from 86.45% to 78.42%. At the same time, voltage and temperature variations during the plateau period decreased significantly compared to those before and after discharge. This research provides a crucial reference point for advancing battery design and thermal management systems.

Fully Printed Negative-Capacitance Field-Effect Transistors with Ultralow Subthreshold Swing and High Inverter Signal Gain.

The switching of conventional field-effect transistors (FETs) is limited by the Boltzmann barrier of thermionic emission, which prevents the realization of low-power electronics. In order to overcome this limitation, among others, unconventional device geometry with a ferroelectric/dielectric insulator stack has been proposed to demonstrate stable negative-capacitance behavior. Here, the switching of the ferroelectric layer behaves like a step-up amplifier and results in a body factor less than 1. This implies a larger change in the semiconductor surface potential compared to the applied gate voltage variation. The transistors with such ferroelectric/dielectric stack are known as negative-capacitance field-effect transistors (nc-FETs), and can demonstrate a subthreshold slope lower than the Boltzmann's limit (60 mV/decade). While nc-FETs have typically been realized with high-vacuum-deposition processes, here we show fully printed nc-FETs with amorphous indium-gallium-zinc oxide (a-IGZO) as the semiconductor material, Al2O3 as the dielectric, and poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) as the polymer ferroelectric. The printed nc-FETs demonstrate an extremely low subthreshold slope of ∼2.3 mV/decade at room temperature, which remains below the Boltzmann's limit for over 5 orders of magnitude of drain currents. Furthermore, the unipolar depletion-load-type inverters fabricated using n-type nc-FETs have demonstrated an extraordinary signal gain of 2691.

Circuits implementations using carbon nanotube field-effect transistor nanotechnology

Device scaling is a pivotal aspect in the field of electronics, aimed at enhancing the performance of integrated circuits (ICs) by reducing the dimensions of transistors. The device scaling presents the short channel effects (SCEs) in the nanoscale regime. To address the SCEs, nanometer IC designers have turned to the carbon nanotube field-effect transistor (CNTFET) technology, which offers unique properties and mitigates the challenges associated with transistor scaling. In this research work, a leakage reduction technique known as the input-dependent (INDEP) method is suggested to tackle the leakage current issue at the nanoscale regime using CNTFET technology. The INDEP method involves the incorporation of two additional transistors within the logic circuit. To evaluate the efficacy of the INDEP method, a CNTFET-based 7-stage inverter chain is meticulously designed at 32 nm CNTFET technology node. Subsequent comparative analysis against alternative designs is conducted, assessing performance metrics such as power dissipation, delay, and power delay product (PDP). The suggested INDEP method reduces power dissipation by 83.75% and improves PDP by 78.44%. Furthermore, the study delves into the impact of process, voltage, and temperature (PVT) variations. Additionally, the investigation explores the influence of parameters such as the number of carbon nanotubes, temperature, supply voltage, and chiral indices on the performance of the 7-stage inverter chain. The simulation results demonstrate that the CNTFET-based INDEP technique yields promising outcomes, characterized by low power dissipation, precise output, and minimal uncertainty across all evaluated metrics.

A Non-Linear Successive Approximation Finite State Machine for ADCs with Robust Performance

This work presents the detailed design of a Successive Approximation Analog to Digital Data Converter (SAR ADC) using bulk 180 nm CMOS IC technology. The focus of the study is on replacing the typical Successive Approximation Register array with a Finite State Machine. This converter features a fully differential and bipolar architecture, which leads to the logic SAR nonlinear behavior. A novel digital control logic mitigates the conversion errors through the conditions in the previous logic states. The logic scheme, in combination with a robust continuous comparator, demonstrates tolerance to Process, Voltage, and Temperature variations. The architecture does not include calibration or additional redundancies in post-layout simulations to emphasize the exclusive benefits of the new SAR logic. The proposed SAR ADC achieves a 14.07 effective number of bits with 7.04 fJ/conversion step Walden figure of merit in biomedical applications.

Subthreshold read operations in 3D PCM: 1S1R device modeling and memory array analysis

3-D phase change memory (PCM) is one of the most promising next-generation nonvolatile memory, and the subthreshold sensing strategy can effectively improve its limited endurance. In this study, we propose a one-selector-one-resistor (1S1R) model with Monte Carlo (MC) function and provide array configurations for the worst case and the maximum bit line voltage (VBL-max), respectively. Based on these, the read window margin (RWM) is evaluated with various array sizes, OTS threshold voltage variations (σvar), and bias voltages (VBias). Our results reveal that the RWM increases as the VBL approaches the VBL-max. Larger arrays lead to an increased leakage current difference, while larger σvar values result in decreased cell current difference and VBL-max. The decrease in VBL-max further deteriorates the RWM. Additionally, we analyze the optimal VBias for 2-deck arrays achieves a 7% reduction in leakage energy consumption and a 22.6% increase in RWM compared to the V/2 bias. The optimal VBias depends on OTS devices and array sizes.

Design and implementation of an innovative single-phase direct AC-AC bipolar voltage buck converter with enhanced control topology

Direct AC–AC converters are strong candidates in the power converting system to regulate grid voltage against the perturbation in the line voltage and to acquire frequency regulation at discrete step levels in variable speed drivers for industrial systems. All such applications require the inverted and non-inverted form of the input voltage across the output with voltage-regulating capabilities. The required value of the output frequency is gained with the proper arrangement of the number of positive and negative pulses of the input voltage across the output terminals. The period of each such pulse for low-frequency operation is almost the same as the half period of the input grid or utility voltage. These output pulses are generated by converting the positive and negative input half cycles in noninverting and inverting forms as per requirement. There is no control complication to generate control signals used to adjust the load frequency as the operating period of the switching devices is normally greater than the period of the source voltage. However, high-frequency pulse width modulated (PWM) control signals are used to regulate the output voltage. The size of the inductor and capacitor is inversely related to the value of the switching frequency. Similarly, the ripple contents of voltage and currents in these filtering components are also inversely linked with PWM frequency. These constraints motivate the circuit designer to select high PWM frequency. However, the alignment of the high-frequency control input with the variation in the input source voltage is a big challenge for a design engineer as the switching period of a high-frequency signal normally lies in the microsecond. It is also required to operate some high-frequency devices for various half cycles of the source voltage, creating control complications as the polarities of the half cycles are continuously changing. This requires at least the generation of two high-frequency signals for different intervals. The interruption of the filtering inductor current is a big source of high voltage surges in circuits where the high-frequency transistors operate in a complementary way. This may be due to internal defects in the switching transistors or some unnecessary inherent delay in their control signals. In this research work, a simplified AC–AC converter is developed that does not need alignment of high-frequency control with the polarity of the source voltage. With this approach, high-frequency signals can be generated with the help of any analog or digital control system. By applying this technique, only one high-frequency control signal is generated and applied in AC circuits, as in a DC converter, without applying a highly sensitive polarity sensing circuit. So, controlling complications is drastically simplified. The circuit and configuration always avoid the current interruption problem of filtering the inductor. The proposed control and circuit topology are tested both in computer-based simulation and practically developed circuits. The results obtained from these platforms endorse the effectiveness and validation of the proposed work.

Augmented Two-Stage Hierarchical Controller for Distributed Power Generation System Powered by Renewable Energy: Development and Performance Analysis

The sustainable development of an area is highly reliant on a reliable electrical energy supply. Microgrids are important in integrating distributed energy resources (DERs) using power electronic converters. However, microgrid control becomes challenging with the increasing number of distributed generators and loads. With the conventional droop control method, power contributions from DER converters cannot be accurately shared due to a mismatch of line impedances. In this paper, an augmented hierarchical control mechanism is proposed to solve the issues mentioned above. This hierarchical control mechanism consists of primary and secondary controllers. The primary stage utilized the droop controller to improve optimal power flow, mainly for the resistive network. The secondary stage is based on an improved methodology to compensate for the voltage and frequency variations during small and large signal disturbances. Moreover, the modelling and analysis for PMSG-based wind energy conversion systems are also presented. The response of the primary controller for active and reactive power sharing is investigated. The analysis emphasizes the demonstration of optimal power-sharing under normal and abnormal conditions for the considered load. Finally, the suggested robust controller’s performance is evaluated in a MATLAB environment, and simulation results show the proposed scheme’s superiority under different operating conditions. The frequency is stable at 50 Hz after a 50 KW load is added.

An Application of Closest Pair of Points Algorithm to Detect the Outliers on the Fixed Solar System

Renewable energy resources are regarded as clean energy sources and effective utilization of these resources reduces ecological effects, produces little secondary waste and they are feasible in light of present and future economic and social societal demands. Solar energy is a radiant light and heat from the sun that may be harvested through a variety of methods, including solar power for producing electricity, solar thermal energy, and solar architecture. Solar technologies generate electricity from the sun, which is considered to be a clean energy source. Solar energy technologies offer a tremendous chance for mitigating greenhouse gas emissions and lowering global warming by replacing traditional energy sources. However, the technologies are not exempted from the operational challenges such as the ever-fluctuating ambient conditions. The intention of this study is to present the experimental outcomes of an application of the closest pair of points algorithm to detect outliers on the fixed solar system. The closest pair of points algorithm is used to find outliers in the system based on the measured voltage from the photovoltaic (PV) panel. The algorithm examines the PV panel’s immediate voltage and compares it to earlier voltage samples to assess whether there is a significant voltage variation that might turn into outliers. The algorithm proved to be extremely precise and efficient in detecting outliers on the fixed solar system. However, the efficiency of the algorithm should yet be verified for larger PV arrays to determine whether it will withstand the test.

Transient and steady‐state performance improvement of two interconnected areas through VSC‐based HVDC transmission line using multi‐purpose control strategies

AbstractThis paper presents various control strategies to improve operations in two interconnected areas connected by a VSC‐HVDC transmission line. The main focus is on designing a central control system (CCS) that coordinates control units in both areas. In area 1, an AC voltage control unit is connected to the CCS. In area 2, three control units including a load power control unit, a fault detection unit, and an AC voltage control unit are also connected to the CCS. The CCS receives inputs from these units and generates commands for the DC voltage and active/reactive power control units on both sides of the DC line. The first proposed strategy addresses permanent voltage drops caused by load fluctuations in area 2. It adjusts the transmitted power from area 1 based on voltage variations in area 2. The second strategy focuses on mitigating faults in area 2 by injecting active and reactive power from area 1 during such events. The third strategy resolves transient voltage oscillations in both areas by controlling the reactive power of stations on either side of the DC line. Simulations using MATLAB‐SIMULINK demonstrate that these mechanisms successfully achieve their objectives.

Multivariate signal-to-noise ratio as a metric for characterizing spectral computed tomography

Objective. With the introduction of spectral CT techniques into the clinic, the imaging capacities of CT were expanded to multiple energy levels. Due to a variety of factors, the acquired signal in spectral CT datasets is shared between these images. Conventional image quality metrics assume independence between images which is not preserved within spectral CT datasets, limiting their utility for characterizing energy selective images. The purpose of this work was to develop a metrology to characterize energy selective images by incorporating the shared information between images within a spectral CT dataset. Approach. The signal-to-noise ratio (SNR) was extended into a multivariate space where each image within a spectral CT dataset was treated as a separate information channel. The general definition was applied to the specific case of contrast to define a multivariate contrast-to-noise ratio (CNR). The matrix contained two types of terms: a conventional CNR term which characterized image quality within each image in the spectral CT dataset and covariance weighted CNR (Covar-CNR) which characterized the contrast in each image relative to the covariance between images. Experimental data from an investigational photon-counting CT scanner was used to demonstrate the insight of this metrology. A cylindrical water phantom containing vials of iodine and gadolinium (2, 4, and 8 mg ml−1) was imaged under conditions of variable tube current, tube voltage, and energy threshold. Two image series (threshold and bin images) containing two images each were defined based upon the contribution of photons to reconstructed images. Analysis of variance (ANOVA) was calculated between CNR terms and image acquisition variables. A multivariate regression was then fitted to experimental data. Main Results. Image type had a major difference on how Covar-CNR values were distributed. Bin images had a slightly higher mean and wider standard deviation (Covar-CNRlo: 3.38 ±17.25, Covar-CNRhi: 5.77 ± 30.64) compared to threshold images (Covar-CNRlo: 2.08 ±1.89, Covar-CNRhi: 3.45 ± 2.49) across all conditions. ANOVA found that each acquisition variable had a significant relationship with both Covar-CNR terms. The multivariate regression model suggested that material concentration had the largest impact on all CNR terms. Signficance. In this work, we described a theoretical framework to extend the SNR to a multivariate form that is able to characterize images independently and also provide insight regarding the relationship between images. Experimental data was used to demonstrate the insight that this metrology provides about image formation factors in spectral CT.