Voltage Quality Research Articles

Model Predictive Control-Based Active/Reactive Power Regulation of Inverter Air Conditioners for Improving Voltage Quality of Distribution Systems

Model Predictive Control-Based Active/Reactive Power Regulation of Inverter Air Conditioners for Improving Voltage Quality of Distribution Systems

Improvement of Voltage Quality in a Distribution System by a Novel Simplified Unit Vector Theory

Improvement of Voltage Quality in a Distribution System by a Novel Simplified Unit Vector Theory

Deep reinforcement learning based reactive power regulation and its optimization in power grids

Abstract The study applies the Markov game to grid reactive power regulation based on deep reinforcement learning theory, constructs the Markov game for grid optimization problems, and optimizes it using the HAPPO algorithm to explore real-time grid optimization strategy based on multi-intelligence body reinforcement learning. On the basis of the optimization strategy, the grid power management method based on deep reinforcement learning is explored through the Markov decision process and the improved deep deterministic policy gradient method, and the grid operation optimization model based on deep reinforcement learning is constructed. The model is then examined in terms of arithmetic cases. The maximum error of the model in this paper is less than 5%, and the accuracy of the fitting is high. The node voltage has a maximum voltage offset of 0.0025, resulting in high voltage quality. The real-time optimization solves for an average voltage offset that is 97.9% lower and a maximum voltage offset that is 75.4% lower compared to the long-term scale reactive power optimization. The average running cost and standard deviation of the model increase with greater communication impairment. The model approach in this paper performs the best in terms of optimization cost, reducing it by 1.12%, 6.67%, 10.93%, and 0.94% compared to the other four approaches.

Methology of experimental research of voltage quality in electrical circuit

Methology of experimental research of voltage quality in electrical circuit

A Hybrid Modulation Technique for Operating Medium-Voltage High-Power CHB Converters Under Grid Voltage Disturbances

Power converters, and particularly multilevel converters, are key elements in the current energy scenario. Among them, Cascaded H-Bridge Converters (CHB) are a popular and versatile solution for many industrial applications. Technical literature provides multiple modulation techniques for its operation. Among them, hybrid-PWM modulation techniques provide a good trade-off between switching loss and output voltage quality. In this work a hybrid modulation technique is presented which allows not only the fundamental block switching operation of some power cells but also a harmonic control over a specific harmonic distortion present in the grid. To validate the operation of the proposal, several experimental results have been reported to demonstrated the good behaviour of the proposed modulation technique.

A Comprehensive Approach to Flexible LVRT Strategies for Inverter-Based PPMs Enhancing Voltage-Support, Overcurrent Protection, and DC-Link Voltage Quality

A Comprehensive Approach to Flexible LVRT Strategies for Inverter-Based PPMs Enhancing Voltage-Support, Overcurrent Protection, and DC-Link Voltage Quality

Ensuring sustainability of the power supply system of mining enterprises in the conditions of war risks

In the work, a study of the conditions of normal operation of the power supply system of mining enterprises with limited capacity of the power system was carried out. Based on complex studies, conclusions were drawn about the structure of electrical loads in coal mines, which are characterized by a non-linear and non-symmetric nature. The problem of higher harmonics and interharmonics with limited short-circuit power, which is characteristic of an autonomous power supply system, is highlighted. Stable operation of the power supply system and main consumers is achieved by matching the mode of the generator set with the mode parameters of the load. New dependencies of regime parameters were obtained, which evaluate energy efficiency in complex situations caused by military risks. Experimental studies of voltage quality indicators and energy efficiency in the conditions of power supply systems of coal mines of Ukraine confirmed the adequacy of the proposed analytical models.

SIMULATION AND RESEARCH OF SINGLE-PHASE SHORT CIRCUITS IN THE ELECTRICAL NETWORK

The purpose of this work is to model single-phase short circuits in a three-phase electrical network and identify their type by analyzing the angular frequency of the spatial vector. Recently, the saturation of electric networks with powerful non-linear loads, the introduction of conversion equipment and renewable energy sources lead to the need for systematic analysis and research of the quality of electric energy (QEE). One of the factors that significantly affect the operation of electrical equipment is short circuits. In the article, based on the developed model of the formation of QEE distortions, a single-phase short circuit in a three-phase electrical network is investigated by switching it to a single-phase system with two α-β projections and a zero-sequence voltage vector.
 Studies of the influence of the location of the short-circuit point on the voltage in the electrical network have shown that the difference in the distance from the point of damage to the load, type of short-circuit leads to varying degrees of voltage change. Conducted studies have shown that different types of malfunctions and parameters of the electrical network at the point of short circuit cause different disturbances in the electrical voltage in the power supply system. The presence of a short circuit of the same type at different locations leads to different voltage drops and overvoltages. Short-term changes in voltage are the most common distortions of the quality of electrical voltage in electrical networks. The simulation results based on the developed model are consistent with the theory and reliably simulate the change in voltage in the electrical network.
 In the future, the presented model can help in creating a basis for the identification and subsequent control measures of voltage change violations.

Design, Modeling, and Validation of Grid-Forming Inverters for Frequency Synchronization and Restoration

This paper focuses on the modeling, analysis, and design of grid-forming (GFM) inverter-based microgrids (MGs). It starts with the development of a mathematical model for three-phase voltage source inverters (VSI). The voltage and current controllers consist of two feedback loops: an outer feedback loop of the capacitance-voltage and an inner feedback loop of the output inductance current. The outer voltage loop is employed to enhance the controller’s response time. The inner current loop is used to provide active damping for the resonance created by the LCL filter. A two-layer control scheme is adopted for the GFM inverter control. The primary decentralized control uses droop control and virtual impedance loops to share active and reactive power. Simultaneously, the centralized secondary control addresses frequency and amplitude deviations induced by the droop control. Additionally, a synchronization loop is proposed for seamless reconnection of GFM inverters to the MG and to connect the GFM-controlled MG to the main grid. It has the advantage that the inverter operates in GFM mode even after the synchronization has occurred. The simulation results have shown that the voltage controller ensures a 0.005 s settling time and maintains the steady-state error at its minimum value of 0.1 V. Similarly, the current controller ensures a 0.006 s settling time with a 10−5 steady-state error. The system with the designed controller has a low total harmonic distortion (THD) of 1.46% and improved power quality of the output voltage. Furthermore, a quick restoration time is observed during load steps and tripping events, with a restoration time of 1 s with 10−10 steady-state error. Synchronization is achieved within 0.8 s for the incoming inverters and requires 3 s to synchronize the MG with the main grid, maintaining a steady-state error of 10−9.

Analysis of unified power quality conditioner errors

This article is devoted to error analysis of the unified power quality regulator. In the context of the growing importance of reliable and high-quality power supply, power quality regulators are becoming key devices to ensure the stability of networks and meet the needs of domestic consumers. The paper proposes a comprehensive approach to error analysis of the unified power quality conditioner, the main purpose of which is to compensate for the impact of rapidly changing loads on power quality. At the same time, indicators of general harmonic distortion of the quality of electricity are analyzed, and factors such as the magnitude and duration of loads are also taken into account. A large part of the article is devoted to the study of the sources of errors in unified power quality conditioner. A comparison of the parallel-serial and series-parallel topologies of unified power quality conditioner is performed. The influence of the unified power quality conditioner control algorithm on the formation of errors of each topology is analyzed. Using Matlab/Simulink computer simulation tools, the article proposes a framework for error quantification, which allows accurate estimation of errors at various stages of unified power quality conditioner operation. This framework covers the Fourier series transformation of voltage and power for comprehensive estimation of error magnitudes. To confirm the effectiveness of the proposed error analysis and compensation strategies, the article presents graphs of simulation results in the time and frequency domains. Active and reactive power generation errors and voltage setpoint errors are described. These findings emphasize the ability of unified power quality conditioner to improve the quality of electricity, despite measurement errors. The main results include the analysis of deviations of voltage quality indicators, the establishment of a connection between compensation errors and deficiencies in the functioning of the system, as well as the development of recommendations for improving the efficiency of compensation devices.

The effect of a pre-reconstruction process in a filtered backprojection reconstruction on an image quality of a low tube voltage computed tomography.

This study aims to evaluate the effect of pre-reconstruction process for low tube voltage computed tomography (CT) on image quality of filtered backprojection (FBP) reconstruction. Small and large quality assurance water phantoms (19 and 33cm diameter) were scanned on a third-generation dual-source CT with 70 kVp and 120 kVp at various dose levels. Image quality was assessed in terms of the noise power spectrum (NPS) and task-based transfer function (TTF). NPSs and TTFs in the small phantom were comparable between 70 and 120 kVp protocols. In the large phantom, the curves of the NPS changed and the TTF decreased even at the high-dose levels for 70 kVp protocol compared to 120 kVp protocol. Our results indicated that the pre-reconstruction process is performed in low tube voltage CT for large objects even for the FBP reconstruction and has an effect on the image quality.

Multi-channel switching magamp power converter for radio recieving devices

Development of high-quality energy supply of radio receiving devices is an urgent task. The article discusses the methods of designing high-frequency multi-channel power converters based on high-frequency magnetic amplifiers, the magnetic cores of which are made of an amorphous alloy with a rectangular hysteresis loop. Their significant advantages when powering radio receiving devices are the high quality of the output voltages and the low level of electromagnetic interference, both radiated and conductive. At the same time, they have a higher level of dynamic characteristics, reliability and efficiency while reducing their topological complexity and cost. In addition, it allows the implementation of multi-channel power converters with equivalent and independent output channels in a wide range of output powers. The paper presents the implementation of such a converter for powering radio receiving devices.

Control Strategies for Enhancing Power Quality with Unified Power Quality Conditioner in a Solar-PV Integrated Utility System

The electrical utility systems are well-liked as local energy systems because of their capacity to incorporate renewable energy, enhance energy effectiveness and strengthen the resilience of the power system. These benefits do, however, come with specific complications regarding control and power quality (PQ). PQ within a utility system is paramount to ensure the appropriate operation of connected devices and the well-being of the overall system. As a result, both voltage quality & current quality are significant. Control strategies in conjunction with cutting-edge power electronics devices (PED) offer a solid framework to handle PQ challenges. Hence, this paper’s proposed work discusses the application of a Solar-Photovoltaic (PV) fed Unified Power Quality Conditioner (UPQC) for power quality enhancement towards the supply grid network. The Solar-PV fed UPQC enhances PQ and maximizes solar energy utilisation, leading to an eco-friendly and cost-effective solution while injecting clean, renewable energy into the grid. In this paper, the control strategies for UPQC are based primarily on the Adaptive Leaky Least Mean Square (AL_LMS) algorithm as compared with the Synchronous Reference Frame (SRF) based theory for switching of series and shunt active converters of UPQC. This AL_LMS approach extracts reference signals to switch UPQC’s shunt and series voltage source converters (VSCs) by iteratively updating the weights. Thus, the control strategy applied to Solar-PV fed UPQC mitigates voltage problems like voltage sag and swell, current harmonic distortions and other PQ issues. The work is done in MATLAB/ Simulation software and simulation outcomes show the effectiveness of Solar-PV fed UPQC in improving power quality by maintaining within the IEEE-519 Standards.

Optimal electric vehicle scheduling in unbalanced distribution system by spatial and temporal data mining and bi‐level particle swarm optimisation

AbstractThis research proposes a new comprehensive methodology aimed at optimally managing electric vehicle (EV) charging in an unbalanced distribution system with consideration of grid capacity and voltage quality constraints as well as the stochastic driving and charging behaviour of EV users. A data mining algorithm is designed to generate suitable spatial and temporal EV and charger input data for EV scheduling that is decomposed into two subproblems. The lower‐level subproblem identifies the maximum load at each node and time and the upper‐level subproblem allocates charging slots for each EV being charged. Both subproblems are solved by developed particle swarm optimisation (PSO) algorithms. The effectiveness and robustness of the algorithms have been thoroughly validated by conducting rigorous tests on a modified IEEE 37‐bus distribution system with different EV penetration scenarios. The test results have confirmed the algorithms' performance in accommodating the increasing load associated with EV charging and successfully improving the system performance by maximising the system load factor, minimising load unbalance, and reducing the system power loss. All operational constraints on node voltages, and distribution transformer and feeder capacities of the existing power distribution infrastructure are fully respected while maintaining high user satisfaction represented by the average state of charge (SoC) of all EVs.

A novel ANFIS-controlled customized UPQC device for power quality enhancement

Power quality is crucial for the reliable and efficient operation of domestic and industrial loads. Nonlinear power electronic converter loads have increased in usage, which has led to a decline in both voltage and current quality. To overcome these power quality issues, a universal power quality compensator (UPQC) has been developed and integrated into the power distribution network. The UPQC comprises dual active power filters which are equipped with a DC-link capacitor. The voltage of the DC-link capacitor is controlled by a DC-link voltage controller. However, the conventional PI controller is not suitable for regulating voltage at a defined level due to inappropriate gain values. In this work, we propose an intelligent adaptive neuro-fuzzy inference system-based DC voltage controller for customized UPQC devices. The proposed control scheme aims to mitigate the existing power quality challenges by reducing the issues in classical controllers and incorporating intelligence knowledge with subjective decisions. Using the MATLAB/Simulink software tool, we have tested a customized UPQC device controlled by ANFIS for critical operation and performance. The simulation results are presented along with valid comparisons.

Methods to Minimize the Effects of Geometric Asymmetry of Multi-Circuit, Multi-Voltage Overhead Lines on Transmission Network Operation

Multi-circuit, multi-voltage overhead lines (MMOLs) are becoming a favorable solution in the perspective of ensuring the efficient transmission of electrical energy and limitations relating to the expansion of the transmission network. The main part of this manuscript contains a method that minimizes the effects of risks on the operation of the power system due to asymmetrical MMOLs, with particular emphasis on the circuit with the lowest-rated voltage. The selected set of criteria includes elements such as the determination of the neutral point displacement voltage in the network with the lowest-rated voltage (zero voltage, U0), selected voltage quality factors, and short-circuit analyses to examine the impact of differences between the use of accurate and simplified mathematical models on the calculation of short-circuit currents. Methods to minimize the effects of MMOL geometric asymmetry have been proposed using simple technical steps, such as selecting the appropriate pole silhouette (indication of the methodology for identifying such supporting structures), changing the way of supplying individual circuits, or using partial transposition in the circuit with the lowest-rated voltage. The proposed methods are verified by analyzing a case study of the development of the transmission network in Poland.

Assessment of Novel Self-tuned Emotional Learning-based Intelligent Controller for Bidirectional Cascaded Quasi-Z-Source DC–DC Converter Control

The self-tuned emotional learning-based intelligent controllers (STELBICs) are suggested to regulate a bidirectional cascaded quasi-Z-source DC-to-DC converters (BC-qZSCs). The bidirectional converters of DC-to-DC with a huge voltage conversion range are required in current times for voltage matching in a variety of applications, particularly electric automobiles. The BC-qZSC may raise or buck the voltage, and electricity flows in both directions. The switch’s duty cycle can be changed to keep the voltage steady. To produce a consistent output voltage, a good controller design is necessary. To enhance the performance of BC-qZSC in both operating modes, this study introduces a unique STELBIC. The proposed novel controller’s performance is evaluated by comparing it with an artificial neural networks-controlled converter and a traditional Proportional Integral-controlled converter. In both boost and buck modes of operation, the controller’s performance is evaluated in terms of voltage quality, including steady-state error, settling time, and voltage ripple. Matlab/Simulink is used to analyze the entire system.

Allocation of PV Systems with Volt/Var Control Based on Automatic Voltage Regulators in Active Distribution Networks

This paper presents an optimal allocation methodology of photovoltaic distributed generations (PVDGs) with Volt/Var control based on Automatic Voltage Regulations (AVRs) in active distribution networks considering the non-dispatchable mode of PVDG operation. In the proposed methodology, an intelligent coordinated Var control is activated via controlling the AVR tap position and the Var injection of PV inverters to achieve a compromise between reducing active and reactive power losses and enhancing voltage quality in a distribution network. Also, the scheduled power factor mode of operation is investigated for the PV inverters. Added to that, the proposed allocation methodology is handled on the basis of hourly loading variation under simultaneous control modes of PV inverters and AVR. Moreover, the impacts of the specified number of PVDGs are assessed on the distribution system’s performance. A recent effective optimizer of the slim mold algorithm (SMA) is dedicated to solving the proposed optimization framework. The simulation implementations are executed on a practical distribution network of the Kafr Rabea area related to South Delta Electricity Company in Egypt. Also, the application is conducted for a large-scale distribution network from the metropolitan area of Caracas. The proposed methodology provides superior performance in minimizing the active and reactive power losses and improving the voltage profile.

Analysis of the Effect of Capacitor Placements at High and Low Voltage Transformer Sides as Voltage Profile and Total Cost in Distribution Systems

This study mentions the problem of determining optimal placements and sizes for capacitor banks by comparing different schemes that allow implemented buses at both high and low voltage side, only high voltage side or low voltage side of transformers in distribution systems. Criterions evaluated for each scheme are active and reactive power losses in whole system, voltage value at all buses, installation and operation cost and accumulative profit saving. Standard with and without transformer branches in distribution systems and Newton-Raphson method are introduced to make clear about the way to analyze power flows in whole system. Optimal placements and sizes for capacitor banks are determined by using a proposed algorithm and optimal capacitor placement tool in ETAP software. Simulation results can help to show the comparisons, evaluations and make decision about optimal capacitor placements and sizes. The contribution shows the best scheme that install capacitors at low voltage side of transformers because it has the lowest implemented capacity, highest economic factors while voltage quality is always in allowable range. Achieved results can be applied in any distribution system, help managers have overall review and decide optimal placements and sizes for capacitor banks. Keywords: Capacitor bank, OCP Tool, ETAP software, Optimal placement, Optimal size, Voltage quality, Optimal cost.

Study on the interaction of vehicle-to-grid and its impact on power quality of electric grid

With the continuous increase in the number of electric vehicles (EVs) in the market, both EVs and charging stations are rapidly developing. This paper provides an overview of the negative impacts of EV charging on the distribution grid at the current stage. It summarizes specific solutions proposed by scholars both domestically and internationally to address the effects on voltage, harmonics, and power quality. These solutions mainly involve the addition of filters to the distribution grid, the use of 12-pulse rectifiers, and series resonance. Furthermore, the paper analyzes how Vehicle-to-Grid (V2G) technology can balance the grid and regulate power quality issues caused by EV charging, ensuring stable system operation. V2G technology also enables EVs to function as mobile energy storage devices and allows for rational energy distribution using bidirectional charging stations. The integration of charging stations with the grid, forming a connected vehicle network, is considered the future direction of EV development.