Proper Reactive Power Research Articles

FC-PV-battery-Z source-BBO integrated unified power quality conditioner for sensitive load & EV charging station

The proposed integrated system combines of fuel cell (FC), photovoltaic (PV), battery, Z-source and Biogeography-Based Optimization (BBO) based Unified Power Quality Conditioner (UPQC) compensator aims to provide a high-quality power supply to sensitive loads, such as electrical, electronics, medical equipment, Electrical Vehicles (EV), or critical industrial processes. It can regulate voltage, mitigate power disturbances (e.g., voltage sags, swells, flicker, voltage interruption, harmonics, reactive power etc.), and ensure a stable power supply. Additionally, it can facilitate EV charging stations by managing the power flow and optimizing charging processes. The PV or FC based Z-source inverter can control and regulate power flow in both directions. It operates with a unique impedance network, allowing for voltage boosting or bucking. The Z-source inverter enhances the flexibility and control of power flow in the system. The fuel cell generates electricity through an electrochemical process, typically using hydrogen as a fuel source, while the PV array converts sunlight into electrical energy. The FC-PV system provides a renewable and clean energy source. The battery serves as an energy storage device within the integrated UPQC system. It stores excess energy produced by the FC-PV system or from the grid during off-peak hours and releases it when needed, contributing to load balancing and stability. Biogeography-Based Optimization (BBO)-based Selected Harmonic Elimination Pulse Width Modulation (SHE-PWM) technique calculate the proper inverter switching angles and control the total harmonic distortion (%THD). Grid connected EV charging station produce nonlinear current and pollute the DC-link system. The proposed FC-PV-Z source-BBO based UPQC and its control strategy can enhance the EV-charging induced PQ (power quality) issues, eliminate the voltage and current harmonic or reduce overall voltage and current %THD control the proper reactive power, improve the power factor, restoring the flicker, transient, swells and sags of the micro grid, grid or smart grid and completely moderate the fluctuations of DC-link voltage.

Reactive power optimization in distribution systems considering load levels for economic benefit maximization

Introduction. The need for electrical energy has been increased sharply due to hasty growth in industrials, social and economic improvements. From the previous studies, it has been agreed that almost 13 % of the total power generated is wasted as heat loss at distribution level. It has been extensively recognized that the node voltage profile along the distribution system can be enhanced under steady state power transfer controlled by proper reactive power compensation. Capacitors have been acknowledged as reactive power compensating device in distribution systems to achieve technical and economical benefits. Novelty of this work is the application of Archimedes optimization algorithm for reactive power optimization in distribution systems so as to obtain an improved solution and also a real 94-bus Portuguese network and modified 12-bus network has been taken and validated for three different load levels which are totally new. Purpose of the proposed work is to maximize the economic benefit by reducing the power loss and capacitor purchase cost at three different load conditions subject to satisfaction of equality and inequality constraints. Methods. The economic benefit has been validated using Archimedes optimization algorithm for three load levels considering three distribution systems. Results. The computational outcomes indicated the competence of the proposed methodology in comparison with the previously published works in power loss minimization, bus voltage enhancement and more economical benefit and proved that the proposed methodology performs well compared to other methods in the literature.

Intelligent Optimized Voltage Control for Hybrid Off-Grid Power Systems

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

Novel Compensation Methods Using Energy Storage System (ESS) in Islanded Unbalanced Single-/Three-Phase Multimicrogrids

The integration of single-phase microgrids (MG) and unbalanced loads to three-phase MGs results in power quality issues at the point of common coupling (PCC). These issues include unbalanced voltage, unequal power flow, and inaccurate reactive power sharing. In this article, an energy storage system (ESS) has been proposed with novel control methods to help mitigate unbalance issues in these islanded multimicrogrids (MMGs). It presents two novel control methods: modified reverse droop control and multifunction control to compensate the reactive power of the MMG and generate the needed active and reactive power references of the ESS. The developed control methods mitigate PCC voltage and power unbalance of the MMG and also achieve the load power sharing proportionally among different rated photovoltaics (PV) inverters. In addition, the system stability with the proposed control is also presented under different scenarios. The proposed multifunction controller operation is validated using Opal-RT real-time simulator and experimentally using control hardware-in-the-loop. The results demonstrate that the PCC unbalanced voltage and power are reduced significantly by 97.8%, and the proper reactive power sharing is achieved among the different PV inverters in the proposed system.

An Advanced Droop Control Strategy for Reactive Power Assessment in Islanded Microgrids

Inverter based islanded MicroGrids (MGs) are very fascinating but challenging ways to integrate Distributed Energy Resources (DERs) in electric networks. Active and reactive power regulation is a major issue due to the necessity of optimally exploiting the sources characteristics and controlling voltage and frequency. Focusing the attention on the reactive power control, the main needs are to regulate voltage at suitable values and ensure a proper reactive power sharing among the energy sources. The conventional control for reactive power presents relevant drawbacks and so an Advanced Droop Control strategy (ADC) is presented to approach primary voltage control and reactive power sharing among Grid-Supporting inverters in islanded MGs. The ADC strategy is presented defining its control law and the control scheme with a stability analysis. Then, an analytical procedure is developed to set the controller parameters. Following, a comparison between the ADC and droop control is performed with dedicated simulations on a common benchmark Microgrid in order to highlight the advantages of the proposed control strategy. Finally, a comparison with other advanced control techniques is proposed in order to show that ADC is able to guarantee improved performance in terms of the combined regulation of voltage and reactive power.

A Study of Static Var Compensation Using TSC – TCR Shunt Compensator

The notion of reactive power management encompasses a wide range of system and customer challenges, particularly those connected to power quality, because most power quality issues may be mitigated or remedied with proper reactive power control. When strong inductive loads are coupled to transmission lines, the trailing load current causes a problem with power factor. In some cases, very low current flows through the transmission line due to minor load, resulting in a leading parasitic capacitance in the line, resulting experience extreme, causing the load side hand voltage must become twice that of the sending end side voltage (Ferranti effect), especially in long transmission system. To avoid this problem, we developed a new hybrid reactive power control model that uses a simultaneous combo of thyristorcontrolled reactor (TCR) and thyristor switched capacitor (TSC), which will immediately include a sleek current control spectrum from touch sensitive to deductive approach values by varying the firing angle of the transformer via a computer.

Comparative analysis of various compensating devices in energy trading radial distribution system for voltage regulation and loss mitigation using Blockchain technology and Bat Algorithm

The electric power distribution plays a crucial part in the power systems to maintain the power quality and stability of the system for loss mitigation and voltage regulation. The reactive power compensators like a capacitor, DG, and DSTATCOM play a vital role in power quality and stability improvement by providing proper reactive power in the distribution system. This article provides a critical review and comparative analysis of various compensating devices allocation to achieve power loss mitigation and voltage regulation in the radial distribution system (RDS). The Bat Algorithm (BA) and Voltage Stability Index (VSI) are utilized for determining the optimal size and site of the compensating devices in the RDS. Further, the application of Blockchain technology is utilized for voltage regulation of energy trading RDS. To show the effectiveness of the present study, an IEEE 33 test system is considered. All three compensators are implemented in IEEE 33 test system and compared with existing approaches. The present study is very much helpful to the Distribution Network Operators for selecting the suitable compensator in real-time applications.

Harmonic Mitigation Using Passive Harmonic Filters: Case Study in a Steel Mill Power System

In this study, we mitigated the harmonic voltage in a power system that contained the roughing mill (RM) and finishing mill (FM) motor drives. AC/DC converter type RM drive is a non-linear, large-capacity varying load that adversely affects power quality, e.g., a flicker, voltage distortion, etc. The voltage drop can be compensated within a certain limit by using the proper capacity of a power capacitor bank. In addition, the voltage distortion can be controlled as per the guidelines of IEEE Std. 519 using the passive harmonic filter corresponding to the characteristic harmonics of the motor drive load. The passive harmonic filter can provide an economical solution by mitigating the harmonic distortion with a proper reactive power supply. However, at the planning level, attention should be paid to avoid system overvoltage that is caused by the leading power under light load conditions and also the problem of parallel resonance between the harmonic filter and the step-down transformer. In addition, when designing the filter reactor, the K-factor and peak voltage must be considered; the filter capacitor also requires a dielectric material that considers the harmonic peak voltage. The purpose of this study was to acquire a better understanding of the filter applications as well as verify the field measurement, analysis, and design of harmonic filters together with its performance.

Maximum Power Tracking and Power Sharing in Grid Connected WECS Using Modified PFC Rectifier and PR Controlled Inverter

This article presents an improved maximum power tracking and power sharing technique by using a self-recurrent wavelet neural network (SRWNN) controller. A power factor correction (PFC) rectifier as machine-side converter and proportional resonant (PR) controlled three-phase inverter as grid-side converter for wind energy conversion system (WECS) is presented. The modified PFC rectifier ensures the machine to work at maximum power coefficient, by using a sensor less SRWNN controller. Hence, it extracts maximum power at various wind speeds and provides unity power factor operation at generator side so as to increase the efficiency. The PR controlled inverter ensures proper real and reactive power sharing with the grid, which also acts as a distribution static compensator (DSTATCOM), by casting off harmonics at the grid side for nonlinear loads. The wind turbine, generator, converter and controller are modeled in MATLAB/Simulink platform and performance is analyzed for maximum power tracking and power sharing for a 40kVA, 400 V WECS. An extensive analysis of the proposed system is carried out in a developed experimental setup and the results validate the theoretical claims.

A Cyber-Secure Distributed Control Architecture for Autonomous AC Microgrid

Security of various cyber-physical systems is a major concern for researchers worldwide. Nowadays, microgrids also form such cyber-physical system to achieve a number of objectives such as enhanced frequency regulation, economic active power sharing, proper reactive power sharing, etc. Communication links are essential in such microgrids to ensure bilateral flow of data to be fed to the secondary controllers of the distributed generators integrated to the power network. This article, therefore, studies the impact of various kinds of cyberattacks viz., false data injection, denial-of-service, and replay attack on the performance of these communication enabled secondary controllers having potential vulnerabilities. Additionally, it presents a unique framework to ensure system stability when communication links are subjected to such attacks. The analysis has been carried out in a microgrid operating in islanded mode where the controller area network (CAN) bus communication network is utilized to form the cyber-physical system. Simulations are performed in MATLAB/Simulink platform and real-time evaluation of the proposed framework has been carried out in a test bed having OPAL-RT (OP5600) simulator and physical CAN devices to form the communication links.

Towards energy transition: conjoint assessment of large-scale PV system performance and interconnection impacts in isolated microgrid

Environmental, energy security and electricity demand concerns stimulate solar-grid integration. However, intermittent, non-dispatchable PV characteristics may challenge passive grid operation. This paper contains the comprehensive planning and assessment of a 2 MWp CdTe-based PV system deployment proposed for hybrid operation in an isolated 11 kV 10-bus microgrid in Brunei. The presented approach combinedly assesses PV system performance and scenario-based interconnection impacts based on a detailed PV system model considering deployment conditions. Various interconnection points with multiple sets of feeder-specific measured load profiles are examined. Results show the PV system designed for maximum annual generation achieves performance ratio of 90.6%. While time-series power flow assessment reveals grid operation enhancement, there are concerns at times of generation-demand mismatch requiring proper genset sequencing and reactive power management. Meanwhile, faster relay operating time and reverse fault current are demonstrated in existing protection scheme. Dynamic grid stabilities are preserved in various generation intermittency and loss events, including the most challenging condition of further inertia and spinning reserve reduction reaching a frequency of 96.02%. Finally, optimal interconnection point fulfilling multi-objectives on losses, voltage profile and line reserve capacity is identified. The findings indicate a good prospect of the synergy for advancing energy transition. The analysis could facilitate RE planning and policymaking.

REACTIVE POWER CONTROL IN MICRO-GRID NETWORKS USING ADAPTIVE CONTROL

Purpose. Despite their economic and environmental benefits, distributed products in power systems have caused problems in power systems. One of the most important issues in this regard is voltage fluctuations and frequencies in Micro-grids, which depends on several factors, such as variable consumption load and errors in power systems. One of the main challenges associated with the use of Micro-grids is power management among distributed generation sources. Power management plays a pivotal role in numerous Micro-grids and may ensure the stable and improved performance of Micro-grids in the permanent status of the system. The present study aimed to examine the power control in Micro-grids by proposing an adaptive control method along with the PID controller for power management and coordination in Micro-grids. This coordination system operates between production sources and controlling the voltage and frequency levels against the possible disturbances occurring anywhere in the system loop. The results of the simulation of the proposed algorithm in MATLAB software environment exhibited a high success rate (i.e., proper response to the fluctuations in the Micro-grid) and extremely low error rate (i.e., proper reactive power in the grid).

Power Sharing in Hybrid Microgrids Using a Harmonic-Based Multidimensional Droop

Droop-based control strategies are generally used in hybrid microgrids (HMGs) for voltage and frequency regulation in the dc and ac microgrids (MGs). The control of interlinking converters (ICs) that connect ac and dc MGs plays a vital role in the stability and efficiency of HMGs. However, conventional P-V droops for the dc side may not be effective due to line resistances and local nature of voltage. Also, conventional Q-V droops for the ac side may result in circulating power and current among parallel ICs diminishing their performance. In this paper, dc voltage harmonic frequencies are employed to create a global variable in the dc side of HMGs and to introduce an efficient droop control strategy for the dc MG without deteriorating power quality. Accordingly, accurate active power sharing is achieved and circulating power is eliminated. In addition, a three-dimensional (3-D) droop is suggested for voltage control at the ac MG using virtual impedances. Thus, proper reactive power sharing is accomplished among parallel ICs, while circulating currents are suppressed as well. The optimal gains of the 3-D droop are determined via an optimization problem. The efficacy of the proposed method is evaluated by examining it on a typical HMG in different situations.

Transformer Management System for Energy Control of Customer Demand Response and PV Systems

This paper proposes an innovative transformer management system (TMS) for energy control of customer loads and photovoltaic (PV) systems to solve the problems of transformer overloading and overvoltage due to power injection by PV renewable energy. The operation status of distribution transformers is monitored by transformer terminal unit (TTU) and reported to the control master station via the hybrid communication system. The demand response of customer load control is activated to reduce the loading level of transformers for mitigation of overloading problem. For the residential customers with installation of roof top PV system, the TTU is applied to perform the power factor control of smart inverter to prevent the overvoltage problem. The hybrid communication system consisting of power line carrier, LoRa radio frequency, and optical fiber is used to provide two-way communication for data collection and controls of customer loads and PV system. According to the field testing of the proposed TMS in Taiwan Power Company, the adaptive energy control of customer loads by TTU is executed when the overloading problem of distribution transformer occurs. The TTU also performs the power factor control of PV smart inverters to solve the overvoltage problem due to too much of PV power being injected during the solar peak period. The overvoltage problem due to PV power injection has also been solved by TTU for control of PV smart inverters to perform the proper reactive power compensation.

Review of Active and Reactive Power Sharing Strategies in Hierarchical Controlled Microgrids

Microgrids consist of multiple parallel-connected distributed generation (DG) units with coordinated control strategies, which are able to operate in both grid-connected and islanded modes. Microgrids are attracting considerable attention since they can alleviate the stress of main transmission systems, reduce feeder losses, and improve system power quality. When the islanded microgrids are concerned, it is important to maintain system stability and achieve load power sharing among the multiple parallel-connected DG units. However, the poor active and reactive power sharing problems due to the influence of impedance mismatch of the DG feeders and the different ratings of the DG units are inevitable when the conventional droop control scheme is adopted. Therefore, the adaptive/improved droop control, network-based control methods, and cost-based droop schemes are compared and summarized in this paper for active power sharing. Moreover, nonlinear and unbalanced loads could further affect the reactive power sharing when regulating the active power, and it is difficult to share the reactive power accurately only by using the enhanced virtual impedance method. Therefore, the hierarchical control strategies are utilized as supplements of the conventional droop controls and virtual impedance methods. The improved hierarchical control approaches such as the algorithms based on graph theory, multi-agent system, the gain scheduling method, and predictive control have been proposed to achieve proper reactive power sharing for islanded microgrids and eliminate the effect of the communication delays on hierarchical control. Finally, the future research trends on islanded microgrids are also discussed in this paper.

Benefits that could be achieved by a proper reactive power generation in small photovoltaic systems operating inside low voltage distribution network

The reduction of feed-in tariffs and subsidies in the last years substantially decreased the interest of investors for photovoltaic (PV) systems in individual countries and in the European Union in general. From the viewpoint of electricity distribution system operators (DSO) and electricity distribution companies, the PV systems are often observed as the systems that cause additional costs and make network operation difficult, but must be connected to the electricity network due to the existing legislation. Thus, the power of PV systems newly connected to the electricity networks per year decreases substantially. The fact that PV systems can be used not only for active, but also for reactive power generation, is often neglected. If reactive power in PV systems is generated properly, it can satisfy the local reactive power demand, which leads to reduction of network losses. This paper focuses on an existing low voltage distribution network with installed 100 kWp PV power. Its goal is to perform a sensitivity analysis of benefits in the network that could be achieved by the reduction of network energy losses and by the locally generated reactive power, both achieved by PV systems capable to generate reactive power.

Chaotic PSO-Based VAR Control Considering Renewables Using Fast Probabilistic Power Flow

The roles of reactive power control in a distribution system become essential due to the high penetration of distributed generations (DG) these days. Proper reactive power control can reduce real power losses and regulate the voltage profile in a power system. However, intermittent characteristics of DGs (e.g., renewable energies from wind and solar power) impose uncertainty on power generation in the power system. Therefore, this paper presents a novel fast probabilistic power-flow (FPPF) method based on the Gram-Charlier series expansion to deal with such uncertainty. The FPPF method only deals with stochastic variations of random variables with respect to the expected values, thus reducing the number of iterations. Moreover, the chaotic particle swarm optimization is used to adjust generator voltages, transformer taps, and static compensators to minimize the real power losses while the stochastic voltages satisfy the operational limits. Applicability of the proposed method is verified through simulation using an autonomous 25-bus (Penghu) system and the IEEE 118-bus system. Comparative studies considering traditional probabilistic power-flow methods are performed as well.

Thermal Behavior Optimization in Multi-MW Wind Power Converter by Reactive Power Circulation

The influence of actively controlled reactive power on the thermal behavior of a multimegawatt wind power converter with a doubly fed induction generator is investigated. First, the allowable range of internal reactive power circulation is mapped depending on the dc-link voltage and the induction generator and power device capacity. Then, the effects of reactive power circulation on current characteristic and thermal distribution of the two-level back-to-back power converter are analyzed and compared. Finally, the thermal-oriented reactive power control method is introduced to the system for the conditions of constant wind speed and during wind gust. It is concluded that the thermal performance will be improved by injecting proper reactive power circulation within the wind turbine system, thereby being able to reduce the thermal cycling and enhance the reliability of the power converter.

Mitigation of Voltage sag and Harmonics in Grid connected Wind Energy System using STATCOM

Power quality gains its importance with the introduction of sophisticated electrical gadgets. The performances of these devices are sensitive to the quality of input power supply. Various power quality problems results in failure or mal-operation of end user equipment. Some of the major power quality issues are voltage sag, voltage swell and harmonics. To solve these problems, capacitors, voltage regulators and filters, are conventionally used. These techniques involve inherent drawbacks. So it is proposed to use Flexible AC Transmission System (FACTS) devices for the mitigation of power quality problems. With the usage of these devices, drawbacks associated with conventional methods can be overcome easily. The application of FACTS devices provides faster control and enhances the way of using the transmission system at their rated thermal capability. In this work, it is proposed to use Static Var Compensator (STATCOM) for mitigating voltage sag and harmonics by providing proper reactive power support. The device is modelled and simulated using MATLAB-SIMULINK. In order to validate the proposed approach, it is tested with three phase fault simulated in the designed model. The graphical, numerical results with and without STATCOM are compared to measure the effectiveness of control.

Beta (phase constant) compensation for flat voltage profile in a transmission line

The reliability of the bulk electric power systems is not only dependent on the generation but also on the transmission system. In long lines, the voltage along the transmission line varies with the loading conditions. Proper reactive power compensation helps to maintain the voltage along the line within acceptable limits. This paper proposes a compensation method to adjust the phase constant of the transmission line in order to obtain a flat voltage profile along the line. Case studies conducted on a long transmission line are presented.