Load Reactive Power Research Articles

Design an Accurate Power Control Strategy of Parallel Connected Inverters in Islanded Microgrids

When the overall loads change periodically, the accurate real power and reactive power sharing considered is essential for the operation of an islanded microgrid. In this work, an accurate power control strategy of parallel-connected inverters in an AC microgrid in islanded mode has been designed. The examined microgrid involves four inverters linked to the load via different system impedance conditions is performed. Also, the control strategy for islanded microgrid operation with detailed switching models is simulated by using PSCAD/EMTDC software, and all dynamic and steady-state real and reactive power sharing is explained. Moreover, the real power sharing is achieved using only the decentralized control (droop control), while the reactive power sharing control approach is proposed as a central controller (secondary controller) in order to improve the precision of fundamental reactive power sharing, gives an efficient dynamic performance, and reduce the circulating current. The central controller in the microgrid requires communications. It is used as an external loop to accomplish identical reactive power sharing according to reactive power load especially when the mismatch in voltage drops through the feeders is occurred. The control approach will still work with traditional droop control when the central controller is a failure. The obtained results show that the proposed approach is immune to the time delay in the central controller. Additionally, the active power and the reactive power is shared accurately.

Adaptive robust energy management for isolated microgrids considering reactive power capabilities of distributed energy resources and reactive power costs

This paper presents an adaptive robust Energy Management (EM) model for an isolated Microgrid (MG) to decide for the day-ahead optimal dispatch to effectively manage the MG power sources considering uncertainties in Renewable Energy Sources (RESs). The aim of this model is to minimize the operation costs, reactive power costs, spinning reserve and load shedding. Usually, fuel consumption costs of diesel generators are considered to be dependent on active power generation only. However, neglecting the related reactive power costs might result in increased operation costs and deviations from optimal dispatches. Hence, this paper optimizes the costs related to both active and reactive powers of diesel generators. Furthermore, simultaneous active/reactive power dispatch can lead to accurate operation decisions compared to separate dispatch for active or reactive power alone. In addition, this study considers the reactive power capability of inverter-interfaced Distributed Energy Resources (DERs) so that reactive powers can be supplied from inverter-interfaced DERs. Moreover, detailed models for the different resources are presented, especially for diesel generators and inverter interfaced DERs where actual capability curves are used instead of the widely used box constraints. The problem is formulated as nonlinear programming problem using GAMS program and solved by the CONOPT solver.

Multi‐functional commercial solar photovoltaic plant integrated to three‐phase low voltage AC network

This study presents the commercial solar PV plant (SPVP) operation, integrated into the low voltage (LV) AC network. The SPVP has the multi-functional operational capability. It feeds the PV array generated power to loads and the AC network, while ensuring the power quality improvement at the point of common coupling (PCC) as per the IEEE std. 519, irrespective of the load characteristic (linear/nonlinear and balanced/unbalanced). The SPVP minimises the line losses in the AC network by recouping the load reactive power requirement locally. Moreover, the SPVP operates in either maximum power extraction (MPE) mode or constant power generation (CPG) mode, depending upon the rise in PCC voltage amplitude during the peak PV array power generation and low load demand condition. The SPVP switches between the MPE and the CPG modes during the high rise in PCC voltage amplitude and regulates the PV array generated power to protect itself and the load connected at PCC. In this study, an adaptive filter technique based on maximum correntropy criterion is used for the PQI, and the perturb and observe based algorithm is used for MPE. A simulation model and reduced rating hardware prototype are developed to validate the system's performance.

Reactive Power Control and Neutral Current Elimination of Four Wire Five Level NPC Inverter based STATCOM using 3D-SVPWM Technique

In this paper, three phase four wire five level Neutral Point Clamped Inverter (NPCI) based Static synchronous Compensator (STATCOM) is implemented for reactive power control and neutral current elimination. Three dimensional Space Vector Pulse Width Modulation (3D-SVPWM) control strategy is developed to control this 5-level NPC inverter. The behaviour of static synchronous compensator is analyzed and reactive power control is done using constant DC voltage. The objective of this compensating method is to provide balanced and sinusoidal source currents under unbalanced and nonlinear load conditions and reactive power control. The 3D-SVPWM technique provides reduced harmonic content in output voltage and current, controlled source current, minimized common mode voltage and improved output voltage. In 3D-SVPWM, switching pulses are generated with non-redundant switching states, which lead to reduce the complexity in switching time calculation and computational time is less. The highlights of the paper includes the neutral current is reduced to 0.25A, source current harmonics is minimized and it provides balanced and sinusoidal source currents with help of STATCOM compensation. The simulation and experimental results demonstrates the sinusoidal and harmonics free source current and minimized neutral current for four wire five level NPCI based STATCOM.

Hysteresis Controlled Based Power Quality Improvement in a Renewable Energy Source Connected to Utility grid with BESS Based STATCOM

This Paper presents a control strategy of the grid interconnected inverter Renewable Energy Sources (RES). This system can achieve the maximum benefits from these grid interconnected inverter when installed in 3-phase 4-wire distribution system. Increasing electrification of daily life causes growing electricity consumption and the rising number of sensitive or critical loads demand for high quality electricity. One of the main problems facing today is that related with the transmission and distribution of electricity. Due to the rapid increase in global energy consumption and the diminishing of fossil fuels, the customer demand for new generation capacities and efficient energy production, delivery and utilization keeps rising. Utilizing distributed generation, renewable energy and energy storage can potentially solve problems as energy shortage. With the increase in load demand, the Renewable Energy Sources (RES) are increasingly connected in the distribution systems which utilizes power electronic Converters/Inverters. The inverter can perform as a multi function device by incorporating active power filter functionality. The inverter can thus be utilized as: 1) power converter to inject power generated from RES to the grid, and 2) shunt APF to compensate current unbalance, load current harmonics, load reactive power demand and load neutral current. All of these functions may be accomplished either individually or simultaneously. This new control concept is demonstrated with extensive MATLAB/Simulink simulation studies and validated through digital signal processor-based laboratory experimental results.

Voltage stability assessment of isolated hybrid dish-stirling solar thermal-diesel microgrid with STATCOM using mine blast algorithm

This paper presents the voltage control of an isolated hybrid diesel-dish-Stirling solar thermal system (DSP) based power system. As DSP is employed with an induction generator (IG), it needs reactive power for magnetic field. Though synchronous generator (SG) is coupled with the diesel generator, SG alone unable to supply sufficient reactive power to cater the reactive power requirement of the consumers load and the IG. Under such circumstances, static synchronous compensator (STATCOM) is used to meet the reactive power demand. The parameters of the controllers employed with the STATCOM as well as automatic voltage regulator (AVR) of the SG are tuned simultaneously applying recently developed mine blast algorithm (MBA). Performance of the MBA based controllers are compared with that of the cuckoo search algorithm (CS), and particle swarm optimization (PSO) based counterpart on the proposed model. Application of STATCOM and MBA based control strategy in diesel-dish-Stirling solar thermal system-based hybrid system for reactive power regulation is a maiden attempt. Extensive simulations of the model for dynamic responses of voltage deviations and reactive deviations under several uncertain conditions, such as step disturbance in reactive power load of the consumers and IG without/ with STATCOM, realistic variations of power output of DSP and reactive load have been carried out. Results analyses indicate that MBA based control strategy is the best amongst all the control strategies attempted here in the terms of maximum overshoot and the settling time. Further, meager values of the maximum overshoot and the settling time under several uncertain conditions justify the coordinated control of AVR and STATCOM to maintain the voltage stability of the isolated hybrid system.

A New Adaptive Broadband Thyristor-Controlled Impedance Matching Network

In this article, we present an adaptive broadband thyristor-controlled impedance matching network (TCIMN) for increasing power utilization from a power amplifier to the loads. Different from the conventional passive impedance matching methods, the proposed one can achieve load impedance matching under a wide frequency range of power amplifiers. First, the operation principle of TCIMN is introduced mathematically. Based on that, the parameter design method is proposed based on the required frequency range. Moreover, the operating range and harmonic analyses are provided to give the TCIMN firing angle operating ranges under different frequencies and alleviate the potential harmonic problem caused by thyristors. To control the proposed TCIMN, the dynamic impedance identification is applied to match the load reactive power adaptively. Finally, the simulation and experimental results of a prototype are given to demonstrate the validity of the proposed TCIMN, analysis, and control method. The results clearly show that the proposed TCIMN can adaptively match the load impedance for the different loads and broadband frequency range. More importantly, the power amplifier power utilization factor is significantly improved without causing harmonic pollutions.

Nyström Minimum Kernel Risk-Sensitive Loss Based Seamless Control of Grid-Tied PV-Hybrid Energy Storage System

This paper presents Nyström minimum kernel risk-sensitive loss (NysMKRSL) based control of a three-phase four-wire grid-tied dual-stage PV-hybrid energy storage system, under varying conditions such as irradiation variation, unbalanced load, and abnormal grid voltage. The Voltage Source Converter (VSC) control enables the system to perform multifunctional operations such as reactive power compensation, load balancing, power balancing, and harmonics elimination while maintaining Unity Power Factor (UPF). The proposed VSC control delivers more accurate weights with fewer oscillations, hence reducing overall losses and providing better stability to the system. The seamless control with the Hybrid Energy Storage System (HESS) facilitates the system’s grid-tied and isolated operation. The HESS includes the battery, fuel cell, and ultra-capacitor to accomplish the peak shaving, managing the disturbances of sudden and prolonged nature occurring due to load unbalancing and abnormal grid voltage. The DC link voltage is regulated by tuning the PI controller gains utilizing the Salp Swarm Optimization (SSO) algorithm to stabilize the system with minimum deviation from the reference voltage, during various simulated dynamic conditions. The optimized DC bus control generates the accurate loss component of current, which further enhances the performance of the proposed VSC control. The presented system was simulated in the MATLAB 2016a environment and performed satisfactorily as per IEEE 519 standards.

Grid Synchronization and Islanding Detection Control Algorithm for Two-stage Three-phase SPV System

ABSTRACT Integration of distributed energy sources (DER) with the conventional grid through power electronic interface has emerged as a boon for reliable and good quality power to end-users. The existing control algorithms for the power electronic interface are normally feedback algorithms which help in grid synchronization and effective power dispatch. In this work, an adaptive feedforward-feedback control algorithm is proposed for optimal solar power management of two-stage three-phase grid-integrated solar photovoltaic (SPV) system. Proposed control algorithm enables feeding of SPV energy to load and into the grid, and also act to balance grid currents, compensates reactive power, eliminates harmonics and protect load and source during adverse islanding condition. Phase-locked loop (PLL) used in the feedback part of the algorithm facilitates the effective synchronization of the SPV system. Asymmetric fuzzy logic control (FLC) is used for DC-link voltage stabilization during load variation. Feedforward algorithm ensures fast dynamic response for variable atmospheric and grid operating conditions. Moreover, for protection of SPV arrays and the loads coupled at point of common coupling (PCC), islanding detection followed by interfacing inverter shutdown feature is added in the proposed algorithm. Quantitative analysis of the system is provided in order to investigate the effectiveness of the proposed algorithm. The effectiveness of the algorithm is evaluated using simulation studies performed on MATLAB/ Simulink software.

Grid Integration of Renewable Energy Sources using GA Technique for Improving Power Quality

Hybrid Renewable energy sources (HRES) are rapidly increasingly compared to the traditional system since they are less effective to the environment and meet the huge demand required by the utilities. In the proposed paper the modelling, control and design analysis is implemented with PV, wind and battery as an energy storing device. The grid-interfacing inverter is regulated with a single-stage, three-phase RES-based distributed generation (DG) system. A genetic algorithm (GA) based shunt active power filter (SHAPF) is used to mitigate the power quality issues under nonlinear and unbalanced load conditions. The DG is grid-connected through a current-controlled –voltage source inverter (CC-VSI) via a DC link capacitor. Here the VSI is utilized to transfer the power from DG to the point of common coupling (PCC), SAPF to compensate for load current harmonics, under distorted supply voltage conditions, reactive power demand and load current imbalance. Both of these functions are important either individually or concurrently. As a result, the proposed controller regulates the power flow, controls it and acts as a SHAPF or does both at the same time. The proposed method is employed in the MATLAB/Simulink platform and performances were analysed.

Data Driven Stochastic Energy Management for Isolated Microgrids Based on Generative Adversarial Networks Considering Reactive Power Capabilities of Distributed Energy Resources and Reactive Power Costs

This paper proposes a two-stage stochastic energy management (EM) in an isolated microgrid (MG) to decide for the day-ahead optimal dispatch. The dispatch aims to effectively manage the MG power sources, including intermittent renewable energy sources (RESs), battery energy storage systems (BESSs), and diesel generators such that the expected operation costs, reactive power costs, spinning reserve, and load shedding are minimized. The Generative Adversarial Networks (GANs) is utilized in this paper as a data driven scenario generation method to model the uncertainties in the output power of the RESs to be used in the stochastic programming formulation. Then, the fast forward scenario reduction algorithm is used to reduce the number of scenarios with the help of SCENRED/GAMS software. Usually, fuel consumption costs of diesel generators are considered to be dependent on active power generation only. However, neglecting the related reactive power costs might result in increased operation costs and deviations in the dispatches from the optimal solutions. Hence, this paper co-optimizes the costs related to both active and reactive powers of diesel generators. In addition, this study considers the reactive power capability of inverter-interfaced distributed energy resources (DERs). Moreover, the detailed models for the different resources are presented, especially for diesel generators where the actual capability curves are used instead of the widely used box constraints. The problem is formulated as a nonlinear programming problem in the General Algebraic Modeling System (GAMS) software and is solved by the CONOPT solver.

Real-Time Operation of Microgrids

Microgrid (MG) systems effectively integrate a generation mix of solar, wind, and other renewable energy resources. The intermittent nature of renewable resources and the unpredictable weather conditions contribute largely to the unreliability of microgrid real-time operation. This paper investigates the behavior of microgrid for different intermittent scenarios of photovoltaic generation in real-time. Reactive power coordination control and load shedding mechanisms are used for reliable operation and are implemented using OPAL-RT simulator integrated with Matlab. In an islanded MG, load shedding can be an effective mechanism to maintain generation-load balance. The microgrid of the German Jordanian University (GJU) is used for illustration. The results show that reactive power coordination control not only stabilizes the MG operation in real-time but also reduces power losses on transmission lines. The results also show that the power losses at some substations are reduced by a range of 6% - 9.8%.

Control of Digitalized Distribution Electric Network According to the Criterion of Minimum Loss of Electric Power Transmission

At present, the world energy industry is focused on creating intelligent distribution electric networks with management on the energy Internet platform. To solve this problem, a model circuit of an intelligent distribution radial electric network was developed, for controlling parameters in normal and post-accident modes of which, it is proposed to use regulators of transformation coefficients of network transformers and fastacting compensating devices for smooth control of reactive load power. Mathematical model of proposed network and target function are formed, minimization of which ensures minimum losses of electric power transport. Algorithms for control of parameters of operating modes in normal and post-accident modes have been developed. The implementation of the proposed algorithms ensures the operation of the network with minimal losses of electricity transport

The power quality measurements and real time monitoring in distribution feeders

Power quality (PQ) is a measure of the electrical system or electrical grid to deliver “clean” and stable electrical power. Due to the increase in demand of energy per capita day by day, the loads that cause instabilities on the utility grid, subsequent deviation in the current and voltage. Mainly the industries are suffering from poor PQ which consequences not only increasing the energy demand and it is also reduce the production. These are the methods and equipment’s are used for the power quality measurements. When the industries operating with high power equipment, the PQ disturbances such as voltage and current harmonics, switching transients and RMS magnitude variations levels are very high. These are highly affecting the power factor (P.F) of the system and load reactive power consumption increased increases which leads the high power losses. In this paper, the method of PQ disturbances measurements has been proposed at different load condition at the different times during at point of common coupling (PCC). Numerous studies have conducted about to investigated PQ examinations. Nevertheless, the reported PQ studies explorations are done in simulation level. Therefore, the proposes the real time PQ study at distribution feeders PCC point using power quality analyzer and reports the materialized producers of time based measurements. This examination produce will be a valuable guide for electrical engineers, and explore the prospects accessible by proposed methods for additional enhancement PQ trouble shooting in order to analyses and solve serious PQ problem. This paper provides an experimental approach of PQ real-time measurements in distribution Feeders using PQ analyzer. The study is conducted high-rated and low- rated electric machinery at the different feeders PCC level points for and provides the PQ problem optimize method with respect to events. This comprehensive PQ method can be exercise for grid PQ towards to locate the methods for the each optimization individual PQ problems.

DG Allocation in Distribution Networks with Considering of Voltage Stability Improvement and Loss Reduction

The improvement of the line Load-ability (LL) for voltage stability establishes the main criterion for distribution networks. The Distributed Generation (DG) resources play an important role in the supply of active and reactive power loads, bus voltage profiles, and voltage stability in distribution systems. In this paper, a new technique has been proposed for optimization of the location placement and sizing of DGs, considering the Generalized voltage Stability Index (GSI) to determine the maximum load-ability. Also, an analytical method has been applied to infer the effects of DGs on the distribution systems’ characteristics. The study also considers three types of DG modes, which are voltage control mode (PV mode), constant power mode (PQ mode), and also voltage control mode with reactive power constraint (PV mode with VAR constraint). The proposed method is applied to 12-bus, modified 12-bus, 69-bus and 94-bus radial distribution systems.

Single‐phase wind‐BES microgrid with seamless transition capability

A new control strategy for a wind-BES (battery energy storage) microgrid is presented, which controls the power transfer and the mode of operation seamlessly from an islanded mode (IM) to the grid connected mode (GCM) and vice versa. In GCM, the DC link voltage regulation, the load reactive power compensation and harmonics current mitigation are performed by the load side voltage source converter (LVSC) using a double sinusoidal signal integrator (DSSI) based control algorithm. The maximum power from the wind generation is extracted by operating the generator side voltage source converter (GSC). At the grid fault or grid disturbances, this microgrid operates in IM and LVSC is controlled in the voltage control mode. A synchronizing controller is utilized to control the operation of synchronization. The grid current and point of common coupling (PCC) voltage distortions are kept within the limit as per the IEEE-519-2014 and the IEEE-1547 standards. The system operation is demonstrated through test results at several conditions such as, changing wind speeds, varying loads and seamless transition.

Reactive Power Control Strategy of Demand Side Back-to-Back Converter Based on VSM

Background: The Demand Side Management (DSM) technology is playing an increasingly important role in the power system, in order to promote the real-time supply and demand balance of the power grid and improve the economy and safety of the power grid. Objective: To realize the flexible and continuous reactive power control of demand side load, a reactive power control strategy for the demand side back-to-back converter (DS-B2BC) is proposed. Methods: First, DS-B2BC is proposed. Then, the reactive power control model of DS-B2BC and its control loop are designed, and the reactive power control model, based on the Virtual Synchronous Motor (VSM), is established. Results: The simulation results verify that the reactive power control strategy proposed in this paper is effective, which can control the demand side load reactive power flexibly and continuously. Conclusion: Moreover, the strategy can counteract the disturbance from the power grid simultaneously.

A detailed power flow analysis of the dual unified power quality conditioner (iUPQC) using power angle control (PAC)

In this paper, a detailed mathematical analysis of the power flow through the two converters of the Unified Power Quality Conditioner (UPQC) using its dual control strategy (iUPQC) is developed. Unlike previous power flow analyses, the proposed approach considers the power processed due to load current harmonics and grid voltage related problems, such as harmonic distortion, unbalance and fundamental frequency long-duration disturbances. Such analysis considers the unified conditioner under its conventional operation and with the implementation of the power angle control (PAC), which usually provides load reactive power demand sharing between the converters. The presented power flow analysis results in a better understanding on how the PAC can be used to equalize the powers processed by each of the iUPQC converters under general abnormal conditions. Besides, it contributes to clarify how such control can be used to provide active power cancelation or loss reduction. Finally, a three-phase four-wire prototype of an iUPQC was built to experimentally validate the proposed approach.

Robust Frequency Cascaded Adaptive Complex Filter Control for Grid Interactive PV System

This article deals with a robust frequency cascaded adaptive complex filter (ACF) control for the grid interactive photovoltaic (PV) system. The incorporated control algorithm rejects lower order harmonics too unlike the conventional quadrature signal generators; thus, this control algorithm extracts accurate fundamental frequency orthogonal components of load current. The voltage source converter (VSC) acts as a distribution static compensator (DSTATCOM) when generation from the PV array is unavailable, besides injecting active power in the distribution network, and reducing reactive power loading on the utility network by mitigating harmonics in presence of generation from the PV array. Thus, the VSC utility is enhanced. This PV system performance is robust against the weak utility grid parameter variation and at load perturbation. The presented algorithm improves transient response at dynamic loading and irradiance change. The harmonic contents in distribution network voltage and utility current are reduced within the IEEE-519 standard.

Development and simulation of the Institute of ionosphere measuring complex energy consumption

The work is devoted to solving an urgent problem - the development of a computer model of the energy consumption system of the Institute of the ionosphere of the National Academy of Sciences and the Ministry of Education and Science of Ukraine in order to solve the problem of increasing the energy efficiency of the measuring complex. The power supply system of the complex is described, a generalized structural diagram of the loads - powerful consumers of electricity is presented. The graphs characterizing the energy consumption of individual powerful loads are presented, the problem of compensating the reactive power of loads is shown. The adequacy of the developed model is confirmed by the coincidence of the shape and values of the experimentally obtained characteristics on loads with the characteristics of the model. The model adequacy was assessed by the variance of feedback deviations from the system mean. The results obtained confirmed the possibility of using the developed Matlab-model of the energy consumption system of the measuring complex for creating and testing on the model of an energy-efficient power supply system, which will ensure the stable operation of scientific equipment for the implementation of research programs of the NAS of Ukraine.