Utility Interface Research Articles

Multiport Converter Utility Interface with a High-Frequency Link for Interfacing Clean Energy Sources (PV\Wind\Fuel Cell) and Battery to the Power System: Application of the HHA Algorithm

The integration of clean energy sources (CESs) into modern power systems has been studied using various power converter topologies. The challenges of integrating various CESs are facilitated by the proper design of multi-port power converter (MPPC) architecture. In this study, a brand-new two-stage MPPC is suggested as a solution to the intermittent nature and slow response (SR) of CESs. The suggested system combines a DC\DC and a DC\AC converter and storage unit, and the suggested circuit additionally incorporates a number of CESs (PV\wind\fuel cell (FC)). This article discusses the power management and control technique for an integrated four-port MPPC that links three input ports (PV, wind, and FC), a bidirectional battery port, and an isolated output port. One of the recent optimization techniques (Harris Hawk’s algorithm) is applied to optimize the system’s controller gains. By intelligently combining CESs with complementary characteristics, the adverse effects of intermittency are significantly mitigated, leading to an overall enhancement in system resilience and efficiency. Furthermore, integrating CESs with storage units not only addresses SR challenges but also effectively combats intermittent energy supply. The proposed system exhibits improved dynamic capabilities, allowing it to efficiently distribute excess energy to the load or absorb surplus energy from external sources. This dual functionality not only optimizes system operation but also contributes to a reduction in system size and cost, concurrently enhancing reliability. A comprehensive investigation into operational principles and meticulous design considerations are provided, elucidating the intricate mechanics of the suggested MPPC system. Employing MATLAB/Simulink, the proposed architecture and its control mechanisms undergo rigorous evaluation, affirming the feasibility and efficacy of this innovative system.

The Usability of Management Information Systems Applications

Many management information systems applications can be used to support businesses. One example is platforms that support electronic commerce, so retailers can sell products and services online. The use of electronic commerce applications is so common that virtually every smartphone owner has used them. In this research, the author evaluates the usability of mobile applications for electronic commerce in the Kingdom of Saudi Arabia and introduces a measure with which developers and organizations can evaluate the usability of their mobile applications. Applying quantitative research methods, including structural equation modeling, the research shows that three constructs—application design, application utility, and user interface structure—are the strongest predictors of both continued intention to use a mobile application and loyalty to the mobile application.

Design and Analysis of Novel Three-Phase PFC for IM Drives

Induction motor drives (IMDs) can achieve high performance levels comparable to dc motor drives. A major problem in getting high dynamic performance in an IMD is the coupling between the flux and torque producing components of stator current. This is successfully overcome in FOC (Field-Oriented Control) IM, making it to the industry standard control. The performance of an IMD with an improved power quality converter at the front end is presented in this study. In the IMD, boost converter is employed to reduce power quality difficulties at the utility interface. As the boost converter contains only one switch, it results in a low processing time and cost. To ensure sinusoidal supply currents with high PF (Power Factor) and minimal THD (Total Harmonic Distortion), a novel PFC (Power Factor Corrector) control technique is proposed. To enhance the performance of the converter and to lower distortions at the motor side, PI (Proportional Integral) controller is incorporated at the PFC side. Thus it controls the DC bus voltage. The proposed boost converter improves power quality by lowering overall harmonic distortion of AC mains current, improving power factor correction, and regulating dc-link voltage. It is designed, modelled, and simulated in the MATLAB/simulink platform. Using a DSP (Digital Signal Processor), the suggested system’s performance is experimentally validated. The system’s performance is evaluated for speed and load torque, and the power quality indices are determined to meet IEEE-519 standards under all operating conditions. From the obtained results, it is evident that the proposed system mitigates the power quality issues effectively.

Power Flow Numerical Assessment of a STATCOM iUPQC Utility Interface for Microgrids

The dual unified power quality conditioner (iUPQC) is an active filter that has been studied to be applied as utility interface in microgrid applications. It regulates the voltage of the microgrid side and controls the power flow between the grid and microgrid side. Besides that, ancillary functions to grid side has been proposed to extend its power quality compensation. This paper presents a detailed analytical and numerical analysis of the power flow of an iUPQC, which operates as an utility interface in microgrid applications with the extended function of STATCOM. It can compensate not only the disturbances at the load or microgrid side but also provides a RMS voltage regulation at the Point of Common Coupling (PCC), thus, providing reactive power to the grid. Moreover, the iUPQC power flow is evaluated considering the implementation of the power angle control (PAC), a technique used to share and equalize the power processed by each converter allowing the optimization of this conditioner. Therefore, this study can support the understanding of the power flow of the iUPQC operating as STATCOM, in order to share and optimize the available power in the iUPQC converters using PAC.

Optimal allocation of renewable distributed generators and shunt capacitors in distribution system using hybrid intelligent approach

Increased utilisation of naturally available energy sources in a distribution system (DS) is customary in recent years. These RES are intermittent in nature and impact the system performance significantly. In this paper, a methodology is utilised for bidding the lowest price to the consumer based on the availability of RES. A physical communication infrastructure between the utility and user is enabled to coordinate between the RES dominant utility and consumers. The main objectives of this communication enabled user utility interface system are to minimise power loss and enhance the voltage profile simultaneously. A multi-objective approach considering active power loss index (ALPI), voltage deviation index (VDI), and voltage stability index (VSI) are presented to solve the renewable distributed generation (RDG) and shunt capacitors (SCs) allocation problem. A combination of sensitivity analysis and random walk moth flame optimisation (RWMFO) is utilised for solving the aforementioned multi-objective function. IEEE 33 and 69 bus test systems are taken for analysis. Finally, the implemented method is compared with recent techniques available in the literature.

Model-Free Energy Management System for Hybrid Alternating Current/Direct Current Microgrids

A hybrid ac/dc microgrid combines the benefits of ac and dc power systems. It provides high efficiency and is compatible with conventional ac distribution network. This article proposes a centralized energy management approach to perform coordinated control on a hybrid ac/dc microgrid as a single-controllable entity. The central controller relies on low-bandwidth communication channels and is aimed at achieving 1) proportional power sharing among energy storage units located in both dc and ac sides of the microgrid, 2) state-of-charge equalization of the energy storage units, 3) grid power flow control, 4) plug-and-play capability, and 5) operation in grid-connected and islanded modes through an interlinking utility interface converter. The state-of-charge equalization method guarantees uniform operation of the energy storage units during both charge and discharge modes considering typical operational transients. Finally, the proposed model-free approach is evaluated experimentally through a laboratory-scale hybrid ac/dc microgrid in different operational conditions in both grid-connected and islanded operating modes.

Integrated Informatics Analysis of Cancer-Related Variants.

PURPOSEThe modern researcher is confronted with hundreds of published methods to interpret genetic variants. There are databases of genes and variants, phenotype-genotype relationships, algorithms that score and rank genes, and in silico variant effect prediction tools. Because variant prioritization is a multifactorial problem, a welcome development in the field has been the emergence of decision support frameworks, which make it easier to integrate multiple resources in an interactive environment. Current decision support frameworks are typically limited by closed proprietary architectures, access to a restricted set of tools, lack of customizability, Web dependencies that expose protected data, or limited scalability.METHODSWe present the Open Custom Ranked Analysis of Variants Toolkit1 (OpenCRAVAT) a new open-source, scalable decision support system for variant and gene prioritization. We have designed the resource catalog to be open and modular to maximize community and developer involvement, and as a result, the catalog is being actively developed and growing every month. Resources made available via the store are well suited for analysis of cancer, as well as Mendelian and complex diseases.RESULTSOpenCRAVAT offers both command-line utility and dynamic graphical user interface, allowing users to install with a single command, easily download tools from an extensive resource catalog, create customized pipelines, and explore results in a richly detailed viewing environment. We present several case studies to illustrate the design of custom workflows to prioritize genes and variants.CONCLUSIONOpenCRAVAT is distinguished from similar tools by its capabilities to access and integrate an unprecedented amount of diverse data resources and computational prediction methods, which span germline, somatic, common, rare, coding, and noncoding variants.

Optimal Multiobjective Control of Low-Voltage AC Microgrids: Power Flow Regulation and Compensation of Reactive Power and Unbalance

The presence of single-phase distributed generators unevenly injecting active power in three-phase microgrids may create undesired upstream current unbalance. Consequently, voltage asymmetry and even active power curtailment may occur in such networks with negative economic impact. Thus, this paper proposes an optimal multiobjective approach to regulate the active and reactive power delivered by distributed generators driven by a three-layer hierarchical control technique in low-voltage microgrids. This method does not require previous knowledge of network parameters. The multiobjective algorithm is implemented in the secondary level achieving optimal dispatch in terms of maximizing the active power generation, as well as minimizing the reactive power circulation and current unbalance. By the existence of a utility interface three-phase converter placed at the point-of-common-coupling, the proposed control can regulate the power circulating among the microgrid phases, and the microgrid structure can withstand grid-connected and islanded operating modes. The path for interphase power circulation through the DC-link of the utility interface allows the multiobjective algorithm to achieve better results in terms of generation and compensation compared to the system without utility interface. The proposed method is assessed herein by computational simulations in a three-phase four-wire microgrid under realistic operational conditions.

PLL-Based Feed-Forward Control to Attenuate Low-Frequency Common-Mode Voltages in Transformerless LVDC Systems

Low-voltage dc distribution systems have gained significant attention over the last years, since they provide simpler and more efficient integration of distributed generators and storage devices, establishing a pathway to net zero energy buildings. In low-power units, transformerless utility interface is preferred to reduce footprint and losses. However, the lack of galvanic isolation introduces a common-mode (CM) path between the dc distribution bus and the utility service grounding, leading to the presence of high CM voltages at the dc bus feeders. The attenuation of the CM voltage reduces the touch voltage amplitude and leakage current, contributing to a safer environment. In this paper, a feed-forward active compensation of the CM voltage is proposed. It relies on utility voltage parameters, estimated by a phase locked loop, to generate a counter CM voltage; hence, it does not require previous knowledge of the system CM path model or the addition of voltage sensors. Experimental results show that this technique can attenuate the CM voltage to non-dangerous magnitudes without interfering with the microgrid differential mode behavior.

Analysis and Experimental Characterization of a Large-Bandwidth Triple-Loop Controller for Grid-Tied Inverters

This paper analyzes a large-bandwidth, triple-loop controller designed for single-phase, grid-tied, and voltage–source inverters with LCL output filter. The inner control loops regulate the inverter output current and the filter capacitor voltage, respectively, while the third, outer one regulates the current injected into the grid. The inner loops are given deadbeat type regulators, whose minimum response delay allows the third loop to achieve a relatively large regulation bandwidth. This organization provides several benefits, including a regulated local ac voltage, a large-bandwidth control of the power flowing to the grid, and a good robustness against different types of commonly encountered grid perturbations. In particular, grid voltage harmonic pollution, amplitude, and frequency fluctuations or connection impedance parameter variations can be tolerated without incurring into instability or unacceptable performance degradation. Besides, the proposed controller is inherently able to guarantee seamless transitions between grid-tied and islanded operation, showing good potential for application to nano- and microgrid utility interface converters.

Robust Microgrid Clustering in a Distribution System With Inverter-Based DERs

Power electronics for the utility interface of distributed energy resource (DER) offers many benefits in the electric grid operation through flexibility of the DER controls. Energy from various generation sources including renewables can be efficiently delivered to the consumers with high power quality and reliability. However, mixed source microgrids comprising both inverter- and synchronous generator-based DERs are susceptible to collapse, particularly when the system operates in the islanded mode. This paper presents robustness studies on microgrids from a qualitative point of view, borrowing features from ecological systems that are highly robust. The interrelationships between ecological species translate into the dynamic behavior of DERs, affected by their sizes and locations within the grid. The advantage of such qualitative analysis over traditional quantitative viewpoint is it explicitly identifies the nature of interactions and interconnections between the subsystems as beneficial or detrimental to stability. From the robustness studies, the best possible microgrid configurations are determined for IEEE 33-bus system having a mix of inverter-based DERs and synchronous generator-based DERs. Furthermore, all possible microgrid cluster formations are studied for finding the most robust microgrid islanding strategies.

A heat integration method with multiple heat exchange interfaces

In recent decades, energy efficiency has become one of the key issues facing large process industries. Mounting economic, environmental and social pressure motivate energy-intensive industries to improve their efficiency. Identifying retrofit opportunities in large-scale problems is extremely complex due to numerous interconnections and dependencies between process units, sub-units and utilities present on most industrial sites. Therefore, when attempting to identify promising retrofit opportunities, methods detecting early design decisions are crucial. Techniques applying heat integration (HI) often use mathematical models and optimization to survey potential solutions. Mixed integer linear programming (MILP) is often used for industrial energy efficiency case studies due to its flexibility, solution speed and guaranteed optimal solution while taking advantage of the extensive bodies of work dedicated to this type of problem. The current work proposes a methodology based on HI and MILP to represent process energy requirements with different heat exchange interfaces. Switching from the current utility interface to an alternative one requires additional heat transfer area while it might bring operational benefits due to better system integration. The optimal combination of the processes with different interfaces is obtained by considering the trade-off between the cost of additional heat exchanger area required and decrease in the operating cost. The proposed method is applied to two industrial case studies which show the added value for HI and impact of the proposed method for reducing the problem size in heat exchanger network (HEN) design. In the first case study, the total cost of the system is reduced by 45% taking into account the cost of the modifications in the existing heat exchangers while in the second case study the computation time of heat load distribution (HLD) is reduced by 78% using the results of optimal interface selection. The proposed method provides early design decisions for retrofit solutions on industrial sites. Utilizing this methodology provides a dual benefit of identifying the most promising options for retrofit applications while also eliminating inconsequential ones at an early stage of the analysis.

Domestic Technical Standards and Performance Test of Photovoltaic PCS for Renewable Energy

This paper describes domestic technical standard of Photovoltaic(PV) PCS(Power Conditioning Systems)-Characteristics of the utility interface. This standard tests utility compatibility and personnel safety and equipment protection of PV inverter performance functions. Especially utility compatibilit...

Utility Direct Interfaced Charger/Discharger Employing Unified Voltage Balance Control for Cascaded H-Bridge Units and Decentralized Control for CF-DAB Modules

A bidirectional high-frequency isolated ac–dc converter for utility direct interfaced electric vehicle charger with vehicle-to-grid (V2G) capability is presented in this paper. This type of charger can achieve the direct utility interface with medium voltage input. It is composed of multilevel cascaded H-bridge ac–dc converter as the first stage and modular current-fed dual active bridge dc–dc converters as the second stage. For the cascaded H-bridge converter, a unified control to balance the cascaded H-bridge dc voltages is proposed for both charging and discharging modes. For the second dc–dc isolation stage, the current-fed dual active bridge converter is used in facing of the wide conversion gain in battery charging application and also to reduce the charging current ripple. Meanwhile, to improve the system flexibility and reliability, decentralized control is utilized for individual current-fed dual active bridge converters in view of the battery charging profile. The proposed method along with the presented topology can achieve voltage balance in spite of the power flow direction, simplification of the controller for the dc–dc modules and can also bear unbalanced power flow. The simulation and experimental results have been presented to show the effectiveness of the proposed control.

A novel current injection device for harmonic reduction of three-phase controlled converters in renewable energy utility interfacing

Three-phase controlled/uncontrolled converters have been used in renewable energy applications such as photovoltaic and wind energy as rectifiers and inverters. The main drawback of these converters is the high THD (Total Harmonic Distortion) in their line currents. Many techniques have been used to remedy this problem. Third harmonic current injection is one of the best solutions for the harmonic reduction in line currents of these converters. Injecting third harmonic current from the dc-bus to the line currents reduces its harmonic contents. Minimum THD for any firing angle of the controlled converter is a function of the phase-angle and amplitude of harmonic injection current that can be controlled by a single-phase controlled converter and a boost converter, respectively. This scheme is used with a zigzag transformer to circulate the harmonic injection current to the line currents. A novel mathematical analysis for the proposed scheme and state of the art scheme is introduced. The mathematical analysis introduces the optimum values for components on the harmonic injection path at minimum THD and the corresponding efficiency. The scheme under study has been simulated using the PSIM program. A lab prototype for this scheme has been implemented. Mathematical, simulation, and experimental results for this scheme have been introduced, compared, and discussed. The results show the superiority of the proposed scheme.

Techno-Economic Aspects in Electricity Market Operations with Grid Interfaced Electric Vehicles

The focus of this paper is to explore the oppor- tunities and challenges associated with grid-interfaced electric vehicles in the view of growing electrification of the transporta- tion sector. The study covers the following key concerns, 1) the configuration for electric vehicle (EV) – electric utility interfacing, 2) potentiality of EVs for grid services in competitive market environment, and 3) evaluation of charging/ discharging impacts of a large deployment of EVs on the grid. The study suggests that the three principal participants, the power utilities, the vehicle owners, and the entity called aggregator can proactively work together to better manage the charging demand by the EVs, preventing the negative impacts caused by the uncontrolled charging. Simulative analyses are also presented to highlight the impact of grid-to-vehicle (G2V) and vehicle-to-grid (V2G) on the demand profile and electricity market price. The development of G2V/V2G profiles for grid services would require taking into consideration the vehicles’ heterogeneity which is dependent upon mobility behavior. The prospect of drawing revenue by offering energy and capacity services through V2G in volatile ancillary services market can also offset the barrier of expensiveness in their adoption, in addition to improving the grid reliability.

Autoinspection and Permitting With a PV Utility Interface (PUI) for Residential Plug-and-Play Solar Photovoltaic Unit

Renewable energy resources are becoming popular with mass adoption in residential and commercial applications because of gradual cost reduction along with continuous technical advancements. Photovoltaic (PV) energy is one of the biggest players of renewable energy installations although soft costs remain as the major barrier for higher penetration of PV systems. To address the cost challenges, a plug-and-play (PnP) system for a quick, low-cost installation is proposed and designed. The method is much less invasive and labor intensive than the traditional installation methods. This paper presents the PnP electrical system, with emphasis on the controls, software, and system-level communications within the system. A PV utility interface circuit has been developed for automated electrical safety checks and authentication for the PnP PV system. A data protocol has been used to deal with the master–slave controller setup in the system. This research has the potential to reduce the residential PV system price by $0.6/W.

Improved Power Quality Bridgeless Converter-Based SMPS for Arc Welding

This paper proposes a power-factor-corrected bridgeless (BL) switched-mode power supply (SMPS) for welding applications that possesses output voltage control and current limiting feature even during extreme overloading conditions at the output terminals. Eliminating an input diode bridge rectifier minimizes conduction losses and improves thermal utilization of semiconductor devices. The front-end of the proposed SMPS consists of a BL boost converter operating in a continuous conduction mode to attain unity power factor, while at the rear end a pulse width modulation isolated full bridge dc–dc converter is used to regulate the output voltage. The design and implementation of this BL arc welding power supply (AWPS) is presented showing its fast dynamic response to supply voltage and load variations. The performance of the proposed AWPS is examined in terms of power factor, total harmonic distortion of the supply current, efficiency, and output current limit over a wide range of line/load variations. Test results confirm the effectiveness of the proposed AWPS in maintaining an impeccable power quality at utility interface apart from achieving an excellent output voltage regulation and current limiting capability.

Sliding Mode Fixed Frequency Current Controller Design for Grid-Connected NPC Inverter

In this paper, a fixed-frequency pulsewidth modulation (PWM) based on sliding-mode current controller is designed and applied to a utility interface three-phase/wire/level neutral-point-clamped inverter. The proposed design methodology of the sliding-mode control is based on a constant switching frequency operation and on Gao’s reaching law that allows chattering compensation. The aim of the controller is to inject a controlled active power from renewable energy sources into the grid while controlling the power factor and minimizing supply current harmonics. Moreover, the dc-link voltages across the split capacitors are controlled with a simple proportional–integral (PI) regulator. Experimental results show the advantages of the proposed control algorithm in terms of fast dynamic response, low voltage ripple on the dc bus, low current Total Harmonic Distortion, and robustness toward external perturbations from the dc and ac sides; moreover, a comparison with a PWM–PI current controller is presented.

Design, Simulation and Implementation of Current Fed Isolated Full Bridge DC-DC with Voltage Multiplier for Fuel Cell Grid Applications

Abstract This paper proposes novel current fed converter full bridge isolated DC-DC converter with voltage multiplier and active clamp circuit for fuel cell grid connected applications. The proposed converter is best suited for fuel cells and their interfacing to utility three phase grid. Active clamp concept introduced on the primary side of isolation transformer to reduce the turn-off voltage spikes of full bridge active devices. Innate soft-switching with elongated range can be achieved in the recommended converter by using the parasitic capacitance of MOSFET switches and leakage inductance of the high frequency transformer. Zero Voltage Switching(ZVS) is achieved for all the primary devices which allow greater switching frequency operation and improvement in over-all efficiency of the converter for utility interface. Cost, size and weight of the converter minimizes for the higher switching operation of the converter. Half-wave Cockcroft-Walton Voltage Multiplier (H-W C-W VM) having minimum number of multiplying stages is used on the secondary side of the designed converter in order toget the required DC-link voltage for three phase utility grid connection. The converter's switching frequency is maintained at 100 KHz. This paper is organized as introduction, steady state operation, simulation results with two different cases i.e. full load and half load conditions and finally, test result validation of a 250 Watt experimental setup with the proposed converter.