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Showing records 126 to 150 of 710. [First] Page: 2 3 4 5 6 7 8 9 10 Last
Key Operational Issues on the Integration of Large-Scale Solar Power Generation—A Literature Review
Wei Li, Hui Ren, Ping Chen, Yanyang Wang, Hailong Qi
April 4, 2023 (v1)
Keywords: balancing of whole network, electric vehicle charging and discharging station, frequency regulation, PV output forecasting, PV power generation
Solar photovoltaic (PV) power generation has strong intermittency and volatility due to its high dependence on solar radiation and other meteorological factors. Therefore, the negative impact of grid-connected PV on power systems has become one of the constraints in the development of large scale PV systems. Accurate forecasting of solar power generation and flexible planning and operational measures are of great significance to ensure safe, stable, and economical operation of a system with high penetration of solar generation at transmission and distribution levels. In this paper, studies on the following aspects are reviewed: (1) this paper comprehensively expounds the research on forecasting techniques of PV power generation output. (2) In view of the new challenge brought by the integration of high proportion solar generation to the frequency stability of power grid, this paper analyzes the mechanisms of influence between them and introduces the current technical route of PV power... [more]
Optimal Energy Efficiency Tracking in the Energy-Stored Quasi-Z-Source Inverter
Sideng Hu, Zipeng Liang, Jing Zhou, Xiaoli Yu
April 4, 2023 (v1)
Keywords: energy storage unit, ES-qZSI, optimal operation, power loss analysis
In this paper, the interaction between the energy storage (ES) power distribution and system efficiency enhancement is researched based on the energy stored quasi-Z-source inverter. The corresponding current counteraction, stress reduction, power loss profile, and efficiency enhancement around the embedded energy storage units are studied in details. Firstly, the current counteraction effect on the device current is presented with the embedded ES source. The corresponding reduction in the device current stress is revealed. Then, the detailed device power loss expressions with current redistribution in the impedance network are explored mathematically. A quasi-inverted-trapezoidal power loss profile is found with the embedded source power distribution. To further increase the overall system efficiency, an optimal energy efficiency tracking strategy is proposed for the ES-qZSI (energy-stored quasi-Z-source inverter) based on the power distribution control. Both the simulation and the exp... [more]
Experimental Investigation of the Air Exchange Effectiveness of Push-Pull Ventilation Devices
Sven Auerswald, Carina Hörberg, Thibault Pflug, Jens Pfafferott, Constanze Bongs, Hans-Martin Henning
April 4, 2023 (v1)
Keywords: air exchange efficiency, decentralised ventilation, push-pull, ventilation effectiveness
The increasing installation numbers of ventilation units in residential buildings are driven by legal objectives to improve their energy efficiency. The dimensioning of a ventilation system for nearly zero energy buildings is usually based on the air flow rate desired by the clients or requested by technical regulations. However, this does not necessarily lead to a system actually able to renew the air volume of the living space effectively. In recent years decentralised systems with an alternating operation mode and fairly good energy efficiencies entered the market and following question was raised: “Does this operation mode allow an efficient air renewal?” This question can be answered experimentally by performing a tracer gas analysis. In the presented study, a total of 15 preliminary tests are carried out in a climatic chamber representing a single room equipped with two push-pull devices. The tests include summer, winter and isothermal supply air conditions since this parameter v... [more]
PCB-Embedded Spiral Pattern Pick-Up Coil Current Sensor for WBG Devices
Hwa-Rang Cha, Kyeong-Mo Kim, Min-Soo Song, Rae-Young Kim
April 4, 2023 (v1)
Keywords: current sensor, multilayer PCB pattern coil, wide bandgap devices
This paper proposes a current sensor for wide bandgap (WBG) devices. The current of a power semiconductor device is mainly measured using a Rogowski coil, an active current transformer, and a coaxial shunt resistor. The Rogowski coil and active current transformer are not suitable for the current measurement of surface mount WBG devices due to their operating principle. The coaxial shunt resistor causes parasitic inductance. Since WBG devices are more sensitive to parasitic inductance than silicon devices, parasitic inductance may affect circuit operation. To overcome these problems, this paper proposes a printed circuit board (PCB)-embedded spiral pattern pick-up coil current measurement for WBG devices. The proposed pick-up coil has high mutual inductance compared to the conventional pick-up coil, so the measurement sensitivity is high. In addition, there is no need for additional processing outside the PCB. Experimental results using a double pulse tester circuit are provided to ver... [more]
Space Charge Accumulation Characteristics in HVDC Cable under Temperature Gradient
Yifan Zhou, Wei Wang, Tailong Guo
April 4, 2023 (v1)
Keywords: bipolar charge transport (BCT) model, conductivity model, cross-linked polyethylene (XLPE), HVDC cable, pulsed electro-acoustic (PEA), space charge, temperature gradient (TG)
One of the main issues that affect the development of high-voltage direct-current (HVDC) cable insulation is the accumulation of space charge. The load operation of an HVDC cable leads to the formation of a radially distributed temperature gradient (TG) across the insulation. In this study, the space charge accumulation in a cross-linked polyethylene (XLPE) cable is measured under a DC electric field and TG using the pulsed electro-acoustic (PEA) method, and the effect of the TG on the space charge behavior is investigated. In addition, the bipolar charge transport (BCT) model and the conductivity model based on an improved cylindrical geometry are used to simulate the charge behavior in the HVDC XLPE cable under TG, and the experimental and simulated results are compared. The results show that the higher temperature of the cable conductor promotes the accumulation of homocharge near the side of high temperature. Additionally, with the increase of the TG, not only does more heterocharg... [more]
A Novel Analytic Method to Calculate the Equivalent Stray Capacitance of the Low-Speed Maglev Train’s Suspension Electromagnet
Da Liang, Kunlun Zhang, Qilong Jiang, Ying Wang
April 3, 2023 (v1)
Keywords: finite element method (FEM), floating potential, maglev train, stray capacitance, suspension electromagnet (SEM)
The suspension electromagnet (SEM) is one of the most critical components of the low-speed maglev train to achieve the stable suspension and non-contact operation with the track. Therefore, it is valuable for optimizing the maglev system to study the characteristics of the SEM. This paper proposes a novel analytic method to calculate the equivalent stray capacitance of the SEM efficiently. It considers the capacitances inside the winding (turn to turn and layer to layer) and between the winding and core. Firstly, utilizing the compensation analytic method (CAM) calculates the static capacitances to reduce the calculation error, and the results of the CAM have significant improvement comparing with that of the traditional analytic method (TAM). Secondly, the analytical formula of the core floating potential is derived based on the partial capacitance theory, which has a 2.1% relative error to the finite element method (FEM). Finally, the experiment results of the SEM of a test rig prove... [more]
The DSR Scheme in the Capacity Market of Industrial Enterprises in Poland—Participation Determinants
Bartosz Jeżyna, Marcin Lis, Agata Mesjasz-Lech
April 3, 2023 (v1)
Keywords: capacity market, capacity market DSR program, DSR, DSR guaranteed program
The purpose of this article is to present the key differences between the Polish Guaranteed DSR (demand-side response) Scheme operating from 2017 to 2020 and the Polish Capacity Market DSR Scheme operating from 2021, and their impacts on the decision to participate in the DSR scheme. The present study attempts to compare the rules of the old and new schemes and their impacts on the participation decision depending on the industry of the potential scheme participant. The study was conducted on a group of 50 randomly selected companies. A structured interview was used to collect information, and a chi-quadrant independence test and a Wilcoxon−Mann−Whitney test were used in the analysis of the collected data. The study was conducted in selected enterprises located in Poland. The results of the study indicate the elements that are similar to the literature on the subject, and key aspects arising from the unique characteristics of the Polish market and the industry of the potential particip... [more]
Supporting Decentralised Energy Management through Smart Monitoring Systems in Public Authorities
Graeme Stuart, Leticia Ozawa-Meida
April 3, 2023 (v1)
Keywords: communities of practice, decentralised energy management, public buildings, smart monitoring
Energy infrastructure in large, multi-site organisations such as municipal authorities, is often heterogeneous in terms of factors such as age and complexity of the technology deployed. Responsibility for day-to-day operation and maintenance of this infrastructure is typically dispersed across large numbers of individuals and impacts on even larger numbers of building users. Yet, the diverse population of stakeholders with an interest in the operation and development of this dynamic infrastructure typically have little or no visibility of energy and water usage. This paper explores the integration of utility metering data into urban management processes via the deployment of an accessible “smart meter” monitoring system. The system is deployed in three public authorities and the impact of the system is investigated based on the triangulation of evidence from semi-structured interviews and case studies. The research is framed from three perspectives: the bottom-up micro-level (individua... [more]
A Comparative Analysis of Two Cable Yarder Technologies Performing Thinning Operations on a 33 Year Old Pine Plantation: A Potential Source of Wood for Energy
Rodolfo Picchio, Rachele Venanzi, Nicolò Di Marzio, Damiano Tocci, Farzam Tavankar
April 3, 2023 (v1)
Keywords: cable yarder, CO2 emission, Energy Efficiency, fuelwood, pine plantations, time study
In central Italy, there are extensive European black pine (Pinus nigra Arn.) plantations which range from 30 to 60 years of age and where no thinning operations have been made. The main purpose of this study was to provide a comparative analysis of two cable yarder technologies (Maxwald, mobile pulley carriage and Savall, semi-automatic carriage), in terms of fuelwood production and cost, from the first thinning of a 33 year old plantation in slope areas of these plantations. The results showed that fuelwood production was cost-effective in both systems (Savall by 15.1 and Maxwald by 14.8 € m−3), although the productivity of the Savall system was higher than the Maxwald system (6.1 vs. 5.7 m3 h−1). The respect amounts of productivity have the potential to increase by 27% for the Savall yarder and 25% for the Maxwald yarder upon condition that the delay times are reduced to minimum level by proper training of workers, by a better organization, and planning of operations. The total effec... [more]
A Feasibility Study of Frequency Regulation Energy Storage System Installation in a Power Plant
Lateef Onaadepo Ibrahim, Youl-Moon Sung, Doosoo Hyun, Minhan Yoon
April 3, 2023 (v1)
Keywords: ESS, ESS location, ESS operation, ETAP, load flow, relay coordination, short circuit
The aim of this work is to analyze and stabilize the power system when connecting an energy storage system (ESS) to replace the traditional power reserve of a power plant. Thus, it is necessary to validate and simulate the power facility protection system using a relay coordination approach. The input feasibility of the generator for the frequency regulation (FR) of the operational ESS is also validated through detailed analysis studies including power flow, short circuit and relay coordination analysis. The case scenarios for ESS installation are categorized based on its operation mode and location in the power system. These studies are carried out on the power system at the peak load condition specified for both grids. With the electrical transient analyzer program (ETAP), an analysis is performed to study the implementation of the ESS in a large, integrated power system to determine which location best fits the installation of ESS considering the load flow, short circuit and relay c... [more]
Microalgae Oil Production Using Wastewater in Japan—Introducing Operational Cost Function for Sustainable Management of WWTP
Riaru Ishizaki, Agusta Samodra Putra, Sosaku Ichikawa, Tofael Ahamed, Makoto M. Watanabe, Ryozo Noguchi
April 3, 2023 (v1)
Keywords: biocrude, economic efficiency, microalgae, oxidation ditch, wastewater treatment
A comparative evaluation of economic efficiency was performed for native polyculture microalgae oil production in an oxidation ditch (OD) process wastewater treatment plant (WWTP). A cost function was developed for the process. The operational cost per 1 m3 of wastewater (w.w.) was 1.34 $/m3-w.w. in the existing scenario, 1.29 $/m3-w.w. in algal scenario A (no cost for CO2 and waste heat) and 1.36 $/m3-w.w. in algal scenario B (no cost for CO2). The conditions were set as follows: hydraulic retention time (HRT): 4 days, microalgal productivity: 0.148 g/L and daily treatment volume: 81.6 m3-w.w./d. The cost differences were related to the increase in polymer flocculants for algae separation (+0.23 $/m3-w.w), carbon credits from CO2 absorption (−0.01 $/m3-w.w), the sales of biocrude (−0.04 $/m3-w.w) and sludge disposal (−0.18 $/m3-w.w). Hence, the introduction of the algae scenario was the same cost-effective as the existing scenario. Microalgae oil production in an OD process WWTP can s... [more]
Incomplete Cross-Bonding in the MV Line. Experience from the Operation of MV Single Cable Lines
Krzysztof Dobrzynski, Zbigniew Lubosny, Jacek Klucznik, Janusz Grala, Dominik Falkowski
April 3, 2023 (v1)
Keywords: cross-bonding, induced sheath current, induced sheath voltage, MV cable line
Cable lines are one of the basic components of power systems. Medium and high voltage cables mainly comprise a metallic sheath, which is concentric to the main core conductor. There are several operating schemes of such cable lines, which differ in the place of earthing of sheaths and the possible use of the sheaths and/or conductors crossing. The sheaths cross-bonding is typically done in two places of one cable line section, and it allows to reduce power losses. Nevertheless, the use of incomplete sheaths crossing—only in one place on cable route may have economic justification. The paper presents an incomplete sheaths cross-bonding analysis of an existing medium voltage cable line. The results obtained by the mathematical model are validated by measurements taken on 30 October 2019 on an existing cable line. Measurements recorded on a real object for various systems of crossing sheaths are presented. The influence of incorrect sheaths crossing on the measured quantities was shown. I... [more]
AATTENUATION—The Atmospheric Attenuation Model for CSP Tower Plants: A Look-Up Table for Operational Implementation
Natalie Hanrieder, Abdellatif Ghennioui, Stefan Wilbert, Manajit Sengupta, Luis F. Zarzalejo
April 3, 2023 (v1)
Keywords: atmospheric extinction, attenuation loss, central receiver, CSP, solar energy, solar resource assessment, solar tower plant, transmittance model
Attenuation of solar radiation between the receiver and the heliostat field in concentrated solar power (CSP) tower plants can reduce the overall system performance significantly. The attenuation varies strongly with time and the average attenuation at different sites might also vary strongly from each other. If no site specific attenuation data is available, the optimal plant design cannot be determined and rough estimations of the attenuation effect are required leading to high uncertainties of yield analysis calculations. The attenuation is caused mainly by water vapor content and aerosol particles in the lower atmospheric layer above ground. Although several on-site measurement systems have been developed during recent years, attenuation data sets are usually not available to be included during the plant project development. An Atmospheric Attenuation (AATTENUATION) model to derive the atmospheric transmittance between a heliostat and receiver on the basis of common direct normal i... [more]
Operation Analysis of a SAG Mill under Different Conditions Based on DEM and Breakage Energy Method
Qiyue Xie, Caifengyao Zhong, Daifei Liu, Qiang Fu, Xiaoli Wang, Zhongli Shen
April 3, 2023 (v1)
Keywords: DEM, fill level, mill power, mill speed, SAG mill, steel ball ratio
As one of the machines widely used in mining, a semi-autogenous grinding (SAG) mill can significantly improve the roughing efficiency of rock. But the SAG mill still faces the obstacles of significant energy consumption and empirical operation parameters. In order to obtain the optimal operation parameters of a SAG mill, in this paper, the discrete element method (DEM) is used to simulate the breakage process of the particles by controlling three parameters, i.e., the mill speed ratio, the mill fill level ratio, and the steel ball ratio. This method simulates the particles size, mill power, and qualified particles quality of crushed particle, which reveal the grinding strength and energy consumption of the SAG mill. In this paper, the grinding changes of a SAG mill under different parameter conditions are explored. Firstly, an experiment on the influence of a single parameter change on the mill’s operation is set up, and then the influence of three parameter changes on the mill’s opera... [more]
Specific Energy Consumption of a Belt Conveyor System in a Continuous Surface Mine
Witold Kawalec, Natalia Suchorab, Martyna Konieczna-Fuławka, Robert Król
April 3, 2023 (v1)
Keywords: belt conveyor, energy consumption, sustainable operation
Belt conveyor (BC) transportation systems are considered to be the most effective for handling large volumes of bulk material. With regards to the rules of sustainable development, the improvement of belt conveyor technology is, in many cases, focused on environmental issues, which include the idea of energy usage optimization. The key issue in an energy-efficient transportation system is reducing the value of specific energy consumption (SEC) by increasing conveyor capacity whilst decreasing belt conveyor motion resistance. The main idea of this paper is to conduct an analysis of the modernization of existing belt conveyor transportation systems operated in open-pit lignite mines, in order to achieve relatively small electric energy consumption for a considered transportation task. The first part of the paper investigates the relationship between a conveyor’s SEC and material flow rate for various conveyor design parameters. Then, based on multi-parameter simulations, an analysis of e... [more]
Experimental Investigation of Inhibitive Drilling Fluids Performance: Case Studies from United States Shale Basins
Nabe Konate, Saeed Salehi
April 3, 2023 (v1)
Keywords: drilling performance, friction factor, inhibitive drilling fluids, rate of penetration, swelling, torque
Shale formations are attractive prospects due to their potential in oil and gas production. Some of the largest shale formations in the mainland US, such as the Tuscaloosa Marine Shale (TMS), have reserves estimated to be around 7 billion barrels. Despite their huge potential, shale formations present major concerns for drilling operators. These prospects have unique challenges because of all their alteration and incompatibility issues with drilling and completion fluids. Most shale formations undergo numerous chemical and physical alterations, making their interaction with the drilling and completion fluid systems very complex to understand. In this study, a high-pressure, high-temperature (HPHT) drilling simulator was used to mimic real time drilling operations to investigate the performance of inhibitive drilling fluid systems in two major shale formations (Eagle Ford Shale and Tuscaloosa Marine Shale). A series of drilling experiments using the drilling simulator and clay swelling... [more]
Fault Current Limiting and Breaking Characteristics of SFCLB Using Flux Coupling with Tap Changer
Sung-Hun Lim, Jin-O. Kim, Youngjin Jeong
April 3, 2023 (v1)
Keywords: breaking time, flux coupling, mechanical switch, superconducting fault current limiting breaker (SFCLB), tap changer, winding method
In this paper, a superconducting fault current limiting breaker (SFCLB) using flux coupling with a tap changer is suggested and its effective fault current limiting and breaking characteristics due to the winding method using its tap changer are analyzed. The suggested SFCLB using flux coupling, which consists of the SFCLB using flux coupling with a tap changer, mechanical switch and driving coil, can perform the circuit-breaking function without external driving power after the fault current limiting operation. To examine the suggested SFCLB’s operation, the small scale SFCLB using flux coupling was fabricated and alternative current (AC) short-circuit experiments due to the winding method using the tap changer of the SFCLB were executed. From the experimental results, a lower fault current limiting rate and faster breaking time in the case of a SFCLB with a series connection could be obtained compared to one with a parallel connection.
Methodology for Predictive Assessment of Failures in Power Station Electric Bays Using the Load Current Frequency Spectrum
Fábio Vinicius Vieira Bezerra, Gervásio Protásio Santos Cavalcante, Fabrício Jose Brito Barros, Maria Emília Lima Tostes, Ubiratan Holanda Bezerra
April 3, 2023 (v1)
Keywords: circuit breakers, electrical contacts, Fourier transform, predictive maintenance, sectionalizing switches, signal-to-noise ratio, spectral analysis
This paper presents a novel analysis methodology to detect degradation in electrical contacts, with the main goal of implanting a predictive maintenance procedure for sectionalizing switches, circuit breakers, and current transformers in bays of electric transmission and distribution substations. The main feature of the proposed methodology is that it will produce a predictive failure indication for the system under operation, based on the spectral analysis of the load current that is flowing through the bay’s components, using a defined relationship similar to the signal-to-noise ratio (SNR) used in data communication. A highlight of using the proposed methodology is that it is not necessary to make new investments in measurement devices, as the already-existing oscillography measurement infrastructure is enough. By implementing the diagnostic system proposed here, electrical utilities will have a modern tool for monitoring their electrical installations, supporting the implementation... [more]
“In Situ” Evaluation of Mechanical Wear of Mobile Contacts of Electricity Voltage Regulator
Max Gabriel Steiner, Anderson Diogo Spacek, João Mota Neto, Pedro Rodrigo Silva Moura, Oswaldo Hideo Ando Junior, Cleber Lourenço Izidoro, Luciano Dagostin Bilessimo, Jefferson Diogo Spacek
April 3, 2023 (v1)
Keywords: fixed contacts, mechanical wear, mobile contacts, on load contact-changer, voltage regulator
This in situ study presents an analysis of the wear of mobile contacts of switching in an automatic line voltage regulator, regarding the surface wear of the contacts. It is interesting to analyze the contacts of this equipment due to the friction and wear generated during the contact change, in order to predict and contain mechanical operation failures. The contacts were evaluated for mass loss, profilometry, and analysis in a scanning electron microscope, after remaining in operation in the regulator for about one year and switching the contacts almost 2500 times. This study aims to evaluate the performance of the contacts, in terms of surface wear, correlating the number of switching and the effects generated on the contacts in terms of loss of mass and surface damage. With the results obtained, it is possible to conclude that with each switching maneuver the mobile contact loses about 0.002895% of its initial mass. In addition, there was a change in the topography of the sample, as... [more]
A Novel Check-List Strategy to Evaluate the Potential of Operational Improvements in Wastewater Treatment Plants
Vojtěch Zejda, Vítězslav Máša, Šárka Václavková, Pavel Skryja
April 3, 2023 (v1)
Keywords: efficiency evaluation, methodology, overall efficiency, parameter analysis, Wastewater, WWTP
With increasing demands for cleaning and purification of water, wastewater treatment plants (WWTP) require their most efficient operation. The operators are thus obliged to constantly review the efficiency of the processing units and technological equipment of WWTPs and seek opportunities for improvements. To increase the efficiency of particular equipment, the important parameters to be used for the intensification must be correctly selected. A common WWTP consists of different types of processing units, where the basic parameters can be changed to achieve the highest efficiency (i.e., maximum output with minimum energy consumption) in the WWTP. However, due to many possible technologies in the wastewater treatment process, the combinations of processing units can be complex. In such cases, the efficiency assessment can be misleading if only basic parameters were accessed. Moreover, single-unit intensification can potentially improve the efficiency of the unit itself but cannot guaran... [more]
Comparative Analysis on Load Characteristic of Intermittently Conditioned Buildings for Different Wall Insulation Forms
Liting Yuan, Zhiyi Wang, Yanyan Huang, Xiaolong Wang
April 3, 2023 (v1)
Keywords: energy consumption, insulation form, intermittent operation, peak load, peak-valley load difference
The Air-conditioning System (ACS), used in office buildings in the hot summer and cold winter zone of China, are always operate intermittently. The dynamic thermal behaviors of building walls with real climate conditions may be different from those with only the representative day’s climate conditions, due to the time varying nature of the climate, which will lead to the variation of the ACS loads. A numerical calculation was performed to analyze the effects of insulation form on heat behavior of external walls and ACS loads. The results indicate that cooling transmission load with inside insulation reaches its maximum value when the solar-air temperature in daytime is the highest, while that with outside insulation occurs at the time when the air temperature at night is the highest during summer. Heating transmission load for the wall with external and internal insulation both peaks in the day with lowest mean outdoor temperature during the last non-working period. Inside insulation c... [more]
Efficiency of Telematics Systems in Management of Operational Activities in Road Transport Enterprises
Ryszard K. Miler, Marcin J. Kisielewski, Anna Brzozowska, Antonina Kalinichenko
April 3, 2023 (v1)
Keywords: a universal matrix of efficiency rates, operational activities of RTEs, road transport enterprises (RTEs), telematics systems
Implemented in road transport enterprises (RTEs) on a large scale, telematics systems are dedicated both to the particular aspects of their operation and to the integrated fields of the total operational functioning of such entities. Hence, a research problem can be defined as the identification of their efficiency levels in the context of operational activities undertaken by RTEs (including more holistic effects, e.g., lowering fuel/energy consumption and negative environmental impacts). Current research studies refer to the efficiency of some particular modules, but there have not been any publications focused on describing the efficiency of telematics systems in a more integrated (holistic) way, due to the lack of a universal tool that could be applied to provide this type of measurement. In this paper, an attempt at filling the identified cognitive gap is presented through empirical research analysing the original matrix developed by the authors that refers to the efficiency rates... [more]
Water Heating and Operational Mode Switching Effects on the Performance of a Multifunctional Heat Pump
Win Jet Luo, Kun Ying Li, Jeng Min Huang, Chong Kai Yu
April 3, 2023 (v1)
Keywords: Circulating heating, coefficient of performance, composite operational mode, Direct heating, multifunctional heat pump
In this study, a multifunctional air and water source heat pump system was developed with a parallel refrigerant piping arrangement, which possessed six operational functions: space cooling (SC), space heating (SH), water heating (WH), water cooling (WC) and two composite operational modes. The two composite operational modes were the SC/WH mode and the SH/WH mode. The performance of the multifuctional heat pump system under different ambient conditions was investigated based on the testing standards of CNS 14464 and CNS 15466. In this study, the effect of the direct water heating (DWH) and circulating water heating (CWH) methods on the performance was investigated. It was found that the water heating performance of the system by the DWH method is better than that of the system by the CWH method. The water heating capacity and COPw,h of the DWH method can be improvement by 2.6% to 22.1% and 2.9% to 50.8%, respectively. Moreover, this study developed a refrigerant pressure balance metho... [more]
Multi-Agent Cooperation Based Reduced-Dimension Q(λ) Learning for Optimal Carbon-Energy Combined-Flow
Huazhen Cao, Chong Gao, Xuan He, Yang Li, Tao Yu
April 3, 2023 (v1)
Keywords: multi-agent cooperation, optimal carbon-energy combined-flow, reduced-dimension Q(λ)
This paper builds an optimal carbon-energy combined-flow (OCECF) model to optimize the carbon emission and energy losses of power grids simultaneously. A novel multi-agent cooperative reduced-dimension Q(λ) (MCR-Q(λ)) is proposed for solving the model. Firstly, on the basis of the traditional single-objective Q(λ) algorithm, the solution space is reduced effectively to shrink the size of Q-value matrices. Then, based on the concept of ant cooperative cooperation, multi-agents are used to update the Q-value matrices iteratively, which can significantly improve the updating rate. The simulation in the IEEE 118-bus system indicates that the proposed technique can decrease the convergence speed by hundreds of times as compared with conventional Q(λ), keeping high global stability, which is very suitable for dynamic OCECF in a large and complex power grid compared with other algorithms.
Reliability and Network Performance Enhancement by Reconfiguring Underground Distribution Systems
Praveen Agrawal, Neeraj Kanwar, Nikhil Gupta, Khaleequr Rehman Niazi, Anil Swarnkar, Nand K. Meena, Jin Yang
April 3, 2023 (v1)
Keywords: dynamic failure rate, loss reduction, network reconfiguration, reliability, undergrounded distribution systems
Contemporary distributions are now going to underground their overhead distribution lines due to techno-social reasons. Reliability and loss reduction are the two prime objectives for distribution system operation. Since failure rates of ungrounded cables are the function of Joules heating besides their physical lengths, the reliability evaluation of undergrounded distribution systems needs to be reviewed. This paper suggested a suitable modification in existing reliability indices in order to make them more appropriate for underground distribution systems. A multi-objective network reconfiguration problem is formulated to enhance the reliability and performance of distribution systems while duly addressing the variability and uncertainty in load demand and power generation from renewables. The application results on a standard test bench shift the paradigm of the well-known conflicting nature of reliability and network performance indices defined for overhead distribution systems.
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