Electrification System Research Articles

Influence of the rail electrification system topology on the energy consumption of train trajectories

Electrically powered rail vehicles are considered one of the most energy-efficient means of transport. Transport activity is responsible for a considerable part of global energy consumption. The transport industry is therefore obliged to develop strategies for more efficient energy use. Railway electrification systems transmit the electrical power supplied by substations to moving trains. However, part of the power supplied is consumed by the electrification systems and does not reach the trains. In this study, transmission losses in the 2 × 25 kV electrification system are evaluated. The 2 × 25 kV system is widely used in high-speed and high-capacity railway lines. Assessment of the performance of the 2 × 25 kV system is carried out by computer simulation of the power flows between the elements involved in train movement by means of simplified physical models. The results show that the reduction of transmission losses is a feasible way to achieve energy savings and to improve the energy efficiency in electrified rail transport. For this, it is essential to add the topology of the electrification system to the data considered in the design of the train trajectories.

Optimal Sizing of Hybrid Renewable Energy System for off-Grid Electrification: A Case Study of University of Ibadan Abdusalam Abubakar Post Graduate Hall of Residence

The main objective of this study is to design a Hybrid Renewable Energy System (HRES) to meet the energy demand of a major Post Graduate Student residential hostel. The specific objectives were to estimate the energy demand, perform economic and technical analysis of various combination of renewable energy technologies that can meet the estimated energy demand and to select the appropriate and optimum hybrid system for the hall of residence. Quantitative analysis was used to determine the energy demand of the hall of residence while the solar resource information was obtained from the NASA Surface Meteorology. The Hybrid Optimization Model for Electric Renewables (HOMER) software was used for analysis. The components of the system considered were solar photovoltaic (PV), diesel generator, batteries and inverter. The optimised hybrid system obtained was also compared to a system in which a diesel generator serves as the sole source of electricity supply. Economic analysis using the total net present cost and levelized cost of enegy was employed to determine the optimized hybrid combination. Environmental considerations were also made based on the amount of Carbon dioxide emitted per year. Results indicates that electricity generation through a hybrid system made up of 1000kW PV, 110 kVA generator, 11791 kWh Surrette S6CS25P battery arranged in parallel strings and a 220 kW Inverter had the lowest total net present cost, lowest cost of energy with a low emission. Hence, Hybrid Renewable Energy Systems (HRES) should be employed in the production of electricity in due to its ability to reduce environmental degradation while ensuring a low total net present cost and a low cost of energy.

Feasibility and optimal design of a hybrid power system for rural electrification for a small village

A hybrid renewable energy system is at present accepted globally, as the best option for rural electrification particularly in areas where grid extension is infeasible. However, the need for hybrid design to be optimal in terms of operation and component selection serves as a challenge in obtaining reliable electricity at a minimum cost. In this work, the feasibility of installing a small hydropower into an existing water supply dam and the development of an optimal sizing optimization model for a small village-Itapaji, Nigeria were carried out. The developed hybrid power system (HPS) model consists of solar photovoltaic, small hydropower, battery and diesel generator. The optimal sizing of the system’s components for optimum configuration was carried out using Genetic Algorithm. The hybrid model’s results were compared with hybrid optimization model for electric renewable (HOMER) using correlation coefficient (r) and root mean square error (RMSE) to verify its validity. The results of the simulation obtained from the developed model showed better correlation coefficient (r) of 0.88 and root mean square error (RMSE) of 0.001 when compared to that of HOMER. This will serve as a guide for the power system engineers in the feasibility assessment and optimal design of HPS for rural electrification.

Technoeconomic feasibility study of grid-connected building-integrated photovoltaics system for clean electrification: A case study of Doha metro

Issues like air pollution and high CO2 rates are forcing the government of Qatar to mitigate these pollution rates as Qatar is considered the highest country that has can emissions per capita. As a result, huge efforts are executed to reduce these high rates of pollution so many renewable technologies projects are introduced, and solar PV plant is a major one. In this paper, Doha metro project is taken as a case study to implement a hybrid system within one of the metro stations to assess the economic profitability of it and then it can be a proposal for the country of Qatar to implement such a hybrid system within the governmental projects to mitigate the pollution rate. The methodology adopted in this paper is to evaluate the profitability of the hybrid system proposed by using HOMER software where it can model, simulate and optimize the proposed system with the desired components. Main finding is that due to the low electricity tariffs with and without the governmental subsidies, the implementation of PV system in Qatar is not economically feasible unless the PV system capacity is enlarged into a big scale or the tariff prices being increased with Carbon tax regulations.

Wideband Modeling of Power SiC MOSFET Module and Conducted EMI Prediction of MVDC Railway Electrification System

Wideband Modeling of Power SiC MOSFET Module and Conducted EMI Prediction of MVDC Railway Electrification System

Priority-based low voltage DC microgrid system for rural electrification

This paper discusses the current state of DC distribution system, how it can be beneficial to isolate solar-based Micro-Grid (MG) system in a rural area, and how the priority-based approach can help the MGs to operate in cost-effective and reliable ways. DC distribution system holds many advantages over AC systems in such area, where the load demand is not so high and the electricity supply through grid extension is not feasible. Direct load control-based approach can ensure a continuous supply of power to the loads with various priorities. In this paper, an experimental analysis of the DC MGs has been presented with the help of priority based algorithms. A cost-effective SCADA system is developed to interface with the remaining parts of the system, so that the MGs can be monitor and control to get the desired performance. The main objective of this study is to identify a cost-effective and practical energy management system for the rural area, where expensive and advanced technology is not suitable. From this study, it is concluded that the proposed combination of algorithm and SCADA system increase the system’s reliability and power consistency significantly.

A Novel Hybrid Solar-wind Energy Conversion System for Remote Area Electrification

Background: Remote area electrification is a social responsibility that needs to be catered by research fraternity. One of the most viable technology as a solution is the Renewable Energy Source (RES) based power generation. However, RES is intermittent and thus, mostly ineffective without an energy storage device. Energy storage device comes at increased cost and may not be a cost-effective solution to the problem. Introduction: One solution that has been frequently proposed to reduce the intermittency of RES is hybridization. Hybridization of RES such as Wind Energy Conversion System (WECS) with Solar Energy Conversion System (SECS) is the most basic solution offered owing to their complementary nature. Therefore, this paper sees SECS in the role of supporting WECS in regions with highly intermittent wind conditions. In this paper, a novel technique of hybridization of WECS with SECS has been proposed. Methods: The basic idea of the paper is to control the dc-link voltage from the generation side by regulating the power generated by RES as per load demand using minimum components. The underlined principle is the relative lower time constant of solar panel and battery system in comparison to a wind turbine. Results: The experimental results on the proposed system shows that the SECS supports the WECS at higher wind turbulence and low wind conditions. Conclusion: This unique feature of the proposed system enables a WECS supported by a small rated SECS to attain high power reliability and thus, suitable for application such as remote area electrification.

Optimization and sustainability analysis of PV/wind/diesel hybrid energy system for decentralized energy generation

This paper focuses on the techno-economic feasibility and sustainability of a PV/wind/diesel hybrid system designed for decentralized power supply. Several designs have been studied for the hybrid system by varying the PV slope and wind turbine hub height under different dispatch strategies to supply the load. For each design, the power system has been optimized to determine the maximum electrical output at a low cost. Sensitivity analyses have been performed to evaluate operational risk in the actual operation as well as the cost-effectiveness of the proposed system. As a final remark, the sustainability of the proposed hybrid energy system has been analyzed based on some key indicators to understand the implications of a design choice on electrical production, CO2 emission and cost of energy. Our results show that for a projected period of 25 years, the selected hybrid power system for electrification of a housing estate will cost 10.2 million USD for a daily load of 4876.5 kWh, and the cost for every kWh of electricity generated is $0.4574. Results also show that the hybridization of the standard diesel generating system increased the reliability and cost-effectiveness of the power system, saving $0.316 for every kWh of electricity generated, with about 1,521,310 kg of CO2 emission avoided annually.

Genetic Algorithm Scaling for Compensation System Control in Micro Hydro/Solar Hybrid System for Rural Electrification

Recent technologies have been focusing on power generation through renewable energy resources such as solar, wind, hydro etc. This paper focuses on development of a micro solar/hydro power generating resources feeding local loads. The compensation system derived for the small scale loading conditions at the load line was made using PI scaling Genetic Algorithm based control keeping the general architecture of the UPFC same. The results had depicted enhancement in the active power output, better reactive power compensation and reduction in THD levels of voltage and current at the load line.

Characterization and Implementation of Resonant Isolated DC/DC Converters for Future MVdc Railway Electrification Systems

Today, in electric railways, the old dc supply systems are reaching their limits. To improve their efficiency and increase railroad traffic, a new dc electrification has recently been proposed at 9 kV. It is now necessary to prepare the migration of infrastructure and rolling stock, using power electronic transformers (PETs), for adaptation to this voltage level. For this application, high efficiency and reduced volume are essential. This article clearly demonstrates that it is now possible to achieve a compact, high-power, isolated dc-dc converters using 3.3-kV SiC-MOSFET power modules with high efficiency. After a preliminary study based on simulations, this article focuses on the characterization and implementation of elementary isolated dc-dc converters. The proposed topology is a series-resonant converter rated for a nominal power of 300 kW at 1.8 kV. First, laboratory testing using an “opposition method” is used to evaluate the elementary converters up to their nominal power using both electrical and thermal measurements to accurately determine losses and efficiency. At the nominal output power, an efficiency of 98.93% is obtained. This is quite remarkable for an isolated dc-dc converter operating under 1.8 kV with a switching frequency of 15 kHz. Finally, two elementary isolated dc/dc converters are associated with input series/output parallel (ISOP) configuration in order to achieve a 3-kV/1.5-kV PET with a nominal power of 600 kW as a prelude to the final 9-/1.5-kV power conversion.

Technical, Economical, and Environmental Feasibility of Hybrid Renewable Electrification Systems for off-Grid Remote Rural Electrification Areas for East Azerbaijan Province, Iran

Nowadays, global warming, air pollution emissions, climate change, and fuel price growth are chronic challenges on a global scale for residential sectors. To overcome this, renewable energy systems would certainly be a potential alternative. Expanding electricity to remote rural areas with no access to grid electricity is a significant concern in the Middle East countries such as northern west of Iran. Off-grid hybrid renewable energy systems (RES) can be an ideal solution for remote rural areas no access is available to grid electricity. This research investigates the application of wind turbine, PV panels, and diesel generator in a hybrid renewable energy system for six off-grid remote villages, with separate locations and various climate statues, for East Azerbaijan province, Iran. Hybrid renewable energy system applies optimal size of several environmentally-friendly sources via HOMER software. In this study, for offering suitable configuration, all possible configurations of the renewable energy system were formulated for each village. These communities were chosen based upon Iran’s Sixth Five-Year Economic and Renewable Energy Development Plan (2017–22). Wind speed and solar radiation data were extracted from Surface Meteorology and Solar Energy Dataset of NASA. For achieving accurate data on wind speed and solar radiation, as well as population for each community, they were extracted from Iran’s Atlas and National Department of Statistics respectively. In order to explore the most cost-effective and efficient design for each community, various models of wind turbine, PV panels, and diesel generator were designed and optimized. In this study, most important economic indicators including initial capital ($), operating cost ($/yr), total NPC ($), and cost of energy ($/kwh) were taken into account. For conducting economic and environmental sustainability, HOMER software was applied. For economic modelling and geographical position, Visio and Arc GIs software were used respectively.

Towards a methodology for new technologies assessment in aircraft operating cost

The need for a greener and competitive aircraft is leading to the use of new technologies. A thorough assessment of these technologies is mandatory from the initial phases of aircraft design to understand their feasibility and to select the most promising one both in terms of performances and in terms of costs. This paper proposes a methodology to assess the operating cost of innovative technologies for regional aircraft. In particular, two NASA studies have been adopted to determine the impact onto costs of MEA and AEA technologies and advanced ECS solutions for two innovative regional aircraft concepts developed during the European Clean Sky 2 research. The proposed methodology is able to assess the effect of on-board systems electrification level in terms of fuel and maintenance costs savings. The methodology, which allows to evaluate the effect of specific technological improvements onto costs, is applied exploiting the results provided by a reliable cost model and gives the opportunity to quantify operating cost savings for different regional aircraft. Applying the modified cost model to the reference aircraft under study, savings ranging from 1.6 to 3.1% of direct operating cost are estimated for MEA and AEA technologies. Greater savings are estimated for the individual cost items involved. More specifically, a reduction of fuel cost ranging from 6 to 14.5% is envisaged as a consequence of the lower SFC associated to innovative ECS technologies.

Tračnička infrastruktura u potresom pogođenim područjima

In the case o seismic impact on rail infrastructure, even small deformations or damage to track structure can compromise safe operation of rail traffic. Damage can affect track substructure or permanent way of the track, but also the electrification system and safety-signalling devices. Ballast prism will suffer damage in case of greater intensity earthquakes, resulting in the reduction of lateral and longitudinal resistance of track structure. Earthquake action may also cause derailment of moving rail vehicles. Operation of rail vehicles also causes certain levels of vibrations, and so an analysis of subsequent effects of rail traffic.

A Study on the Detachment Characteristics of the Tramwave Catenary-Free Electrification System for Urban Traffic

The tramwave catenary-free system (TCS)—a novel type of electrified transit system for urban railways—receives traction energy from a flexible ground-embedded ferromagnetic strip, which is energized only if a corresponding segment is located underneath the vehicle body. The current collector in the TCS is equipped with an “I-shaped” permanent magnet combination that produces a lifting force on the flexible ferromagnetic strips with octopus-shaped copper sheets located on the surface of the strips underneath the ground. The vehicle’s high-voltage circuit conducts when an electrical contact is maintained by the attractive force of the permanent magnet combination mounted inside the magnetic current collector. However, it has recently been observed that due to the dynamic processes during the electrical contact a severe electrochemical corrosion may occur on the surface of the octopus-shaped copper sheets, which can jeopardize the safe operation of the whole electrified transit system of trams. In order to identify the origins of this electrochemical corrosion, the dynamic characteristics of the TCS have been evaluated with particular attention paid to the impact of eddy currents on the attractive force of the permanent magnet combination under variable operational velocities of vehicles. Based on the dynamic characteristics of TCS, the arc erosion process on the surface of the copper sheet has been reproduced using an arc-discharge experimental platform and the causes of electrochemical corrosion in the TCS have been found. The damage development trends—under increasing speeds of trams—evaluated by the dynamic model of the TCS are consistent with the statistical data for practical damage situations.

Evaluation and optimization of off-grid and on-grid photovoltaic power system for typical household electrification

This study aims to design a renewable energy system that can meet the desired electrical load of households with low energy cost, high renewable energy fraction and low CO2 emissions. Photovoltaic solar power systems used to electrify typical households in Iraq were investigated through simulation and optimisation. One-minute resolution simulations and optimisations were performed to determine the performance and net present cost of two photovoltaic power system configurations, namely (i) off-grid and (ii) on-grid solar photovoltaic power systems. Results show that the two systems exhibit excellent performance, but the on-grid photovoltaic power system requires cheaper cost compared with the off-grid photovoltaic power system. The total energy generated from the off-grid photovoltaic power system meets the desired electrical load of households and recharges the batteries, whereas the excess electricity from the on-grid photovoltaic power system feeds the grid. The two designed systems are environmentally friendly and economically viable. The total net present cost of the off-grid solution is $6,244, and its energy cost is $0.196/kWh. By contrast, the total net present cost of the on-grid system is $6,115, with energy cost equal to $0.183/kWh. The obtained results confirm the suitability of photovoltaic power systems for electrifying single households in addition to feeding the national grid.

Machine Learning for Energy Systems

The objective of this editorial is to overview the content of the special issue “Machine Learning for Energy Systems”. This special issue collects innovative contributions addressing the top challenges in energy systems development, including electric power systems, heating and cooling systems, and gas transportation systems. The special attention is paid to the non-standard mathematical methods integrating data-driven black box dynamical models with classic mathematical and mechanical models. The general motivation of this special issue is driven by the considerable interest in the rethinking and improvement of energy systems due to the progress in heterogeneous data acquisition, data fusion, numerical methods, machine learning, and high-performance computing. The editor of this special issue has made an attempt to publish a book containing original contributions addressing theory and various applications of machine learning in energy systems’ operation, monitoring, and design. The response to our call had 27 submissions from 11 countries (Brazil, Canada, China, Denmark, Germany, Russia, Saudi Arabia, South Korea, Taiwan, UK, and USA), of which 12 were accepted and 15 were rejected. This issue contains 11 technical articles, one review, and one editorial. It covers a broad range of topics including reliability of power systems analysis, power quality issues in railway electrification systems, test systems of transformer oil, industrial control problems in metallurgy, power control for wind turbine fatigue balancing, advanced methods for forecasting of PV output power as well as wind speed and power, control of the AC/DC hybrid power systems with renewables and storage systems, electric-gas energy systems’ risk assessment, battery’s degradation status prediction, insulators fault forecasting, and autonomous energy coordination using blockchain-based negotiation model. In addition, review of the blockchain technology for information security of the energy internet is given. We believe that this special issue will be of interest not only to academics and researchers, but also to all the engineers who are seriously concerned about the unsolved problems in contemporary power engineering, multi-energy microgrids modeling.

Coupled rigid-flexible modelling and dynamic characteristic analysis of electromechanical brake (EMB) units on trains

The electromechanical braking is a novel braking mode, which is the development direction of the electrification and intelligent train braking system. In this paper, a coupled-rigid-flexible model of the EMB unit is developed, and dynamic characteristics of the EMB unit are analysed based on the model. Firstly, assumed mode method is used to describe the axial and torsional vibration of the screw in nut-screw assembly, and lumped mass method is used to describe motions of other components in the EMB unit. Secondly, the EMB unit model is established and simulated in Matlab/Simulink software based on electro-mechanical and rigid-flexible coupling characteristics. Then the model parameters are calibrated by experiment. Finally, the simulated model is studied to analyse the influence of various factors on the dynamic characteristics of the EMB unit. The results indicate that an increment in viscous damping flats the fluctuation of the pushout force. The maximal pushout force decreases and the changing trend of force is different along with the rotational structure damping increases. The flexible vibration of the screw results in higher pushout force, meanwhile the fluctuation of the force is greater with higher braking instruction current value. When the ratio of the screw length to the screw cross-sectional diameter is 30, the pushout force varies along with the friction pairs wear under vibration. The study can provide references for structure design, control design and fault diagnosis of EMB units.

Multidisciplinary aircraft integration within a collaborative and distributed design framework using the AGILE paradigm

The aircraft design is a collaborative and multidisciplinary process. It involves several experts with different disciplinary competences. These disciplinary experts often belong to different departments or organizations. The EU funded H2020 AGILE project aims at developing new generation of Multidisciplinary Design Analysis and Optimization (MDAO) frameworks. In particular, the AGILE project tackles the investigation and the development of technologies able to enhance the collaboration between the disciplinary experts. The present paper deals with a MDAO framework developed in the context of the AGILE research project. The integration of some disciplinary expertise is described by means of a case study of an innovative regional aircraft. Some disciplinary design variables are investigated to verify the correctness of disciplines integration and to quantify the mutual dependences among the design disciplines. In particular, the variation of the engine By Pass Ratio and the electrification level of the On-Board Systems are investigated through the MDAO workflow developed for aircraft preliminary design. Finally, the results show a plausible interaction among the disciplines and interesting trends regarding aircraft systems electrification.

Ad-hoc heuristic for design of wind-photovoltaic electrification systems, including management constraints

Isolated electrification systems based on renewable energy are a suitable option for providing many rural communities in developing countries with access to electricity. In particular, the design of wind-photovoltaic systems that combine stand-alone and micro-grid systems has proved an efficient but challenging optimization problem. Decision support tools and solution procedures have been proposed in the literature, most of them focused on techno-economic aspects. However, social aspects related to the management of the systems are a key issue for users’ satisfaction and project sustainability. Only one procedure based on mixed integer linear programming takes the management aspects into account, but excessive computing time may be required or no solutions may be found for non-small communities. Thus, a fast procedure is proposed. The validation is carried out by solving 640 instances, randomly generated from real project characteristics. Our procedure always finds a feasible solution in less than 7 s on average; and even for instances with hundreds of possible locations for equipment, the solutions are found in less than 1 min. Moreover, it finds cheaper solutions than those in the literature. Thus, the procedure represents a very efficient process for optimizing the design of electrification projects considering the technical and management constraints.

Multicriteria-based methodology for the design of rural electrification systems. A case study in Nigeria

Electrification with micro-grids is receiving increasing attention to electrify rural areas in developing countries. However, determining the best local supply solution is a complex problem that requires considering different generation technologies (i.e. solar PV, wind or diesel) and different system configurations (off-grid or on-grid). Most existing decision aid tools to assess this design only consider economical and technical issues in a single optimization process. However, social and environmental considerations have been proven key issues to ensure long-term sustainability of the projects. In this context, the objective of this work is to develop a multicriteria procedure to allow comparing electrification designs with on-grid or isolated micro-grids and different technologies considering multiple aspects. This multicriteria procedure is integrated in a two-phased methodology to assist the design of the system to electrification promoters in a structured process. First, different electrification alternatives are generated with an open-source techno-economic optimization model; next, these alternatives are evaluated and ranked with the multicriteria procedure, which considers 12 criteria representing economic, technical, socio-institutional and environmental aspects. The whole design methodology is validated with a real case study of 26 population settlements in Plateau State, Nigeria. Experts in rural electrification within the Nigerian context have been consulted to weight the criteria and particularize their evaluation for the specific case study. Results show that solar PV technology based systems are the most suitable electrification designs for communities in Nigeria, while grid connection feasibility depends on the size of the community and the distance to the closest national grid consumption point.