Showing papers on "Electric power published in 2022"

Distributed Real-Time Dispatch of Integrated Electricity and Heat Systems With Guaranteed Feasibility

Abstract: Due to the distributed structure of electric power networks (EPNs) and district heating networks (DHNs), distributed dispatch is favorable for coordination in an integrated electricity and heat system (IEHS). However, the feasibility issue of the dispatch solution remains unresolved. Without making this clear, critical threats may be posed to system operation, and there cannot be security guarantees. In this article, we propose a distributed method for real-time IEHS dispatch where feasibility is strictly ensured in each iteration. First, a network reduction method of DHNs retaining the temperature quasi-dynamics is derived. Based on that, a novel feasibility cut (FC) generation method is devised, which strictly maintains system security during the iterative process. Finally, modified Benders decomposition with guaranteed feasibility (MBD-GF) is proposed to tackle distributed IEHS dispatch. The case studies of two IEHSs validate the effectiveness and efficiency of the proposed method.

Study and Analysis of Power Quality in the Electrical Networks of the Outdoor Lighting of the Dushanbe City

Abstract: At present, attention to the power quality in electrical networks has increased significantly. This is connected with increasing in the quantity and power of the electrical receivers with non-linear volt-ampere characteristics. If earlier traditional lamps were used for outdoor lighting of cities, now the quantity of energy-saving lamps, which are sources of higher harmonic of current components, has increased. As it is known, deterioration of Power Quality negative consequences the elements of electrical networks. Therefore, the authors carried out instrumental measurements have been implemented on the electrical networks of the outdoor lighting in the Dushanbe city to analyze and identify the causes of power quality deterioration. This article provides results of the instrumental assessment of the power quality are also presented and explains the possible causes and consequences of the registered violations to define and mitigate power quality disturbances.

Distributed power generation planning for distribution networks using electric vehicles: Systematic attention to challenges and opportunities

Abstract: Electric vehicular distributed generation are increasingly essential for distribution network strategy. In recent years, electric car management and general administration have become more essential in the electric distribution sector. This article discusses several optimization strategies for distributed generation, electric vehicles, and distributed generations employing electric vehicles programs in power distribution systems with diverse load models. Conventional optimization methods, artificial intelligence, hybrid approaches, and advanced optimization methods for planning are the five kinds of optimization techniques. The plan considers the system's many features and distinct components of the system's intended purpose, such as decreasing real and reactive power losses. This paper also gives an overview of existing models and approaches that applicable to the distributed generation with electric vehicles may use when planning, assessing and categorizing present and future research trends in this subject. Researchers, enterprises, academics, and scientists will benefit significantly from this review article, according to the authors, because it will allow them to accurately identify references in the same topic.

A high-efficient triboelectric-electromagnetic hybrid nanogenerator for vibration energy harvesting and wireless monitoring

Abstract: Scavenging mechanical vibration energy by combining triboelectric nanogenerators (TENGs) and electromagnetic generators (EMGs) is a renewable and low-carbon way to generate electric power. In this paper, we fabricate a cylindrical structure hybrid nanogenerator based on spring structure to effectively scavenge vibration energy. The introduction of spring structure not only enhances the space utilization, but also supports the moving magnet. Owing to its innovative structure, the instantaneous output power of TENG and EMG are 0.88 mW at a load of 10 MΩ and 216.7 mW at a load of 60 Ω, respectively. With the aids of a power management circuit, the hybrid nanogenerator can provide continuous power for two hygrothermographs connected in series. In addition, a self-powered wireless acceleration sensing monitoring system (SWAM) is developed to measure the acceleration signals of vibration sources. This study provides a novel guideline for harvesting mechanical vibration energy.

Optimal design of electrical power distribution grid spacers using finite element method

Abstract: Spacers in the compact power distribution network are essential components for the support, organization, and spacing of conductors. To improve the reliability of these components and have an optimized network design, it is necessary to evaluate the performance of the variation of their geometric parameters. The analysis of these components is fundamental, considering that there are several models available that are validated by the electric power utilities. Due to the various possible design shapes, it is necessary to use an optimized model to reduce the electric potential located in specific sites, improving the reliability in the component, as the higher electrical potential results in a greater chance of failure to occur. The finite element method (FEM) stands out for evaluating the distribution of electrical potential. In this paper, an FEM is used to evaluate variations in vertical and horizontal dimensions in spacers used in the 13.8 kV power grid. The models are analyzed in relation to their behavior regarding the potential distribution on their surface. From the results of these variations, the model is optimized by means of a mixed-integer linear problem (MILP), replacing the FEM output with a ReLU network substitute model, to obtain a spacer with more efficiency to be used in semi-insulated distribution networks.

Short Term Electric Power Load Forecasting Using Principal Component Analysis and Recurrent Neural Networks

Abstract: Electrical load forecasting study is required in electric power systems for different applications with respect to the specific time horizon, such as optimal operations, grid stability, Demand Side Management (DSM) and long-term strategic planning. In this context, machine learning and data analytics models represent a valuable tool to cope with the intrinsic complexity and especially design future demand-side advanced services. The main novelty in this paper is that the combination of a Recurrent Neural Network (RNN) and Principal Component Analysis (PCA) techniques is proposed to improve the forecasting capability of the hourly load on an electric power substation. A historical dataset of measured loads related to a 33/11 kV MV substation is considered in India as a case study, in order to properly validate the designed method. Based on the presented numerical results, the proposed approach proved itself to accurately predict loads with a reduced dimensionality of input data, thus minimizing the overall computational effort.

All-Electric NASA N3-X Aircraft Electric Power Systems

Abstract: In this paper, turboelectric NASA N3-X aircraft is fully electrified for the first time; engines are removed and the all-electric NASA N3-X aircraft electric power system (EPS) is introduced, supplied by four electrochemical energy units (EEU) including batteries, fuel cells, and supercapacitors. In this regard, three medium voltage direct current (MVDC), ±5 kVdc, bipolar EPS architectures are proposed for the aircraft, discussed, and analyzed in detail by performing power flow (PF) analysis. Proposed architectures are also considered as 3-phase AC, 10 kVac, EPSs and discussed and analyzed in detail for comparison. To perform PF analysis for proposed MVDC EPSs, two PF solvers for dc networks under constant power generations and loads are also modified and developed. Potential cable conductors are selected and hints are provided to choose final conductors; to assess the performance of selected conductors, dimensions of the aircraft are estimated and cable parameters are calculated based on presented dimensions. Proposed EPS architectures meet power system planning criteria under normal condition as well as all n-1 contingencies. This article aims to assess newly designed EPSs and, therefore, assumptions are made about EEUs and propulsion motors to the extent whereby PF analysis is affected.

Wavelet LSTM for Fault Forecasting in Electrical Power Grids

Abstract: An electric power distribution utility is responsible for providing energy to consumers in a continuous and stable way. Failures in the electrical power system reduce the reliability indexes of the grid, directly harming its performance. For this reason, there is a need for failure prediction to reestablish power in the shortest possible time. Considering an evaluation of the number of failures over time, this paper proposes performing failure prediction during the first year of the pandemic in Brazil (2020) to verify the feasibility of using time series forecasting models for fault prediction. The long short-term memory (LSTM) model will be evaluated to obtain a forecast result that an electric power utility can use to organize maintenance teams. The wavelet transform has shown itself to be promising in improving the predictive ability of LSTM, making the wavelet LSTM model suitable for the study at hand. The assessments show that the proposed approach has better results regarding the error in prediction and has robustness when statistical analysis is performed.

Nighttime electric power generation at a density of 50 mW/m² via radiative cooling of a photovoltaic cell

Abstract: A large fraction of the world's population lacks access to the electric grid. Standard photovoltaic (PV) cells can provide a renewable off-grid source of electricity but only produce power from daytime solar irradiance and do not produce power at night. While there have been several theoretical proposals and experimental demonstrations of energy harvesting from the radiative cooling of a PV cell at night, the achieved power density is very low. Here, we construct a device, which incorporates a thermoelectric generator that harvests electricity from the temperature difference between the PV cell and the ambient surrounding. We achieve 50 mW/m 2 nighttime power generation with a clear night sky, with an open-circuit voltage of 100 mV, which is orders of magnitude higher as compared with previous demonstrations. During the daytime, the thermoelectric generator also provides additional power on top of the electric power generated directly from the PV cells. Our system can be used as a continuous renewable power source for both day- and nighttime in off-grid locations.

Low-Carbon Transformation of Electric System against Power Shortage in China: Policy Optimization

Abstract: The low-carbon transition of the power system is essential for China to achieve peak carbon and carbon neutrality. However, China could suffer power shortages due to radical policies in some extreme cases. The gap between power demand and supply from March 2021 to November 2021 ranged between 5.2 billion kW·h and 24.6 billion kW·h. The main reason for the power shortage was over-reliance on renewable energy and insufficient coal power supply for the power system. The low-carbon transformation path of the electric system needs to be explored with more flexibility for power security. This study applied a modified LEAP model and carried out a forecast analysis of thermal power generation and installed capacity in 2025 and 2030 under normal and extreme weather scenarios. The results suggested that: the installed capacity of thermal power will need to account for about 44.6–46.1% of power generation in 2025 and 37.4–39.3% in 2030, with the assumption of power shortages caused by the instability and uncertainty of renewable power. In the future, China needs to pursue the development of diversified energy sources and enhance the power supply security capability while strengthening the development and utilization of renewable energy.

A Performance Evaluation of Three-Phase Induction Electric Motors between 1945 and 2020

Abstract: In the late 19th century, the three-phase induction motor was the central element of productivity increase in the second industrial revolution in Europe and the United States. Currently, it is the main load on electrical systems in global terms, reaching approximately 70% of electrical energy consumption in the industrial sector worldwide. During the 20th century, electric motors underwent intense technological innovations that enabled significant performance gains. Thus, this work analyses the performance changes in squirrel-cage rotor three-phase induction electric motors (SCIMs) with mechanical powers of 3.7 kW, 37 kW, and 150 kW and speed ranges corresponding to two poles and eight poles, connected to a low voltage at a frequency of 60 Hz and tested between 1945 and 2020. The study confirms accumulated performance gains of above 10% in some cases. Insulating materials for electrical conductors have gone through several generations (cotton, silk, and currently, varnish). Improvements to the housing for cooling, the bearings, the quality of active materials, and the design were the elements that enabled the high gains in performance. The first commercial two-pole SCIM with a shaft power of 4.4 kW was marketed in 1891, with a weight/power ratio of 86 kg/kW, and until the 2000s, this value gradually decreased, eventually reaching 4.8 kg/kW. Between 2000 and 2020, this ratio showed a reversed trend based on improvements in the performance of SCIMs. More active materials were used, causing the weight/power ratio to reach 8.6 kg/kW. The MEPS (minimum energy performance standards) of SCIMs had an essential role in the performance gain over the last three decades. Data collection was via tests at the Electrical Machines Laboratory of the Institute of Energy and Environment of the University of São Paulo. The laboratory has a history of tests on electrical equipment dating from 1911.

Wavelet Long Short-Term Memory to Fault Forecasting in Electrical Power Grids

Abstract: The electric power distribution utility is responsible for providing energy to consumers in a continuous and stable way, failures in the electrical power system reduce the reliability indexes of the grid, directly harming its performance. For this reason, there is a need for failure prediction to reestablish power in the shortest possible time. Considering an evaluation of the number of failures over time, this paper proposes to perform a failure prediction during the first year of the pandemic in Brazil (2020) to verify the feasibility of using time series forecasting models for fault prediction. The Long Short-Term Memory (LSTM) model will be evaluated to obtain a forecast result that can be used by the electric power utility to organize the maintenance teams. The Wavelet transform shows to be promising in improving the predictive ability of the LSTM, making the Wavelet LSTM model suitable for the study at hand. The results show that the proposed approach has better results regarding the evaluation of the error in prediction and has robustness when a statistical analysis is performed.