Hasil untuk "Distribution or transmission of electric power"

J. F. Parisi, A. Diallo

Using a range of fusion power plant (FPP) concepts, we demonstrate that spin-polarized fuel (SPF) can significantly enhance net electric power output, often by many multiples. Notably, the electric power gain from SPF generally exceeds the corresponding increase in thermal fusion power. Plants close to engineering breakeven stand to benefit most, where even modest boosts in fusion power produce disproportionately larger gains in net electricity. As a representative example, a 25% increase in fusion power via SPF could allow an ITER-like device (with an added turbine to recover thermal fusion power) to achieve engineering breakeven. These findings strongly motivate the development of spin-polarized fuel for FPPs.

Chengnian Huang, Zhihao Lan, Menglin L. N. Chen et al.

The PT-symmetric waveguides have been frequently discussed in the photonics community due to their extraordinary properties. Especially, the study of power transmission is significant for switching applications. The aim of this study is to extract the mode power transmission parameters based on the coupled mode equations and analyze the power properties of the PT-symmetric system. The equations relying on the coupled mode theory are constructed according to the two different orthogonality relations between the original and adjoint system. The results matching well with the finite difference simulations demonstrate the validity of our method, while the conventional coupled mode theory fails. The power properties in the PT-symmetric and PT-broken phases are also observed. Furthermore, a new integration is implemented from which the conserved quantity is defined and extracted, which reflects the Hamiltonian invariant of the system. Our method fully incorporates the properties of complex modes and allows the study of the power transmission properties based on the orthogonality relations, which is also applicable to other types of non-Hermitian optical systems. This work provides a new perspective for the power analysis of PT-symmetric waveguides and is helpful to design the switching devices.

Hyeongmeen Baik, Jinia Roy

This paper presents a comprehensive review of dielectric barrier discharge (DBD) power supply topologies, aiming to bridge the gap between DBD applications and power electronics design. Two key aspects are examined: the dependence of the DBD electrical model on reactor geometry, and application-driven requirements for injected waveform characteristics, including shapes, voltage amplitude, frequency, and modulation techniques. On this basis, the paper systematically reviews two major categories of power supplies: sinusoidal types comprising transformerless and transformer-based resonant inverters, and pulsed power supplies (PPSs). The review summarizes performance trade-offs, highlights untested topologies and emerging applications, and offers guidance for advancing high-performance DBD power supply design for next-generation systems.

Ahmed M. Makhzom, K. R. Aissa, Aisha A. Alshanokie et al.

In this study, the carbon dioxide CO2 emission factor for the energy industry sector, which includes the oil and refining industry sector, was estimated by tracing the energy path in its primary form from the AlSharara and Hamada fields to AlZawia Refinery Company to the south of Tripoli power station for generating the electrical power until it reaches the final consumer through the transmission and distribution networks of electric power (electricity consuming sectors). The Life Cycle Assessment (LCA) methodology adopted in this research, which can also apply in all sectors that consume thermal energy such as sectors of transportation and industrial, due to their similarity to all sectors in the first and second stages, and they differ only in the final stage. The research also aims to estimate and collect the quantities of carbon dioxide emitted from the primary energy flow path, from the oil field (upstream) that feeds the oil refinery (downstream), which feeds the power station (infrastructure). The results of the mathematical analysis of data for the energy industry sector showed that to generate 1 megawatt-hour of electricity, 291 kg of diesel oil must be burned, and to obtain this amount of diesel, 1,141 kg of crude oil must be refined. The emitted CO2 chart for this entire pathway was drawn up, where it was found that the total CO2 emitted was around 1253 kg CO2 per MWh. The share of the oil sector from the emitted CO2 was 6.4%, whereas the share of the electricity sector was 93.6%.

Xiaojie Fan, Yongning Chi, Zhibing Wang

Abstract The hybrid cascaded high‐voltage direct‐current (HC‐HVDC) links are recently introduced for ultra‐high voltage bulky power transmissions. However, as wind power becomes more prevalent, the grid is gradually weakened and will face voltage stability issues. This paper proposes a coordinated reactive power control strategy for HC‐HVDC links to enhance the voltage stability of AC bus. Firstly, the impact of HC‐HVDC on the static voltage stability of the AC bus is studied by the voltage sensitivity coefficient. Then, the limitation of reactive power capability of modular multilevel converter in the HC structure is identified. Based on the analysis results, a coordinated reactive power control strategy based on adaptive voltage droop is proposed. In the strategy, the DC voltage ratio is regulated according to the fluctuation degree of the AC bus voltage to adjust the reactive power of HC‐HVDC, which realized the dynamic voltage support for the AC bus. Finally, electromagnetic simulations in power systems computer aided design (PSCAD)/electromagnetic transients including DC (EMTDC) are performed, and the results validate the theoretical findings and the effectiveness of the control strategy.

Lun Dong, Yuan Huang, Xiao Xu et al.

Abstract The variability of renewable energy within microgrids (MGs) necessitates the smoothing of power fluctuations through the effective scheduling of internal power equipment. Otherwise, significant power variations on the tie‐line connecting the MG to the main power grid could occur. This study introduces an innovative scheduling strategy that utilizes a data‐driven approach, employing a deep reinforcement learning algorithm to achieve this smoothing effect. The strategy prioritizes the scheduling of MG's internal power devices, taking into account the stochastic charging patterns of electric vehicles. The scheduling optimization model is initially described as a Markov decision process with the goal of minimizing power fluctuations on the interconnection lines and operational costs of the MG. Subsequently, after preprocessing the historical operational data of the MG, an enhanced scheduling strategy is developed through a neural network learning process. Finally, the results from four scheduling scenarios demonstrate the significant impact of the proposed strategy. Comparisons of reward curves before and after data preprocessing underscore its importance. In contrast to optimization results from deep deterministic policy gradient, soft actor‐critic, and particle swarm optimization algorithms, the superiority of the deep deterministic policy gradient algorithm with the addition of a priority experience replay mechanism is highlighted.

Yuling Wang, Vijay Vittal

In recent years, there has been an increasing need for effective voltage control methods in power systems due to the growing complexity and dynamic nature of practical power grid operations. To enhance the controller’s resilience in addressing communication failures, a dynamic voltage control method employing distributed execution multi-agent deep reinforcement learning(DRL) is proposed. The proposed method follows a centralized training and decentralized execution based approach. Each agent has independent actor neural networks to output generator control commands and critic neural networks that evaluate command performance. Detailed dynamic models are integrated for agent training to effectively capture the system’s dynamic behavior following disturbances. Subsequent to training, each agent possesses the capability to autonomously generate control commands utilizing only local information. Simulation outcomes underscore the efficacy of the distributed execution multi-agent DRL controller, showcasing its capability in not only providing voltage support but also effectively handling communication failures among agents.

Changyue Zou, Junjie Feng, Xiaobin Zhao et al.

Abstract It has been known that resonances often occur when high‐voltage direct current (HVDC) systems are connected into the AC system via voltage‐source converters (VSCs). The resonances may lead to system failure and even damage primary equipment under some severe conditions. However, the existing damping methods are inadequate to ensure the system is always stable. To solve it, this article introduces the passive impedance adapter (PIA) in parallel with VSC to compensate the negative impedance of VSC‐HVDC system especially at mid‐ and high‐frequency ranges. A novel design and implementation method for the PIA is then proposed with the reduced volume and power loss to ensure the whole system impedance always positive. By this way, no resonance exists and the system is stable under any practical condition, such as the different cable lengths and impedances. Finally, a simulation platform is built to verify the effectiveness of the proposed PIA method in compensating the VSC‐HVDC impedance.

Lucas Pereira, Vineet Jagadeesan Nair, Bruno Dias et al.

We propose a comprehensive approach to increase the reliability and resilience of future power grids rich in distributed energy resources. Our distributed scheme combines federated learning-based attack detection with a local electricity market-based attack mitigation method. We validate the scheme by applying it to a real-world distribution grid rich in solar PV. Simulation results demonstrate that the approach is feasible and can successfully mitigate the grid impacts of cyber-physical attacks.

Arash Rohani, Ali Nahavandi, Mahyar Abasi et al.

Abstract This paper presents the optimal scheduling of active distribution network (ADN) with linear and non‐linear loads in the presence of an integrated unit of electric spring and electric vehicle parking lot (IUEE). The proposed scheme is formulated in the form of three‐objective optimization, which minimizes the expected operating cost of the ADN, voltage deviation function (VDF), and the total harmonic distortion (THD) of the voltage in separate objective functions. Constraints include harmonic power flow (HPA) equations, operation and power quality limits, and operation model of the IUEE. This scheme has uncertainties of load, energy price, and energy demand of EVs, which are modelled here using stochastic programming. Next, the sum of the weighted functions method as a subset of the Pareto optimization technique is adopted to extract the integrated single‐objective problem. Then, Sine‐Cosine Combined Algorithm (SCA) and Gray Wolf Optimization (GWO) are used to achieve an optimal solution. In the end, by examining the numerical results obtained from the implementation of the proposed scheme on a 69‐bus ADN, the capability of the design in enhancing the economic situation, operation, and power quality of the ADN compared to network power flow studies obtained by optimal scheduling of the IUEE is confirmed.

Siqi Lin, Wei Yao, Yongxin Xiong et al.

Abstract This paper presents an open‐access Matlab/Simulink‐based power system simulation toolbox (MatPSST) for research and education. In MatPSST, dynamic modeling is implemented by Simulink. Only the initialization process is coded in Matlab. This structure makes full use of Simulink, enabling users to fully use the rich solvers and built‐in toolboxes in Matlab/Simulink, such as small‐signal analysis, without additional programming. The interaction with real‐time platforms like RTLAB and dSPACE in MatPSST is convenient through the Simulink interface. In addition, MatPSST provides a uniform interface and flexible framework for user‐defined functions. Users do not need to consider the interaction between models and dynamic solvers when implementing state‐of‐the‐art user‐defined models. To avoid the heavy work (replicate units and change parameters) in modeling detailed wind farm or photovoltaic station with hundreds of renewable generation units, the idea of the vector‐variable‐based model is proposed with MatPSST. Case studies introduce some selected application examples of MatPSST in research and education and demonstrate its accuracy by the comparisons with Simscape and PSAT. The cases reveal the advantages of MatPSST in promoting power system research and education.

Yifeng Zhao, Gang Liu, Yaodong Guo et al.

Abstract An explosion accident in an enclosed cable trench caused by the discharge of 10 kV three‐phase cable joints is discussed. Combined with the disassembly analysis, the fault recording data analysis, and the validation of experiment, the evolution of the cable joint fault is deduced and discussed. The results show that the trigger of the cable joint fault is the creepage discharge at the cross‐linked polyethylene–silicon rubber insulation interface. This results in the partial breakdown and the grounding failure of three‐phase cable joints. Under the long‐term floating potential and current thermal effect, the insulations are gradually ablated and decomposed into a large amount of combustible gas. Finally, the accumulated combustible gas is ignited by the arc caused by a three‐phase short circuit at the moment of the reclosing operation. The analytical method and conclusions proposed in this paper can provide suggestions and guidance to prevent analogous distribution network cable joint fault accidents.

Liu Zhiren, Tong Weilin, Xue Mingjun et al.

Abstract With the high penetration of distributed generation and gradual increase in loop network structures, existing over‐current protection in distribution networks is difficult to apply. The use of current differential protection has become an ideal solution, and high performance and commercialization of 5G communication provides an effective way to solve the problem of differential protection channel transmission. Aiming at distribution network differential protection based on 5G, this paper adopted an adaptive frequency conversion transmission mechanism to significantly reduce the data flow of differential protection. In terms of protection strategy, the differential allowable signal and the differential protection startup logic are separated, and a novel action method and protection logic suitable for weak infeed distribution networks are proposed. The strategy significantly shortens the protection action time under wireless communication. Furthermore, a comprehensive synchronization scheme using zero‐crossing synchronization of forward sampling points and cycle numbers based on the second pulse signal was established. This scheme can effectively improve the reliability of data synchronization for differential protection. Finally, the method proposed in this study was verified using the dynamic model experiment of real‐time digital simulation (RTDS).

Runyu Fu, Jianguo Wang, Jianping Wang et al.

Abstract The operation of disconnectors in gas insulated substation (GIS) or power plant will produce very fast transient overvoltage (VFTO), which is considered to have serious harm to transformer longitudinal insulation and other high‐voltage equipment insulation. VFTO may also lead to secondary circuit failure. In this paper, the holistic modelling of 500 kV GIS step‐up substation equipment with a double circuit and long GIS busbar in a coastal power plant is established using Electromagnetic Transient Program (EMTP). The authors calculated the VFTO waveform that may be generated in different operations of the GIS substation. The authors analyze the amplitude and frequency characteristics of the VFTO waveform at lightning arresters and the entrance of transformers and find that the amplitude of VFTO at the entrance of #1 MT is less than its impulse withstand voltage. In some cases, the VFTO waveform at the entrance of #1 MT has high‐frequency content with fast attenuation. The VFTO waveform generated when operating the disconnector close to the arrester will cause the arrester to act many times and count frequently in a short time.

Xueping Gu, Yansong Bai, Shaoyan Li et al.

Abstract Disturbance‐resisting ability (DRA) of the restored network needs to be considered when making a restoration scheme of power systems, to ensure system security and reduce secondary blackout risk. This paper proposes an optimisation method of whole‐process restoration decision‐making with DRA of the restored network in consideration. Firstly, a load rate balance (LRB) index of the restored network is defined to represent the DRA index during restoration. Then, an optimisation model of whole‐process restoration decision‐making is established, considering the LRB index of the restored system. To solve the model by a linear programming method, the non‐linear terms in the model are transformed into linear forms. Finally, a time‐step decoupling method to reduce solving difficultness of the established model with the LRB index is derived, with purpose of accelerating the solving process. The numerical results of the IEEE 30‐bus system and a practical power system verify effectiveness of the proposed method to obtain a restoration scheme to balance the system restoration benefit and security.

D. R. Weerakoon, C. Karawita, U. D. Annakkage

Series compensation of transmission lines increase the risk of Sub-Synchronous Resonance (SSR) problems. Use of Thyristor Controlled Series Compensators (TCSC) in place of Fixed Series Capacitors (FSC) has benefited in terms of damping SSR. SSR Damping with TCSC can be achieved with supplementary controls or through its inherent damping capability. Use of discrete time models for small signal stability analysis of TCSC is well established. This paper uses a simplified Dynamic Phasor (DP) model of the TCSC for an in-depth evaluation of the inherent SSR damping capability through small signal stability analysis. Source of inherent damping in open loop operation and the representation of it in the DP model is elaborated and the small signal model is validated against Electro Magnetic Transient (EMT) simulations. Effect of inductive-resistive nature of the TCSC on Induction Generator Effect (IGE) and Torsional Interactions (TI) is shown through small signal stability assessment. It is shown that the network resonant frequency exists only in a narrow range of firing angles of the TCSC and thus IGE and TI are avoided in most part of its operating range. IEEE first benchmark system for SSR studies is used to demonstrate the inherent damping capability of a TCSC.

Ziyi Yue, Huazhi Liu, Yonggang Li et al.

Abstract The low‐carbon development of integrated energy systems is achieved via the sharing of multiple energy interactions by park‐level IES (PIES).However, coordinating profit distribution conflicts among complex interactive stakeholders in stochastic scenarios is challenging. Accordingly, this study proposes a novel tri‐layer framework that aggregates different game mechanisms to investigate the interactions between PIESs and coupled energy markets. First, a linkage trading mechanism is proposed by integrating carbon emissions trading and green certificate trading, which establishes a coupled electricity‐carbon‐green certificate market. Consequently, a park aggregation operator acts as an intermediary between PIESs and the coupled market, setting upper‐level purchase and sale prices to guide unit generation in each PIES using the Stackelberg game theory. Subsequently, the Nash game theory is applied to realize cooperative bargaining among PIESs for a fair revenue distribution. Further, the impact of uncertain environments is considered by utilizing stochastic scenario methods and the conditional value‐at‐risk theory. To protect the privacy of each participating agent while improving the convergence speed, a differential evolutionary method is combined with analysis target cascading to solve the framework. Finally, the proposed scheduling method is validated by utilizing a typical case to optimize conflicting PIES interests in multiple scenarios and realize decarbonisation.

Yasin Pezhmani, Morteza Zare Oskouei, Navid Rezaei et al.

Abstract This paper deals with the real‐time optimal operation of active distribution networks (ADNs) hosting hybrid hydrogen‐electricity refuelling stations by benefiting from renewable energy sources (RESs), conversion facilities, and energy storage systems. The hybrid refuelling stations, which are controlled by ADN operator, supply electricity and hydrogen for electric vehicles (EVs) and hydrogen vehicles (HVs), respectively. In addition, the deployment of water equipment technologies in the ADNs, is considered by utilizing water well pumps in the hybrid stations to serve water demand. The principal aim is to minimize the expected operation cost, including the cost of purchasing power from the upstream grid and maintenance and operation costs of each hybrid refuelling station. Various technical and physical constraints are considered to ensure the reliable operation and realistic scheduling of ADNs in the presence of hybrid refuelling stations. This study employs a hybrid information gap decision theory (IGDT)‐stochastic approach to address the uncertain behaviour of wholesale market price, electricity demand of EVs in refuelling stations, RESs output power and nodal demand of ADN to reach a risk‐averse strategy. The developed approach is coded under GAMS software and the effectiveness of the approach is validated by testing on the modified IEEE 33‐bus test system.

Lang Li, Zhaoxu Luo, Peng Tian et al.

Abstract A hybrid series‐parallel microgrid structure and its distributed decentralized cooperative control strategy are introduced in this paper. In the hybrid series‐parallel microgrids, the distributed generators (DGs) are concatenated in parallel to form a paralleled‐connected generation (PCG) module. Further, the hybrid series‐parallel microgrids consist of multiple PCG modules in series. For the considered microgrids, a distributed decentralized cooperative control strategy is proposed. For DGs in the same PCG module, low‐bandwidth communications are applied to obtain convergence control of the system. Meanwhile, different PCG modules realize autonomous synchronization in a communication‐free manner. Thus, the proposed distributed decentralized cooperative control method is a low‐bandwidth communication approach. Moreover, it is immune to single‐point fault and communication failure. Finally, the feasibility of the proposed controller for the considered microgrids is verified by stability and simulations.

Chuanqing Xu, Kedeng Cheng, Yu Wang et al.

Tuberculosis (TB) is an infectious disease transmitted through the respiratory system. China is one of the countries with a high burden of TB. Since 2004, an average of more than 800,000 cases of active TB have been reported each year in China. Analyzing the case data from 2004-2018, we find significant differences in TB incidence by age group. Therefore, the effect of age heterogeneous structure on TB transmission needs further study. We develop a model of TB to explore the role of age heterogeneity as a factor in TB transmission. The model is fitted numerically using the nonlinear least squares method to obtain the key parameters in the model, and the basic reproduction number Rv 0.8017 is calculated and the sensitivity anal-ysis of Rv to the parameters is given. The simulation results show that reducing the number of new infections in the elderly population and increasing the recovery rate of elderly patients with the disease could significantly reduce the transmission of tuberculosis. Furthermore the feasibility of achieving the goals of the WHO End TB Strategy in China is assessed, and we obtain that with existing TB control measures it will take another 30 years for China to reach the WHO goal to reduce 90% of the number of new cases by year 2049. However, in theoretical it is feasible to reach the WHO strategic goal of ending tuberculosis by 2035 if the group contact rate in the elderly population can be reduced though it is difficulty to reduce the contact rate.