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Self-attention reinforcement learning for multi-beam combining in mmW ave 3D-MIMO systems

Science China(Information Sciences) 2023年第6期66卷 204-221页

作者： Yingzhi HUANG Zhaoyang ZHANG Jingze CHE Zhaohui YANG Qianqian YANG Kai-Kit WONG College of Information Science and electronic engineering Zhejiang University department of electronic and electrical engineering University College London

Machine learning(ML)has been empowering all aspects of the wireless communication system design, among which, the reinforcement learning(RL)-based approaches have attracted a lot of research attention since they can interact with the environment directly and learn from the collected experiences efficiently. In this paper, we propose a novel and efficient RL-based multi-beam combining scheme for future millimeter-wave(mmWave)three-dimensional(3D)multi-input multi-output(MIMO)communication systems. The proposed scheme does not require perfect channel state information(CSI)or precise user location information which both are generally difficult to obtain in practice, and well addresses the crucial challenge of computational complexity incurred by the extremely huge state and action spaces associated with multiple users, multiple paths, and multiple 3D beams. In particular, a self-attention deep deterministic policy gradient(DDPG)-based beam selection and combination framework is proposed to learn the 3D beamforming pattern without CSI adaptively. We aim to maximize the sum-rate of the mmWave 3D-MIMO system by optimizing the serving beam set and the corresponding combining weights for each user. To this end, the transformer is incorporated into the DDPG to obtain the global information of the input elements and capture the signal directions precisely, which leads to a near-optimal beamformer design. Simulation results verify the superiority of the proposed self-attention DDPG over conventional ML-based beamforming schemes in terms of sum-rate under various scenarios.

关键词： reinforcement learning (RL) deep deterministic policy gradient (DDPG) self-attention pre-coding/combining millimeter-wave (mmWave) multi-input multi-output (MIMO)

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Statistical analysis and interpretation on lightning impulse breakdown voltages of ester liquids under varying field uniformity

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High Voltage 2024年第1期9卷 22-34页

作者： Haichuan Yu Qiang Liu Zhongdong Wang Department of Electrical and Electronic Engineering The University of ManchesterManchesterUK department of engineering University of ExeterExeterUK

Ester liquids(ELs),as the alternative transformer liquids to the conventional mineral oils(MOs),have been increasingly used in power transformers with high voltage ratings.Among various properties,the lightning impulse breakdown voltages(LIBDVs)have been studied elaborately in the past two decades under different electric field uniformities.The electric field uniformities do have an effect on the breakdown characteristics,for example,breakdown mechanisms,polarity effects,and differences of LIBDV between ELs and MOs,which is quantitatively investigated based on the LIBDVs collected from the literatures.The breakdown mechanism transition phenomenon between streamer initiation dominated breakdown and streamer propagation dominated breakdown has been reviewed firstly.Then,the transition field factor boundaries to observe the polarity effect on LIBDVs are taken at around 20 for ELs and 10 for MOs.Besides,the transition field factor boundaries to observe the LIBDV distinctions between ELs and MOs are about 109 and 14 under positive and negative lightning impulse,respectively.The systematic analysis and interpretation on the transition field factor boundaries among different phenomena can provide insights on insulation design of ELs filled power transformers.

关键词： field lightning breakdown

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Coordination of Networked Nonlinear Multi-Agents Using a High-Order Fully Actuated Predictive Control Strategy

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IEEE/CAA Journal of Automatica Sinica 2022年第4期9卷 615-623页

作者： Guo-Ping Liu IEEE the department of electronic and electrical engineering Southern University of Science and Technology

This paper is concerned with the coordinative control problem of networked nonlinear multi-agents(NNM)with communication delays.A high-order fully actuated(HOFA)model is introduced to describe the nonlinear multi-agents.Based on this model,a HOFA predictive coordination method is proposed to compensate for the communication delays actively and achieve simultaneous stability and consensus.This method largely simplifies the design of networked nonlinear multi-agents and makes the control performance be same for networked nonlinear multi-agents with and without communication delays.The analysis on the closed-loop systems derives the simultaneous stability and consensus criteria of networked nonlinear multiagents using the HOFA predictive coordination method.With the presented way of designing HOFA predictive coordination controllers,a simulated example demonstrates the advantages of the proposed method.

关键词： method nonlinear coordination

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Strategies for improving resilience of regional integrated energy systems in the prevention-resistance phase of integration

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Protection and Control of Modern Power Systems 2023年第2期8卷 167-184页

作者： Jiaqing Wu Jie Gu Shuqi Liu Zhijian Jin department of electrical engineering School of Electronic Information and Electrical EngineeringShanghai Jiao Tong UniversityShanghaiChina

The construction of integrated energy systems can help improve energy efficiency and promote global energy transi-tion.However,in recent years,the occurrence of extreme natural disasters has brought certain threats to the safe and stable operation of the integrated energy system.Thus,it is necessary to improve the ability of the integrated energy system to resist disasters,reduce disaster losses,and restore energy supply as soon as possible,i.e.,improve its resil-ience.Considering the influence of pre-disaster prevention measures and disaster-time operational measures on sys-tem disaster resilience and the correlation between the two,this paper proposes a system hardening strategy based on three-layer robust optimization.The upper layer formulates the optimal hardening strategy of the system before the disaster event occurs,the middle layer identifies the failed elements in the worst disaster situation,while the lower layer realizes the system operational optimization by coordinating the energy storage charging and discharging plan of each subsystem.The strategy can reduce the total supply shortage of the integrated energy system and improve the flexibility of the system in the pre-disaster prevention and disaster resistance integration stages.

关键词： Integrated energy system Natural disasters Prevention–resistance Resilience improvement Robust optimization

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Edge-cloud Computing Systems for Smart Grid: State-of-the-art, Architecture, and Applications

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Journal of Modern Power Systems and Clean Energy 2022年第4期10卷 805-817页

作者： Junlong Li Chenghong Gu Yue Xiang Furong Li department of electronic and electrical engineering University of BathBathUK College of electrical engineering Sichuan UniversityChengduChina

The quantity and heterogeneity of intelligent energy generation and consumption terminals in the smart grid are increasing drastically over the years.These edge devices have created significant pressures on cloud computing(CC)system and centralised control for data storage and processing in realtime operation and control.The integration of edge computing(EC)can effectively alleviate the pressure and conduct real-time processing while ensuring data security.This paper conducts an extensive review of the EC-CC computing system and its application to the smart grid,which will integrate a vast number of dispersed devices.It first comprehensively describes the relationship among CC,fog computing(FC),and EC to provide a theoretical basis for the differentiation.It then introduces the architecture of the EC-CC computing system in the smart grid,where the architecture consists of both hardware structure and software platforms,and key technologies are introduced to support functionalities.Thereafter,the application to the smart grid is discussed across the whole supply chain,including energy generation,transportation(transmission and distribution networks),and consumption.Finally,future research opportunities and challenges of EC-CC while being applied to the smart grid are outlined.This paper can inform future research and industrial exploitations of these new technologies to enable a highly efficient smart grid under decarbonisation,digitalisation,and decentralisation transitions.

关键词： Smart grid edge computing fog computing cloud computing Internet of Things data fusion container technology

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Review on Optimization of Forecasting and Coordination Strategies for Electric Vehicle Charging

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Journal of Modern Power Systems and Clean Energy 2023年第2期11卷 389-400页

作者： Zixuan Jia Jianing Li Xiao-Ping Zhang Ray Zhang department of electronic Electrical and Systems EngineeringSchool of EngineeringUniversity of BirminghamBirminghamUnited Kingdom

The rapid development of electric vehicles(EVs)has benefited from the fact that more and more countries or regions have begun to attach importance to clean energy and environmental protection.This paper focuses on the optimization of EV charging,which cannot be ignored in the rapid development of EVs.The increase in the penetration of EVs will generate new electrical loads during the charging process,which will bring new challenges to local power systems.Moreover,the uncoordinated charging of EVs may increase the peak-to-valley difference in the load,aggravate harmonic distortions,and affect auxiliary services.To stabilize the operations of power grids,many studies have been carried out to optimize EV charging.This paper reviews these studies from two aspects:EV charging forecasting and coordinated EV charging strategies.Comparative analyses are carried out to identify the advantages and disadvantages of different methods or models.At the end of this paper,recommendations are given to address the challenges of EV charging and associated charging strategies.

关键词： Electric vehicle(EV) forecasting aggregator coordination strategy smart charging

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A Review of State-of-the-art Flexible Power Point Tracking Algorithms in Photovoltaic Systems for Grid Support:Classification and Application

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Journal of Modern Power Systems and Clean Energy 2024年第1期12卷 1-21页

作者： Mina Haghighat Mehdi Niroomand Hossein Dehghani Tafti Christopher D.Townsend Tyrone Fernando the department of electrical engineering University of IsfahanIsfahanIran the department of electrical Electronic and Computer EngineeringUniversity of Western AustraliaCrawley WA 6009Australia

To maximize conversion efficiency,photovoltaic(PV)systems generally operate in the maximum power point tracking(MPPT)mode.However,due to the increasing penetra tion level of PV systems,there is a need for more developed control functions in terms of frequency support services and voltage control to maintain the reliability and stability of the power grid.Therefore,flexible active power control is a manda tory task for grid-connected PV systems to meet part of the grid requirements.Hence,a significant number of flexible pow er point tracking(FPPT)algorithms have been introduced in the existing literature.The purpose of such algorithms is to real ize a cost-effective method to provide grid support functional ities while minimizing the reliance on energy storage systems.This paper provides a comprehensive overview of grid support functionalities that can be obtained with the FPPT control of PV systems such as frequency support and volt-var control.Each of these grid support functionalities necessitates PV sys tems to operate under one of the three control strategies,which can be provided with FPPT algorithms.The three control strate gies are classified as:①constant power generation control(CP GC),②power reserve control(PRC),and③power ramp rate control(PRRC).A detailed discussion on available FPPT algo rithms for each control strategy is also provided.This paper can serve as a comprehensive review of the state-of-the-art FPPT algorithms that can equip PV systems with various grid support functionalities.

关键词： Maximum power point tracking(MPPT) flexi ble power point tracking(FPPT) power reserve control(PRC) power ramp rate control(PRRC) low voltage ride-through(LVRT) constant power generation(CPG)

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Impact of Electric Vehicle Aggregator with Communication Time Delay on Stability Regions and Stability Delay Margins in Load Frequency Control System

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Journal of Modern Power Systems and Clean Energy 2021年第3期9卷 595-601页

作者： Ausnain Naveed Sahin Sonmez Saffet Ayasun the Department of Electrical and Electronic Engineering Nigde Omer Halisdemir UniversityNigdeTurkey the Department of Electrical and Electronic Engineering Gazi UniversityAnkaraTurkey

This paper investigates the impact of electric vehicle(EV)aggregator with communication time delay on stability regions and stability delay margins of a single-area load frequency control(LFC)system.Primarily,a graphical method characterizing stability boundary locus is implemented.For a given time delay,the method computes all the stabilizing proportional-integral(PI)controller gains,which constitutes a stability region in the parameter space of PI controller.Secondly,in order to complement the stability regions,a frequency-domain exact method is used to calculate stability delay margins for various values of PI controller gains.The qualitative impact of EV aggregator on both stability regions and stability delay margins is thoroughly analyzed and the results are authenticated by time-domain simulations and quasi-polynomial mapping-based root finder(QPmR)algorithm.

关键词： Communication time delay electric vehicle(EV)aggregator frequency regulation proportional-integral(PI)controller design stability delay margin stability region

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High voltage direct current transmission cables to help decarbonisation in Europe:Recent achievements and issues

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High Voltage 2022年第4期7卷 633-644页

作者： Giovanni Mazzanti department of electrical Electronic and Information EngineeringUniversity of BolognaBolognaItaly

High Voltage Direct Current(HVDC)underground and submarine cables constitute an essential technology for the long-distance transmission of renewable electrical power with low losses,thereby fostering decarbonisation.In the past 2 decades,all this yielded a quasi-exponential rise of HVDC cable systems installed worldwide,but has also made the working conditions of HVDC cables harsher.In this paper,the contribution of HVDC cables to decarbonisation is tackled,with particular reference to the situation in Europe,and a few simple calculations showing in general terms the quantitative contribution provided by HVDC cable systems to decarbonisation are given.Then,the major issues towards long-lasting and reliable HVDC cable systems are summarised briefly,focussing-for the sake of brevity-on the influence of the main HVDC cable technologies,of cable laying environment and of duty service.Some hints are also provided at the chances given by multiterminal HVDC systems.

关键词： cable submarine thereby

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Experimental verification of the potential of superhydrophobic surfaces in reducing audible noise on HVAC overhead line conductors

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High Voltage 2022年第4期7卷 692-704页

作者： Xu Zhang Ian Cotton Qi Li Simon MRowland Christopher Emersic Chengxing Lian Wenyuan Li Department of Electrical and Electronic Engineering The University of ManchesterManchesterUK School of electrical engineering Chongqing UniversityChongqingChina

Overhead line conductors can generate audible noise across a wide frequency spectrum as a result of elevated electric fields at the conductor surface.Such fields are enhanced by the presence of surface defects,insects,water drops and pollution.Within this paper,the impact of a superhydrophobic coating on the audible noise produced by an overhead line conductor is examined.Noise levels from a conductor coated with a superhydrophobic coating were compared to those from a bare conductor in a semi-anechoic chamber.The conductors were energised at voltages to provide surface electric fields ranging from 6 kV/cm to 21 kV/cm(rms).With a continuous water spray system depositing droplets on the conductor surface,the frequency domain sound pressure level,overall sound pressure levels and corona discharge magnitude were measured.It is demonstrated that the use of a superhydrophobic coating reduced audible noise levels and corona discharge magnitude,especially at electric fields above 14 kV/cm.The image analysis suggests that the water drop size distribution and the position of surface droplets on the conductor circumference play an important role in the magnitude of audible noise.

关键词： coating surface potential

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