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power Flow Model for Medium-voltage Distribution Systems Considering Measurement and Structure Characteristics

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Journal of Modern power Systems and Clean Energy 2024年第2期12卷 571-583页

作者： Zhengmei Lu Wei Yan Dezhi Huang Junjie Tang Ferdinanda Ponci Antonello Monti state Key Laboratory of power Transmission Equipment&System Security and New Technology Chongqing UniversityChongqing 400044China state grid Zhejiang Yiwu power supply company State Grid Zhejiang Electric Power CompanyYiwu 322001China Institute for Automation of Complex power Systems of the E.ON Energy Research Center at RWTH Aachen University Aachen52074Germany Digital Energy Fraunhofer FIT Aachen52072Germany IEEE

Medium-voltage distribution systems(MVDSs)mainly consist of a feeder head,lines,distribution transformers,and the equivalent load or power supply interfaced with the distribution transformers.The information of such load or power supply can be measured via the three-wattmeter method(THM)and the two-wattmeter method(TWM).The measurements can be used to perform the control of the power supply and simulate the characteristics of the load,so the models of the load and the power supply need to consider the measurement characteristics.Existing research works on three-phase power flow(PF)just consider the measurement characteristics of THM.Hence,the PF equation of the bus measured via TWM is firstly built.Based on conventional measurements,an accurate and general model of the grounded and ungrounded slack bus is proposed.Furthermore,the influence arising from the connection type and angle shift of distribution transformers on the admittance matrix is considered,and thus a general three-phase transformer model is summarized,which is applicable for all the transformers mentioned herein.Finally,Newton's method is adopted to solve the PF calculation,and the performance of the proposed PF model is demonstrated through designed tests.

关键词： Medium-voltage distribution system three-phase power flow calculation measurement characteristic slack bus modeling distribution transformer

Real-Time Energy Management for Net-Zero power Systems Based on Shared Energy Storage

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Journal of Modern power Systems and Clean Energy 2024年第2期12卷 371-380页

作者： Pengbo Du Bonan Huang Ziming Liu Chao Yang Qiuye Sun School of Information Science and Engineering Northeastern UniversityShenyang 110004China Information and Communication branch State Grid Liaoning Electric Power Company Ltd.Shenyang 110004China IEEE

Battery energy storage systems(BESSs)serve a crucial role in balancing energy fluctuations and reducing carbon emissions in net-zero power systems.However,the efficiency and cost performance have remained significant challenges,which hinders the widespread adoption and development of BESSs.To address these challenges,this paper proposes a real-time energy management scheme that considers the involvement of prosumers to support net-zero power systems.The scheme is based on two shared energy storage models,referred to as energy storage sale model and power line lease model.The energy storage sale model balances real-time power deviations by energy interaction with the goal of minimizing system costs while generating revenue for shared energy storage providers(ESPs).Additionally,power line lease model supports peer-to-peer(P2P)power trading among prosumers through the power lines laid by ESPs to connect each prosumer.This model allows ESP to earn profits from the use of power lines while balancing power deviations and better consuming renewable energy.Experimental results validate the effectiveness of the proposed scheme,ensuring stable power supply for net-zero power systems and providing benefits for both the ESP and prosumers.

关键词： Shared energy storage energy storage provider(ESP) energy management peer-to-peer(P2P)trading net-zero power system

Dispersed Wind power Planning Method Considering Network Loss Correction with Cold Weather

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Energy Engineering 2024年第4期121卷 1027-1048页

作者： Hanpeng Kou Tianlong Bu Leer Mao Yihong Jiao Chunming Liu Hulunbeier power supply company State Grid Inner Mongolia East Power Co.Ltd.Hulunbeier021100China College of electrical and Electronic Engineering North China Electric Power UniversityBeijing102206China

In order to play a positive role of decentralised wind power on-grid for voltage stability improvement and loss reduction of distribution network,a multi-objective two-stage decentralised wind power planning method is proposed in the paper,which takes into account the network loss correction for the extreme cold region.Firstly,an electro-thermal model is introduced to reflect the effect of temperature on conductor resistance and to correct the results of active network loss calculation;secondly,a two-stage multi-objective two-stage decentralised wind power siting and capacity allocation and reactive voltage optimisation control model is constructed to take account of the network loss correction,and the multi-objective multi-planning model is established in the first stage to consider the whole-life cycle investment cost of WTGs,the system operating cost and the voltage quality of power supply,and the multi-objective planning model is established in the second stage.planning model,and the second stage further develops the reactive voltage control strategy of WTGs on this basis,and obtains the distribution network loss reduction method based on WTG siting and capacity allocation and reactive power control strategy.Finally,the optimal configuration scheme is solved by the manta ray foraging optimisation(MRFO)algorithm,and the loss of each branch line and bus loss of the distribution network before and after the adoption of this loss reduction method is calculated by taking the IEEE33 distribution system as an example,which verifies the practicability and validity of the proposed method,and provides a reference introduction for decision-making for the distributed energy planning of the distribution network.

关键词： Decentralised wind power network loss correction siting and capacity determination reactive voltage control two-stage model manta ray foraging optimisation algorithm

Influence of thermal ageing on high-field polarisation characteristics and conductivity behaviour of submarine polymeric cables insulation

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High Voltage 2023年第1期8卷 138-148页

作者： Xize Dai Jian Hao Gian Carlo Montanari Zheng Jian Ruijin Liao Xinlong Zheng state Key Laboratory of power Transmission Equipment&System Security and New Technology Chongqing UniversityChongqingChina Department of Energy Aalborg UniversityAalborgDenmark Center for Advanced power Systems Florida State UniversityTallahasseeFloridaUSA shinan power supply branch company of state grid chongqing electric power company NananChina Zhoushan power supply branch company of state grid Zhejiang electric power company ZhoushanChina

Diagnosing insulation intrinsic ageing is essential for preventing insulation failure of submarine cables,and in case of failure,helping in any decision about maintenance actions.In this study,a novel aged cable diagnosis approach based on high-voltage frequency domain spectroscopy(HV-FDS)with broader frequency width is proposed to analyse the high-field polarisation characteristics and conductivity behaviour of 500 kV submarine polymeric cables insulation,aiming to support the evaluation of overall insulation ageing.The measurement principle of HV-FDS and relaxation mechanism are stated,and then focus is on studying the extent of change of polarisation and conduction properties of submarine cables insulation as a function of ageing stress and time.Moreover,the high-field polarisation characteristics and conductivity behaviour are discussed in-depth based on the carrier transport and trap properties.Finally,the novel diagnostic indicator based on the high-field characteristics is extracted to quantify the thermal ageing state of submarine cables insulation.Results show that the high-field polarisation characteristics and conductivity behaviour seem to become sensitive diagnostic quantities if measured at reasonably high voltage,which are able to reveal mechanisms associated with thermo-oxidative ageing as that generated in the testing procedure considered in this paper.Sensitivity is considerably higher than that experienced in typical dielectric spectroscopy approaches.

关键词： behaviour insulation characteristics

A novel high-voltage solid-state switch based on the SiC MOSFET series and its overcurrent protection

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High Voltage 2023年第4期8卷 698-706页

作者： Dazhao He Wenjie Sun Yixin Liao Penghao Zhang Liang Yu Shoulong Dong Chenguo Yao Xin liu state Key Laboratory of power Transmission Equipment and System Security and New Technology School of Electrical EngineeringChongqing UniversityChongqingChina Rizhao power supply company State Grid Shangdong Electric Power CompanyRizhaoChina

All-solid-state switches are one of the core components of pulsed power supply systems.However,the voltage level of a single switch is limited.By optimizing the chip structure,the voltage level of a single switch can be improved.Due to the immaturity of the production process and the positive correlation between the blocking voltage and the onresistance of the switch,it is difficult to improve the blocking voltage and the continuous forward current of a single switch simultaneously.The series-connected switch is a way to increase the switch's blocking voltage without reducing the switch's continuous forward current.Magnetically coupled isolated drive and resistor-capacitor forced voltage equalization techniques are investigated to increase the blocking voltage of the switches using multiple SiC metal-oxide-semiconductor field-effect transistors(MOSFETs)in series connections.Meanwhile,a special overcurrent protection scheme is designed to improve the reliability of the series-connected switch.Finally,a high-voltage solid-state switch is developed based on the SiC MOSFET series connections,whose output pulse width is adjustable from 20 to 300μs,frequency is adjustable from 1 Hz to 3 kHz,the maximum output voltage can reach 57 kV(1 Hz),and the overcurrent protection time is about 1μs.

关键词： series state solid

High‐altitude tunnel‐catenary gap impulse discharge characteristics and breakdown voltage correction

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High Voltage 2023年第6期8卷 1285-1295页

作者： Yi Liao Xingliang Jiang Guolin Yang Jianlin Hu Zhijin Zhang Qin Hu Chen Tan Haitao Wu Xuefeng Mountain Energy Equipment Safety National Observation and Research Station of chongqing University ChongqingChina state grid Chengdu power supply company ChengduChina state grid chongqing electric power Research Institute ChongqingChina

Air gap impulse discharge characteristics of railway tunnel‐catenary at high‐altitude are of great significance to the electrical insulation design.The existing altitude correction methods for non‐uniform air gaps are not applicable to tunnel‐catenary.To investigate the impulse discharge characteristics of the tunnel‐catenary,a typical structural model was built in an artificial climate chamber.Different altitudes were simulated by adjusting the atmospheric pressure.The 50%breakdown voltages of the 300–700 mm tunnel‐catenary gap were tested at 243–4000 m.The test found that the altitude/atmospheric pressure and gap length have an evident effect on the 50%impulse breakdown voltage,and the influence of humidity is relatively small.The polarity effect was analysed by streamer theory.The{d,P,h}parameter method was employed to obtain the fitting formulas for the impulse breakdown voltage.A high‐altitude correction method for the tunnel‐catenary breakdown voltage based on 1 km altitude was proposed.Field natural tests were conducted to verify the accuracy of the proposed method.The results show that the breakdown voltage obtained by the correction method has an average error of 3.66%in the results of the field tests,indicating that the method has engineering application prospects.

关键词： breakdown altitude correction

Multi-objective Day-ahead Polarity Switching Optimization for Voltage Unbalance in Bipolar DC Distribution Networks

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Journal of Modern power Systems and Clean Energy 2023年第4期11卷 1212-1223页

作者： Zhongchi Huang Qianggang Wang Yuan Chi Jianquan Liao Yu Zhang Niancheng Zhou chongqing University ChongqingChina Sichuan University ChengduChina state grid chongqing Shibei electric power supply branch ChongqingChina

Bipolar direct current(DC)distribution networks can effectively improve the connection flexibility for renewable generations and loads.In practice,concerns regarding the potential voltage unbalance issue of the distribution networks and the frequency of switching still remain.This paper proposes a day-ahead polarity switching strategy to reduce voltage unbalance by optimally switching the polarity of renewable generations and loads while minimizing the switching times simultaneously in the range of a full day.First,a multi-objective optimization model is constructed to minimize the weighted sum of voltage unbalance factors and the sum of number of switching actions in the day based on the power flow model.Second,a two-step solution strategy is proposed to solve the optimization model.Finally,the proposed strategy is validated using 11-node and 34-node distribution networks as case studies,and a switching and stabilizing device is designed to enable unified switching of renewable generations and loads.Numerical results demonstrate that the proposed strategy can effectively reduce the switching times without affecting the improvement of voltage balance.

关键词： Bipolar direct current(DC)distribution network multi-objective optimization renewable generation voltage unbalance

grid Side Distributed Energy Storage Cloud Group End Region Hierarchical Time-Sharing Configuration Algorithm Based onMulti-Scale and Multi Feature Convolution Neural Network

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Energy Engineering 2023年第5期120卷 1253-1269页

作者： Wen Long Bin Zhu Huaizheng Li Yan Zhu Zhiqiang Chen Gang Cheng state grid chongqing Shiqu electric power supply branch Chongqing400000China

There is instability in the distributed energy storage cloud group end region on the power grid side.In order to avoid large-scale fluctuating charging and discharging in the power grid environment and make the capacitor components showa continuous and stable charging and discharging state,a hierarchical time-sharing configuration algorithm of distributed energy storage cloud group end region on the power grid side based on multi-scale and multi feature convolution neural network is proposed.Firstly,a voltage stability analysis model based onmulti-scale and multi feature convolution neural network is constructed,and the multi-scale and multi feature convolution neural network is optimized based on Self-OrganizingMaps(SOM)algorithm to analyze the voltage stability of the cloud group end region of distributed energy storage on the grid side under the framework of credibility.According to the optimal scheduling objectives and network size,the distributed robust optimal configuration control model is solved under the framework of coordinated optimal scheduling at multiple time scales;Finally,the time series characteristics of regional power grid load and distributed generation are analyzed.According to the regional hierarchical time-sharing configuration model of“cloud”,“group”and“end”layer,the grid side distributed energy storage cloud group end regional hierarchical time-sharing configuration algorithm is realized.The experimental results show that after applying this algorithm,the best grid side distributed energy storage configuration scheme can be determined,and the stability of grid side distributed energy storage cloud group end region layered timesharing configuration can be improved.

关键词： Multiscale and multi feature convolution neural network distributed energy storage at grid side cloud group end region layered time-sharing configuration algorithm

Situation Awareness and Sensitivity Analysis for Absorption of grid-connected Renewable Energy power Generation Integrating Robust Optimization and Radial Basis Function Neural Network

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Journal of Modern power Systems and Clean Energy 2023年第6期11卷 1795-1803页

作者： Ziqi Zhang Zhong Chen Qi Zhao Yi Wang Jiang Tian School of electrical Engineering Southeast UniversityNanjingChina Suzhou power supply branch of the state grid Jiangsu electric power company SuzhouChina NARI Group Corporation Ltd. (State Grid Electric Power Research Institute Ltd.)NanjingChina

The significance of situation awareness(SA) in power systems has increased to enhance the utilization of gridconnected renewable energy power generation(REPG). This paper proposes a real-time calculation architecture based on the integration of robust optimization(RO) and artificial intelligence. First, the time-series simulation of the REPG consumption capacity is carried out under the current grid operating conditions. RO is employed in this simulation, given the randomness of the REPG output and the grid load. Then, the radial basis function neural network(RBFNN) is trained with the results under different parameters using the artificial fish swarm algorithm(AFSA), enabling the neural network(NN) to be the replacement for the time-series simulation model. The trained NN can quickly perceive the REPG absorption situation within the predefined grid structure and period. Moreover, the Sobol' method is adopted to conduct the global sensitivity analysis for different parameters based on the input-output samples obtained by the trained NN. Finally, the simulation experiments based on the modified IEEE 14-bus system prove the real-time performance and accuracy of the proposed SA architecture.

关键词： Renewable energy radial basis function neural network robust optimization sensitivity analysis situation awareness