30 October 2024, Volume 44 Issue 5

  

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  Progress in the Research of Thermionic and Thermophotovoltaic Converters and the Hybrid Systems in the Near-Field

  LI Lin, WU Xiaohu, YU Kun

  2024, 44(5): 1-14. https://doi.org/10.19718/j.issn.1005-2992.2024-05-0001-14

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  Thermoionic converters and thermophotovoltaic converters are two primary solid-state thermoelectric converters capable of operating at extreme temperatures with the potential for high efficiency,making them suitable for ultra-high temperature thermal energy storage applications.Both rely on the transfer of fundamental energy carriers through highly non-isothermal junctions:electrons in thermoionic converters and photons in thermophotovoltaic converters.However,the performance of both converters is constrained by factors such as the Stefan-Boltzmann law and space charge effects,preventing further enhancement.Nevertheless,when the distance between the emitter and absorber is comparable to or less than the thermal radiation characteristic wavelength,the performance of both converters can be significantly enhanced due to the photon tunneling effect generated by evanescent waves and the mitigation of space charge effects.Therefore,it holds significant importance in fields such as waste heat recovery and renewable energy utilization.This paper reviews the research progress of domestic and foreign scholars in the two types of solid-state thermoelectric converters and their hybrid systems,summarizes and analyzes potential future directions and key challenges.
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  Review on CCUS Investment Benefits : Insights into Technology, Economics, and Policy

  ZHOU Xiaolin, LIU Yawen, HAN Jieping

  2024, 44(5): 15-23. https://doi.org/10.19718/j.issn.1005-2992.2024-05-0015-09

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  Carbon Capture, Utilization, and Storage （CCUS）technology is of great significance in global climate change mitigation and achieving carbon neutrality. However, its large-scale commercial implementation is restricted by low investment returns. This paper systematically reviews the progress of research on CCUS investment benefits from both domestic and international perspectives, analyzing the impacts of technological innovation, economic costs, and policy support on investment returns. It also assesses regional differences worldwide in terms of policies, technologies, and economic benefits. The study reveals that while CCUS technology shows great promise, its economic feasibility and insufficient policy incentives are still key barriers to its deployment. By summarizing the shortcomings and challenges in current research, this paper provides directions for future studies and theoretical and practical references for CCUS commercialization and policy-making.
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  Ultra-short Term Wind Power Prediction Based on Evolutionary Bagging Ensemble Learning

  KANG Yingzhe, TIAN Yuhang, LIANG Shichang, TANG Zhenhao

  2024, 44(5): 24-32. https://doi.org/10.19718/j.issn.1005-2992.2024-05-0024-10

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  In order to achieve high-precision ultra-short-term prediction of wind power,this study conducted cross-domain feature selection based on Wasserstein distance and Random Forest （RF），and combined it with Evolutionary Bagging （EvoBagging）。A new method for ultra-short term wind power prediction is proposed.Firstly,the Local Outlier Factor （LOF）algorithm is used for outlier detection,and K-Nearest Neighbors InterpolationK-NNI is used to replace outlier points in the original data.Secondly,the data after outliers were decomposed by Empirical Mode Decomposition （EMD）algorithm and statistically calculated to build the reconstructed data,and Wasserstein distance and RF cross-domain feature selection were used to reduce the feature dimension of the reconstructed data.Finally,in order to combine the advantages of each model to improve the prediction accuracy of the model,It is constructed with Deep Belief Network （DBN），Deep Neural Networks（DNN），Light Gradient Boosting Machine （LGBM）and eXtreme Gradient EvoBagging ensemble learning ultra-short term wind power prediction model based on Boosting（XGBoost）learner.It is proved that the prediction error of this model is reduced by 5%on average compared with that of a single model,and it can achieve high precision prediction of ultra-short term wind power.
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  Study on Heat Storage/Release Performance of a New Zonal Seasonal Thermal Storage Tank

  ZHAO Hongpeng, LIU Yongxu, JIANG Tieliu, YANG Guang, LI Pan, HU Pengfei, LI Qi, LIU Zhongyan

  2024, 44(5): 33-41. https://doi.org/10.19718/j.issn.1005-2992.2024-05-0033-09

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  Large-scale cross-season heat storage technology can effectively solve the problem of winter and summer heat imbalance of new energy heating.In this paper,a new type of zonal seasonal heat storage tank is proposed,and the heat dissipation effect and annual thermal efficiency of the heat storage tank under two different storage/release modes are calculated and compared by numerical simulation.The results show that the heat storage tank can maintain high annual thermal efficiency under both storage and release modes.Mode 2 adopts the strategy of "the last one goes first"， although the thermal efficiency of each zone is abandoned,it ensures that at least half of the zones are working under a higher heat utilization rate,and the annual thermal efficiency of the whole heat storage tank can reach 88.25%.Under mode 1，the annual thermal efficiency of the heat storage tank is 87.55%，which is slightly worse than that of mode 2， but it can ensure the stability of the hot water temperature throughout the heating season.
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  Research on Low-voltage Control Method Based on Series Voltage Compensation Control

  WANG Shiqing, CHEN Gang, LIU Yitao

  2024, 44(5): 42-49. https://doi.org/10.19718/i.issn.1005-2992.2024-05-0042-08

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  In order to solve the problem of poor economy of series voltage compensation device designed for low voltage at the end of rural power grid, a low voltage control method based on series voltage compensation control is designed. Considering the influence of static characteristics of load voltage, the two indicators of line active power loss and average voltage deviation of each node are normalized and weighted as the objective function, and the method for selecting the location and capacity of compensation devices is proposed. The low voltage line at the end of an actual power grid is selected for simulation test, and the test results show that the method can effectively solve the low voltage problem at the end of rural power grid.
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  Distributed Photovoltaic and Energy Storage Capacity Allocation Method for the Optimal Use of Energy in the Park

  LIN Peixin

  2024, 44(5): 50-56. https://doi.org/10.19718/j.issn.1005-2992.2024-05-0050-07

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  Under the background of "dual carbon"，the energy consumption in parks tends to be clean and low-carbon. The scaled development of distributed photovoltaic and energy storage can optimize the energy consumption structure and cost in parks. How to optimize resource allocation and achieve green energy consumption in parks is a current research hotspot.This paper will focus on the demand for optimizing the capacity configuration of distributed photovoltaic and energy storage in parks,and study the optimal configuration method of distributed photovoltaic and energy storage from the perspective of energy consumption cost.The goal is to minimize the annual energy consumption cost and the grid variability coefficient,and an improved adaptive weight particle swarm optimization algorithm is used to establish a two-level optimization model to propose a method for optimally configuring distributed photovoltaic and energy storage capacity for park energy consumption. An example application is carried out in a park energy consumption scenario to verify the feasibility and effectiveness of the model selection and optimization algorithm.
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  Distribution Network Power Quality Management Model Based on Grid-Vonnected Inverter Control

  YANG Jingxuan, ZHANG Chi

  2024, 44(5): 57-62. https://doi.org/10.19718/j.issn.1005-2992.2024-05-0057-06

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  As distributed power sources access the distribution network in a wide range of multiple points,the power quality problems of the distribution network are highlighted.Distributed power sources are connected to the distribution network through grid-connected inverters,and the optimal control of grid-connected inverters can enhance the source-side improvement effect of power quality and fully exploit the regulation potential of the remaining capacity of the inverters.Therefore,this paper proposes a multi-objective optimisation model of distribution network power quality based on the control of grid-connected inverters of distributed power sources.Firstly,the quantitative model of the adjustable capacity of distributed power inverters is analysed to ensure the quality of power generation；then,according to the results of the power quality assessment of distribution network zones,the optimization model of grid-connected inverter control parameters is established,and the multi-objective optimization method of power quality based on inverter control is proposed；finally,the effectiveness of the proposed method is verified through simulation examples.Finally,the effectiveness of the proposed method is verified by simulation examples.The results show that,with the method proposed in this paper,the harmonics and unbalance of the distribution network are obviously suppressed, and the compensation effect is obvious,which is an effective means for the future optimisation of the power quality of a new type of distribution network.
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  Analysis and Evaluation of Frequency Stability Characteristics of New Energy Power System Based on Key Response Characteristics 

  ZHANG Zedong, LIU Cheng, JIANG Minglei, ZHOU Shuyu, ZHANG Yuchi

  2024, 44(5): 63-72. https://doi.org/10.19718/i.issn.1005-2992.2024-05-0063-10

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  The high proportion of new energy grid connection leads to the reduction of power system inertia and the more complex spatial and temporal distribution characteristics of power grid frequency.It is urgent to clarify the frequency stability discrimination of power grid in new scenarios. In order to examine the frequency characteristics and frequency stability discrimination in the new scene, firstly, through the analysis of the new scene characteristics, the variables that can reflect the frequency time series characteristics are selected. After Pearson correlation analysis and feature hierarchical clustering dimension reduction, the feature quantities that are strongly correlated with the frequency and easy to measure are selected as the key response feature quantities. Through the correlation curve of its response characteristics with the frequency, the frequency is studied with the change of its feature quantities in the system stability and instability state, and the frequency criterion is constructed. The criterion can identify the fault unit while judging the stability. Finally, the effectiveness of the method is verified by an actual power grid example.
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  Data-driven Online Voltage Stability Evaluation for Renewable Energy Power Systems

  QIAO Xinyue, WANG Lixin

  2024, 44(5): 73-79. https://doi.org/10.19718/i.issn.1005-2992.2024-05-0073-07

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  With the rapid development of new energy,the difficulty of solving voltage stability problems in new power systems has increased,and traditional evaluation methods are no longer able to meet real-time and accurate requirements.Based on the Q-V curve theory,a sensitivity index for voltage stability evaluation of a new type of power system connected to the wind turbine grid has been established in the article.Firstly,the power system flow equation is used to calculate and analyze the changes in reactive power and voltage amplitude of the load,and sensitivity indicators are classified according to the results.Then,a weighted average algorithm is introduced to fit the sensitivity data over a period of time,and the fitted values are used to represent the sensitivity of the load during that period.Finally,the DIGDILENT simulation platform was used to conduct simulation verification on the IEEE 10 machine 39 node system.By comparing the sensitivity index and reactive power margin under different operating conditions,the effectiveness of this index in evaluating the voltage stability of the new power system was verified.
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  Low Carbon Optimization Strategy for Transmission Lines Based on CCER Carbon Emission Accounting

  XU Chenghao, ZHU Wenwei, PAN Baichong, CHE Weixian, LONG Yanliang, WANG Dianbin, GUAN Wenxu

  2024, 44(5): 80-86. https://doi.org/10.19718/i.issn.1005-2992.2024-05-0080-07

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  The research aims to explore the new construction and renovation strategies for energy-saving transmission conductors.By comparing and analyzing the application of five types of conductors in practical engineering,including aluminum-clad steel-cored （high-conductivity）aluminum stranded wire,aluminum alloy-cored （high-conductivity）aluminum stranded wire,medium-strength aluminum alloy stranded wire,steel-cored high-conductivity aluminum stranded wire,and aluminum alloy-cored aluminum stranded wire,combined with the principle of energy-saving conductors,the investment and operating costs of transmission conductors under different voltage levels （+800kV DC，500kV AC，220kV AC，110kV AC）and their energy-saving effects are evaluated.The research results show that the aluminum alloy core -type aluminum stranded wire has the best economic performance,and can cover the reconstruction cost and new construction cost through energy-saving benefits in a relatively short period of time.Further analysis shows that line length,annual utilization hours,and carbon price are key factors affecting the cost-benefit balance point.Therefore,using aluminum alloy core-type aluminum stranded wire for energy-saving transmission transformation can not only effectively reduce power loss and carbon emissions,but also bring significant economic benefits and promote the sustainable development of the transmission system.
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  Research on Electric Vehicle Charging Safety Early Warning Based on Outlier Detection Method

  GU Bing, LI Zehao, WANG Xiaolin, ZHAO Zitong, JIN Shengquan

  2024, 44(5): 87-93. https://doi.org/10.19718/j.issn.1005-2992.2024-05-0087-07

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  In the process of achieving the goal of carbon peak and carbon neutrality, in order to achieve environmentally friendly and energy-saving development,electric vehicles have begun to take the stage.With the rapid growth of electric vehicle ownership in the market,the safety problems caused by electric vehicles have gradually begun to emerge.Spontaneous combustion and fire accidents of electric vehicles are common.They have caused serious economic losses and even life hazards to automobile manufacturers,consumers,and operators of charging equipment.The charging safety of electric vehicles has begun to restrict the development of the electric vehicle industry.In this paper, starting from the constant voltage and constant current charging method, through the analysis of the causes of electric vehicle charging faults, a data mining early warning method based on discrete point detection of Gaussian distribution is proposed.The characteristic of outlier detection method is that it can effectively distinguish the data with significant difference from a set of data sets.A large amount of data will be generated during the charging process of electric vehicles. The Gaussian distribution model of normal charging state is obtained by obtaining the data under normal charging.The outlier detection method is used to judge whether the charging of electric vehicles is in a dangerous state, and the charging fault is warned in time. The real-time monitoring and early warning of electric vehicle charging process are realized. The experiment proves that the outlier detection method has good feasibility and accuracy for electric vehicle charging safety early warning .
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  Low-voltage DC Cable Fault Location Method Based on Improved Empirical Wavelet Transform

  DONG Moting, LIU Hongpeng, ZHANG Shuxin

  2024, 44(5): 94-100. https://doi.org/10.19718/j.issn.1005-2992.2024-05-0094-07

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  To improve the accuracy of low-voltage DC cable location,an improved empirical wavelet transform（IEWT）method and an improved double-end traveling wave criterion method are proposed.This method first uses the double-end traveling wave method to obtain the current signals at both ends of the faulty cable,and then decomposes and reconstructs the current signal through IEWT to obtain processed intrinsic mode function （IMF）components, which are screened to effectively avoid mode mixing in the decomposition of complex noise signals.Finally,the selected IMF components are detected using kurtosis rules,and the position of the fault point is determined by using the improved double-end traveling wave fault criterion.Simulation results show that this method has high accuracy and meets the requirements of engineering practice for location.
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  Optimization and Scheduling Strategy For Virtual Power Plant Clusters Considering Flexibility and Resource Complementarity

  WANG Qi, DONG Hongda, HE Zigian, NIE Fanjie, LIU Xiaojun

  2024, 44(5): 101-111. https://doi.org/10.19718/j.issn.1005-2992.2024-05-0101-11

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  Aiming at the lack of system operation flexibility caused by the low utilization rate of flexibility resources during the operation of virtual power plant cluster （VPPC），this paper proposes an optimal scheduling strategy for VPPC that takes into account the mutual benefit of flexibility resources.Firstly,based on the trading relationship between VPPC and the electricity spot trading market,a VPPC trading model is constructed in which VPPC counts and flexibility resources are mutually beneficial.Under this trading model,the supply-demand relationship between VPPC operating flexibility under the source-load uncertainty scenario is further analyzed with respect to the flexibility shortage phenomenon,and the VPPC flexibility mutual aid service fee settlement model is established.Secondly,the impact of participation in flexibility mutual aid service on the energy interaction between the lower virtual power plants and the economic operation of the upper cluster is studied in depth,and a two-layer optimization model of master-slave game is constructed to take into account the interests of multiple subjects,and a master-slave game equilibrium algorithm based on the Kriging meta-model is used to simulate the operation of each virtual power plant and reasonably formulate the price of mutual aid for the energy of virtual power plant clusters；lastly,the proposed solution can not only enable the cluster operator to earn a profit but also provide the cluster operator with a reasonable price for the energy of the cluster.Finally,it is verified through case studies that the proposed scheme not only enables the cluster operator to earn profits from the mutual aid service,but also reduces the power supply pressure on the power grid,lowers the operating costs of each virtual power plant,significantly improves the overall operational flexibility of the system and reduces the operating costs of all parties involved in the service.
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  Research on the Optimal Configuration of Distributed Phaser to Support Voltage Stability in New Energy Power Systems

  WANG Kaiping, JIANG Minglei, SUN Shengxuan, ZHU Meng, SHE Xin, ZHENG Huicong, FENG Fan

  2024, 44(5): 112-120. https://doi.org/10.19718/i.issn.1005-2992.2024-05-0112-09

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  A high proportion of new energy power sources connected to the grid will lead to power system voltage with volatility and randomness,thus reducing system voltage stability.As a key reactive power compensation device in new energy stations,distributed synchronous regulators play a significant role in enhancing system voltage stability.However,in the current new energy power system,how to configure these distributed regulators in an economically reasonable and reliable way needs to be explored in depth.To this end,a new distributed regulator siting and capacity-setting method focusing on voltage stability constraints is proposed in the paper.First,the static voltage stability index of the system is evaluated to guide the selection of the optimal installation location of the regulator to ensure that the selected location can most effectively improve the system voltage support capability.Subsequently,on the basis of site selection,the capacity configuration of the regulator is reasonably planned with the objectives of minimizing the investment cost and maximizing the operational reliability of the system.Finally,through the analysis of actual cases, this method is not only economical and efficient,but also provides a strong guarantee for the stable operation of the new energy power system.