Table of Content

28 July 2024, Volume 57 Issue 7

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Special Contribution

Analysis and Prospect of Transformation and Upgrading Effects of Coal-fired Power Units in China

Zhiqiang LIU, Jianfeng LI, Li PAN, Zhixuan WANG

2024, 57(7):  1-11.  DOI: 10.11930/j.issn.1004-9649.202402031

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The upgrading and transformation of coal-fired power plants serve as a pivotal means to enhance the cleanliness, efficiency, and flexibility of coal-fired power units, as well as to adapt to the shift towards a dual emphasis on foundational security and system regulation in coal-fired power generation. By analyzing the current status and effectiveness of coal-fired power unit upgrades in China, this study explores the major issues encountered during the upgrading process and proposes measures to promote such upgrades. It also offers a prospective view on the development of coal-fired power plant transformation. The research reveals that the energy-saving and carbon-reduction modifications in coal-fired power plants can reduce the average coal consumption for power supply under rated conditions by approximately 5 g/(kW·h). The flexibility enhancements enable the minimum output load of modified units to decrease from roughly 42% of the rated load to approximately 29% of the rated load. Additionally, the heating modifications increase the heat supply of modified units by approximately 56%. However, the upgrading process faces challenges such as the coordination of load rate and coal consumption for power supply, investment and returns, technology selection, and reliability. To address these issues, this study puts forward recommendations from the perspectives of operation, technology, and policy, providing valuable references for the orderly promotion of coal-fired power plant upgrades.

Modeling and Decision-making for Uncertainty in the New Power System

A Novel Inertia Delay Optimization Control Strategy for New Power Systems Based on Crisscross Optimization

Xue WANG, Lin LIU, Wendi LIU, Yanpeng ZHAI, Ling YANG, Fangyuan XU, Yan GAO, Jixin ZHANG

2024, 57(7):  12-20.  DOI: 10.11930/j.issn.1004-9649.202312029

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The power system, traditionally dominated by synchronous generators, is evolving into a new power system where virtual synchronous generators (VSGs) take the lead. This transition results in significant changes in the system's dynamic characteristics. Currently, most literature focuses on analyzing the dynamic behaviors of standalone or multi-machine grid systems based on an assumption of infinite power supply, with limited research on the dynamic characteristics of new power systems dominated entirely by VSGs. Therefore, this study first builds a model of a three-machine, nine-node system where VSGs are the primary controllers and conducts transient simulations using differential equations. Subsequently, the crisscross optimization (CSO) algorithm is employed to optimize the inertia delay in the new power system. A comparison is made between the optimized control system and the non-optimized system. The results demonstrate that the optimized system exhibits reduced oscillation amplitude and shorter adjustment times after disturbances occur. Through simulations, the validity of the conclusions is verified.

Self-synchronization Voltage Source LVRT Control Method for New Energy Inverter under Weak Grid

Dan LIU, Kezheng JIANG, Yiqun KANG, Xiaotong JI, Yunyu XU, Fang LIU

2024, 57(7):  21-29.  DOI: 10.11930/j.issn.1004-9649.202303126

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The self-synchronization voltage source control technology of the grid-connected inverter is of great significance to the construction of new power system dominated by renewable energy. When the voltage of weak grid drops, the traditional self-synchronization control strategy will have a series of problems in the process of low voltage ride through (LVRT), such as the large transient current impact, the instability of weak grid voltage, and the imbalance of voltage-current control ability, which are caused by the large grid impedance and phase angle difference. For this reason, the relationship between the grid voltage vector and the grid impedance and the grid-connected current in the case of voltage sag under the weak grid, as well as the influencing factors are derived in this paper. Furthermore, a multi-state following self-synchronization voltage source LVRT control method based on stable and transient impedance reshaping is proposed to balance the control ability between voltage and current through steady-state impedance, and ensure the transient control and smooth transition of voltage and current in the whole process through transient impedance reshaping. At the same time, a transient control strategy based on multi-state following is proposed to further ensure the smooth switching and stable operation during the voltage drop and recovery process under weak grid, which can firstly deliver reactive power to support the grid voltage, and compensate the impact of transient overvoltage and overcurrent caused by phase angle and amplitude mutation to help the grid voltage transit smoothly. Finally, the correctness and effectiveness of the proposed control method are verified in MATLAB/Simulink.

Extreme Operation Mode Extraction Method Based on Convex Hull Algorithm

Yanping XU, Jie BAI, Haobo SHI, Xiaohui QIN, Yantao ZHANG

2024, 57(7):  30-39.  DOI: 10.11930/j.issn.1004-9649.202305121

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In the context of safety and stability calculation in power system planning and operation, the operation mode that is the most unfavorable to safety and stability is generally selected for verification. However, with the increase of new energy penetration, the power grid has become more complex and changeable, leading to a more subjective artificial selection scenario. To address this issue, this paper proposes an extreme scenario extraction method based on a rapid convex hull algorithm to meet the requirements of scenario selection for security verification. From the perspectives of power supply planning and generation-transmission coordination planning, the extreme operating modes affecting planning are analyzed, considering generation adequacy, thermal power ramping requirements, and network transmission security. Based on the convex hull algorithm, the coordination system is constructed from the above-mentioned three aspects to extract the extreme operation mode. The proposed method is applied to extract the extreme operation modes in the power grid of Northwest China. Compared with the extreme scenario extraction based on the K-means algorithm, the results demonstrate that the proposed method can provide effective data support for scenario selection and meet the requirements of power grid planning.

Distributionally Robust Optimal Configuration for Shared Energy Storage Based on Stackelberg Game Pricing Model

Caijuan QI, Baosheng CHEN, Dongni WEI, Zhao YANG

2024, 57(7):  40-53.  DOI: 10.11930/j.issn.1004-9649.202307016

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The goals of carbon peaking and carbon neutrality and the construction of new power system have promoted the continuous development of new energy resources, while bringing along higher demands for energy storage. When configuring energy storage for wind farms in the power system, the shared economic model is used to optimize the configuration of energy storage with consideration of the pricing mechanism, and the impact of wind generation uncertainty on the energy storage configuration scheme is discussed. Firstly, based on the Stackelberg game for determining the price, a shared energy storage optimal configuration model is proposed, in which the shared energy storage operator is the leader, wind farms are the followers, and the profit of each participant is maximized. Then, to address the fluctuations of wind power output, a moment information-based distributionally robust optimization method is introduced to construct chance constraints to describe uncertainties, where the moment information is used to complete the ambiguity set to reduce the conservatism. The wind farm model is reconstructed into a mixed integer second-order cone programming model through Chebyshev inequality for solution. Finally, case studies are conducted based on the actual wind farm data in Ningxia, and the results show that the proposed optimal configuration model can reduce redundant investment, promote energy storage to participate in configuration and address the actual wind power generation fluctuations.

Research on Economic Configuration of Energy Storage for Assisting New Energy in Primary Frequency Regulation

Luyang LI, Longxiang CHEN, Lei CHEN, Dawei SUN, Linlin WU, Yong MIN

2024, 57(7):  54-65.  DOI: 10.11930/j.issn.1004-9649.202307042

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When participating in primary frequency regulation of electrical power systems, it is necessary for new energy to address the issue of energy sources. Configuring energy storage is an effective way. In practical application, the configuration of energy storage needs to consider the factors of physical characteristics, unit cost, and other constraints to comprehensively compare the technical economy. However, the energy storage system configuration schemes proposed in existing literature mainly analyze operational scenarios and fail to consider various engineering constraints and actual cost data of energy storage. Based on the actual cost data, this article fully considers the physical characteristics and engineering design constraints of the energy storage system to study the economy of distributed access to units within the station for assisting primary frequency regulation of new energy. The article analyzes the technical characteristics and design constraints of three types of energy storage systems, namely lithium batteries, flywheels, and supercapacitors. On this basis, three types of configuration methods for energy storage for primary frequency regulation are proposed, and cost analysis and technical economy comparison are conducted based on the configuration schemes.

Multi-mode Control Method of Gravity Energy Storage DC Link Battery

Jiayan HAN, Yanling LÜ, Chong ZHOU

2024, 57(7):  66-73.  DOI: 10.11930/j.issn.1004-9649.202309026

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Gravity energy storage is one of the important energy storage modes. However, due to its unique transient dynamic characteristics, it is necessary to construct a reasonable system topology and control method. In this paper, a multi-mode control method for the DC link of gravity energy storage is proposed. From the transient energy control perspective, the power match between battery energy storage and gravity energy storage is realized through dynamic analysis of the gravity energy storage system and delineation of the constraint conditions. The experimental results show that the proposed control method can significantly reduce the voltage rise of DC link in the case of input power fluctuation, reasonably allocate the power inside the gravity energy storage system, and improve the overall storage performance of the gravity energy storage system.

Distributed Photovoltaic Power Interval Prediction Based on Spatio-Temporal Correlation Feature and B-LSTM Model

Haijun WANG, Rongrong JU, Yinghua DONG

2024, 57(7):  74-80.  DOI: 10.11930/j.issn.1004-9649.202310049

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A distributed photovoltaic (PV) power interval prediction method based on spatio-temporal correlation features and bayesian long short-term memory (B-LSTM) model is proposed. The approximate Bayesian neural network is constructed by adding a Dropout layer based on the LSTM neural network to establish a B-LSTM model considering spatio-temporal correlation features, and its powerful memory and feature extraction capabilities are used to extract deep features for distributed PV power interval prediction for intrinsic mode function components with different feature scales. An arithmetic example is analysed with an actual distributed PV dataset in a region to verify the superiority of the proposed method.

Key Technologies for Energy Storage Planning and Operation of New Power System

Allocation of Hybrid Energy Storage Capacity Based on Pearson Correlation Analysis and T-tFD Algorithm under VMD Decomposition

Shurui LIU, Peiqiang LI, Jiayu CHEN, Yashi GUO

2024, 57(7):  82-97.  DOI: 10.11930/j.issn.1004-9649.202403025

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In the context of rapid development of clean energy, the stochasticity and volatility of wind power output have significant impacts on the stability of power system, so wind power fluctuation smoothing is a basic problem for the current clean energy development. A hybrid energy storage capacity allocation strategy based on SCNGO-VMD is proposed to smooth wind power fluctuations. After variational mode decomposition (VMD) of the wind power parameter optimization, the Pearson correlation analysis is used to judge the boundary points of strong and weak correlation, and the grid-connected power and hybrid energy storage power are obtained after two allocations; The hybrid energy storage power is allocated based on T-test frequency division (T-tFD) algorithm, and the capacity configuration of battery/ultra-capacitor is obtained. Based on this strategy, the annual comprehensive cost of energy storage components is used as the model to evaluate the economics through case study. And the fluctuation of grid-connected power and the superiority of the SCNGO are analyzed. The results show that the energy storage capacity allocation strategy based on SCNGO-VMD can effectively smooth wind power fluctuations. The maximum fluctuation of the smoothed grid-connected power for 1 minute and 10 minutes is only 18.2% and 45.52% of the national requirements, and the corresponding energy storage configuration cost is the lowest among traditional configuration strategies. The configured hybrid energy storage capacity is more economical. Meanwhile, it is verified that the SCNGO is superior to the traditional intelligent optimization algorithm in iteration speed and accuracy.

Collaborative Expansion Planning of Source-Grid-Storage in Medium Voltage Distribution System Considering Operational Flexibility

Fengliang XU, Keqian WANG, Wenhao WANG, Peng WANG, Huanchang WANG, Shuai Zhang, Fengzhan ZHAO

2024, 57(7):  98-108.  DOI: 10.11930/j.issn.1004-9649.202312058

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To adapt to the dual volatility of distributed generation (DG) and load in the new distribution system, it is necessary to coordinate the source-grid-storage allocation to meet the needs of system operational flexibility. To characterize the operational flexibility level of the distribution system, three indexes including the net load adaptability index, net load fluctuation index and line load margin balance index are proposed from three aspects including flexible supply and demand balance, net load curve smoothness and line transmission balance, and a distribution system source-grid-storage three-layer expansion planning model is established with consideration of above indexes. The upper and middle layers are optimized in distribution lines, DG and energy storage to minimize the annual comprehensive costs, and the lower layer is optimized in operation to maximize the operational flexibility. The composite clustering algorithm is used to generate the typical planning scenarios of the distribution system, and the three-layer extended planning model is solved with the improved particle swarm algorithm and non-dominated genetic algorithm in the bi-level nested form. Finally, the effectiveness and superiority of the proposed planning model are verified based on the improved IEEE33 node system.

Dynamic Modeling and Control Strategy for Hybrid Energy Storage System Considering State of Charge and Storage State of Hydrogen

Chong SHAO, Rongyi HU, Jiao YU, Mingdian WANG

2024, 57(7):  109-124.  DOI: 10.11930/j.issn.1004-9649.202402052

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Energy storage is one of the important methods for mitigating the fluctuation of renewable energy. A refined simulation model is presented that can describe the material transport and energy conversion in a proton exchange membrane electrolyser (PEM). The model is constructed based on the component structure of the PEM, as well as the principles of electrochemistry and thermal equilibrium, taking into account the phenomenon of internal gas transport across the membrane. Based on this model, an electricity-hydrogen coupling system including electrochemical energy storage and hydrogen energy storage is established. A two-layer coordinated control strategy considering the charge state of electrochemical energy storage and the hydrogen state of hydrogen energy storage is proposed. The upper-layer power allocation considers the changes in electric and hydrogen load demands in the system, and uses the battery state of charge and hydrogen storage tank state of hydrogen as important constraints to determine the operating modes for each device in the system. The bottom layer control achieves power tracking adjustment by utilizing PQ control, VQ control, and other methods according to equipment operating characteristics. The effectiveness of this proposed model and control method is verified through simulations under several different operation scenarios. The research results can provide support for the optimization of control strategies for wind-photovoltaic-hydrogen storage systems.

Power System

Lightning Risk Assessment of Distribution Network Line Based on Information Fusion

Zixiang PEI, Kai SHU, Xuntian ZHOU, Tiancheng FAN, Yuhe LUO, Yuting LIU

2024, 57(7):  125-131.  DOI: 10.11930/j.issn.1004-9649.202306118

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Lightning seriously affects the safe operation of distribution network lines. A lightning risk assessment method based on information fusion is thus proposed by introducing sensitive factors and vulnerability indexes. Firstly, a lightning risk assessment index system is constructed from five aspects including ground resistance, population density, tower height, river network density and slope direction. Secondly, by introducing the analytic hierarchy process of information fusion, a correlation matrix of lightning damage is established based on grey, entropy weight and evidence theory to carry out comprehensive evaluation. Finally, a case study of a distribution network line was conducted. The results show that the evaluation results of the proposed method are basically consistent with the actual results for overall trend of lightning risk, which validates the rationality of the index system.

A Novel Fault Feeder Selection Method for Resonant Grounding Distribution Networks Based on Improved Hough Transform

Liang GUO, Xinyu QU, Xiaowei WANG, Yizhao WANG, Ying TIAN, Fan ZHANG

2024, 57(7):  132-142.  DOI: 10.11930/j.issn.1004-9649.202306087

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Aiming at the problem of inaccurate feeder selection in case of zero-crossing voltage and high impedance faults in distribution networks, a novel feeder selection method for single-phase grounding faults of resonant grounding systems is proposed. Firstly, the optimized variational mode decomposition (VMD) is used to process the zero-sequence power of each feeder, consequently selecting the mode IMF(k) with the highest correlation strength with the original zero-sequence power. And then the IMF(k) is convert into a two-dimensional image in JPG format, and the Hough transform detection technology is used to obtain the fitting line and angle of IMF(k) at the initial stage of the fault. The angle between the fitting straight lines of the modal quantities of each feeder is compared and processed, and the feeder corresponding to the minimum comprehensive correlation coefficient value is determined as the faulty feeder. The simulation results show that the proposed method is not affected by the factors such as ground resistance, fault phase angle, noise interference, and data loss, which verifies the effectiveness of the proposed method.

A Precise Identification Method for Fault Trains Based on Train Grounding Current

Shicheng GUO, Yongsheng LIU, Jing WU, Wei HOU, Xin JIANG, Xiangliang ZHANG, Kai CHEN, Xiangjian SHI

2024, 57(7):  143-150.  DOI: 10.11930/j.issn.1004-9649.202306063

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To solve the problem that faulty trains can't be accurately identified when the DC traction power supply system for the dedicated return rail has a short circuit fault between the positive pole and the train, a precise identification method is proposed for fault trains based on train grounding current. Firstly, an equivalent model is established for the bilateral power supply traction system. Secondly, the difference of train grounding current characteristics between the faulty trains and the normal trains are analyzed. Finally the precise identification method for fault trains based on the train grounding current is proposed. The proposed method uses the amplitude and direction of the train grounding current as the fault identification criteria. The train is judged as normal when the amplitude of the train grounding current is less than the setting value; the direction of the train grounding current is used as criterion when the amplitude is greater than or equal to the setting value, and the train with positive current direction is judged as faulty and the train with opposite current direction is judged as normal. This method is simple in principle and easy to implement. The adoption of bi-criterion can effectively avoid misjudgment and improve the reliability. The feasibility and effectiveness of the proposed method are verified by Matlab simulation and field test.

Research on Europe-North Africa Hydrogen Coordinated Development

Xu HU, Ruijian AN, Yuchen DU, Xiaohan SHI, Yue WANG

2024, 57(7):  151-162.  DOI: 10.11930/j.issn.1004-9649.202305024

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Hydrogen is a clean energy carrier that can play an important role in the global energy transition. In recent years, the world's major countries and regions have introduced a series of policies to support the development of hydrogen energy. Europe has also formulated relevant policies to guarantee regional energy security and promote the development of hydrogen, and cooperated with neighboring countries to develop the hydrogen industry. North Africa has significant potential for renewable energy, but the regional energy composition has been relatively homogeneous, with hydrocarbon accounting for more than 90% of regional energy consumption, which poses a serious obstacle to regional economic and environmental development. With the decline of global renewable energy generation costs and the acceleration of clean energy transition, North African countries have successively put forward national renewable energy development strategies and set long-term goals. With the help of mature policy, technical support, and broad market demand in Europe, the idea of developing green hydrogen industry will be an important opportunity for the North Africa region to break through the development bottleneck. According to the estimation, the cost from local renewable energy power to green hydrogen and then, export to the European market can be competitive with the local European green hydrogen. However, the transition is difficult due to the lack of policies and funding, as well as the high dependence on traditional fossil energy. North African countries need to strengthen policy guidance and promote international cooperation to promote hydrogen development and drive the energy transition of the region, and finally become the global center of hydrogen energy.

Calculation and Sharing of Regional Carbon Emission Reduction Considering Construction of Ultra High Voltage AC Projects

Shuo WANG, Huijuan HUO, Dan XU, Xin QIE, Cheng XIN, Weiwei LI, Jing DUAN

2024, 57(7):  163-172.  DOI: 10.11930/j.issn.1004-9649.202305128

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Under the "dual carbon" goal, the ultra-high voltage (UHV) AC project, with its advanced technological means, will play a greater role in consuming clean energy and reducing transmission losses. Considering that there is relatively little research on the carbon reduction benefits of UHV AC projects. this paper proposes a quantitative method for evaluating the carbon reduction benefits of UHV AC projects, taking the load landing area as the research object. Firstly, the distribution of power flow at both ends of the transmission and reception is simulated to determine the power flow proportion of the transmission channel. Secondly, an analysis is conducted on the electricity balance of the power supply area to determine the amount of clean energy transmitted by the UHV AC project. The carbon reduction emissions in the load area is calculated based on carbon emission factors, and the Shapley value is used to calculate the carbon reduction benefits of the UHV AC project based on its contribution. Finally, an actual project is taken as an example for numerical analysis. The results indicate that the UHV AC project can reduce carbon emissions by improving the ability to accommodate clean energy.

Topology Optimization of Offshore Wind Power Collection System Considering Actual Carrying Capacity of Submarine Cables

Jing YE, Junwen CAI, Lei ZHANG, Guanghao ZHOU, Jiehui HE, Xue ZHAI

2024, 57(7):  173-181.  DOI: 10.11930/j.issn.1004-9649.202307014

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The actual carrying capacity of submarine cables is important evidence for submarine cable selection, and in the topology optimization of offshore wind power collection systems, it is of great significance to consider the differences in carrying capacity of submarine cables in different laying sections and the effects of magnetic heat effect on the carrying capacity of the submarine cable laying in parallel with multiple circuits, which can ensure the safety of the power collection system. Firstly, the wind turbines were divided into clustered partitions using the fuzzy C-mean algorithm, and the power collection system topology was divided into intra-partition and extra-partition topology optimization. Then, a topological search algorithm based on Voronoi diagrams was used for the solution within the partition. Subsequently, in the extra-partition topology optimization, the impact of the submarine cable bottleneck section and the number of circuits on the carrying capacity was considered, and a mixed integer nonlinear optimization model was built. After linearization, the model was solved by the optimization solver GUROBI. Finally, an actual wind farm was used as a case for simulation verification. The results show that the proposed model can ensure the actual carrying capacity of the submarine cable is greater than the working current, and it effectively ensures the safety of the power collection system.

A Credible Monitoring Model for Carbon Emissions in Industrial Parks Based on Blockchain Technology

Dong WANG, Jingli FENG, Da LI, Jingwei NIU, Jun LI

2024, 57(7):  182-187.  DOI: 10.11930/j.issn.1004-9649.202309045

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A digital model for trusted monitoring of carbon emissions in the park based on energy and power blockchain is proposed to be built. The blockchain anti-tamper technology is first used to ensure the trusted storage requirements of monitoring data. All relevant access entity indicators are authenticated and controlled by the alliance chain, which avoids the risk of data loss and malicious tampering by others other than the subject; Secondly, in the fusion process of specific monitoring indicators, the model combined with AHP method to build a carbon emission evaluation index fusion strategy, and carried out multi-source online fusion of energy and power related index data combined with similarity clustering algorithm. Finally, LOF algorithm is used to detect long-period abnormal outliers of index data, which can solve the problem of data distortion or self-screening of misstatement to some extent.

Adaptive Understanding Framework and Key Technology of Power Grid Fault Disposal Information

Bo TIAN, Yue ZHANG, Fei MENG, Lianfei SHAN, Haiyang GAO, Kun TIAN, Yongtian QIAO

2024, 57(7):  188-195.  DOI: 10.11930/j.issn.1004-9649.202401026

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In order to improve the response capacity of power grid fault disposal, an adaptive understanding framework of fault disposal information is proposed. The framework is based on the constructed multi-task collaborative understanding model and the fault disposal knowledge graph to identify the power grid fault alarm, operation status, operation instruction and other information, and the fault disposal operation strategy is generated by reasoning adaptively. By establishing the evaluation index system and test data set of fault disposal information, the experimental effect of the adaptive understanding framework of fault disposal information and multi-task collaborative understanding model are verified.

Economic Capacity Assessment of Renewables in Distribution Networks

Pengfei FAN, Baoqin LI, Jiangwei HOU, Rong LI, Chongming SONG, Kaijun LIN

2024, 57(7):  196-202.  DOI: 10.11930/j.issn.1004-9649.202312019

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Based on the robust optimization method, considering the safe operation and economic objectives, the capacity of distributed power generation and energy storage in the distribution network is optimized. According to historical data and probability distributions of the uncertain wind, solar and load, multiple scenarios of these uncertainties are generated, and the uncertainty set describing these uncertainties is established using these operation scenarios. Then, based on the uncertainty set, a two-level robust optimization model is established. The outer-level model searches for the economically worst operation scenario in the uncertainty set. The inner-level model optimizes the capacity of wind, solar and energy storage in the worst scenario, taking into account the security constraints of distribution network. Compared with the capacity allocation results of the traditional method using typical operation scenarios, the capacities allocated in this paper are smaller, and can meet the condition of safe operation in the distribution network, with higher economic performance.

New Rapid Decoupling Methods for Calculating Steady-State and Interval Power Flow of Integrated Electricity-Heat Energy Systems

Weiwei JING, Qiang WANG, Hao CHENG, Bo WANG, Fuchang YUE, Chen WANG, Wenxue WANG

2024, 57(7):  203-213.  DOI: 10.11930/j.issn.1004-9649.202309019

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Steady-state power flow calculation of integrated energy systems is fundamental to subsequent planning and operational studies. The commonly used Newton-Raphson method poses challenges in numerical stability. Moreover, with the increasing uncertainty in integrated energy systems, it becomes increasingly vital to study the interval power flows for the safety analysis and evaluation of the integrated energy systems. Initially, based on the first and second order expansions of the Taylor function, the analytical expressions for heat load flow and nodal temperature are derived, which allow for the independent solution of flow rate and temperature, enabling the determination of system steady-state flow without solving equation set. And then, the monotonicity of the flow rate and temperature expressions is analyzed in conjunction with heat load values to determine the interval flow solutions for heat load flow and nodal temperature. The proposed method is fast in calculation speed and free from numerical stability problems while ensuring the computational accuracy. Finally, the effectiveness of the proposed method is validated through case study analysis.

Analytical Target Cascading Based Active Distribution Network Level Multi-agent Autonomous Collaborative Optimization

Jiawu WANG, Dianyun ZHAO, Changfeng LIU, Kang CHEN, Yumin ZHANG

2024, 57(7):  214-226.  DOI: 10.11930/j.issn.1004-9649.202311008

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As part of the strategic push toward achieving carbon neutrality, the imperative to integrate renewable energy into active distribution networks (ADNs) on a large scale has become a priority. However, the traditional centralized control methods are hamstrung by dispatch control strategies and data interchange modes, falling short in accommodating the needs for distributed energy assimilation and meeting the economic operation goals of distribution networks. In response, this work introduces an innovative regional multi-agent autonomous collaborative optimization approach for ADNs, grounded in Analytical Target Cascading (ATC). This approach treats flexible loads, distributed energy resources, and storage systems as controllable unit agents. It aligns with the overall economic optimization objectives of the distribution network and the localized autonomous optimization requirements of microgrid domains, framing a dispatch architecture structured around "ADN entity-node entity-controlled unit entity." Leveraging ATC to handle the inter-agent shared interactive information, the approach effectively separates complex system hierarchies into primary systems and subsystems. This separation facilitates a synergistic optimization that respects both the comprehensive and specific regional goals. The method's robustness and efficiency are substantiated through the development and testing within D9M2 and IEEE 33 node distribution systems, demonstrating its validity in practical scenarios.

Generation Technology

Life-Cycle Carbon Footprint Assessment of Coal-fired Power Generation

Hanxiao LIU, Sike SHAN, Shuzhou WEI, Liyuan YU, Shuai WANG, Meiling LIU, Ying CUI

2024, 57(7):  227-237.  DOI: 10.11930/j.issn.1004-9649.202404039

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Carbon footprint, as an essential tool for quantifying carbon emissions, provides data support for carbon emission reduction in coal-fired power generation. To investigate the electricity carbon footprint of coal-fired units and its influencing factors, actual case calculations and sensitivity analysis were conducted based on the life cycle method. The carbon footprint calculation results indicate that the carbon footprint per unit of grid-connected electricity for a 300 MW coal-fired power generation unit is 0.932 kgCO₂e/kW·h. The primary emission source is coal combustion, accounting for approximately 79%, followed by upstream coal production and processing, accounting for approximately 20%. The comparative analysis of carbon footprint and carbon verification concludes that reducing carbon emissions should not only focus on conventional methods in coal-fired power plants, but also consider reducing emissions in the upstream coal supply stage as an effective solution.

Broadband Impedance Modeling and Sub/Super-synchronous Oscillation Analysis of Steam Turbine Generator

Muchi ZHAO, Haijiao WANG, Chun LIU, Guoqing HE, Yanxia SUN, Panpan WANG

2024, 57(7):  238-246.  DOI: 10.11930/j.issn.1004-9649.202312081

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Impedance-based modeling and analysis method is currently one of the effective tools to analyze and solve the problem of renewable energy grid-connected broadband oscillation. Centralized development of long-distance transmission is an important form of renewable energy development and utilization in China. Among the power generation equipment in the renewable energy base, the impedance model of wind and solar power generation equipment has been built perfectly, but the current broadband impedance model of the steam turbine generator has some simplification, failing to completely reflect the broadband impedance characteristics of the steam turbine generator. Based on the frequency-domain small-signal modeling method, a broadband impedance model of the steam turbine generator containing the prime mover, speed governor, exciter system, shaft system, and synchronous generator was established. A simulation model of a steam turbine generator was built in Matlab/Simulink, and the correctness of the proposed model was verified by frequency sweeping. The influence of different links on the impedance was analyzed. Finally, the effectiveness of the proposed model in the analysis of the sub/super-synchronous oscillation problem was verified by studying a steam turbine generator connected to the grid via a series compensation device.