Table of Content

28 July 2023, Volume 56 Issue 7

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Special Contribution

Review of Commercial Air Conditioners for Participating in Urban Grid Regulation

WU Tong, HUI Hongxun, ZHANG Hongcai

2023, 56(7):  1-11.  DOI: 10.11930/j.issn.1004-9649.202209064

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The key to achieving the goals of “carbon peak and carbon neutrality” lies in the economic and efficient operation of urban power grids. However, factors such as the increase of volatile new energy and the widening of load peak-valley differences bring challenges to urban power grids. Traditional power generation units maintain the stable operation of the power system by frequently adjusting their output, which is not only inefficient but also faces a shortage of adjustable resources. As an important part of the total electricity consumption of the urban grids, the air conditioning system of commercial buildings has the potential to act as an adjustable resource involved in grid regulation. Simultaneously, with the thermal storage characteristics of buildings, it can carry out regulation while meeting the comfort needs of indoor temperature for users, demonstrating its immense potential. In order to better tap into the regulatory capacity of the air conditioning system in commercial buildings, the case of both the single and aggregated models of typical commercial building air conditioning systems is shown, and the methods for assessing the potential of these systems for regulation and their control technologies are outlined. A comparative analysis of typical commercial building air conditioning system demonstration projects both at home and abroad is made, and some suggestions and prospects based on the current development situation are also provided.

Key Technology of Hydrogen Energy and Its System Integration Control for the New Power System

Capacity Planning of Hydrogen Production and Storage System Based on Hydrogen Load Demand

PENG Shengjiang, YANG Dezhou, SUN Chuanshuai, YUAN Tiejiang, LIU Yongcheng

2023, 56(7):  13-20,32.  DOI: 10.11930/j.issn.1004-9649.202301030

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In the future energy society, the value of hydrogen energy will be realized in the conversion of various types of energy sources, particularly as the key link in the power system. To this end, a new energy system capacity planning method based on different hydrogen load levels is proposed to promote the application and development of renewable energy sources more efficiently such as wind and photovoltaic energy in the power grid. The method can maximize the economical benefits of the system while meeting the regional hydrogen energy demand. Under different hydrogen production modes, the optimal hydrogen production system scale can also be determined. In addition, the penalty costs of curtailing wind and solar power and hydrogen energy supply shortage are taken into consideration as well as the environmental benefits of the system. The results show that it is more reasonable and economical to adopt the mode of grid-integrated wind power and photovoltaic energy transactions for electricity in hydrogen production, which avoids the redundant configuration of large-capacity hydrogen production-storage equipment.

Optimized Configuration of Hydrogen-Energy Microgrid Capacity Considering Source Charge Uncertainties

YUAN Tiejiang, YANG Yang, LI Rui, JIANG Dongfang

2023, 56(7):  21-32.  DOI: 10.11930/j.issn.1004-9649.202211054

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With regards to the low energy conversion efficiency and uncontrollable factors on the robustness of electrothermal gas-coupled microgrid planning due to the randomness of new energy resources, an optimization method for the configuration of hydrogen-energy microgrid is proposed considering the uncertainties of source charges. First of all, by taking advantages of hydrogen energy storage, electric boilers and organic Rankine cycle (ORC) systems to expand the electrothermal gas conversion paths of traditional microgrids, a multi-energy coupled, low-carbon and efficient hydrogen energy microgrid is set up. Then, a typical daily selection method of electrical load-wind power output based on ordered clustering algorithm and fuzzy c-means (FCM) clustering algorithm is proposed, with the minimization of annualized total cost as the optimization objective, and by taking into account the constraints of power balance, equipment operation, hydrogen storage system and natural gas pipeline, the hydrogen energy microgrid capacity optimization configuration model is established. Finally, the actual data of an industrial park is analyzed to obtain the optimal configuration scheme and the cost of each equipment in the system. Using Matlab and Yalmip toolbox for sensitivity analysis, it is verified that the proposed method and model can effectively reduce the total cost and carbon emissions.

Optimal Configuration of Electricity-Hydrogen Hybrid Energy Storage System Based on Multi-objective Artificial Hummingbird Algorithm

LU Zijing, LI Zishou, GUO Xiangguo, YANG Bo

2023, 56(7):  33-42.  DOI: 10.11930/j.issn.1004-9649.202301006

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Through the combination of hydrogen energy storage system and battery energy storage system, the long-term and fast energy conversion can be achieved and the impact of increasing penetration of distributed generation on the stability of distribution network can also be reduced. Considering the economic and technical requirements of hybrid electric-hydrogen energy storage system connected to distribution network, a multi-objective optimal configuration model of hybrid electric-hydrogen energy storage system is established to minimize the life cycle cost, voltage fluctuation and net load fluctuation of distribution network. The multi-objective artificial hummingbird algorithm based on Pareto is used to solve the planning scheme and then compared with the multi-objective particle swarm optimization and multi-objective atomic orbital search algorithm. Finally, the model based on the extended IEEE-69 bus standard test system is solved. The simulation results show that with the proposed multi-objective artificial hummingbird algorithm Pareto frontier can be obtained with better solution set quality. The resulting hybrid energy storage system configuration scheme can improve the voltage quality and load level of distribution network while taking into account the economic benefits. Compared with the energy storage system of exclusive battery configuration, the application of electric-hydrogen hybrid energy storage system can improve the distribution network net load fluctuation and voltage fluctuation by 21.02% and 16.66% respectively, which has verified the effectiveness and outstanding performance of the optimal configuration method proposed in this paper.

Research on Coordinated Control Strategy of Hydrogen-Electric Hybrid Energy Storage Microgrid Based on Exponential-Function-Based Droop Control

WANG Jihua, YE Xiaming, QIN Ruyi, YING Fangyi, YU Jiajie

2023, 56(7):  43-53.  DOI: 10.11930/j.issn.1004-9649.202209002

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With the rapid development of multi-energy hybrid energy storage technology, hydrogen-electric hybrid energy storage system will become increasingly important to solve the intermittency and volatility problems of grid-connected renewable energy generation. In this paper, the theoretical open-circuit voltage of PEM electrolysis hydrogen production is derived by applying the principle of thermodynamics, and the expected actual voltage is obtained through the integration of different overpotentials as the function of current. An electrochemical model conforming to the output characteristics of hydrogen production voltage is established. Then, based on the analysis of the typical architecture of hydrogen-electric hybrid energy storage microgrid, the exponential-function-based sagging control strategy considering battery SOC is proposed, such that the SOC balance problem during battery parallel charging and discharging can be resolved while maintaining the bus voltage stability of microgrid. Finally, in combination with the adaptive control methods of photovoltaic and electrolytic hydrogen production units, the operation of microgrid is distinguished into four working modes according to the charging and discharging state of the battery, and the related simulation analysis is carried out. The results show that the exponential-function-based sagging control strategy considering the battery SOC can make the microgrid achieve smooth transition between working modes. Particularly adaptive power distribution can be implemented when the photovoltaic power supply fluctuates. Therefore both the system economy and energy utilization efficiency are effectively improved.

Optimal Capacity Configuration of Residential Solar-Hydrogen Coupling Energy System with Hydrogen Vehicle Load

DOU Zhenlan, ZHANG Chunyan, ZHAO Huirong, YAO Yuqi, PENG Daogang

2023, 56(7):  54-65.  DOI: 10.11930/j.issn.1004-9649.202208077

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To address the impact of household hydrogen vehicles on residential energy system, an integrated residential energy system is designed with multiple types of energy storage devices including electric, thermal and hydrogen storage components coupled with photovoltaic/photothermal equipment. The mathematical model based on mixed integer linear programming theory is then proposed for system capacity configuration optimization. Firstly, with the high-efficiency photovoltaic and solar-thermal devices as the major energy production contributor, and the hydrogen energy as the major energy conversion and storage medium, the energy supply system architecture is designed to meet the residential electric, heat and hydrogen vehicle’s load requirements. Secondly, by setting the capacity of the equipment in the system as the optimization variable, and the minimization of annual investment cost of the system as the objective function, the reliability of energy supply and other factors as the constraints, the system optimal capacity configuration model is established. Finally, the system performance is evaluated in terms of the annual total investment saving rate and renewable energy utilization rate, which decreases by 42.21% and increases by 33.32% respectively after optimization. Meanwhile two different mobile load scenarios are constructed with exclusive electric vehicles and hydrogen energy vehicles respectively. Then the sensitivity analysis regarding the price of hydrogen energy equipment is carried out. It turns out that the residential energy supply system with hydrogen energy vehicle load will demonstrate more economic advantages if the hydrogen equipment price is reduced by more than 60%.

Flexible Load Stochastic Optimal Control of Wind Power-Based Hydrogen Production and Ammonia Synthesis Systems Based on the Itô Process

YANG Guoshan, ZHU Jie, SONG Wenqin, QIU Yiwei, ZHOU Buxiang

2023, 56(7):  66-77.  DOI: 10.11930/j.issn.1004-9649.202209056

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Wind power-based hydrogen production and ammonia synthesis (P2A) is one of the potential technical routes for large-scale renewable energy consumption and carbon emission reduction in the power and chemical industries. Taking power-to-hydrogen production as a medium, P2A can participate in grid balancing regulation as a large-scale industrial load. However, due to the limitation of the chemical process and control of the ammonia synthesis load, the inertia of load regulation is large. When the wind power output deviates from the predicted trajectory, it is difficult for the P2A load to respond quickly. Thus, a stochastic optimal control method for the P2A load considering temporally correlated uncertainty of wind power is proposed. Firstly, the flexible regulation state-space model of the P2A system is established. Second, considering the coupling of the stochastic process of wind power output and the adjustment inertia of the ammonia synthesis section, the Itô process is used to model the stochastic process of wind power output, and a stochastic dynamics-constrained optimal control model of the P2A system is constructed. Then, the stochastic optimization problem is transformed into a deterministic second-order cone programming by the trajectory sensitivity decomposition and solved by the stochastic model predictive control (SMPC) in a rolling-horizon manner, avoiding the disadvantages of high computational complexity and low efficiency of the traditional sampling-based stochastic control methods. The case study shows that, compared with deterministic control, the proposed method fully takes advantage of the flexible production of ammonia synthesis and greatly improves the ability of P2A Load to consume the fluctuating wind power.

Power System

Construction and Application of Knowledge Graph for Intelligent Retrieval of Power Grid Dispatching and Control Information

LIU Dong, ZHANG Yue, PI Junbo, SHAN Lianfei, LIU He, SONG Pengcheng, JIANG TAO

2023, 56(7):  78-84.  DOI: 10.11930/j.issn.1004-9649.202209084

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Lack of effective retrieval means for the multi-dimensional information of power grid dispatching and control, a knowledge graph construction method for the intelligent retrieval of power grid dispatching and control information is proposed. The semantic relationship of dispatching operation procedures key information is recognized based on deep learning, and the rule conversion method is used to extract the power grid model information. The dispatching and control information knowledge map is established by integrating the targeted knowledge of dispatching operation procedures and power grid model knowledge, and the application scheme of intelligent retrieval of dispatching and control information based on knowledge graph is proposed. The proposed method has been verified to have high recognition accuracy through numerical examples, and can support intelligent retrieval of regulatory information in different scenarios.

Strategy for DC Microgrid Energy Management Based on RG-DDPG

LI Jianbiao, CHEN Jianfu, GAO Ying, PEI Xingyu, WU Hongyuan, LU Zikai, ZHOU Shaoxiong, ZENG Jie

2023, 56(7):  85-94.  DOI: 10.11930/j.issn.1004-9649.202210086

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The randomness and intermittency of distributed energy have brought great challenges to the energy management of direct current (DC) microgrids. In order to solve this challenge, a DC microgrid energy management strategy based on reward guidance deep deterministic policy gradient (RG-DDPG) is proposed in this paper. This strategy describes the optimal operation of the DC microgrid as a Markov decision process and uses the continuous interaction between the agent and the DC microgrid environment to adaptively learn energy management decisions, thus realizing the optimal management of the DC microgrid energy. In the strategy training process, the priority experience replay mechanism based on temporal difference error (TD-error) is used to reduce the randomness and blindness of RG-DDPG’s learning and exploration in the DC microgrid operating environment and improve the convergence speed of the energy optimization and management strategy proposed in this paper. At the same time, during the training rounds, the size of the accumulated rewards is used to construct an excellent round set of DC microgrid energy management, strengthen the connection between RG-DDPG agents in the training rounds, and maximize the use of the training value of the excellent round. The simulation results show that the proposed strategy can reasonably distribute energy in the DC microgrid. Compared with the energy management strategy based on deep Q learning (DQN) and particle swarm optimization (PSO), the proposed strategy can reduce the daily average operation cost of DC microgrids by 11.16% and 7.10%, respectively.

Coordinated Restoration Method of Hybrid AC/DC Distribution Networks for Resilience Enhancement

FU Shouqiang, CHEN Xiangyu, ZHANG Libin, QIN Chao, ZENG Yongkang

2023, 56(7):  95-106.  DOI: 10.11930/j.issn.1004-9649.202209024

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Hybrid AC/DC distribution network is an important form of future distribution networks. In recent years, increasingly frequent extreme disasters have posed severe challenges to the safe and reliable power supply of hybrid AC/DC distribution networks. It is urgent to enhance the resilience of hybrid AC/DC distribution networks. Considering the sequential fault and its repairing process caused by extreme disasters, a collaborative restoration method for hybrid AC/DC distribution networks is proposed. Distributed generations (DGs), mobile emergency generators (MEGs), and dynamic reconfiguration of AC/DC distribution networks are fully coordinated to achieve rapid restoration of critical loads under extreme disasters. During the sequential fault occurrence and repairing, the collaborative reconfiguration of the AC and DC portions of the hybrid AC/DC distribution networks is implemented to isolate faults and restore loads by remote-controlled switch (RCS). Additionally, restoration islands are formed based on the dynamic dispatching of MEGs and DGs to ensure the rapid restoration of critical loads and improve network resilience. The second-order cone relaxation technique is adopted to convexify the power flow equations in this optimization model. Consequently, the original model is converted to a mixed integer second-order cone programming which can be solved efficiently. A modified IEEE 33-bus hybrid AC/DC distribution network is employed to verify the effectiveness of the proposed method. The importance of considering MEG real-time scheduling, RCS based dynamic network reconfiguration, and AC/DC part coordination of the distribution network for enhancing the resilience is also demonstrated.

Passivity-Based PI Control Method of MMC with Asymmetric Bridge Arms

CHEN Cheng, XUE Hua, HU Zenghui, WANG Yufei

2023, 56(7):  107-116,124.  DOI: 10.11930/j.issn.1004-9649.202211082

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Considering asymmetric bridge arms of modular multilevel converter (MMC), a passivity-based PI control method based on the bilinear model is proposed to address the dq decoupling transformation errors caused by the fundamental frequency component asymmetry of circulating currents,, which can achieve stable fault phase capacitor voltage, accurate suppression of asymmetric circulating current components and balanced output of three-phase grid-connected currents. Firstly the MMC bilinear model under the condition of asymmetric bridge arm is established in the abc coordinate. Then the linear transformation of the nonlinear system is conducted, in which the control variables are adjusted synchronously with the state variables. In this way the controller design is simplified and the control errors introduced by the dq decoupling transformation are diminished. Based on the global energy dissipation characteristics of the system, a simple passivity-based PI controller is designed to quickly suppress the sub-module capacitor voltage ripple, eliminate the current asymmetry of the bridge arm, and hence ensure the global asymptotically stable operation of the closed-loop control system. The simulation results based on MATLAB has verified that the proposed control method can effectively suppress the adverse effects from the asymmetric bridge arm, and exhibits its capability of fast response, strong stability and high robustness.

Setting Configuration and Adjustment Method of Synchronous Condenser System Under Idling Conditions

SHI Jiyin, SHI Sheng, WANG Da, LU Wanhua, LIN Xiaoyuan

2023, 56(7):  117-124.  DOI: 10.11930/j.issn.1004-9649.202212038

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When connecting the idling condenser to the grid, it is difficult to configure the setting value of the synchronization system to balance the requirements of grid connection success rate and current shock together. In this paper the idling characteristic of the condenser is analyzed, and then the characteristic expression and measurement method of frequency change rate are put forward. Based on the study of the variation characteristics of the voltage of the condenser with respect to the voltage of the power grid, the patterns of the occurrence of the synchronization points are summarized first. It appears that once the frequency differential setting is met, the voltage vector of the condenser should rotate at least 360° with respect to the grid voltage vector. Then the calculation formula for the frequency differential setting is derived. Considering the working condition of synchronization under the frequency differential setting, the formula is also derived for calculating the phase angle differential setting value of synchronous detection relay. The voltage sampling channel is calibrated and the closing time of the circuit breaker is measured by phase verification test with the same source. The measurement of the frequency change rate of the condenser and the adjustment of the lead time are performed by false synchronization test. This method can meet the requirement of 100% grid connection probability while minimizing the shock impact of differential frequency grid connection on the condenser. The feasibility and rationality of this method are verified from the field test results.

Inherent Characteristics Analysis and Optimal Application Scenarios of Type-C Damped Filter

LIU Ke, YANG Fangnan, WANG Yang, LI Jianwu, WANG Xin, YAN Han, WANG Xuan, CHEN Pengfei

2023, 56(7):  125-135.  DOI: 10.11930/j.issn.1004-9649.202203093

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Passive filter is extensively used in new power systems because of its mature technology and low cost, and two types of high pass (HP) filters, i.e. the second-order HP filter and type-c damped filter, are widely used for harmonic treatment However, the existing researches cannot yet clearly reveal the characteristics of each type of filters, which makes it difficult for the designer to select the optimal filter topology under different circumstances. As a result, this paper provides a deep insight into the topological characteristics of the two types of HP filters with focus on the influence of system voltage on the filter cost, and summarizes the inherent characteristics of the two type of HP filters and their optimal application scenarios. Universal conclusions are reached in the paper, which are applicable to different voltage levels ranging from low voltage to high voltage, and helpful to solve the problem of filter topology selection and guide the design of filter packages.

Fault Location Method for Communication Link in Smart Substation Based on Deep Learning

PI Zhiyong, ZHU Yi, LIAO Xuan, LI Zhenxing, FANG Hao, WU Pei

2023, 56(7):  136-145.  DOI: 10.11930/j.issn.1004-9649.202210085

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Aiming at the problem of low troubleshooting efficiency of communication link faults caused by complex links in smart substation, a deep learning based fault location method for intelligent substation communication link of smart substation is proposed. Firstly, based on the network topology of secondary devices in smart substations, a network connectivity matrix is constructed and used as the benchmark, and a fault feature characterization method is proposed for communication link faults. And then, based on the logical relationship between secondary device connection and operation status, a fault sample set of the whole station is constructed. The improved CNN is applied to build the fault location model of the smart substation communication link. Finally, the fault link is accurately located through the fault bay information preliminarily determined by the background information and the model output results. A 220 kV smart substation is taken for case study and some bays of it are taken to construct the fault sample set, and different fault location methods are compared through result analysis. The comparison results show that the proposed location method has higher accuracy.

The Construction of the Professional Dictionary of Relay Protection Defect Text in a Regional Power Grid and Its Natural Language Characteristics Analysis

LIU Zhongshuo, ZHENG Shaoming, TAO Chang, LIU Yimin, CHEN Qian, WANG Shuhong, YU Yiting, XUE Ancheng

2023, 56(7):  146-155.  DOI: 10.11930/j.issn.1004-9649.202302001

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Massive defect text data of relay protection devices is lack of data mining based on professional dictionary. It cannot provide sufficient support for grading, diagnosing, and eliminating relay protection defects, thus unable to meet efficient operation and maintenance needs. A professional dictionary construction method suitable for defects in relay protection devices is proposed, and relevant professional dictionaries are constructed taking a regional power grid as an example. Firstly, relevant defect logs and management protocols are aggregated to form a defect text corpus; secondly, a regular expression-based deactivation word identification method is applied to realize the rejection of irrelevant words in the defect text; then, a combined machine and manual method is used to build a relay protection defect text dictionary; Besides, it adopts latent semantic analysis and decision tree classification to achieve synonym merging. By integrating the deactivation word list, the split word lexicon and the synonym list, a specialized dictionary of protection device defects in the regional power grid is constructed. Finally, the Zipf distribution feature analysis of the professional dictionary and the corpus information entropy analysis before and after using the dictionary are carried out, which shows the effectiveness of the professional dictionary.

Test and Control Technology for Secondary Relay Protection Equipment of Power System Based on Edge IoT

YE Yuanbo, ZHANG Hao, WANG Tongwen, WANG Zhihua, CHEN Yong

2023, 56(7):  156-162,174.  DOI: 10.11930/j.issn.1004-9649.202207053

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In order to solve the problems of low automation degree of substation relay protection test and poor management of test reports, a test and control technology for protection device based on Edge IoT is proposed. Based on the data storage and processing capability of cloud platform, an automatic test architecture based on Edge IoT is designed. The state assessment of protection device based on D-S evidence theory is established by further fusing multi-source information to improve the analysis level of automatic test of protection device. The management and control system forms dual test reports through edge computing and automatic test devices, establishes a mutual correction mechanism on the cloud platform, and adopts hierarchical encryption technology for report information to ensure the security and traceability of the test data. The research is applied to the project site, realizing the automatic testing of protection device, automatic generation and hierarchical encryption of test reports, and improving the efficiency and automation of testing.

New Energy

Remaining Useful Life Prediction and State of Health Estimation of Lithium-Ion Batteries Based on Voltage Data Segment Hybrid Model

YUE Jiahui, XIA Xiangyang, JIANG Daiyu, ZHOU Guandong, XU Zhiqiang, ZHANG Yuan, LV Chonggeng

2023, 56(7):  163-174.  DOI: 10.11930/j.issn.1004-9649.202208122

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The remaining useful life (RUL) prediction and state of health (SOH) estimation of lithium-ion batteries are essential for energy storage safety. The important indicators often focus on battery capacity and internal resistance. However, in practical operation, the capacity measurement requires a complete charge/discharge cycle, and the measurement of internal resistance requires additional equipment. To this end, based on the voltage segment in the constant current discharge condition of the lithium-ion battery, the sharp voltage drop of the initial discharge segment is taken as a new healthy factor. Confronted with the possibility that data of the new healthy factor is polluted by noise, this paper rebuilds the factor data to reduce noise through a multi-order Bezier curve. Then an empirical degradation hybrid model is built with the number of cycles. On this basis, the SOH of the battery is defined by voltage segment, and a new SOH estimation model is proposed. The feasibility and effectiveness of the proposed degradation model and estimation model are verified by the aging data published by NASA and the experimental platform.

Analysis on Operation Value of Electrochemical Energy Storage and Pumped Storage Participating in a Joint Market

LIN Yi, LIN Wei, WU Wei, JIANG Yuewen, LIN Azhu

2023, 56(7):  175-185.  DOI: 10.11930/j.issn.1004-9649.202209015

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To evaluate the operation value of electrochemical energy storage and pumped storage participating in the power market, clarify the cost-benefit mechanism of energy storage, and promote the development and application of the energy storage business model, this paper constructs a joint clearing optimization model of power market, frequency regulation market and reserve market, and applies the electrochemical energy storage and pumped storage to the joint market as the dispatching management tools of the market operators. According to the changes in the total market cost and the daily operating cost of energy storage before and after the participation of energy storage in the joint market, the operational values of energy storage in the joint market is quantitatively compared. The impacts of the two types of energy storage on the market clearing price and the main factors affecting the operational value of energy storage are analyzed through a case study, so as to provide reference for the planning, construction and operation of energy storage.

Differential Protection of Transmission Transformer for Large-Scale Doubly-Fed Wind Farms Based on Detrended Analysis

XU Yanchun, FAN Zhongyao, SUN Sihan, MI Lu

2023, 56(7):  186-197.  DOI: 10.11930/j.issn.1004-9649.202210091

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Since the fault current output from the doubly-fed wind farm has frequency deviation characteristics and contains large harmonic components, when an internal fault occurs in the transmission transformer for the doubly-fed wind farm, the ratio of the second harmonic to the fundamental wave in the differential current of the transformer increases, which makes the differential protection of the transformer face the risk of delay action. Moreover, when the system fails, a large number of non-periodic components in the fault current output from the doubly-fed wind farm will make the current transformer in the transmission transformer more prone to saturation, resulting in reduced reliability of the differential protection of traditional transformers. This paper proposes a differential protection scheme for the transmission transformer for large-scale wind farms based on detrended analysis. Firstly, the sampling current is processed by detrended analysis through the sliding data window to obtain the detrended residual function, and then the slope characteristics of the current waveform are utilized to complete the effective distinction between the magnetizing inrush current and the fault differential current (including the current transformer saturation state) of the transformer. The proposed protection scheme is validated to be applicable under different operating conditions by building a transmission system for the doubly-fed wind farm in PSCAD.

Two-Layer Optimization Operation Model of Cloud Energy Storage Based on Improved Myerson Value Method

WEI Zhenbo, LI Yinjiang, ZHANG Wenwen, YANG Chao

2023, 56(7):  198-206.  DOI: 10.11930/j.issn.1004-9649.202212071

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To deeply explore the role of centralized shared energy storage and distributed energy storage in the future new energy structure, this paper proposes a two-layer optimization operation model of cloud energy storage considering multi-agent value coordination. Firstly, a two-layer cloud energy storage model is built based on the scale effect of shared energy storage and the complementarity of distributed energy storage users. The upper objective function is the optimal daily economic benefit considering the full lifecycle cost of shared energy storage. The lower layer aims at the lowest daily operation cost of the user alliance and is solved by two-layer parallel optimization of analytic target cascading (ATC). To take into account the interests of each participant and the realization paths, the paper puts forward an improved Myerson value method to address the curse of dimensionality caused by cost allocation and user groups of chain alliance. Finally, the simulation results show that the model can further improve the consumption capacity of clean energy in the whole society, and the proposed cost allocation method can yield win-win results, providing references for future user-side large-scale energy storage applications.

Online Monitoring Method of Battery Stack Inconsistency Based on Discharge Quantity of Battery Clusters

ZHANG Yuan, XIA Xiangyang, YUE Jiahui, LIU Daifei, WANG Mingqi

2023, 56(7):  207-215,227.  DOI: 10.11930/j.issn.1004-9649.202211089

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Batteries cannot remain completely consistent during production and the degree of aging is inconsistent in different operating conditions. Therefore, to avoid the “barrel effect” in large-scale energy storage power stations, this paper proposes an online monitoring method of battery stack inconsistency based on the discharge quantity of battery clusters. With the discharge quantity in the energy storage station as a characteristic parameter, the corresponding relationship between the battery stack and the discharge quantity of battery clusters is analyzed quantitatively. Meanwhile, linear fitting is conducted on the two variables to obtain their change rate k and realize the online monitoring of battery stack consistency. The change rate k is recorded as a timing signal and serves as a BP neural network input to achieve short-time prediction and accurately estimate the safe operation of the energy storage power station. Finally, by analyzing the actual operation data of an energy storage power station in Hunan, it is calculated that the MAE is 0.406%; the MSE is 0.002%; the RMSE is 0.489%. All of the values are less than 0.5%, verifying the feasibility and effectiveness of the proposed method.

Technology and Economics

Evaluation and Analysis of Factors Affecting Operation and Inspection Cost of Distribution Network Equipment Assets

LUO Chaoyueling, LI Zhiwei, XU Zhenyu, TANG Xuejun, LI Li, FANG Zhao

2023, 56(7):  216-227.  DOI: 10.11930/j.issn.1004-9649.202302061

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At present, the cost structure of distribution network operation and maintenance is vague, and the management is relatively extensive, which can easily lead to regional allocation imbalance, and the weakness of equipment asset operation and maintenance cannot be reasonably strengthened. A method for evaluating and analyzing the factors affecting the operation and inspection cost is proposed based on the BMA improved grey correlation method. Potential influencing factors are analyzed from the aspects of economic factors, equipment factors, environmental factors, and network structure. Key variables are selected based on the Bayesian model averaging (BMA) method, and the improved anti entropy grey correlation analysis method is used to quantitatively analyze the correlation degree of influencing factors, and identify the weakness that affects the operation and inspection costs. Nine key factors affecting the operation and inspection cost of actual distribution network equipment assets are selected in actual power supply area, and the comprehensive score and weak construction items are obtained. The effectiveness and rationality of this method are verified combined with the specific situation of regional development finally.

Multi-criteria Comprehensive Evaluation of Multi-energy Complementary System Based on AHP-EWM and TOPSIS Method

JIA Kaihua, YU Yunxia, FAN Xiubo, LI Maoxuan, WANG Dong, TANG Cuicui, JI Zhang

2023, 56(7):  228-238.  DOI: 10.11930/j.issn.1004-9649.202212004

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The operation strategy of multi-energy complementary system affects the economy, environment and energy utilization efficiency of power system. To select an optimal operation strategy of the multi-energy complementary system, firstly, the index weights were determined by the integrated weight method combining the analytic hierarchy process and the entropy weight method, and the TOPSIS was introduced to rank the operation strategies. Secondly, the operation strategies of the following thermal load (FTL), following electric load (FEL), and following operation cost (FOC) were analyzed. Finally, the optimal operation strategy of six typical days was determined and a year-round optimum hybrid operation strategy was obtained by optimizing an electricity-gas coupling multi-energy complementary system. The results show that it is better to choose the FEL in the heating season, while it is better to choose the FOC in the cooling season and transition season. It can be concluded from analysis of the annual operation cycle that the hybrid operation strategy has better comprehensive performance than the single operation strategy.