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Table of Content

    05 December 2020, Volume 53 Issue 12
    Construction Path and Key Operation Issues of Electricity Market in China
    MA Li, FAN Menghua, QU Haoyuan, LI Jie, ZHAO Zheng, WU Zechen, CHEN Kening
    2020, 53(12):  1-9.  DOI: 10.11930/j.issn.1004-9649.202007095
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    With further deepening of electricity reform, remarkable progress has been made in construction of China's electricity market. However, there are still multiple challenges, such as long-term coexistence of government-allocated and market-allocated electricity, insufficient and unbalanced development, clean and low-carbon transformation of energy, diversification of market participants and aggravation of interest contradictions, which need to be considered from market design and path planning as a whole. In this paper, the evolution path and models of China's electricity market construction and development are designed in two stages: the near-term and the medium-long-term. Key issues are studied including the connection between government-allocated and market-allocated electricity, the connection between provincial and inter-provincial markets, the connection between long-term and spot markets, the market mechanism to promote new energy consumption, the auxiliary services, the capacity market, and the price mechanism. Relevant measures and strategic suggestions are put forward for further deepening the construction of electricity market in China.
    Influence of UnevenTemperature on Current Distribution in Paralleled Multi-Chips Press Pack IGBT
    DENG Zhenyu, CHEN Minyou, LAI Wei, LI Hui, WANG Xiao, LI Jinyuan, DU Yaoting
    2020, 53(12):  10-17.  DOI: 10.11930/j.issn.1004-9649.202004065
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    The multi-chip parallel press pack IGBT device is a key component in flexible DC transmission equipment. Due to manufacturing processes, loop parasitic parameters and thermal coupling, the internal stress distribution of the device is imbalance, resulting in uneven aging of the device, the temperature distribution uneven, and the current distribution imbalance. This paper focuses on the problem of uneven current distribution caused by different temperature imbalance. First, the causes of uneven current sharing of IGBT devices and the effect of temperature on the uneven current characteristics are analyzed. Then, the single-chip press pack IGBT devices are used in parallel to simulate the effect of the uneven temperature distribution which is used for the experiment about the effect of temperature imbalance degree on the current distribution of the multi-chip devices. Finally, the relationship between the temperature difference and the degree of current imbalance is verified by experiment. It lays a scientific and technical foundation for improving the operational reliability of the device and cognizing the failure mechanism of the press pack IGBT.
    A Review of Reverse Bias Test for Power Device in High Temperature, High Humidity and High Voltage Conditions
    WANG YanHao, DENG Erping, HUANG Yongzhang
    2020, 53(12):  18-29.  DOI: 10.11930/j.issn.1004-9649.202005133
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    In outdoor working conditions, the lifespan of power device would be shortened by moisture invasion and erosion of the high humidity environment. The maximum 80 V bias of traditional high humidity high temperature reverse bias test (H3TRB), which is used to assess the reliability under humid environment, cannot meet the demand of high voltage high power device accelerated aging test, thus the high-voltage high humidity high temperature reverse bias test (HV-H3TRB) has been carried out in recent years. However, both the research progress and the key problems are unclear, which turns to the research development direction unclear. In this paper, the mechanism of moisture invasion into power device and the mechanism of moisture corrosion on chip surface are discussed in detail. Then, the existing research status is discussed and summarized in terms of research object and method, device failure analysis, and electrical aging characteristics. Afterwards, according to the changes of device structure before and after aging, the optimal design of anti-moisture of chip layer terminal, passivation layer and packaging material are summarized. Finally, the future development direction of related research is pointed out.
    Design and Development of 4500 V Trench Gate IGBT
    LI Li, WANG Yaohua, GAO Mingchao, LIU Jiang, JIN Rui
    2020, 53(12):  30-36.  DOI: 10.11930/j.issn.1004-9649.202006300
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    In this paper, a 4500 V trench gate IGBT chip was developed, so as to improve the single chip current density as well as to master the technology of high voltage trench gate IGBT. Using the TCAD simulation software, experiments were carried out on the aspects of the substrate material, carrier stored layer design, trench width, trench depth and dummy trench gate structure, whose impacts on the chip performance were analyzed. According to the overall design goal, the chip structure and process parameters were determined, and the 4500 V trench gate IGBT chip was fabricated and verified. The test results of 4500 V trench gate IGBT chip can meet the design expectation, and its key parameters, such as rated current, saturation voltage, turn-on switching energy and turn-off switching energy, have been significantly improved compared with the planar gate IGBT chip.
    Thermal Resistance Distribution Experiment of Parallel Sub-Module in Press-Pack IGBT Device
    HAN Lubin, LIANG Lin, KANG Yong
    2020, 53(12):  37-44.  DOI: 10.11930/j.issn.1004-9649.202007196
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    In the rigid Press-Pack IGBT module, the pressure distribution of parallel chips determines the contact thermal resistance and contact electrical resistance directly. However, the distribution of pressure and thermal resistance cannot be measured during the normal operation. In order to analyze the pressure distribution and thermal resistance distribution of each sub-module in the Press-Pack IGBT module, the method of measuring the thermal resistance distribution of the parallel sub-modules of the Press-Pack IGBT module is proposed, which is based on the devices characteristics and thermal resistance test. Then, the distributions of thermal resistance under different pressures and currents are studied in detail. The experimental results show that the distribution of junction temperature, current and thermal resistance among the parallel sub-modules in the IGBT module are greatly dispersed due to the difference of external pressure, devices characteristics and connecting conductors. The proposed measurement method could effectively verify the distribution characteristics of junction temperature, thermal resistance and pressure of the Press-Pack IGBT module under certain packaging conditions.
    Broadband Dielectric Properties and Temperature Effects of Silicone Gel for IGBT Device Encapsulation
    MAO Yuan, LI Xuebao, XU Jiayu, ZHAO Zhibin, CUI Xiang
    2020, 53(12):  45-54.  DOI: 10.11930/j.issn.1004-9649.202007124
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    Silicone gel materials are used as packaging material for IGBT devices. Under the operating conditions, the devices are subjected to a repetitive on-off voltage which corresponds to the wide spectrum, and the device loss will cause temperature rise. In order to accurately analyze the internal electric field characteristics of the devices, the dielectric properties of silicone gel in a wide temperature range were studied by frequency domain dielectric spectroscopy. The broadband dielectric spectroscopy of silicone gel at different temperatures was achieved by using interdigital electrodes. Then the Cole-Cole dielectric model was adopted to fit the experimental data, and the influence of temperature on the characteristic parameters of the Cole-Cole model was analyzed. The results showed that frequency and temperature have a great influence on the dielectric properties of silicone gel in the frequency domain. At low frequency and high temperature, the real and imaginary parts of the complex permittivity of silicone gel materials increase significantly. In the Cole-Cole dielectric model, the relationship between DC conductivity σ0, space charge polarization intensity Δε1 and the temperature are governed by the Arrhenius equation, and the thermal activation energy is 0.233 eV and 0.691 eV, respectively. The relaxation time τ1 and τ2 are different at low temperature and increase obviously at high temperature. The recognition of dielectric properties of silicone gel materials for semiconductor device encapsulation can provide basic data support for internal electric field analysis and insulation design of devices.
    A Review of Thermal Design for IGBT Module
    LIU Guoyou, WANG Yangang, LUO Haihui, QI Fang, LI Xiang, WU Yibo
    2020, 53(12):  55-61,74.  DOI: 10.11930/j.issn.1004-9649.202007137
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    In this paper, the thermal characteristics and thermal design of IGBT module are reviewed. Firstly, the thermal network model and its dependence on the packaging material’s thermal performance and dimensions are addressed. Then, the thermal design of IGBT module is investigated in terms of semiconductor chip, packaging structure and material. Finally, the main thermal design aspects of conventional IGBT module and new press-pack IGBT module are presented.
    Mechanical Stress Analysis in High Power Press Pack IGBT
    TANG Xinling, LIN Zhongkang, ZHANG Xizi, YAN Shumin, SU Bing, WANG Liang, HAN Ronggang, SHI Hao
    2020, 53(12):  62-74.  DOI: 10.11930/j.issn.1004-9649.202005029
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    Mechanical stress is one of the key factors affecting the electrical characteristics, thermal characteristics and reliability of high-voltage high-power press-pack IGBT devices. First of all, in this paper, from the perspective of chip and package structure design, the research status and key design techniques of the uniformity of the mechanical pressure distribution of single-chip and parallel multi-chip are introduced. Secondly, from the perspective of packaging technology, the influence of compliant contact, rigid contact and different soldering forms on the mechanical stress distribution of the chips are compared. Finally, combined with the characteristics of the press-pack structure, and based on a new type of edge termination structure, a new packaging technology solution is proposed, which can effectively improve the uniformity of the pressure of single chips and parallel chips, so as to provide a reference for the design of high-voltage high-power press-pack IGBT devices.
    Optimal Configuration of Multi-Energy Complementary System Considering Full Life Cycle
    KOU Lingfeng, JI Yu, WU Ming, NIU Geng
    2020, 53(12):  75-82.  DOI: 10.11930/j.issn.1004-9649.202006291
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    Aiming at the optimization configuration of multi-energy complementary systems including wind power generation, photovoltaic power generation and energy storage systems, this paper proposes a full life cycle optimization configuration method for multi-energy complementary systems considering system interaction with distribution network and demand-side response costs, Constructed a two-layer optimization model: the upper layer performs global optimization with the goal of minimum annual investment cost, and determines the optimal configuration scheme and energy storage output range of the multi-energy complementary system; the lower layer is established with daily operating costs and renewable energy unutilization as the goals. Multi-energy complementary system and multi-objective economic scheduling model is established. Consider independent and grid-connected multi-energy complementary systems respectively. Taking actual scenery data as an example, a calculation example verifies the correctness and effectiveness of the proposed optimization configuration strategy, and quantitatively analyzes the optimization of the operation mode of multi-energy complementary systems. Impact of configuration strategy.
    Optimization Strategy of Microgrid Hierarchical Scheduling Considering Electric Vehicles User Satisfaction Degree
    YU Huiqun, YIN Shen, ZHANG Hao, SHI Shanshan, PENG Daogang, CAI Guoshun
    2020, 53(12):  83-91.  DOI: 10.11930/j.issn.1004-9649.202005079
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    In this paper, a hierarchical scheduling optimization strategy considering electric vehicle user satisfaction degree is proposed for electric vehicle cluster in residential microgrid. Microgrid scheduling optimization process can be divided into load layer and source storage layer. The load layer utilizes the energy storage characteristics of electric vehicles to smooth the peak of the original load in the microgrid under the premise of ensuring user satisfaction of electric vehicles. Renewable energy is used to support the load of the microgrid in the source storage layer, and the excess part is absorbed by the dispatchable electric vehicle, which makes the comprehensive cost of the microgrid minimized. The improved ant lion algorithm is used to solve the model of the source storage layer. Lastly, verify through an example. The result shows that the strategy greatly improves the economics and reliability of microgrid compared with the disordered charge of electric vehicles. Meanwhile, the satisfaction degree of electric vehicle user is improved.
    Comparative Analysis of Integrated Energy Service Implementation Paths in Typical Districts and Counties
    SUN Qiang, CHEN Qian, PAN Hangping, YONG Weizhen, CHEN Yang, WANG Jianxue
    2020, 53(12):  92-100,109.  DOI: 10.11930/j.issn.1004-9649.202002091
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    In recent years, integrated energy services have been greatly improved as the result of the prominence of energy and environmental problems, changes in user energy demand, and breakthroughs in key technologies such as "Internet plus" and energy storage. Quite a few works can be found on integrated energy systems and integrated energy services. However, little of them has focused on the district-level. In this paper, a typical district classification method based on TOPSIS model was proposed, which divided districts and counties into six types. According to the characteristics of districts and counties types, implementation routes of integrated energy services were planned. The proposed methods were applied in the case studies of several typical counties, including Baoying, Jiangyin, Yangzhong, Xuanwu, Wuzhong and Tongshan.
    Economic Dispatch of Fully Renewable Energy System Considering Uncertainty of both Energy Source and Load
    YU Fan, NIU Honghai, LI Bing, ZHAO Yang, CHEN Pei, GUAN Xiaochen, YANG Yu
    2020, 53(12):  101-109.  DOI: 10.11930/j.issn.1004-9649.202003206
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    This paper established a fully renewable energy system which takes solar energy, wind energy and biomass energy as primary energy and meets the demand of electricity, heat and cooling loads. Considering the uncertainty of both energy source and load, a day-ahead economic dispatch model based on two-stage robust optimization was built and solved by column constraint generation (C & CG) algorithm. The simulation results show that renewable energy can be fully consumed by giving full play to its multi energy complementary characteristics. At the same time, the conservatism of robust optimization can be effectively improved by adjusting the uncertainty adjustment parameters, so as to improve the operation economy of the energy system and ensure safe and stable operation.
    Coordinated Control Technology for Regional Integrated Energy
    HUA Guanghui, HU Wei, JING Jiangping, WU Yi, SHA Zhou, CHEN Weidong, XU Xiaohui
    2020, 53(12):  110-118.  DOI: 10.11930/j.issn.1004-9649.201911100
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    As an important part of energy internet and the main supporting form of social energy, the integrated energy system (IES) is the important development direction for the new round of energy transformation. As the extension and expansion of power grid dispatching system, the coordinated control system of regional IES performs the lean and ubiquitous dispatching control of multi-energy flow for related energy equipment in the region. Based on the three-layer architecture of the IES, the important role of the regional IES is analyzed. The topological relationship, and the hardware and software structure of regional integrated energy coordinated control system are proposed. The system platform services, basic applications, and advanced application functions are studied. A software for the regional integrated energy coordinated control system is developed, and has been applied and verified in Tongli new energy town integrated energy demonstration area. It will be further promoted and applied in the future.
    Optimal Operation of Integrated Electricity-Gas System Considering Uncertainty of Integrated Demand Response
    LUO Jinman, ZHAO Shanlong, FENG Youjun, LIU Zhuoxian, DONG Wenjie, YANG Yanhong
    2020, 53(12):  119-126.  DOI: 10.11930/j.issn.1004-9649.202002127
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    In order to effectively analyze the influence of integrated demand response (IDR) uncertainty on the security of system operation, an optimal operation model for integrated electricity-gas system (IEGS) considering the IDR uncertainty is proposed by taking the IEGS as an example. Firstly, according to the implementation characteristics of energy price-based IDR project, different types of IDR uncertainty models are established using the fuzzy method and probability method comprehensively. On this basis, the point estimation method is used to calculate the probabilistic energy flow of the system, and the calculation results are taken as chance constraints to minimize the operation costs of IEGS and ensure the security of the system. Finally, by taking the IEGS consisting of improved IEEE-33 power system and 20-node natural gas system for case study, the effectiveness of the proposed model and method are verified, and the wind power accommodation capacity of the system is evaluated under uncertainty context.
    Method on Hierarchical Coordinated Optimization of Electrical Energy Storage and Thermoelectric Power for Accommodation of Curtailed Wind Power
    YANG Yulong, LI Pai, HUANG Yuehui, WANG Guilin, ZHOU Yigang
    2020, 53(12):  127-135.  DOI: 10.11930/j.issn.1004-9649.202002130
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    Large scale combined heat and power (CHP) units exist in Northern China, but their peak regulation capacities are limited due to the heating demand in winter. This results in the wind power curtailment problem in winter. Adding energy and thermal storage devices is regarded as an important method to improve peak regulation capacities of CHP units. This paper studies the coordinated optimization method of CHP units, energy and thermal storage under the ancillary service market environment. To maximize the thermal storage benefit and peak load regulation benefit of electrical energy storage and CHP units respectively, this paper builds a hierarchical coordinated optimization model that considers wind power accommodation maximization, heating demand constraint and the operating constraints of CHP units, electrical and thermal energy storage. Through the simulation testing, the proposal can coordinate the operation between the electrical energy storage device and thermal storage device, and take full advantage of multi-day adjustment ability of thermal storage device, so as to increase the system operating benefits in power market and reduce wind power curtailment. These research results have reference value for solving wind power curtailment problem in winter under current power market environment in Northern China.
    Study on Reasonable Curtailment Rate of Renewables under Certain Renewable Energy Consumption Quota Obligation
    GAO Lei, SU Xinyi, LIU Shiyu
    2020, 53(12):  136-142.  DOI: 10.11930/j.issn.1004-9649.202004031
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    With the gradual increase of renewables in power system, the flexibility of power system is reduced. To realize the full consumption of renewables, the power system needs to dispatch a large amount of peaking power to accommodate the renewables, which will not only reduce the safety and economy of the power system, but also hinder the clean low-carbon transitionof the power system. In this paper, from the perspective of the overall power consumption cost of the whole society, we propose a method to calculate the reasonable curtailment rate of renewables under certain renewable energy consumption quota obligation. Through simulation analysis, the reasonable curtailment rate of different provinces is calculated, while the influencing factors is also studied. It is assumed that this study can provide guidelines for the planning and operation of the power system with high proportion of renewables.
    Optimal Configuration and Economic Study of Hybrid Energy Storage System in Wind and Solar Power Plants
    LIU Yongqian, LIANG Chao, YAN Jie, ZHANG Jing
    2020, 53(12):  143-150.  DOI: 10.11930/j.issn.1004-9649.202002046
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    Energy storage system (ESS) is important to solve the problem of large-scale renewable energy integration. However, in addition to its high investment cost, operation and maintenance loss, the technical and economic parameters of ESS’s vary significantly between different types. Therefore, it is of great significance to study the optimal configuration and conduct economic analysis of different types of ESS’s. In this paper, a hybrid configuration optimization method for capacity-based and power-based ESS’s in wind and solar power plants is proposed to maximize the net benefit of the ESS in its full life cycle. Based on the actual operation data of wind and solar power plants in Zhangjiakou and the actual parameters of three mainstream ESS’s, the influence of different sensitivity factors on the selection and capacity of ESS is analyzed. The results show that the economic performance of capacity-based ESS is more sensitive to its price changes while the liquid flow batteries combined with ultracapacitors demonstrate the best economics.
    A Review of UHV AC GIL Ex-factory Test Technology
    CHEN Shuang, LIU Yan, BIAN Chao, ZHANG Pengfei, CUI Boyuan, CHEN Yun, XU Jiazhong
    2020, 53(12):  151-158.  DOI: 10.11930/j.issn.1004-9649.202004008
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    Based on the application of UHV gas-insulated metal-enclosed transmission line(GIL)in the Sutong GIL Utility Tunnel Project, this paper firstly introduces the structural characteristics of UHV GIL, and analyzes its main technical parameters, type test and performance requirements for ex-factory test. And then a partial buckle dynamic vacuum positive-pressure helium leak detection method is proposed, which can effectively improve the efficiency of the UHV GIL gas sealing test. In addition, a four-station insulation test switching tool and a SF6 gas-insulated tank-type impulse voltage generator that meets the requirements of the UHV GIL standard lightning impulse voltage withstand test are introduced. The time for ex-factory insulation test of the UHV GIL is reduced to 1/4 of the traditional method. The testing practice introduced in this paper can provide a reference for the large-scale application of GIL.
    Aging State Evaluation of Oil-Paper Insulation Based on Fusion of Gray Texture and Oil Gas Features
    LIU Dongchao, LIN Yu, YUAN Hui, WANG Shuai, JIANG Min, YU Hua, LI Haitao
    2020, 53(12):  159-166,197.  DOI: 10.11930/j.issn.1004-9649.202004095
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    Aiming at the problem of insufficient precision of aging information obtained by single partial discharge(PD) feature discrimination, a D-S evidence fusion recognition method based on PD gray texture and oil-gas features is proposed to analyze the aging state of oil-paper insulation. Firstly, an air gap model of artificial oil-paper insulation is constructed through experiments to simulate the actual operation environment inside the transformer. Next, the PD signals of seven aging levels of oil-paper insulation and the corresponding gas content in oil are collected. Then, the gray texture features, statistical features and oil-gas features of each aging level are extracted, and subsequently identified using the support vector machine. The identification results of gray texture features and oil-gas features are then input into the D-S evidence fusion framework for further recognition and analysis. Finally, the recognition results are compared with the single feature and other two-feature fusion results. The experimental results show that the D-S evidence fusion method based on gray texture feature and oil-gas feature can better identify the aging state of oil-paper insulation.
    Identification Method for Incipient Intermittent Arc Ground Fault of High-Voltage Cables
    ZHOU Zhengxiong, XIA Xiangyang, ZHU Peng, LI Mingde, HUANG Hai, CHEN Shanqiu, XIA Junshan, WANG Ruiqi
    2020, 53(12):  167-176.  DOI: 10.11930/j.issn.1004-9649.202004153
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    Persistence partial discharge accelerates aging of cable insulation, and the insulation defect point will produce an instantaneous intermittent grounding arc before its complete breakdown. For the incipient fault of this type of cables, a recognition strategy is proposed based on combination of change point detection and improved adaptive neural network under time domain sequence. Firstly, the non-parametric bilateral CUSUM algorithm is used to monitor the cumulative sum of the positive and negative offsets of the three-phase current to determine the abnormal phase. And then the improved ADAline weight formula is used to express the harmonic content of the transient abnormal phase, and the amplitude variation trend of harmonic content curves and its transient duration exceeding the set threshold can be used to identify the half-cycle and multi-cycle incipient faults of cables. The PSCAD / EMTDC simulation results show that the strategy has a good distinction for constant resistance faults or other overcurrent disturbances. Finally, the on-site monitoring data of live cables have verified the algorithm's fault recognition rate and anti-interference.
    A Climbing System of Aerial Work Assistance Robot for UHV Tower
    TANG Shiyang, MEN Yongsheng, YU Zhen, GUAN Cheng, XU Yonggang
    2020, 53(12):  177-182.  DOI: 10.11930/j.issn.1004-9649.202006009
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    Aerial work is a high risk procedure in power grid construction and operation. It is a vital issue to protect the workers’ safety while working on high tower or climbing tower. In this paper, a safety protection strengthening method is proposed based on tower-climbing robot assistance, and an iron tower climbing system with high flexibility and good obstacle-crossing ability is designed. The required functions are realized with the 3-leg silkworm-like main structure and the magnetic/clamping dual function craws. Through laboratory based experiment, the proposed system was proven to be able to move vertically or horizontally and turn around, with an ability to cross a 180 mm high and 400 mm wide obstacle. The proposed climbing system structure is applicable to the power tower climbing for assisting various aerial works.
    A Practical Method for Analyzing Feasible Generation Region under Security Constraint of Key Transmission Line Section
    ZHOU Xingyu, PAN Xueping, WANG Zhengfeng, CHEN Dezhi
    2020, 53(12):  183-189.  DOI: 10.11930/j.issn.1004-9649.202001060
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    Under power market circumstances, the monthly safety check of dispatch schedule faces many problems, such as long time span, poor forecast accuracy of power load and new energy power, and high uncertainty of trading energy. Therefore, a practical constructing method for feasible generation region is proposed in this paper. Firstly, the generator units in the whole grid are clustered based on the active power sensitivity of each generator unit relative to the key transmission line, and combined with the unit's geographic location. Secondly, the base power flow determination method for building feasible generation region is proposed. Furthermore, the feasible generation region of leading generator cluster under different load levels is built with the total active power output of leading cluster and the total load set as the horizontal coordinates and vertical coordinates, respectively. Finally, the feasible generation region is revised on-line according the power system’s real operation condition. A provincial power system is used to validate the feasibility of the proposed method in this paper.
    Model and Algorithm of the Robust Generation Schedule Based on Confidence Risk Measurement
    LI Pengfei, HOU Yanqiu, ZOU Jiaxin, ZHANG Shujie, LI Pai, LIN Jikeng
    2020, 53(12):  190-197.  DOI: 10.11930/j.issn.1004-9649.201902078
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    Aiming at the uncertainty and operational risk of grid operation scheduling brought about by large-scale wind power integration, a new confidence-risk-measurement-based model and its solution algorithm is proposed for robust generation schedule. The paper firstly proposes a new risk measurement, namely confidence risk measurement (Riskα). For a given confidence level α and the corresponding wind power forecasting interval, the sum of the risk of wind curtailment and the risk of load shedding constitutes the confidence comprehensive risk measurement, which can be used for quantifying the risk caused by actual wind power surpassing the acceptable wind power threshold. And then, taking the sum of generation cost and confidence risk minimum as optimization objective, a new robust generation schedule model and its decomposition algorithm are proposed to simultaneously optimize the generator unit portfolio decision-making and the wind power acceptable threshold, thus making the formulated generation schedule achieve a balance between economy and operational risk. A case study has proved the correctness and effectiveness of the proposed model and algorithm.
    Industrial Design of High Voltage Flexible DC Converter Valve
    QIAO Li, XIE Jian, LI Yunpeng, GUO Chunyi
    2020, 53(12):  198-205,222.  DOI: 10.11930/j.issn.1004-9649.201911061
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    To improve the product quality and added value of flexible DC converter valve, it is meaningful to investigate its corresponding industrial design method. Based on analyzing the design of the sub-module, valve module and valve tower of a ±320 kV flexible DC converter valve, a reasonable design method is proposed from the aspects of function, structure, modeling, man-machine, assembly, cost, coating and so on. The industrial design of ±500 kV converter valve is innovated by adopting a technology and design concurrent process and a function-and-ergonomics based "subtraction" design method. Through analysis and experimental verification, the design schemes have been applied to the engineering prototype. Through comparison of design schemes, an optimal industrial design scheme is obtained, which can ensure a better quality of design schemes from the perspective of knowledge. Meanwhile, it is of significance for product design innovation and new technology industrialization to integrate the industrial design into the high-tech research and development process.
    Humidity Control of RMU Based on COMSOL Simulation Analysis
    WANG Yinchao, DING Yinmei, LI Weibin, YANG Yong, WANG Yueqiang, WANG Hugen, QIAO Fei, WANG Junsheng, XIE Yong, YU Jiamin, LU Zhongxin
    2020, 53(12):  206-213.  DOI: 10.11930/j.issn.1004-9649.201903057
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    The long-term operation of ring main unit (RMU) in humid condensation environment will lead to the decrease of insulation strength of equipment, which will result in discharge and breakdown faults, and further shorten the service life of equipment. Therefore, it is very necessary to ensure a good operation environment for RMU. Semiconductor condensation dehumidification is an emerging dehumidification technology that controls the humidity in the cabinet by condensing moisture and discharging it out of the cabinet. In this paper, the COMSOL simulation software is used to simulate semiconductor condensation dehumidification. The air flow field, heat field and water transport in the dehumidifier are coupled to study the distribution changes of flow field, temperature and relative humidity after the installation of the dehumidifier, as well as the influence of dehumidifier installation position on dehumidification effect. The results show that the temperature inside the RMU changes little after the installation of the dehumidifier, the relative humidity can be reduced from 90% to 50% in about 11h, and the dehumidification effect is the best when the dehumidifier is installed at the bottom of the cabinet. The results of the simulation are verified by experiments. In this paper the influence of installation position of dehumidifier on temperature and humidity distribution and dehumidification effect in RMU is given, which can provide a reference for installation of dehumidifier in RMU.
    Analysis and RTDS Simulation on Suppression Methods for TV Fuses Frequently Blown
    GUI Yuan, CHEN Fan, ZHU Yong, QI Weiqiang, YAO Yuhai, REN Zhigang
    2020, 53(12):  214-222.  DOI: 10.11930/j.issn.1004-9649.201902092
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    Potential transformer (TV) is an important equipment for measurement and protection in distribution network. The high voltage side of TV is usually equipped with fuse for protection, but abnormal fuse blown often occurs, affecting the safety of power system. In order to solve this problem, this paper analyses the causes of the fault from the circuit principle, and verifies the theoretical analysis using RTDS simulation platform, and obtains the voltage-current characteristics under abnormal conditions such as ferromagnetic resonance and under-frequency non-linear oscillation. An improved method for resonance elimination is put forward and analyzed, and proves valid. In view of its limitations, it is proposed to combine the proposed method with the high saturation point TV method, which can better suppress over-voltage and over-current. Finally, on this basis, several existing countermeasures for fuse blown are verified and compared, and the feasibility of various schemes is summarized.
    Evaluation Model of Synchronous Line Loss Data Quality Based on Penalty Variable Weight RDA
    WANG Fangyu, LIU Wenying, CHEN Xinxin, WANG Weizhou, XING Zhou
    2020, 53(12):  223-231.  DOI: 10.11930/j.issn.1004-9649.202003151
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    The evaluation of synchronous line loss data quality is very important for line loss data management and line loss analysis. In view of the contradiction between the accuracy and efficiency of line loss data quality evaluation, a novel evaluation model of line loss data quality based on penalty variable weight “rank sum” difference assessment (RDA) is proposed. Firstly, based on the traditional “rank sum” test, which does not depend on sample size and index selection, a RDA model is established to directly evaluate the overall quality of synchronous line loss data. Secondly, using the difference probability density function of the “rank sum” difference data series as the index, the weight of RDA is modified, with consideration of the influence of the number and magnitude of abnormal data on the data quality evaluation. And the method does not depend on the selection of indicators and the sample size. Finally, the simulation of Gansu grid actual operation data proves the validity and superiority of the evaluation model of synchronous line loss data quality based on penalty variable weight RDA proposed in this paper.
    Energy Transition Path for Urban Areas under New-type Urbanization: A Case Study on Suzhou City Wuzhong District
    ZHU Chanxia, XI Weimin, SUN Qiang, CHEN Jiejun, XIE Dian, CHEN Qian, SUN Zhihuang
    2020, 53(12):  232-240.  DOI: 10.11930/j.issn.1004-9649.201911057
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    Urbanization is closely related to energy development. Based on a case study of Suzhou city Wuzhong district, the urbanization characteristics of Wuzhong district are analyzed from the aspects of history, geography, population and economical industry. Meanwhile, the district’s basic conditions, such as location situation, energy resources, energy consumption, energy technology utilization and ecological environment, are also analyzed. At last, the energy transition path for Wuzhong district is proposed from 7 dimensions, including social economic development, infrastructure, industrial structure, urban function & morphology, ecological environment, governance level and cultural concept.
    Development Status and Policy Suggestions for District Energy Integration
    HUO Molin, GUO Lei, ZHANG Zhe
    2020, 53(12):  241-247.  DOI: 10.11930/j.issn.1004-9649.202005095
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    The district energy integration of multi-energy systems improves the efficiency of district energy use, and strengthens the local consumption of renewable energy, and reduces pollutant emissions. The development of district energy integration needs more effective policy measures. Firstly, this paper systematically analyzes the current development status of district energy integration in China, and summarizes the characteristics of the current development from four aspects including investors, technology application, key market and relevant policies. And the paper also identifies the existing key problems, which include technical problems, policy problems and operation problems. Then the policy measures and experience for solving these problems in foreign countries, including planning, regulations, subsidy policies, price policies, demonstration projects, are reviewed. At last, the paper puts forward four policy suggestions for the development of district energy integration in China based on the actual situation.
    Impact of COVID-19 on China's Total Electricity Consumption in 2020 and Its Trend
    LIU Qing, WU Chenrui, ZHANG Chuncheng, WU Shanshan, WANG Xiang, JI Guoqiang
    2020, 53(12):  248-257.  DOI: 10.11930/j.issn.1004-9649.202007074
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    Electricity consumption is an important boundary condition for power grid companies to formulate medium- and long-term electric power planning and annual comprehensive plan. It is of great significance to accurately measure the impact of the COVID-19 epidemic. This paper constructed a calculation and prediction model for the impact of the COVID-19 epidemic on electricity consumption, designed the benchmark and risk scenarios, calculated the impact of the epidemic and policy factors on electricity consumption from the dimensions of total electricity consumption, sector, industry, region and province, and predicted the growth trend of electricity consumption in 2020. The results show that the epidemic and policy factor is expected to reduce the growth rate of electricity consumption in 2020 by 2.6~3.3 percentage points in the business region operated by the State Grid Corporation of China (SGCC). The outbreak of the COVID-19 epidemic has had a significant impact on electricity consumption. The epidemic situation should be closely followed and rolling adjustment be made on the prediction results.
    Study on Economic Benefits of Electric Vehicle Battery Swapping Station Participating in Power Market Auxiliary Service
    LI Jie, YANG Bing
    2020, 53(12):  258-262,269.  DOI: 10.11930/j.issn.1004-9649.202009125
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    The battery swapping mode can improve the operation efficiency of electric vehicles(EVs) and achieve better interaction with power grid. This paper took the EVs battery swapping station as the research object, analyzed the operation mode of the station, established an energy conservation model and an economic income model, and explored the feasibility and potential of improving the economic income of the exchange station via auxiliary service in power market. Then, the influence of key factors such as battery parameters and battery ratio on the revenue was analyzed. The results show that, only by increasing the number of batteries in the station, the revenue cannot be effectively improved. However, when the per kilowatt hour cost of the power battery is reduced by about 10% or the number of cycles is increased by about 15%, the investment income balance can be realized, and the impact of increasing the cycle times of power battery is greater than that of reducing the price of kilowatt hour.
    Study on the Emission Characteristics of Organic Components in Condensable Particulate Matter from Low-Low Temperature Electric Precipitator and Sea Water Desulfurization
    LIU Xiaomin, WANG Lele, HUANG Jianxun, HUANG Rongting, XU Jizhuang, KONG Fanhai, XIE Jiannan, LI Jinjin, YANG Linjun, ZHANG Fajie, HE Chuan
    2020, 53(12):  263-269.  DOI: 10.11930/j.issn.1004-9649.202005153
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    As the emission of condensable particulate matter (CPM) could exacerbate haze pollution, recently it has received more attention. In this study, CPM and its organic components were tested at different sampling sites of a flue gas purification system under the Coal 1 and Coal 2 combustion conditions, respectively. The top 10 organic components in CPM were analyzed. The results show that under the Coal 1 and Coal 2 combustion conditions, the mass emissions of CPM at the stack inlet are 4.2 and 5.6 mg/m3, respectively, and the removal efficiency of CPM by pollution control facilities after ultra-low emission transformation are 97.21% and 98.18%, respectively. In particular, the removal rates of the organic CPM by the low-low temperature electrostatic precipitator (LLTESP), the sea water wet flue-gas desulfurization (SWFGD) and the wet electrostatic precipitator (WESP) are 71.82%, 56.36% and 76.61% by average, respectively. Among them, LLTSEP exhibits general removal effect on esters, hydrocarbon and all other organic compounds. In comparison, SWFGD excels in the removal of the hydrocarbon compounds, while WESP has remarkable performance on reducing ester compounds.
    Serial Negative Synergy Effects in Synergetic Treatment for Flue Gas Pollutants
    GAO Peirong, YAN Zhiren, YANG Jun, MA Xiaohua, ZHAI Mingqiu
    2020, 53(12):  270-276.  DOI: 10.11930/j.issn.1004-9649.202005104
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    With the applications of synergetic treatment technology for flue gas pollutants increasingly popular in coal-fired power plants, the adverse effects among individual equipment in the synergetic treatment process are becoming more prominent such that the decline of equipment capacity or incremental emission of pollutants are also observed. In this paper, such negative synergy effects are analyzed, and a 350 MW coal-fired power unit is studied by means of performance testing, laboratory testing, operation diagnosis and other methods. The results show that there exists serial negative synergy effects, that is, the negative synergy effects of upstream equipment continuously encroach on the pollutants treatment capability of themselves or downstream equipment, which eventually causes insufficient pollutants treatment capability. At last, suggestions on controlling and elimination of the negative synergy effects are also presented.
    Performance Analysis and Adjustment of Thermocompressor in Exhaust and Waste Heat Utilization System of 330 MW Air Cooling Unit
    HUANG Zhikun, CEN Lingshan, LI Zhihua, LI Yang, WANG Enzhen, ZHANG Pan
    2020, 53(12):  277-283.  DOI: 10.11930/j.issn.1004-9649.202001094
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    This paper introduces the configuration of the three-stage cascade exhaust and waste heat utilization system of the direct air cooling unit. In particular, the component structure and working principle of its most critical equipment, i.e., the thermocompressor, is elaborated and the key factors affecting the thermocompressor performance are analyzed. Then the orthogonal testing is carried out on the three-stage cascade exhaust and waste heat utilization system of a 330 MW coal-fired direct air cooling unit in a power plant. The analysis on the test results show that the boost ratio of the thermocompressor has significant influence on its ejection ratio. In addition, the verification test result indicates the consistency between the optimal scheme obtained from the orthogonal testing and the actual operation. At last, through the testing of effect of various boost ratio on the ejection ratio, it is concluded that whenever the boost ratio is outside of its designed range, either higher than the upper limit or lower than the lower limit, the ejection ratio will all drop down greatly. Therefore, the boost ratio should be strictly controlled within the designed range during practical operation.
    Case Analysis of Several Atypical Faults of Large Turbo-Generator Set
    ZHANG Xueyan, QU Jie, HE Guoan, ZHU Pengbo, JIANG Guangzheng, PAN Bo
    2020, 53(12):  284-292,300.  DOI: 10.11930/j.issn.1004-9649.202003147
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    This paper presents several atypical fault cases of large steam generator set caused by installation or maintenance mistakes in recent years. The fault symptoms, causes and consequences are described and analyzed in details, which involved axial displacement overrun, sudden change of turbine output and thermal parameters, or abnormal vibrations. The analytical procedures and experience of the cases can provide reference for the analysis of faults and accidents as well as the installation and maintenance guide of the unit in the future.
    Modeling and Optimization for Single-Sequential Valve Switching Process Based on Reverse Segment Decoupling
    QU Xiaohe, ZHUANG Yifei, ZHANG Xing, WU Haicheng, ZHANG Jian, LI Da
    2020, 53(12):  293-300.  DOI: 10.11930/j.issn.1004-9649.202004163
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    After long period of operation, the flow characteristics of governors in the generator unit may deviate gradually from its original values, thus the pre-set DEH parameter values are no longer in line with the actual flow characteristics. Eventually it will cause substantial load fluctuation during the single-sequential valve switching process, which will compromise the security of unit operation. This paper proposes the simplified modeling and related solution methods for the flow characteristics of governors, and then designs a flow characteristics optimization scheme based on reverse flow segments. Then the scheme is applied in a 320 MW circulating fluidized bed boiler for case studies and testing. The experimental results show that the matching degree of the flow characteristics under single-sequential valve operation mode has been greatly improved through the optimization of the governor parameters, such that the load fluctuation is effectively suppressed during the valve switching process.