Table of Content

05 May 2021, Volume 54 Issue 5

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Power Supply and Demand Balance during the 14th Five-Year Plan Period under the Goal of Carbon Emission Peak and Carbon Neutrality

TAN Xiandong, LIU Jun, XU Zhicheng, YAO Li, JI Guoqiang, SHAN Baoguo

2021, 54(5):  1-6.  DOI: 10.11930/j.issn.1004-9649.202103047

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Under the carbon emission peak and carbon neutralization (bi-carbon) goal, the clean and low-carbon transition will be accelerated for the power system, which will have a profound impact on China’s power supply and demand situation during the 14th Five-Year Plan period. Based on an analysis of the major impact factors on the power supply and demand situation in China during the 14th Five-Year Plan period in the context of bi-carbon goal, a power demand forecasting model is built using the sector analysis method, and the power supply and demand balance is analyzed with the power system production simulation. It is concluded that during the 14th Five-Year Plan period, China's power demand will keep a fairly fast growth; the “double-peak” power demand in summer and winter seasons will bring pressures on power supply; and there is a certain amount of power shortage in winter in the regions with relatively high proportion of hydropower installed capacities. It is suggested that actions should be taken to ensure the balance of power supply and demand, such as strengthening the integrated planning of source-grid-load-storage, speeding up the improvement of demand response policies and mechanisms and building a reasonable number of gas-fired power plants and electrochemical energy storage stations according to the needs.

Blockchain-based Transaction Model of Distributed Photovoltaic Generation for Local Power Consumption

JIN Kaiyun, YANG Jianhua, CHEN Zheng, WANG Weizhou, HOU Bin, XUE Wenjing

2021, 54(5):  8-16.  DOI: 10.11930/j.issn.1004-9649.202004023

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At present, with the growing penetration rate of distributed photovoltaic generation in distribution networks, the application of blockchain is becoming more appealing to the dispatch of distributed energy transactions thanks to its decentralization feature and tamperproof mechanism. This is particularly beneficial for local or nearby energy consumptions, which can greatly boost the operation economy of the distribution networks. A blockchain-based photovoltaic transaction mechanism is proposed, and the benefit function of photovoltaic users and distributed photovoltaic aggregator is established. The Stackelberg game model is applied to determine the internal electricity price, and edge computing is used to work out an optimal power consumption plan. A reputation-based local consumption transaction mechanism is designed, in which penalties will be imposed on those users with low levels of local consumption. Therefore, users are encouraged to consume more photovoltaic power through time-shifting loads. The simulation of a distribution network shows that the local consumption of photovoltaic power has been improved and the users can benefit more under the transaction mechanism of blockchain.

Design of Power Data Trading Scheme Based on Blockchain

LIU Wei, SUN Yixin, CHEN Ruixin, CUI Weiping, WANG Zhimin

2021, 54(5):  17-27.  DOI: 10.11930/j.issn.1004-9649.202003224

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Power data trading is an important way that data can play valuable role. However, there exists considerable problems in the present data trading, such as centralized trading trust, unclear trading rules and difficult transaction supervision. This paper proposed power trading scheme based on blockchain. Firstly, upon the analysis of the characteristics of power data and the problems encountered in power data trading, the applicability of block chain to power data trading scenarios is expounded. Then, the basic characteristics and classification of block chain technology are described. Next, the design details for intelligent contract are put forward to ensure the secure and automatic execution of power data transaction. Finally, in combination with consensus mechanism, transaction account and other factors, the blockchain-based power data transaction is proposed including its basic framework and especially the analysis of key supporting technologies to ensure the operation security and smoothness of power data trading.

Energy Efficiency Optimization Based on Computing Offloading for Internet of Things in Power Systems

LIU Shidong, BU Xiande, YU Qiang, TIAN Feng

2021, 54(5):  28-34,45.  DOI: 10.11930/j.issn.1004-9649.202010054

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Based on the heterogeneous network architecture, in this paper by taking into account the mobile edge computing (MEC) architecture of Internet of things in power systems using three-tier computing, the energy consumption model and delay model are established respectively for each tier. Then the related tasks are offloaded from local computation in smart mobile device (SMD) to the MEC servers of small base station (SBS) and macro base station (MBS). To minimize the energy consumption due to the computing offloading, through variable substitution and decomposition, then by taking advantage of theoretical derivation based on the objective function monotonicity, the optimal solution is finally obtained. Simulation results show that, in comparison with other methods, the proposed scheme can achieve the effects of energy saving with less time delay.

Research on Cognitive Radio Non-orthogonal Multiple Access System in 5G Communications Oriented to Ubiquitous Power Internet of Things

SHE Rui, ZHANG Ningchi, WANG Yanru, GUO Dandan, MA Wenjie, LIU Hui, ZHANG Jie

2021, 54(5):  35-45.  DOI: 10.11930/j.issn.1004-9649.202010099

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With the continuous advancement of the construction of the power Internet of Things, the power distribution network has seen exponential growth of data volume. As a result, the traditional smart power communication network based on cognitive radio is no longer capable of meeting the high demand for spectrum resources by a large number of devices that are installed to collect power consumption data. This paper constructs a 5G network model for the power Internet of Things, which aims to use the non-orthogonal transmission characteristics of non-orthogonal multiple access (NOMA) technology to further improve the spectrum resource utilization of the limited power private network. To ensure the accuracy of spectrum detection, a multi-user cooperative sensing method is adopted. The closed expressions of spectrum access probability and throughput are derived; in order to further increase the accuracy of the classification results, an improved K-means algorithm is proposed. The alternate iterative algorithm is implemented to jointly optimize the detection time, node power and the number of user clusters such that the system throughput can be maximized eventually. The simulation results show that compared with the traditional orthogonal multiple access system, not only the spectrum utilization but also the accuracy of the sensing results are significantly improved.

Short-Term Load Forecasting Method Based on Multi-model Fusion Using CNN-LSTM-XGBoost Framework

ZHUANG Jiayi, YANG Guohua, ZHENG Haofeng, ZHANG Honghao

2021, 54(5):  46-55.  DOI: 10.11930/j.issn.1004-9649.202004026

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Accurate short-term load forecasting can provide effective guidance for unit scheduling, economic dispatch and power market operations. Concerning the low accuracy problem of load forecasting brought by the limited features of input data, a method based on multi-model fusion using CNN-LSTM-XGBoost framework is proposed. The Long Short-Term Memory network structure fused with local feature pre-extraction module is first established and then integrated with the XGBoost prediction model in parallel. Afterwards by using mean absolute percentage error-reciprocal weight algorithm to set initial model fusion weights and start searching for optimal weight, the optimal fusion model is built. From the prediction experiment of load data by virtual of the proposed method, it is discovered that the mean average percentage error and the root mean squared error of CNN-LSTM-XGBoost are 0.337% and 148.419 MW respectively, which indicates significant decrease of the error metrics compared with the outcome using single network model and multi-model structure. Therefore, it is verified that the method based on multi-model fusion using CNN-LSTM-XGBoost framework has faster training speed, higher accuracy and lower error of prediction.

Risk Assessment of Low-Voltage Interconnected Distribution Districts Considering Large-Scale Fast Charging Load

SHEN Peifeng, WANG Xuyan, ZHANG Haoliang, WEI Zhinong, XU Guangkai, SUN Guoqiang

2021, 54(5):  56-64.  DOI: 10.11930/j.issn.1004-9649.202002003

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A risk assessment method of distribution district is proposed based on large-scale electric vehicle(EV) fast charging load. Firstly, based on the "parking-charging" mode, and considering the different charging needs of residential areas and commercial areas, the EV fast charging load is simulated. Secondly, both the traditional decentralized access mode for fast charging load and the new access mode for low-voltage side interconnection in the distribution districts are given, and the control strategy for AC/DC converter and energy storage equipment is proposed, and the power model of distribution district interconnection is established. Finally, the risk indexes of distribution transformers, including heavy load, overload and load-shedding cost, are put forward, and a risk assessment system of distribution district is established. A demonstration project in Nanjing is taken as an example to analyze the operation risks of the distribution district under different topological structures and fast charging load scales, and the supporting effects of the energy storage system on the distribution district.

Stability Control Strategy for Wind-Thermal-Storage Hybrid System with Multi-Channel Delivery under DC Blocking

ZHAO Jixian, LI Fengting, YIN Chunya

2021, 54(5):  65-73.  DOI: 10.11930/j.issn.1004-9649.202004123

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DC blocking can cause transient overvoltage in the wind-thermal-storage system with multi-channel delivery. Firstly, the paper analyzes the impact of the surplus reactive power and the strength of the sending-end system on the transient overvoltage of the AC system after blocking. Secondly, the paper analyzes the mechanism of various adjustment methods to deal with blocking faults, which include: the flow transfer of the remaining delivery channels except the blocking line, the regulation of pumped storage and power-type energy storage. And the action sequence is determined according to the characteristics of each method, and a coordinated stability control measure is proposed that comprehensively considers multiple adjustment methods. Finally, the Hami power grid model is built based on DIgSILENT for simulation verification. The simulation results show that coordinated multi-means stability control measure can effectively alleviate the transient overvoltage problem, reduce the number of machine cutting, avoid the cascading disconnection risk of wind turbines, reduce the control cost, and improve the coordination recovery ability of the AC system.

Identification of Vulnerable Lines in Transmission Network for Cascading Failure Based on PageRank Algorithm

WEI Mingkui, ZHOU Quan, SONG Yuyan, WANG Yuhong, ZHOU Hong, CAI Shaorong, JIANG Li

2021, 54(5):  74-82.  DOI: 10.11930/j.issn.1004-9649.202004082

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In order to quickly and accurately identify the vulnerable lines that may trigger cascading failure in the power grid, a double-layer method for identifying vulnerable lines in the transmission network was proposed based on PageRank algorithm, which takes into account the cascading effect of faults. Firstly, the time series network model of transmission network is established based on the snapshot method with consideration of the evolution process of the cascading failure. Then, regarding the interaction of transmission lines and the immunity of lines to load fluctuation, a shallow identification model based on extended PageRank algorithm is constructed to calculate the vulnerability of transmission lines. Finally, the algorithm reconstruction is used to show the relationship between failures and the deep identification model of vulnerable lines is established to comprehensively analyze the vulnerability of lines. The change process of vulnerability in the cascading failure can be described at the same time. A case study was carried out on IEEE 39 bus system to demonstrate the rationality and accuracy of the suggested method.

Coordinative Frequency Control of Multi HVDC Links in Sending-End Power Grid Considering Over-Frequency Protection of Wind Power Generation

YOU Guangzeng, LI Huarui, LI Changgang, LIU Chao, QIAN Yingchun, LI Lingfang

2021, 54(5):  83-90,110.  DOI: 10.11930/j.issn.1004-9649.201903030

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A large number of high voltage direct current (HVDC) projects are under construction or have been put into operation in order to mitigate the reverse distribution between energy and loads in China. Focusing on the over-frequency scenarios of sending-end power systems causing by HVDC blocking, the coordinative control of multi high voltage direct current (HVDC) links considering over-frequency protection of wind power generators is studied in this paper to control system frequency. A coordinative control model is proposed to minimize the total HVDC modulation amount. The first-order difference is adopted to estimate the sensitivity of the maximum frequency deviation of the system against each controlled DC power, and the optimum coordinative frequency control strategies of multi HVDC links can be obtained. The proposed method is validated in a sending-end power grid model with high wind power penetration rate to show its effectiveness in designing the frequency control strategies of the sending-end power systems.

A Day-Ahead Two-Stage Distributed Optimal Scheduling Method for Active Distribution Network Based on ADMM

ZHANG Jin, HU Cungang, RUI Tao

2021, 54(5):  91-100.  DOI: 10.11930/j.issn.1004-9649.201904021

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With the access of a large number of controllable devices in the active distribution network, it is urgent to propose a new optimal dispatching method to adapt to the increasingly complex dispatching operation of the active distribution network. In order to solve this problem, this paper proposes a two-stage distributed optimal dispatching method considering the operation costs and network loss of the active distribution network. The first stage is the active power optimization stage, which considers the active power regulation function of controllable resources and takes the minimum operation cost of distribution network as the objective for economic optimal dispatch. The second stage is the reactive power optimization stage. On the basis of the first-stage dispatch, the reactive power regulation function of controllable resources is taken into account, and the reactive power optimization model is established. In order to alleviate the communication burden of the system, the centralized mathematical model of active and reactive power optimization is decomposed into several sub-models by using alternating direction method of multipliers, and the distributed solution of the model is realized by the interaction of expected information between adjacent regions. The simulation results show that the method can effectively reduce the operation cost and network loss of distribution network.

Generation Shedding Capacity Optimization of Sending-End Power Grids with Multi-DC Asynchronous Outfeeds Considering Frequency Stability

GOU Jing, LIU Fang, KUANG Li, SU Yunche, LI Ao, WEN Yunfeng

2021, 54(5):  101-110.  DOI: 10.11930/j.issn.1004-9649.202004133

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For the asynchronous interconnection system, the inertia of sending-end power grid drops sharply. Because of the severe high frequency problems caused by bipolar blocking of a HVDC transmission line, the traditional generation shedding strategy for dealing with the high frequency problems has some risks such as inaccurate shedding capacity (i.e. over- shedding or under-shedding) and lack of the rotational inertia after shedding. In order to solve the inadequacy of existing generation shedding schemes, we propose a generation shedding capacity optimization model for the sending-end grid with multi-DC asynchronous outfeeds considering the stability of system frequencies. The model comprehensively considers a variety of constraints, such as the frequency constraints, network power flow constraints, reserve constraints, and the constraints of generator-tripping capacity. By taking account of the adjustment performance and geographical distribution differences of various units in the sending-end grid, the TOPSIS method and the Superiority Chart are used to obtain the penalty factors of various units, and the optimal generation shedding scheme of the sending-end grid is determined for the bipolar blocking fault of a large-capacity HVDC transmission line with the goal to minimize the comprehensive cost of generator tripping. An improved IEEE RTS-79 test system is taken for case study, which has verified the effectiveness and the frequency adaptability of the proposed model.

Analysis of Spectrum Characteristics of Audible Noise Generated by AC Corona Discharge

HUANG Mingxiang, GUO Zhibin, PAN Lizhi, LI Xuebao

2021, 54(5):  111-120.  DOI: 10.11930/j.issn.1004-9649.202007078

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The audible noise (AN) generated by alternative current (AC) corona discharge is mainly composed of wide frequency band and pure tones at harmonics of power frequency. In order to understand the distinct spectrum characteristics of AN, the time-domain waveforms of AN occurring on the surface of conductor are measured using the time-domain test platform for AC corona-generated audible noise. Based on the analysis of its time and frequency characteristics, the AN is divided into three components: impulsive noise, ion-migration noise and background noise, and a wavelet-transform based noise extraction method is proposed to separate them. The impact mechanism of the AC voltage modulation and space ion-migration on conductor pure tones as well as the variation characteristics of pure tones are obtained. The result shows that under the effect of AC voltage modulation, the periodic pulse cluster noise and the reciprocating migration noise of space ions constitute the pure tones, while the ion migration has larger effects than the voltage modulation. The pure tones become prominent with the increase of voltage and share more proportion of the total sound pressure level. Finally, the motion characteristics of space ions in the process of corona discharge are presented to give a qualitative explanations for the spectrum characteristics of AN.

Fault Location of DC Transmission Lines Based on Backward Waves Considering Wave Speed Changes

WU Jianwei, SHAO Jianfeng

2021, 54(5):  121-128.  DOI: 10.11930/j.issn.1004-9649.202004148

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The fault location methods of UHVDC transmission lines can be divided into traveling-wave-based algorithm, fault-analysis-based algorithm and natural-frequency-based algorithm according to the principle. The traveling-wave-based algorithm is not reliable due to its wave head identification problem, and the choice of wave speed also affects the accuracy of fault location; The fault location accuracy of the fault-analysis-based algorithm is not high because of model accuracy; The natural-frequency-based algorithm has dead zone when the fault occurs at the end of the line. This paper presents a novel fault location algorithm, when the DC line fault occurs, the first backward-wave has not been reflected, and it is not affected by the frequency variation of the reflection coefficient, the backward-wave head is easy to identify, so the backward-wave is used for fault location in this paper. The identification of wave head uses the à trous algorithm with excellent singularity detection capability. In the case of inconsistent wave speeds caused by the use of different types of conductors on the DC line, the calculation is performed with different wave speeds to improve the range accuracy further. Compared with the existing fault location algorithm, the reliability of the wave head identification of this algorithm is improved, and since the variation of the wave speed is taken into consideration, the ranging accuracy is improved further when different types of wires are used in the DC line.

Simulation of Metal Particles with Different Arrangements in Uniform Electric Field

ZHU Jie, WU Jiale, SONG Xupeng, BIAN Xingming

2021, 54(5):  129-138.  DOI: 10.11930/j.issn.1004-9649.201911040

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Many studies at macro level have proved that the surface states of conductors can affect the corona performance greatly, but their effects on the electric field pattern are not studied sufficiently at microscopic level. The influence of the different arrangement of metal particles on the plates applied voltage was simulated in the uniform electric field, because the uniform electric field allowed us to pay more attention to the law of mutual influence of the particles. When the metal particles were arranged in a line, as the number increased, the maximum electric field strength and the maximum surface charge density were weakened, which tended to a limit value. The formula was fitted according to the quantity-electric field strength curve. When three balls were arranged in a line, the weakening effect was the strongest when the middle ball was located in the middle of the other balls, and the shorter the distance between the two balls was, the more obvious the effect was. When the metal balls were arranged in regular polygons, the more the balls were and the closer their distance was, the more obvious the weakening effects. It was also found that the field strength reached the highest when the metal ball was close to but not in contact with the plate. The simulation results show that the less number of metal balls may not lead to a better electric field distribution, which provides a theoretical basis for better optimizing the surface state of conductors and removing the defects.

Optimization of Magnetic Coupling Mechanism for Wireless Power Supply of High-Voltage Transmission Line On-Line Monitoring Equipment

HE Jiyong, ZHOU Haikuo, ZHU Renxun

2021, 54(5):  139-147,165.  DOI: 10.11930/j.issn.1004-9649.202002133

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Real-time and accurate on-line monitoring of high-voltage transmission lines is an effective means to ensure the stable operation of power grids. Magnetic coupling resonance wireless power supply is a feasible solution to the power supply problem of on-line monitoring equipment. However, the conventional magnetic coupling resonance system has a poor overall performance due to its weak coupling and the sensitiveness of its transmission efficiency to the change of the transmission distance. The mutual inductance influences of coupling coils on the transmission efficiency are analyzed through magnetic coupling resonance circuit models, and a joint optimization scheme considering the cross influence of coils and cores is proposed to improve the transmission performance. Simulation and experiment have verified the improvement of transmission efficiency under the change of coaxial spacing, horizontal and angular offsets. This study can provide an efficient insight into the optimization of magnetic coupling system.

Primary Current Test Method for Transformer Protection Based on Transient Load

SHI Jiyin

2021, 54(5):  148-155.  DOI: 10.11930/j.issn.1004-9649.202007025

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When test load is insufficient, the current transformer (TA) secondary circuit test by primary current cannot be completed, which often results in the failure of new transformer protection to be put into normal operation. In order to solve this problem, a method for testing TA secondary circuit by using transient current such as motor starting current or transformer magnetizing inrush current is presented. The double-side current relationship of the transformer is analyzed with transient load flowing, and the current is reconstructed according to different wiring groups so that the currents on both sides are proportional. The signal correlation function is introduced to analyze and calculate the current waveform, and the phase angle difference and transformation ratio of TA on both sides of the transformer relative to the reference bay are obtained, thereby determining the correctness of TA secondary circuit. The engineering test results of the proposed method are consistent with that of traditional steady-state load test method, which proves its feasibility and correctness.

Fuzzy Comprehensive Evaluation of Aging State of Silicone Rubber Sheds of Composite Insulators

WANG Sihua, CHEN Long, WANG Junjun, ZHAO Lei

2021, 54(5):  156-165.  DOI: 10.11930/j.issn.1004-9649.202010080

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Aiming at the aging problem of silicone rubber composite insulators with long-term outdoor operation, a composite insulator condition assessment method is proposed based on fuzzy comprehensive evaluation. From the perspective of silicone rubber shed materials of composite insulators, four first-level indicators, including mechanical performance index, hydrophobic index and electrical performance index, as well as 12 second-level indexes are established. The membership of each index is obtained by constructing the membership function of the evaluation indexes, and the weight of each index is given with the combined weight method of improved analytic hierarchy process (AHP) and entropy weight method. At last, the linear weighting methods is used to calculate the grade status of composite insulators. Case study shows that the proposed model can accurately and efficiently discriminate the state of composite insulators, which can provide a basis for the condition maintenance of composite insulators.

Ampacity Optimization for Cluster Power Cables Laid in Ducts of Narrow Channel

MA Aiqing, QIN Bo, ZHANG Huafu

2021, 54(5):  166-173.  DOI: 10.11930/j.issn.1004-9649.202003131

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In the construction of underground power cables, it is often unavoidable to pass through areas with narrow roads or dense underground pipe networks.In order to keep a safe horizontal distance, it is common to arrange the cluster cables in a narrow underground channel, which however will lead to the ampacity decrease of underground power cables in cluster. Based on the IEC 60287, an unequal load matrix optimization method is proposed for cluster cables in narrow channels by combining the heat transfer theory with matrix theory. To verify the accuracy of the optimization method, a finite element temperature model is established for several typical cable arrangement schemes in narrow underground channels, and the temperature field simulation is performed.Finally, a suitable scheme for narrow-arranged cables is designed after comparing the ampacity of actual underground power cables before and after the underground channel is narrowed. The results show that the proposed scheme can improve the utilization rate of the power cable, and reduce the influence of the narrowed channel on ampacity of power cables. The adopted unequal load flow method for the narrow channels can improve the cable transmission capacity, and it can increase by 6.53% at maximum with the increase of the number of cables loops.

Dynamic Early Warning Method for Power Grid Information System Based on Fuzzy Analytic Hierarchy Process

GUO Jing, ZHANG Jie, DING Xi, SHEN Lei

2021, 54(5):  174-178,185.  DOI: 10.11930/j.issn.1004-9649.202002034

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Power grid information system is very important for supporting the stable and reliable operation of power grid enterprises. Real time monitoring, evaluation of the operation status of information system and timely early warning have always been the focus for concerning in the industry. When the conventional early warning methods are used to deal with the equipment aging or updating, business volume fluctuation, and equipment addition, false alarm and missing report often occur. The daily operation curve is fitted scientifically and updated and compared in time. The weight of each equipment index is calculated based on the fuzzy analytic hierarchy process (FAHP). The equipment early warning level is generated by combining the abnormal duration and incremental weight. Finally, the overall warning status of the information system is obtained by synthetizing the equipment warning level and quantity. The algorithm is verified by a prototype system, and the results show that the method can sense the whole running state of the equipment and the system in real time, and quickly judge the reliability and identify the fault. This method can achieve accurate and timely dynamic early warning, and improve the operation reliability of information system, and has important research significance and practical value.

E-FCNN Based Electric Power Inspection Image Enhancement

BAI Wanrong, ZHANG Xun, ZHU Xiaoqin, LIU Jixiang, CHENG Qiyu, ZHAO Yan, SHAO Jie

2021, 54(5):  179-185.  DOI: 10.11930/j.issn.1004-9649.202004144

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For UAV patrol of transmission lines and robot inspection of unattended substations, low image resolution is one of the main problems due to long shooting distance or machine shaking. In order to solve this problem, we propose an edge-aware feedback convolutional neural network (E-FCNN), which not only adds Resnet blocks and feedback mechanism to the conventional super-resolution network to strengthen the ability of feature extraction, but also adds texture information to the edge-aware branch to enhance the image detail. Extensive experiments show that the proposed algorithm is superior to other existing algorithms, both in subjective visual quality and objective evaluation indexes such as peak signal-to-noise ratio. Practically, the proposed algorithm can improve the accuracy of insulator detection in UAV transmission line inspection.

Frequency Stability Control Strategy for Large-scale Grid Connections with DFIG Units

YANG Lei, WANG Zhichao, ZHOU Xin, LI Shengnan, HE Peng, XIANG Chuan, ZHANG Jie, WANG Delin

2021, 54(5):  186-194.  DOI: 10.11930/j.issn.1004-9649.202003163

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The penetration rate of wind power in the power grid has been increasing year by year. A lot of contributions have been made to optimize the power supply structure, energy conservation and emission reduction, however, due to the natural fluctuation and uncertainty of wind speed, grid integration with large-scale wind power is bound to impact the frequency stability of the power grid. With regard to this problem, the doubly-fed induction generator (DFIG) control system was studied in this paper and then the primary frequency modulation control strategy following large-scale DFIG connection was established. On the basis of the existing droop control and virtual inertia control strategy, the droop control part is implemented by virtue of variable coefficient according to the input wind speed and the frequency fluctuation of grid side, as to improve the droop control characteristics. Additionally, the operating conditions of DFIG are classified, and the load reduction coefficient is used to reduce the curtailment of wind while the DFIG is running at limited power level. The effectiveness of the proposed primary frequency modulation control strategy is verified by means of the simulation of an actual power grid model with large-scale wind power grid connection.

Operation Control Technology and Application of All-clean Energy Power Supply in Provincial Power Grid

ZHU Gang, LI Yanhe, ZHANG Zhen, XU Yourui

2021, 54(5):  195-205.  DOI: 10.11930/j.issn.1004-9649.202006306

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Electricity plays an important role in energy transformation. The future energy transformation will show the trend of clean, low carbon and electrification. This paper mainly introduces the operation control technology and application of all-clean energy supply in provincial power grid. Firstly, this paper introduces the technical problems faced by the power grid to achieve all-clean energy supply; secondly, the power and electricity balance equation of the power grid under the condition of all-clean energy supply is analyzed; thirdly, based on the output constraints of the power grid and Hydropower units, dispatching generation scheduling optimization function is analyzed. Finally, taking the clean energy power supply successfully realized in Qinghai Province in recent three years as an example, this paper analyzes the feasibility and main implementation process of the clean energy in the provincial power grid from the perspective of engineering practice, and discusses the innovative connotation of the three clean energy power supply in technology and transaction mode. The practice and exploration of all-clean energy power supply can provide practical experience for improving the multi-energy complementary coordination control and new energy absorption capacity of power grid, promoting the development of clean energy, and providing meaningful reference for the power grid to carry the new energy revolution.

Technical Difficulties and Related Control Strategies on In-Depth Peak Regulation for Supercritical Circulating Fluidized Bed Boiler

WANG Pengcheng, DENG Boyu, CAI Jin, WANG Ke, KONG Hao, LI Lifeng, ZHANG Man, YANG Hairui

2021, 54(5):  206-212.  DOI: 10.11930/j.issn.1004-9649.202011107

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In order to further improve the stability and economy of the operation of supercritical circulating fluidized bed (CFB) boiler units in the process of deep peak regulation, this paper takes the 350 MW supercritical CFB boiler of a power plant as the research object and proposes the corresponding control strategies and technical measures based on the analysis of the series of problems in deep peak regulation, such as steady combustion and fluidization, hydrodynamic safety, steam feed pump control, emission control, and so on. The practical operation results show that by adopting these control strategies, long-term steady operation of the boiler can be achieved. The research results can provide helpful reference for the deep peak regulation of supercritical CFB boilers of the same type and even the ultra-supercritical CFB boilers.

Performance Analysis and Application Research of Low-Pressure Cylinder Zero Output Technology on 320 MW Unit

LIU Shuangbai, ZHANG Jing, WU Xin, HU Yuou

2021, 54(5):  213-220.  DOI: 10.11930/j.issn.1004-9649.202101053

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Using low-pressure cylinder zero output technology can effectively improve the heating capacity and peak regulation capacity of the generation unit. In this paper, taking a 320 MW heating unit for example, firstly, Ebsilon software is used to calculate and analyze the heating performance of low-pressure cylinder zero output. The results show that the application of low-pressure cylinder zero output technology increased the maximum heating extraction steam flow of the unit by 97%, and reduced the net coal consumption by 61 g/(kW·h) at 250 MW heating load. Then, the test study on the heating capacity of low-pressure cylinder zero output mode of the unit was carried out. Field measurements show that the maximum heating load of the unit can reach as much as 476 MW, while the minimum electric load can be reduced to 79.5 MW. At last, based on the operation data of the heating season of previous year, the economic performance of low-pressure cylinder zero output mode is analyzed. The results show that using this heating mode can save 5581 t of standard coal equivalent.