01 February 2020, Volume 41 Issue 2

    

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  Multi-Objective Optimization Model of Gas-Electricity Interconnected Virtual Power Plant Considering Demand Response

  ZHANG Junliu,FAN Wei, TAN Zhongfu, JU Liwei, DE Gejirifu,YANG Shenbo, SUN Jingxia

  Electric Power Construction. 2020, 41(2): 1-10. https://doi.org/10.3969/j.issn.1000-7229.2020.02.001

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  With the gradual increase of distributed energy permeability, virtual power plant technology has gradually become a key technology to solve the large-scale development of renewable energy. This paper focuses on multi-objective optimization of gas-electricity interconnected virtual power plant. Firstly, this paper integrates wind power, photovoltaic power generation, convention gas turbine, power-to-gas, gas storage tank, etc. into virtual power plants. At the same time, it links the public power grid and natural gas network. The load side includes electricity load, hydrogen fuel-cell vehicle load and natural gas load. The demand response is introduced to adjust the terminal load. Then, combined with power balance and other constraints, the multi-objective model of the gas-electricity interconnected virtual power plant is constructed with the optimization objectives of economic benefit of operation, peak regulation, and carbon dioxide emission. The multi-objective optimization model is transformed into a single-objective model by weighing each objective function. Finally, in order to verify the validity and feasibility of the established model, a virtual power plant in a certain area is selected as an example to compare the operation results of four scenarios. The results show that: 1) The multi-objective optimization model of the gas-electricity interconnected virtual power plant can achieve the optimal comprehensive benefits of economy, stability and environmental protection； 2) Power-to-gas and demand response have the synergistic effect of peak regulation, which improves the stability of the system； 3) Power-to-gas increases the amount of grid-connected clean energy and reduces carbon emissions； 4) The connection between the virtual power plant and the public network enables flexible energy interaction, and the rational purchase and sale of electricity strategies can optimize operation.
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  Typical Application Scenarios and Project Review of Energy Blockchain

  ZHOU Hongyi1、，QIAN Weihang2、，BAI Jingjing1、，WEI Zhinong2、，SUN Guoqiang2、，ZANG Haixiang

  Electric Power Construction. 2020, 41(2): 11-20. https://doi.org/10.3969/j.issn.1000-7229.2020.02.002

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  As an emerging infrastructure and distributed computing paradigm， blockchain is characterized by de-centralization， openness， transparency， immutability and traceability， which is consistent with the characteristics of openness， equivalence， interconnection and sharing of energy internet and can promote the further development of energy internet. The research status of energy blockchain is systematically analyzed and divided into six typical application scenarios: distributed energy trading， blocking management and auxiliary services， carbon emission right certification and green certificate trading， demand response， data management and information security， and release and investment of digital tokens. On this basis， the typical energy blockchain projects corresponding to each application scenario are summarized and reviewed. Finally， the development prospect of energy blockchain in China is analyzed and some suggestions are put forward.
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  Analysis on Transmission Congestion Mechanism of Cross-Region Renewable Energy Integration in Receiving-End Power Grid

  GUO Li，WU Chen，CHEN Li，CONG Xiaohan，MIAO Xiyun，WANG Beibei

  Electric Power Construction. 2020, 41(2): 21-29. https://doi.org/10.3969/j.issn.1000-7229.2020.02.003

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  With large amount of outside power injection and renewable energy grid-connection， the regional transmission congestion problem caused by unbalanced distribution of power supply and load begins to appear in the receiving-end grid. Because of the difference of power sources and loads peculiarity， peak regulation demand between sending-end grid and receiving-end grid， the interregional peak adjustment will cause the transmission section obstruction with insufficient margin. In view of an eastern developed province receiving-end grids transmission congestion problem， this paper analyzes the effects of high proportion of outside power and local renewable energy on peak load regulation. Then a congestion mechanism analysis model is established. In the example， two different congestion scenarios are simulated under the two reserve power supply modes of total reserve and average reserve， and a continuous time-sequence simulation of the provinces planning state in 2025 is carried out with GOPT simulation software to further demonstrate the blocking phenomenon. Through the mechanism analysis of this paper， some suggestions are put forward to alleviate the regional transmission congestion， such as differentiated allocation of peak load regulation power and differentiated allocation of reserve.
  
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  Research on Market Mechanism of Frequency-Regulation Auxiliary Service Considering Demand-Side Resources

  JING Jiangping，YANG Zijun，LU Xiao，SHEN Yunwei，WANG Zijian，SONG Jie，SHAO Junjun，LI Yang

  Electric Power Construction. 2020, 41(2): 30-39. https://doi.org/10.3969/j.issn.1000-7229.2020.02.004

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  With the development of smart grids， it has become possible for demand-side resources to participate in frequency regulation. How to quantify the contribution of traditional automatic generation control (AGC) units and demand-side resources to system frequency regulation， and encourage demand-side resources to participate in frequency regulation market is a problem that needs to be solved urgently. On the basis of considering the different frequency regulation performance of the traditional AGC unit and the demand-side resources and the replacement effect of the demand-side resources on the traditional AGC unit， a clearing and compensation model of the combined market of power and frequency regulation is established. Simulation results of the IEEE 14-node system show that the model can greatly improve the bidding probability and benefit of the demand-side resources in the market， and reduce the systems demand for frequency regulation capacity and purchase cost.
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  Cyber Security Simulation Based on Real-Time Simulation Platform of Cyber Physical Power System

  SUN Pingyuan， LIU Keyan， QI Donglian

  Electric Power Construction. 2020, 41(2): 40-46. https://doi.org/10.3969/j.issn.1000-7229.2020.02.005

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   Modern power systems have gradually developed into cyber physical power systems that deeply integrate information flow and energy flow. Traditional simulation methods that only operate on physical systems cannot guarantee the accuracy of the simulation analysis. From the perspective of simulation analysis， on the basis of a comparative analysis of existing simulation methods， this paper makes improvements in simulation tools and coordination modes， and further adds a man-in-the-middle link to build a new CPPS real-time co-simulation platform considering cyber-attacks. Finally， the impact of cyber-attacks on the power physical system is studied with the example of load control business on this platform， and the deep coupling relationship between cyber system and physical system of CPPS is analyzed in detail. Simulation results validate the effectiveness and real-time performance of the proposed platform.
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  Load Probability Modeling and Scenario Generation for Electric Vehicle Charging Station Considering Time Correlation

  JIANG Hao， LIN Shunjiang， LU Yi， HE Sen

  Electric Power Construction. 2020, 41(2): 47-57. https://doi.org/10.3969/j.issn.1000-7229.2020.02.006

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  Due to the influence of random factors such as electric vehicle (EV) owners travel behaviors and traffic condition， the load of EV charging station has strong randomness. Establishing an appropriate probability model to describe the stochastic load of EV charging station is of great significance to the secure operation analysis of distribution network. Taking the load of each period in daily load curve of EV charging station as a random variable， according to historical data， the probability distribution of each single-period load is established with versatile distribution which has the highest fitting accuracy. Because of the continuity of EVs charging behaviors， the charging stations loads in adjacent periods are correlated. Firstly， 96 periods of a day are divided into several continual period sets according to the correlation analysis between loads of different periods. In each set of continual periods， the correlation between the loads of several adjacent periods is relatively large. Then， the joint probability distribution of the loads of several adjacent periods in each set of continual periods is established by using Pair-copula method with D-vine structure. Furthermore， the Pair-copula joint probability distribution model is used to sample and generate load scenarios considering time correlation for all continual period sets in a day. The trend and size of fluctuation are used to represent the fluctuation indices of the generated load scenarios to measure the rationality. Finally， taking the actual historical data of an EV charging station in Shenzhen  as an example， the effectiveness of the proposed method is verified.
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  Numerical Calculation Method for Energy Flow of Combined Electricity and Heat Networks

  JING Jiangping， WU Yi， HU Wei， LU Xiao， WANG Wenxue， WEI Zhinong， SUN Guoqiang

  Electric Power Construction. 2020, 41(2): 58-66. https://doi.org/10.3969/j.issn.1000-7229.2020.02.007

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  Existing energy flow calculation methods for heat network obtain the state variables by solving the nonlinear equations， and then the network heat loss can be obtained， and the network loss is usually not known before the energy flow calculation. In this paper， the total loss formula of the radiant heating network is strictly derived. The total heating loss can be obtained before the energy flow calculation， and then the mass flow rate and the node temperature of each pipeline can be obtained. The energy flow results can be obtained through the electricity-heat coupling component. The simulation results of a 23-node thermal network and a 33-node power distribution network show that the proposed energy flow calculation model of integrated energy system can achieve the higher accuracy while obtaining faster calculation speed.
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  Optimal Scheduling and Operating of Active Distribution Network Considering Comprehensive Carrying Capacity

  DAI Songling， WANG Xi， LIU Fang， LEI Yunkai， OUYANG Xuetong， WEN Fengrui， LI Huaqiang

  Electric Power Construction. 2020, 41(2): 67-75. https://doi.org/10.3969/j.issn.1000-7229.2020.02.008

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  With the increasing penetration of wind and solar power， the uncertainties bring great challenges to the optimal scheduling of active distribution network. In order to improve the ability of active distribution network to deal with uncertain disturbances， an optimal scheduling method is proposed to enhance the comprehensive carrying capacity of active distribution network. Firstly， comprehensive carrying capacity is proposed from the aspects of resource adequacy and operation safety of active distribution network. Then， based on the coordinated scheduling of various active management resources， an optimal scheduling model of active distribution network considering comprehensive carrying capacity is constructed. Secondly， the graph theory “broken circle” method is introduced to improve the encoding strategy of the grid， and the hybrid encoding particle swarm optimization algorithm is used to solve the model. Finally， an improved IEEE 33-node system is taken as an example to verify the validity of the model.
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  Research on Steady-State Equivalent Model of “Sen” Transformer (ST)

  CHEN Kailong，SONG Jieying，LIU Xin，ZHANG Jianpo

  Electric Power Construction. 2020, 41(2): 76-84. https://doi.org/10.3969/j.issn.1000-7229.2020.02.009

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  “Sen” Transformer (ST) is the most powerful electromagnetic unified power flow controller. At present， the research on ST mainly focuses on circuit topology and feasible control schemes， and there is little research on ST modeling. There is no equivalent model of ST for theoretical and systematic analysis. Based on the mutual inductance model of multi-winding transformer， the 6-port mathematical model of ST is established. In addition， the three-sequence voltage equation of ST is derived. Then the three sequence equivalent circuits with excitation characteristic are obtained. And each sequence short-circuit impedance can be calculated from each transformation ratio and winding resistance and leakage reactance. The simulation model of ST is built in PSCAD software， and the simulations of steady-state current and short-circuit current are carried out. Simulation results and the equivalent model are in good agreement， and the maximum relative error of line current is less than 0.15%， which verifies the effectiveness of the ST equivalent model.
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  Sub-Synchronous Oscillation Characteristics of Direct-Drive PMSG under All Operation Regions when Wind Farms Connected to Weak AC System

  GAO Benfeng， CUI Yichan， SHAO Bingbing， LIU Yi， ZHAO Shuqiang

  Electric Power Construction. 2020, 41(2): 85-93. https://doi.org/10.3969/j.issn.1000-7229.2020.02.010

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  In view of the sub-synchronous oscillation (SSO) characteristics of direct-drive wind farms incorporating weak AC grids， the existing research mostly analyzes the situation that the direct-drive permanent magnet synchronous generator (D-PMSG) in the maximum power tracking operation area without considering the constant output power and other operation areas. In this paper， a small signal model of D-PMSG connected into weak AC power network is established， and then the eigenvalue method is used to analyze the sub-synchronous oscillation characteristics under different wind speeds and output power in the full operating region. A time-domain simulation model of a direct-drive wind farm connected to a weak AC grid was established in PSCAD/EMTDC to verify the correctness of the conclusions. The results show that， in the maximum power tracking operation area， when the wind speed increases and the output power is the maximum， the damping increases； In the running area of constant output power， when the wind speed increases， the damping is basically unchanged； In the whole operation area， at the same wind speed， the lower the output power， the smaller the damping and the worse the system stability； In actual operation， if the power grid limits the output power of wind farm， in order to reduce the power output of wind farm， more suitable measure is cutting off some D-PMSGs， thus the system has greater damping when sub-synchronous oscillation occurs.
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  Analysis Method for Operation Error of Smart Meter Considering Ill-Conditioned Model

  CHEN Hao， QIAO Yanan， LIU Jing， LI Yang， YANG Ting

  Electric Power Construction. 2020, 41(2): 94-100. https://doi.org/10.3969/j.issn.1000-7229.2020.02.011

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  Error verification of the smart meter in low-voltage station areas is of great significance for maintaining the state of meters and saving operating costs. The error analysis method based on big data only relies on electricity measurement data in the advanced metering system， which is of high coverage， fast and convenient， and avoids the heavy work of on-site verification， thereby saving a lot of manpower and material resources. However， because of the ill-condition of the model， the accuracy of the measurement data cannot be guaranteed. Aiming at this problem， this paper uses data preprocessing and regularization algorithm to effectively solve the ill-posed state of verification model of the smart meter error. Finally， taking the electricity data of an actual low-voltage station area as an example， analysis result shows that the method proposed in this paper can effectively improve the calculation accuracy of operation error verification algorithm of the smart meters， and provide scientific reference for the maintenance work of on-site meter verification.
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  Research on Charging and Discharging Control Strategy of Hybrid Battery in Household Photovoltaic Power Station

  CHEN Jingwen， ZHANG Wenqian， LI Xia

  Electric Power Construction. 2020, 41(2): 101-1078. https://doi.org/10.3969/j.issn.1000-7229.2020.02.012

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   In order to solve the problem that the intermittent photovoltaic power generation and the diversity of electricity load cause frequent fluctuations of bus voltage of the household photovoltaic power station， a kind of photovoltaic power station structure containing hybrid battery energy storage is designed. For PV bus voltage stability， this paper proposes a power management strategy for the hybrid energy storage system by combining a low pass filter with fuzzy control. First of all， the fluctuations in DC bus voltage are divided into high frequency and low frequency components. Then the low frequency component is processed by energy type battery， while high frequency component is processed by power battery， to realize the stability of bus voltage in power station. At last， on the basis of bus voltage stability， two components of battery energy are redistributed to effectively prolong the service life of the energy type battery. In order to verify the rationality of the strategy， a simulation model is established. The simulation results show that the strategy designed in this paper may suppress the voltage fluctuation of the photovoltaic DC bus， and the voltage fluctuation of the bus is controlled within 1.25%.
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  Event-Triggered Load Frequency Model Predictive Output Feedback Control of Interconnected Grid

  LIU Dongming， YANG Yang， WANG Junbo， SHI Haitao， MA Hongjun， ZHANG Hong

  Electric Power Construction. 2020, 41(2): 108-117. https://doi.org/10.3969/j.issn.1000-7229.2020.02.013

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  The open communication environment inevitably leads to the generation of communication delay in load frequency control. This paper offers an event-triggered model predictive output feedback control scheme for multi-region load frequency control systems. Model predictive controller exchanges predictive input sequences through a delayed communication network to construct a Luenberger-type observer to provide state estimates for transmission to the local controller. In addition， event trigger conditions are developed by comparing the deviation between the actual state observations and the estimated values used in the model output feedback controller， extending the maximum allowable time interval， thereby reducing the utilization of communication resources. Finally， the simulation study of the four-area load frequency control system shows that the proposed method can improve the control performance of the system and reduce the number of network information transmission in non-ideal communication networks with time-varying delay.
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  Multi-Objective Optimal Scheduling Based on Fuzzy Membership for Electric Bus Charging Station

  QIAN Kejun， QIN Meng， SONG Yuanjun， ZHOU Zhenkai， LIU Yi， XIE Ying， CHEN Lijuan

  Electric Power Construction. 2020, 41(2): 118-124. https://doi.org/10.3969/j.issn.1000-7229.2020.02.014

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  In order to consider both economic benefits of the charging station and the safety of the distribution network， a multi-objective optimized scheduling model for electric buses participating in vehicle to grid (V2G) is established. This model takes into account not only the travelling need of electric buses， but also the bus-pile connection status in the charging station. Due to the low correlation among objectives， the fuzzy membership function is used to fuzzy up objectives. Then the multi-objective optimization problem is transformed into single-objective problem to maximize satisfaction on the basis of the maximum and minimum theory. Finally， single-objective strategy and the multi-objective strategy are compared under disordered charging mode and V2G charging mode， which verifies the economy and effectiveness of the multi-objective model of charging station participating in V2G.
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  Multi-Objective Power Quality Optimization Control of Novel Electric Spring on the Basis of AFSA

  DENG Yujun， ZHOU Jianping， MAO Dajun， HU Chengyi， YE Jianqiao， FANG Le

  Electric Power Construction. 2020, 41(2): 125-132. https://doi.org/10.3969/j.issn.1000-7229.2020.02.015

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  Electric spring (ES)， as a new technology for demand-side response， has become a hot issue in the power industry. In order to fully exploit the potential of ES， this paper proposes a multi-objective power quality optimization control strategy for novel ES on the basis of AFSA to optimize the voltage of critical load (CL)， system frequency and power factor of non-critical load (NCL). Firstly， a new back-to-back electric spring (B2B-ES) topology is proposed to realize bidirectional flow of power on the load side. Secondly， an improved artificial fish swarm algorithm (AFSA) is proposed， which is based on the weighted average visual range and adaptive crowding factor. The multi-objective optimization function is designed to extract the local value of the load-side NCL voltage and system frequency to optimize the ES control signal， so as to compensate the power quality of the system online by adjusting the power of the electric spring. Finally， the simulation proves that the proposed optimization control can overcome the shortcomings of single-objective and poor real-time performance of the existing ES control method， and realize real-time optimization of multi-objective power quality control.