01 July 2019, Volume 40 Issue 7

    

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  Energy Transaction Mode in the Regional Multi-microgrid Connected Distribution Network Considering Wind Power Accommodation

  TAN Siwei， LIU Yang， XU Lixiong， WANG Hanlin

  Electric Power Construction. 2019, 40(7): 1-9. https://doi.org/10.3969/j.issn.1000-7229.2019.07.001

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  As the number of microgrids continues to increase， the frequent energy interaction between the microgrid and the distribution network will have an adverse impact on the operation of the distribution network. In addition， the gradual increase in penetration rate of wind power leads to a large amount of wind power entering the distribution network， which also imposes a serious burden on the operation of the distribution network. In order to reduce the unnecessary energy interaction between the microgrid and the distribution network， promote the local consumption of wind power， this paper constructs an energy transaction mode for multi-microgrid and distribution network that considers wind power uncertainty. The optimization goal of this mode is to maximize the revenue of the system operation entity and minimize the total cost of power consumption of the multi-microgrid. This mode integrates the load and wind power output in the area through operation entity， and divides the internal peak-to-valley time of the system to improve the utilization of wind power. In order to enhance the ability to cope with the uncertainty of wind power， the transaction mode uses the load transfer rate to describe the user response of TOU prices and establish a model for the TOU price of regional multi-microgrid systems considering wind power uncertainty. Finally， the multi-objective optimization problem in the model is solved by the NSGA-II algorithm combined with the Monte Carlo method. The example proves that the proposed transaction mode is beneficial to reduce the cost of electricity used in microgrids， improve the overall benefits of the multi-microgrid， and realize the friendly interaction between the multi-microgrid system and the distribution network.
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  Distributed Energy Trading System Based on Internet of Vehicles Platform

  ZHANG Yuanxing，JIANG Bing，DIAO Xiaohong，LI Taoyong，ZHANG Jing，LIU Yongxiang，XU Qingqiang

  Electric Power Construction. 2019, 40(7): 10-17. https://doi.org/10.3969/j.issn.1000-7229.2019.07.002

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  Smart vehicle networking platform is the product of the integration of power， transportation and internet in the new era. It is also an important part of the ubiquitous power internet of things. It shows great potential in the context of energy internet. By effectively utilizing the resources of vehicle networking platform to promote distributed energy consumption， we can provide a viable profit model for vehicle networking platform and promote the transformation of Chinas energy system. Firstly， this paper analyses the distributed energy trading architecture in the vehicle networking platform. On this basis， a distributed energy trading system based on block chain intelligent contract is proposed for P2P transaction of vehicle networking platform. Finally， the operation mode of vehicle networking platform under distributed energy trading mode is designed， which mainly includes producer-consumer mode， integrated energy service mode and digital connection mode. The conclusions of this paper can provide a reference for the construction of distributed energy trading system on vehicle networking platform.
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  Sequential Operation Simulation Technology for Renewable Energy Accommodation Considering Multi-Energy Complementarity

  CHEN Qichao，LI Hui，WANG Shuai，SHI Rui，ZHANG Ning，QI Qingru，WANG Fei

  Electric Power Construction. 2019, 40(7): 18-25. https://doi.org/10.3969/j.issn.1000-7229.2019.07.003

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  For the accurate assessment of the multi-energy complementary benefits of renewable energy such as wind， photovoltaic and hydro power， a power system sequential operation simulation model is proposed considering the multiple energy coordination and complementary of hydro/coal/wind/photovoltaic power. The simulation model is based on the mid- and long-term random output sequential simulation of numerous wind farms and solar photovoltaic power plants， and the short-term optimization method of hydropower considering the influence of storage capacity on the basis of the results of medium and long-term hydropower optimization. The simulation calculation of production operation is carried out by taking the western China power grid as a case， which is with high proportion of renewable energy and difficulties in accommodation. The results show that the power structure and load characteristics of the northwest and southwest regions are different， and the complementary advantages of the trans-region are obvious. The construction of interconnection transmission channels between northwest and southwest regions can realize multi-energy complementarity， effectively improve the utilization efficiency of renewable energy transmission lines， and enhance the renewable energy accommodation capacity in the western region.
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  Interval Prediction of Photovoltaic Power Applying Improved Weight Optimization Model

  WEI Shanyang， LI Jinghua， HUANG Qian

  Electric Power Construction. 2019, 40(7): 26-33. https://doi.org/10.3969/j.issn.1000-7229.2019.07.004

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  Interval prediction method can reflect the possible range of photovoltaic power， and provide more abundant forecasting information than point prediction method. An interval prediction model based on Radial Basis Function （RBF） neural network is proposed to directly output the prediction interval of photovoltaic power. In order to optimize the performance of the output interval of the model and avoid the problem of choosing penalty coefficient， an improved prediction interval optimization model considering the bias information of the interval prediction is constructed and solved by particle swarm optimization （PSO） algorithm to obtain the optimal RBF neural network output weights， and improve the reliability and accuracy of the prediction interval. By comparing the prediction results of the traditional interval optimization model and the improved interval optimization model， it is found that the improved interval optimization model can obtain more accurate prediction interval of photovoltaic power， and can provide more accurate auxiliary information for dispatching decision-making.
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  An Evaluation Method on the Flexibility of Regulation Methods in Distribution Network Considering Typical Scene Sets

  CHEN Yaoyu， JIANG Quanyuan，ZHOU Ziqiang，WANG Chaoliang，XU Feng

  Electric Power Construction. 2019, 40(7): 34-40. https://doi.org/10.3969/j.issn.1000-7229.2019.07.005

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  With the increase of distributed energy source and highly uncertain load in space-time distribution， the distribution network needs to be more flexible. In the planning of power distribution network upgrading and reconstruction， this paper proposes a matrix-based flexibility evaluation method from two dimensions of coping with multiple scenarios and meeting multiple objectives for different optional regulation methods. In the dimension of running scene set， K-medoids clustering algorithm is used to extract the typical scene set， and DS Evidence Theory is used to reduce the dimension； In the dimension of operational performance， the index system including new energy consumption， power loss and feeder balance etc. is proposed， and the dimension is reduced by using the Entropy Theory； Finally in the case of IEEE 33-node distribution network， the flexibility analysis of traditional regulation methods such as reactive power compensation capacitor and no-load tap changer and new regulation method such as Soft Opent Point is carried out， and finally Soft Opent Point shows higher flexibility according to the evaluation method.
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  Discussion on the Design of Edge Computing Architecture for Regional Electricity Retailer

  XU Xiao，CHEN Zhong，DING Hong'en，FANG Guoquan，CHEN Yanxi，DU Puliang

  Electric Power Construction. 2019, 40(7): 41-47. https://doi.org/10.3969/j.issn.1000-7229.2019.07.006

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  In the era of the internet of everything， the amount of data transmission in the power system is increasing rapidly. In order to improve the accuracy and timeliness of data processing in regional electricity retailers， a new data processing architecture based on edge computing is proposed in this paper. Firstly， the definition of edge calculation and the designed framework of nodes are clarified， and some application scenarios of edge computing in power system are introduced. Secondly， the edge computing framework for regional electricity retailers is built by analyzing the models of cloud platforms and edge nodes. At the same time， the overall operation process is designed， and the content of the integrated framework information interaction is discussed in detail. Finally， the edge computing task allocation model of regional electricity retailers is established. The information transmission performance and computational performance of edge computing nodes are analyzed using an example. The result shows that the proposed architecture is superior to the traditional cloud computing method， which provides a new idea for the electricity retailers to formulate the calculation and analysis method of the electricity package.
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  Multi-objective Optimal Configuration Scheme for Distributed Energy Storage in Distribution Network Considering Multi-scenario Requirements

  SUN Chongbo， SONG Yi， CAI Chao， YUAN Kai， YANG Xiong

  Electric Power Construction. 2019, 40(7): 48-56. https://doi.org/10.3969/j.issn.1000-7229.2019.07.007

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  Aiming at optimization configuration of distributed energy storage in the distribution network， an economic indicator model and technical indicator model for energy storage access distribution network are established. An overall configuration optimization scheme of energy storage considering multi-scenario requirements is proposed to meet the interests of multi-agent of source network. The optimization models under different application scenarios of source， network and load side are established and the constraints that should be met are given. The second-order cone-based optimization method is used to transform the large-scale mixed integer nonlinear model into a mixed integer second-order cone optimization model， which improves the solution speed of the optimization problem. On the basis of the specific problems of energy storage configuration of a distribution network in a certain area， this paper optimizes the multi-scenario energy storage allocation in source， network and load side. Compared with the unified optimization scheme， the results show that the proposed multi-objective optimization configuration can be effectively applied to the optimal allocation of energy storage of the actual distribution network.
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  A Dynamic Equivalent Method for Three-Sequence Network Applied to Electromagnetic Transient Simulation of AC/DC System and Its Application in East China Power Grid

  YANG Linchao， LOU Boliang， XU Zheng， ZHOU Hua， HUA Wen

  Electric Power Construction. 2019, 40(7): 57-64. https://doi.org/10.3969/j.issn.1000-7229.2019.07.008

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  Electromagnetic transient simulation can accurately simulate the dynamic characteristics of AC/DC power system under asymmetric faults. In order to reduce the amount of simulating calculation and improve the simulation efficiency， it is necessary to simplify the large-scale power system. A dynamic equivalent method for three-sequence network applied to electromagnetic transient simulation of AC/DC system is proposed. On the basis of dynamic reduction technique for the physical equivalence， this method improves the standard equivalent structures of low-voltage networks， takes into account the negative sequence and zero sequence currents under asymmetric short-circuit faults， adopts a practical engineering method of parameter aggregation of equivalent generators and selection of controller models， makes the impedance of each sequence network of the trunk grid equal before and after the simplification， and gets better simulation accuracy of the equivalent system under asymmetric faults. This equivalent method does not produce negative resistance branches in the simplification process， and avoids the emergence of equivalent transformers with negative resistance or reactance. Thus， the equivalent system can be directly used in electromagnetic transient simulation. Finally， the corresponding equivalent software is developed and applied to the equivalence of East China Power Grid. Simulation results verify the effectiveness of the proposed method.
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  Bilinear Robust State Estimation of Power System Containing UPFC

  WANG Du，YANG Jia，WU Shiqiang，CHEN Zhidao，WANG Weimin，SUN Guoqiang，WEI Zhinong

  Electric Power Construction. 2019, 40(7): 65-75. https://doi.org/10.3969/j.issn.1000-7229.2019.07.009

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  As one of the important components of flexible AC transmission systems （FACTS）， the unified power flow controller （UPFC） plays an important role in the safe and stable operation of power system， and the effective state estimation of the power system containing UPFC is also an inevitable requirement for the power electronizing trend of power system. The robust state estimation of the traditional UPFC model can effectively suppress bad data， but there are problems such as complex model and low computational efficiency. On the basis of the new UPFC topological model， a bilinear method is used to estimate the robust state of the power system containing a UPFC. By selecting effective intermediate variables， the method linearized the nonlinear measurement equation of the power system and UPFC component step by step， which could effectively improve the computational efficiency of state estimation on the premise of engineering application by ensuring that the error level of calculation results is in the same order. The modified IEEE standard system and the actual system of Nanjing west ring network were simulated and tested. By comparing with the WLAV test results， the calculation speed close to weighted least squares （WLS） algorithm was obtained on the premise of ensuring the corresponding accuracy， indicating the effectiveness and practicability of the proposed method.
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  Emergent Coordinated Control Strategy of Regional Interconnected Grid after Tie-Line Fault Outage

  ZHENG Chuanning， YU Qun， CAO Na， CHEN Jing

  Electric Power Construction. 2019, 40(7): 76-84. https://doi.org/10.3969/j.issn.1000-7229.2019.07.010

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  In order to reduce the risk of cascading faults caused by sudden disconnection of tie lines in a large power grid interconnected by multi-area power grids， an emergent coordinated control strategy is proposed to ensure the operation of critical key lines in regional power grids. When the tie line is suddenly disconnected， if the key lines overload， the load nodes in the direction of the power flow will be controlled by centralized load shedding in proportion to the overload rate. Taking the IEEE 118-node power grid as an example， a multi-sandpile blackout accident model which can be used to simulate multiple regional power grids at the same time is adopted to simulate the chain fault process of the power grid after the tie-line fault. The simulation results show that the impact of sudden disconnection of tie lines in multi-area interconnected power grid and the risk of cascading failures are reduced by applying the emergent coordinated control strategy.
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  Method Based on Comprehensive Importance for Critical Line Identification in A Power Grid

  XU Yan， LEI Xiaoshuang， QIN Bin， YANG Hui， LUO Kun， LIU Li

  Electric Power Construction. 2019, 40(7): 85-90. https://doi.org/10.3969/j.issn.1000-7229.2019.07.011

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  More accurate and rapid identification of the key lines of power grid is of great significance to improve the stability of the power grid operation and prevent cascading failure of power grid. Firstly， on the basis of the complex network theory， the improved flow betweenness index is proposed to judge the vulnerability of the branch from the structural point of view after the power disturbance. Then， on the basis of the entropy theory， the weighted flow transfer entropy index considering the load rate of the branch is proposed， which overcomes the shortcomings of the original indicator only considering the uniformity of the transfer flow distribution. Finally， the comprehensive importance assessment index including above two indicators is established to more comprehensively measure the importance of the branch in the power system. Through the simulation， the improved network transmission efficiency curve of the system under different attack modes is obtained. The effectiveness of the method is proved by the simulation of IEEE 39-node system， which is of great significance to prevent the cascading failure of power system.
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  Transient Safety Risk Assessment Method for Super Large-Scale Power Grid Considering Key Scenarios

  HE Hailei， ZHANG Yantao， ZHOU Qinyong， SUN Yujiao， ZHANG Libo，ZHONG Jun

  Electric Power Construction. 2019, 40(7): 91-100. https://doi.org/10.3969/j.issn.1000-7229.2019.07.012

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  In order to solve the problem that scenarios and multiple failures considered are not sufficient in transient-security risk assessment of super large scale power grid， a multiple transient security preconceived fault screening method is proposed， and software that can be applied to the actual power grid is developed. First， index and algorithm of key scenarios based on improved K-means cluster are established. Secondly， the idea of multiple faults screening combined with dimension reduction is proposed. The multiple faults screening indexes and algorithms  considering the risk of power angle stability and voltage stability are established. Finally， large-scale power system fault collection platform based on PSD-BPA power flow program is developed. The effectiveness of the proposed evaluation method is validated by the simulation results of actual power grid.
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  Harmonic Multi-label Classification Based on LSTM

  CHEN Qian，QI Linhai，WANG Hong

  Electric Power Construction. 2019, 40(7): 101-106. https://doi.org/10.3969/j.issn.1000-7229.2019.07.013

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  Long Short-Term Memory network （LSTM） is introduced for the wide access of power electronic equipment， and harmonic pollution is more complicated and the impact is greater. This paper proposes a composite harmonic disturbance classification model that combines LSTM and multi-label classification algorithms. The model firstly extracts the feature values through LSTM， then performs feature dimensionality reduction processing through the fully connected layer， and finally performs multi-label classification and recognition through the classification layer. This model overcomes the shortcomings of artificial feature selection， the slow convergence speed and easy to be limited to local optimum in traditional neural network training. Experiments show that the algorithm model can effectively classify and recognize complex harmonic disturbance under different noise conditions.
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  Research on Deviation Electricity Assessment Model of Wind-Storage Hybrid Power Generators in Electricity Market Environment

  SUN Bo， LI Simin， FAN Yanan， LI Zhiheng

  Electric Power Construction. 2019, 40(7): 107-114. https://doi.org/10.3969/j.issn.1000-7229.2019.07.014

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  As a transitional stage before the formation of the wind power spot market， the assessment of wind power suppliers deviation power is one of the indispensable links in the process of building a wind power market. In order to more intuitively analyze the impact of the deviation power assessment on the economic benefits of wind power suppliers， the wind power suppliers deviation power assessment model is constructed， and the wind storage joint operation measures are adopted to reduce the deviation power that wind power suppliers need to be assessed. On this basis， the revenue model of the wind-storage system in the energy storage system is constructed under different control modes. On the basis of the mixed integer programming technique， the CPLEX optimization software is used to solve the model. The comparison of the energy storage system on the economic benefits of the wind power supplier is carried out， and the sensitivity analysis of the deviation unit power assessment cost and the deviation exemption evaluation coefficient is carried out. The results show that under the mode of controlling the number of times of charge and discharge of the energy storage system， the combined operation of wind power and storage can obtain better economic benefits.
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  Locational Marginal Pricing Model at Distribution-Node Considering Loss  and Its Iterative Calculation Method

  ZHANG Danyang， HU Zechun， WANG Xuanyuan

  Electric Power Construction. 2019, 40(7): 115-122. https://doi.org/10.3969/j.issn.1000-7229.2019.07.015

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  With the rapid growth of distributed generation （DG）， establishing a local power market will be a promising way to integrate DG and guarantee the optimal operation of distribution system. However， locational marginal pricing （LMP） for transmission network cant be applied to distribution network directly. This paper proposes a distribution locational marginal pricing （DLMP） model to clear the local electricity market where DGs bid in pool. The DLMP is decomposed into five components： marginal energy cost for active power and reactive power， marginal loss cost， marginal voltage support cost and marginal congestion cost， which quantify the contribution of each part to the total nodal price. Meanwhile， an iterative solution method is designed to obtain the DLMPs with high precision. Through the iterative calculations of market clearing model and AC power flow， the results obtained can overcome the dependence on the preset parameters （e.g. network loss factor） based on the historical operation information. Finally， simulation results on the IEEE 33-node distribution system demonstrate the effectiveness of the proposed model and accuracy of the proposed method.