01 October 2019, Volume 40 Issue 10

    

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  A Real-Time Dispatch Model Considering the Uncertainty in Photovoltaic Power

  ZHOU Yu, YANG Ming,WANG Fei,WANG Shibo，ZHU Yi

  Electric Power Construction. 2019, 40(10): 1-8. https://doi.org/10.3969/j.issn.1000-7229.2019.10.001

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  When large-scale photovoltaic power generation is injected into power system, the uncertainty of its power output brings new challenges to real-time dispatch, and further puts forward higher requirements for the accuracy of photovoltaic power prediction. To solve this problem, a real-time scheduling method considering the power uncertainty of photovoltaic power generation is proposed in this paper. Firstly, on the basis of the effective steady-state security region method and linear power flow model of real-time dispatching, a real-time dispatching model considering voltage amplitude is proposed in this paper. Secondly, the original problem is transformed into a deterministic linear programming problem by robust optimization. Finally, according to the proposed method, effect of the accuracy of photovoltaic power and load forecasting on the security and economy of power system real-time dispatching is analyzed. In this paper, the effectiveness and efficiency of the method are illustrated by an example of modified IEEE 9-node system and the IEEE 118-node system.
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  Coordination and Optimization  of Combined Heat and Power System Considering Multi-type Demand-Response Load

  GAO Shan,ZOU Ziqing， LIU Yu

  Electric Power Construction. 2019, 40(10): 9-17. https://doi.org/10.3969/j.issn.1000-7229.2019.10.002

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   Integrated demand response （IDR） has been considered a significant way to raise the flexibility of integrated energy system（IES）. By co-optimizing demand response load and energy production conversion equipment， IES will increase the efficiency of energy utilization which in turn lowers the cost of both the energy supplies and consumers. Firstly， the characteristics of demand response load are analyzed， and the demand response load is subdivided into interruptible load， transferable load and adjustable heat load. Secondly， the combined heat power （CHP） system is modeled by the energy hub modeling method， and the demand response load is incorporated into it. On this basis， the operation strategy of the CHP system considering demand response load is constructed. The dispatch model is solved with the goal of minimizing daily operating cost and energy consumption. Finally， the results of case study in two different scenarios show that the participation of demand response load can cut the peak and fill the valley and make the supply and demand more balanced. By coordinating the operation strategy of energy equipment and demand-side load， the daily operation cost of the system is saved by 5.4%， and the energy conversion rate is increased by 2.6%. The economic optimal operation of CHP system is realized.
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  Real-Time Dispatch Considering Flexible Ramping Products in A Power System with High Proportion of Renewable Energy Generation

  LIN Hongji， YAN Yuan， WEN Fushuan， HU Jiahua， QU Haoyuan， ZHAO Zheng

  Electric Power Construction. 2019, 40(10): 18-27. https://doi.org/10.3969/j.issn.1000-7229.2019.10.003

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   The variability and uncertainty brought about by intermittent renewable energy generation （IREG） impose higher requirements on the operational flexibility of the power system. The scarcity of flexibility may result in load shedding and/or curtailment of wind or solar power. Given this background， the concept of flexible ramping product （FRP） thus comes into being and has gradually attracted extensive attentions， since FRP provides an alternative for enhancing the accommodation capability for IREG. Firstly， the definition and characteristics of power system flexibility and the procurement of flexible resources are clarified. Then， a real-time dispatch model considering FRP provided by generation units and demand response resources is presented. In the developed real-time dispatch model， multiple types of demand response resources are taken into account， and some operating constraints are respected including the ones associated with unit start-up/shut-down in future periods and ramping up/down rates. Next， scenarios with various corresponding actual load demands and power outputs from IRES are generated by the Latin Hypercube Sampling method based on forecasted values of load demands and power outputs from IREG， and the dispatch schemes are evaluated by simulating the actual dispatch process. Finally， the role of FRP in enhancing system flexibility and in enhancing the accommodation capability for IREG and the impacts of different factors on the system operational flexibility are investigated through case studies.
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  Optimization Strategy for Start-up Sequence of Generation Units Considering Critical Restoration Paths

  YANG Zhichao， SUN Lei， DING Ming

  Electric Power Construction. 2019, 40(10): 28-35. https://doi.org/10.3969/j.issn.1000-7229.2019.10.004

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  Reasonable start-up sequence of generation units after blackouts is beneficial in improving the generation capacity of power systems， and speeding up restoration process of power systems. Firstly， the restoration characteristic  in the start-up process of generation units is introduced. Both the start-up power curve and generation characteristic curve are modeled. Then， considering the influence of critical restoration paths on the start-up sequence of generation units， a start-up sequence model of generation units is proposed to maximize the total power capacity during the power system restoration. By linearizing the start-up power expression and generation expression of units， the proposed model is reformulated into a mixed integer linear model， which can be efficiently solved by commercial solvers. Finally， the IEEE 39-node system is applied to verify the effectiveness of the proposed model and method.
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  Research on Community-Based Energy Internet Operation Considering the Relationship Between Social Networks

  WEI Zhenbo， LIU Lianghao， GUAN Xiangyou

  Electric Power Construction. 2019, 40(10): 36-44. https://doi.org/10.3969/j.issn.1000-7229.2019.10.005

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  In view of the high social aggregation of users in the community-based energy internet， and the direct influence of users' social relations on their respective load curves， energy purchase cost and transaction decision， a mode of regional comprehensive energy transaction considering social network relations is proposed. Since load transfer among users in the social alliance is helpful to absorb the redundancy of intermittent energy （PV） output， a community-based energy internet trading mechanism with user alliance is proposed. A master-slave game model considering the conflict of interests between community comprehensive energy operators， multi-users and alliance is constructed and solved by distributed genetic algorithm. Simulation results show that user alliance not only has a positive effect on promoting intermittent energy consumption， but also can increase the income of participants. The stronger the user alliance is， the narrower the operator's profits gains， however， the larger the social benefits of the system will be. Especially in the peak period of user load， it can significantly reduce the grid-side power load and alleviate the power supply burden of the power system. Thus， this mode can provide reference for future community-based energy internet operation.
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  Status Analysis on Chinese Tradable Green Certificate Market and the Optimization of Trading Mechanism

  GU Jinwei， LU Yangyang

  Electric Power Construction. 2019, 40(10): 45-55. https://doi.org/10.3969/j.issn.1000-7229.2019.10.006

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  In the market of tradable green certificate （TGC）， an effective trading mechanism and good bidding strategy plays an important role for improving its efficiency. Firstly， under the circumstances that the TGC trades are voluntary in China now， the trading mechanism is introduced and the studies are done on the two aspects of pricing and market performance. Next， on the basis of these analyses， an appropriate multi-round call auction mechanism is designed for improving the efficiency and social welfare， in which a particle swarm optimization （PSO） adaptive bidding strategy  is proposed to accomplish a multi-round quotation and bidding process. This bidding strategy can make both sides of TGC buyers and sellers to adjust their biding price and quantity dynamically. Finally， some experiment simulations are done to verify the feasibility and effectiveness of the trading mechanism and bidding strategy.
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  Review of Subsynchronous Oscillation Analysis Method for On-Grid Wind Power Systems

  YANG Bowen， XIE Xiaorong， YAN Gangui， ZHAN Ying

  Electric Power Construction. 2019, 40(10): 56-63. https://doi.org/10.3969/j.issn.1000-7229.2019.10.007

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  Subsynchronous oscillation occurred in the on-grid wind farms has seriously affected the stability of the whole system and has become a bottleneck to the efficient utilization of wind power. This problem attracts wide attentions from both the industry and the academia. Different study methods have been presented in the literature. In this paper， various analysis methods for subsynchronous oscillations associated with wind power are classified into two categories， namely time domain and frequency domain. A comprehensive review of the methods is given， including their practical application in China and abroad. Considering the fact that the impedance model-based analysis method has received extensive attention recently， the paper focuses on the impedance analysis method and summarizes the latest research results of impedance modeling and stability criteria. Meanwhile， new challenges or open problems are summarized. The direction for future research work is also discussed.
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  Optimization Operation of Active Distribution Network with DG and EV Applying IGDT

  SHI Wenchao，LU Lin，GAO Hongjun，LI Haibo，WEN Jinhu，WANG Jiayi，LIU Jinyuan

  Electric Power Construction. 2019, 40(10): 64-74. https://doi.org/10.3969/j.issn.1000-7229.2019.10.008

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   Under the background of large number of electric vehicles and clean energy generation connected to distribution network， uncontrolled charging of electric vehicles and the uncertainty of clean energy output has a negative impact on the operation of distribution network. By using Monte Carlo simulation to generate the trip characteristics of electric vehicles， and taking time-of-use price as a means of regulation， a coordinated charging controlling strategy is formulated. Considering the uncertainty of distributed generation output， an optimization operation model of active distribution network on the basis of information gap decision theory （IGDT） is established. The objective of the model is to minimize the total operation cost of grid-side， charging user-side and environment-side， and it contains a variety of active management equipment constraints. Considering the different risk preferences of decision makers， the opportunity model and the robust model are established to provide decision-making basis for the formulation of scheduling schemes. Finally， the validity of IGDT model is verified by the improved PG&E 69-node system.
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  Maximum Capacity of Grid-Connected Distributed Generation in AC/DC Hybrid Distribution Network

  HUANG He，GAO Song，HAN Jun，SUN Qirun，WU Zhi，GU Wei

  Electric Power Construction. 2019, 40(10): 75-83. https://doi.org/10.3969/j.issn.1000-7229.2019.10.009

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   The proportion of distributed generation（DG） in the distribution network is continuously increasing， which has a certain impact on the normal operation of distribution network. It is necessary to evaluate the maximum access capacity of the distributed generation. The operation mode of AC/DC hybrid distribution network is more flexible than the traditional AC distribution network. The AC/DC hybrid distribution network has a larger acceptability of the distributed generation and it is the development trend of the distribution network in the future. This paper constructs the maximum capacity evaluation model of distributed generation for AC/DC hybrid distribution network on the basis of Distflow power flow constraint， and then the second-order cone relaxation technique is used to deal with the non-convex and nonlinear constraints in the model. The model is transformed into a solvable mixed integer second-order cone programming model to be solved. Finally， the effectiveness of the model is tested in a 94-node distribution system. The maximum access capacity of the distributed generation and the corresponding influencing factors of the AC distribution network and the AC/DC hybrid distribution network are also analyzed. The results show that the maximum access capacity of the distributed generation in AC/DC hybrid distribution network is larger than that of the traditional AC distribution network.
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  Adaptive Synchronization Frequency Control for Interconnected Micro-grids in Island Mode

  ZHONG Yongjie，ZHAI Suwei，SUN Yonghui

  Electric Power Construction. 2019, 40(10): 75-83. https://doi.org/10.3969/j.issn.1000-7229.2019.10.011

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   On the basis of load frequency control （LFC） related technology， a new generalized dynamic LFC model and a robust decentralized LFC control strategy are proposed in this paper for the power system composed of interconnected micro-grids （MGs） in island mode. Firstly， the LFC mechanisms of a single area and multi-area control system are described， and the classical LFC scheme is applied to power system with changeable scene and interconnected MGs in island mode. Secondly， for a power system with six interconnected MGs in island mode， a kind of coordinated control strategy is proposed on the basis of consistency of LFC algorithm， where by controlling the turbine governor input and managing the amount of energy that energy storage systems （ESS） have to absorb/inject from/into MGs， a new adaptive synchronization frequency control method for islanding MGs is proposed. Then， it is illustrated that ESS under saturation constraint can reduce the instability caused by small inertia and small damping in MGs. Finally， the correctness and effectiveness of the proposed algorithm are verified by the simulation results with the power system including six interconnected MGs， which shows that the proposed controller can minimize the impact of interference and maintain robust performance of the interconnected MGs in island mode.
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  Capacity Configuration of Inter-Linking Converters in AC/DC Hybrid Micro-grid Considering Energy Storage Scheduling

  ZHU Yongqiang， LIU Kang， ZHANG Quan， TIAN Yuan， CAI Bingqian， XIA Ruihua

  Electric Power Construction. 2019, 40(10): 84-93. https://doi.org/10.3969/j.issn.1000-7229.2019.10.010

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   Inter-linking converter is the key equipment for power exchange between AC and DC sides in AC/DC hybrid micro-grid. It can coordinate the power distribution between AC and DC sides and improve the power quality of the system. In the design stage of the micro-grid， determining the configuration capacity of inter-linking converter is the key step of engineering construction. Aiming at the state of distributed power generation， energy storage and load on both sides of AC and DC at the sampling time， the power flow of inter-linking converters is analyzed on the basis of flexible scheduling of energy storage on both sides， and the theoretical transmission power constraints of inter-linking converters at sampling time are obtained. The dual-objective capacity allocation model of inter-linking converters in AC/DC hybrid micro-grid is established from two aspects of economy and voltage deviation. The optimal capacity of inter-linking converters is obtained by using multi-objective particle swarm optimization algorithm. Finally， the validity of the proposed model and solution method is verified in a simulation example.
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  Research on Attack and Defense Strategy of Substation Network Security Applying Markov Decision Process

  SONG Jiahan，LI Jingjiao，PI Jie，OUYANG Zongshuai，WANG Haiming，FAN Youping

  Electric Power Construction. 2019, 40(10): 104-110. https://doi.org/10.3969/j.issn.1000-7229.2019.10.012

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  Considering that the defense capability of substation is more and more important in maintaining the safe and stable operation of power grid in an increasingly complex network security environment， this paper proposes a method for modeling the attack/defense strategy of substation network on the basis of Markov decision process（MDP）. Firstly， the detailed steps of the network attack are introduced and the possible paths of successful intrusion into the substation are analyzed in depth. Then， the probability model of successful network attack is established from the perspective of attacker and defender respectively. Finally， according to the characteristics of the target substation， Markov decision process modeling is used to solve the optimal action strategy of both attack and defense. The method comprehensively considers the key characteristics of the target substation and the technical capabilities of the attack/defense sides， and provides a theoretical basis for the attack/defense of both sides in the behavior design of the power cyber-physical system（CPS）in network security scenario.
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  Power Generation Optimization Strategy Based on Static Model for Concentrating Solar Power Plant

  ZHANG Zhongdan， LI Jinjian， WANG Xinggui， ZHAO Lingxia

  Electric Power Construction. 2019, 40(10): 111-117. https://doi.org/10.3969/j.issn.1000-7229.2019.10.013

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  At present， the concentrating solar power （CSP） station is still in the initial stage and the research on the operating efficiency or generating capacity is majorly started from thermal storage medium or thermal storage. Little research has been done to optimize from the energy flow. In view of the above problem， a power generation optimization strategy based on the static model for CSP is established to improve power generation and operating efficiency. Firstly， according to the operating mechanism of the CSP station， the energy flows of subsystems and those among them are simplified reasonably， and the static energy flow mathematical model of CSP is obtained. Then， an optimization strategy， which takes the maximum amount of power generated by the CSP station as the objective function and the mathematical model of static energy flow as the restriction is proposed. The Smith Predictor is adopted to get over the negative effect caused by the time lag link. Finally， the MATLAB is used to verify the correctness of the optimization strategy. The results show that the optimization strategy can effectively improve the power generation and the operating efficiency of the CSP station.
  
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  Planning and Operation Joint Optimization of Energy Storage System in Prosumer Smart Community

  CHENG Yu， WANG Wang

  Electric Power Construction. 2019, 40(10): 118-125. https://doi.org/10.3969/j.issn.1000-7229.2019.10.014

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  Aiming at the smart community with dual forms of production and consumption， a joint optimization model of energy storage system planning and operation and its solution algorithm are proposed in this paper. Considering the classification regulation characteristics of controllable load resources in the smart community， the capacity loss characteristics of the energy storage system and the uncertainty of distributed photovoltaic output， combining the scenario method and chance constraint programming， a stochastic optimization model is established and converted into a mixed integer linear programming model （MILP） for solving the problem. The influence of the substation capacity， the confidence of chance constraint and the cascade utilization of battery on the decision of the community economic allocation on energy storage system is analyzed. The results show that the model can be used to optimize the energy storage capacity planning and the operation schedule of smart community considering the uncertainties of renewable energy.
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  Research on Protection Method Based on Time-Spectrum for Hybrid HVDC Transmission Line

  NING Wenyuan1， YANG Xiaonan2， LIU Yinglin3， LIU Yanying3， LUO Guomin3，WANG Xiaojun3

  Electric Power Construction. 2019, 40(10): 126-132. https://doi.org/10.3969/j.issn.1000-7229.2019.10.015

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   With the increase of transmission capacity and the demand of multi-drop load， transmission lines are no longer just two-end transmission， and converter stations are not only a single type. Hybrid multi-terminal HVDC transmission system is an inevitable trend. However， the existing protection methods for traditional and flexible HVDC transmission can't be directly applied to hybrid multi-terminal HVDC transmission system. Aiming at the requirement of special structure and high speed of hybrid multi-terminal HVDC transmission system， this paper presents a protection method for hybrid HVDC transmission line on the basis of single-terminal time-frequency spectrum transient electrical quantity. Firstly， comparing the grounding current with the steady-state current， the polar selector is constructed according to the direction of the integral value of the current variation， and the criterion of internal and external identification is constituted according to the spectrum component of the current. Finally， the simulation model of Wudongde HVDC transmission project in PSCAD/EMTDC is built to verify the theory. According to the simulation results， the proposed protection method can accurately identify internal and external faults， select fault poles， and resist certain transition resistance and noise interference.