01 February 2019, Volume 40 Issue 2

    

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  Bidding Strategy of Electricity Market Including Virtual Power Plant Considering Demand Response Under Retail Power Market Deregulation#br#

  HE Qilin, AI Qian

  Electric Power Construction. 2019, 40(2): 1-10. https://doi.org/10.3969/j.issn.1000-7229.2019.02.001

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  The opening of the retail market is one of the key tasks of the power system reform in China. In this paper, under retail power market deregulation, we consider the influence on demand-side resource participating in electric market, propose a bidding strategy of virtual power plant considering demand response, and set up a bidding model for the whole market including virtual power plant （VPP）. On the basis of the optimization of the virtual power plant, we use the adaptive learning method to solve the model, and clear the market with the goal of maximizing the social benefit. Finally, an example is selected to verify the validity of the bidding strategy, and the results show that the economy of the generation companies and retailing suppliers is improved and the demand for electricity in the whole market is adjusted. What's more, retail power market deregulation is benefit to demand-side resources participating in market competition.
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  Optimal Model for Daily Deviation Penalty of Electricity Retailer Considering Real-time Electricity Trading

  MA Jiale， TAN Zhongfu， YU Xiaobao， TAN Qingkun， DE Gejirifu， ZHAO Rui

  Electric Power Construction. 2019, 40(2): 11-19. https://doi.org/10.3969/j.issn.1000-7229.2019.02.002

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  The purpose of starting the spot market is to establish a market-based power balance mechanism that combines medium and long-term power transactions with spot transactions. In the early construction stage in which the market operation mechanism is not perfect， the short-term assessment mechanism with a daily settlement period is conducive to fair market transactions and stabilize power fluctuations in the spot market. With the objective of intuitively reflecting the impact of short-term deviation power assessment on the revenue and business strategy of the electricity retailer， a revenue model in day-ahead market of the retailer that takes into account the daily deviation power assessment mechanism is constructed. On the basis of real-time market purchase and electricity trading with energy storage stations a daily deviation power assessment optimization model with the objective of maximizing revenue of retailer is established. According to the 2017 transaction data of Guangdong Power Market， the typical daily spot transaction and actual power consumption are simulated. Moreover， sensitivity analysis of uniform clearing price， unit assessment cost， transaction price with the energy storage station and positive and negative deviation is conducted. The results show that the optimization strategy can significantly improve the revenue of the retailer；uniform clearing price， unit assessment cost and the prices of electricity purchased from the energy storage station have the greatest impact on the additional cost；the prices of electricity sold to energy storage power stations have the greatest impact on additional revenue；positive and negative deviations have the greatest impact on the overall revenue of the retailer.
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  Research on Combined Dispatching Mode of Energy Storage in Energy Market and Regulation Market

  XIE Min，WEI Wei，LI Jianzhao，LIU Mingbo

  Electric Power Construction. 2019, 40(2): 20-28. https://doi.org/10.3969/j.issn.1000-7229.2019.02.003

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  With the steady development of reforming in power market and the breakthrough of energy storage technology， the study of energy storage as a trader participating in the trading mechanism of power market has gradually attracted the attention of researchers， which has become an important problem to be solved urgently for further deepening the commercial operation of energy storage. Taking compensation mechanism of frequency modulation in California as a major application background， according to the power system 'supply-network-load-storage' coordination characteristics， as well as the technology operation and regulation characteristics of energy storage， considering the relevance of regulation capacity and regulation mileage of energy storage power station， this paper constructs a combined dispatching model for the energy storage as a trader to participate in the energy market and regulation ancillary service market. Simulation based on the improved IEEE 39-node system verifies the performance of the energy storage system in the California mode. The paper also analyzes the operating characteristics of the energy storage system and its impact on the system operation， as well as the profit distribution characteristics of the energy storage in the energy market and the regulation ancillary service market， which is profound significance to the localization of mature application mode of foreign energy storage participating in market.
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  Multi-objective Clearing Model of Distribution Market with Microgrids Considering Demand Response

  WANG Hui， LIAO Kun， LIN Yixuan， JIN Binbin

  Electric Power Construction. 2019, 40(2): 29-36. https://doi.org/10.3969/j.issn.1000-7229.2019.02.004

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  The efficient and rational application of the microgrid is conducive to accelerate the low-carbon development of the power industry. With the advancement of electricity market reform， a scientific and rational market competition mechanism will have an important effect on the marketization process of the microgrid. In order to solve the problem of microgrid surplus bidding online， and by fully considering the characteristics of microgrid， a multi-objective bidding clearing model based on block bidding considering demand response is established. The model takes into account the economy and the low-carbon performance of the system. Then an optimized method for translational load and more reasonable hybrid settlement method are proposed. The non-dominated sorting genetic algorithm （NSGA-II） is used to obtain the Pareto solution set for the multi-objective model and the fuzzy clustering method is used for decision making. The results of the example show that the multi-objective bidding clearing model based on the block bidding can improve the market competitiveness of the microgrid and improve the low-carbon performance of the system， and has played a positive role in low carbon economy and environmental protection.
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  Distribution Planning Model in Active Distribution Network Considering Fuzziness and Randomness

  FAN Zhicheng， ZHU Junpeng， WU Han， YUAN Yue

  Electric Power Construction. 2019, 40(2): 37-44. https://doi.org/10.3969/j.issn.1000-7229.2019.02.005

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  With large-scale DG accessing into the power system， the mismatch between generation planning and grid structure has aroused people's concern and thinking. Therefore， from the view of the optimal allocation of DG and considering the optimization of grid structure， a DG planning model of active distribution network with fuzziness and randomness is established. Firstly， strong uncertainty introduced by DG， a typical day scene method， which takes into account the fuzziness and randomness of distributed generation output， is proposed to improve the accuracy of the model. Then， the bi-level DG planning model of the active distribution network is constructed with the maximum annual income of the DG suppliers and the minimum annual network loss cost of the distribution company. In addition， in order to promote the consumption of DG， the upper model also considers coordinated optimization process of energy storage system. Finally， on the basis of the improved IEEE 33-node system， the GAMS-DICOPT solver and discrete particle swarm optimization algorithm with adaptive weight are used to solve the planning model， and the validity of the model is verified. The result shows that through the rational allocation of DG and the optimization of grid structure， the multi-stakeholder's win-win situation can be realized and the consumption of DG will be promoted at the same time.
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  Study on Virtual Inertia Dynamic Interval Control Strategy for VSG

  SONG Zhenhao， LU Limin， XU Zheng3，LU Zhipeng， WU Ming， ZHAO Ting

  Electric Power Construction. 2019, 40(2): 45-53. https://doi.org/10.3969/j.issn.1000-7229.2019.02.006

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  With the high penetration of photovoltaic power generation system accessing power grid， due to the lack of the moment of inertia， the photovoltaic inverter seriously threatens the stability of the system. According to the traditional generator's model， the equivalent model of the virtual synchronous generator is established. According to the principle of power conservation， when the photovoltaic power output is fluctuating or the load fluctuates， due to the existence of energy storage and the controllability of its power， the battery can provide transient power similar to that on the rotor of the synchronous generator. Because characteristics of the battery is different from the rotor which stores energy through rotation， the battery provides different inertial support under different SOC state. At the same time， in order to ensure the stability of the system frequency， minimum moment of inertia is needed. In this paper， an adaptive optimal control scheme for VSG is proposed according to the change of SOC and the improvement of frequency. Finally， simulation results in MATLAB/simulink verify the effectiveness of the analysis.
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  Clustering and Simulation of Photovoltaic Output Adopting Markov Model

  XU Shanshan， ZHU Junpeng， YUAN Yue， WU Han

  Electric Power Construction. 2019, 40(2): 54-62. https://doi.org/10.3969/j.issn.1000-7229.2019.02.007

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   Processing data properly and constructing a rational photovoltaic output model is the base of power system operation and plan. Focusing on characteristics of photovoltaic output， a photovoltaic output clustering and simulation method based on Markov model and spectral clustering is proposed. Firstly， the amplitude parameter， the standard component and fluctuant component are extracted from photovoltaic output and Markov model is adopted to analyze the fluctuant component. We use spectral clustering and Alpha value， Silhouette index and Bayesian information criterion to evaluate the quality of clustering results and to determine the optimal cluster number. Then， state-transition matrixes between the weather in the month and power output in the day are integrated， and a bistratal Markov model is constructed. Finally， the mid/long term photovoltaic simulating output is generated by utilizing the bistratal sampling. Compared with the K-means clustering analysis， spectral clustering is more suitable for processing photovoltaic output data， especially in the condition of data missing or data error and in distinguishing weather data. Through the comparative analysis on statistical characters， timing characters and weather characters， the validity of the proposed model is verified.
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  Layered Wind Power Dispatching Control Strategy Based on DSA Power Prediction Model

  LIU Qi1， FANG Junjun， ZHAO Jie， ZHANG Shengfeng， LIU Dichen，CHEN Yin

  Electric Power Construction. 2019, 40(2): 63-70. https://doi.org/10.3969/j.issn.1000-7229.2019.02.008

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  In order to enhance the capacity of wind power high-permeability grid and improve control accuracy and operational economy， this paper improves and proposes a layered control strategy based on DSA power prediction model wind power dispatch. The active power scheduling is divided into system layer， wind farm group layer， group sub-field layer， wind power generation unit layer and feedback correction layer. The DSA model is used to predict the ultra-short-term power output of wind farm， taking into account the constraints of the grid and the safe operation of the wind power units. The coordinated control relationship between levels and corresponding power allocation method for each level are eliminated， and the error is corrected by rolling optimization. Analysis of the example demonstrates the effectiveness of the proposed control strategy. Compared with existing control strategies， the prediction accuracy is higher. Under the condition of large power fluctuation， the root mean square error of the control is small， and the number of starts and stops of the wind power units can be effectively reduced. It reduces the network loss of the system and has the advantages of high control precision and fast response speed.
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  A Partitioning Method for Distribution Network with Flexible Multi-state Switches

  ZHANG Jin，JIANG Quanyuan，ZHOU Ziqiang，LU Yi，YANG Yong

  Electric Power Construction. 2019, 40(2): 71-78. https://doi.org/10.3969/j.issn.1000-7229.2019.02.009

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  Flexible multi-state switch is a new kind of intelligent distribution device. Considering the functional characteristics， the requirement of partitioning distribution network with flexible multi-state switches is proposed. According to the theoretical framework of the multi-level graph partitioning， a partitioning method which contains of three stages of coarsening， partitioning and refinement is proposed. In the coarsening stage， a method aiming at minimum electrical distance is given. After the initial partitioning is completed by the greedy growing graph partitioning algorithm， the preliminary splitting boundary will be refined by the path searching algorithm. The proposed method can not only optimize the operation indices of the distribution network， but also increase the flexibility and controllability of the distribution network. IEEE 118-node test system is used to demonstrate and validate the effectiveness of the splitting strategy. As for the partitioning result， further analysis is made while considering the regulation of flexible multi-state switch. The result shows the partitioning method can not only improve the average feeder load balance index， but also improve the feeder load balance and voltage distribution cooperated with the regulation of flexible multi-state switch.
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  Research on Stability Control of Microgrid Applying Virtual Synchronous Generator with Adaptive Parameters

  HUO Xianxu， WU Pan， HUANG Xin， YAN Jingjing， WANG Keyou， XU Ke， YAO Cheng， CHEN Peiyu

  Electric Power Construction. 2019, 40(2): 79-86. https://doi.org/10.3969/j.issn.1000-7229.2019.02.010

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  With the rapid development of the distributed generation technology and microgrid technology， more and more power electronic devices are used in modern power system especially in microgrids. Meanwhile， power electronic converters in microgrid may affect the stability of the system due to lack of necessary inertia and damping. To deal with the problem， this paper， by simulating the traditional synchronous machine rotor equation， equips the droop control with virtual inertia and damping to set up a virtual synchronous generator control model for inverter control. Next， the influence of inertia and damping parameters on the control stability of the virtual synchronous generator is studied. By designing reasonable trigger mechanism， the virtual synchronous generator control strategy with adaptive parameters is put forward， which can flexibly switch adaptive parameter adjustment mode according to control requirements. At last， simulation result and comparative analysis show that the proposed strategy is beneficial to enhance the frequency and power stability of the system to a certain extent.
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  A Method of Determining the Second Order Component of Arm Current to Reduce the Sub-module Capacitance for Modular Multilevel Converters

  FAN Qiang， LU Feng， ZHANG Fan， LI Yu， ZHAO Chengyong， XU Jianzhong

  Electric Power Construction. 2019, 40(2): 87-93. https://doi.org/10.3969/j.issn.1000-7229.2019.02.011

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  Modular Multilevel Converter （MMC） has wide prospects in engineering application. It is also of great engineering significance to reduce voltage fluctuation of sub-module（SM） capacitor in MMC to realize the lightening of MMC converter. Various control methods of sub-module capacitor for voltage fluctuation reduction are made a systematic summary and the essence of all kinds of methods for capacitor voltage fluctuation reduction is to inject the harmonic voltage and current into the arm of MMC. In addition， a method for determining the amplitude of the second order circulating current and phase angle of the arm current is proposed. And simulation program used for verification is built in the PSCAD/EMTDC. The simulation waveform shows that the ripple amplitude of sub-module capacitor voltage can be effectively reduced. Further， low capacitance simulation is performed. It can be concluded that when the ripple voltage amplitude of the sub-module capacitor keeps constant， the capacitance of the sub-module can effectively reduce more than 30%. And a loss analysis of MMC converter is made. The result demonstrates that the loss of MMC under low capacitance condition is not greater than that under contrast condition.
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   Non-intrusive Load Identification Method Based on Selected Bayes Classifier

  JIANG Fan, YANG Honggeng

  Electric Power Construction. 2019, 40(2): 94. https://doi.org/10.3969/j.issn.1000-7229.2019.02.012

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    Non-intrusive load identification can provide information of household loads and improve users' habits, and it is the key technique of smart power utilization. Current non-intrusive load identification methods mainly use steady-state characteristics of loads；usually result in inaccuracy when the loads have similar steady-state characteristics. As various household loads have different peculiarity on switching process, this paper proposes a new identification method based on selected Bayes classifier. Firstly, simulated annealing algorithm is adopted to select the most recognizable characteristics of loads from database for characteristics. Secondly, the flexible Bayes classifier is built on the basis of the selected characteristics and Gaussian kernel density estimation methods. Finally, posterior probability is calculated to identify the load. The measured data shows that the proposed method has high identification accuracy and calculation speed.

  This work is supported by National Natural Science Foundation of China （No. 51477105 ）.

   
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   VSC-HVDC Inverter Control Strategy Based on VSG Technology

   

  LIU Zhongyuan, WANG Weiqing, WANG Haiyun, YUAN Chengyu, WANG Liang, LI Yongqin, DING Wenbin

  Electric Power Construction. 2019, 40(2): 100. https://doi.org/10.3969/j.issn.1000-7229.2019.02.013

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   With the traditional converter control strategies, the dynamic frequency regulation of the AC power system and the unbalanced power transmission between the AC and DC systems are hard to be involved in voltage source converter based high voltage direct current（VSC-HVDC）system. Aiming at the problem, on the basis of the research on the characteristics of the virtual synchronous generator （VSG） technology, a VSC-HVDC inverter control strategy based on VSG technology is proposed. Firstly, according to the VSC-HVDC system topology model, the feasibility of virtual synchronization of converter station is analyzed. Secondly, the VSG technology with fuzzy PI droop control for active power is introduced into the HVDC transmission system. By adjusting the droop coefficient, the inverter of the flexible HVDC transmission system can ensure the active power transmission balance when the system under steady-state operation and transient faults, so that it has the ability to coordinate control the AC system frequency and the DC system voltage. Finally, a model of three-terminal system is built in Matlab/Simulink for simulation verification. The results show that the VSC-HVDC system can improve the inertial of the AC grid and reduce the change rate of frequency after adopting the VSG control strategy. The FM control can provide better support in the steady state and transient state, which improved the performance of AC and DC system effectively, as well as the reliability of the system. 

  This work is supported by National Natural Science Foundation of China （No.51667020） and Xinjiang Uygur Autonomous Region Key Laboratory Project（No.2016D3021）

   
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   Study on System Stability Control Measures for Steady-state Overvoltage in UHV Half Wavelength Transmission Lines

   

  LIN Weifang, YI Jun, JIA Junchuan, WANG Ansi, YU Fangfang, FANG Shihui

  Electric Power Construction. 2019, 40(2): 109. https://doi.org/10.3969/j.issn.1000-7229.2019.02.014

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   Half wavelength AC transmission technology is a forward-looking and competitive new transmission technology. The steady-state overvoltage of ultra-high-voltage （UHV） half wavelength transmission lines is serious. It is necessary to focus on the stability control measures after fault. In this paper, the control measures is put forward, such as reducing power generation at the sending terminal, applying shunt reactive power compensation at the end of the line, and fast modulating direct current power. The relevant theoretical analysis is given, and the effectiveness of the control measures is verified by the large power grid simulation. The characteristic of UHV half wavelength transmission system is enriched and the theoretical and technical support is provided for the future new transmission technology by the paper research.

  This work is supported by State Grid Corporation of China Research Program.