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10 August 2020, Volume 37 Issue 4
Energy Storage
Design criteria of energy storage power plants and typical case studies
LI Jianlin, TAN Yuliang, WANG Han
2020, 37(4):  331-340.  doi:10.19725/j.cnki.1007-2322.2020.0177
Abstract ( 110 )   PDF (1239KB) ( 103 )  
At present energy storage power stations distributed in northwestern provinces in China were put into operation one after another and it provided valuable practical experiences for the development of energy storage power stations. However, there was short of uniform design specifications and criteria for the construction of energy storage power stations. For this reason, the roles that the energy storage power system could play in the power station were presented, and then both standards and technical specifications for the design of energy storage power station, the guide of model choice and testing of the battery and the grid-connection of the energy storage power station were sorted and analyzed. By means of introducing and demonstrating the internal energy storage structure applied in typical energy storage power station in China, the design criteria to be followed in the construction of energy storage power station in the future were obtained, and the issues to be pay special attention were discussed.
Optimal allocation of energy storage systems considering flexibility in distribution network
ZHU Xiaorong, LU Guowei
2020, 37(4):  341-350.  doi:10.19725/j.cnki.1007-2322.2020.0087
Abstract ( 62 )   PDF (1202KB) ( 45 )  
To deal with the drastic fluctuation of net load caused by large amount of distributed power generation connected to distribution network, based on the combination of local restriction with quantitative evaluation of overall flexibility a method to optimally allocate the energy storage system was proposed. Firstly, the X-mean method was utilized to analyze the annual operation scenario of distribution network and through the clustering the key scenario was chosen. Secondly, the quantitative calculation model of operation flexibility in distribution network and the local flexibility constraint were established. Finally, based on the established flexibility evaluation model, a bi-layer iterative model to solve the optimal allocation of energy storage systems in distribution network was constructed. The standard IEEE-33 bus distribution network system was utilized in the design and simulation of a real distribution network. Simulation results show that the proposed flexible planning method for the allocation of energy storage systems in distribution network is effective and economic.
New Energy Power System
Day-ahead Photovoltaic Power Generation Forecasting Based on DPK-means and ELM
LI Wen, WEI Bin, HAN Xiaoqing, GUO Lingjuan
2020, 37(4):  351-357.  doi:10.19725/j.cnki.1007-2322.2019.0929
Abstract ( 59 )   PDF (980KB) ( 25 )  
The day-ahead photovoltaic (PV) power generation forecasting was an important evidence in power grid economic scheduling, and the K-means clustering algorithm and neural network were widely used in the power generation forecasting. In allusion to the defects in K-means clustering algorithm, i.e., not easy to determine the initial clustering center and the number of clusters, and the imperfection of neural network, i.e., too many training parameters and easy to falling into local optimum, an algorithm, in which the DPK-means was combined with extreme learning machine (ELM), was constructed to implement the day-ahead forecasting of PV power generation. Firstly, utilizing density peaks clustering (DPC) abovementioned defects in K-means clustering was revised. Secondly, the DPK-means algorithm was used to carry out the clustering analysis on historical meteorological data samples, on this basis an ELM forecasting model was established to implement the forecasting of day-ahead PV power generation. Case study results show that using the proposed combined forecasting algorithm a better forecasting result can be obtained, so the proposed algorithm is feasible.
Operational Risk Assessment of Power System Considering Wind Power and Photovoltaic Grid Connection
SHANG Haoyu, LIU Tianqi, BU Tao, HE Chuan, YIN Yue, DING Lijie
2020, 37(4):  358-367.  doi:10.19725/j.cnki.1007-2322.2020.0112
Abstract ( 42 )   PDF (747KB) ( 31 )  
To make more rational planning and construction of grid-connected new energy system and improve its operational security, an operational risk assessment model of power system, in which the grid-connected wind and photovoltaic (PV) power stations were taken into account, was proposed. On the basis of taking the uncertainty of wind and PV power output, load fluctuation and the real-time status of transmission lines and generators into account, the joint wind and PV power output and the affection of the weather on the outage rate of transmission line were considered to perform the risk assessment more exactly. On the basis of traditional risk index system, where the out-of-limit of voltages, the voltage collapse, the out-of-limit t of active power of transmission lines were taken into account, the sources of risk were more comprehensively considered. Leading in the composite risk indices covering above mentioned indices and combining with analytic hierarchy process (AHP) and entropy weight method, the weight of each index was respectively calculated, thus the obtained results were more objective. Utilizing non-sequential Monte Carlo method the system state was extracted to perform risk assessment. Taking IEEE-14 bus system for example, the influences of the grid-connecting positions of new energy power generations to power grid and the influence of joint power output of wind and PV power generation on power system operational risks are qualitatively analyzed to verify the proposed model and method. The simulation results could be referenced for the risk assessment of grid-connected new energy system represented by wind and PV power generation.
Quantitative Analysis on Transient Stability of Extended Single-Machine Infinite System Containing DFIG under Asymmetric Faults
ZHANG Xuejuan, SUN Shiyun, ZHENG Xinyu, ZHAO Wei, WANG Chunyou
2020, 37(4):  368-375.  doi:10.19725/j.cnki.1007-2322.2020.2020.0113
Abstract ( 31 )   PDF (1697KB) ( 12 )  
In allusion to the extended single-machine infinite system containing double-fed induction generator (DFIG), the influence of switching in DFIG on transient angle stability of the system under asymmetric faults was analyzed. Based on impedance equivalent model of DFIG, the detailed expression of the limit clearing angle of the system containing DFIG under asymmetric fault was derived according to the equal-area criterion, meanwhile the effect of the two influencing factors, i.e. the ratio occupied by the wind power and the grid-connected position of the wind turbine, on the limit clearing angle of the system containing DFIG was taken into account, thus the effect of the two influencing factors on transient angle stability of the system was obtained and the applicability of the two influencing factors for different types of DFIG models were analyzed. A simulation model of an extended single-machine infinite system containing DFIG was established in PSD-BPA to verify the correctness of the theoretical analysis. Simulation results show that the results of the theoretical analysis are correct.
Energy Internet
Game Theory Based Optimization Allocation of Generators in Virtual Power Plant
HOU Chenjia, LIANG Haining, ZHAO Dongmei
2020, 37(4):  376-384.  doi:10.19725/j.cnki.1007-2322.2020.0119
Abstract ( 56 )   PDF (1481KB) ( 31 )  
Along with the encouragement and support from national policy, it is a general trend that a large amount of distributed power generation resources are being grid-connected to power grids. The uncertainty of power output of single distributed power plant leads to the limitation of grid-connection of single distributed power plants, and this problem could be effectively remitted by virtual power plant utilizing cluster complementary effect between multiple power sources. By use of game theory the generators in virtual plants were configured, and the installed conditions of investors in different power generation ways such as wind power generation, PV power generation, fossil fuel power generation and so on under various cooperative modes and non-cooperative modes were analyzed to allocate the revenue among the participants of the cooperative modes. It was considered that the game model might be more complex under N-person game, and it was possible to appear the situation that the individual reason was not inconsistent with the entire reason, thus it led to the overall revenue not too enough, so combining with the installed power supply ratio and the participants’ risk preference coefficients the Shapley value distribution method was improved. The effectiveness of the proposed method is verified by simulation results
Short-Circuit Current of Inner Mongolia Power Grid with Asynchronous Interconnection Project
LI Dandan, WU Haiyan, ZHANG Aijun, CHEN Xiang, LIU Shichuan, LIU Huiqiang
2020, 37(4):  385-390.  doi:10.19725/j.cnki.1007-2322.2019.0427
Abstract ( 28 )   PDF (949KB) ( 17 )  
With the development of the Inner Mongolia power grid, short-circuit current exceeding the standard has become one of the most prominent problems in recent years. The asynchronous interconnection model of back-to-back HVDC transmission system was established with the planned Inner Mongolia 500kV power grid in 2023 as the research target. Based on the model, PSD-SCCP was uesed to scan the entire network for three-phase and single-phase short-circuit currents on 220 and 500kV buses before and after the Inner Mongolia Power Grid Asynchronous Networking Project was connected. It can be concluded that after the asynchronous network project was put into operation, it could reduce the overall short-circuit current level of the Inner Mongolia power grid to a certain extent, especially the effect of limiting the short-circuit current level of the bus near the converter station was very obvious. However, for areas that is far from the converter station, the restriction effect was not obvious. The effectiveness and limitations of asynchronous networking schemes in limiting short-circuit current were verified. Therefore, for the short-circuit current exceeding the standard of the Inner Mongolia power grid in 2023, a combination of asynchronous networking solutions and other traditional measures to limit short-circuit current can be adopted to deal with it.
Smart Grid
Control Strategy of Flexible DC Distribution System Based on Droop Characteristics
LI Yinghan, GAO Liang
2020, 37(4):  391-398.  doi:10.19725/j.cnki.1007-2322.2020.2019.0574
Abstract ( 44 )   PDF (5432KB) ( 14 )  
The flexible DC power distribution system could operate in various ways and the source-load power fluctuations have high-frequency randomness. In order to solve the problems of low power quality, unreasonable power distribution and unsatisfactory voltage dynamic regulation under traditional droop control, a control strategy combining adaptive control, predictive control and droop control was proposed. Firstly, the DC voltage deviation compensator was designed to track the stable working voltage of the system in real time, and the dynamic influence factor was set for the traditional droop coefficient. The droop coefficient was adaptively adjusted, and the power was reasonably distributed according to the power margin of each converter station. Then the predictive control method was introduced in the inner current control loop to avoid the weakening control effect due to improper PI parameter tuning, and further improve the dynamic response capability of the system. The simulation model of double-ended flexible DC power distribution system was built on PSCAD, and the simulation of different operating conditions verified the effectiveness of the strategy.
BDI Agent Based Non-Player-Character Intelligent Simulation Technology and Its Application in Dispatcher Training Simulator
QI Xiaolin, LV Yan, HAN Yi, LI Yuanyuan, LI Zhihong, SONG Xuri, DI Fangchun
2020, 37(4):  399-407.  doi:10.19725/j.cnki.1007-2322.2020.0094
Abstract ( 31 )   PDF (991KB) ( 12 )  
To remedy such imperfections in multi-level dispatcher training simulator (DTS) as wide cross-domain, communication conflicts among multi-users and multi roles and unable to simulate the instructing process of the dispatcher, a non-player-character (NPC) intelligent simulation method based on BDI Agent was proposed. By means of analyzing the NPC features in the game and integrating it with DTS, a BDI Agent based NPC model was constructed, the behavior tree and sub-behavior tree for dispatcher training simulator was designed and the message event triggering technology was utilized to implement message interaction among multi-NPCs and automatic triggering of grid events. Comparing the proposed method with the process of traditional simulation system, both feasibility and practicality of NPC intelligent simulation technology in multi-level DTS are verified, thus the traditional artificial and unified training mode of dispatchers can be replaced by intelligent and differentiation training mode.
Control Strategy of MMC Receiving Converter Based on Virtual Synchronous Generator
CHEN Jikai, ZENG Qiang, LI Lin, JIA Xiaohua, XIN Yechun, LI Guoqing
2020, 37(4):  408-415.  doi:10.19725/j.cnki.1007-2322.2019.0998
Abstract ( 35 )   PDF (1224KB) ( 20 )  
The power electronic topological structure of Modular Multi-level Converter (MMC) determines its feature of zero inertia, so it cannot support the system inertia, thus both fluctuation of DC transmitted power and short-time power unbalance in AC system could leads to an evident frequency deviation in AC power grid connected to thermal power generating units. To remedy this defect, a virtual synchronous generator (VSG) based control strategy for receiving converter of MMC was proposed. In this control strategy a first-order damp link was added into the outer-loop control of MMC to provide inertial parameter and damping parameter for the system to make the converter similar to the synchronous generator in external operating characteristic. A mathematical model of VSG was established to analyze the dynamic response of both inertial parameter and damping parameter. Based on Opal-RT real-time simulation, a five-terminal MMC-MTDC system was constructed to verify the correctness and effectiveness of the proposed control strategy. Simulation results show that when the power in AC/DC system fluctuates, the proposed control strategy can effectively suppress the frequency fluctuation in AC power grid without the aid of complex communication system, so it is proved that this control strategy can effectively provide inertial and damping to the system and enhance the frequency stability of AC power grid.
Electricity Market
Reliability Analysis of Uncertain Incentive Demand Response Distribution Network
FAN Hong, DENG Jian
2020, 37(4):  416-424.  doi:10.19725/j.cnki.1007-2322.2020.0175
Abstract ( 42 )   PDF (1074KB) ( 10 )  
Alone with the participating of incentive demand response into power grid operation gradually, it plays significant role in improving load distribution and takes an important part in raising the reliability of distribution network. Based on the features of existing incentive demand response and according to the principles of consumer psychology, the non-schedulable response model for interruptible load and emergency demand response, and the schedulable model for direct load control, were respectively established. On the basis of different time scales and by means of fuzzy C-means clustering algorithm the incentive demand response resources were classified, and on this basis the response features such as the response capabilities and uncertainties of non-schedulable and schedulable resources under different time scales were considered, and then a flexibly configurable two stage response scheduling model with the participation of incentive demand response was established. At last, the reliability calculation for an improved RBTS system was performed by use of sequential Monte Carlo simulation. The effectiveness of the proposed method is verified by simulation results.
Multi-source Micro-grid Operation Optimization Considering Uncertain Electricity Price Demand Response
GAO Jia, XIAO Yingqun, MA Rui, ZHANG Jinqian
2020, 37(4):  425-432.  doi:10.19725/j.cnki.1007-2322.2019.0412
Abstract ( 41 )   PDF (1000KB) ( 24 )  
To improve the economic operation level at both supply and demand sides of microgrid, the influences of price elastic coefficient uncertainty on the cost at the both sides was analyzed. Firstly, at the demand side of microgrid, a demand-response cost-effectiveness model, in which the uncertainty of price elastic coefficient was taken into account, was established. Secondly, at the supply side of microgrid, taking economic operation cost and environment cost as optimal objectives and combining with practical operational constraints in microgrid, an economic operation optimization model of microgrid, in which the uncertain price demand response was taken into account, was established, and then a new hybrid difference particle swarm optimization was proposed as the solving method for the established optimization model, in which the benchmark functions was utilized to conduct the contrastive test to verify the effectiveness and reliability of the improved algorithm. Simulation results show that the demand response cost of microgrid increases while the price elastic uncertain factor is taken into account, besides, the operation benefit at the supply side of microgrid decreases to some extent while the uncertain factors are added.
Optimization Model of Bi-level Economic Operation of Microgrid in Electricity Market Environment
XIE Jingdong, LU Wenqi, LṺ Zhiwei
2020, 37(4):  433-440.  doi:10.19725/j.cnki.1007-2322.2020.0102
Abstract ( 38 )   PDF (989KB) ( 22 )  
Along with rapid development of clean energy and relying on its flexible and efficient integration capability for distributed generation, the microgrid has become an important development direction of smart power grid. In the environment of electricity market, it is extremely important that how microgrid can well coordinate and optimize its internal and external resources to gain maximized economic benefit for its existence and development. To effectively promote economic and optimized operation of microgrid under the condition of electricity market, a bi-level economic dispatching optimization model for microgrid was proposed. In the upper level of the proposed model, following items such as making the microgrid participate the competition in the selling side of electricity market and the ancillary service market, drawing up the market trading plan for microgrid, optimizing the operation income of microgrid and so on were considered; in the lower level of the proposed model following items were considered: the optimized scheduling of distributed generations within the microgrid, coordinating the optimal allocation of various internal resources to make the total operation cost the lowest. It is verified by analysis results of computation example that by means of establishing bi-level optimization the microgrid can obtain better economic benefit under the competition environment of electricity market.
Information

  • Bimonthly,Founded in 1984
    Competent Authorities:Ministry of Education
    Sponsor:North China Electric Power University
    Editor-in-chief:Song yonghua
    CN 11-3818/TM
    ISSN 1007-2322
    Postal code:82-640
    Address:North China Electric Power University Beijing 102206,China
    http://xddl.ncepu.edu.cn
    Email:xddl@vip.163.com