Table of Content

28 December 2022, Volume 55 Issue 12

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Research on Optimal Configuration of Offshore Wind Power Energy Storage Based on Improved Scene Clustering Algorithm

YI Jingui, ZHU Ziwei, XIE Qing

2022, 55(12):  2-10.  DOI: 10.11930/j.issn.1004-9649.202201065

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As demands on smoothing the output fluctuation of offshore wind power increase, this paper proposes an optimal configuration method for offshore wind power storage. The wavelet packet decomposition algorithm is used to process the output curve of the wind power, and an annual power response curve of the power storage system is obtained. In addition, the paper adopts an improved scene clustering algorithm combining a cloud model with a fuzzy c-means clustering algorithm to aggregate the annual power response curve and generate typical scenes of the power response. Furthermore, to minimize the annual comprehensive cost of the power storage, the paper constructs an optimal configuration model for offshore wind power storage and uses the particle swarm optimization algorithm to solve the optimal configuration model. Finally, the proposed method and model are analyzed and verified by typical examples. The results show that the proposed model and method can comprehensively consider the actual operating characteristics of the power storage system on the side of offshore wind farms and effectively guide the power storage configuration and construction planning of offshore wind farms.

Joint Configuration and Optimization of Multi-microgrid Shared Energy Storage Based on Coalition Game

JIANG Congwei, OU Qinghe, WU Zhongchao, ZHANG Jian, YANG Shu, ZHU Jianan, AI Qian

2022, 55(12):  11-21.  DOI: 10.11930/j.issn.1004-9649.202204050

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In the context of achieving carbon peak and carbon neutrality, it is urgent to fully dispatch flexible resources in new power systems. At the same time, the concept of shared energy storage replaces traditional economic operation modes of energy storage and has revolutionary significance for improving the operation efficiency of energy storage. Considering that the capacity configuration and operation optimization of energy storage equipment are coupled, this paper adopts an energy cell–organization framework, proposes a two-stage multi-objective optimal configuration scheme of the shared energy storage based on a coalition game, and fairly allocates the coalition cooperation costs by using the Shapley method. Firstly, a multi-objective total energy storage configuration model is established, with equipment investment, power fluctuations, and electricity selling and purchase prices considered. Based on the NSGA2 algorithm, the Pareto frontier of the coalition’s overall energy storage planning is obtained. Then, with the principle of minimum interaction power between cells, the internal energy storage capacity and power configuration of each cell are calculated, respectively. By comparing the benefits of coalition cooperation with the cooperation benefits divided by participant groups, the paper determines the stability of the energy cell coalition and allocates the cost and interest of each energy cell according to the Shapley method. Finally, the effectiveness of the proposed method is verified by the comparative analysis of different cooperation schemes in the game cases of three energy cells that involve residential, commercial, and industrial aspects.

Optimal Configuration of Hybrid Energy Storage Capacity for Wind Farms Considering Carbon Trading Revenue

CHEN Chongde, GUO Qiang, SONG Ziqiu, HU Yang

2022, 55(12):  22-33.  DOI: 10.11930/j.issn.1004-9649.202204093

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The output power of wind farms fluctuates strongly, and direct grid connection will affect the safe and stable operation of the power system. Therefore, it is necessary to optimize energy storage configuration to smooth the wind power, so as to meet the requirements of grid connection. In order to deal with the large energy storage capacity caused by poor tracking of the moving average method, a hierarchical moving average method was proposed to determine the target in smoothing wind power. The wind power offset was decomposed by a Butterworth low-pass filter, and the low-frequency and high-frequency components were used as the reference power of lithium battery energy storage and flywheel energy storage, respectively. In view of the cost of initial investment and replacement of energy storage as well as the revenue from electricity sales and carbon trading, an optimal configuration model of hybrid energy storage capacity for wind farms was established and solved by an adaptive chaotic particle swarm optimization algorithm. Simulation and verification were carried out according to the operation data of a 48MW wind farm. The simulation results show that the hierarchical moving average method is more suitable for determining the target in smoothing wind power, and the hybrid energy storage of lithium battery and flywheel can improve the net income of the energy storage system of wind farms in the whole life cycle.

Open-Circuit Fault Diagnosis Method of Energy Storage Converter Based on MFCC Feature Set

YU Bin, SONG Xingrong, ZHOU Ting, LUO Linbo, LI Hui, CHE Liang

2022, 55(12):  34-42.  DOI: 10.11930/j.issn.1004-9649.202205007

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Power conversion system (PCS) fault diagnosis plays an important role in the intelligent operation and maintenance of battery energy storage power stations. Considering the difficulties in signal feature extraction, data dimension explosion, and instability of threshold determination interval in the non-invasive identification of IGBT open-circuit fault in PCS by the existing methods, this paper proposes an open-circuit fault diagnosis method of energy storage converter based on Mel-scale frequency cepstral coefficients (MFCC) feature set, so as to support the normal operation and maintenance of PCS. Firstly, the three-phase current on the alternating current (AC) side is taken as the input signal, and an MFCC fault feature data set is constructed by analyzing the signal spectrum energy distribution and envelope characteristics in different frequency intervals. Then, through kernel principal component analysis (KPCA), the dimension reduction screening of nonlinear fault features under charge and discharge conditions is realized. Secondly, a fault state diagnosis model based on the Bayesian optimization algorithm (BOA) and one-dimensional convolutional neural network (CNN-1D) is constructed with a low-dimensional fault feature set as an input. Finally, through the fault simulation experiment of a grid-connected energy storage converter, the proposed method is compared with existing methods, and the results show that the proposed method has better robustness and accuracy in complex noise environments.

Frequency-Voltage Digital Intelligent Control Strategy of Microgrid with User-Side Energy Storage Based on Deep Q-Learning

LIN Rihui, CHEN Youli

2022, 55(12):  43-50.  DOI: 10.11930/j.issn.1004-9649.202207086

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Frequency and voltage are important criteria for measuring energy indicators. Considering the problem of frequency/voltage regulation caused by load fluctuations in microgrids, a smart monitoring-control strategy for microgrids with user-side energy storage based on deep Q-learning (DQN) is proposed in this paper. Firstly, in view of the randomness of user behavior, the random constraints on the output of energy storage on the user side are added, and a four-quadrant charging and discharging model is introduced to build a charging and discharging model for user-side energy storage. On this basis, a cooperative control model of frequency and voltage in the microgrid is built. Secondly, the frequency/voltage controller structure and digital intelligent control platform based on DQN are designed. With the real-time frequency deviation and voltage deviation of the system and the upper and lower limit constraints of the output power of user-side energy storage as the state space and the output of each unit in the system as the action space, a global reward function including two local rewards is designed on the basis of the two control objectives of frequency and voltage. The results of the calculation examples indicate that compared with the traditional PID controller, the DQN controller proposed in this paper can simultaneously meet the control requirements of frequency and voltage and can more effectively deal with the power quality problems caused by load fluctuations.

Design and Operation of Grid-Connected Photovoltaic Energy Storage Power Station in Frigid Plateau Region

ZHAO Bin, LIANG Gao, JIANG Menghao, WANG Li, KONG Qin, WANG Bingqiang

2022, 55(12):  51-60.  DOI: 10.11930/j.issn.1004-9649.202207060

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Tibet is located in a frigid plateau region, and its solar energy resources are extremely rich. Photovoltaic energy storage power stations are conducive to improving the local power structure. However, the severe environment of the frigid plateau region has a significant influence on photovoltaic energy storage equipment. The structure of the Tibet power grid and solar energy resources in Shigatse were analyzed in this paper, and the feasibility of building photovoltaic energy storage power stations was evaluated. Taking Langming Sangzhuzi 50 MW grid-connected photovoltaic energy storage power station as an example, the paper proposed the design scheme of photovoltaic energy storage power stations suitable for frigid plateau regions. The energy storage capacity was set with the objective of minimizing the curtailment of the photovoltaic energy storage power station. The design scheme was verified by the operation data of the power station. The results showed that the scheme is applicable in frigid plateau regions, and an energy storage system with a capacity of 12.5 MW/100 MW·h matches the 50 MW photovoltaic system well, which can reduce about 60 MW·h abandoned power per day. The research can provide guidance for the optimization design of grid-connected photovoltaic energy storage power stations in frigid plateau regions.

Short-Term Wind Power Prediction Based on Variational Modal Decomposition and Quantile Convolution-Recurrent Neural Network

SHA Jun, XU Yusen, LIU Chongchong, FENG Dingdong, XU Zheng, ZANG Haixiang

2022, 55(12):  61-68.  DOI: 10.11930/j.issn.1004-9649.202106030

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Due to the randomness and intermittency of wind power, wind power forecasting requires not only accurate point forecasting, but also reliable interval and probabilistic forecasting to quantify the uncertainty of wind power. This paper proposes a probabilistic wind power forecasting method based on variational mode decomposition (VMD) and quantile convolution-recurrent neural network. Firstly, this method uses VMD to decompose the original wind power sequence into a series of modal components with different characteristics. Secondly, the convolutional neural network (CNN) is used to extract high-order features reflecting the dynamic changes of each modal component. Then, the quantile regression is performed by the long short-term memory (LSTM) recurrent neural network based on the high-order features to obtain the predicted values for different quantiles. Finally, the kernel density estimation (KDE) is employed to estimate the probability density curve of wind power. The effectiveness of the proposed method is verified with the example test using datasets from the wind farm in China.

Wide-Area Damping Cooperative Control Method of Low-Frequency Oscillations of Power Systems with Photovoltaic Stations

SHEN Tugang, WU Zhenghua, WANG Sijia, WU Xiangyu

2022, 55(12):  69-77.  DOI: 10.11930/j.issn.1004-9649.202112114

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The grid integration of largescale new energy increases the risks of weakly damping oscillations. Considering the dynamics of synchronous generators and photovoltaic generations, this paper establishes a detailed small-signal model and analyzes the impact of photovoltaic generations on low-frequency oscillation modes. A wide-area damping control structure of low-frequency oscillations is proposed for power systems containing photovoltaic generations, so that photovoltaic generations and synchronous generators can dampen low-frequency oscillations. Based on the results of eigenvalue analysis, an optimization model of wide-area damping control parameters is proposed further Finally, the electromagnetic transient simulation model of four-generator and two-area system with photovoltaic station is built on the PSCAD/EMTDC platform. The time domain simulation results verify the effectiveness of this wide-area damping control method.

Massive Scenario Reduction Based Distribution-Level Power System Planning Considering the Coordination of Source, Network, Load and Storage

LIU Jinsen, LUO Ning, WANG Jie, XU Chang, Cao Yi, Liu Zhiwen

2022, 55(12):  78-85.  DOI: 10.11930/j.issn.1004-9649.202208020

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The integration of high-proportion renewable power generation has brought great challenges to the efficiency of distribution network planning methods and the economy of planning results. In order to solve the problem of coordination between the massive operation data of renewable power generation and the coordinated planning of the source-network-load-storage, this paper proposes a coordinated planning method of the source-network-load-storage based on the massive scenario dimension reduction. Firstly, the dimensionality reduction clustering is carried out on the wind-light-load mass high-dimensional scenarios by the principal component Gaussian mixture clustering algorithm, and the typical scenario set of wind and power loads is obtained; then, a source-network-load-storage coordination planning model of distribution network for massive scenarios is constructed, and the second-order cone relaxation technique is adopted to convert the non-convex constraints to convex ones; finally, the effectiveness of the proposed massive scenario dimension reduction clustering method and distribution network planning model is verified on the Portugal 54-node distribution network.

The Optimal Allocation Strategy of Pumped Storage for the Collaborative Operation with Wind/Solar Generation

SANG Linwei, WEI Xuan, XU Yinliang, SUN Hongbin

2022, 55(12):  86-90,123.  DOI: 10.11930/j.issn.1004-9649.202107006

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Cross-regional transmission of large-scale renewable power generation is an inevitable requirement to deal with the reverse distribution characteristics of domestic wind/solar resources and load centers as well as to achieve carbon neutrality. However, the inherent randomness, intermittence, and volatility of wind/solar generation bring challenges to the transmission and accommodation of renewable power generation. Hydropower, which could serve as both the power source and energy storage, provides a solution for calming the fluctuation of renewable power generation, so as to improve the flexibility of wind-photovoltaic(PV)-hydropower hybrid energy system. Based on the wind-PV-pumped storage hybrid energy system, this paper proposes a capacity allocation method to quantify the effect of pumped storage on renewable power generation delivery, where the operation constraints, capacity constraints, water inflow/outflow constraints are considered. The planning model of minimizing the investment cost of pumped storage and meeting the requirements of each typical operating scenario is constructed and solved.

A Distribution Network Expansion Project Classification Model Based on Data Augmentation and Dimensionality Reduction Method

ZHOU Xin, LIN Jingxing, XIE Zhiwei, ZHANG Zheng, LIANG Ruduo, OU Zuhong

2022, 55(12):  91-97.  DOI: 10.11930/j.issn.1004-9649.202204098

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Distribution network expansion project is of great significance for power supply enterprises to carry out power supply work. Aiming at the low efficiency of the process operation of distribution network business expansion project, a classification method of distribution network business expansion project based on data enhancement and data dimension reduction technology is proposed. This method enhances the original data, reduces the data dimension through depth self encoder, and performs feature extraction and clustering analysis. Based on the data of a distribution network expansion project of a power supply bureau, the simulation results show that the classification accuracy of the algorithm used in this paper is better than other algorithms. The proposed method can reasonably allocate the duration of the industrial expansion project, realize the differential management of the distribution network industrial expansion project, and improve the process operation efficiency and customer satisfaction.

Discussion on Multi-Status Monitoring Technology of Prefabricated Substation

FAN Changjun, MENG Fei, GUO Tianheng, DU Yankun, CUI Xiaolin, ZHANG Cheng

2022, 55(12):  98-104.  DOI: 10.11930/j.issn.1004-9649.202203037

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Centralized access of prefabricated cabin substation has gradually become the development trend of urban power distribution system. Based on the SF₆ gas concentration, temperature and humidity, noise, pollution and other factors in the prefabricated cabin substation, an integrated status monitoring system is built, and a forced fan strategy is proposed based on the fan configuration in the prefabricated cabin to adjust the cabin environment and reduce the operation and maintenance of the substation. The proposed method takes into account the comprehensive influence of multiple environmental factors, solves the problem of fan start and stop confusion in prefabricated cabin substations, and improves the reliability and sensitivity of environmental control in prefabricated cabin substations.

Economic Scheduling of Electric-Heat-Water Multi-Energy Coupling Systems Considering Electric Vehicles and Demand Response

GUO Mingxing, LV Ran, FEI Fei, CHEN Tao

2022, 55(12):  105-111.  DOI: 10.11930/j.issn.1004-9649.202109117

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In the context of the increasing installed capacity of combined water and power units (CWP), this paper pro-poses an economic scheduling method for the electricity-heat-water integrated energy system, considering the charging and discharging strategy of electric vehicles and the demand response management strategy. First, the basic structure of the electricity-heat-water integrated energy system is construct, and the coupling mechanism between the systems is analyze. Then, with the goal of minimizing the total fuel cost of power generation, heat generation, and seawater desalination during the scheduling process, the economic scheduling method considering the behavior of electric vehicles and demand response management strategy is established. Finally, a simulation example is used to verify the proposed method, and the results show that the proposed method is conducive to realizing the low carbon economy operation of the system.

Space Charge Behavior and Mechanism of Polyimide Under Pulse Voltage

HOU Jianjian, WANG Chanjuan, GUO Haoxin, CHEN Chen, LIU Xuemin, HE Dongxin

2022, 55(12):  112-123.  DOI: 10.11930/j.issn.1004-9649.202209119

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The insulation of power electronic equipment is more likely to deteriorate and fail early because it is operated with high repetition rate and steep rise time pulse voltage for a long time. In order to explore the microscopic mechanism of insulation failure under pulse voltage, the space charge distribution before and after the pulse edge at the nanosecond level was studied and compared, and the influences of electric field strength and silicone oil on the charge vibration waveform at the pulse edge were explored. Based on an analysis of the spectrum of charge vibration waveform and voltage waveform and the charge accumulation characteristics at different pulse rise times, the charge vibration mechanism at the time of pulse voltage edge and the influence mechanism of charge behavior on insulation degradation under nanosecond pulse were expounded. It was found that the charge distribution characteristics before and after the rising edge and falling edge of the nanosecond pulse were different, and a special space charge migration behavior was found at the pulse edge; the electric field strength would affect the accumulation speed and amount of the heteropolar charge, thereby affecting the shape of charge vibration waveform; the application of silicone oil between the electrode and the sample would affect the polarity of the charge vibration waveform; the voltage component in the 5×10⁶~1×10⁷ Hz frequency band played a major role in the space charge vibration; the charge accumulation under the nanosecond pulse voltage caused serious electric field distortion.

Study on the Threshold for Deformation Rate of Transmission Tower Foundation in Goaf Subsidence Area

YU Hong, LI Hao, KANG Biao, WANG Dahai, ZHANG Zhiqiang, ZHANG Guifeng, ZHANG Haipeng

2022, 55(12):  124-134.  DOI: 10.11930/j.issn.1004-9649.202209080

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Goaf subsidence will cause such deformations as sliding and settlement of the transmission tower foundations, and even cause tower collapse in serious cases. This paper analyzes the tower inclination and foundation deformation rate of a 500 kV line under different foundation deformation conditions in order to study the deformation and failure characteristics of transmission towers in goaf subsidence area. The results show that compared with the tower inclination, the foundation deformation rate can better indicate the status of transmission towers in goaf area; the threshold of the tower foundation deformation rate is 0.5% under the uneven settlement condition, and 1.0% and 2.0% for slight tower damage and serious tower damage respectively under the relative horizontal deformation. The research results of this paper can provide an important reference for the bearing capacity design and the monitoring and evaluation of the tower safety status in the goaf area.

An Optimal Planning Method for Park IES Considering Life Cycle Carbon Cost

FANG Rengcun, YANG Jie, ZHOU Kui, HUANG Tao, LV Fengbo

2022, 55(12):  135-146.  DOI: 10.11930/j.issn.1004-9649.202106002

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Integrated energy system (IES) is one of the effective ways to achieve the “dual carbon” goal, and its planning, construction and operation need to take into account economic costs and low-carbon benefits. In order to comprehensively evaluate the comprehensive IES benefits, a planning method is proposed that incorporates the carbon emission cost of energy and equipment in the life cycle process of manufacturing, transportation, operation into the optimization goal. A hourly simulation and optimization is carried out for a park IES, and an analysis is made on the influence of different carbon cost scenarios on the IES optimal configuration and operation schemes. The proposed method can provide a reference for IES design and planning.

High Quality Power Supply Service Mode Considering Service Life of Mitigation Equipment Against Voltage Sag

LI Pei, YU Yongjun, MA Zhiquan, CAI Chongkai

2022, 55(12):  147-159.  DOI: 10.11930/j.issn.1004-9649.202110029

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The voltage sag mitigation equipment has such problems as large one-time investment cost and high investment threshold, which urgently need to be solved through a new high quality power supply service mode. Therefore, a high quality power supply mode considering the service life of mitigation equipment against voltage sag (HPSL) is proposed. Firstly, a HPSL operation mode is proposed and the operation entities and service process of HPSL are defined. And it is proposed that the old equipment shall participate in the mitigation management if they can meet the user's needs. Secondly, a HPSL service pricing optimization model is established with a comprehensive consideration of the cost and income composition of equipment manufacturers and users, and with the maximum net income of both parties as objective. Furthermore, a service fee game model is established based on the Stackelberg game. The model takes the adjustment of additional income coefficient by equipment manufacturers as the decision-making, and the adjustment of service duration by users as the response, which is in line with the actual situation. The improved genetic algorithm is used to solve the model. Finally, a case study is conducted by taking a large film factory as an example. It is proved that the proposed mode can reduce the governance cost of users, and improve the service fee income of equipment manufacturers.

MMC Coordinated Control Strategy for Maximum Power Output Under Asymmetric Voltage Sag

HE Yedan, XIA Xiangyang, YIN Xu, DENG Wenhua, WANG Can, XIONG Fuqiang, ZHOU Hanliang

2022, 55(12):  160-167.  DOI: 10.11930/j.issn.1004-9649.202206102

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Aiming at the problems of asymmetric voltage sag on the AC side of flexible DC transmission system, such as the power fluctuation and three-phase current imbalance during the operation of modular multilevel converter (MMC), a MMC coordinated control strategy for maximum power output under asymmetric voltage sag is proposed in this paper. Taking the coordinated control of suppressing the fluctuation of active power and outputting the three-phase balance current as objective, a linear weighted analytical formula is constructed to determine the regulation parameters according to the variation law of the operation characteristics of MMC system with the regulation parameters under asymmetric voltage sag, and then the maximum active power is outputted while ensuring that the outputted peak current of MMC system is within the maximum allowable working range; The proposed strategy not only expands the active power output capacity, but also improves the overall control and protection performance of the system. Finally, the effectiveness of the proposed method is verified through simulation and experiment.

Analysis of Distributed Green Power Transaction Optimization Based on Nash Bargaining Theory

ZHANG Yan, QIAO Songbo, XU Qifeng, YU Jing

2022, 55(12):  168-178.  DOI: 10.11930/j.issn.1004-9649.202209094

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In order to promote the market-oriented consumption of distributed green power and improve the operation efficiency of distributed green power units, this paper studies the cooperative trading mode of distributed power generation operators, energy storage operators and flexible load aggregators that aggregate distributed green power by using virtual power plant joint technology. Firstly, the optimal operation model of each subject is established under the premise of energy transaction between each subject, and then the multi-agent cooperative game model is established based on Nash bargaining theory. In order to better solve the cooperative game model, the model is transformed into a sub-problem of maximizing the total benefit of cooperative operation and a sub-problem of asymmetric income distribution. The alternating direction multiplier method is used to solve the two sub-problems in a distributed manner. Finally, the effectiveness of the proposed model is further verified by simulation. The conclusion shows that participating in power cooperative trading can effectively improve the operating efficiency of distributed green power units.

Research and Its Application of Evaluation Model for Comprehensive Performances in Trans-Province Power Trading

DAI Shuangfeng, YE Ze, JIANG Man, WANG Yali, WU Yongfei

2022, 55(12):  179-186.  DOI: 10.11930/j.issn.1004-9649.202012129

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This paper analyzes the influencing factors of the comprehensive benefits in cross-provincial power trading, constructs the measurement model and finally completes the calculation of the comprehensive benefits, which provides direction guidance for cross-provincial power trading. The results show that in the cross-provincial power trading, the comprehensive benefit depends on the arrangement of the transaction direction, multi-type power trading is significantly better than the coal-fired power trading, and the hydro-power trading have the best comprehensive benefits, which are obviously better than the thermal power transactions.