Table of Content

30 September 2023, Volume 0 Issue 9

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Research & Analysis

Impact Assessment and Adaptive Protection Strategy of Energy Storage Access into Distribution Network

ZHU Liwei, FU Xiangyun, NIU Meng, QU Zhanzhan, GUANG Hongwei, SONG Jiakang, YUE Fuchang

2023, 0(9):  1-10.  doi:10.16628/j.cnki.2095-8188.2023.09.001

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With the increasing of new energy in the power system year by year,energy storage has become an increasingly important flexible regulatory resource.Energy storage systems are generally connected to the power grid through power electronic devices,while frequent charging and discharging may have an impact on the power flow and protection of the grid.By analyzing the source load characteristics of electrochemical energy storage,considering the different operating states and power exchange situations of energy storage as a power source and a load.based on a typical distribution network architecture,the power flow changes at different locations of faults are studied.The impact of energy storage connected to the distribution network on traditional protection is evaluated,and the adaptive current protection schemes and specific protection measures are proposed.Finally,the effectiveness of the adaptive current protection scheme is verified by simulation.

Large-Scale Energy Storage Assisted Transient Voltage Stability Control Model and Application of Power Grid

ZHU Chen, ZHENG Junfeng, FANG Xing, FU Xiang, CHEN Baiyuan, GAO Kefu, HU Xiangwei, HUANG Jiyuan

2023, 0(9):  11-17.  doi:10.16628/j.cnki.2095-8188.2023.09.002

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In order to effectively solve the problem that the UHV DC bipolar lock and the randomness of new energy output may lead to a decrease of the transient stability level of the main network and the reliability of the distribution network power supply.Firstly,based on the power system analysis software package (PSASP),a user defined module is used to model the energy storage system to improve the transient voltage stability control of power grid.Secondly,a joint voltage regulation control strategy for energy storage power station and capacitor/reactor is proposed to effectively improve the voltage regulation capability of the system.Finally,the results show that compared with the condenser the voltage recovery speed of energy storage with equal capacity connected at the same location is faster.The power grid transient voltage regulation level is effectively improved.

Neutral Point Voltage Balance Control of Type-I Three-Level PCS

ZHANG Xiaojie, MAO Xingkui, ZHENG Jiadong, ZHANG Zhe, DONG Jiqing

2023, 0(9):  18-23.  doi:10.16628/j.cnki.2095-8188.2023.09.003

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In response to the inherent neutral point voltage imbalance problem in type-I three-level power conversion system (PCS),the principle of neutral point voltage imbalance is analyzed based on space vector modulation,and a hybrid modulation strategy is proposed combining seven segment space vector pulse width modulation (SVPWM) with five segment SVPWM.When the neutral point voltage offset is large,the seven segment SVPWM with balance factor is used to quickly adjust the neutral point voltage.When the neutral point voltage offset is small,the five segment SVPWM without switching at high current is adopted to effectively reduce the switching times of the switch and reduce the loss.A 12 kW PCS prototype is built.The experiments show that compared with the traditional seven segment SVPWM,the neutral point voltage offset and fluctuation of the hybrid modulation strategy is reduced,and the efficiency of the prototype is improved by about 0.3%.The correctness and effectiveness of the proposed hybrid modulation strategy are verified.

Study on Phased Enhanced Heat Dissipation Performance of Ordered Porous Structure of Charging Pile Power Module

HAN Ying, ZhANG Huaiyuan, JIA Aobo, HOU Chunguang

2023, 0(9):  24-31.  doi:10.16628/j.cnki.2095-8188.2023.09.004

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Taking the heat dissipation device of the DC charging pile EVR700-15000 power module as the research object,the ordered porous structure is adopted to enhance the heat dissipation of the power module.The thermal simulation model of porous channel is established to study the influence of vortex generator on enhanced heat transfer in different flow stages,and the influence of the placement and number of vortex generators on the heat dissipation performance of porous structure is studied.The heat dissipation effect of ordered porous structure before and after adding passive enhanced heat transfer is compared and analyzed.The results show that the heat transfer performance of the vortex generator in the development stage of the fluid is better than that in the fully developed stage.Adding an ordered porous structure with passive enhanced heat transfer can effectively reduce the operating temperature of the power module and improve the stability of the charging pile.

Optimal Configuration of Customer Energy Storage Based on Power Big Data

WANG Limeng, QU Yang, LIU Yutu, YANG Ranran

2023, 0(9):  32-38.  doi:10.16628/j.cnki.2095-8188.2023.09.005

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Taking regional power users as the research object,the analysis of energy storage investment potentiality is carried out.The objective function is established based on the highest life-cycle return and the fastest cost recovery of the user’s investment in energy storage.Based on the big data of electric power,the suitable users for energy storage investment are identified and the capacity configuration is calculated.According to the objective constraint function,combined with the current energy storage related parameters and electricity price,the boundary value of profitable user energy storage configuration capacity is obtained.Screening out users with a user capacity greater than the configured capacity is a potential user for developing energy storage configurations.Then,a calculation model for lithium iron phosphate batteries is constructed,and the optimal energy storage investment plan for potential users is obtained by calculating the capacity,duration,and benefits of adjustable resources for potential users.The energy storage cost is further reduced and a higher economic efficiency is obtained through the combination of configuring energy storage batteries and time-of-use electricity prices.

Electrical Design & Discussion

DC Power Supply System Based on the Battery Guard Component

ZHAO Qiliang, XIONG Zecheng, YU Yue, YIN Qiang, HUANG Junwei

2023, 0(9):  39-42.  doi:10.16628/j.cnki.2095-8188.2023.09.006

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In response to problem single battery open circuit in traditional series DC power supply to lead to decrease the reliability of the entire battery power supply and require the battery to detach from the bus core capacity.A new DC power supply system based on the battery guard component is proposed.The system improves the reliability of the DC power supply system through battery protection components,and has functions such as online battery capacity verification.According to relevant regulations,a scheme for a 110 kV substation is implemented.The system test results and operating conditions meet the design expectations,which can prove that the proposed scheme has application and promotion value.

Bidirectional PCS Design Based on Silicon Carbide

CHEN Qi, ZHANG Binyi, MAO Xingkui

2023, 0(9):  43-49.  doi:10.16628/j.cnki.2095-8188.2023.09.007

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With the development of bidirectional power conversion system (PCS) towards high voltage and high efficiency,SiC devices are gradually being applied in bidirectional PCS.The PCS main circuit topology of SiC adopts a T-type three-level inverter circuit that can effectively reduce grid connected current harmonics.Aiming at the high switching frequency of SiC devices,the phase-locked control based on phase voltage sampling is more susceptible to interference,and the system stability is easily affected when the power grid is unbalanced,a phase-locked loop based on line voltage sampling and the corresponding positive and negative sequence separation control strategy of grid-connected current are proposed.Finally,a 10 kW bidirectional PCS experimental prototype based on SiC is built,which shows good performance and stable and reliable operation.The experimental results verify the correctness and effectiveness of the design scheme and control strategy.

Non Power Point Energy Storage Power Supply

LÜ Haichao, MENG Fanti, LIU Miaomiao, JIA Tian, NIU Gaoyuan

2023, 0(9):  50-54.  doi:10.16628/j.cnki.2095-8188.2023.09.008

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In order to improve the efficiency of electric engineering vehicles,a non power point energy storage power supply is proposed.The various working modes,charging and recharging processes of non power supply energy storage power supply is analyzed in detail.The testing analysis and verification are conducted.The results show that the proposed device can achieve continuous operation of electric engineering vehicles in construction sites without power sources,and can also serve as an emergency power source to provide emergency electrical energy support for production and daily life on the construction site.

Estimation & Prediction Technology

Research on SOC Estimation of Lithium Battery Based on GRA-MEA-BP Algorithm

XU Shouping, HU Juan, FU Shanshan, CHEN Juan

2023, 0(9):  55-61.  doi:10.16628/j.cnki.2095-8188.2023.09.009

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In view of the nonlinear characteristics of lithium battery state of charge (SOC),the grey relational analysis,mind evolutionary algorithm,back propagation (GRA-MEA-BP) neural network algorithm is proposed,which is used for the SOC estimation of lithium battery at the current moment.Several main impact factors of SOC estimation is selected by GRA.The MEA-BP neural network is trained by taking the main influencing factors as inputs and the current SOC as output.Finally,taking the actual lithium battery as the object the proposed method is trained and verified by real data.The verification results indicate the accuracy of the proposed method.

SOC Estimation of Power Lithium-ion Battery Based on EKF Algorithm

LI Tang, HUANG Kang, MAO Xingkui, ZHANG Zhe

2023, 0(9):  62-68.  doi:10.16628/j.cnki.2095-8188.2023.09.010

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In order to solve the problem of difficult to accurately estimate and predict the state of charge (SOC) of power lithium-ion batteries in new energy vehicles,a second-order RC equivalent circuit model is chosen to model lithium-ion battery firstly.MATLAB/cftool toolbox and the forgetting factor recursive least squares (FFRLS) are used to identify the parameters of the lithium-ion battery model.Secondly,the SOC estimation accuracy is improved by the extended Kalman filter (EKF) algorithm.Finally,the battery management system (BMS) experimental platform is built.The simulations and experiments are conducted under the federal urban driving schedule (FUDS) in the United States.The results show that the FFRLS method can improve the lithium-ion battery model accuracy compared with the parameter identification method fitted by the cftool toolbox,and the SOC estimation accuracy is high and the convergence speed is fast,which can verify the accuracy and effectiveness of the second-order RC equivalent circuit model of lithium-ion batteries combined with the EKF algorithm to estimate the SOC of lithium-ion batteries.

Prediction of Remaining Service Life of Lithium Battery Based on AE-LSTM

CHENG Junhan, WANG Shuli, CAI Zhiyuan

2023, 0(9):  69-75.  doi:10.16628/j.cnki.2095-8188.2023.09.011

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A prediction model based on data fusion and long short term memory network (LSTM) is proposed to address the issue of low prediction accuracy in predicting the remaining service life of lithium batteries,which mostly uses a single decay feature.Spearman correlation coefficient method is used to select the decay features with high correlation from the open source data set of lithium battery in the laboratory of University of Maryland (CALCE) with the capacity ratio as the prediction target.Auto encoder (AE) is used to perform data fusion on the decay features.The remaining service life prediction model of AE-LSTM lithium battery is established and compared with the prediction model of RNN and LSTM.The example shows that the proposed method has high prediction accuracy and can meet the needs of practical engineering.