Research On SOC And SOH Estimation Algorithms Of VRLA Battery Used In Substation

VRLA battery, which known as the maintenance-free battery, isan important part of substation DC power supply system. It's responsible forproviding power protection for the secondary power system load, in order to ensure the normal operation of the relay protection, communication equipment and so on. Substation batteries are often used in series.Defective batteries happenedto exist would cause a serious decrease in the capacity of the whole group batteries.If this phenomenon continued for a long time,the reliability of the whole group batterieswould bereduced severelyand thedefective batteries mightacceleratthe aging of the whole groupcells,which calls the "barrel effect". Therefore, in order to ensure the safe operation of the power equipment, the state of health (SOH)of each battery and its real state of charge (SOC) must be real-time monitored in the substation operation.Firstly, this paper analysised the history data of more than 50 substation power grids5-years nearby and then summarized the multiple factors related to battery SOC estimation.Then this paper tested some specific type VRLA batteries under the laboratory conditions in different temperature and different experimental conditions. Then we got the extraction of VRLA battery typical OCV-SOC curve, drew lessons from domestic and foreign common VRLA battery equivalent model and the SOC estimation model.This paper combined substation battery group for a long time in floating state and general two years before a full capacity check discharge of the actual working conditions and working environment, selectedthefive-order OCV-SOC model and introduced temperature, cycles and other parameters to modify the battery capacity. The paper used the Extended Kalman filter (EKF) algorithm to estimate the battery state of charge (SOC), and constructed the model of experimental data simulation to analysis, and finally verified the rationality of the algorithm of SOC. Then the paper focused research on the relationship between the key of VRLA battery SOH and battery temperature, SOC, internal resistance, voltage parametersand then establishedthe battery body parameters-battery operation and maintenance working life model. The paper did tests under the laboratory conditions for high temperature float accelerated aging experiment, and adopt the multi-factor comprehensive analysis. Finally, the paper established oriented substation with actual conditions of VRLA battery aging model and SOH estimation algorithm, then introduced the whole process of algorithm realization and verification processin detail.This paper studied the LiShi DJ100 and DJ300 type of VRLA batteries and did some test in laboratory with constant temperature and humidity cabinet for a series of different temperature and different conditions of charge and discharge experiments.According to the experimental data, the OCV-SOC mathematical model formula of parameter identification and battery capacity compensation coefficient parameter identification, and then simulated in Matlab/Simulink. The results show that the method can obtain higher SOC estimation accuracy. Finally, the accuracy of the SOH algorithm and the forecast model is verified by the battery on-line monitoring management system.