doi:10.16186/j.cnki.1673-9787.2022110061

Received:2022/11/29

Revised:2023/05/24

Published:2024/05/15

Primary frequency modulation based on retired battery with hierarchical backup and adaptive control

ZHAO Xilin, CHEN Xiao

School of Electrical & Electronic Engineering， Hubei University of Technology， Wuhan 430068， Hubei， China

Abstract:  Objectives  Under the goal of carbon peaking and carbon neutrality，a large number of new energy is connected to the grid，resulting in a decrease in the equivalent inertia of the power system and an increase in the uncertainty of power supply，which has brought challenges to the frequency security of the power grid.In recent years， battery energy storage has received extensive attention in the field of power grid frequency modulation due to its fast response and flexible regulation.Considering the rapid development of new energy vehicles at present， a large number of automotive batteries are being retired. Taking into account the cost associated with battery configuration， how to make full use of retired battery in participating in grid frequency regulation applications under the premise of safe utilization was a research-worthy issue， and this article conducted an in-depth study on this matter.   Methods  Firstly， the AGC model of retired batteries participating in the primary frequency modulation of power grid was constructed， and the influence of the charge and discharge depth of retired batteries on their remaining life was analyzed to determine the SOC threshold range of their operation.Secondly，by designing the proportional coefficient of output， the advantages of virtual inertia and virtual droop were maximized，and the retired battery SOC was used as the switching condition for hierarchical adaptive control.Then，the frequency deviation distribution coefficient was introduced to make another group of retired battery participate in the standby coordination， so as to avoid the frequent switching of charging and discharging states of one group of batteries， which would damage the remaining service life of the battery.   Results  Finally，by constructing a simulation model in MATLAB/Simulink，setting multiple sets of parameters for comparison， the results demonstrated that the rational utilization of retired battery can successfully substitute for new batteries in participating in grid frequency control，which provided effective support for the stability and secure operation of the grid.   Conclusions  Under the proposed approach， retired batteries can effectively reduce the maximum frequency deviation of the grid，avoiding over-limit SOC and secondary frequency drops. At the same time， this approach significantly reduced the number of charge-discharge switchings of retired battery during load fluctuations，which was beneficial for extending the remaining lifespan of the battery.  

Key words:retired battery;state of charge;primary frequency modulation;hierarchical backup;adaptive control