Secondary frequency regulation of thermal power units assisted by energy storage systems has the advantages of fast response speed and high tracking accuracy.However,improper power allocation can accelerate battery life degradation,resulting in increased operat-ing cost and reduced economic benefit.Therefore,how to formulate a reasonable energy storage power allocation strategy to ensure frequen-cy regulation performance while extending battery life and improving economic benefits has become a key issue that needs to be solved ur-gently.A mathematical model of energy storage lithium battery based on the second-order RC equivalent circuit was established firstly,and the limited memory least squares recursive algorithm to identify the model parameters was then employed.Subsequently,three power alloca-tion strategies such as proportion,difference and frequency were simulated and analyzed based on the joint frequency regulation model of thermal storage.Finally,with the actual operational data from a 660 MW thermal power unit in Jiangsu,the effects of different strategies on system frequency regulation performance,battery life and economy were analyzed.The obtained results indicate that the proportion alloca-tion strategy has the worst frequency regulation effect and accelerates the battery life decay.The difference allocation strategy performs well in frequency regulation performance but has limited effect on improving battery life.The frequency allocation strategy can effectively reduce the battery replacement frequency and thus improve the overall economic benefit.Generally,the frequency allocation strategy can not only improve the frequency regulation capability,but also maximize the battery life with optimized economic benefit,demonstrating significant application advantages in the secondary frequency regulation assisted by the energy storage systems.
energy storage systemsecondary frequency regulationpower allocationbattery lifepower unitoperation optimization