Primary frequency control with BESS considering adaptive SoC recovery

Abstract

In this article, a control method which combines adaptive droop control with adaptive state of charge (SoC) recovery control is proposed for battery energy storage system (BESS) to participate in primary frequency regulation (PFR), aiming to improve the system frequency dynamics and contribute to the long-term performance of BESS during PFR. Firstly, based on the frequency operation characteristics of power grid and the economic operation requirements of BESS, an adaptive droop control function of BESS participating in PFR is constructed. Secondly, the recovery power of BESS is determined by regarding SoC as feedback signal. Then, according to the frequency signal of power grid with the operation characteristics of conventional generator units (CGUs), the limiting coefficient of recovery power for BESS is designed. Furthermore, based on the recovery power and the recovery power limit coefficient, the adaptive recovery power of BESS is obtained, which avoids the negative impact of BESS on the operation of CGUs when restoring SoC. Finally, according to the adaptive droop control of BESS with the adaptive SoC recovery control, a comprehensive control method is designed to maintain the proper SoC during the whole operation of BESS, which indirectly reduces the frequency adjustment burden of CGUs. The performance of the proposed method is validated through case studies under conditions of various power variation.