Power Fluctuation Suppression in Energy Storage for PV-Battery GFM Systems

Grid-forming (GFM) control is increasingly adopted in grid-connected inverters for frequency support, as a promising solution for the large-scale integration of renewable energy resources, like solar photovoltaic (PV). To solve the uncertainty of the PV power and reserve extra energy for frequency support, a battery energy storage system (BESS) is usually adopted. However, in the PV-battery GFM system, as the PV system and the BESS are coupled at the DC bus, any power fluctuation in the PV system will directly influence the BESS, which contributes to a reduction in the lifespan of batteries. The BESS power fluctuation in this process remains unclear. As such, in this paper, the typical control of the PV-battery GFM system is analyzed in order to explore the interaction between the BESS and the PV system. A control strategy is presented to suppress the PV power fluctuation and improve the DC-link voltage dynamic of the BESS. And, the control parameters are designed for the presented control strategy. Experimental tests have demonstrated the effectiveness of the control scheme.

I. Introduction

With the increasing penetration of renewable energy sources (RESs) into the power system, solar photovoltaic (PV), as a typical distributed generation resource, has received consid-erable attention worldwide [1], [2]. However, the wide-side adoption of such power electronics-based systems makes the power system become low-inertia or inertia-less [3]. Grid-forming (GFM) control stands out as a promising solution to address these issues, primarily owing to its strong frequency support capability [4], [5]. Currently, the virtual synchronous generator (VSG) control is one of the most commonly used GFM methods [6], enabling the inverter to mimic the dynamics of a synchronous generator (SG).