Sizing Methodology for Battery Energy Storage Systems Coupled with PV Plants to Ensure Compliance to Grid Codes

Abstract

Photovoltaic (PV) solar energy is a crucial technology to transition from a fossil fuel-based energy mix to a futurewith high shares of renewable energy. To do so, PV plants must be coupled with energy storage systems that can accumulate excess power and dispatch it when PV generation decreases suddenly. This paper proposes a methodology todetermine the battery energy storage system (BESS) energy capacity and power rating that ensures grid code compliance while reducing PV power output variability. The methodology also introduces the steps related to gathering andvalidating PV generation data and the specifications an appropriate model must include. To do this, we use a modelthat considers the degradation of PV modules and two Li–ion battery types (LFP and NMC). The total BESS cost andpossible battery replacements are key factors when defining the system energy capacity (in MWh) and power rating(in MW). To test the methodology, a 20 MWp PV plant is simulated along with the BESS. The results indicate that anLFP–based BESS of 2.5 MWh with a rated power of 1.25 MW ensures a stable output power with variation below 10% of the rated PV plant 98 % of the time. As a result, this paper defines a methodology to guide academics, engineers,and practitioners through sizing a reliable battery storage system.