Performance Evaluation Of Grid-scale Battery Energy Storage System Employing Virtual Synchronous Generator Control For Grid Code Compliance In Weak Grids

This document is on the design and testing of a grid-scale Battery Energy Storage System (BESS) employing Virtual Synchronous Generator (VSG) control grid-forming scheme. The BESS is rated 60 MWh/50 MW. The simulations were conducted using MATLAB/Simulink/Simscape software. The protection functions and the associated protection relays needed to achieve these functionalities are presented. The approach adopted can apply to any relevant standard or grid code associated with a Transmission System Operator (TSO) internationally, however, the local grid codes in the context of South Africa were used. The system is designed to be compliant with the document Grid Connection Code for Battery Energy Storage Facilities (BESF) connected to the Electricity Transmission System (TS) or the Distribution System (DS) in South Africa and is classified under Category C as defined in the same document. The system was able to adjust both its active and reactive power outputs accordingly in response to load reduction conditions in the network. Furthermore, for local fault conditions, it was able to ride-through transient faults and trip and disconnect for permanent faults. For these two cases the BESS protection functionality serves as primary protection. The system was also able to trip and disconnect for remote permanent faults where the associated protection functionality is utilised as back-up protection.