DC-side Voltage Limiter for Grid-Forming Converters with Energy Storage

This paper describes a method to limit the DC-side voltage of the Grid Forming (GFM) converters with energy storage, such as the Energy-Storage Static Synchronous Compensator (E-STATCOM) and Battery Energy Storage System (BESS). First, the system model and converter topology are presented. Next, the studied GFM control method is shown, along with its basic control blocks, for an E-STATCOM study case. Later, the proposed DC-side voltage limiter based on Variable Virtual Inertia (VVI) and its working principles are described. It is shown that using such a limiter, when the DC-side voltage reaches its limits, which are related to State of Charge (SoC) limits, the active power contribution will gradually decrease to zero. At the same time, the converter can continue to contribute and respond to system changes with its reactive power capabilities. Finally, the performance of the proposed limiter is validated with time-domain simulations for various scenarios.