Frequency stability supports from battery storage with virtual synchronous machine control

This paper investigates the dynamic behaviour of large-scale battery energy storge (BES) with virtual synchronous machine (VSM) control to assess its capabilities in providing virtual inertia and fast frequency response (FFR). To do so, a novel VSM BES dynamic model is proposed which includes upper-level plant control, lower-level converter control, back-to-back converter, and battery storage stack models. The plant-level control is responsible to generate VSM BES active-reactive power references in addition to an internal voltage phasor for its synchronization while the converter-level control creates a modulation signal according to the internal voltage phasor. We then study the relationship between grid-code requirements, i.e., response time and damping, and VSM control design and parametrization. We also discuss how a specific control loop (e.g., VSM control, virtual damping control, etc.) dominates the VSM BES active power behaviour during a certain time horizon. This could help understand the VSM BES dynamics in frequency stability analysis while highlighting the importance of each plant/converter-level control loop. Our discussions and simulation case studies demonstrate BES VSM capabilities and dynamic behaviour during virtual inertia/frequency supports, thus contributing to adding further clarity on the VSM control concept.