Asymmetric and Confined Operation of a Generic Virtual Synchronous Machine

This article presents and examines a novel approach to modify the active-power behaviour of a generic virtual synchronous machine (VSM) in order to respect DC-side activepower limitations of converter-coupled generation and loads, thereby enabling them to participate in instantaneous reserve without additional storage or hardware reinforcements. A modification to the VSM control is suggested which consists of a DeltaP feedback loop and a dynamic adaptation of the virtual impedance. These mechanisms enable the VSM to have a RoCoF-dependent (Rate of Change of Frequency) acceleration time constant TA ≥ 0 without endangering the system stability for low values of TA. These mechanisms are able to keep the active power of the VSM within parameterizable limits and act a lot faster than a method previously suggested in research. To demonstrate the feasibility of the modified control, EMT (electromagnetic transient) simulations in SIMULINK/SIMSCAPE investigate a system-split scenario. The results show that the VSM behaves as expected and that the specified active-power limits are complied with, except for a short duration when a sudden large disturbance occurs.