Comparative analysis of a virtual synchronous machine and a synchronverter based on grid-forming benchmark scenarios

The increasing integration of inverter-based resources and the related reduction in the number of synchronous generators lead to a decrease in the inertia available to the power system. One potential solution for providing virtual inertia is the application of grid-forming control methods to inverter-based resources. This paper presents a comparative analysis of two distinct methods, both of which fall within the category of virtual synchronous machines (VSM). The two methods are compared and parameterised on the basis of a small-signal model and evaluated in electromagnetic transient (EMT) simulations using selected benchmark scenarios in accordance with the preliminary requirements of a German transmission system operator (TSO), TenneT. Both methods comprise cascaded control loops. This paper focuses on the different active and reactive power controllers that serve as main controllers. The identical secondary current control loops are employed for both methods in order to provide an indispensable current limiting function. It is demonstrated analytically and in EMT simulations that the investigated methods can be parameterised in a way that they show an identical transient response and that they can successfully meet the preliminary requirements for grid-forming inverters of the German TSO in the considered scenarios.