Title: Grid-forming Control for Power Converters based on Matching of Synchronous Machines,
Abstract: We consider the problem of grid-forming control of power converters in
low-inertia power systems. Starting from an average-switch three-phase inverter
model, we draw parallels to a synchronous machine (SM) model and propose a
novel grid-forming converter control strategy which dwells upon the main
characteristic of a SM: the presence of an internal rotating magnetic field. In
particular, we augment the converter system with a virtual oscillator whose
frequency is driven by the DC-side voltage measurement and which sets the
converter pulse-width-modulation signal, thereby achieving exact matching
between the converter in closed-loop and the SM dynamics. We then provide a
sufficient condition assuring existence, uniqueness, and global asymptotic
stability of equilibria in a coordinate frame attached to the virtual
oscillator angle. By actuating the DC-side input of the converter we are able
to enforce this sufficient condition. In the same setting, we highlight strict
incremental passivity, droop, and power-sharing properties of the proposed
framework, which are compatible with conventional requirements of power system
operation. We subsequently adopt disturbance decoupling techniques to design
additional control loops that regulate the DC-side voltage, as well as AC-side
frequency and amplitude, while in the end validating them with numerical
experiments.