Virtual Oscillator-Controlled Grid-Forming Inverters Incorporating Online Parametric Grid Impedance Identification

Recently, an emerging communication-free control strategy called dispatchable virtual oscillator control (dVOC) has been introduced for grid-forming (GFM) inverters. In contrast to droop control which operates based on phasor quantities, dVOC is a non-linear and time-domain approach and stabilizes arbitrary initial conditions to a sinusoidal steady state. As recent studies emphasize the relation between the performance (e.g., stability) of dVOC-based inverters and the Thevenin grid impedance seen by the inverter at its point of common coupling (PCC), it becomes necessary to enable these inverters to online estimate the grid impedance. Therefore, this chapter presents the implementation of an online parametric grid impedance estimation into the control loop of a single-phase dVOC-based inverter operated in a grid-connected mode. The identification of the grid impedance is achieved based on the injection of the pseudorandom binary sequence (PRBS).