Frequency-Domain Large-Signal Modeling and Stability Analysis for Dispatchable Virtual Oscillator Control

Dispatchable virtual oscillator control (dVOC) is a time-domain nonlinear control method for grid-forming voltagesource converters (VSCs). The large-signal stability assessment of the dVOC-based VSC-grid system under large disturbances is crucial to ensuring secure and resilient system operation. This paper develops a comprehensive frequency-domain large-signal modeling and stability analysis approach to establish the global asymptotic large-signal stability of dVOC. We utilize the smallgain theorem to analyze large-signal stability by separating the linear and nonlinear gains in the frequency domain. A symmetric linear gain matrix is derived, and a bounded nonlinear gain is designed. It is found that as long as the overall system gain, defined as the product of the linear and nonlinear gains, is less than one, the dVOC-based VSC can always synchronize with the grid under large disturbances. A sufficient condition for global asymptotic large-signal stability is derived, and the theoretical analysis is validated through experimental results.