Global Frequency Reference Tracking as an Oscillation Suppression Mechanism in VSM Primary Control: A Coupled-Oscillator Study

TL;DR

This paper proposes a global frequency reference tracking control for VSM inverters that improves transient stability and reduces oscillations in power systems by transforming synchronization into a reference tracking problem.

Contribution

It introduces a control architecture that uses a global frequency reference for VSM inverters, enhancing transient response and stability compared to traditional mutual synchronization methods.

Findings

Reduced frequency overshoot in simulations

Elimination of underdamped oscillations

Lower angular stress in the network

Abstract

Synchronization in power systems is traditionally achieved through physical network coupling, whereby inverter-based resources (IBRs) and synchronous machines converge to a common frequency via oscillatory swing dynamics. In conventional operation, secondary control acts on a slow time scale and is typically engaged only after the primary dynamics have largely settled. As a result, in the absence of an explicit global reference, disturbances can induce prolonged transients and large phase excursions. This work considers a setting in which the total active power balance is known and maintained at all times, and proposes a control architecture for virtual synchronous machine (VSM) based inverters in which all units track a broadcast global frequency reference. Under this assumption, synchronization is transformed from a mutual oscillator locking problem into a reference tracking problem. Using a second order swing network model, we show that embedding a simple proportional integral (PI) frequency controller can significantly improves transient behavior. A washout mechanism ensures that the additional control action vanishes in steady state, thereby preserving network determined power sharing. Simulations on a three oscillator network demonstrate reduced frequency overshoot, elimination of underdamped oscillations, and lower angular stress compared to conventional open loop synchronization, highlighting the effectiveness of a global frequency reference as a coordination mechanism for grid-forming inverter networks.