Exploration of Time-Delay Effect on the Stability of Grid-Connected Power Converters with Virtual Inertia

The lack of inertia contributions from renewable generators, which are essentially power electronic converters in replacement of synchronous generators, may greatly degrade the frequency regulation performance. As a solution, distributed virtual inertia provided by grid-connected power converters has been introduced as an effective approach to improve power system inertia. However, time-delays, which can be introduced by signal measurement, converter control, and communication, are ignored in the existing virtual inertia control implementations. To fill this research gap, this paper presents a detailed analysis of the effect of time-delays on virtual inertia control. It is revealed that instability will happen when the virtual inertia is greater than the existing power system inertia regardless of time-delays. In other cases, the system stability depends on time-delays, together with other design parameters. For verification, the experimental results are presented, which are consistent with the theoretical analysis.