Electric Network Stimulation-Response Relationship and Its Characteristics Under Time-Varying Amplitude and Frequency

The process that, the equipment regulates internal voltage's amplitude and frequency (A/F) to generate changes in the electric network terminal power, plays a critical role in determining a power system's dynamic behavior. Traditional system analysis relies on the “quasi-steady state” assumption of constant frequency to investigate the network, and the results are often reasonable due to the network's time constant being fast enough compared to the internal voltage dynamics. However, the increasing integration of converter-interfaced equipment with fast A/F dynamics raises concerns about the network's power variations concerning the A/F, including the characteristics of potentially impacting power system dynamics. To address these concerns, this paper emphasizes the demands for analyzing the network's stimulation-response relationships under the dynamic practice of time-varying A/F. It provides a generalized method to establish explicit expressions for the original stimulation-response relationship of the network. On this basis, the dynamic characteristics potentially impacting the system dynamic processes are analyzed and elaborated. In addition, this paper identifies differences in the system's dynamic behaviors that may arise from commonly used static network relationships, even for system electromechanical dynamics. This work aims to lay the foundation for further understanding of the physics and analytics of the network under the equipment-regulated time-varying A/F.