Amplitude/Frequency Continuous Modulation Law of Oscillation Signals in Power Systems and Demodulation Method

With the increasing penetration of power electronic devices in power systems, the issue of system oscillations has become increasingly complex. Understanding and analyzing the system oscillation process is fundamental to mitigating system oscillations. However, traditional methods primarily analyze system oscillations through the amplitude/frequency characteristics of harmonics. Yet, the amplitude/frequency of harmonics does not reflect the physical characteristics of the system’s oscillation signals. The actual formation of oscillation signals is as follows: after the system is disturbed, the equipment drives changes in the internal voltage amplitude/frequency through an imbalance of active and reactive power at the ports. The changes in the internal voltage amplitude/frequency act on the network, driving further changes in the active and reactive power at the equipment ports. The interaction between the system devices and the network forms the modulation process of the oscillation signals in the power system. Based on the objective law of system oscillation signal modulation over time, this paper proposes a method using particle swarm optimization(PSO) to extract the amplitude/frequency modulation characteristics of oscillation signals. Finally, the validity of the amplitude/frequency modulation law of system oscillation signals is verified through the analysis of the internal voltage oscillation waveforms obtained from a grid-connected inverter system simulation.