| In a power system blackout, the system faces electromagnetic and electromechanical transients, which have different time scales. In this dissertation, Frequency-Adaptive Simulation of Transients (FAST) for the multi-scale modeling of transients in power systems is introduced, analyzed, implemented and validated. The proposed methodology processes analytic signals that bridge the relative merits of instantaneous and dynamic phasor signals and is distinguished by the introduction of adaptive frequency shifting of the Fourier spectra of signals. Different setting of the shift frequency enables the efficient simulation of both natural and envelope waveforms as well as the smooth transition between both.;A library of multi-scale models of circuit elements and power system devices including magnetically coupled inductors, transformers, transmission lines and synchronous machines is created. The transmission line model is distinguished in that it bridges both lumped and distributed parameters to efficiently emulate multi-scale phenomena from steady state to traveling waves. Key to the proposed model is the automatic insertion or removal of a pi-circuit cell. The synchronous machines are modeled adopting the Park transformation. In order to support the FAST methodology, the multi-scale synchronous machine model is able to provide analytic-signal terminal currents of the abc domain to the AC network from the currents of the dq0 domain. A new interface between the synchronous machine and the AC system is also designed to improve the accuracy and stability.;An algorithm that automatically determines the settings of the shift frequency and time step size is developed. With fast analysis of the Fourier spectra of monitored signals, the simulator can automatically decide whether to track the natural or envelope waveform according to the type of transients. The shift frequency and time step size can thus be obtained to achieve the specified accuracy.;Comprehensive studies involving scenarios of amplitude and angle modulation, energization and deenergization transients, electromechanical oscillations, transient recovery, short circuits, power oscillations, and load shedding are performed to confirm the validity of the proposed methodology. The validation means comprise comparison of the results with those of an EMTP-type simulator, theoretical calculations and a field test. |
