Time-varying phasor
In communication theory, time-varying phasors are used for analyzing narrow-band signals, whose signal bandwidths in the frequency domain are considerably smaller than the carrier frequency.[1][2] Time-varying phasors are mostly used for analysis of frequency domain of band-pass systems.[2][1] The method uses classical impulse response.[1]
In electrical power system, phasors are used for transient analysis of the power system keeping the quasi-stationary conditions.[1][3][4] They were introduced to facilitate the computation and analysis of power systems in stationary operation.[3] Time-varying phasors are used in dynamic analysis of a large power system.[1][5] The phasor representation of sinusoidal voltages and currents is generalized to arbitrary waveforms.[2] This mathematical transformation eliminates the 60 Hertz (Hz) carrier which is the only time-varying element in the stationary case.[3] The longer usage of time-varying phasors in large power systems since 1920s have created many misconceptions. One of the misuses suggest that quasi-stationary models are always accurate, but only when the system dynamics are slow as compared to nominal system frequency which is usually 60 Hz.[4]
The concern to study time-varying phasors is raised to understand in-depth the fast amplitude and phase variations of emerging electrical power generator technologies.[4] This is because current and voltage signals of latest machines may have harmonic components and they can damage the entire transmission system which is coupled with the machine.[3][4] However, if we employ quasi-static model, we can accurately model AC signals by using time-varying phasors as opposed to traditional quasi-static model which supports constant voltage and current signals throughout the network.[5]
References
- ↑ 1.0 1.1 1.2 1.3 1.4 Venkatasubramanian, V. (1994). "Tools for dynamic analysis of the general large power system using time-varying phasors". International Journal of Electrical Power & Energy Systems 16 (6): 365–376. doi:10.1016/0142-0615(94)90023-X.
- ↑ 2.0 2.1 2.2 Jeltsema, Dimitri (2015). Camlibel, M. Kanat; Julius, A. Agung; Pasumarthy, Ramkrishna et al.. eds. "Time-Varying Phasors and Their Application to Power Analysis" (in en). Mathematical Control Theory I. Lecture Notes in Control and Information Sciences (Cham: Springer International Publishing) 461: 51–72. doi:10.1007/978-3-319-20988-3_4. ISBN 978-3-319-20988-3. https://link.springer.com/chapter/10.1007/978-3-319-20988-3_4.
- ↑ 3.0 3.1 3.2 3.3 Venkatasubramanian, V.; Schattler, H.; Zaborszky, J. (November 1995). "Fast time-varying phasor analysis in the balanced three-phase large electric power system". IEEE Transactions on Automatic Control 40 (11): 1975–1982. doi:10.1109/9.471228. ISSN 1558-2523. https://ieeexplore.ieee.org/document/471228.
- ↑ 4.0 4.1 4.2 4.3 Belikov, J.; Levron, Y. (December 2018). "Uses and Misuses of Quasi-Static Time-Varying Phasor Models in Power Systems". IEEE Transactions on Power Delivery 33 (6): 3263–3266. doi:10.1109/TPWRD.2018.2852950. ISSN 1937-4208. https://ieeexplore.ieee.org/document/8403297.
- ↑ 5.0 5.1 "Comparison of time-varying phasor and dq0 dynamic models for large transmission networks" (in en). https://www.researchgate.net/publication/317252520.
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