Makale Koleksiyonu
https://hdl.handle.net/11480/5937
Article Collection2022-05-22T02:43:08ZComputation of time delay margins for stability of a single-area load frequency control system with communication delays
https://hdl.handle.net/11480/733
Computation of time delay margins for stability of a single-area load frequency control system with communication delays
Sönmez, Şahin; Ayasun, Saffet; Eminoğlu, U.
Time delays have become unavoidable in power systems since communication links are extensively used for sending and receiving control signals. This paper investigates the effect of time delays on the stability of a single-area load Frequency Control (LFC) system. A direct and exact method to compute delay margins is presented. The delay margin is the maximum amount of the time delay that the system can tolerate before it becomes unstable for a given operating point. The proposed method starts with the determination of all possible purely imaginary characteristic roots for any positive time delay. To achieve this, Rekasius substitution is first used to convert the transcendental characteristic equation of the LFC system into a polynomial. Then, Routh stability criterion is applied to determine the critical root, the corresponding oscillation frequency and the delay margin for stability. For a wide range of controller gains, delay margins of LFC system are determined to find out the qualitative effect of controller gains on the delay margin. Finally, theoretical delay margin results are verified by using the time-domain simulation capabilities of Matlab/Simulink.
2014-01-01T00:00:00ZEffect of load increase and power system stabilizer on stability delay margin of a generator excitation control system
https://hdl.handle.net/11480/3735
Effect of load increase and power system stabilizer on stability delay margin of a generator excitation control system
Sönmez, Şahin; Ayasun, Saffet
This paper studies the impact of load increase and a power system stabilizer (PSS) on the stability delaymargin of a single-machine-infinite-bus system including an automatic voltage regulator. An analytical method isproposed to determine the stability delay margin of the excitation control system. The proposed method first eliminatestranscendental terms in the characteristic equation of the excitation system without making any approximation and transforms the transcendental characteristic equation into a regular polynomial. The key result of the elimination process is that the real roots of the new polynomial correspond to the imaginary roots of the transcendental characteristic equation. With the help of the new polynomial, it is also possible to determine the delay dependency of system stability and the root tendency with respect to the time delay. Delay margins are computed for various loading conditions and PSS gains. It is observed that the delay margin generally decreases as the PSS gain and load demand increase, resulting in a less stable system.
WOS: 000393327200048
2016-01-01T00:00:00Z