A time-domain approach is formulated to analyze oscillations that are induced by control valve stiction in feedback control loops. Analytical relationships are established between the proportional-integral controller parameters and the oscillation amplitude and period of the process output. Based on the relationships and the robustness to model uncertainties, a new compensation method by tuning controller parameters is proposed to reduce the oscillation amplitude to a desired value. Compared with the describing function approach, the time-domain approach achieves a significant improvement in accuracy in calculating the oscillation amplitude and period. By contrast to the counterparts in the literature, the proposed compensation method is quantitative, and avoids tuning the controller parameters in a trial-and-error manner to compensate oscillations. Experimental examples illustrate the effectiveness of the obtained results.
Thyristor Controlled Series Compensation (TCSC) is expected to provide various benefits to power systems, including transient stability improvement, Subsynchronous Resonance (SSR) mitigation, power swings damping, fault current reduction, etc. Grasping the characteristics of TCSC installations and finding effective firing control strategies are essential to implement these advantages. This paper studies two important aspects of TCSC characteristics, the time constant of TCSC dynamic response and impacts of reference signals for thyristor firing angles on TCSC dynamic response. Closed-loop impedance control is proposed to speed the dynamic response of TCSC. A "two-stage" firing control method is presented to accomplish smooth switching between the capacitive region and inductive region. Both digital simulations w i t h EMTDUPSCAD software and physical experiments are employed in the study.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.