Stability analysis of network-controlled generator excitation system with interval time-varying delays

This paper deals with the problem of stability analysis of generator excitation system (GES) with interval time-varying delays. Network-controlled GES involves transmitting measured data from the plant site to controller and control signals from the controller to the plant site. Open communication channels impart time-varying nature to the delays. These time-varying delays can vary between intervals which would affect the system stability. The model of a GES is developed with the proportional integral (PI) controller including delay effects. In this paper, a less conservative delay-dependent stability criterion is derived using Lyapunov-Krasvoskii functional (LKF) for GES with interval time-varying delays. The bounding technique for derivative of LKF is developed by using Wirtinger inequality and free-weighting matrices. The relationship between the delay margins of GES and gains of the PI controller are investigated. This delay margin is used to tune the PI controller. The adequacy of the proposed result is confirmed by using simulation studies

Stability analysis of network-controlled DC position servo system with time-delay

This paper presents a stability analysis of network-controlled direct current (DC) position servo system with time-delays (TDs). The usage of communication links and measurement devices in the network-controlled system involves a considerable amount of TDs. Those TDs would degrade the dynamic performance and causes instability to the DC position servo system. A less conservative delay-dependent stability (DDS) criterion is presented by using Lyapunov–Krasvoskii functional and linear matrix inequality techniques. The maximum allowable TD called delay margin (DM) is computed, which can be used to tune a proportional-integral (PI) controller of the DC position servo system. Two cases of TD are considered in this analysis: time-invariant and time-varying delays. The DDS approach is used to study the trade-off between the PI controller gains and the DMs. This approach together with numerical simulation gives the insightful trade-off between DM and dynamic performance of the system. Finally, the stability of the DC position servo system with PI controller is analysed in the presence of TD through the experimental setup

Passivity Based Stability Condition for Interefered Digital Filters

This paper presents a new passivity condition for fixed-point state-space interfered digital filters using saturation arithmetic. Passivity is a way to characterize input-output stability of a system, that is, supplied bounded input energy produces bounded output energy. The presented criterion also ensures asymptotic stability of the state-space digital filter with zero external disturbances. The result is expressed in terms of linear matrix inequality, and therefore, can be solved via existing numerical packages. A numerical example is arranged to validate the usefulness of the proposed method