Delay-Dependent Stability Analysis of Generator Excitation Control System Using CAN Bus

As the times develop, the use of communication is widening and communication in control systems will play a more important role. The automation of power plants also increases the level of automation and control performance by building control systems using fieldbus. In particular, the CAN bus, which can realize real-time information sharing, allows the excitation control system, governor control system and other control systems to jointly utilize the electrical quantities of the generator, thus reducing the cost of building the system and increasing the utilization efficiency of resources. However, this allows the control system to include the time delay due to communication. Worldwide, efforts are being made to reduce the instability of excitation control systems in the presence of communication-induced time delays. This is because if the generator excitation control system contains a time delay component, the instability of the control can be increased. In this paper, using Lyapunov-Krasovskii functional approach combined with Wirtinger inequality, stability criterion in linear matrix inequality (LMI) framework is presented for ascertaining the delay-dependent stability of a generator-excitation control system using field bus. Stability analysis is carried out for excitation control system based on PI controller with time-invariant feedback loop delay. The delay-dependent stability problem is formulated by mathematical modeling of closed-loop systems such as linear delay continuous-time delay differential equations, and using LMI-based stability criteria, the maximum allowable limit of the CAN bus delay for which the closed-loop system can operate normally without losing stability is calculated for various subsets of controller parameters. The effectiveness of the proposed result is validated on a benchmark excitation control system with simulation results.