Output tracking control with enhanced damping of internal dynamics and its output boundedness

This paper investigates an important and challenging problem in nonlinear systems: achieving both output tracking control with a tolerable bound and enhanced damping control of internal dynamics. This problem is solved by using a damping controller in an input-output linearized STATCOM system. The proposed controller provides improved damping for lightly damped internal dynamics with degraded but tolerable output tracking performance. It ensures that the tracking error of output stays within a bound. Finding a parameter-dependent Lyapunov function for the zero dynamics proves the stability of the damped internal dynamics for time invariant/varying trajectories. Stability of the closed-loop system is established by designing a Lyapunov function.