Zairong Xi

Output feedback exponential stabilization of uncertain chained systems

This paper deals with chained form systems with strongly nonlinear disturbances and drift terms. The objective is to design robust nonlinear output feedback laws such that the closed-loop systems are globally exponentially stable. The systematic strategy combines the input-state-scaling technique with the so-called backstepping procedure. A dynamic output feedback controller for general case of uncertain chained system is developed with a filter of observer gain. Furthermore, two special cases are considered which do not use the observer gain filter. In particular, a switching control strategy is employed to get around the smooth stabilization issue (difficulty) associated with nonholonomic systems when the initial state of system is known.

Nonlinear decentralized saturated controller design for power systems

In this paper, a multi-machine power system is first represented as the generalized Hamiltonian control system with dissipation. Then, a decentralized saturated steam valving and excitation controller, which is statically measurable, is proposed based on the Hamiltonian function method. Finally, an example of three-machine power system is discussed in detail.

A switching algorithm for global exponential stabilization of uncertain chained systems

This note deals with chained form systems with strongly nonlinear unmodeled dynamics and external disturbances. The objective is to design a robust nonlinear state feedback law such that the closed-loop system is globally Kexponentially stable. We propose a novel switching control strategy involving the use of input/state scaling and integrator backstepping. The new features of our controllers include the ability to achieve Lyapunov stability, exponential convergence, and robustness to a set of uncertain drift terms.

Geometric structure of generalized controlled Hamiltonian systems and its application

The main purpose of this paper is to provide a systematic geometric frame for generalized controlled Hamiltonian systems. The pseudo-Poisson manifold and the ω-manifold are proposed as the statespace of the generalized controlled Hamiltonian systems. A Lie group, calledN-group, and its Lie algebra, calledN-algebra, are introduced for the structure analysis of the systems. Some properties, including spectrum, structure-preservation, etc. are investigated. As an example the theoretical results are applied to power systems. The stabilization of excitation systems is investigated.

Energy-Based Stabilization of Forced Hamiltonian Systems with its Application to Power Systems

Abstract The purpose of this paper is twofold. First of all, the stabilization of excitation control of power systems is considered. The system has been formulated as a forced Hamiltonian system with dissipation. Then the energy-based Lyapunov function is constructed to investigate the stability of the forced system. Secondly, the model of the generalized Hamiltonian systems is proposed, which consists of externally supplied energy, dissipation and internal energy source. The state space is described as a manifold equipped with a quadratic tensor field. Global coordinate free model of the generalized Hamiltonian systems is obtained.

On output feedback stabilization of uncertain chained systems

This paper deals with chained form systems with strongly nonlinear disturbances and drift terms. The objective is to design robust nonlinear output feedback laws such that the closed-loop systems are globally exponentially stable. The systematic strategy combines the input-state-scaling technique with the so-called backstepping procedure.

Stabilization of General Nonlinear Control Systems via Center Manifold and Approximation Techniques

This paper considers the stabilization of a class of general nonlinear control systems. Under some mild conditions, a general nonlinear control system can be transformed into a normal form, which is suitable for the center manifold approach. A kind of controller in the polynomial form is proposed to stabilize the systems. First, the type and degree of controllers are chosen to assure the approximation degree of the center manifold. Then the coefficients are chosen to make the dynamics of the center manifold of the closed-loop systems stable. To test the approximate stability of the dynamics on the center manifold, the Lyapunov function with homogeneous derivative proposed in [6] is used.

Relative equilibria of power systems

In this paper, we consider the relative equilibria of the excitation control of power systems. It is shown that the systems have no common conservative quantity for both the unforced system and closed-loop system. It implies that the closed-loop system has different conservative quantity from the unforced system, i.e., it has no relative equilibrium to the power system.