Youyi Wang

Robust control of a class of uncertain nonlinear systems

This paper considers the robust control of a class of nonlinear systems with real time-varying parameter uncertainty. Interest is focused on the design of linear dynamic output feedback control and two problems are addressed. The first one is the robust stabilization and the other is the problem of robust performance in an H∞ sense. A technique is proposed for designing stabilizing controllers for both problems by converting them into ‘scaled’ H∞ control problems which do not involve parameter uncertainty.

Global Transient Stability and Voltage Regulation for Power Systems

Summary form only given as follows. This paper is concerned with the global control of power systems. It arises from the practical concern that transient stability and voltage regulation are both important properties of power system control, but they are ascribed to different model descriptions and relate to different stages of system operation (i.e. transient period and post-transient period respectively). Earlier control results deal with the two problems separately, or employ a switching strategy of two different kinds of controllers, which causes a discontinuity of system behavior. We design in this paper a global controller to co-ordinate the transient stabilizer and voltage regulator. The designed controller is smooth and robust with respect to different transient faults. Simulations on a single-machine infinite bus power system have demonstrated better performances compared with existing controllers.

Robust decentralized nonlinear controller design for multimachine power systems

In this paper, a robust decentralized excitation control scheme is proposed for multimachine power system transient stability enhancement. First, a direct feedback linearization (DFL) compensator through the excitation loop is designed to eliminate the nonlinearities and interconnections of the multimachine power system. Then, a robust decentralized controller is proposed to guarantee the asymptotic stability of the DFL compensated system considering the effects of plant parametric uncertainties and remaining nonlinear interconnections. The design procedure for an n-machine power system involves in solving n Riccati equations. In the design of the robust nonlinear decentralized controller, only the bounds of generator parameters need to be known, but not the transmission network parameters, system operating points or the fault locations. Since the proposed robust nonlinear decentralized controller can guarantee the stability of the large scale power system within the whole operating region for all admissible parameters, transient stability of the overall system can be greatly enhanced. The design procedure is tested on a three-machine example power system. Simulation results show that the proposed control scheme can greatly enhance the transient stability of the system regardless of the network parameters, operating points and fault locations.

H ∞ filtering for a class of uncertain nonlinear systems

Abstract This paper investigates the problem of H ∞ filtering for a class of uncertain continuous-time nonlinear systems with real time-varying parameter uncertainty and unknown initial state. We develop an infinite horizon H ∞ filtering methodology which provides both robust stability and a guaranteed H ∞ performance for the filtering error irrespective of the parameter uncertainty.

Parameter Identification for PEM Fuel-Cell Mechanism Model Based on Effective Informed Adaptive Particle Swarm Optimization

In order to improve the inherent drawbacks of particle swarm optimization (PSO), an effective informed adaptive PSO (EIA-PSO) algorithm that has better equilibrium characteristic between global search and local search is proposed. In this paper, an electrochemical-based proton exchange membrane fuel cell (PEMFC) mechanism model suitable for engineering optimization is developed, and a parameter-identification-technique-based EIA-PSO for this mechanism model is presented. In order to verify the validity of the advanced method, comparisons between experimental data and simulation data are carried out. The results demonstrate that EIA-PSO can make the mechanism model with identified parameters fit the experimental data with higher precision even in the presence of measurement noise. Therefore, EIA-PSO is an optional effective technique for identifying the parameters of the PEMFC mechanism model.

Nonlinear output stabilization control for multimachine power systems

In this paper, a robust decentralized nonlinear control scheme is proposed for multimachine power system stability enhancement. The nonlinear controller consists of a novel dynamic direct feedback linearization (DFL) compensator through the excitation loop to cancel the nonlinearities and interactions among generators and a robust feedback controller to guarantee the asymptotic stability of the DFL compensated system considering the effects of dynamic output feedback and plant parametric uncertainties. The decentralized controller for each generator in the multimachine system is obtained by solving an algebraic Riccati equation. The nonlinear controller can guarantee the stability of the multimachine nonlinear power system within a whole operating region for all admissible parameters. The design procedure is tested on a three-machine power system. Simulation results show that the proposed control scheme can greatly enhance the stability of the system, regardless of the network parameters, operating points, and fault locations.

Robust nonlinear coordinated control of power systems

To prevent an electric power system losing synchronism under a large sudden fault and to achieve voltage regulation are major objectives in power system design. This paper applies the Riccati equation approach, together with the direct feedback linearization (DFL) technique, to design robust nonlinear controllers for transient stability enhancement and voltage regulation of power systems under a symmetrical three-phase short circuit fault. A DFL excitation controller and a DFL coordinated controller (excitation and fast valving controller) are proposed. The simulation results show that a power system can keep transiently stable, even when a large sudden fault occurs at the generator terminal. The robust nonlinear DFL controllers proposed here can greatly improve transient stability and achieve voltage regulation.

Robust nonlinear controller design for transient stability enhancement of power systems

A robust DFL (direct feedback linearization) nonlinear excitation controller is proposed to enhance transient stability for power systems. A robust control technique for linear systems is extended to design this controller. The design of the controller is independent of the operating point. Simulation results show that the controller has the following advantages: the fault location does not need to be known and the controller can overcome the variation of the reactance of the transmission line. Both transient stability enhancement and voltage regulation can be achieved.<<ETX>>

A new nonlinear voltage controller for power systems

A new nonlinear voltage controller is proposed in this paper. The design of this controller involves the direct feedback linearization (DFL) technique and robust control theory. The performance of the proposed nonlinear controller in a single machine-infinite bus power system is simulated. The simulation results show that both voltage regulation and system stability enhancement can be achieved with this proposed controller, regardless of the system operating condition, and compared to other kinds of controllers, the proposed nonlinear controller gives better dynamic performance and robustness.

Robust filtering for a class of discrete-time uncertain nonlinear systems: An H∞ approach

This paper deals with the H∞ filtering problem for a class of discrete-time nonlinear systems with or without real time-varying parameter uncertainty and unknown initial state. For the case when there is no parametric uncertainty in the system, we are concerned with designing a nonlinear H∞ filter such that the induced l2 norm of the mapping from the noise signal to the estimation error is within a specified bound. It is shown that this problem can be solved via one Riccati equation. We also consider the design of nonlinear filters which guarantee a prescribed H∞ performance in the presence of parametric uncertainties. In this situation, a solution is obtained in terms of two Riccati equations.