Theory and applications of adaptive control-A survey

The adaptive control of a class of large-scale systems formed of an arbitrary interconnection of subsystems with unknown parameters, nonlinearities, and bounded disturbances is investigated. It is first shown that no matter how weak the interconnections are, a decentralized adaptive control scheme can become unstable. Approaches are then developed for stabilization and tracking using new decentralized adaptive controllers. In the case where the relative degree n^{*} of the transfer function of each decoupled subsystem is less than or equal to two, sufficient conditions are established which guarantee boundedness and exponential convergence of the state and parameter errors to bounded residual sets. In the absence of disturbances and interconnections, the decentralized adaptive control schemes guarantee exact convergence of the tracking errors to zero. The effectiveness of the proposed adaptive schemes is demonstrated using a simple example.

Decentralized adaptive control of interconnected systems

An adaptive controller is presented for load-frequency control of power systems. It uses a PI (proportional-integral) adaptation to satisfy the hyperstability condition for taking care of the parameter changes of the system. Only the available information on the states and output are required for the control. No explicit parameter identification is needed. The controller can be designed by using a reduced plant model to simplify the design without degrading the performance much, so it is very easy to implement practically. The simulation results indicate that good control performance can be obtained and that the performance is sensitive to the plant parameter changes. The control remains effective in the presence of generation rate constraints. >

An adaptive controller for power system load-frequency control

A robust controller, based on the Riccati-equation approach, is proposed for power system load-frequency control. Only the bounds of the system parameters are required to design the robust load-frequency controller. The proposed robust controller is simple, effective and can ensure that the overall system is asymptotically stable for all admissable uncertainties. Simulation results show that, for the example system, the proposed robust load-frequency controller can achieve good performance even in the presence of generation rate constraint.

Robust load-frequency controller design for power systems

Adaptive control is now finding its way into the marketplace after many years of effort. This paper reviews some ideas used to design adaptive control systems. It covers early ideas which primarily attempt to compensate for gain variations and more general methods like gain scheduling, model reference adaptive control, and self-tuning regulators. It is shown that adaptive control laws can be obtained using stochastic control theory. Techniques for analyzing adaptive systems are discussed. This covers stability and convergence analysis. Issues of importance for applications like parameterization, tuning, and tracking, as well as different ways of using adaptive control are also discussed. An overview of applications which includes feasibility studies as well as products based on adaptive techniques concludes the paper.

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J. P. Monville

Papers

Paper: Improving power network stability and unit stress with adaptive generator control

A Method to Improve the Power Network “Steady State Stability” and to Reduce the Unit Stress. The Multivariable Adaptive Control of Generators