Optimal Output – Feedback a Multirate Stabilization Techniques Applied to the Design of Excitation Controllers of a three Phas

In this paper an optimal control strategy, is used to design a desirable excitation controller of a hydrogenerator system, in order to enhance its dynamic stability characteristics. The proposed control strategy based on Two-Point-Multirate Controllers (TPMRCs) is readily applicable in cases where the state variables of the controlled plant are not available for feedback, since TPMRCs provide the ability to reconstruct exactly the action of static state feedback controllers from input-output data, without resorting to state estimators, and without introducing high order exogenous dynamics in the control loop. In the TPMRCs based scheme, the control is constrained to a certain piecewise constant signal, while each of the controlled plant outputs is detected many times over a fundamental sampling period T0. On the basis on this strategy, the original problem is reduced to an associate discrete-time linear quadratic (LQ) regulation problem for the performance index with cross product terms, for which a fictitious static state feedback controller is needed to be computed. Simulation results for the actual 117 MVA hydrogenerator unit, show the effectiveness of the proposed method which has a quite satisfactory performance. KeywordsOptimal control Multirate controllers , power systems, hydrogenerator.