Output voltage control of synchronous generator using diode and thyristor excitation structures combined with multivariable H∞ controllers

In this study, the authors present a comparison between two excitation structures. The first one consists of a diode bridge rectifier connected to a wound field synchronous machine. In the second structure, the diode bridge is replaced by a thyristor one. A multi-input single-output (MISO) H_∞ voltage controller is designed for each structure. The proposed controllers take into account the modeling of each structure and permit to guarantee the system stability during the sudden variation of the load connected to the terminal of the main synchronous machine. The performance of each structure is evaluated by experimental tests in the presence of unknown variations of the power system operating conditions. The results show the great efficiency of the thyristor excitation structure combined with the MISO H_∞ controller as regards the response time, the voltage drop and the voltage overshoot.