AN ADAPTIVE DIGITAL MULTIVARABLE STABILIZBR FOR A MULTIMACHINE PLANT
It has long been recognized that the simple control strategy of using an individual stabilizer on each generator in a power plant has not always been effective. Such stabilizers usually derive their control action from only one measured signal, and therefore they are not capable of camping out all modes of oscillation. Furthermore, these stabilizers are usually not adaptive, in that they do not alter their control action when plant operating conditions change. An alternative is to employ a multivariable stabilizer which uses a much larger set of variables from all machines in a plant to generate a coordinated set of control signals. In this way, all modes of oscillation can be adequately damped. One such stabilizer based on the Generalized Heffron-Phillips model of a multimachine plant has been designed with the aid of modal control theory. As reported, this stabilizer was not adaptive. This thesis extends the development of this multivariable stabilizer so that it recognizes changes in operating conditions and adapts itself to provide optimum control. An adaptive scheme is formulated and a digital computer implementation is described. Since it is not desirable to carry out preliminary testing of the adaptive stabilizer on an operating power plant, an alternative test environment is chosen. An analogue computer simulation of a multimachine plant is set up and the tests carried out on it are described. The results prove that the adaptive stabilizer operates satisfactorily to provide auxiliary damping of intermachine oscillations and that it adapts itself properly to changing load conditions on the plant.