Optimal Control And Design Of Power Systems Using Lyapunovs Direct Method

The complexity and time-varying nature of large power systems mashes the design of controllers for the synchronous generators extremely difficult. Various sophisticated control theories (e.g. Linear quadratic regulato1, domain separation, modal control) have been applied to linearised mathematically models of these ay ebene. In all these cases the design is carried out for rated machine power at a conditionally stable operating point. If changes in machine operating point, machine parameters or system configuration occur then the design performance will be ‘de-rated'. Adaptive control provides an alternative design approach to this problem, where the controller has a variable structure which enables iit to compensz'.e for variations in the controlled system. This approach is applicable to small (5%) disturbance condition only because during large disturbances, system parameters may vary too quickly to be compensated. In this latter case other design techniques may be applied. It is possible to use a small digital computer to switch from one algorithm to another to implement the required control. The particular approach used in this thesis (referred to as model reference-adaptive control) employs Lyapunov function based on the error generated by model and plant states to design the controller. This method ensures the stable behavior (in the sense of Lyapunov) of the controller