Optimal control of synchronous-machine excitation by quasilinearisation techniques

This paper describes the application of quasilinearisation techniques in solving nonlinear optimal-control problems in power systems. The computational effectiveness of this method is demonstrated in controlling the excitation to optimise the performance of a synchronous machine simulated as a simple 3rd-order system. The results presented in this paper show that the application of quasilinearisation technique gives an accurate solution utilising considerably less computer time compared with the more commonly used gradient method. However, the core requirements for this method are greater than those for the gradient method. To examine the effects of the relative emphasis placed on the different state variables in the performance criterion, optimisation has been carried out with respect to two different quadratic indices. The usefulness of the quasilinearisation technique is further demonstrated by its application to an optimisation problem with practical constraints on the control variable.