Closed-Loop Optimal Excitation Control for Power System Stability

An optimal excitation control for the stability of synchronous machines is found in a closed form using Pontryagin´s minimum principle. While the optimal control is bang bang, in practice it is necessary to compromise with normal voltage regulator action to produce a sub-optimal control. The time required for stabilization is slightly increased by this. The results obtained for the single machine- infinite bus case indicate that such control provides major benefits in removing transients.