New Approach to SMES Optimal Control in Power System Transients

The paper describes an approach to the choice of control for turbine and electric energy storage devices in power system aiming at maximum transient stability improvement. The aim is achieved by the use of Pontryagin´s maximum principle. The solution obtained for nonlinear dynamic system can not be directly implemented because it is in the form of control trajectories but it is very useful in estimating technical possibilities of different controlled elements (synchronous generator, SMES, SVC etc.). Pontryagin´s maximum principle has been expanded to nonlinear dynamic system described by both differential and algebraic equations and optimal control problem dimension was reduced by m(n+l-T) as compared to the approach in [1] by the use of Lagrangian coefficients. The paper shows that new optimality conditions give the same results. The above approach has been used for the choice of turbine and SMES control in a simple EPS with the account of turbine governors speed and SMES coil current change rate constraints.