Trajectory-sensitivity design of load-frequency control systems

A method is described for limiting the trajectory dispersion of a load-frequency control system due to parameter variations with a controller subject to structure constant. The parameter variations are assumed to be small, so that linear sensitivity equations are obtained for the trajectory-sensitivity function. The desensitisation problem is then formulated as a suboptimal-control problem with a specified feedback structure and a quadratic performance index which also includes the trajectory-sensitivity function. The controller gain minimising the cost function is determined by iterative application of an algorithm for parameter optimisation based on averaging the performance criterion. Applied to a 2-area system, the design procedure is shown to produce a load-frequency control system with a trajectory sensitivity to the varying-incremental-speed-regulation parameter greatly reduced compared with that of the corresponding suboptimal-control system designed without sensitivity considerations, while maintaining a satisfactory performance.