Self Tuning Load Frequency Controller for Interconnected Power Systems Including Effects of Nonlinearities

A study is described of the load frequency and tie-line power control of a multi-area interconnected power system, using self tuning control based on a minimum variance strategy. Each area in the interconnection is represented by a stochastic ARMAX model and area generation control is computed by a self tuning algorithm with an extended recursive least squares technique for parameter estimation. It is shown that the ARMAX predictive model, although inadequate in modelling the non-zero mean value of the power system load disturbances, is capable of describing the system dynamic behaviour and satisfies the load frequency control objectives. To comply with the zero-mean characteristic of the ARMAX model, a modified predictive model is developed where the non-zero mean component of the load disturbances is predicted as a function of local area variables, and integrated into the control algorithm. Simulation studies show that with this modification, the system response is noticeably improved especially when generation rate constraint and governor dead-band nonlinearities are taken into account.