Robust Load Frequency Control

It is highly desirable that any control system is not affected by modeling errors or parameter variations of a controlled object. This paper presents an application of a robust feedback control system to load frequency control of an interconnected power system. In the design of this control system, parameter variations in a controlled object are formulated as disturbances to the system, and then a robust compensator is introduced. This compensator makes the transfer functions between these equivalent disturbances and the controlled output exactly or approximately zero. As a result, the frequency characteristic between the reference input and the controlled output is kept almost unchanged over a specified frequency range, even if some parameters in the controlled object vary widely from their nominal values. The robust compensator is, moreover, effective in real disturbances such as load changes. The effect of the control system is demonstrated by an example applied to a two-area interconnected power system model.