Extended integral control for load frequency control with the consideration of generation-rate constraints

This paper presents an extended integral control to LFC (load frequency control) scheme with the presence of GRC (generation rate constraints) in order to get rid of the overshoot of conventional PI control. The conventional LFC scheme does not yield adequate control performance with consideration of the singularities of speed-governor such as rate limits on valve position and GRC. In order to overcome this drawback, an extended integral control is developed for the PI control of the speed governor under the presence of GRC. The key idea of the extended integral control is using a decaying factor to reduce the effects of the error in the past. The decaying factor greatly affects the control performance, and should be carefully selected. This study determines the decaying factor in proportion to the degree of deviation in several levels. The computer simulation has been conducted for the single machine system with various load changes. The simulation results show that the proposed controller based on extended integral control yields much improved control performance, compared to the conventional PI controller