Adaptive Super Twisting Sliding Mode Load Frequency Control for an Interconnected Power Network with Nonlinear Coupling Between Control Areas

Abstract

The article revisits the design of sliding mode control (SMC) for load frequency problems in power systems. Unlike works reported earlier, an adaptive super twisting SMC (ST-SMC) is designed for two area interconnected power network under load disturbance. The two control areas are nonlinearly coupled to each other making the control objective more challenging. The proposed design ensures asymptotic convergence of frequency and tie line power deviations under any load disturbance. In practice, the bounds of unknown disturbances in a power network are often not known. Therefore, dynamically adapted gains are considered in the design of the ST-SMC that ensures better control efficiency without controller gains being overestimated. The proposed controller is compared with conventional SMC designed for interconnected power systems. The merit of the proposed design is observed in control input which is significantly less affected by chattering without any loss in the control accuracy. The proposed design is also validated with typical nonlinearities in power systems like generation rate constraints (GRC) and governor dead band (GDB). The effectiveness of the proposed design is shown by simulation.