Higher order sliding mode STATCOM control for power system stability improvement

Abstract

The objective of this research is to design a higher order Sliding Mode Controller (SMC) for a Static Synchronous Compensator (STATCOM) and investigation of its implication on power system stability improvement. The theory of Super-Twisting–Sliding-Mode-Control (STSMC) is applied to determine the nonlinear control law of a STATCOM. The STSMC based control combines 2-sliding control and Robust Exact Differentiator (RED) which can efficiently mitigate the effect of external disturbance to the system The purpose of the application of the STSMC based control method is that it not only solves the chattering problem of classical SMC but also the derived control law is independent of system parameters. The efficacy of the design of the proposed STATCOM controller has been investigated in comparison to both the nonlinear (via exact linearization) and conventional (via approximate linearization) Linear Quadratic Regulator (LQR) based STATCOM controller. An IEEE type 14 bus multi-machine system has been taken into consideration to study the simulation results with regard to the transient stability improvement in multiple operating scenarios. It has been revealed from the simulation results that the proposed control scheme based on STSMC is more effective with respect to both the exact linearization based as well as approximately linearization based approach for the design of STATCOM controller. Furthermore, it has been abstracted that the STSMC based nonlinear STATCOM controller is competent to mitigate the dynamic instability of an electric power system even under contingency and different loading conditions.