Robust Higher Order Observer Based Non-linear Super Twisting Load Frequency Control for Multi Area Power Systems via Sliding Mode

Abstract

The article focuses on the design of higher order sliding mode observer (HOSMO) based super twisting sliding mode control (ST-SMC) for load frequency problems in an interconnected multi area power systems. A sudden load disturbance in any area can cause deviations in frequency and tie line power from their desired values. The proposed design functions for the improved overall performance of the system. High frequency oscillations (chattering) which is the main operational problem with SMC is investigated through ST-SMC. Firstly, with inherent advantages of robustness, insensitivity to uncertainties and disturbances, the HOSMO estimates the system states from the output and control signal. Secondly, the ST-SMC acts only on the first time derivative of sliding surface to ensure finite time convergence of frequency and tie line power deviations. The supremacy of the proposed design compared to modern state of the art lies in improved transient and steady state behavior, robustness and chattering free control without any loss in control accuracy. Furthermore, performance indices like integral square error (ISE), integral absolute error (IAE) and integral time absolute error (ITAE) for the said controller are found to be lesser compared to that of linear and nonlinear SMC. The said controller also results in acceptable frequency deviation when validated under random step load disturbances, parameter uncertainties, with an integration of renewable energy resource and nonlinearities in power systems like generation rate constraints (GRC) and governor dead band (GDB).