Real-time implementation of grey fuzzy terminal sliding mode control for PWM DC-AC converters

Classical terminal sliding mode control (TSMC) has finite system state convergence time and is insensitive to disturbances and uncertainties within expected limits. However, TSMC may chatter when uncertainty values are overestimated or may exhibit a steady-state error when uncertainty values are underestimated. An improved TSMC is proposed by the use of a mathematically simple and computationally fast grey prediction (GP) methodology, which is then fine-tuned by the use of fuzzy control methodology for PWM DC-AC converters. First, GP methodology is employed to deal with classical TSMC chattering and steady-state error problems. Fuzzy control is then used to tune the GP forecasting value for improved rise time and overshoot characteristics. The system is evaluated by simulation and also by real experiment. Both evaluation methods confirm that the proposed controller achieves low total harmonic distortion under non-linear loading conditions and fast dynamic response under transient loading conditions. Because the proposed grey-fuzzy TSMC methodology is simpler to implement than prior methods and offers more efficient computation, it will be of interest to designers of related control systems.