Decoupled Model Predictive Control for Three-Level Flying Capacitor Boost Converter Based on a Nonlinear Extended State Observer

This paper proposes a continuous-set decoupled model predictive control (DMPC) strategy for voltage balancing problem of three-level flying capacitor boost converter (TL-FCBC). To mitigate system coupling effects, a reduced-order state-space equation (ROSSE) of the TL-FCBC is first established by regulating the flying capacitor voltage through an outer-loop controller. This ROSSE introduces an adjustable flexible parameter that can be finely adjusted according to different converter operating conditions. This outer-loop controller adopts the super-twisting sliding mode control (STSMC) to obtain the appropriate duty cycle difference between two switches, thus achieving flying capacitor voltage balance. The proposed DMPC serves as the inner-loop controller, with ROSSE employed as the predictive model, enabling real-time tracking of the reference values for both output voltage and inductor current. In order to further enhance the system robustness against parameter variations, a nonlinear extended state observer (NESO) is developed to accurately estimate the changes of load resistance and input voltage in real-time. By constructing a Lyapunov function, the asymptotic stability of the TL-FCBC system is proven theoretically. Experimental results validate the effectiveness of the proposed control strategy, which has good voltage balancing capability and robustness.