A Novel Tri-State DC–DC Converter and Robust Nonlinear Control for Fuel Cell–Ultra Capacitor based Hybrid Electric Vehicles

Conventional DC-DC power converters employed in electric vehicle (EV) applications, including boost, buck-boost, fly-back, and interleaved converters, exhibit a right-half-plane (RHP) zero under continuous conduction mode (CCM), resulting in non-minimum-phase behavior and degraded dynamic performance. This research proposes a novel hybrid energy storage system (HESS) based on tri-state boost and tri-state buck-boost converters that eliminate the RHP zero, thereby enabling faster transient response and improved controllability. To achieve precise regulation of the system, three nonlinear control strategies, namely Lyapunov redesign, sliding mode control (SMC), and super-twisting sliding mode control (ST-SMC), are developed for accurate DC-bus voltage regulation and precise tracking of the polymer electrolyte membrane fuel cell (PEMFC) and ultra-capacitor (UC) currents. A rigorous Lyapunov-based stability analysis is presented to establish the global asymptotic stability of the closed-loop system. The proposed controllers are validated through MATLAB/Simulink simulations under the European Extra Urban Driving Cycle (EUDC) and hardware-in-the-loop (HIL) implementation using a TMS320F28379D dual-core microcontroller platform. Comparative results demonstrate that the ST-SMC achieves superior dynamic performance with reduced tracking error, minimized overshoot/undershoot, improved disturbance rejection capability, reduced chattering, and the lowest integration of square error (ISE) value of 1.689 × 104 compared with the Lyapunov redesign and SMC approaches. Furthermore, the close agreement between simulation and HIL results confirms the practical feasibility, robustness, and real-time applicability of the proposed control framework for EV powertrain applications.