Steady-State Model-Derived Multivariable Loss Optimization for Triple Active C³L³ Resonant Converter

Conventional pulsewidth modulation (PWM)-controlled multiport converters (MPCs) portray a narrow soft-switching range and higher rms currents at light-load and nonunity gain conditions, leading to degraded end-to-end efficiency. Focusing on efficiency targeted limitations of conventional MPCs employed in electric vehicle (EV) charging applications, a comprehensive loss optimization study of a resonant triple active (TA) C^{3}L^{3} converter is presented in this article. The multivariable loss objective function is developed with constraints imposed to ensure zero voltage switching (ZVS)- and synchronous rectification (SR)-based soft switching for all the corner conditions, by investigating the scope of optimal hybrid phase-duty-frequency modulation techniques. Based on the performance metrics obtained by employing hybrid modulation schemes, an algorithm is introduced to enable the selection of least algorithmic complexity focused on digital implementation constraints that yields a steady-state operating zone matrix for different loading and port gain conditions. To benchmark the converter performance and the optimal modulation scheme selection criteria, an all-GaN-based 2-kW prototype is developed for a resonant frequency of 500 kHz. Experimental validations for various loading conditions are presented for a wide-gain bidirectional operation (400/500-600/24-28 V), that yield an efficiency improvement of 1.2% as compared with conventional solutions, while portraying a peak converter efficiency of 97.42%.