Research on Three-Parameter Modulation Strategy for Phase-Shifted Full-Bridge Converters Based on Asymmetric Duty Cycle

Abstract

The peak-to-peak current in dual-active-bridge (DAB) converters significantly impacts conversion efficiency. Under conventional single-phase-shift (SPS) modulation, efficiency degrades at high voltage conversion ratios. This paper proposes an asymmetric duty cycle-based triple-parameter modulation (TPADM) strategy by introducing asymmetric phase-shift angles to expand modulation flexibility. First, the operating principle of TPADM is analyzed, identifying four distinct modes based on switching sequences. Second, steady-state characteristics (inductor current, power transfer) are derived via time-domain analysis for all modes. Third, a piecewise optimization method using Karush-Kuhn-Tucker (KKT) conditions minimizes peak-to-peak current, maximizing efficiency. Finally, experimental results validate the superiority of TPADM over SPS in reducing current stress and improving efficiency across wide voltage ranges.