No-load Control Strategy of Three-Phase Interleaved LLC Based on Phase-Shedding

The three-phase interleaved LLC offers advantages such as high power density and low switching loss. However, it faces challenges in maintaining voltage gain stability under no-load or extremely light load conditions due to the influence of parasitic capacitance. To address this issue, this paper proposes a phase-shedding control strategy for stabilizing the output voltage during no-load conditions. The remaining two-phase interleaved angle is maintained at 120°to operate in full-bridge LLC mode. By employing Fundamental Harmonic Approximation(FHA), an equivalent circuit model and DC gain that consider parasitic capacitance are derived for both the three-phase operation mode and two-phase operation mode. A simulation model is developed using Matlab/Simulink software to analyze these modes under no-load conditions. Experimental results validate the rationality of the proposed phase-shedding control strategy.