A Dual Phase-Optimized Strategy to Reduce Second-Carrier Harmonic Current for DAB-Based Three-Phase Single-Stage AC–DC Converter

The dual-active-bridge-based three-phase singlestage ac-dc converter has gained significant attention in power conversion applications due to its superior efficiency and compact volume. However, one potential problem is that the dc-side total capacitor ripple current (TCRC) is considerable, which induces capacitor heating and compromises converter reliability. This paper presents a Fourier analysis based dual phase-optimized strategy that considers the constraints of phase shift angle (PSA) in DAB converter, aiming to minimize the root mean square (RMS) of the lowest frequency harmonic current (LFHC) in TCRC. First, a mathematical model is developed for the single phase (1P) converter, comprising a frequency domain analytical expression of the ripple current and the PSA adjustable range of 1P converter. Subsequently, using the developed model, the initial phase relationships among the three 1P converters are adjusted at the minimum symmetrical interval (30-degree) of the power grid cycle. Concurrently, the PSA of converters are dynamically optimized at each switching cycle, thereby achieving maximal attenuation of the LFHC. Experimental validation using a 3×1.1kW prototype demonstrates a 90% reduction in the RMS of the LFHC under rated conditions.