Overview and Comparison of Modulation and Control Strategies for a Nonresonant Single-Phase Dual-Active-Bridge DC–DC Converter

Abstract

The nonresonant single-phase dual-active-bridge (NSDAB) dc-dc converter has been increasingly adopted for isolated dc-dc power conversion systems. Over the past few years, significant research has been carried out to address the technical challenges associated with modulations and controls of the NSDAB dc-dc converter. The aim of this paper is to review and compare these recent state-of-the-art modulation and control strategies. First, the modulation strategies for the NSDAB dc-dc converter are analyzed. All possible phase-shift patterns are demonstrated, and the correlation analysis of the typical phases-shift modulation methods for the NSDAB dc-dc converter is presented. Then, an overview of steady-state efficiency-optimization strategies is discussed for the NSDAB dc-dc converter. Moreover, a review of optimized techniques for dynamic responses is also provided. For both the efficiency and dynamic optimizations, thorough comparisons and recommendations are provided in this paper. Finally, to improve both steady-state and transient performances, a combination approach to optimize both the efficiency and dynamics for an NSDAB dc-dc converter based on the reviewed methods is presented in this paper. Index Terms-Current feedback control, current stress, dualactive-bridge (DAB) converter, dynamic performances, efficiency, observer-based control, power control, power losses, reactive power. NOMENCLATURENSDAB Nonresonant single-phase dual-active-bridge. EV Electrical vehicle. SST Solid-state transformer. BTB Back-to-back. MMDCT Modular multilevel dc-link solid-state transformer. SPS Single-phase-shift. ZVS Zero-voltage-switching. DPS Dual-phase-shift. EPS Extended-phase-shift. TPS Triple-phase-shift.

Enhanced DAB for Efficiency Preservation Using Adjustable-Tap High-Frequency Transformer

“…This tap was selected as it provides the step up required for nominal operation of the converter between 40-V and 400-V DC-links, under which the transformer core loss is small. Furthermore, we could compare this tap with higher (11,12) and lower (9) taps in the E-DAB, for demonstrating the performance at both ranges. In Fig.…”

“…Among them, increasing the dead-time could improve the soft-switching at light loads at the cost of degrading the efficiency at heavy loads; moreover, when the inductor current reaches zero, increasing dead-time does not help at all, leading to more losses [9]. Various modulation schemes could also broaden the region for softswitching [9]- [12], but the laborious calculations involved in those methods are difficult to be performed at high switching frequency due to the limited computation and time-resolution in controllers and drivers. Another solution is to utilize resonance to extend the soft-switching region by adding extra components, passive or active (not lossless), which add to the design size and complexity [10], [12], [13] and lead to electromagnetic interference issues as the increased gain is based on frequency modulation [14].…”

“…Various modulation schemes could also broaden the region for softswitching [9]- [12], but the laborious calculations involved in those methods are difficult to be performed at high switching frequency due to the limited computation and time-resolution in controllers and drivers. Another solution is to utilize resonance to extend the soft-switching region by adding extra components, passive or active (not lossless), which add to the design size and complexity [10], [12], [13] and lead to electromagnetic interference issues as the increased gain is based on frequency modulation [14]. DC blocking capacitor together with a new modulation scheme is proposed in [15] and the method could successfully increase efficiency for voltage gains around 2 p.u.…”

A Tutorial and Review Discussion of Modulation, Control and Tuning of High-Performance DC-DC Converters Based on Small-Signal and Large-Signal Approaches

“…A triple phase shift modulation technique can offer three degrees of freedom for further optimization [38]. A comprehensive review of various fixedfrequency control methods for dual active bridge converters is presented in [39], [40].…”

“…3) Set the dc gain k c of the compensator as k c = ω c /k g , where ω c is the crossover radian frequency. Here k c can be computed using the frequency response of the loop transfer function in (40) at ω = ω c under perfect polezero compensation. The frequency response can be written as…”