Hybrid Modulation Scheme with Current-Stress Optimization of DAB DC-DC Converter to Enhance Efficiency

Abstract

The increasing popularity of power electronic (PE) converters in different applications has led the research work to obtain higher efficiency and power density of the system. The dual active bridge (DAB) converter becomes very important in the domain of DC-DC isolated converters, due to its several advantages. Multiple research articles have studied the operation procedure of DAB converter, and proposed various modulation techniques for the same. Several phase shift modulation techniques have improved the operation of DAB for wide voltage and power range. However, at low power and wide voltage variation of converter, some limitations of those phase sift modulation techniques can be identified such as, low efficiency, hard switching operation, high peak and rms current of transformer, high computational effort etc. Targeting those issues, a hybrid modulation technique is proposed combining single phase shift and variable phase shift modulation techniques. The proposed modulation scheme a) optimizes the transformer peak current at its minimum value for full range of power, b) provides zero voltage switching (ZVS) operation for all operating conditions, c) ensures minimum voltage stress on switches, d) does not use any current sensor for the optimization process and e) operates with simplified control strategy which results low computational efforts. The optimization of peak current is achieved using two different methods, which are differential method and Lagrangian multiplier method. The optimization process is carried out for full range of voltage and power to ensure the ZVS operation for all operating conditions. All the claimed characteristics of the proposed modulation technique are verified through simulation and the experimental results derived from a hardware prototype.