A novel phase-shift bidirectional DC-DC converter with an extended high-efficiency range for 20 kVA solid state transformer

This paper proposes a novel phase-shift dual-half-bridge converter with an adaptive inductor. This converter will be used as a high frequency transformer isolated dc-dc stage of a 20 kVA single phase solid state transformer (SST) in the future renewable electric energy delivery and management Systems. By utilizing an adaptive inductor as the commutation inductor, the proposed converter can control not only the phase shift but also the commutation inductance so that the circulating energy can be optimized to maintain zero-voltage-switching operation at light load. In addition, the conduction losses and current stress at heavy load can be reduced as well. As a result, the efficiency at both light and heavy load, compared with conventional phase-shift DHB converter with fixed commutation inductance, can be significantly improved. Therefore, the extended high-efficiency range of SST can be achieved, which is critical for the SST application due to its wide load range, continuous operation, and the rising energy cost. The theoretical analysis is presented and validated by the experimental results on a 50 kHz, 1 kW dc-dc converter module.