Publications

Abstract not provided.

Abstract not provided.

Abstract not provided.

This paper presents a new high gain, multilevel, bidirectional DC-DC converter for interfacing battery energy storage systems (BESS) with the distribution grid. The proposed topology employs a current-fed structure on the low-voltage (LV) BESS side to obtain high voltage gain during battery-to-grid mode of operation without requiring a large turns ratio isolation transformer. The high-voltage (HV) side of the converter is a voltage-doubler network comprising two half-bridge circuits with an intermediary bidirectional switch that re-configures the two bridges in series connection to enhance the boost ratio. A seamless commutation of the transformer leakage inductor current is ensured by the phase-shift modulation of HV side devices. The modulating duty cycle of the intermediary bidirectional devices generates a multilevel voltage of twice the switching frequency at the grid-side dc link, which significantly reduces the filter size. The presented modulation strategy ensures zero current switching (ZCS) of the LV devices and zero voltage switching (ZVS) of the HV devices to achieve a high power conversion efficiency. Design and operation of the proposed converter is explained with modal analysis, and further verified by detailed simulation results.

This paper presents an isolated bidirectional dc/dc converter for battery energy storage applications. Two main features of the proposed circuit topology are high voltage-conversion ratio and reduced battery current ripple. The primary side circuit is a quasi-switched-capacitor circuit with reduced voltage stress on switching devices and a 3:1 voltage step down ratio, which reduces the turns ratio of the transformer to 6:1:1. The secondary side circuit has an interleaved operation by utilizing the split magnetizing inductance of the transformer, which not only helps to increase the step down ratio but also reduces the battery current ripple. Similar to the dual-active-bridge circuit, the phase shift control is implemented to regulate the operation power of the circuit. A 1-kW, 300-kHz, 380-420 V/20-33 V GaN-based circuit prototype is currently under fabrication. The preliminary test results are presented.