Abstract

This paper proposes a bidirectional dc–dc converter for residential micro-grid applications. The proposed converter can operate over an input voltage range that overlaps the output voltage range. This converter uses two snubber capacitors to reduce the switch turn-off losses, a dc-blocking capacitor to reduce the input/output filter size, and a 1:1 transformer to reduce core loss. The windings of the transformer are connected in parallel and in reverse-coupled configuration to suppress magnetic flux swing in the core. Zero-voltage turn-on of the switch is achieved by operating the converter in discontinuous conduction mode. The experimental converter was designed to operate at a switching frequency of 40–210 kHz, an input voltage of 48 V, an output voltage of 36–60 V, and an output power of 50–500 W. The power conversion efficiency for boost conversion to 60 V was ≥98.3% in the entire power range. The efficiency for buck conversion to 36 V was ≥98.4% in the entire power range. The output voltage ripple at full load was <3.59 Vp.p for boost conversion (60 V) and 1.35 Vp.p for buck conversion (36 V) with the reduced input/output filter. The experimental results indicate that the proposed converter is well-suited to smart-grid energy storage systems that require high efficiency, small size, and overlapping input and output voltage ranges.

Highlights

  • Distributed generation (DG) is the future of energy systems that provide system reliability and flexibility within local electric loads instead of centralized generation

  • The combined half-bridge (CHB) converter (Figure 2a) has two power stages consisting of two half-bridge converters and a dc link capacitor Clink that operates as an energy-transfer unit [6,7,8]

  • An additional half-bridge converter can be connected to the Clink in order to use the converter as multiple inputs or outputs

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Summary

Introduction

Distributed generation (DG) is the future of energy systems that provide system reliability and flexibility within local electric loads instead of centralized generation. The CHB converter (Figure 2a) has two power stages consisting of two half-bridge converters and a dc link capacitor Clink that operates as an energy-transfer unit [6,7,8]. The CBB converter [9,10,11,12,13,14] (Figure 2b) consists of one inductor and four switches. CBB converter can bebeimplemented inin a switches on the right leg are used for the boost operation. 2) the the loss and and conditions, current ripple in the inductor causes core loss increases output voltage ripple; and (3). Switching frequency because the 1:1 transformer and Cs reduce the core loss and switching loss

Circuit
42–58.8 Vduty a given irradiation converterwith of the system adjusts the
Maximum
Circuit Structure
Reduction of Core Loss
Principle of Operation
Voltage
Output Voltage Ripple
Design Considerations
Digital Controller
Experimental Results
14. Waveforms of iof
12.6 W in the conventional
Conclusions

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