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A Three-Port Three-Phase DC-AC Topology Based Multi-Functional Grid-Connected Inverter with Enhanced Conversion Efficiency

A novel multi-functional grid-connected inverter (MFGCI), composed of a three-port three-phase DC/AC converter and a front-end DC/DC converter, is investigated and evaluated in this paper. A low voltage DC source can exchange most energy with the AC grid only through the DC/AC converter and only partial power needs to be processed by the DC/DC converter. Therefore, power conversion stages can be reduced and overall conversion efficiency is improved. To make sure most active power can be transferred directly from the DC source to the AC grid within single-stage conversion, a modified SVPWM strategy is adopted and evaluated experimentally. Impact factors on the single-stage power transferring when the MFGCI compensates reactive and harmonic currents for power quality enhancement is analyzed in detail as well. Compared with traditional solutions, the presented MFGCI can realize active power delivery with high efficiency in addition to enhancing power quality. Experimental results with a 5kVA inverter prototype are provided to verify the feasibility and effectiveness of the three-port three-phase DC/AC converter-based MFGCI.