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While searching for transformerless inverters in the IEEE site, most of them seem to be about grid connected Photovoltaic inverters. Removing transformers will increase the efficiency at the cost of galvanic non-isolation between the ac and dc parts which might cause dangerous dc injection currents. Is this why battery inverters do not have transformerless topologies?

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  • \$\begingroup\$ The likely don't have it because the cost never outweight the little benefits (if any) \$\endgroup\$ – PlasmaHH Jan 15 '16 at 10:33
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Grid-tied PV systems use a high DC bus voltage — higher than the peak AC voltage — which means that it is simple to use a single set of switching elements to turn this into the required AC output.

Battery-based systems generally use a much lower DC bus voltage. In order to make a transformerless inverter, you'd need to first boost the bus voltage to the higher value using one set of switching elements (DC-DC converter), and then have another set of switching elements to do the waveform generation. It's much simpler, and generally just as efficient overall, to do the waveform generation at the battery bus voltage and use a transformer to boost it to the line level.

In addition, in a UPS application, you can use that same transformer and switching elements to charge the battery, which reduces the overall system cost.

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  • \$\begingroup\$ so is it completely useless to replace the transformer with boost converters in UPS applications? i was about to do a project on transformerless ups but now i guess i have to change my project title as eliminating ground leakage current in pv cells.. so i'll use a 12 volt 200 mA 2.4 watts solar panel coupled with a suitable boost converter followed by an inverter topology like h5. \$\endgroup\$ – Mathav Raj Jan 18 '16 at 16:50
  • \$\begingroup\$ @Olin Lathrop will a "12 volt 200 mA 2.4 watts solar panel coupled with a suitable boost converter followed by an inverter topology like h5" circuit work for a demo project i'm about to do on suppression of leakage current in transformerless inverters? \$\endgroup\$ – Mathav Raj Jan 21 '16 at 15:02

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