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Grid-connected transformerless single-phase photovoltaic inverters: an evaluation on DC current injection and PV array voltage fluctuation

Morris, Claude (2009) Grid-connected transformerless single-phase photovoltaic inverters: an evaluation on DC current injection and PV array voltage fluctuation. Other thesis, Murdoch University.


A number of political, environmental and technical factors have resulted in the increase of implementation of renewable technology including grid connected photovoltaic inverters. As a result, new topologies for grid connected inverters providing higher efficiencies and lower manufacturing costs have been developed. In particular, designs utilising transformerless topologies have steadily increased. While there are clear associated advantages of implementing these new transformerless topologies, new potential issues such as DC current injection and capacitive leakage currents are introduced. Part A of this report presents a clearly defined test circuit setup and procedure for testing DC current injection for grid-connected single-phase photovoltaic inverters implementing both transformerless and high frequency transformer topologies. The results demonstrated that the test circuit setup and testing procedure is suitable for inclusion in a future amendment to AS4777.2. It is however proposed that before these amendments are recommended, further investigation is required to determine what power levels all inverters are required to be tested at and how many tests per inverter are required. Part B of this report defines and models a variety of transformerless inverter topologies, switching schemes and output filter configurations and clearly defines their operation. All of these various models have been simulated to determine which designs are suitable for applications in regards to reducing capacitive leakage currents in an effort to eliminate potential risks to users and to ensure electromagnetic compatability. Two commercially available and one anonymous Grid-connected Transformerless Single-phase Photovoltaic Inverter models utilising a selection of the simulated topologies and switching schemes were experimentally tested to verify simulated results.

Item Type: Thesis (Other)
Murdoch Affiliation: School of Engineering and Energy
Supervisor(s): Calais, Martina
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