Abstract：Current coupling among the transformerless non-isolated grid-connected inverter modules is researched with the current decoupling condition given by analyzing the equivalent operation modes of the inverters mentioned with different topologies and modulations. Analysis reveals that the bipolar PWM inverters can be operated in parallel with current decoupling naturally. Unipolar double frequency PWM inverters can be operated in parallel with harmonic current of switching frequency coupled and fundamental components decoupled. Unipolar PWM inverters can not be operated in parallel with current coupling. Inverters with common-mode current eliminating cells, such as H5 and HERIC topology, can achieve current decoupling naturally in parallel operation. Grid-connected photovoltaic power systems with inverter modules mentioned are built respectively. And experimental results verify the analysis.
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2012, Vol. 27 
