Reduction of Conducted EMI on Parallel Operation for AC Module Inverters

An AC photovoltaic module system is recognized as a novel photovoltaic power generating system. However, serious EMI troubles caused by the photovoltaic inverters are suspected, because many inverters operate simultaneously. This paper discusses common-mode conducted EMI and its a reduction method of parallel operation of grid connectable inverters. In the case of parallel operation of inverters, the characteristic impedance of the series resonant circuit in a common-mode equivalent circuit decreases and it increases a noise voltage on grid lines. When a common-mode inductor is connected in series to the total output line, the reduction effect of common-mode noise is larger compared to when individual inductors are connected to each inverter output.

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