Reduction Methods of Conducted EMI Noise on Parallel Operation for AC Module Inverters

An AC photovoltaic module system consists of a photovoltaic module and a voltage source inverter, and a number of the ac modules are connected in parallel. The inverters have to be connected to a photovoltaic module on the roof of a residence, therefore it is necessary to make it small and light weight. Thus, the flyback inverter is used for the AC module system in this paper. The advantage of the inverters is that stable current injection into a utility line can be achieved without using the inter-linkage inductor. When the common-mode filter is connected in series to the total output of the inverters, the reduction effect of the common-mode noise is greater than when individual filters are connected to each inverter output. This paper discusses common- and differential-mode EMI noise for AC module inverters and shows an installation point for a common- and differential-mode filter to reduce the noise voltage.