1. APPLICATION AND STABILITY ANALYSIS OF A NOVEL DIGITAL ACTIVE
EMI FILTER USED IN A GRID-TIED PV MICRO-INVERTER MODULE
ABSTRACT:
This paper presents a novel technique to suppress common-mode electromagnetic interference (EMI)
using a digital active EMI filter (DAEF). The DAEF control technique is concurrently implemented with a
digital controller of a grid-tied photovoltaic microinverter. A brief description of the microinverter
architecture and its inverter circuit is illustrated. The inverter stability is investigated using the overall
transfer function. Accordingly, the system compensation is designed based on the direct quadrant (DQ)
reference frame control technique. Finally, the proposed digital controller is tested on a grid-connected 200W dc-ac microinverter. The experiment results validate the effectiveness of the proposed technique.
Compared with the conventional passive EMI filter, the proposed digital controller can achieve an
equivalent or better performance in terms of EMI suppression and maintain stability within the operation
bandwidth. Therefore, the embedded DAEF can significantly reduce the size, cost, and space of the overall
power inverter printed circuit board without the need of a conventional passive EMI filter.