Interface impedance consideration in the design of an input EMI filter for grid-tied PV micro-inverter

Inverters adopted in centralized PV power generation have inherent problem of islanding forcing the entire system shutdown and resulting in costs of downtime. Nowadays, the distributed systems using micro-inverters at each PV panel, has been an adequate method to address this issue. The major difference between the centralized inverters and the distributed micro-inverters reside in their rated power. However, they share a common issue of being generators of conducted EMI. This paper proposes an intermediate EMI filter design using impedance interactive approach at both PV-side and front-end DC converter interface. This method provides sufficient margin to ensure the converter stability at Maximum Power Point Tracking (MPPT) and satisfy the applicable EMC specifications. The experimental results show that the implementation of the EMI filter at the DC feed has effectively attenuated the EMI noise to an acceptable level, while providing good stability under the input voltage and load variations.