Analysis and Decoupling of Multisource EMI in High-Power PV Inverter

The photovoltaic (PV) inverter contains four types of converters, the active neutral point clamped (ANPC) inverter, the boost converter, the ac auxiliary (ACAUX) flyback converter, and the dc auxiliary (DCAUX) flyback converter. The coupling of single-source electromagnetic interference (EMI) generated by these different converters forms multisource EMI. The contributions of each single-source EMI are hidden in the coupled multisource EMI. Therefore, the modeling and suppression may not be highly targeted. In this article, the decoupling method of multisource EMI in high-power PV inverter is investigated. First, the studied PV inverter and its multisource EMI are analyzed. Second, the LF multisource EMI is decoupled based on the discrete spectrum. Third, the HF multisource EMI is decoupled based on the time-frequency matrix. Finally, the proposed decoupling method is implemented to both LF and HF EMI of a 100 kW PV inverter. The targeted suppression strategies are adopted based on the decoupled single-source EMI. The peak EMI spectra dominated by DCAUX, ACAUX, and ANPC are decreased by 18, 10, and 7 dB, respectively. The results validate the correctness of the proposed decoupling method.