Characterization of High Voltage EMC filters for Electric Vehicles charging applications

Filters for Electromagnetic Interference (EMI) are necessary since they can suppress the noise coming from switching-mode power supplies (SMPS). A key component of such filters are common mode chokes (CMCs) and film filter capacitors. In Electric Vehicles (EVs) charging applications such as On-Board Chargers (OBCs), the power EMC filters are located at the input side, the AC High Voltage (HV) filter and output side DC HV filter. In particular, the second one is the device that interfaces the charger with the Li-ion HV vehicle battery. CISPR25 regulates the EMI noise level on the HV port, however car-makers can have their own EMC regulations with more challenging limits with respect to the international norm. Prediction of the performances of the filter is necessary to avoid time-consuming hit-and-trial set of measurements in anechoic chambers to find root cause of filter failure. This paper deals with the simulation performed with Ansys HFSS and characterization of an HV DC filter for a 22kW/800V OBC mounted on a high-end car. Emphasis is put on dealing with chassis enclosure, necessary to shield filter as well for cooling purposes, which might alter filter performances.