What are the sources of conducted noise at the EPS battery interface?

Conducted noise at the EPS battery interface mainly originates from two directions: first, the switching noise of the internal inverter and DC/DC converter of the EPS, which is conducted in reverse to the battery port through the DC bus; second, the high-frequency ripple generated on the connection line by fluctuations in the battery's internal resistance or changes in charging and discharging current. This noise exists in both common-mode and differential-mode forms. Common-mode noise is mainly generated by the inverter bridge's high dv/dt forming a loop with the battery's negative terminal (usually also the chassis ground) through parasitic capacitance; differential-mode noise exists directly between the battery's positive and negative terminals. Furthermore, when the battery cable is long, it acts as an antenna, receiving spatial interference and conducting it into the EPS. Therefore, an EMI filter must be installed at the battery interface to prevent internal noise from interfering with the battery management system (BMS) and to suppress external noise intrusion.