Ripple Test and Impedance Analysis Procedures for Normative Evaluation of HVDC Busses In Evs

This paper describes the importance of impedance analysis of individual, as well as connected components in a high voltage DC bus and best test practices to comply with normative standards. The HVDC bus is the “backbone” in any battery powered EV. It provides power transfer from battery to e-drives and supplies power to modules for heating/cooling, on-bord charging and other auxiliaries. However, voltage and current on the DC bus also comprise of AC components generated by inverters and other power consuming components. Voltage ripples may result in high current ripples on the DC bus, especially when ripple frequencies coincide with any modules’ low impedance resonance frequencies. These resonant current ripples can result in thermal destruction of power lines and modules, as well as in degradation of battery, e-motors and inverters alike. Consequently, such module and system ripple tests are required in OEM's and ISO test norms.