Sizing DC-link Capacitors in Complex Automotive High Voltage Systems

In the high voltage (HV) supply systems of battery electric vehicles (BEV) current oscillations as conducted disturbances are present due to the switching operation of the power electronic devices. These oscillations have a great impact on the power quality and influences the availability and efficiency of the system operation. The enhanced number of power electronics interfaced devices connected to the high voltage supply system are improving the complexity and possibility of appearance of undesired mutual effects between the high-voltage devices. That implies that the proper design parameter choice, such as the DC- link capacitor sizing, to guarantee the limits on voltage ripple is becoming a main integration challenge. In this work, a summary of the requirements for the automotive HV supply systems for the voltage and current ripple in the frequency range up to 150 kHz is shown. The critical design and integration challenges with respect to the requirements on the voltage ripple are presented. As well as the evaluation of the relevant electrical characteristics on device and system level to guarantee the reliable and stable operation of the automotive HV supply system are highlighted. As main contribution, a methodology is shown to size DC-link capacitors of traction inverters to guarantee system level voltage ripple limits in complex vehicular architectures. For the proposed methods simulation models and test configurations are shown to validate the design methodology.