Busbar Design for Distributed DC-Link Capacitor Banks for Traction Applications

High power density is an important requirement for traction motor drives as transportation systems continue their electrification trends. Increasing power density requires a system-level approach addressing all inverter components; particularly, power modules, thermal management system, and dc-link capacitor bank. This paper focuses on designing a distributed dc-link capacitor bank using multi-layer series-connected ceramic capacitors (MLSCs) which have higher operating temperature, lower ESL and lower volume than film capacitors. The paper addresses the design of a busbar assembly connecting several MLSCs to the inverter power modules and the power source. The main design goals are distributing the capacitors across the power modules to provide a short path to high-frequency current components, minimizing parasitic inductances, and achieving similar current profiles among all MLSCs. ANSYS™ Q3D simulations are used to evaluate the busbar current density. The impedance as function of frequency is measured on the prototyped busbar assembly. Experimental tests verify the proposed design ideas.