Current and Voltage Harmonics in the Powertrain of Electric Vehicles

Abstract

Switching electronics, such as the drive inverter, generate significant voltage and current harmonics with frequencies as low as a few kilohertz which are propagated throughout the complete electric powertrain and all connected components. With amplitudes up to several volts and dozens of amperes, such harmonics can cause significant problems and lead to performance limitations or even component failures. In order to maintain the quality of the dc-link voltage and guarantee the sound interaction of all components, power electronics must therefore be equipped with filter capacitors damping these harmonics. However, the filter stages account for a large part of the overall component cost and volume. Usually, the required dc-link filters are designed independently for each component on its own without taking into account the configuration of the complete powertrain. This, however, might result in undersizing of filters and possible system failures or contrary to that to oversized and expensive components. In this study, an analytic approach for the computation of the electric harmonics generated by the drive unit of a hybrid fuel cell vehicle will be derived and validated using measurement data. Using this model, the significance of the electric harmonics for the design of the powertrain as well as the sizing process of the filter capacitors will be analyzed.