Loss optimizing control of a multiphase interleaving DC-DC converter for use in a hybrid electric vehicle drivetrain

In this paper, the application of a multiphase interleaving DC-DC converter in the drivetrain of an electric vehicle is studied. At first, a method for controlling the converter is proposed which ensures its operation under variable switching frequency and changing of the number of active phases. The implemented cascade control is designed with the help of a small signal model of the multiphase converter. The controller also features a nonlinear feedforward compensator to improve the transient performance. In the next step, different loss optimizing strategies are developed and discussed, based on the temperature-dependent loss model of the drivetrain. These strategies are to vary switching frequency, DC-link voltage and the number of active phases as well as a so-called passive mode operation. Finally, the efficiency difference between a conventional drivetrain and the modified one is presented which shows efficiency improvement especially at partial load. A test setup is also constructed for experimental results which will be presented at the end of this paper.