Multi-Source Inverter for Power-Split Hybrid Electric Powertrains

Some electrified vehicles, for example the Toyota Prius, integrate a dc-dc converter between the battery pack and the traction inverter to increase the powertrain efficiency. However, adding this extra converter adversely affects the cost and power density of the powertrain due to the additional components, such as the switches and the inductor, that are expensive and heavy in high-power converters. The concept of the multi-source inverter was previously introduced as an alternative solution to reduce the power rating of the dc-dc converter while keeping similar powertrain performance. In this paper, the implementation of the multisource inverter in a hybrid power-split powertrain is discussed. The operating modes during both dc-ac and ac-dc conversions are detailed and a prototype is experimentally tested with a load. New control strategies of the proposed powertrain show that three out of five operating modes bring new opportunities in terms of battery charging and power rating reduction of the dc-dc converter. A vehicle-level simulation model is developed in MATLAB/Simulink to quantify the benefits of the proposed topology. Simulations are performed for four drive cycles to compare the power profile of the dc-dc converter of the suggested powertrain with the Toyota Prius. The average power transferred by the dc-dc converter can be reduced by up to 25% in most drive cycles tested.