Electric Power Recirculation in Multimode Power-Split HEVs: Implications for Transmission Design

In multimode power-split hybrid electric vehicles, the full installed onboard power cannot be assumed to be always available at the wheels, because power recirculation within the electric unit may overload the motor-generators beyond their maximum power limit. This paper investigates this issue through a generalized parametric framework in which the same functional parameters govern both electric machines power and planetary gearing synthesis. The Chevrolet Volt powertrain is adopted as a case study. Since the baseline transmission cannot make the full installed power effectively available over the whole vehicle speed range due to electric power recirculation, an alternative solution is identified through a CVU recirculation chart and its planetary gearing synthesis is derived through a PSU design chart.