A six legs buck-boost interleaved converter for KERS application

This paper addresses the design of a bi-directional DC/DC power converter to interface a supercapacitor bank and a motor-generator unit. The design is based on an interleaved six legs topology in which the current is shared among six inductors to minimize their weight and cost, allowing, besides, a low switching frequency to lessen switching losses. The converter is conceived to be employed in an electric Kinetic Energy Recovery System for Internal Combustion Engine Vehicles. The system makes use of a supercapacitor as a storage system, and a motorgenerator unit connected to the drive shaft for vehicle acceleration and braking. The system uses available commercial devices, thus obtaining a cheap and high-efficiency conversion chain. It is shown how the design criteria differ from traditional interleaved converters. The same topology allows minimizing the input and output ripple and improving the reliability in case of fault as well. Losses are reduced both by sharing the currents and by a suitable control strategy, which allows more converters to be connected in parallel to increase the delivered power. Results, given in simulation, assess the stability and dynamic performance of the conversion circuit, showing a low current and voltage ripple in all operating conditions.