A Six Legs Buck-boost Interleaved Converter for KERS Application

Abstract

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  motor-generator   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.