Power electronics for hybrid-drive systems

Today many car manufacturers consider automobiles with combined drive systems consisting of combustion engine and electrical machine as a trend-setting concept. These hybrid vehicles are characterized by its good driving dynamics, economical fuel consumption and environmental-friendliness. Depending on performance class and drive structure, there are different systems available: micro-hybrid, mild-hybrid, full-hybrid, series-hybrid and also series/parallel-hybrid. Due to this large variety of drive systems Siemens VDO Automotive has decided to develop a hybrid electric vehicle (HEV) platform with a modular concept. This concept is useful for all of these different hybrid systems. Electronic converters have a significant role in this modular platform, because the overall power between the board-net and electric machine must be regulated by a DC/AC converter. To implement the motor operation together with the generator operation the converter must be able to operate bi-directionally. This enables system functions like electric drive, combustion engine-start, starting support, regenerative braking and start/stop functions in city traffic. The first steps of the modular platform were realized with practical project experience together with car manufacturers. This paper gives a rough overview about hybrid systems and shows the development status of power electronic converters.