Abstract
Keywords - Starter Generator, Hybrid Car, Inverter, Energy Storage, Converter
Abstract - With the background of the rising crude oil prices and the worldwide increasing traffic density - the reduction of the fuel consumption and the exhaust emission became one of the most important tasks of the automotive engineering. Therefore, a further optimization of the powertrain is urgently necessary. This can be achieved very well by the combination of the combustion engine with a starter generator. There are various new functions available, which will lead to a reduction of the fuel consumption and exhaust gas and will further increase the traveling comfort and the driving dynamics. Additionally to these advantages, the starter generator will be able to cover the constantly growing onboard electrical power demand in future. Up to now, standard generator systems are already loaded to their limits. The starter generator eliminates the existing power limitation and convinces furthermore with excellent system efficiency of more than 84% in a wide working range.
This publication starts with an overview about the starter generator systems and compares the usable functions. The system of choice will be determined by the demanded functions. The belt driven side mounted starter generator for instance, which replaces the standard lundell alternator is an effective solution to provide start/stop functions. Due to the wider allowed speed range, it may be also possible to vary the gear ratio between the starter generator and the powertrain depending on the desired mode of operation. For higher output power with engine support (boost-function), it is suitable to integrate the starter generator directly into the powertrain.
Below, the components of the starter generator will be described in detail. The pros and cons when using induction-, synchronous- and reluctance machine are compared to each other. Different procedures to control these machines with a two-level voltage source inverter are shown. For the use of a starter generator, an effective energy storage system with sufficient charge cycle resistance is necessary. For this, different storage technologies are compared to each other. In order to improve energy storage many specialists regard combinations of different energy storage technologies as promising. If the advantages of two different energy storage systems will be used, two electrical board-nets are necessary and its energy exchange by converters has to be controlled. So with an energy management system a careful use of the battery can be achieved by the combination of a battery with double layer capacitors. This enables the use of the lead-acid battery for hybrid vehicles.