Comparison of topologies to drive the machine of an automotive electrical power steering with higher voltage levels

A comparison between different inverter topologies has been carried out and their suitability assessed for application as a driver unit of the asynchronous machine for an automotive electrical power steering system. The proposed topologies provide higher voltage levels to the machine compared to the voltage levels obtained directly from the automotive electrical power net and also provide a reduced slope of the input current drawn from the automotive electrical power net by utilizing an additional double layer capacitor as integrated energy storage device. The comparison includes an inverter with additional boost converter, an inverter with integrated boost converter and a third topology with integrated boost converter and modified driving scheme. A detailed analysis has been performed to determine the overall losses and most suitable topologies have been built and tested to prove theoretical predictions. Experimental results are in good correlation with theoretical predictions.