Propulsion System Based on the NPC Multi-Source Inverter for Battery Hybrid Trams: Experimental Validation

Abstract

Hybrid tram vehicles with a connection to the overhead line and onboard batteries present many advantages, including effective braking energy recovery, reduced current absorption from the overhead wire, and partial catenary-free operation. For their connection to the vehicle dc bus, the batteries require bulky and heavy dc/dc converters that are sized for the peak power rating of the storage system. This paper presents the experimental validation of a non-conventional battery hybrid propulsion system employing the NPC Multi-Source Inverter. The Multi-Source Inverter provides an additional connection between the battery and the traction motors and can thus be used to partly bypass the dc/dc converter and reduce its power rating. The experiments on a small-scale lab prototype validate the envisioned control of the architecture and attest to its potential of reducing significantly the peak current rating of the dc/dc converter, with expected savings in terms of weight, volume, and power losses.