New generation of full low-floor trams: Control of wheel drives with permanent magnet synchronous motors

This paper presents a propulsion system concept for a new generation of full low-floor trams employing gearless wheel drives with surface-mounted permanent magnet synchronous motors (PMSM). The main attention is paid to the wheel drive control. The proposed control had to overcome two major problems: (i) oscillations of LC filters in traction converter dc-links, and (ii) load angle control due to required operation of PMSM with the load angle of 90° in order to fully utilize the PMSM capability. The drive operation in a very wide speed range in a field weakening and specifically the load angle limitation was a new problem for which we did not find any reference related to traction applications. Proper function of presented propulsion system and its control is verified by simulations of the tram drive prototype and by experiments made on both a small-scale wheel drive prototype of 10.7kW and developed tram ŠkODA ForCity.