A hysteresis current control for parallel connected line-side converters of an inverter locomotive

Inverter locomotives have become a standard solution in modern rail transportation. Up to now the suboscillation method for pulsewidth modulation has been widely used for the control of their line-side converters. Future requirements such as faster power control, well defined response in the case of a distorted line voltage or the installation of active filters demand for new modulation schemes. The authors introduce a modulation method which is based on a hysteresis current control. It is suited for parallel connected voltage source inverters and combines the advantages of both the hysteresis control and the suboscillation method. This includes the dynamic performance as well as the staggered firing of the converters in order to reduce the total harmonic content of the line current. The design of this scheme, which is especially suited for locomotives with an active filter, is explained and a comparison with the suboscillation method is presented. All results are based on computer simulations