Full speed range induction motor indirect rotor field oriented control for high speed traction applications

Nowadays, with the demand of high speed traction applications, for example traditional locomotive or Electric Multiple Units, medium-voltage high power AC drives are required. In the high power AC drives, the switch frequency of the devices has to be limited in order to reduce the loss of the power semiconductor devices. The modulation strategy is made up of asynchronous modulation, synchronous modulation and single pulse modulation in the full speed range. In this case, the traction motors, usually are induction motors, are running at a low modulation frequency ratio and even square wave mode in high speed situation. The induction motor control in single wave mode and the current harmonic elimination at low modulation frequency ratio should be taken into account. This paper presents a unified control strategy and modulation strategy for induction motor indirect rotor field-oriented control with a two-level voltage source inverter.