The Application Of IGCT In Asynchronous Motor Direct Torque Control

With the rapid development of rail transportation, the study of high voltage, high current AC drive system is particularly important. Asynchronous Motor Vector control and Direct Torque Control laid the foundation of modern AC variable speed theory. Compared with the Vector Control system, Direct Torque Control system eliminates a lot of sectors such as vector transform, the amplitude calculation of the rotor flux and the position determination of the rotor flux, and it emphasizes the direct control of the flux and the torque, so the system is more simple and quick and it has a much better dynamic response ability and also reduces the effect of the parameters on control performance. In this paper, Simulink in Matlab is used to simulate and verify each model of the Direct Torque Control system, and the simulation of the whole Direct Torque Control system is also verified. Finally, a reliable and practical Direct Torque Control system simulation model is established.IGCT (Integrated Gate Commutated Thyristors, IGCT), which combines the advantages of GTO(Gate Turn-Off Thyristor, GTO) and IGBT(Insulated Gate Bipolar Transistor, IGBT), is evolved from GTO. It has the characteristics of high turn-off voltage, large turn-off current, high switching frequency, low losses and high reliability. These characteristics of IGCT is very suitable as the switching devices in an inverter circuit of an AC drive system with high voltage and high current. However, there is no models of IGCT in Simulink, so in this paper, a simulation model of IGCT based on the test circuit waveforms given by the company ABB is established in Simulink, and the model is tested according to ABB’s test circuit. Thus the simulation model is in line with IGCT devices.Finally, the IGCT simulation model is applied to the inverter circuit of the Direct Torque Control system. In the application process, the problem that the inverter circuit is not working properly is solved. While studying the operating state of the IGCT in the inverter circuit, the overload problem is also solved. In the end, by changing the parameters of the system and a series of simulation experiments, a Direct Torque Control scheme which is suitable to the IGCT devices is found.