Multilevel Diode-Clamped Inverter Fed IPMSM Drive for Electric Traction

The analysis of two, three and five-level diode-clamped inverter fed Interior Permanent Magnet Synchronous Motor drive for Electric Traction application is presented. The drive has been controlled by Direct Torque Controlled Carrier Based Space Vector Pulse width Modulation (DTC-CBSVPWM). DTC is a precise controller for permanent magnet synchronous motor (PMSM) owing to its robust and fast torque response for steady-state as well as transient conditions. The basic drawback of DTC is due to high ripple content in stator current, and torque due to the application of same active voltage vector during the entire sample period. It is resolved by using an appropriate modulation technique. Space Vector Modulation (SVM) synthesis the voltage vector gives superior performance, but calculation of angle and sector is complex. A simplified version, unified voltage modulation or carrier based space vector pulse width modulation is described. The voltage modulation task is simplified by synthesizing inverter output voltage directly with the effective times. The actual gating signals of each inverter arm can be simply deduced by means of effective time relocation algorithm.