A Novel Direct Torque Control Strategy of Two-Level Voltage Source Inverters for Eliminating Common-Mode Voltage Spikes Caused by Dead-Time Effect

The traditional direct torque control (DTC) of two-level voltage source inverter-fed motor system can achieve evident reduction of common-mode voltage (CMV) if zero vectors are not used, as the amplitude of the CMV of the zero vector is much larger than that of the active vector. However, due to the influence of dead-time effect, zero vectors can still be generated during inverter commutation, resulting in CMV spikes. To eliminate the CMV spikes caused by dead-time effect, a novel DTC strategy is proposed in this article. Through the analysis of the voltage vector during the dead-time of the commutation process, the process of looking up the DTC switching table is modified, and a transient vector is inserted when necessary, so that no zero vector is generated during commutation. The proposed DTC strategy eliminates CMV spikes in a look-up table way, so that the simple control structure of traditional DTC is maintained, while neither modification of hardware circuit nor detection of current polarity are required. Experiments verified the effectiveness of the proposed strategy.