A Dynamic Analysis of SVM Based Three-Level NPC for a 3-Phase Induction Motor

Multilevel inverters have wide scope of research in the area of drives applications from few decades. Due to its unique advantages the neutral-point clamped (NPC) inverter have taken and due to it's less harmonic content in outputs at higher switching frequencies, space vector pulse-width modulation (SV-PWM/SVM)have chosen in this paper for the analysis purpose. This paper presents a SVPWM based three-level NPC inverter with one of asymmetrical switching sequence. The given strategy helps in reduction of number of converter switching sequences at high switching frequency range, compared with the conventional SV-PWM scheme, and gives a good dynamic response when it is applied to any drive system due to less THD and its various other advantages. As the three-level NPC inverter is more popular for medium voltage high power applications, this paper considered the NPC converter for analysis. This paper also presents the effect of load and speed variations in the stator current, speed and torque of the Induction Motor (IM) of the rating 400V, 10KW at 3KHz switching frequency. The proposed scheme is compared with the performance of Sinusoidal Pulse Width Modulation (SPWM) strategy applied drive system. The proposed control strategy is based on the nearest three-vector (N3V) scheme, without look-up table. The proposed SVM scheme uses less number of switching sequences and the timings or duty cycles simplified. Also these switching sequences are different for each sector of SVM diagram. The paper shows various simulation results of the structure.