Analysis of 2-Level and 3-Level Inverter Fed Direct Torque Control of Induction Motor Drive

AC drives are more predominant than dc drives. Ac drives require control of frequency, current and voltage for variable-speed applications. The difference between the traditional vector control and the DTC is that the DTC has no fixed switching pattern. The DTC switches the inverter according to the load needs. Though conventional DTC (CDTC) is simple, easy to implement generates substantial steady state ripples in torque and flux and acoustical noise. Also, with CDTC the switching frequency is not maintained constant. In recent years several PWM techniques were developed to reduce the steady state ripple and to get the constant switching frequency. CSVPWM results in higher line side voltage and less line current harmonic distortion than sine triangle PWM with constant switching frequency. CSVPWM-based DTC could eliminate some tribulations that are with the CDTC, such as steady state ripples in torque and flux, variable switching frequency, etc., at higher line side voltages. This paper discusses the implementation of a high-performance direct torque control (DTC) of induction machine drive using SVPWM technique for two level and three level inverter and results are compared. The software used for this project is MATLAB/SIMULINK.