Author Copy 43 SPWM Techniques in Closed Loop Control of Five-Level Inverter Fed 3 Induction Motor © 2014 IUP. All Rights Reserved. SPWM Techniques in Closed Loop Control of Five-Level Inverter Fed 3 Induction Motor M V Subramanyam* and P V N Prasad** * Assistant Professor, Department of Electrical and Electronics Engineering, Matrusri Engineering College, Hyderbad, Andhra Pradesh, India; and is the corresponding author. E-mail: subramanyam.mvs@gmail.com ** Professor, Department of Electrical Engineering, Osmania University, Andhra Pradesh, India. E-mail: pvnprasad@osmania.ac.in The paper investigates the effect of carrier frequency variation on Total Harmonic Distortion (THD) of output current using different Sinusoidal Pulse Width Modulation (SPWM) techniques. The induction motor is fed by closed loop fuzzy logic controlled five-level Multilevel Inverter (MLI). The MLI has several advantages over two-level conventional inverters such as reduced harmonics and lower voltage stress on power electronic switches. The different techniques in SPWM of phase disposition methods are used. Keywords: Carrier frequency, Multilevel Inverter (MLI), Phase disposition, Sinusoidal Pulse Width Modulation (SPWM), Total Harmonic Distortion (THD) Introduction Multilevel Inverters (MLI) include an array of power semiconductor devices and capacitor voltage sources, the output of which generates stepped voltage waveforms. The commutation of switches permits the addition of capacitor voltages, which results as high voltage at output, while the power semiconductor must withstand only reduced voltages. However, as the number of levels increases, the control complexity increases. Figure 1 shows a schematic diagram of one-phase leg of two-level and three-level inverters with different number of levels, for which the action of semiconductors is represented by ideal switch with several positions. In closed loop control, there are two loops—inner current loop and outer speed loop. Both closed loops are controlled using fuzzy logic. As there are several modulation techniques, the Sinusoidal Pulse Width Modulation (SPWM) techniques is discussed here (Teodorescu et al., 1999; and Subramanyam et al., 2013). There are several SPWM Techniques such as (i) In Phase Disposition PWM (IPDPWM); (ii) Phase Opposition Disposition PWM (PODPWM); (iii) Alternate Phase Opposition Disposition PWM (APODPWM); (iv) Alternate Phase Opposition Disposition and Alternate Phase Shift PWM (APODAPSPWM); (v) Phase Shift PWM (PSPWM); (vi) Alternate Phase Shift PWM (APSPWM), (vii) Carrier Overlap PWM (COPWM); (viii) Variable Frequency PWM (VFPWM); and (ix) Alternate Variable Frequency PWM (AVFPWM) (Farid and Farid, 2009; Ozdemir et al., 2009; and Srinivas, 2009). In this paper, five-level MLI is used. The first four-phase disposition methods are considered. The rating of induction motor is 3, 4500 W, 415 V and 50 Hz.