Analysis of Space Vector Pulse Width Modulation VSI Induction Motor on various conditions Padma Chaturvedi 1, Amarish Dubey 2 1 Department of Electrical Engineering, Maharana Pratap Engineering College, Mandhana, Kanpur (U.P.) India 2 Department of Electronics and Communication Engineering, Rama Institute of Engineering and Technology, Mandhana, Kanpur (U.P.) India ABSTRACT In this paper an attempt is made to investigate the performance of SVPWM VSI-fed induction motor drive. The openloop Simulink model of the voltage source inverter-fed induction motor drive is presented based on space vector theory. Simulation results are obtained for performance analysis of the drive under different loading conditions and are discussed in detail. Keywords: Induction motor drive, Space vector pulse width modulation (SVPWM), Voltage source inverter. 1. INTRODUCTION Advances in power electronics have led to an increased interest in voltage source inverters with pulse width modulation control of AC drives. A number of pulse width modulation (PWM) schemes are used to obtain variable voltage and frequency supply. The most widely used PWM schemes for three-phase voltage source inverters are carrier- based sinusoidal PWM and space vector PWM (SVPWM). There is an increasing trend of using space vector PWM (SVPWM) because of their easier digital realization and better DC bus utilization [1-3]. Moreover, it gives a higher output voltage for the same DC bus voltage, lower switching losses, and better harmonic performance in comparison to carrier based sinusoidal pulse width modulation [4-5]. The space vector pulse width modulation of a three level inverter provides the additional advantage of superior harmonic quality and larger under-modulation range that extends the modulation factor to 90.7% from the traditional value of 78.5% in sinusoidal pulse width modulation. This paper focuses on SVPWM implemented on an induction motor drive. The model of a three-phase voltage source inverter is presented based on space vector theory. 2. SYSTEM DESCRIPTION Fig.1 shows the basic circuit for the performance investigation of VSI-fed induction motor drive using SVPWM technique. Fig.2 shows the simulation model for the performance investigation of VSI-fed induction motor drive using SVPWM technique. The SVPWM voltage source inverter-fed induction motor drive system consist of an input LC filter, a three-phase controlled rectifier, a DC link capacitor, a three-phase voltage source inverter, a squirrel-cage induction motor and an output LC filter for controlling the speed of the induction motor. Figure 1 Circuit model of the SVPWM VSI fed IM drive. Volume 2, Issue 12, December 2013 Page 409
3. PERFORMANCE INVESTIGATION OF THE DRIVE A MATLAB/Simulink model is developed to examine the performance of the three-phase induction motor drive as shown in Fig.2. A three-phase squirrel-cage induction motor rated 3 hp, 220 V, 60 Hz, 1725 rpm is fed by a three-phase IGBT inverter connected to a DC link voltage source of 325 V. The firing pulses to the inverter are generated by the spacevector PWM modulator block of the SPS library. The chopping frequency is set to 1980 Hz and the input reference vector to magnitude-angle. Speed control of the motor is performed by the constant V/Hz block. The magnitude and frequency of the stator voltages are governed by the speed set point. By varying the stator voltage magnitude in proportion with frequency, the stator flux is kept constant. Figure 2 Simulink model of the SVPWM VSI fed IM drive System The performance of the drive is investigated for the following loading conditions: 3.1 CASE 1: AT FULL LOAD (Tfl = 11.9 N-m.) Simulation results of induction motor at full load are shown in figures 3-8. Figure 3 shows DC link voltage which is found to be 309.6 V. Figure 4 shows inverter output voltage of which the peak amplitude is 309.6 V. The stator and rotor currents are shown in figures 5-6. The starting current is high and within 0.85 second, it reaches to steady state value 10.72 A. Steady state value of rotor current is 8.735 A. The rotor speed is shown in figure 7 and it can be observed that speed reaches at steady state value 1720 rpm within 0.85 second when motor is subjected to full load 11.9 N-m. Figure 8 shows the electromagnetic torque of the motor of which steady state value is 12.15 N-m. Figure 3 DC link voltage (Case-1) Figure 4 Inverter output voltages (Case-1) Volume 2, Issue 12, December 2013 Page 410
Figure 5 Three-phase induction motor stator current (Case-1) Figure 6 Three-phase induction motor rotor current (Case-1) Figure 7 Three-phase induction motor rotor speed Figure 8 Three-phase induction motor (Case-1) electromagnetic torque (Case-1) 3.2 CASE 2: AT NO LOAD CONDITION (T =0 N-m.) Simulation results of induction motor at no load condition are shown in figures 9-14. Figure 9 shows DC link voltage which is found to be 309.8 V. Figure 10 shows inverter output voltage of which the peak amplitude is 311 V. The stator and rotor currents are shown in figures 11-12. The starting current is high and within 0.7 second, it reaches to steady state value 2.495 A. Steady state value of rotor current is 0.03483 A. The rotor speed is shown in figure 13 and it can be observed that speed reaches at steady state value 1800 rpm within 0.7 second when motor is subjected to no load. Figure 14 shows the electromagnetic torque of the motor of which steady state value is 0.1975 N-m. Figure 9 DC link voltages (Case-2) Figure 10 Inverter output voltages (Case-2) Figure 11 Three-phase induction motor stator current Figure 12 Three-phase induction motor rotor (Case-2) current (Case-2) Figure 13 Three-phase induction motor rotor speed (Case-2) Figure 14 Three-phase induction motor Electromagnetic torque (Case-2). Volume 2, Issue 12, December 2013 Page 411
3.3 CASE 3: AT OVER LOAD CONDITION (T=15 N-m) Simulation results of induction motor at over load condition are shown in figures 15-20. Figure 15 shows DC link voltage which is found to be 309.2 V. Figure 16 shows inverter output voltage of which the peak amplitude is 309.3 V. The stator and rotor currents are shown in figures 17-18. The starting current is high and within 0.9 second, it reaches to steady state value 13.06 A. Steady state value of rotor current is 6.385A. The rotor speed is shown in figure 19 and it can be observed that speed reaches at steady state value 1697 rpm within 0.9 second when motor is subjected to over load 15 N- m. Figure 20 shows the electromagnetic torque of the motor of which steady state value is 15.27 N-m. Figure 15 DC link voltages (Case-3). Figure 16 Inverter output voltages (Case-3) Figure 17 Three-phase induction motor stator current (Case-3) Figure 18 Three-phase induction motor rotor current (Case-3) Figure 19 Three-phase induction motor rotor speed (Case-3) Figure 20 Three-phase induction motor electromagnetic torque (Case-3) 3.4 CASE 4: AT UNDER LOAD CONDITION (T = 8 N-m) Simulation results of induction motor at under load condition are shown in figure from figure 21-26. Figure 21 shows DC link voltage which is found 309.6 V. Figure 22 shows inverter output voltage of which the peak amplitude is309.6 V. The stator and rotor currents are shown in figures 23-24. The starting current is high and within 0.75 second, it reaches to steady state value 7.896 A. Steady state value of rotor current is 5.065 A. The rotor speed is shown in figure 25 and it can be observed that speed reaches at steady state value 1748 rpm within 0.75 second when motor is subjected to under load 8 N-m. Figure 26 shows the electromagnetic torque of the motor of which steady state value is 8.236 N-m. Figure 21 DC link voltage (Case-4) Figure 22 Inverter output voltages (Case-4) Volume 2, Issue 12, December 2013 Page 412
Figure 23 Three-phase induction motor stator current (Case-4) Figure 24 Three-phase induction motor rotor current (Case-4) Figure 25 Three-phase induction motor rotor speed (Case-4) Figure 26 Three-phase induction motor electromagnetic torque (Case-4). Table 1 Performance investigation of VSI-fed induction motor drives using SVPWM technique at different loading conditions Performance Quantities Full Load (11.9 N-m) No Load (0 N-m) Over Load (17 N-m) Under Load (8 N-m) Stator Current(A) 10.72 2.495 13.06 7.896 Rotor Current (A) 8.735 0.03483 6.385 5.065 Speed (rpm) 1720 1800 1697 1748 Electromagnetic Torque (N-m) 12.15 0.1975 15.27 8.236 Settling Time (s) 0.85 0.7 0.9 0.75 The facts and figures discussed in section-iii have been summarized in Table 1. References [1] Khoudir Marouani, Lotfi Baghli, DjafarHadiouche, Abdelaziz Kheloui1, and Abderrezak Rezzoug, Discontinuous SVPWM Techniques for Double Star Induction Motor Drive Control, IEEE,pp. 902-907, 2006. [2] R. Rajendran and Dr. N. Devarajan, FPGA Implementation of Space Vector PWM technique for Voltage Source Inverter Fed Induction Motor Drive, IEEE, pp. 422-426, 2009. [3] Y. Zhao and T. A. Lipo, Space Vector PWM Control of DualThree-phase Induction Machine using Vector Space Decomposition, IEEE Trans. Ind Appl., vol. 31, no. 5, pp. 1100 1109, Sep./Oct. 1995. [4] Comprehensive Analysis, IEEE Transaction on Industrial Electronics, vol. 49, no.1, pp.186 196, Feb. 2002.H. Bain, Z. Zhao, S. Meng, J. Liu, and X. Sun, Comparison of Three PWM Strategies-SPWM, SVPWM & OnecycleControl, in Proc. 5th International Conference on Power Electronics Drive system, vol. 2, pp. 1313-1316, 2003. AUTHOR Padma Chaturvedi was born in Kanpur (U.P.), India. She received her Bachelor degree in Electrical and Electronics Engineering from U.P. Technical University, India. She did her Master of Technology from Department of Electrical Engineering (Power Electronics and Drives), Kamala Nehru Institute of Technology, Sultanpur, (U.P.) India. She worked as lecturer and Asst. Prof. in different Engineering colleges of UP Technical University. Presently she is working as an Asst. Professor in Department of Electronics Engineering, Maharana Pratap Engineering College Kanpur, UP, India. Her areas of interest are in the field of Power Electronics and Drives, Fault Tolerance, Leakage and Power reduction in Semiconductor Devices and etc. Volume 2, Issue 12, December 2013 Page 413
Amarish Dubey was born in Kanpur, (U.P.) India. He received his Bachelor degree in Electronics and Communication Engineering from U.P. Technical University, INDIA. He has completed his Master of Technology from Department of Electronics Engineering, Indian Institute of Technology (Banaras Hindu University), Varanasi (U.P.) India. He worked as lecturer and Asst. Prof. in different Engineering colleges of U.P. Technical University. Presently he is working as an Asst. Professor in Department of Electronics and Communication Engineering, Rama Institute of Engineering and Technology, Kanpur (U.P.) India. His areas of interest are Digital Design, Fault Tolerance, Leakage and Power reduction in VLSI Design, Radiation Effects in Semiconductor Devices, Power Electronics and Drives and etc. APPENDIX-I Induction Motor Parameters Voltage Nominal Power Frequency 220V 2238W 60Hz Pole Pairs 2 Rated Load Torque Speed Rotation Inertia Stator Resistance Rotor Resistance Stator Leakage Inductance Rotor Leakage Inductance Mutual Inductance 11.6 N-m 1725 rpm 0.0879Kg-m2 0.435 ohm 0.816 ohm 0.004 H 0.004 H 0.06931 H Volume 2, Issue 12, December 2013 Page 414