Space Vector Based Dual Zero-Vector Random Centered Distribution Pwm Algorithm for Direct Torque Control of Induction Motor Drive For Reduced Acoustical Noise

The direct torque control (DTC) technique has been recognized as the viable solution to achieve precise and quick torque response but it suffers from few drawbacks such as high ripple in torque, flux and stator current resulting in increased vibrations and acoustic noise. The conventional SVPWM algorithm gives good performance for control of induction motor drive, but it also produces considerable acoustical noise resulting in increased total harmonics distortion. The deterministic pulse width-modulation (PWM) method adopted in induction-motor drives causes Acoustical noise due to the switching frequency. This paper presents a novel dual zero-vector random centered distribution PWM algorithm for direct torque controlled induction motor drive. The proposed PWM algorithm uses two zero voltage vectors. When the operating modulation index is less than the critical modulation index, the proposed PWM algorithm uses V0 (000) as zero voltage vector. Otherwise, when the operating modulation index is greater than the critical modulation index, the proposed PWM algorithm uses V7 (111) as zero voltage vector. To verify the proposed PWM algorithm, a numerical simulation studies have been carried out and results are presented and compared with classical SVPWM algorithm. The simulation results confirm the effectiveness of the proposed DZRCDPWM algorithm for the considered drive. Key words: DTC, DZRCDPWM, RPWM, SVPWM, Acoustic noise

Space Vector Based Hybrid Random PWM Algorithm for DTC-IM Drive To Achieve Superior Waveform Quality

This paper presents a simplified space vector based hybrid random pulsewidth modulation algorithm for direct torque controlled induction motor drive to achieve superior waveform quality and reduced acoustical noise and harmonic distortion. To reduce the complexity involved in the conventional space vector approach, the proposed pulsewidth modulation (PWM) algorithm uses instantaneous sampled reference phase voltages to calculate the actual switching times of the devices. The proposed PWM algorithm modifies the time duration of application of vector V0 (000) by using a factor. By changing the value of this factor many switching sequences can be derived. The proposed PWM algorithm uses 0127, 012 and 721 switching sequences when value takes 0.5, 1 and 0 respectively. In order to achieve superior waveform quality, the harmonic analysis of these sequences is carried out using the notion of stator flux ripple and expressions are derived for mean square flux ripple in terms of imaginary switching times and modulation index. By comparing the instantaneous ripple values in each sampling time interval, the suitable sequence is selected that results in minimum current ripple. Thus, the proposed algorithm gives reduced harmonic distortion when compared with the SVPWM algorithm. As the zero state time is varied randomly according to the operating sequence, randomization effect will occur, which results in reduced dominating harmonics and hence acoustical noise when compared with the SVPWM algorithm. The simulation results validate the proposed algorithm

Random Zero Vector Distribution PWM Algorithm for Direct Torque Control of Induction Motor Drive for Noise Reduction

The basic direct torque control algorithm gives large ripples in torque, flux and current in steady state, which results in acoustical noise and incorrect speed estimations. The conventional SVPWM algorithm gives good performance for control of induction motor drive, but it produces more acoustical noise resulting in increased total harmonics distortion. The random pulse width modulation (RPWM) techniques have become an established means for mitigation of undesirable side effects in adjustable speed ac drives in particular. Hence, to minimize these anomalies of the drive, this paper presents a random zero vector distribution (RZVDPWM) algorithm for direct torque controlled induction motor drive. The proposed random zero vector distribution PWM (RZVDPWM) algorithm distributes the zero state time between the two zero voltage vectors. To validate the proposed PWM algorithm, simulation studies have been carried out and results are presented and compared. From the results, it can be observed that the proposed RZVDPWM algorithm gives reduced acoustical noise when compared with space vector pulse width modulation (SVPWM) algorithm