Space-vector-based hybrid PWM technique to reduce peak-to-peak torque ripple in induction motor drives

Special switching sequences involving division of active state time are used in space-vector-based generation of pulse width modulation (PWM) waveforms. This paper proposes a hybrid PWM technique which is a combination of the conventional and special switching sequences. The proposed hybrid PWM technique reduces the peak-to-peak torque ripple at high speeds of an induction motor drive. Supporting simulation and experimental results are presented from a closed-loop controlled motor drive

Comparative Evaluation of Space Vector Based Pulse Width Modulation Techniques in terms of Harmonic Distortion and Switching Losses

Voltage source inverter (VSI) fed induction motors are widely used in variable speed applications. The harmonic distortion in the line currents of the inverter depends on the switching frequency and the pulse width modulation (PWM) technique employed to switch the inverter. The inverter switching loss is also strongly influenced by the PWM technique used. This paper compares the harmonic distortion and inverter switching losses due to different PWM techniques at a given average switching frequency. The paper evaluates a few specially designed PWM techniques based on space vector approach. It is shown that these techniques lead to reduced line current distortion as well as switching losses compared to well-known techniques such as sine-triangle PWM and conventional space vector PWM (CSVPWM)

A Quick-Simulation Tool for Induction Motor Drives Controlled Using Advanced Space-Vector-Based PWM Techniques

Space-vector-based pulse width modulation (PWM) for a voltage source inverter (VSI) offers flexibility in terms of different switching sequences. Numerical simulation is helpful to assess the performance of a PWM method before actual implementation. A quick-simulation tool to simulate a variety of space-vector-based PWM strategies for a two-level VSI-fed squirrel cage induction motor drive is presented. The simulator is developed using C and Python programming languages, and has a graphical user interface (GUI) also. The prime focus being PWM strategies, the simulator developed is 40 times faster than MATLAB in terms of the actual time taken for a simulation. Simulation and experimental results are presented on a 5-hp ac motor drive

Theoretical and Experimental Evaluation of Pulsating Torque Produced by Induction Motor Drives Controlled With Advanced Bus-Clamping Pulsewidth Modulation

This paper investigates possible reduction of pulsating torque in open-loop and vector-controlled induction motor drives through deployment of certain advanced bus-clamping pulsewidth modulation (ABCPWM) method. Toward this goal, a simple and machine-independent method is proposed to analyze the torque harmonic spectrum of a voltage source inverter fed induction motor, operated with any real-time pulsewidth modulation (PWM) method. The analytically evaluated torque harmonic spectra, pertaining to conventional space vector PWM (CSVPWM), bus-clamping PWM (BCPWM), and ABCPWM, are validated through simulation and experimental results. Theoretical and experimental studies bring out the superiority of the ABCPWM in terms of torque harmonics over CSVPWM and BCPWM. The magnitude of the dominant torque harmonic with the ABCPWM scheme is shown to be significantly lower than that with CSVPWM, over a wide range of speed. The rms torque ripple (i.e., total rms value of all harmonic torques) is lower with ABCPWM than with BCPWM over the entire range of speed

Study on the Effect of Dead Time and its Compensation for Bus-Clamping PWM Techniques

Dead-time is provided in between the gating signals of the top and bottom semiconductor switches in an inverter leg to prevent the shorting of DC bus. Due to this dead time, there is a significant unwanted change in the output voltage of the inverter. The effect is different for different pulse width modulation (PWM) methodologies. The effect of dead-time on the output fundamental voltage is studied theoretically as well as experimentally for bus-clamping PWM methodologies. Further, experimental observations on the effectiveness of dead-time compensation are presented

Ultra-sensitive non-enzymatic ethanol sensor based on Reduced Graphene Oxide-Zinc Oxide composite modified electrode

In this work, we report a reduced Graphene Oxide (rGO)-Zinc Oxide (ZnO) composite based non-enzymatic ethanol sensor with an ultra-high sensitivity of 508.91 μAmM-1cm-2 which is, to the best of our knowledge, ~8 folds higher than previously reported electrochemical ethanol sensors. The rGO-ZnO composite was synthesized by a wet chemical method wherein the reduction of GO and intimate interfacial contact between ZnO NPs and rGO were achieved simultaneously. The sensing of ethanol was explicated by means of current-potential (I-V) technique. The sensor exhibited reproducible response with insignificant variations in current tested across multiple electrodes and responded linearly to ethanol in the range of 0.5-5 mM (R²=0.957). The sensor also showed lower limit of detection. The significant improvement in sensitivity is attributed to the improved surface activity and faster charge separation owing to formation of the nano-Schottky barrier at rGO-ZnO interface. This approach is beneficial as it eliminates the use of conducting binder along with the functional material for ethanol sensing. This ultra-sensitive, binder free rGO-ZnO based sensor offers a simple, low cost approach for ethanol detection in food, pharmaceutical, bio fuel industries and environmental analyses

Space-Vector-Based Hybrid Pulsewidth Modulation Techniques for Reduced Harmonic Distortion and Switching Loss

Novel switching sequences can be employed in spacevector-based pulsewidth modulation (PWM) of voltage source inverters. Differentswitching sequences are evaluated and compared in terms of inverter switching loss. A hybrid PWM technique named minimum switching loss PWM is proposed, which reduces the inverter switching loss compared to conventional space vector PWM (CSVPWM) and discontinuous PWM techniques at a given average switching frequency. Further, four space-vector-based hybrid PWM techniques are proposed that reduce line current distortion as well as switching loss in motor drives, compared to CSVPWM. Theoretical and experimental results are presented