Kaushik Basu

Reduction of Torque Ripple in Induction Motor Drives Using an Advanced Hybrid PWM Technique

A voltage source inverter-fed induction motor produces a pulsating torque due to application of nonsinusoidal voltages. Torque pulsation is strongly influenced by the pulsewidth modulation (PWM) method employed. Conventional space vector PWM (CSVPWM) is known to result in less torque ripple than sine-triangle PWM. This paper aims at further reduction in the pulsating torque by employing advanced bus-clamping switching sequences, which apply an active vector twice in a subcycle. This paper proposes a hybrid PWM technique which employs such advanced bus-clamping sequences in conjunction with a conventional switching sequence. The proposed hybrid PWM technique is shown to reduce the torque ripple considerably over CSVPWM along with a marginal reduction in current ripple.

Minimization of Torque Ripple in PWM AC Drives

A pulsewidth modulation (PWM) technique is proposed for minimizing the RMS torque ripple in inverter-fed induction motor drives subject to a given average switching frequency of the inverter. The proposed PWM technique is a combination of optimal continuous modulation and discontinuous modulation. The proposed technique is evaluated both theoretically as well as experimentally and is compared with well-known PWM techniques. It is shown that the proposed method reduces the RMS torque ripple by about 30% at the rated speed of the motor drive, compared to conventional space vector PWM.

Carrier-Based Implementation of SVPWM for Dual Two-Level VSI and Dual Matrix Converter With Zero Common-Mode Voltage

Pulse width modulation (PWM) converters generate switching common-mode voltages (CMVs) across the load terminals. These voltages cause common-mode currents, leading to bearing failure in motor loads and electromagnetic interference problems. This paper presents a generalized carrier-based PWM technique for open-end winding motor drives that completely eliminates switching CMV. The proposed method is applicable to both dual two-level voltage source inverter and dual matrix converter-based open-end winding drives. Detailed analysis shows that the carrier-based method requires significantly less computation compared to the corresponding space vector implementation. This paper also outlines the relationship between the two implementations. The carrier-based method is shown to achieve superior performance in terms of resource requirements and execution time when implemented on a field-programmable gate array-based real-time control platform. Simulation and experimental results have been presented to validate the proposed method.

A High-Frequency Link Single-Stage PWM Inverter With Common-Mode Voltage Suppression and Source-Based Commutation of Leakage Energy

This paper presents a single-stage bidirectional high-frequency transformer (HFT) link dc/ac converter topology for a three-phase adjustable magnitude and frequency PWM ac drive. This type of converters find a wide range of applications including UPS systems, drives involving renewable energy sources (Solar, Fuel cell), and energy storage systems (typically low voltage dc to high voltage PWM ac). The HFT results in reduction in cost and weight along with a considerable increase in power density. The adverse effects of common-mode voltage are well known in this kind of applications. The proposed topology along with a modulation technique reduces common-mode voltage to practically zero and generates high-quality output voltage waveform comparable to conventional space vector PWM (CSVPWM). A source-based commutation method, presented in this paper, to commute the energy stored in the leakage inductance of the HFT resulting in the following advantages 1) no need for any auxiliary circuits with passive components; 2) almost complete recovery of the leakage energy; 3) soft switching of the output side converter for all load conditions; and 4) minimization of common-mode voltage switching due to commutation. The converter along with the suggested control has been analyzed in detail. The presented simulation and experimental results confirm the operation of the proposed converter.

A Single-Stage Dual-Active-Bridge-Based Soft Switched AC–DC Converter With Open-Loop Power Factor Correction and Other Advanced Features

A dual-active-bridge-based single-stage ac/dc converter may find a wide range of emerging applications such as interfacing plug-in hybrid vehicles with the ac grid, interconnection of dc grid, etc. This type of converter can be used due to unique features such as 1) high-frequency isolation resulting in a) high power density and b) safety and voltage matching; 2) bidirectional power flow; 3) soft switching leading to higher efficiency. In this paper, a modulation strategy has been proposed that results in 1) open-loop power factor correction; 2) zero current switching in the ac-side converter for all load conditions; 3) linear power relationship for easy control implementation; and 4) Zero voltage switching in the load side converter. The converter with the proposed control has been analyzed. Simulation and experimental results on a 1-KW prototype confirm the advantages.

Research in matrix-converter based three-phase power-electronic transformers

This paper presents a review of the current research in the area of ac/ac power conversion with power electronic transformer. The topologies considered have the following features: 1) generation of adjustable frequency and magnitude PWM ac voltage waveform from a balanced three-phase ac voltage source with a high frequency ac link, 2) bidirectional power flow capability, and 3) single stage power conversion without any storage elements. All of these topologies provide power factor correction. Based on the operation and control, these topologies have been classified into three groups. The operation, advantages and drawbacks of each of these topologies have been presented along with a comparison of their performance in the presence of leakage inductance, complexity to control and reliability.

Systematic Input Filter Design of Matrix Converter by Analytical Estimation of RMS Current Ripple

A filter is required to eliminate the high-frequency switching ripple present in the input current of a matrix converter (MC). Design of such a filter requires an estimation of the higher harmonic components present in the input current. This paper presents a simple closed-form analytical expression for the RMS input current ripple injected by the MC. The expression shows the variation with load power factor and is independent of the output frequency. This is used in a step-by-step procedure to design various input filter components from the specifications of allowable total harmonic distortion in the grid current and distortion in the input voltage. The MC is modeled for the grid frequency component in order to evaluate the design for input power factor and voltage drop across the filter. A damping resistance has been designed ensuring minimum ohmic loss. The analytical estimation of the ripple current and the proposed design procedure have been validated by simulations in MATLAB/Simulink and experiments on a laboratory prototype.

Modulation strategies for direct-link drive for open-end winding AC machines

Switching common-mode voltages generated by conventional pulse-width modulated inverters are known to cause bearing currents in ac machines. These undesirable currents may result in bearing damage. A direct-link drive for open-end winding ac machines has recently been proposed. Some advantages of the drive include: 1) common-mode voltage suppression, 2) no storage elements, and 3) ability to achieve up to 1.5 times the peak input phase voltage across the machine phase windings. In this paper, pulsewidth modulation strategies for the drive are proposed. Two strategies are based on space vector modulation and suppress common-mode voltage at the machine terminals. One carrier-based strategy achieves 1.5 times the peak input phase voltage across the machine phase windings but causes switching common-mode voltage at the machine terminals. Simulation and experimental results are presented to verify the operation of the drive.

Advanced modulation strategy for a three-phase AC-DC dual active bridge for V2G

The introduction of Plug-in Hybrid Electric Vehicles (PHEV) and Electric Vehicles (EV) into the consumer market provides opportunities and challenges to implement Vehicle-2-Grid (V2G). V2G is a vehicle that can connect to the grid and consume power to charge its battery pack or supply power to the grid. This paper presents research on a novel converter that implements bidirectional power flow between the grid and a vehicles battery pack. The main advantages of this converter are the following: i) soft switching for all switches of the input converter independent of the load, Zero Current Switching (ZCS) ii) The switching of the input converter is simplified i.e four-step commutation is not required for the four quadrant switches of the input side converter iii) The average power flow through the converter is a linear function of the control variable so the control is simple iv) open loop input power factor correction, v) high power density, vi) isolation. The entire topology has been simulated with the proposed modulation method and simulation results confirm the analytical predictions.

High-frequency transformer-link three-level inverter drive with common-mode voltage elimination

This paper proposes a novel topology along with a switching strategy for AC/AC conversion with a high frequency transformer link. The input side converter is a three phase to single phase direct link matrix converter switched with a simple triangle comparison based novel PWM strategy and provides input power factor correction. This PWM technique also helps to eliminate the effect of the pulsating DC bus seen by the output inverter. The high frequency transformer provides flexible voltage transfer ratio along with galvanic isolation and has much reduced size compared to the bulky line frequency transformer. The centre tapped secondary of the transformer along with a single phase rectifier provide the required voltage levels for a three level inverter. This inverter is operated as a two level inverter in order to eliminate common mode voltages at its output. A novel variable slope carrier is used for this inverter in order to nullify the effect of fluctuating DC bus. The major advantages of this scheme are a) elimination of DC bus capacitor, b) low neutral point fluctuation, c) isolation, d) input power factor correction e) flexible voltage transfer ratio and f) high power density. The proposed configuration is simulated and simulation results are presented, which verifies the operation.