Pulse width Modulation for Power Electronic Converters

Pulse width Modulation for Power Electronic Converters. Converter topologies for AC/DC and DC/AC power conversion, an overview of applications of voltage source converters; pulse-width modulation techniques for 1-phase and 3-phase bridge converters, sine-triangle Pulse width Modulation, bus clamping PWM, space vector based PWM, advanced PWM techniques; calculation of switching and conduction losses; compensation for dead time and DC voltage regulation; estimation of current ripple and torque ripple in inverter fed drives; overmodulation; extension of modulation methods to multilevel inverters.

Pulse width Modulation for Power Electronic Converters Detailed syllabus:

1. Power electronic converters for dc-ac and ac-dc power conversion (6 lectures).

Electronic switches, dc-dc buck and boost converters, H-bridge, multilevel converters – diode clamp, flying capacitor, and cascaded-cell converters; voltage source and current source converters; the evolution of topologies for dc-ac power conversion from dc-dc converters.

2. Applications of voltage source converters (2 lectures).

Overview of applications of voltage source converter, motor drives, active front-end converters, reactive compensators, active power filters

3. Purpose of pulse width modulation (2 lectures).

Review of Fourier series, fundamental and harmonic voltages; machine model for harmonic voltages; undesirable effects of harmonic voltages – line current distortion, increased losses, pulsating torque in motor drives; control of fundamental voltage; mitigation of harmonics and their adverse effects

4. Pulsewidth modulation (PWM) at low switching frequency (3 lectures).

Square wave operation of voltage source inverter, PWM with a few switching angles per quarter cycle, equal voltage contours, selective harmonic elimination, THD optimized PWM, off-line PWM

5. Triangle-comparison-based PWM (4 lectures).

Average pole voltages, sinusoidal modulation, third harmonic injection, continuous PWM, bus-clamping, or discontinuous PWM

6. Space vector-based PWM (4 lectures).

Space vector concept and transformation, per-phase methods from a space vector perspective, space vector-based modulation, conventional space vector PWM, bus-clamping PWM, advanced PWM, triangle comparison approach versus space vector approach to PWM

7. Analysis of line current ripple (4 lectures).

Synchronously revolving reference frame; error between the reference voltage and applied voltage, integral of voltage error; evaluation of line current ripple; hybrid PWM for reduced line current ripple

8. Analysis of dc link current (2 lectures).

The relation between line-side currents and dc-link current; dc-link current and inverter state; RMS DC ripple over a carrier cycle; RMS current rating of dc capacitors

9. Analysis of torque ripple (2 lectures).

Evaluation of harmonic torques and RMS torque ripple, hybrid PWM for reduced torque ripple

10. Inverter loss (3 lectures).

Simplifying assumptions in the evaluation of inverter loss, the dependence of inverter loss on line power factor, the influence of PWM techniques on switching loss, design of PWM for low inverter loss.

11. Effect of inverter dead-time effect (2 lectures).

The requirement of dead-time, the effect of dead-time on line voltages, dependence on power factor and modulation method, compensation of dead-time effect.

12. Overmodulation (3 lectures).

Per-phase and space vector approaches to overmodulation, average voltages in asynchronously revolving d-q reference frame, low-frequency harmonic distortion

13. Pulse width Modulation for multilevel inverter (3 lectures).

Extensions of sine-triangle PWM to multilevel inverters, voltage space vectors, space vector based PWM, analysis of line current ripple, and torque ripple

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