Converter topologies for AC/DC and DC/AC power conversion, overview of applications of voltage source converters; pulsewidth modulation techniques for 1-phase and 3-phase bridge converters, sine-triangle PWM, 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.
Detailed syllabus:
- 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; evolution of topologies for dc-ac power conversion from dc-dc converters.
- 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.
- Purpose of pulsewidth 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.
- 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.
- Triangle-comparison based PWM (4 lectures): Average pole voltages, sinusoidal modulation, third harmonic injection, continuous PWM, bus-clamping or discontinuous PWM.
- 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.
- Analysis of line current ripple (4 lectures): Synchronously revolving reference frame; error between reference voltage and applied voltage, integral of voltage error; evaluation of line current ripple; hybrid PWM for reduced line current ripple.
- Analysis of dc link current (2 lectures): Relation between line-side currents and dc link current; dc link current and inverter state; rms dc current ripple over a carrier cycle; rms current rating of dc capacitors.
- Analysis of torque ripple (2 lectures): Evaluation of harmonic torques and rms torque ripple, hybrid PWM for reduced torque ripple.
- Inverter loss (3 lectures): Simplifying assumptions in evaluation of inverter loss, dependence of inverter loss on line power factor, influence of PWM techniques on switching loss, design of PWM for low inverter loss.
- Effect of inverter dead-time effect (2 lectures): Requirement of dead-time, effect of dead-time on line voltages, dependence on power factor and modulation method, compensation of dead-time effect.
- Overmodulation (3 lectures): Per-phase and space vector approaches to overmodulation, average voltages in a synchronously revolving d-q reference frame, low-frequency harmonic distortion.
- PWM 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.
