POWER ELECTRONICS

Advanced knowledge of the operation of the electronic circuits mainly adopted for electric energy conversion (ac-dc, dc-dc with and without isolation, dc-ac). Knowledge of the main industrial, commercial and domestic applications; electric transportation applications; electric network; emerging applications: wireless power transfer.

Advanced knowledge of the characteristics, operation, advantages and limits of various power devices (diode, BJT, MOSFET, IGBT). Knowledge of the emerging technologies (SiC and GaN) and power device positioning and trend.

Knowledge of the passive components and parasitics in the power converters. Knowledge of the parasitic devices in the power devices.

Knowledge of some issues: heating removal and power converter driving.

Prerequisites

Knowledge of Kirchhoff's laws and branch equations. Knowledge of sinusoidal steady-state analysis. Knowledge of three-phase circuits.

Knowledge of semiconductor physics basics. Knowledge of the basic of semiconductor devices (p-n junction, BJT and MOSFET) structure and modelling.

Classroom or remote (or both) lectures.

Supplementary seminars held by experts from industry and academia.

Class attendance is not mandatory but it is highly recommended. The attendance of at least the 70% of seminars is mandatory.

Should teaching be carried out in mixed mode or remotely, it may be necessary to introduce changes with respect to previous statements, in line with the programme planned and outlined in the syllabus.

Exam

Oral exam concerning a topic related to converters and one related to the devices. An additional question may be asked to pass with honors. The average duration of the oral exam is one hour.

Learning assessment may also be carried out on line, should the conditions require it.

Introduction

Introduction to the field of Power Electronics. Advantages and applications. Overview of power semiconductor devices.
Sinusoidal and non-sinusoidal steady-state. Fourier series. Line current distortion.
Hopkinson’s lax. Inductor. Circuit model of the non-ideal transformer.

ac-dc converters

Single-phase rectifier: ideal circuit, effects of the input inductance, voltage distortion at the PCC. Voltage-doubler rectifiers. Effect of single-phase rectifiers on neutral currents in three-phase with four-wire. Three-phase rectifier: ideal circuit, effects of the input inductance. Basic notes on the controlled rectifiers.

dc-dc converters without isolation

Introduction to the dc-dc converters. Buck, Boost e Buck-Boost converters. Full-bridge dc-dc converter: PWM with bipolar and unipolar voltage switching. Basic notes on synchronous and bidirectional dc-dc converters.

dc-ac converters

Introduction to the inverter and to bidirectional converters. Half-bridge inverter. Full-bridge inverter: PWM with bipolar and unipolar voltage switching; square-wave control. Single-phase inverters with voltage cancellation. Push-Pull inverter. Three-phase inverter: PWM and square-wave control. Inverter ripple. Effect of the blanking (dead) time. Programmed harmonic elimination switching. Basic notes on current-regulated (current-mode) modulation.

dc-dc converters with isolation

Introduction to the dc-dc converters with isolation. Flyback and Forward converters. Push-pull. Half-bridge and full-bridge dc-dc converters with isolation.

Semiconductor physics

Recap of the basics on semiconductor physics. The p-n junction. Main trade-offs in power devices.

Power diode

Structure and characteristic. Conductivity modulation. Power losses. Breakdown voltage. Diode switching characteristics: inductively-loaded clamped switching circuit. Schottky diode.

Power BJT

Structure and characteristic. Current gain and Darlington configuration. Conductivity modulation: quasi-saturation and hard-saturation. Power losses. Breakdown: avalanche and thermal runaway. BJT switching characteristics: inductively-loaded clamped switching circuit. SOA.

Power MOSFET

Basic notes on JFET. Structure and characteristic. Threshold voltage. Breakdown voltage. Power losses. MOSFET switching characteristics: inductively-loaded clamped switching circuit. Effect of parasitics on the switching waveforms: overvoltage, positive and negative glitch, oscillations. Parasitic BJT. SOA.

IGBT

Structure and characteristic. Power losses. Breakdown voltage. IGBT switching characteristics: inductively-loaded clamped switching circuit. Latchup. SOA.

Positioning and trend of switching power devices

Main structures and characteristics of discrete devices and modules. Switching power devices: application fields and market trend. Silicon Carbide and Gallium Nitride power devices.

Seminars

The contents of the seminars are not considered during the exam. The following list reports the content of seminars held during previous courses. This list is as an example of potential topics that could be treated, the actual list will be provided to the students during the lessons once the seminars are planned with the speakers.

- Power factor correction (PFC)
- Design of a Boost PFC TM pre-regulator
- Multilevel converters
- Resonant converters
- Design of a Flyback converter
- Power converter control loop design
- Electromagnetic compatibility
- SiC power devices for automotive and sustainable energies
- GaN power devices: current applications and future trend
- SuperJunction MOSFET
- Power devices reliability

Slides projected during the lessons.

1) Ned Mohan, Tore M. Undeland, William P. Robbins, "Power Electronics: Converters, Applications, and Design". 3rd Edition, John Wiley & Sons, Inc., New York, November 2002.

2) B. Jayant Baliga, “Fundamentals of Power Semiconductor Devices”, Springer Science+Business Media, LLC, 233 Spring Street, New York, NY 10013, USA, 2008.