Course detail

# Power Electronics

FEKT-BKC-VELAcad. year: 2020/2021

Basic classification of power converters: AC/DC, AC/AC, DC/DC, DC/AC. Cascade of few converters. DC-bus. Static thermal phenomena. Cooling of semiconductors. Demanded thermal resistance of the heat sink. Active power; its calculation in special cases. EMC in LF region. Power factor, total harmonic distortion factor. Power switching devices, overview: diode, thyristor, triac, BJT, MOS-FET, IGBT, GTO.

Rectifiers: non-controlled, controlled. Typical loads. Mean value of output voltage. Net rectifiers for supplying of transistor converters. AC/AC converters: 1-phase, 3-phase. Loads of R, L, R-L, R-L-Ui types. Phase control of triacs. DC/DC transistor converters. DC/AC transistor converters (1-phase, 3-phase). Control strategy of DC/DC, and DC/AC converters. PWM, sinusoidal PWM. Magnetic phenomena in the power electronics. Transformer theory. Mathematic models of the voltage transformer. Switch-mode supplies. DC/DC converters with the pulse transformer. Single-end buck converter.

Supervisor

Learning outcomes of the course unit

It is proved by written test, that student is able:

- To define power converter. To define ideal switching element. To list four basic types of converters: AC/DC, AC/AC, DC/DC, DC/AC. To describe the cascade of more converters with the voltage/current DC-bus.

- To describe static thermal phenomena. To explain the cooling of semiconductors. To calculate the demanded thermal resistance of the heat-sink.

- To define the active power. To calculate the conducting losses of a switching device.

- To define EMC in LF area. To define the power factor. To define the total distortion factor of a phase current.

- To list power switching devices: uncontrollable (D), semi-controllable (Ty, Tri), controllable (BJT, MOS-FET, IGBT, GTO). To name its usable parameters.

- To list all types of the rectifiers (AC/DC): uncontrolled, controlled, semi-controlled, node/bridge, m-phase, q-pulse, with/without flywheel diode. To list typical loads: DC-motor, LC-filter, accumulator, welding arc. To justify, why the mean value of the output voltage is useable. To describe hte rectifier from the cybernetics point of view: control char., transport delay, dynamics.

- To represent the current rippling in the rectifier load. To analyse the shapes of the input phase currents.

- To describe and analyse the net DC sources for transistor converters: 2-pulse uncontrolled rectifier with pick-up capacitor, 6-pulse uncontrolled rectifier with pick-up capacitor or LC-filter.

- To list and to describe AC/AC type converters: 1-phase, 3-phase. To analyse its work into the R-load. To deduce the control characteristics for R-load, and justify why the RMS value of the output voltage is useful.

- To list the transistor pulse DC converters (DC/DC). To divide it with regard to the ability to work in the different quadrants of the VA-characteristics of the load. To analyse the converter working in I.Q.

- To analyse the DC/AC converters, 1-phase, 3-phase.

- To describe the PWM system for the control of DC/DC and DC/AC converters.

In the laboratory practices the student measures and analyses signals in different power converters with help of oscilloscope. Student trains following skills:

- To handle and to use basic measure instruments in the power electronics laboratory: oscilloscope, voltmeter, ampermeter, DC and AC laboratory supplies.

- To measure operational properties of different uncontrolled diode rectifiers. To describe measured oscillographs of currents and voltages. To measure the rippling of the output voltage and current.

- To measure pulse converter working in the 1.Q. To describe measured oscillographs of currents and voltages. To analyse the voltage and current rippling on the load.

- To measure 1-phase converter of the AC voltage (AC/AC). To describe the measured oscillographs of currents and voltages.

- To analyse the diagrams of voltages in the 1-phase DC/AC converter working in the sinusoidal PWM regime.

In the numerical lectures the student learns following skills:

- To calculate the mean and RMS value of typical signals.

- To design the current and voltage capability of the power switching devices.

- To calculate the power conducting loss of the power switching device.

- To calculate demanded thermal resistance of the heat-sink in the steady-state.

- To calculate the active power in the different nodes of DC/DC power converters.

- To design controlled rectifier. To calculate in it the voltage, current, and power rates.

- Navrhnout a dimenzovat střídavý měnič napětí. Spočítat v něm napěťové, proudové a výkonové poměry.

- To design AC/AC converter. To calculate in it the voltage, current, and power rates.

Prerequisites

Student must have the previous knowledge from the applied mathematics: To use and to apply the mathematical operations above complex numbers in the component and polar representation (summation, subtraction, multiplication, division, and rectification of the complex fraction). To apply the basic principles of the integral and differential calculus of one variable: description of the inductor work, i.e. induction law in the differential and integral form, similarly the dif. and integr. relation between instant values of the current and voltage at the capacitor. Calculus of the mean and RMS values of the periodical function. Student must have the previous general knowledge and ability: To describe basic properties of the discrete electronic devices (diode, bipolar and unipolar transistor). To attend the course BREB (Control Electronics). To be able practically to use and to apply the following tools for the analysis and synthesis of the electric circuits: 1st and 2nd Kirchhoff laws, Ohm law, induction law in the differential and integral form.

Co-requisites

Not applicable.

Recommended optional programme components

Not applicable.

Recommended or required reading

K.Heumann,A.Stumpe:Thyristoren,B.G.Teubner (DE)

Z.Čeřovský,J.Pavelka : Výkonová elektronika 1, skripta ČVUT (CS)

Bose, B.K.: Power electronics and AC Drives. Prentice Hall 1986 (EN)

Patočka M.: Vybrané statě z výkonové elektroniky, sv. 1, skriptum FEKT, VUT Brno (CS)

Patočka M.: Vybrané statě z výkonové elektroniky, sv. 2, skriptum FEKT, VUT Brno (CS)

Patočka M.: Výkonová elektronika, 1. část - usměrňovače, střídavé měniče napětí, skriptum FEKT, Brno, 2010 (CS)

Patočka M.: Magnetické obvody Elektronický učební text, FEKT, VUT Brno (CS)

Planned learning activities and teaching methods

Lectures are lead with the massive support of Power-Point. The Power-Point file is available for students.

In laboratories, students measure 6 exercises (power converters) with the help of oscillograph.

In numerical exercises, the typical tasks are solved (design of power converters, design of the cooling system).

Assesment methods and criteria linked to learning outcomes

20 points for first semestral test.

1+1+1+1 points = 4 points for 4 laboratory tasks.

6 points for second semestral test.

70 points for exam.

100 points total.

Language of instruction

Czech

Work placements

Not applicable.

Course curriculum

1. Basic classification of power converters: AC/DC, AC/AC, DC/DC, DC/AC. Cascade of few converters. DC-bus.

2. Static thermal phenomena. Cooling of semiconductors. Demanded thermal resistance of the heat sink.

3. Active power; its calculation in special cases.

4. EMC in LF region. Power factor, total harmonic distortion factor.

5. Power switching devices, overview: diode, thyristor, triac, BJT, MOS-FET, IGBT, GTO. Drivers for transistors.

6. Rectifiers: non-controlled, controlled. Typical loads. Mean value of output voltage. Rectifier dynamic. Four-quadrant rectifiers.

7. Rippling of the rectifier load current. Demanded inductance of the choke. Type power of the supplying transformer.

8. Main rectifiers for supplying of transistor converters. Two-pulse rectifier with the capacitor, and six-pulse rectifier with the LC-filter or capacitor.

9. AC/AC converters: 1-phase, 3-phase. Loads of R, L, R-L, R-L-Ui types. Control characteristic for R-load. Phase control of triacs.

10. DC/DC transistor converters. Classification. Analysis of the buck converter working in 1st quadrant.

11. DC/AC transistor converters (1-phase, 3-phase). Voltage definition in the converter-motor system.

12. Control strategy of DC/DC, and DC/AC converters. PWM for DC converters, sinusoidal PWM.

13. Magnetic phenomena in the power electronics. Transformer theory. Mathematic models of the voltage transformer. Switch-mode supplies. DC/DC converters with the pulse transformer. Single-end buck converter.

Aims

To give the students the basic knowledge in the area of power elektronics. Basic theoretical and practical knowledges for the design of the power converters.

Specification of controlled education, way of implementation and compensation for absences

The attendance at the all numerical and laboratory exercises is required.

Classification of course in study plans

- Programme BKC-SEE Bachelor's, 2. year of study, winter semester, 6 credits, compulsory

#### Type of course unit

eLearning

**eLearning:** opened course