Ing Ind - Inf (Mag.)(ord. 270) - MI (475) ELECTRICAL ENGINEERING - INGEGNERIA ELETTRICA

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A

ZZZZ

093588 - POWER ELECTRONICS

Obiettivi dell'insegnamento

The course deals with static converters, based on diodes, thyristors and controllable switches together with electromagnetic devices. The schemes, the operation, the control, the component data, together with the input and output quantities are analyzed. The main design criteria and some applications are also studied.

The goal is also to give the students a methodology to analyse new converters.

The course is based on:

a) theoretical lessons and numerical exercises;

b) computer simulations Matlab/Simulink; the students will be divided into groups with at most two people per computer;

c) experimental tests in the laboratory; the students will be divided into groups with at most three people per table.

Risultati di apprendimento attesi

After passing the exam, the student: will know the fundamental principles and the operation theory of several static converters (DdD1); will know some general design concepts used in Power Electronics (DdD1); will learn how to apply some concepts, learnt in other courses, to Power Electronics: in detail, reference is made to the thermal aspects, most important in the design of a converter, and to control theory, necessary to make a controlled converter operate (DdD2); will be able to apply his knowledge to other problems dealing with Power Electronics; reference is made to the applications to Electric Power Systems and Electrical Machines (DdD2, 3); will be able to simulate a converter in Matlab/Simulink and to design its control system, implementing it (DdD2). Datasheets of common static switches will be provided during the course: the student will learn how to pick up the necessary and useful information (DdD2). During the exam, the student should show the ability to find out the best way to solve a problem (DdD3, 5) and to describe some aspects of a converter in a sequential and understandable way (DdD4).

Argomenti trattati

1) The components. Diodes, thyristors and controllable switches; transformers and reactors for the conversion, auxiliary components (“snubbers”, inductors, capacitors for power factor correction and filtering).

2) General aspects. Real switches (characteristic curves, losses, delays,…); electrical and energetic quantities (average and RMS values, harmonics, power, efficiency, power factor).

3) Thermal behaviour of the converters. Systems with one or two time constants, thermal transient impedance, cooling; calculation of the thermal resistance of a heat-sink.

4) Line-commutated a.c-d.c. conversion. Single – phase and three – phase Graetz rectifier, with different types of load (RL or RC); commutation, phase–control; harmonic analysis; twelve–pulse converters. Filter for the harmonic components of the current injected into the grid. Basic concepts on HVDC.

6) D.c. – a.c. conversion. Two – level, single – phase and three – phase VSI inverters: schemes, modulation techniques; harmonic analysis; Three – level VSI inverter; a.c.-d.c. conversion with PF = 1; operation as an inverter and as a rectifier. Design of a control system.

7) Compensation of the reactive power: thyristor-controlled inductors; Statcom.

8) Zero voltage/current switching converters: analysis of one converter.

Prerequisiti

The student should have some basic knowledge of: Electric Power Systems, Electrical machines, Automatic controls.

Modalità di valutazione

The exam consists in a written test (three hours) and an optional oral test (30-45 minutes) for those who wish to improve their mark. The oral test is mandatory for written marks greater or equal to twenty-eight. The teacher may decide to require the oral test, if he thinks it is necessary. The student must: *) express a reasoning in a linear way: the assumptions, the development and the conclusions (DdD4); a neat written task is required (DdD4); *) explain the operation of a converter from an analytical view-point, through schemes, formulas and plots (DdD1); *) solve the numerical exercises, analysing the results critically (DdD1, 2); *) make correlations between different subjects (DdD2). The numerical exercises explained during the lectures are a subject of the exam.

Bibliografia

Mohan - Undeland - Robbins, Power Electronics - Converters, Applications, and Design, Editore: Wiley, Anno edizione: 2003
Some papers available on Beep www.polimi.itS. Crepaz, Thermal behaviour of static switches, Editore: CUSL Note:

Photocopy available at the CUSL bookshop (building 3 Leonardo)