Power Electronics Applied to Industrial Systems and Transports, Volume 1

Synthetic Methodology to Converters and Components Technology

Nicolas Patin

• Publisher: ISTE Press - Elsevier
• Year: 2015
• Print ISBN:
  9781785480003
• eBook ISBN:
  9780081004593
• Topic: Technology & Engineering
• Subtopic: Industrial Engineering
• Index: Technology & Engineering

Power electronics is based on the switching operating mode of semiconductor components. On this basis, the concepts of type (voltage or current) and reversibility of interconnected sources make it possible to apply a methodology for the synthesis of various types of converters.Here the author presents the major types of components available, always from a user's point of view, with the gate drive/fire control and other auxiliary circuits that are required for their proper functioning (snubbers, for example). The different passive components (capacitors, coils and transformers) are discussed, as well as printed circuit technology, especially in the aspect of their design.This book also focuses on the importance of packaging by reviewing the electrical representation of components' thermal models and the currently available electronics' cooling technologies. Modeling is discussed, as well as different technological aspects used in the engineering design of an electronic power converter, useful for obtaining satisfactory performance and reliability. - Presenting the essential notions in power electronics from both the theoretical and technological perspectives - Dedicated chapters with a focus on connection rules, reversibility and impact choices of switches for converter synthesis - Presented from a user's perspective to enable you to apply the theory of power electronics to practical applications

1

Theoretical Tools and Active Components for Power Electronics

Abstract

In studying linear electric circuits, we distinguish between classic passive dipoles (which absorb energy, although this energy value may be null):

– resistors;

– inductors;

– capacitors.

And active dipoles (which supply energy: this is generally positive, but can also be negative) in the form of sources of:

– voltage (voltage at the terminals is imposed, and independent of the current delivered);

– current (carrying an imposed current, independent of the voltage at the terminals).

Note that, generally speaking, a dipole consisting of a current source and another dipole will behave in the same manner as the current source alone in relation to the circuit to which it is connected. At the same time, we see that a dipole consisting of a voltage source in parallel with another dipole behaves in the same way as the voltage source alone in relation to the circuit.

Keywords

Antiparallel diode transistors

Bipolar transistors

GTO thyristor

H-bridge topology

IGBT transistors

Integrated gate-commutated thyristor (IGCTs)

Metal oxide semiconductor field-effect transistor (MOSFET)

Passive linear dipoles

Safe operating areas (SOAs)

Thyristors

1.1 Electrical circuits and power electronics

1.1.1 General case

In studying linear electric circuits, we distinguish between classic passive dipoles (which absorb energy, although this energy value may be null):

– resistors;

– inductors;

– capacitors.

And active dipoles (which supply energy: this is generally positive, but can also be negative) in the form of sources of:

– voltage (voltage at the terminals is imposed, and independent of the current delivered);

– current (carrying an imposed current, independent of the voltage at the terminals).

Note that, generally speaking, a dipole consisting of a current source and another dipole will behave in the same manner as the current source alone in relation to the circuit to which it is connected. At the same time, we see that a dipole consisting of a voltage source in parallel with another dipole behaves in the same way as the voltage source alone in relation to the circuit.

Another useful point to note relates to the interconnection of sources. The connection of two current sources creates a conflict between the two elements, as they may impose different values on the same current. Similarly, the parallel use of two voltage sources creates conflict if their values are different. However, it is entirely possible to connect two sources of different natures in series or in parallel (i.e. a voltage source with a current source).

These definitions are used “as is” or with minor modifications in the context of power electronics, as we will see later in this chapter.

1.1.2 Extension to power electronics

These components are all used in power electronics, but the definitions of voltage and current sources are less restrictive in this domain than in more general situations:

– in power electronics, a voltage source is a dipole with terminals where the voltage cannot be discontinuous;

– similarly, a current source is a dipole carrying a current which cannot be discontinuous.

Thus, the sources defined in a general context are still considered in the same manner in power electronics, but, by extension, we consider that:

– a dipole obtained by connecting an inductor and any dipole in series is a current source;

– a dipole obtained by connecting a capacitor and any dipole in parallel is a voltage source.

As we have already seen, power electronics is not limited to the use of passive linear dipoles (resistors, inductors and capacitors) and voltage or current sources, but makes use of switches (transistors, diodes, etc.). Consequently, we need to open circuits (OFF state) or provoke short-circuits (ON state):

– an open circuit may be assimilated to a source of null current;

– a short-circuit may be assimilated to a source of null voltage.

The rules defined above concerning the interconnection of voltage and current sources may be applied to this basis, enabling us to:

– short-circuit a current source;

– open the circuit of a voltage source.

But we cannot:

– short-circuit a voltage source;

– open the circuit of a current source.

This final point is important in the construction shown in Figure 1.15, where a free-wheeling diode is needed in parallel to an inductive load (i.e. a current source in the sense of power electronics). This set of rules is presented in Figure 1.1. A classification of sources/loads according to their nature (current source/voltage source) is given in Table 1.1 (this is not an exhaustive list).

Figure 1.1 Rules for circuits in power electronics

Table 1.1

Classification of current or voltage source types

Current sources	Voltage sources
DC machine	Battery
Synchronous machine (generally three-phase)	Solar panel
Asynchronous machine (generally three-phase)	Fuel cell
Transformer winding	Piezoelectric transformer
Inductor dipole in series	Condenser dipole in parallel
Electrical network with finite power	Electrical network with infinite power

The ideal switch K (see Figure 1.2) is a dipole which may be considered to have infinite resistance when open, and zero resistance when closed. It can therefore carry a positive or negative current I_K when open and tolerate a positive or negative voltage V_K at its terminals when turned off. This type of component is bidirectional for both voltage and current. This gives us a voltage/current characteristic made up of two full lines following the two axes of the plane (I_K,V_K). Each half-line of this characteristic, starting from the origin of the plane, is known as a segment. The ideal switch is thus a 4 segment switch. As we will see, in practice, real components have a lower number of segments (with the exception of the triac).

Figure 1.2 The ideal switch and its current/voltage characteristic

The open (turned off – noted OFF) and closed (n...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright page
• Preface
• Introduction
• 1. Theoretical Tools and Active Components for Power Electronics
• 2. Thermics, Packaging and Power Component Technologies
• 3. Auxiliary Converter Circuits
• 4. Passive Components – Technologies and Dimensioning
• 5. Designing Printed Power Circuits
• Appendix: Formulas for Electrical Engineering and Electromagnetism
• Bibliography
• Index