Power Electronics, A First Course, 2nd Edition

5 RECTIFICATION OF UTILITY INPUT USING DIODE RECTIFIERS

As discussed in the introduction to Chapter 1, the role of power electronics is to facilitate power flow, often in a controlled manner, between two systems shown in Figure 5.1: one of them a “source” and the other a “load.” Typically, power is provided by a single-phase or a three-phase utility source, for example, in adjustable-speed motor drives. (Of course, there are exceptions, for example, in wind turbines, where the wind-turbine generator is the source of power to the utility grid that acts like a “load.”)

FIGURE 5.1 Block diagram of power electronic systems.

Such power-electronic interfaces often consist of a voltage-link structure, discussed in Section 1.5.1, where the input from the AC source is first rectified into a DC voltage across a large capacitor. If reversing power flow is not an objective, it is possible to rectify the AC input, single-phase or three-phase, by means of diode rectifiers discussed in this chapter. The knowledge of such systems is essential for learning about thyristor converters, discussed in Chapter 13, which are used in important applications such as high-voltage DC transmission (HVDC) systems.

5.1 INTRODUCTION

In diode rectifiers, unless corrective action is taken as described in the next chapter, power is drawn by means of highly distorted currents, which have a deleterious effect on ...