Energy Processing and Smart Grid

CHAPTER 12CONVERTERS AND INVERTERS

12.1 INTRODUCTION

In order to operate a device properly, it needs to be supplied with the right voltage level. Converters and inverters are needed to achieve this. The main difference between converters and inverters is what they do to the voltage. An inverter changes DC voltage into AC voltage and either increases or decreases it into the appropriate level. A converter changes the voltage level but does not change its type; so an AC voltage would still be AC and a DC voltage would still be DC. Many appliances are designed to work with AC, while small-scale power generators often produce DC.

12.2 DEFINITIONS

A DC–DC converter is an electronic circuitry that converts DC from one power level to another. It is widely used in regulated, switch-mode DC power supplies and in DC motor drive applications, Figure 12.1.

Figure 12.1 A DC–DC converter system.

Typically, the input to these converters is an unregulated DC voltage, which is obtained by rectifying the line voltage. Therefore, it will fluctuate due to changes in the line-voltage magnitude. Switch-mode DC–DC converters are used to convert the unregulated DC input into a controlled DC output at a desired voltage level.

DC–AC converters are known as inverters. The function of an inverter is to change a DC input voltage to a symmetrical AC output voltage of desired magnitude and frequency. ...