Power Electronics: Introduction to Electric Power Conversion

In the modern society, the availability of electric power has become an essential commodity. Electricity today has made almost every part of the society more functional in many ways. It is responsible to provide better health care, better information collection, storage, processing, heating, cooling, mobility and transport.

Where does power electronics fit into this electric power supply?

In any energy conversion system, we need a controller to supply and convert power efficiently through determining the demand and supply of power between the source and sink. Now, when we talk about sources and sinks in general it can be both from the same type of energy conversion (e.g.: — electrical to electrical energy) or different (e.g.: — electrical to mechanical or vice versa). Conversion procedures for the second type of energy requires a varied set of machinery and equipment which are not the concern for this article. We would like to focus our interest on the first type of conversion i.e., electrical to electrical conversion for this article.

What is electrical power conversion?

Before we jump into understanding the nuances of electric power conversion, we need to understand what we are trying to achieve from this power conversion. What are the multiple forms of electrical power that exists and the need for their conversion?

We already know electrical power can classified into two main categories: — Direct Current (DC) and Alternating Current (AC).

Fun Important Note: We should never use “DC current”: — It is like saying “Direct Current Current” or people like saying “Chai Tea” which means “Tea Tea”.

What is DC or Direct Current?

Direct Current is defined as flow of electric charge in a single direction (along the potential gradient). It can flow through conductors (wires), semiconductors (used in power converters) or even as electrons or ion beams in vacuum (wireless transmission of electricity). The best example to remember DC is a simple battery powered lamp or a torch running in battery.

Interesting FACT!!! Direct Current was archaically as galvanic current (Luigi Galvani, the discoverer of electric current produced by chemical action — Batteries and “animal electricity”)

What is AC or Alternating Current?

Alternating Current is defined as the flow of electric charge which periodically reverses direction and magnitude as a function of time. The socket you plugin your mobile or your laptop provide AC to the charger.

Electric Power Conversion

We have got a brief insight on the two type of electric power we want to convert. This make four combinations of power conversion which can be achieved using power electronic converters. What are the four combinations? AC to AC, DC to DC, AC to DC, DC to AC.

Power electronics can thus be defined as the branch of electrical engineering which studies the control and conversion of electric power using semiconductor switches.

Let us now name the power electronic devices we use for converting electric power in combinations mentioned above.

· AC to AC: — 1. AC voltage Converters (Magnitude conversion):-Switched Mode Power Supply (SMPS) in UPS. 2. Cyclo-converters (frequency conversion):-§ Electric Traction, Steel rolling mills.

· DC to DC: -1. Choppers: § Electric vehicles with DC motors (battery to Choppers to DC motor)

· AC to DC:- 1. Rectifiers: § Battery Chargers for mobile, laptops, Electric Vehicles.

· DC to AC: -1. Inverters: §Household emergency power supply.

Block Diagram depicting various power electronic converters

References:

  1. Modern Power Electronics, Second Edition by Andrzej Trzynaclowski.

An Electrical Engineering student for life. Sharing my thoughts on some interesting topics in this domain.