Advantages and Application of Power Electronic

Definition

The increasing focus on electrification for a cleaner environment has fueled the need for electric power in different forms. Power electronics is the branch of electrical engineering that deals with the processing of high voltages and currents to deliver power that supports a variety of needs. From household electronics to equipment in space applications, these areas all need stable and reliable electric power with the desired specifications. Power supply in one form is processed using power semiconductor switches and control mechanisms to another form, supplying a regulated and controlled power. While switched-mode power supplies are a common application of power electronics where power density, reliability, and efficiency are of prime importance, motor control is gearing up with more electrification in transportation systems. Precise control and efficiency are key characteristics for power control applications. The study of power electronics is thus multidisciplinary, involving semiconductor physics, electrical motors, mechanical actuators, electromagnetic devices, control systems, and so on.

How Do Power Electronics Work?

Power electronic systems are used in a variety of applications, such as:

• Power Generation
• Power Transmission
• Power Distribution
• Power Control

In all these applications, the input voltages and currents are switched using power semiconductor devices to provide desired outputs. The construction of basic semiconductor devices such as diodes, FETs, and bipolar junction transistors (BJTs) are altered to withstand high voltages and currents. As a result, we have silicon-controlled thyristors (SCRs), power diodes, power metal oxide semiconductor field effect transistors (MOSFETs), power BJTs, insulated gate bipolar transistors (IGBTs), gate turn-off thyristors (GTOs), and so on. The device selection is based on the power levels, the switching frequency requirements, efficiency, and the nature of inputs and outputs. For instance, in an EV powertrain, the power handled is of the order of kW. In such applications, power MOSFETs which can withstand the high voltage and switch at higher frequencies are commonly used. In the case of power transmission, where the handled power is of the order of few megawatts, silicon-controlled rectifiers (SCRs) are used.

The block diagram of a typical power electronic system is shown in the figure below.

Figure 1: Block Diagram of a Typical Power Electronics System

Types of Power Electronic Circuits

As mentioned in the previous sections, power electronic circuits control the input and output power. There are several types of power converters based on the type of application. When we consider the power source, there are two main types of power sources, namely alternating current (AC) and direct current (DC). This forms four basic types of power electronics circuits shown in the figure below. .

Basic types of power converters

Figure 2: Basic Types of Power Converters

1. AC-to-DC Converters
2. DC-to-DC Converters
3. DC-to-AC Converters (commonly known as inverters)
4. AC-to-AC Converters (commonly known as cycloconverters)

Types of Power Electronic Circuits

There are basically five types of power electronic circuits; each one is based on different purposes:

• To convert fixed AC to variable DC such as full wave or half wave rectifiers – Rectifiers are used.
• To convert fixed DC to variable DC – Choppers are used.
• To convert DC to AC having a variable frequency and amplitude – Inverters are used.
• To convert fixed AC to variable AC at the same input frequency – Voltage Regulators are used.
• To convert fixed AC to AC with variable frequency – Cycloconverters are used.

Other classifications of power converters include the following:

    1. Based on the isolation between input and output:

• Non-isolated Converters
• Isolated Converters

    2. Based on the type of switching:

• Hard-switched Converters
• Soft-switched Converters

    3. Based on the connection to the power grid:

• Grid-connected Converters
• Offline Converters

The Importance of Power Electronics

The drive towards more electrification has resulted in the need for more electric power. Apart from power generation, power processing plays a key role in efficient utilization of the available power. It is important that the raw power is converted to a form that is usable in different applications. Power electronics plays a pivotal role in providing power based on the desired specifications. The basic application which shows the significance of power electronics in our day-to-day life is the fan regulator. Before the advent of solid-state fan regulators, bulky and lossy resistive fan regulators were used. To control the fan speed, the AC mains voltage is passed through a resistor that is connected in series with the fan. So, when the fan is on, there is constant power dissipation in the series resistor. Research has come up with more innovative ways of controlling the fans or motors, in general, by controlling voltage and frequency. This is possible with the availability of power semiconductor devices.

In aerospace applications, especially in space applications, size, weight, and reliability are critical parameters. If power is handled at low frequencies, the transformers and other energy storage elements occupy a huge amount of space. With switching converters that work at high switching frequencies, the size of the energy storage elements is drastically reduced.  The size of these components is inversely proportional to the switching frequency. So, devices with shorter switching times help to reduce the overall size and weight of systems.

State-of-the-art power electronic systems are capable of handling power from a few watts to several megawatts, enabling efficient and reliable interfaces between raw power and regulated power. As a result,  hydraulic and mechanical actuators are being replaced with electric motors that can be controlled precisely using power electronic interfaces.

The Benefits of Power Electronics

Electric power is scarce, and it is of prime importance to deliver the power to the loads with minimum losses. Advancements in power semiconductor research has resulted in more efficient chemistries such as silicon carbide and gallium nitride. The benefits of power electronics are:

1. High power density power supplies
2. Improved efficiency of up to 99% in power conversion
3. Noise-sensitive applications such as in medical devices are also transitioning to switching power supplies because of the efficiency and reliability
4. Power can be made available in the desired form and level as per specifications
5. Increased clean power generation using power electronic interfaces to connect the sources to grid
6. Wireless power transfer

Application of Power Electronics in Real Life

• A whole lot of power electronics applications that we use in our daily life, such as a fan regulator, air-conditioning, induction cooking, light dimmer, emergency lights, vacuum cleaners, personal computers, UPS, battery charges, etc., are the major applications of power electronics.
• Power electronics are also extensively used in automotive applications, like hybrid electric vehicles, trolleys, subways, forklifts, etc. A modern car itself is an example of power electronics that has some components like windshield wiper control, ignition switch, adaptive front lighting, electric power steering, interior lighting, etc. Apart from these, power electronics are widely used in ships and modern traction systems.
• Power electronics are used in industries since the industries have a huge installation of high-power motors that are controlled by power electronic drives, for instance, cement mills, rolling mills, compressor pumps, fans, elevators, textile mills, blowers, elevators, rotary kilns, etc. Some other applications consist of arc furnaces, welding, heating applications, construction machinery, excavators, emergency power systems, etc.
• Power electronics are used in defence and aerospace to supply power to aircraft, advance control in missiles, satellites, unmanned vehicles, space shuttles, and several other equipment of defence.
• Power electronics are used in the generation of renewable energy, such as solar, wind etc., which needs storage systems and conversion systems, and power conditioning systems in order to become usable.

Advantages of Power Electronics Converters

The benefits of power electronic converters are:

• They are highly reliable and have a long life.
• There is very less power loss while using electronic converters.
• Power electronic converters are efficient, and they have a quick response; they are small in size and less in weight.

Disadvantages of Power Electronics Converters

The drawbacks of power electronic converters are:

• Power electronic converters have low overload capacity.
• Power electronic converters are very expensive.

Frequently Asked Questions (FAQs)

Q1 What is power electronics?

To deliver power that supports a variety of needs, there exists a branch of electrical engineering called power electronics; this branch basically deals with the processing of high voltages and currents.

Q2 What is current?

The rate of flow of electrons in a conductor is known as electric current. The SI Unit of electric current is the Ampere.

Q3 Define voltage.

Voltage can be defined as the difference in electric potential between two points. The quantity of voltage is generally measured by a unit known as the volt denoted by V.

Q4 What are the disadvantages of power electronics converters?

Power electronic converters have low overload capacity. Power electronic converters are very expensive.

Q5 How many types of power electronics circuits are there?

There are basically five types of power electronics circuits.