Power Electronics

Power electronics involves the study of electronic circuits intended to control the flow of electrical energy. These circuits handle power flow at levels much higher than the individual device ratings. In general terms, the task of power electronics is to process and control the flow of electric energy by supplying voltages and currents in a form that is optimally suited for user loads.

The history of power electronics has been closely allied with advances in electronic devices that provide the capability to handle high power levels. Applications of power electronics are expanding exponentially. It is not possible to build practical computers, cellphones, cars, airplanes, industrial processes, and a host of other everyday products without power electronics. In this article, we will learn about what is Power Electronics and the key terminologies, applications, types, advantages, and disadvantages of Power Electronics. Power Electronics runs the devices efficiently with the control and conversion of electric power.

What is Power Electronics?

Power electronics can be defined as the application of solid-state electronics for the control and conversion of electrical power. Power electronics is an area of study combining power, electronics, and control. It deals with the processing of high currents and voltages which further helps in the delivery of power to many areas for use.

The processing or converting of electric power is achieved through a power electronics converter also known as power converters or switching converters. Power electronics use electronic devices and circuits to efficiently and precisely control the flow of electrical energy for various applications. Power electronics play an important role in transforming and regulating the voltage, current, and frequency in different electrical applications. Power electronics have a wide range of applications in energy conversion and in transmission of motor control, and in renewable energy systems, and in electric vehicles. This branch of engineering has the high demand because of the growth and need of developing technologies

Blocks Representation of Power Electronics

The main blocks of Power Electronics System are:

• Source of Electrical Power
• Power electronic converter circuit
• Electrical Load
• Sensor or Sensing Unit or Feedback Circuit
• Control Unit or Controller

Block Diagram of Power Electronics

Source of Electrical Power

Mainly there are two types of Electrical energy sources. They are

• AC
• DC

Power electronic converter circuit

• Power electronic converter circuits converts the input power from the source to suitable form as required by the load.
• For example, it we have a DC source and need to supply an Induction motor, then it is necessary to convert DC to AC which is achieved using power electronic converter circuits.
• It works as a converter.
• During transient operation it retrieves the source and motor current in case of excessive current(overload).

Electrical Load

• The load can be a motor, battery etc. Usually loads are specified by their power rating and the type of source required. The ratings of the load largely decide the ratings of the power electronic converter circuit.

Sensor or Sensing Unit or Feedback Circuit

• The sensing and feedback circuits monitor the load conditions. For example, speed and output current are sensed in case of motor loads.
• Sensing unit helps in sensing the certain drive parameters like current or voltage may be required for protection or for closed loop operation.

Control Unit or Controller

• Control unit consists of drive circuits of the power electronic converter circuit.
• The drives of the switches are adjusted according to feedback and reference value.
• It consists of control circuits which is operated as power modulator as desired.

Working of Power Electronics System

Working of Power Electronic system consists of an electrical energy source, an power electronic converter circuit and an electrical load and a sensor and control circuit.

Power electronics deals with conversion and controlling of a large amount of electric power. The converter and controller are two major components in working. The power converters change one form of electric power into some other form with the use of a power semiconductor device. While power controllers are the ones that are responsible for producing control signals relative to turning on or off of the switching devices present within the circuit. This is divided into variety of applications:

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

The complete operation of the system will provide the desired signal of a particular frequency as shown in the block diagram given below and it include several steps:

Step 1: In power electronic systems, there can be an AC or DC source of electric power. The DC electric power source can be a DC generator, battery, etc. while the ac electric power source can be an alternator or induction generator. With the use of a controller, a signal of controlled power reaches the load end from the source via a converter.

Step 2: Next, The converter provides ac or dc electric power according to the load with variable voltage and frequency. Here we have said that the electric power at the output is dependent on the load and the reason behind this is when the load is dc motor then the converter provides output as adjustable dc voltage.

Step 3: Further, the parameters on which load is measured like the voltage, current, etc. acts as the input signal for the controller unit. These are known as feedback signals or controller input signals Along with the feedback signal, the controller is also provided with the reference input signal. The control signal generated by the controller is an outcome of the comparison made between the feedback signal and reference input signal and is regarded as the heart of the system. This control signal regulates the turning on and off of the switching devices of the power converter.

Final Output: In this way with proper control, the desired output is achieved at the load.

The power electronic circuit contains switches, lossless energy storage elements, and magnetic transformers. The controls take information from the Electrical energy source, the load, and the sensor, and then determine how the switches operate to achieve the desired conversion. The controls are built up with conventional low-power analog and digital electronics.

Working of Power Electronics

Types of Power Electronic Circuits

Power electronic circuits are mainly classified into four types :

• AC to DC Converter(Rectifiers)
• DC to DC Converters (Choppers)
• AC to AC Converters (Cycloconverters)
• DC to AC Converters (Inverters)

AC to DC Converter(Rectifiers)

These are also called as AC to DC converters or controlled rectifiers. The line commutated converters (controlled rectifiers) are used to convert a fixed voltage, fixed frequency AC power supply to obtain a variable DC output voltage. Rectifiers are power electronic circuits that are used to convert 1 phase or 3 phase AC input to DC output. The input is single phase or three phase AC supply normally available from the mains. The output is controlled DC voltage and current. If SCR’s are employed in these circuits, then it is referred to as controlled rectifiers. Since SCR’s can be turned off due to natural commutation, rectifiers are also referred to as line (Supply) commutated converters.

Applications of AC to DC Converters

• It is used in Speed control of DC motor in DC drives
• It is used in HVDC transmission
• It is used in Battery Chargers

AC to DC Converters

DC to DC Converters (Choppers)

The Choppers are power circuits which obtain power from fixed voltage DC supply and convert it into a variable DC Voltage. Choppers are power electronic circuits that convert fixed DC input voltage to fixed or variable DC output voltage. Choppers are popularly used in DC drive applications, where the speed of the motor can be controlled in forward and reverse direction. Choppers take input from a fixed DC source or from output of uncontrolled rectifier. Choppers employ forced commutation to turn off the Thyristors.

Applications of DC Choppers

• It is used in Speed control of Dc motors to Dc supply
• It is used in Sub-urban traction
• It is used in Switching power supplies

DC to DC Converters

AC to AC Converters (Cycloconverters)

AC voltage controllers convert the constant frequency, fixed voltage AC supply into variable AC voltage at the same frequency using line computation. Cycloconverters are power electronic converter circuits used to convert fixed AC input voltage to fixed or variable (Voltage or frequency) AC output. The output frequency is lower than the input frequency. Cycloconverters are popularly used for AC traction drives.

Applications of Cycloconverters

• It is used in AC traction vehicles
• It is used in gearless rotary kilns

AC to AC Converters

DC to AC Converters (Inverters)

Inverters are power electronic converter circuits used to convert fixed DC input to fixed or variable AC output. The inverters employ force commutation method to turn off the Thyristors. The input for the inverters is usually obtained from batteries. Inverters are used for speed control of Induction Motors. They are usually used in standby as emergency power supplies.

Applications of Inverters

• It is used in UPS Systems
• It is used in uninterrupted power supply to computers and computer lab
• It is used in Industrial AC drives using induction and synchronous motors

DC to AC Converters

What is Power Semiconductor Devices ?

Power semiconductor devices are used as on/off switches in power control circuit or it is used as a switch or rectifier in power electronics . A power semiconductor device is a semiconductor device used as a switch or rectifier in power electronics for example in a switch-mode power supply. Such a device is also called a power device or, when used in an integrated circuits. Power devices operate at lower switching speeds whereas signal devices operate at higher switching speeds. The powers semiconductor devices used extensively in power electronic circuits.

These power semiconductor devices are divided into three types:

• Diodes
• Thyristors
• Transistors

Power Diode

Diodes play a significant role in power electronics circuits. These are uncontrolled rectifying devices. It acts as a switch to perform various functions such as switches in rectifiers, change reversal of capacitor and energy transfer between components, voltage isolation, energy feedback from the load to power Source.

Thyristors

The thyristors are used extensively in power electronic circuits. They are operated as bistable switches, operating from of state to conducting state. The member of the Thyristors family are SCR, LASCR, RCT, GTO, SITH, and MCT.

Transistors

The power transistors have controlled turn-on and turn off characteristics. The switching speed of power transistor as much nigher than that of thyristors, and they are extensively used in dc-dc and dc-ac converters. The power transistors can classified as BJT, MOSFETs, SITs and IGBTs.

Application of Power Electronics

• Electric Transportation: Power electronics has countless applications in real life. It is used in electric vehicles for the charging and the discharging of the battery and regulate continuous power flow in the vehicle.
• Industrial drives : Power electronics which are used in industries are cement mills ,rolling mills ,wind system ,pumps ,elevators ; also used to improve efficiency and control the speed and torque of the motor.
• Energy storage : For the stable power conversion , energy storage in done in the batteries and in the other form.
• Power distribution and transmission: Power electronics which are used in utility system are smart grids ,FACTS,HDVC transmission, improving system efficiency , and preventing power losses.
• Renewable energy : Power electronics which is used in renewable energy are solar systems, turbines to convert the power into AC power and after that can be transmitted to power grid.

Advantages of Power Electronics

• Energy efficiency : Low efficiency due to low loss in the power semiconductor devices
• Reliability : High reliability of power electronic converter system.
• Durability: Long life and less maintenance due to absence of any moving system.
• Prompting: Fast dynamic response of power electronic system as compare to electro-mechanical system
• High speed switching : Power can be flow easily in the efficient way with the high speed switching.

Disadvantages of Power Electronics

• Power electronics converter have low overload capacity
• Power electronics converter circuit have a tendency to generate Harmonic in the supply system as well as in the load.
• It has Low power factor operation
• Regulation of power is difficult in power electronics converter.

Importance of Power Electronics

• Power electronics systems are used in a wide range of applications and have the potential to impact any area of ​​global industrial and social activity. From cellphones to pacemakers, and utilities to automobiles, power electronics, and the engineering behind those electronics are very influential in peoples’ daily lives.
• From power generation to transportation and communication technologies to average kitchen appliances, power electronics and the engineers behind these electronic devices are everywhere.

Future of Power Electronics

The future of power electronics is expected to be driven by:

• In the growth of renewable energy.
• In the development of smart grid technology.
• In the growth of the electric vehicle market.
• In the trend toward miniaturization and integration.
• Energy storage systems, such as batteries and supercapacitors, will play an increasingly important role in the future of power electronics
• The integration of artificial intelligence and machine learning will also play a significant role.

Conclusion

In this article we have seen what is power electronics and different types of type power electronic circuits and benefits and future range of applications of power electronics in every field. With some current trends in renewable energy. power electronics is not only the present but also the future of electrical and electronics engineering across the globe. The main purpose of power electronics is the processing and controlling of electric energy by giving sufficient voltage and current so that it will be suitable for various consumer applications. The processing or converting of electric power is achieved through a power electronics converter also known as power converters or switching converters.

FAQs on Power Electronics

What do you mean by power electronics?

Power electronics can be defined as the technology with the efficient conversion, control and conditioning of electric power by static means from its available input form into the required electrical output form.

What type of power electronics devices are used in Electrical vehicles?

Power electronics devices are used in Electrical vehicles includes components such as Inverters, DC/DC converters, and chargers.

How do we calculate power electronics system efficiency?

The power electronics system operates at the rated output-power level, and, by measuring the input power and output power, we can calculate the systems efficiency using the equation η=(POUT/PIN)×100%, where POUT is output power and PIN is input power.

Why power electronics is important?

Power electronics plays a important role in reducing energy waste and increasing power quality by using the efficiency of these power conversion systems.

Describe the types of power electronics circuits ?

Power electronic circuits are mainly classified into four types :

• AC to DC Converter(Rectifiers)
• DC to DC Converters (Choppers)
• AC to AC Converters (Cycloconverters)
• DC to AC Converters (Inverters)