Definition of power electronics
It is the
application of solid-state electronics for the control and conversion of
electric power.
OR
Difference between electronics and power electronics
We can say power electronics is a special field where optimum energy is provided to the load.We should always have on thing in our minds that what is electronic when we are at the spot to discuss power electronics "ELECTRONICS" is simply flow of electrons.
It also refers to a
subject of research in electronic and electrical engineering which deals with
design, control, computation and integration of nonlinear, time varying energy
processing electronic systems with fast dynamics.
 |
| flip flop circuit |
Importance of Power Electronics
The basic functions of importance for power
electronics are:
(1) power conversion, ac to dc, dc to ac, ac
to ac
(2) power conditioning to remove distortion,
harmonics, voltage dips and overvoltage’s.
(3) high speed and/or
frequent control of electrical parameters such as currents, voltage impedance,
and phase angle,.
(4)
high speed and/or frequent circuit interruption transfer, and current limiting
functions.
Power electronics is a subject of interdisciplinary nature. To
design and build control circuitry of
a power electronic application, one needs knowledge of several areas, which are
listed below.
·
Design of analogue and digital electronic circuits, to build the
control circuitry.
·
Microcontrollers and digital signal processors for use in
sophisticated applications.
- Many power electronic circuits have an electrical
machine as their load. In ac variable speed drive, it may be a reluctance
motor, an induction motor or a synchronous motor. In a dc variable speed
drive, it is usually a dc shunt motor.
- In a circuit such as an inverter, a transformer may be
connected at its output and the transformer may have to operate with a
nonsinusoidal waveform at its input.
- A pulse transformer with a ferrite core is used
commonly to transfer the gate signal to the power semiconductor device. A
ferrite-cored transformer with a relatively higher power output is also
used in an application such as a high frequency inverter.
- Many power electronic systems are operated with
negative feedback. A linear controller such as a PI controller is used in
relatively simple applications, whereas a controller based on digital or
state-variable feedback techniques is used in more sophisticated
applications.
- Computer simulation is often necessary to optimize the
design of a power electronic system. In order to simulate, knowledge of
software package such as MATLAB and the know-how to model nonlinear
systems may be necessary.
Power electronics
Power electronics are semi-conductor based devices that are able to switch quantities of power ranging from a few hundred watts to several hundred megawatts. Despite their relatively simple function, their speed of operation (typically in the order of nanoseconds) means they are capable of a wide range of tasks that would be difficult or impossible with conventional technology. The classic function of power electronics is rectification, or the conversion of AC-to-DC power, power electronics are therefore found in almost every digital device that is supplied from an AC source either as an adapter that plugs into the wall (see photo in Basics of Electric Power section) or as component internal to the device. High-powered power electronics can also be used to convert AC power to DC power for long distance transmission in a system known as HVDC. HVDC is used because it proves to be more economical than similar high voltage AC systems for very long distances (hundreds to thousands of kilometres). HVDC is also desirable for interconnects because it allows frequency independence thus improving system stability. Power electronics are also essential for any power source that is required to produce an AC output but that by its nature produces a DC output. They are therefore used by many photovoltaic installations both industrial and residential.
Power electronics also feature in a wide range of more exotic uses. They are at the heart of all modern electric and hybrid vehicles—where they are used for both motor control and as part of the brushless DC motor. Power electronics are also found in practically all modern petrol-powered vehicles, this is because the power provided by the car's batteries alone is insufficient to provide ignition, air-conditioning, internal lighting, radio and dashboard displays for the life of the car. So the batteries must be recharged while driving using DC power from the engine—a feat that is typically accomplished using power electronics. Whereas conventional technology would be unsuitable for a modern electric car, commutators can and have been used in petrol-powered cars, the switch to alternators in combination with power electronics has occurred because of the improved durability of brushless machinery.
Some electric railway systems also use DC power and thus make use of power electronics to feed grid power to the locomotives and often for speed control of the locomotive's motor. In the middle twentieth century, rectifier locomotives were popular, these used power electronics to convert AC power from the railway network for use by a DC motor. Today most electric locomotives are supplied with AC power and run using AC motors, but still use power electronics to provide suitable motor control. The use of power electronics to assist with motor control and with starter circuits cannot be underestimated and, in addition to rectification, is responsible for power electronics appearing in a wide range of industrial machinery. Power electronics even appear in modern residential air conditioners.
Power electronics are also at the heart of the variable speed wind turbine. Conventional wind turbines require significant engineering to ensure they operate at some ratio of the system frequency, however by using power electronics this requirement can be eliminated leading to quieter, more flexible and (at the moment) more costly wind turbines. A final example of one of the more exotic uses of power electronics comes from the previous section where the fast-switching times of power electronics were used to provide more refined reactive compensation to the power system.Courtesy of wikipedia,,,,,,
No comments:
Post a Comment