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POWER ELECTRONICS

Power electronics is the application of solid-state electronics to the control and conversion of electric power. In power electronics substantial amounts of electrical energy are processed. The capabilities and economy of power electronics system are determined by the active devices that are available. Power electronic devices may be used as switches, or as amplifiers. Semiconductor devices used as switches can approximate this ideal property and so most power electronic applications rely on switching devices on and off, which makes systems very efficient as very little power is wasted in the switch.

Solid-state devices
Diode
SCR
GTO
TRIAC
MOSFET
BJT
IGBT
Mass Controlled Thyristor(MCT)
Integrated gate commutated Thyristor(IGCT)

AC/DC converters
AC/DC converters (rectifiers) is an electronic device which is connected to the mains (computer, television etc.). These may simply change AC to DC or can also change the voltage level as part of their operation.

AC/AC converters
AC/AC converters are used to change either the voltage level or the frequency (international power adapters, light dimmer). In power distribution networks AC/AC converters may be used to exchange power between utility frequency 50 Hz and 60 Hz power grids.

C converters
DC/DC converters are used in most mobile devices (mobile phones, PDA etc.) to maintain the voltage at a fixed value whatever the voltage level of the battery is. These converters are also used for electronic isolation and power factor correction. A power optimizer is a type of DC/DC converter developed to maximize the energy harvest from solar photovoltaic or wind turbine systems.

DC/AC converters

DC/AC converters (inverters) are used primarily in UPS or renewable energy systems or emergency lighting systems. Mains power charges the DC battery. If the main fails, an inverter produces AC electricity at mains voltage from the DC battery. Solar inverter, both smaller string and larger central inverters, as well as solar micro-inverter are used in photovoltaics as a component of a PV system.

POWER SYSTEMS
An electric power system is a network of electrical components used to supply, transfer and use electric power. An example of an electric power system is the network that supplies a region's homes and industry with power for sizable regions, this power system is known as the grid and can be broadly divided into the generators that supply the power, the transmission system that carries the power from the generating centers to the load centers and the distribution system that feeds the power to nearby homes and industries. Basics of electric power
Electric power is the product of two quantities: current and voltage. These two quantities can vary with respect to time (AC power) or can be kept at constant levels (DC power).Most refrigerators, air conditioners, pumps and industrial machinery use AC power whereas most computers and digital equipment use DC power (the digital devices you plug into the mains typically have an internal or external power adapter to convert from AC to DC power). AC power has the advantage of being easy to transform between voltages and is able to be generated and utilized by brushless machinery. DC power remains the only practical choice in digital systems and can be more economical to transmit over long distances at very high voltages.

Smart grid
A smart grid is a modernized electrical grid that uses information and communications technology to gather and act on information, such as information about the behaviors of suppliers and consumers, in an automated fashion to improve the efficiency, reliability, economics, and sustainability of the production and distribution of electricity.

Microgrid
A microgrid is a small-scale power grid that can operate independently or in conjunction with the area’s main electrical grid. Any small-scale localized station with its own power resources, generation and loads and definable boundaries qualifies as a microgrid. Microgrid can be intended as back-up power or to bolster the main power grid during periods of heavy demand. Often, microgrid involves multiple energy sources as a way of incorporating renewable power. Other purposes include reducing costs and enhancing reliability.

SCADA systems
In large electric power systems, Supervisory Control and Data Acquisition (SCADA) is used for tasks such as switching on generators, controlling generator output and switching in or out system elements for maintenance. The first supervisory control systems implemented consisted of a panel of lamps and switches at a central console near the controlled plant. The lamps provided feedback on the state of plant (the data acquisition function) and the switches allowed adjustments to the plant to be made (the supervisory control function). Today, SCADA systems are much more sophisticated and, due to advances in communication systems, the consoles controlling the plant no longer need to be near the plant itself. Instead it is now common for plant to be controlled by equipment similar to (if not identical to) a desktop computer. The ability to control such plant through computers has increased the need for security and already there have been reports of cyber-attacks on such systems causing significant disruptions to power systems.




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