Applications of Power Electronics

The first electronics revolution began in 1948 with the invention of the silicon transistor was proposed by Bell Labs and commercially produced by General Electric in the earlier fifties. Mercury Arc Rectifiers were well in use by that time and the robust and compact. In power electronics SCR was the first started replacing it in the rectifiers and cycloconverters. The second electronics revolution began with the development of a commercial thyristor by the General Electric Company in 1958 and was the beginning of a new era of power electronics. Since then, many different types of power semiconductor devices and conversion techniques have been introduced.

Generally, power electronics is the process of using semiconductor switching devices to control and convert electrical power flow from one form to another to meet a specific need. In other words, power electronics enables the control of the power flow as well as its form ac or dc and the magnitude of currents and voltages.

Having the most advanced technology for power electronic devices, silicon (Si) power devices can be processed with practically no material defect. However, silicon technology has some limitation for higher power utility applications. The primary limitation of Si devices is voltage blocking capacity due to the narrow band gap (1.1eV), which limits the voltage blocking capacity to less than to 10kv. For higher voltage applications, stacking packaged devices in series is required. Stacking package is expansive from a packing standpoint. Hence, there are incentives to develop devices having great voltage blocking capacity in a same or smaller device package. Such devices could be used in a variety of utility switching applications from distribution level (tens of kV) to transmission levels (>100kv).

During the last two decades, there has been a tremendous increase in the use of power electronic devices and are capable of performing various functions such as rectification, amplification, control and generation. In the medical field, some of the medical devices make use of electronics and ECG (electrocardiograph) used to find the condition of the heart of the patient, EEG (electroencephalograph) used for recording the electrical activity of the brain, EMG (electromyograph) used for determining the activity of the muscles, X-ray machine used for taking pictures of internal bone structure and also for treatment of some diseases.

Electronic circuits are employed for controlling many operations such as control of thickness of a job, moisture contents in a material

For quick arithmetical calculations electronic computers are employed for automatic record keeping and solving of complicated problems. Any computer can be connected to internet through an electronic device, called the modem. Electronic link is being used to transmit and receive e-mail and fax messages.

Use of automatic control system in industry is increased day by day. Speed of industrial motors is controlled through thyratrons, thyristors or magnetic amplifiers.

Instrumentation plays a vital role in any industry and research organization for precise measurement of various quantities. Accuracy of electronics instruments such as cathode-ray oscilloscope, strain gauges, frequency counter etc, is much higher than that of ordinary instruments. No research laboratory is completed without suitable electronic instruments.

Air traffic is controlled electronically. It is through the RADAR (Radio Detection and Ranging) that country is guarded from enemy aircraft. By employing RADAR, it is possible not only to detect, but also to determine the exact location and velocity of the enemy aircraft. Most of the sophisticated military attack and detection equipment are operated electronically.

Electronic circuits are employed for controlling many operations such as control of thickness of a job, moisture contents in a material. Electronic amplifiers are employed to control the operation of automatic door-openers, lightning systems, sound systems, power systems and safety devices.

Power electronics can be found in power system in many forms within the power system. These forms range from high voltage direct current (HVDC) converter station to a flexible ac transmission system (FACTS) devices that are used to control and regulate ac power grids, variable speed drives for motors, the electric drive in transportation systems, fault current limiting devices, the solid-state distribution transformer, and transfer switches.

The challenge facing the power system engineering today is to use existing transmission facilities to a greater effect. Improving utilization of the existing power systems is provided through the application of advanced control technologies in power electronics based equipment or FACTS. FACTS provide proven technical solutions to address new operating challenges being presented today. With that said, FACTS are too expensive to purchase, install, and maintain in the current utility systems.

Differences in essential features of devices call for special protection schemes particular for those devices.

Power electronics can provide utilities the ability to more effectively delivering power to their consumers while providing increased reliability to the bulk power system. Power electronics can also play a pivotal role in improving security of the nation’s electric grid. Although it is very difficult to quantify reliability benefits, studies show the estimated present value of aggregated attributes of reliable, modernized grid to be USD 638 to USD 802 billion over a twenty year horizon, with annualized values of between USD 51 and USD 64 billion/year. With that power electronics is not considered ideal systems. Some of the important issues the power electronics encounter include cost, reliability, cooling methods, efficiency, thermal management and control.

Power electronic converters often operate from the utility mains and are exposed to the disturbances associated with it. Even otherwise the transients associated with switching circuits and faults that occur at load point stress converters and devices. Consequently, several protections must be incorporated in a converter. Power semiconductor devices are commonly protected against:

• Overcurrent.
  • di/dt.
  • Voltage spikes or over-voltages.
  • Gate-under voltage.
  • Over voltage at gate.
  • Excessive temperature rise.
  • Electro-static discharge.

Some of these techniques are common for all devices and converters. However, differences in essential features of devices call for special protection schemes particular for those devices.

Applications of Power Electronic Devices

• High efficiency due to low loss in power semiconductor devices.
  • High reliability of power electronic converter systems.
  • Long life and less maintenance due to the absence of any moving parts.
  • Fast dynamic response of the power electronic systems.
  • Small size and less weight result in less floor space and lower installation cost.
  • Mass production of power semiconductor devices has resulted in lower cost of the converter equipment.

Semi-Conductor Devices

• Develop high-voltage, high-current SiC devices for utility applications.
  • Develop low-cost SiC IGBT devices to elevate the capability of power electronics in utility applications by replacing GTOs.

Wide Bandgap Materials

• Conduct system-level impact studies to evaluate the impact of wide bandgap semiconductors on the utility grid.
  • Develop high temperature packing to take advantage of the capability of SiC devices.
  • Develop innovative wide bandgap materials processes to create low cost, defect free wafers.

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