Editing Power electronics (section)

== Applications ==

Applications of power electronics range in size from a [[switched mode power supply]] in an [[AC adapter]], battery chargers, audio amplifiers, [[fluorescent lamp]] ballasts, through [[variable frequency drive]]s and DC motor drives used to operate pumps, fans, and manufacturing machinery, up to gigawatt-scale [[high voltage direct current]] power transmission systems used to interconnect electrical grids.<ref>{{Cite web |title=Reliance Electric 57C494 {{!}} Automation Industrial |url=https://57c494.com/blog |access-date=2024-01-10 |website=57c494.com |language=en}}</ref> Power electronic systems are found in virtually every electronic device. For example:
* [[DC-to-DC converter|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 [[PV system|solar photovoltaic]] or [[wind turbine]] systems.
* AC/DC converters ([[rectifier]]s) are used every time an electronic device 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 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&nbsp;Hz and 60&nbsp;Hz power grids.
* DC/AC converters ([[power inverter|inverters]]) are used primarily in [[Uninterruptible Power Supply|UPS]] or renewable energy systems or [[emergency light]]ing systems. Mains power charges the DC battery. If the mains 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.

Motor drives are found in pumps, blowers, and mill drives for textile, paper, cement and other such facilities. Drives may be used for power conversion and for motion control.<ref name=Bose_Motion_Control>{{cite journal|last=Bose|first=Bimal K.|title=Power Electronics and Motion Control – Technology Status and Recent Trends|date=September–October 1993}}</ref> For AC motors, applications include [[variable-frequency drive]]s, [[motor soft starter]]s and excitation systems.<ref name=Bose_Motor_Drives>{{cite journal|last=Bose|first=Bimal K.|title=Power Electronics and Motor Drives Recent Progress and Perspective|date=February 2009}}</ref>

In [[hybrid electric vehicle]]s (HEVs), power electronics are used in two formats: series hybrid and parallel hybrid. The difference between a series hybrid and a parallel hybrid is the relationship of the electric motor to the [[internal combustion engine]] (ICE). Devices used in electric vehicles consist mostly of dc/dc converters for battery charging and dc/ac converters to power the propulsion motor. [[Electric multiple unit|Electric trains]] use power electronic devices to obtain power, as well as for vector control using [[pulse-width modulation]] (PWM) rectifiers. The trains obtain their power from power lines. Another new usage for power electronics is in elevator systems. These systems may use [[thyristor]]s, inverters, [[permanent magnet]] motors, or various hybrid systems that incorporate PWM systems and standard motors.<ref name=Yano_Power_Electronics_Japan>{{cite journal|last=Yano|first=Masao|author2=Shigery Abe |author3=Eiichi Ohno |title=History of Power Electronics for Motor Drives in Japan|year=2004}}</ref>

=== Inverters ===

In general, inverters are utilized in applications requiring direct conversion of electrical energy from DC to AC or indirect conversion from AC to AC. DC to AC conversion is useful for many fields, including power conditioning, harmonic compensation, motor drives, renewable energy grid integration, and [[solar panels on spacecraft|spacecraft solar power]] systems.

In power systems it is often desired to eliminate harmonic content found in line currents. VSIs can be used as active power filters to provide this compensation. Based on measured line currents and voltages, a control system determines reference current signals for each phase. This is fed back through an outer loop and subtracted from actual current signals to create current signals for an inner loop to the inverter. These signals then cause the inverter to generate output currents that compensate for the harmonic content. This configuration requires no real power consumption, as it is fully fed by the line; the DC link is simply a capacitor that is kept at a constant voltage by the control system.<ref name=Rashid3 /> In this configuration, output currents are in phase with line voltages to produce a unity power factor. Conversely, VAR compensation is possible in a similar configuration where output currents lead line voltages to improve the overall power factor.<ref name=Trzynadlowski />

In facilities that require energy at all times, such as hospitals and airports, UPS systems are utilized. In a standby system, an inverter is brought online when the normally supplying grid is interrupted. Power is instantaneously drawn from onsite batteries and converted into usable AC voltage by the VSI, until grid power is restored, or until backup generators are brought online. In an online UPS system, a rectifier-DC-link-inverter is used to protect the load from transients and harmonic content. A battery in parallel with the DC-link is kept fully charged by the output in case the grid power is interrupted, while the output of the inverter is fed through a low pass filter to the load. High power quality and independence from disturbances is achieved.<ref name=Rashid3 />

Various AC motor drives have been developed for speed, torque, and position control of AC motors. These drives can be categorized as low-performance or as high-performance, based on whether they are [[scalar-controlled]] or [[vector-controlled]], respectively. In scalar-controlled drives, fundamental stator current, or voltage frequency and amplitude, are the only controllable quantities. Therefore, these drives are employed in applications where high quality control is not required, such as fans and compressors. On the other hand, vector-controlled drives allow for instantaneous current and voltage values to be controlled continuously. This high performance is necessary for applications such as elevators and electric cars.<ref name=Rashid3 />

Inverters are also vital to many renewable energy applications. In photovoltaic purposes, the inverter, which is usually a PWM VSI, gets fed by the DC electrical energy output of a photovoltaic module or array. The inverter then converts this into an AC voltage to be interfaced with either a load or the utility grid. Inverters may also be employed in other renewable systems, such as wind turbines. In these applications, the turbine speed usually varies, causing changes in voltage frequency and sometimes in the magnitude. In this case, the generated voltage can be rectified and then inverted to stabilize frequency and magnitude.<ref name=Rashid3 />

=== 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.<ref>{{cite web | url =http://www.pnl.gov/main/publications/external/technical_reports/PNNL-17167.pdf | title = Pacific Northwest GridWise™ Testbed Demonstration Projects, Part I. Olympic Peninsula Project | access-date = 2014-01-15 | author = D. J. Hammerstrom|display-authors=etal}}</ref><ref>{{cite web | url = http://energy.gov/oe/technology-development/smart-grid | title = Smart Grid / Department of Energy | access-date = 2012-06-18 | author = U.S. Department of Energy}}</ref>

Electric power generated by [[wind turbine]]s and [[hydroelectric]] turbines by using [[induction generator]]s can cause variances in the frequency at which power is generated. Power electronic devices are utilized in these systems to convert the generated ac voltages into high-voltage direct current ([[HVDC]]). The HVDC power can be more easily converted into three phase power that is coherent with the power associated to the existing power grid. Through these devices, the power delivered by these systems is cleaner and has a higher associated power factor. Wind power systems optimum torque is obtained either through a gearbox or direct drive technologies that can reduce the size of the power electronics device.<ref name=Carrasco_Smart_Grid>{{cite journal|last=Carrasco|first=Juan Manuel|author2=Leopoldo Garcia Franquelo |author3=Jan T. Bialasiewecz |author4=Eduardo Galvan |author5=Ramon C. Portillo Guisado |author6=Ma. Angeles Martin Prats |author7=Jose Ignacio Leon |author8=Narciso Moreno-Alfonso |title=Power-Electronic Systems for the Grid Integration of Renewable Sources: A Survey|date=August 2006|volume=53|issue=4|page=1002|doi=10.1109/tie.2006.878356|citeseerx=10.1.1.116.5024|s2cid=12083425}}</ref>

Electric power can be generated through [[photovoltaic cell]]s by using power electronic devices. The produced power is usually then transformed by [[solar inverter]]s. Inverters are divided into three different types: central, module-integrated, and string. Central converters can be connected either in parallel or in series on the DC side of the system. For photovoltaic "farms", a single central converter is used for the entire system. Module-integrated converters are connected in series on either the DC or AC side. Normally several modules are used within a photovoltaic system, since the system requires these converters on both DC and AC terminals. A string converter is used in a system that utilizes photovoltaic cells that are facing different directions. It is used to convert the power generated to each string, or line, in which the photovoltaic cells are interacting.<ref name=Carrasco_Smart_Grid />

Power electronics can be used to help utilities adapt to the rapid increase in distributed residential/commercial [[solar power]] generation. Germany and parts of Hawaii, California, and New Jersey require costly studies to be conducted before approving new solar installations. Relatively small-scale ground- or pole-mounted devices create the potential for a distributed control infrastructure to monitor and manage the flow of power. Traditional electromechanical systems, such as [[capacitor bank]]s or [[voltage regulator]]s at [[Electrical substation|substations]], can take minutes to adjust voltage and can be distant from the solar installations where the problems originate. If voltage on a neighborhood circuit goes too high, it can endanger utility crews and cause damage to both utility and customer equipment. Further, a grid fault causes photovoltaic generators to shut down immediately, spiking the demand for grid power. Smart grid-based regulators are more controllable than far more numerous consumer devices.<ref name=tr1401>{{cite web|first=Martin |last=LaMonica |url=https://www.technologyreview.com/2014/01/21/174504/power-electronics-smooth-solar-transition/ |title=Power Electronics Could Help Grid and Solar Power Get Along &#124; MIT Technology Review |publisher=Technologyreview.com |date= 2014-01-21|access-date=2014-01-22}}</ref>

In another approach, a group of 16 western utilities called the Western Electric Industry Leaders called for the mandatory use of "smart inverters." These devices convert DC to household AC and can also help with power quality. Such devices could eliminate the need for expensive utility equipment upgrades at a much lower total cost.<ref name=tr1401 />