Powering Up: Exploring The Frontiers Of Power Electronics Innovation

By John Oncea, Editor

Power electronics drives efficient energy conversion, from small-scale devices to grid integration and aerospace applications, evolving with new semiconductor technologies.

Imagine it’s 1902. You’re hanging out with American engineer and inventor Peter Cooper Hewitt who, a year earlier, invented and patented a mercury-vapor lamp that served as the forerunner of the fluorescent lamp.

Hewitt’s lamp utilized mercury vapor produced by passing current through liquid mercury and, initially, had to be started by tilting the tube to make contact between the two electrodes and the liquid mercury. Later, he developed an inductive electrical ballast to start the tube which emitted light of a bluish-green color, limiting its practical use despite an efficiency much higher than that of incandescent lamps.

However, these lamps were useful for specific professional areas like photography where color wasn’t critical due to black-and-white films. In 1903, Hewitt improved the lamp’s color qualities, leading to widespread industrial adoption.

In between these two events, in 1902, Hewitt created the mercury arc rectifier, a groundbreaking invention that could convert alternating current (AC) power to direct current (DC) without mechanical means. Hewitt’s rectifiers were used to provide power for industrial motors, electric railways, streetcars, and electric locomotives, as well as for radio transmitters and high-voltage direct current (HVDC) power transmission.

Hewitt’s work also laid the foundation for modern power electronics, a critical discipline within electrical engineering that orchestrates the efficient management and conversion of electrical power and serves as the backbone for a myriad of modern technological applications.

Peter’s personal life was as interesting as his professional life, starting with the fact that through his marriage to Lucy Bond Work, he was an uncle of Maurice Roche, 4th Baron Fermoy who was the maternal grandfather of Diana, Princess of Wales. Peter had an affair with Marion Andrews while married to Lucy which resulted in the birth of Ann Hewitt. Peter and Marion later married, and he formally adopted Ann. After Peter’s death, he left two-thirds of his estate to Ann and one-third to Marion with the caveat that Ann’s portion would revert to Marion if Ann died childless. Just before Ann was to gain legal majority by turning 21 in 1935, she was hospitalized for appendicitis. Marion bribed the surgeons who were operating on Ann, telling them her daughter was “feeble-minded” and then bribing them to sterilize her during the appendectomy. Ann filed criminal and civil lawsuits in San Francisco after realizing what her physicians and her mother had done. The criminal case was ultimately unsuccessful, since at the time, involuntary sterilization of the "feeble-minded" was legal in California. Ann settled the civil suit for $150,000 after a lengthy trial that saw the charges against the doctors and her mother dropped.

Power Electronics 101

According to North Carolina State University, “Power electronics is the technology associated with the efficient conversion, control, and conditioning of electric power by static means from its available input form into the desired electrical output form.

Power electronic converters are commonly used wherever there is a need to change the electrical energy form, such as by modifying its voltage, current, or frequency. While regular electronics use electrical currents and voltage to carry information, power electronics use them to carry power. These systems are used in various devices, including DC/DC converters found in mobile devices like cell phones or PDAs, and AC/DC converters in computers and televisions.

Large-scale power electronics are also used to control the power flow of hundreds of megawatts across the nation, and researchers are exploring opportunities such as applications to control large-scale power transmission and distribution, as well as the integration of distributed and renewable energy sources into the grid.

It would be easier to list applications that don’t include power electronics as the technology has penetrated almost every field that uses electrical energy, writes Electrical4U.

“If we look around ourselves, we can find a whole lot of power electronics applications such as a fan regulator, light dimmer, air-conditioning, induction cooking, emergency lights, personal computers, vacuum cleaners, UPS (uninterrupted power system), battery charges, etc.,” writes Electical4U. “A modern car itself has so many components where power electronic is used such as ignition switch, windshield wiper control, adaptive front lighting, interior lighting, electric power steering and so on. Besides power electronics are extensively used in modern traction systems and ships.”

It doesn’t stop there. In industry, almost all of the motors used are controlled by power electronic drives, from rolling mills to textile mills, compressors to pumps, fans to blowers, and many more. Other applications include welding, arc furnaces, cranes, heating applications, emergency power systems, construction machinery, and excavators.

• Defense and Aerospace: Power supplies in aircraft, satellites, space shuttles, advance control in missiles, unmanned vehicles, and other defense equipment.
• Renewable Energy: Generation systems such as solar and wind need power conditioning systems, storage systems, and conversion systems to become usable. For example, solar cells generate DC power and for general applications, we need AC power hence power electronic converter is used.
• Utility System: HVDC transmission, VAR compensation (SVC), static circuit breakers, generator excitation systems, FACTS, smart grids, etc.

Modern-Day Power Electronics

“The modern solid-state power electronics revolution started with the invention of the PNPN transistor (thyristor) in 1956 by Bell Laboratories,” writes IEEE. “GE introduced the thyristor (SCR) to the commercial market in 1958.”

Other power devices have been developed since, starting with the phase-controlled thyristor. GE invented the antiparallel thyristor (TRIAC) in 1958 for AC power control. In the same year, GE also invented the gate turn-off thyristor (GTO). The market saw the emergence of power MOSFETs and bipolar junction transistors (BJTs) in the late 1970s. High-power GTOs were introduced by Japan in the 1980s.

“Nowadays, the power MOSFETs have become universally popular for low-power high-frequency applications,” writes IEEE. “The insulated-gate bipolar transistor (IGBT) was invented in 1983 by GE-CRD under the leadership of Jayant Baliga. Today, IGBT is the most important device for medium-to-high power applications.

The high-power, integrated gate-commutated thyristor (IGCT) was introduced by ABB in 1997. Large-bandgap materials, such as SiC and GaN are showing great promise. SiC devices, such as the Schottky barrier diode (1200 V/50 A), the power MOSFET (1200-V/100), and IGBT (1200 V/100 A) are already there in the market.”

IGBT and MOSFET are two of the most commonly used power semiconductor devices for switching applications. Nowadays, wideband gap devices such as SiC and GaN are becoming more popular due to their advantages over conventional semiconductors. These advantages include high blocking voltage, high operating frequencies, and the ability to operate at high temperatures.

 

Researchers have proposed many improvements in the topologies of both isolated and non-isolated DC-DC converters to enhance their efficiency and reduce ripples. While conventional topologies are still primarily used for DC-DC converters and multilevel converters, researchers are suggesting many hybrid and derived topologies of conventional multilevel inverters. However, their commercialization has been limited. PWM rectifiers are used when power factor improvement and bidirectional operation are desired. Matrix converters and active front-end voltage source converters are commonly used for AC-AC conversion applications.

“Sinusoidal PWM technique has continued to be the most preferred PWM technique because of its simplicity, IEEE writes. “In addition to the classical PWM techniques such as sinusoidal PWM, selective harmonic elimination PWM, space vector PWM, etc., many advanced PWM techniques are also being suggested.”

The Future Of Power Electronics

Markets and requirements are constantly changing, meaning trends must be closely monitored, notes Knowles Precision Devices. “One area where we are seeing rapid innovation spanning the industries we serve is power electronics. At a high level, the trends driving power electronics innovation are largely centered around methods for providing more energy more efficiently while using smaller components.”

Knowles goes on to list four trends they are monitoring, as well as how to stay on top of each of them with your designs.

• Increasing investment in renewable energy technologies: As with any evolving industry segment, the demands on today’s components won’t be the same as what will be required down the road. Therefore, as this industry grows and innovates, the vast amount of vital power electronics used as the building blocks for these renewable energy technologies must experience innovation as well.
• Continued electric vehicle innovation: There is a trend to focus on making EVs lighter and improving gravimetric density, which means every component used in a vehicle down to the board level must be heavily scrutinized when it comes to their size, weight, and power (SWaP).
• Growing demand for UAVs: Since every gram counts in a drone, the size and weight of even the smallest component must be heavily scrutinized. But, because of the mission-critical nature of many UAVs, reliability cannot go by the wayside.
• Improving power electronics efficiency with wide-bandgap semiconductors: As the power electronics systems used in a wide variety of applications require operations at higher voltages and wider temperature ranges, new circuit design trends are emerging to meet these demands. The latest trend we are seeing is for electrical engineers to shift from using conventional silicon-based (Si) semiconductors to using wide-bandgap semiconductors built with silicon carbide (SiC) or gallium nitride (GaN).