A Siemens Corporate Technology research department specializing in intelligent power electronics is develop-ing software-defined inverters. The new components are designed to enhance the performance of electronic systems and, more importantly, make such systems more flexible. Potential application areas range from robotics and electric vehicles to home energy storage systems.
by Hubertus Breuer
Inverters are needed for almost everything these days. Whether it’s charging stations for electric vehicles or electric drives for robots and drones – all of these systems require the use of power electronics if they’re to operate efficiently and precisely. That’s because inverters can adjust frequency and voltage as needed in just fractions of a second. “The increasing digitization of power supply systems and electrical devices and the advent of the Internet of Things are making power electronics more and more important,” says Andreas Gröger from Siemens Corporate Technology in Erlangen. “With this development, we at Siemens are in tune with the times.”
Great leaps have been made with power electronics over the past 20 years. Today’s inverters can adjust frequency and voltage extremely rapidly. They boast very low distortion and are equipped with innovative materials that ensure efficient heat dissipation. What’s more, their compact design makes for impressive space-saving properties. These attributes are, for example, opening up new possibilities for more flexible use of robots and the development of tomorrow’s distributed power systems.
With all of this in mind, in 2016 Siemens established a new research department for power electronics and software-defined inverters (SDIs). This department, which is now headed by Gröger, works with universities around the world, as well as with companies such as Texas Instruments, and other research partners. SDI experts were recruited from Siemens divisions such as the Digital Factory, Energy Management, and Process Industries and Drives, as well as from selected international universities and institutes that draw young, talented people. This recruitment approach reflects the diversity of the technological challenges involved, as well as the wide range of potential applications for SDIs. Agile working methods that include close cooperation with Siemens business units have enabled the SDI team, which now consists of more than 80 members, to target short innovation cycles for the development of marketable products.
Along with Internet of Things (IoT) capability, one of the most important innovations for the new generation of software-defined inverters involves the use of gallium nitride (GaN) as a semiconductor material, which enables the production of smaller and more efficient modules. Up until now, semiconductors have mainly been manufactured with silicon, as the material is robust and proven, and the technology for its use is advanced. Although GaN has a more limited performance range than silicon, it can operate at significantly higher frequencies while displaying lower conducting and switching loses. GaN is still more expensive than silicon, but its future prospects nevertheless look good. For example, manufacturing on a semiconductor wafer of the material needs less wafer area, which means GaN costs should drop below those of silicon over the long term.
Fast signal processors and special filter components are also helping experts get the most out of GaN, although software is playing the most important role here. The SDI team has developed a lean application platform known as CACTUS (“Control And Converter Technologies for Universal Systems”) that builds on the FreeRTOS cloud-based open-source system for the Internet of Things. CACTUS offers a simple way to network devices. More important, however, is the fact that when utilized in combination with high-performance GaN hardware, CACTUS makes it possible to adapt universal inverters for use with the most diverse types of applications. The cloud makes things easy. “Imagine loading CACTUS onto a temperature sensor,” says Gröger. “You can then use an online engineering platform to link the graphically displayed application for temperature measurement with the function that displays measurement data on a smartphone. Lego Mindstorms utilizes a similar principle, which we’re now implementing for power electronics systems.”
Siemens’ research department in Erlangen demonstrated the versatility of its software applications for the first time when it developed “Tapas” – the world’s first software-defined universal inverter. The 48V device is ten to 50 times more dynamic than comparable inverters and is also much smaller. This makes it particularly suitable for robotics applications, for example, which require a high degree of precision at high speeds. Other potential areas of application are even more extensive, of course, and include 3D printing and LED and laser technology.
Because the variety of application possibilities for Tapas is simply too extensive for Siemens to develop them all, the company launched its TAPAS Community Challenge
at the beginning of 2018. This platform allowed developers from all over Europe to compete against one another in order to come up with the best ideas for using Tapas. The competition, which was held until the end of July 2018, led to the development of promising systems, including a wireless battery-charging device, a module for building a local microgrid, and a magnetic control device for moving a drill in a catheter through the gastrointestinal tract. All of this made it possible to develop software aligned with the task at hand.
Naturally, research with Tapas continues. For example, in November 2018 at Electronica, the world’s leading trade fair for electronics, which is held in Munich, Siemens and Texas Instruments demonstrated an IoT-enabled 400V inverter known as “Gridlink” in which current flows in both directions. This setup is ideal for charging stations that supply vehicles with electricity from the grid and also feed electricity from vehicle batteries back into the grid. “We like working with partners on industrial applications,” says Gröger. “Like us, semiconductor manufacturers in particular are interested in finding out which types of applications can be developed with innovative inverter technologies, and our software and application expertise offers the perfect foundation for pursuing such an approach.”
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