Real-Time Simulation and Testing
Power electronics is essential to a broad range of modern applications, from electric vehicles and aerospace to industrial machines and renewable energy generation. In each of these, power electronics technology is relied on to control the voltage, current, and frequency of electrical power or to convert it between alternating and direct current.
The development, testing, and validation of power electronics solutions is challenging. Modern power electronic systems operate at high switching frequencies and many components introduce non-linearities into the system. Moreover, the proper operation of the system depends on the interaction between the electrical circuit and the controls (and other physical domains, such as the mechanical domain), so the system must be designed as a whole.
Based in Zurich, Switzerland, Plexim has made it its mission to provide electrical engineers with reliable tools to address the challenges they face in the conceptual design, realization, and verification of such complex power electronics systems. Since its first release in 2002, Plexim’s PLECS circuit simulator has established itself as the de facto standard for modeling and simulating complex electrical systems in academia and the industry.
Plexim also offers a compact, powerful device for hardware-in-the-loop and rapid control prototyping applications. With the RT Boxes (RT Box CE, RT Box 1, RT Box 2, and RT Box 3), power electronics engineers can easily convert offline models, designed using the PLECS circuit simulator, into online real-time simulations, complete with analog and digital I/Os. The RT Boxes run on Enclustra SoM (System-on-Module) modules, featuring multiple standard CPU cores alongside a field-programmable gate array (FPGA).
The main challenge Plexim faced when developing the RT Boxes was to provide sufficient performance for the simulations to run in real time. In the case of hardware-in-the-loop testing, in which power electronics controllers are connected to a real-time simulation of the system in which they will be deployed for testing, the RT Boxes had to capture PWM signals with a time resolution of around 7 ns. From the start, it was clear that meeting low latency requirements for the I/Os and achieving microseconds cycle times would require tight integration between an FPGA and standard CPUs.
The engineers at Plexim wanted to focus on those aspects of the development process where they could add the most value, namely, in developing the peripheral electronics. Rather than reinventing the wheel and designing the onboard FPGA themselves, they began looking for commercially available modules combining an FPGA with standard CPUs as well as all the peripherals they needed to reduce their time to market.
At Enclustra, they found the performance they needed for their first product, the RT Box 1, in Enclustra’s Mercury ZX5 SoM(System-on-Module). In addition to the convenience of being located in the same neighborhood, Enclustra’s offering included modules capable of providing a sufficient number of ultra-low-latency I/Os and that are powerful enough to achieve microsecond cycle times, all in a compact format. Featuring a AMD Xilinx® Zynq® 7015/7030 SoC device, the Mercury ZX5 used in the RT Box 1 comes with an ARM® dual-core Cortex™-A9 processor and AMD Xilinx Artix™-7/Kintex®-7 28nm FPGA fabric.
Plexim further developed the RT Box 2 and the RT Box 3 for customers with more challenging applications. For these editions, they selected Enclustra’s Mercury+ XU1 SoM (System-on-module). Built around AMD Xilinx’s Zynq Ultrascale+ MPSoC, the Mercury+ XU1 features an ARM® dual-/quad-core Cortex™-A53 processor and 16nm FinFET+ FPGA fabric. The Mercury+ XU1 module offers increased performance, allowing the RT Box 3 providing users with twice as many I/Os than the RT Box 2.
By working with Enclustra, Plexim was able to speed up the development of their products while meeting the demanding performance required by their solution. Everything was wired out of the box: there was no need to worry about connecting the RAM to the FPGA, the NAND flash was already there, and it came with a PHY for ethernet communication. Therefore, working with the Enclustra SoMs allowed the team at Plexim to jumpstart the development of their product and focus on their core business.
“Enclustra’s SoM solutions deliver the right amount of peripherals for our applications, and are equipped with the type of SoCs that fit our needs,” says Jost Allmeling, CEO of Plexim. “By sourcing the SoMs from Enclustra, we were able to cut the time to market of our solution by around a year. Not only that, we also essentially outsource the sourcing problem, which, in an era of 72-week lead times, is a big advantage.”
Enclustra |Plexim |power electronics| Mercury ZX5 | Mercury+ XU1 |ultra-low-latency I/Os |PLECS circuit simulator | RT Box