Blog Highlights

  • The main challenges of inverter control design, development, testing, and certification.
  • How does a C-HIL setup look like for hybrid inverter controltesting.
  • How can test automation speed up inverter software updateverification.
  • How can HIL speed up product development while improving product robustness and quality.

Schneider Electric XW-Pro Solar Hybrid Inverter 120/240V.

Steven VanWerkhoven is the Director of Software Development at Schneider Electric. He runs all the teams for power electronics controls, firmware, and software development and lifecycle maintenance – in short, the teams that develop everything that goes inside of Schneider Electric’s hybrid residential inverters.

| What are the major challenges hybrid inverter manufacturers face when developing, testing, validating, and certifying inverters?

There’s a lot of challenges withhybridinverterdesign and testing, especially when these inverters are designed to be sold worldwide.We need to develop controlalgorithmsto handle different grid disturbancesinaccordancewithlocalgrid code requirements(e.g.UL 1741 SA, PREPA).So, testing, grid code compliance validation, and pre-certification take a huge amount of development time and cost.

We’re continually developing new and expanding existing features in the form of new control algorithms in our inverters. Since this is handled by a large team of software developers that work continuously, what we need is a system that can run a check every time we commit a code change. You don’t want to go through six months of work with untested software.

Earlier, testing our inverter controls used to involve testingwiththe realinverterin a power lab. This meant a long lead time for getting the actual inverter prototype and assembling it into the lab setup. As power converters today get more complicated, the cost and complexity of these lab setups go up exponentially. Additionally, operating power lab equipment and running tests takes a lot of manpowerandtime;we would be able to run only 5 to 10 testsper dayat maximum.We hada big need for a robust and extensiveHILtesting frameworkthat would speed up control software testing andreducetime-to-market.

HIL Testing | How does your HIL setup look like and what do you test with it?

Typhoon HIL is the core of our Controller-Hardware-In-The-Loop (C-HIL) platform – for example,the AC grid is simulated inside of it. Because we have full control over the AC grid model, we can simulate any disturbance we want, e.g. Low Voltage Ride-Through (LVRT) or anti-islanding events. And we can take the actually measured voltage waveforms from the field and run them in Typhoon HIL, so we can see how the inverter responds to those exact voltage waveforms. And that really dramatically decreases troubleshooting time. If you were trying to do that in the power lab, it would be very complicated and costly.

In the beginning, the main questions were: how accurate are the models, how much can you trust them, how useful are they? We had to answer those questions ourselves when we started using HIL. So, we did the same test cases in the lab and in HIL to validate the models. We found that they match really well, with less than 1% error for steady-state conditions and within 5% or less error during fast transition dynamic test cases.

Testing and pre-certification is where implementing Typhoon HIL’s Controller Hardware-in-the-Loop (C-HIL) test solutions helped us the most: we dramatically decreased our development and testing time through test automation and the wide array of tested scenarios enabled us to always step into certification with full confidence.

Steven VanWerkhoven
Director of Software Development
Schneider Electric

HIL Automation | How did you set up the automation procedures for testing inverter control software updates?

Withour Python test framework, we canuse Typhoon’s HIL APItotrigger a testsuitethrough Jenkins. All of the test cases thatwe’redeveloping automatically get added into our full regression test suite.Weprobablyrunthousands of test cases every weekend.Each Friday evening, the system gets automatically triggered. It takes the latest build from our software programs, puts it on the controller board, and runs all weekend through all sets of parameters – so we can observe the test results when we’re back on Monday morning.

However,after each new code iscommitted to the repository, wealsorunthe control softwarethrough a subset of operating conditions andcorner cases – we callthata “sanity test suite”.We also run a larger set of cases each night.What this ensures is that new features that are being developed are always testedas soon as possible.

HIL Benefits | How did implementing HIL improve your work and product reliability?

The advantage of having an automated HIL platform is that the system automatically performs quality tests for new features every day in real-time as the developers push code. Also, the HIL testing environment allows us to test the real code of our real controls compiled into the actual controller board from the very beginning. For us, this means we are ready to go into lab testing, certification, or software release at any time. For the customer, this is an assurance that their product will pass all of the test cases, as the latest software we are developing is always fully tested. Another advantage of HIL is that we can test basically any corner case with a coverage of thousands of test cases. We can simulate what we’ll see in the field where we can’t even do that in a lab. HIL Tested ensures that the products are reliable.

The HIL results were sufficient for certification in many cases as well. The certification body accepted the test results from our HIL platform because our whole platform had been verifiedand validated against laboratoryresultsandwe proved that the accuracy was well within tolerance.

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To learn more, watch
HIL Tested Schneider Solar Systems
Build A Better Microgrid Series Episode 2

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To find out how you could implement HIL Testing Automation in your own work, visit the TyphoonTest IDE webpage or contact us for a demousing the links below.



Text: Debora Santo, Sergio Costa, Ivan Celanovic
Visuals: Karl Mickei, Debora Santo
Disclaimer: The blog is based on the interview done for the Building a Better Microgrid Industry Spotlight video series with Schneider Electric by Typhoon HIL.