PMU type measurement units based on the GPIC

[Bhat_Maanay_Rice]

I am working on a project where I am required to build a PMU type measurement unit out of rather cheap and readily available hardware components and I want to explore the possibility of using the GPIC for this purpose.

Has anyone tried to reprogram the GPIC to operate as a Phasor Measurement Unit?

I noticed that NI has example programs for synchrophasors based on NI 9076 with GPS, Current sensor, Voltage Sensor and GPIO modules. The probIem is that these set of hardware are much more expensive than a GPIC. I believe that the codes can be reconfigured to work on the FPGA on the GPIC where the Simulatenous AI can be used as both current and voltage sensor. The problem would be to integrate a GPS to the GPIC.

Is there any tried-and-tested method to have the GPIC interface with a GPS module (say NI-9467) so that the measurements are synchronised to the UTC time with accurate time tagging.

Also I am interested on using the system clock as the timetag source and am curious about the accuracy that can be acheived.

Any kind of help and guidance on this project would be highly appreciated.

[Bhat_Maanay_Rice]

So no one has any opinion on this?

[BMac]

Hi Athapa,

Thanks for reviving this thread. I was planning to reply but was travelling and lost track.

It's a great thought and in general, one of the ways in which the GPIC reduces the total bill of material cost in an inverter by replacing/eliminating other subsystem boards and taking on their functionality. (It's actually cost effective on it's own for pure control and I/O in 50 kVA and higher systems, but also often replaces other subsystem boards like data loggers, local HMI controllers, and network interface links.)

There are design teams working on combined power electronics and phasor measurement unit applications. The cRIO-9068 chassis is typically the hardware target in most cases, due to the availability of C Series modules with 24-bit Delta-Sigma analog to digital converters as required to meet the accuracy requirements for a certified PMU per C37.118:2005 or power quality analyzer per 61000-4-30. The CompactRIO based PMU system is typically orders of magnitude less expensive than traditional black box PMUs, and NI provides a complete set of IP and development tools that enable it to be customized at the low levels. Also, the PMU measurement quality is absolutely top notch-- perhaps even best in class. Because the toolkit IP library source code is open, development teams have also used it as the starting point to build other things like custom switched mode power gear, custom protection relays, etc.

Also keep in mind that there are lots of power electronics control applications deployed commercially using CompactRIO rather than the sbRIO GPIC. Having a pre-certified, rugged metal enclosed system can be appealing for many applications. The metal housing of CompactRIO and all the associated certification testing and ratings eliminates a lot of mechanical and EMC engineering expense. We normally encourage our customers to pick the mechanical form factor that's best for the application, and if the volumes are high enough we can find a way to make the price point work.

Going back to the PMU discussion- The NI power measurement suite software libraries can certainly be executed on the sbRIO GPIC. The question is whether your application needs to meet the accuracy requirements of a certified PMU? If you need PMU functionality without the certification, then the GPIC could work. However, if you need the full accuracy of a certified PMU, then you will want to use the standard C Series modules and the default software that's been through the certification testing process.

Regarding GPS, the LVTTL lines on the GPIC are typically used to receive the GPS PPS or IRIG-B information. You won't be able to use the C Series GPS module but there are other commercial units that provide the required signals.

You might also be interested in the LabVIEW FPGA timekeeper IP, which is used to synchronize multiple FPGAs and provide a common time register. This is of interest for microgrid applications where tight synchronization is desirable.

https://decibel.ni.com/content/projects/ni-timesync-fpga-timekeeper

Regards,

BMAC