Maybe the best news for continued green energy

[thermionic1]

I had mentioned the very serious issues that have been occurring on the grid due to Inverter Based Resources (Solar and Wind) tripping offline at the worst possible moments, such as after a fault in another generating station. NERC had issued some strongly worded guidelines about fixing the problem.

As an example, our power gen division is aware of the "Odessa Incident" as they are constructing a 500MW solar installation. They can't find out if the inverters are going to have a problem or not because the IBR OEM won't talk to them directly, or to the developer. The developer could care less and is only interested in building the plant and moving on.

Now, it seems NERC is requiring a database of registered plants. Much more is needed, such as better event and fault records from each inverter.

We use state of the art protection systems on the lines that connect to the IBR plants, but often these relays can't operate as designed because the IBR's don't behave like a synchronous machine and can no longer reliably determine if a fault is in front or behind the relay. The new FERC order will also require transparency of the IBR's so better modeling can be performed.

FERC Reliability Standards

 

[TugboatEng]

High voltage DC transmission uses inverters at the receiving end. How do they manage these complications? HVDC is a well established technology with a proven record of reliability. Or, are there additional complications at the generation end?

 

[thermionic1]

The one HVDC station in our territory had some issues after installation. Surrounding distribution systems that used a power line carrier communications system for residential billing started going haywire. There were several investigations and IIRC, nothing definitive could be proved. The HVDC owner paid to have the PLC systems modified and that seemed to resolve the issue.

These inverters are quite different than those found in solar installations, starting with the HV Valve hall and the very sophisticated protection and control.

I was discussing this issue with some of our powergen folks. They are currently about to purchase a mid sized (200MW) solar plus battery (100MW) site, once developed. They can't get any information from the inverter OEM's on this issue (Odessa). The OEM will only talk to the developer. The developer is either not asking the correct questions or is simply ignoring any questions from the future owner.

Nobody wants to discuss the frequency / inertia issue. IBR's theoretically can act much faster in the frequency support area, but those batteries have to be charged to be of any help.

A few years ago, I was asked to implement a active power curtailment scheme on a small rooftop solar installation. Simply figuring out how to communicate with the inverters was a chore. All of the Modbus registers listed in the manual were obsolete. The entire data map had been reconfigured to some solar industry standard. In the OEM data map, each register name / function was clearly defined. In the new spec, not so much. A year later and I'm asked to remove that control and add a dynamic volt/var scheme. The original OEM sold these line of inverters to another company. This company had no idea what they had and couldn't offer support for the inverter functions that it clearly had. Developer onto the next project and the owner left holding the stick.

I hear that some IBR plants are having dry type voltage transformers fail at an alarming rate. "High Frequency Spikes" is what is being blamed. OK, so now what?

I have a friend that works for a solar developer. I sent him the FERC announcement. He stated it was good to know when the truck was coming. I responded it wasn't a truck, but a freight train.

I say this FERC order is good news because it will force the industry to actually do something about the problem. NERC has issued 3 strongly worded memos about this in the last 3 years and nothing has changed. Having large solar farms dump off line in response to other faults in the system is about the worst thing that can happen. If green energy is going to continue to grow, it has to behave and get along with the other generation sources and system disturbances.