DIY frequency shifting solution for hybrid/grid-tie solar energy system?

[godawgs]

I'm trying to find the best solution for limiting my grid-tied energy system when my hybrid system batteries become full in an off-grid mode. I currently have an 18kW grid-tied system (2X Solaredge inverters) and a 4kW hybrid system (MPP Solar) with 48V batteries. The Solaredge inverters support power reduction through phase shifting. In an off-grid situation, I'd like to know if anyone has a solution for reducing, then turning off, the grid-tied system(s) when the batteries reach a certain threshold. I know it can be done with a DIY DC relay + high voltage AC relay, but it seems a little clunky. I also believe that there are hybrid system vendors that have phase shifting built-in (Victron, etc.), and would swap out the MPP Solar inverter if necessary, but I'm trying to salvage the current setup, if possible.

I believe the Victron Multi-plus II can perform phase-shifting. Are there any other vendors with products that do this?

Appreciate all your help.

Thanks!

 

[BentleyJ]

Check out Schneider Conext XW Pro, Outback Skybox or Mojave system, Sol-Ark.

 

[Ampster]

I'm trying to find the best solution for limiting my grid-tied energy system when my hybrid system batteries become full in an off-grid mode. ...........

As mentioned above those hybrid inverters can do AC coupling. That may be what you are calling phase shifting but it is often called frequency Watt modulation. My Skybox is limited to about 7kW of GT inverters it can control and the SolArk 12k has a similar limit. I presume the MPP can not do AC coupling?

 

[godawgs]

Thanks all. Yes, frequency shifting is what I was talking about, not phase shifting, though I guess it's similar. I inadvertently mixed in an electromagnetic interference term with this topic. The SolArk 15kW system is what I will be going with. It can AC couple my Solaredge inverters while performing the frequency shifting to shut them down when the batteries are full.

 

[Ampster]

I haven't looked at the specs for the 15k. How much GT solar can it AC couple with? It may be dependent on installed battery capacity.

 

[SparkyJJO]

I bought an 8kW Outback Radian to do AC coupling for my 7.5kW array. Theycare stackable to cover larger arrays. They support AC coupling.

 

[Ampster]

Yes, frequency shifting is what I was talking about

Change the title of the thread or start a new one so that you attract relevant comments.

 

[Hedges]

Thanks all. Yes, frequency shifting is what I was talking about, not phase shifting, though I guess it's similar. I inadvertently mixed in an electromagnetic interference term with this topic. The SolArk 15kW system is what I will be going with. It can AC couple my Solaredge inverters while performing the frequency shifting to shut them down when the batteries are full.

SolArk manual:

https://www.sol-ark.com/wp-content/uploads/2022/04/15KOD-Manual-4-22-2022.pdf

All mention of frequency is regarding wider limits when input is generator.

Mentions AC coupling a few times.

"Smart Load ON Batt: The SOC at which the AC coupled inverter(s) are turned on when in off-grid mode 60%-80% recommended"

This suggests it won't ramp down AC input (e.g. through frequency shift) well enough to keep battery cell voltage from shooting up. If there is a load-dump situation, it would have to suck down that excess current suddenly.

"Maximum combined input (AC+DC) = 34.2kW 19.2kW AC + 15kW DC"

Previously I heard they recommended AC coupled PV be less than DC coupled. That would let AC coupled PV be disconnected (by relay to "Generator" port), and variable power from DC coupled PV plus on/off control of AC coupled could provide continuously variable zero to (AC + DC) PV power.

Maybe frequency-shift AC coupling is documented somewhere else.


DIY Learnings of SolArk for Make Benefit Glorious Photovoltaic Power

What I learned today about Sol-Arl 12k frequency shift.

I had a question for Sol-Ark today about how their AC frequency shift really works to ensure both my SolarEdge GTI and Sol-Ark were set up correctly. On the Smart Load tab where "High Frequency" is listed, if set at 62 Hz and you reach what you have set for "Smart Load Off battery the Sol-Ark...

diysolarforum.com

 

[Ampster]

Maximum combined input (AC+DC) = 34.2kW 19.2kW AC + 15kW DC"

My guess is that the AC coupled limit is 19.2kW but that may be pass through limit. I suggest that @godawgs research or call SolArk to confirm. Generally the AC coupling limit is based on the GT inverter capacity in AC not the DC capacity of the panels attached to that inverter. To be clear the DC referred to in the quote I presume is the capacity of the panels connected through the SolArk MPPT port.

 

[godawgs]

My guess is that the AC coupled limit is 19.2kW but that may be pass through limit. I suggest that @godawgs research or call SolArk to confirm. Generally the AC coupling limit is based on the GT inverter capacity in AC not the DC capacity of the panels attached to that inverter. To be clear the DC referred to in the quote I presume is the capacity of the panels connected through the SolArk MPPT port.

I spoke with SolArk. AC coupled limit is 19.2kW. Frequency shifting is largely digital 60.0-->62.0 in a few seconds and is initiated by battery SOC. As long as the GT inverter is capable, it will respond accordingly. DC coupled input is 15kW, which I will have about 12kWp separate from my Solaredge 18kWp . With the 200A pass-through, I will run the utility to the SolArk 15kW, then AC Out to my 200A breaker panel. This will allow all of my PV power to become exportable without any NEC 120% breaker requirements (which was actually becoming a hassle with my current setup). Lastly I will add 30kWh of LiPo server rack batteries to provide enough power when the grid goes out. It's infrequent, but when it does like it did last winter, it can cause a real mess (I live in TX). The 30kWh of battery will also be used for the energy shifting that I've been wanting to do.

 

[Ampster]

long as the GT inverter is capable, it will respond accordingly.

The key to the GT inverter is the spec. Most likely the SolarEdge will work. Whether it modulated or just turns on an off depends on whether it complies with the latest UL2741SA spec. Earlier models did no have the SA suffix and can only be in and off but it still works

 

[jberger]

Here's a video from Scott about using the 15K with AC coupled panels in addition to DC panels.
Just dropped yesterday and might be of some help.

 

[godawgs]

The key to the GT inverter is the spec. Most likely the SolarEdge will work. Whether it modulated or just turns on an off depends on whether it complies with the latest UL2741SA spec. Earlier models did no have the SA suffix and can only be in and off but it still works

Yes, Solaredge implemented firmware that applies to all of their US inverters (California rule 21), though they do have the option of not having frequency shifting as well. In the rule 21 mode, frequency shifting is specified according to a linear proportional power reduction as the frequency moves towards ~62.03hz (where it is 0 power production).