Do Solaredge optimizers limit pv vdc

[solar daze]

Hello All and thank you in advance for any input on this discussion. Also I apologize for the long explanation
So I stared with a solar city system and it consisted of the following:
Total system kw=17.68kw
2-se7600 solaredge inverters
68-REC260/260 watt panels
VOC=47.8
solaredge optimizers
3-18 panel strings
1-14 panel string
2-18 strings in parallel in one inverter
1- 14 string and 1-18 string wired in parallel in the other inverter.
The highest voltage I ever saw was 346 vdc
Hopefully that is enough background for now.
I replaced the solaredge inverters with the eg4 18kpv. I was misinformed that the existing solaredge optimizers were compatible. Turns out they were just kidding, so now I have replaced all of the SE optimizers with the Tigo optimizers. Now my eg4 18kpv went into a fault due to over voltage on the DC input. Now I am reading over 600 vdc on the 18 module strings. An anyone shed some light on how/why this occurred? Do the solaredge optimizers limit the voltage dc coming from the pv arrays? Aside from reconfiguring my entire system does anyone have any idea what is going on?
P.S. the maximum mppt for the solaredge inverters is also 500vdc.

 

[solar daze]

VOC =37.8, my phone fat fingered the wrong VOC

 

[pvgirl]

The solar edge optimizers do MPPT per panel, and they do regulate the string voltage in cooperation with the inverter to a fixed voltage. The voltage and current on a solar edge string are independent of the panels voltage. Without the solar edge optimizers regulating the voltage, your strings now have to be designed to limits of the 18kv, which unfortunately means reconfiguring your panel wiring in shorted strings.

Depending on the panels are laid out, what direction they are facing, the coldest temperature at your location, and the exact model/specifications of your panel, will determine how to rewire your strings.

 

[400bird]

Solar Edge optimizers work differently than Tigo Optimizers.
Solar Edge optimizers are full MPPTs and buck/boost DCDC converters. There are minimums and maximums. But communication between the inverter and optimizers mean the inverter/optimizers set and hold a specific string voltage that is unrelated to PV output and is just the most efficient point for the inverter, mine normally holds about 380 VDC from memory.
This is why they could parallel a 18s and 14s string without production loss.

Tigo optimizers are significantly less sophisticated and just buck the voltage down to increase current (on a single panel) if you've got an underperforming (shaded) panel. They also have a limit somewhere around 25%

In short, yes.

On a standard string inverter, you've got to do the math and make sure you don't exceed the PV input voltage.

 

[solar daze]

Thank you so much for your kindness in clearing this up for me . I have already done the calculations for the new string configuration. If I'd been given the correct information prior to buying the new equipment I would have done ac coupling instead. But in the end it will be worth it...I think. Again thank you so much!

 

[solar daze]

My forum name should have been "solar dazed and confused". Thank you for your fast response!

 

[Oldphile]

Good luck with rewiring your strings. Last week I went through a similar scenario. The installer was accustomed to SolarEdge and wired 12 Panasonic 400 watt panels in series on my Sol-Ark. Measured 545 volts on MPPT input.

 

[Zapper77]

Thank you so much for your kindness in clearing this up for me . I have already done the calculations for the new string configuration. If I'd been given the correct information prior to buying the new equipment I would have done ac coupling instead. But in the end it will be worth it...I think. Again thank you so much!

Yea, AC couple would have been the cheapest. Switching to tigo will save wall space.

I've noticed that my tigo optimizers keep the voltage constant.

Orange Voltage
Pink Amperage

 

[solar daze]

Yea, AC couple would have been the cheapest. Switching to tigo will save wall space.

I've noticed that my tigo optimizers keep the voltage constant.

Orange Voltage
Pink Amperage

View attachment 175146View attachment 175147View attachment 175148

Yes ,it saved lots of wall space for sure! I still think it it will make a much cleaner job. Also I'm not how the grid tie inverters would have handled a loss of utility power. With no grid input the SE would prevent solar production. I still have to tie in my cca and TAP today. Looks like you have a nice system. I'll post pics when it's complete.

 

[solar daze]

Good luck with rewiring your strings. Last week I went through a similar scenario. The installer was accustomed to SolarEdge and wired 12 Panasonic 400 watt panels in series on my Sol-Ark. Measured 545 volts on MPPT input.

Oh my! How did that work out for you? Is that something you did yourself? I should have known better, but things were happening so fast it got away from me.

 

[Oldphile]

Oh my! How did that work out for you? Is that something you did yourself? I should have known better, but things were happening so fast it got away from me.

Installer was on site trouble shooting the string that wasn't producing. When I realized he had 12 panels in series, I pulled up the manual and explained the voltage would be too high. After he understood, he called the office and had a crew come out with a Y cable. 12 in series became two strings of 6 in parallel. Lucky the MPPT wasn't blown. The mistake was made by their engineering department. This was their first Sol-Ark and TIGO. Also lots of problems setting up TIGO.

Now my TIGO map only shows 2 strings instead of 3. I think the modules are physically mapped correctly, but string assignment is meaningless. I think I would have to reconfigure the layout, assign serial numbers and do discovery again. I'm reluctant to do this incase it fails discovery. I dare not screw this up before inspection and PTO.

 

[solar daze]

I am not a fan of Y cables. I feel more comfortable pulling my strings into a combiner box. Maybe they are fine, I've never used them.
However you do make a good point, I hope I didn't blow out my mppts. I would hope that they thought to incorporate some sort of over voltage protection! I'll know later today. Sol-Ark is a great product for sure, I hope all is well for you.

 

[400bird]

I've noticed that my tigo optimizers keep the voltage constant.

To clarify what I said about the two optimizer types. Tigo doesn't do anything with the output voltage (that is left to the MPPT in the string inverter) while Solar Edge activity adjusts the string voltage at the optimizers.

 

[Zapper77]

To clarify what I said about the two optimizer types. Tigo doesn't do anything with the output voltage (that is left to the MPPT in the string inverter) while Solar Edge activity adjusts the string voltage at the optimizers.

Yea my wording was also off.