SolarEdge Question...

[nwdiver]

From what I can tell the 'layout' screen shows the total optimizer power output on the inverter. I do like that I can contrast this number to AC output to get a rough idea of system efficiency to ensure there are no loose connection waiting to cause a problem. Can anyone tell me what I should see for typical system losses? I have a 11.4kW HD Wave that is showing a ~2.7% difference between optimizer output and inverter AC output. Is the the ballpark of normal? Thank you.

[Ampster]

That is normal for one of my systems. I have a 4.3 kW system with 5.0 kWSolaredge inverter. If I chart power of the string vs the inverter I get 93.7%. I used several points along the sine wave and not much difference between early in the day and mid day. My other system is a 5.7kW sysem with a 3.8kW inverter but I can't chart that because it is on the installer site with more limited capabilities.

[nwdiver]

That is normal for one of my systems. I have a 4.3 kW system with 5.0 kWSolaredge inverter. If I chart power of the string vs the inverter I get 93.7%. I used several points along the sine wave and not much difference between early in the day and mid day. My other system is a 5.7kW sysem with a 3.8kW inverter but I can't chart that because it is on the installer site with more limited capabilities.

Awesome. Thank you.

Do you know what the basis is for the power limit on Solar Edge strings? I had been under the assumption that it would simply cap the current at 15A and any additional power would simply be clipped but it looks like Solar Edge doesn't want >6000w STC in a string with a HD Wave inverter. I don't understand why.

[Ampster]

Awesome. Thank you.

Do you know what the basis is for the power limit on Solar Edge strings? I had been under the assumption that it would simply cap the current at 15A and any additional power would simply be clipped but it looks like Solar Edge doesn't want >6000w STC in a string with a HD Wave inverter. I don't understand why.

Serry I don't know that answer. My other system is 5.7 kW with a 3.8 kW inverter and I am curious whether the clipping is at the optimizers or at the inverter. That system is on an installer login and i don't have access to that level of detail.

[ButchDeal]

Serry I don't know that answer. My other system is 5.7 kW with a 3.8 kW inverter and I am curious whether the clipping is at the optimizers or at the inverter. That system is on an installer login and i don't have access to that level of detail.

What do you mean by on an installer login? Installers would have full access. if they haven't given you access then call them and get them to grant you owner access.

The clipping happens at both. The inverter is limited but the optimizers will start shifting the voltage off of MPPT to limit power as the inverter start clipping.

[ButchDeal]

Awesome. Thank you.

Do you know what the basis is for the power limit on Solar Edge strings? I had been under the assumption that it would simply cap the current at 15A and any additional power would simply be clipped but it looks like Solar Edge doesn't want >6000w STC in a string with a HD Wave inverter. I don't understand why.

It will void the warranty to put more power on a string. This is to insure that the optimizers are able to control the power and are appropriately sized to limit current.

The limit is actually 5.7kW per string for HDWave inverters 6kW and under and 6kW for SE7600H and up.
You also have min and max string length as well.

https://www.solaredge.com/sites/default/files/se-P5-series-add-on-power-optimizer-datasheet-na.pdf

[nwdiver]

This is to insure that the optimizers are able to control the power and are appropriately sized to limit current.

That's where I was a little confused. Because STC can be exceeded under certain conditions. Low temps combined with 'edge of cloud effect' can easily make a 300w panel a 400w panel. Most electronics handle this by simply raising voltage which is why the Voc limit is based on the coldest temperatures expected and the actual current limit is typically 120% of the Isc rating. The string should be able to limit current to 15A regardless of the combined STC of the panels so long as the panels don't exceed the voltage input rating of the optimizers.

[ButchDeal]

That's where I was a little confused. Because STC can be exceeded under certain conditions. Low temps combined with 'edge of cloud effect' can easily make a 300w panel a 400w panel. Most electronics handle this by simply raising voltage which is why the Voc limit is based on the coldest temperatures expected and the actual current limit is typically 120% of the Isc rating. The string should be able to limit current to 15A regardless of the combined STC of the panels so long as the panels don't exceed the voltage input rating of the optimizers.

With all electronics there are test conditions that they validate for. With these in particular there are very stringent limits that they test for and have approval for since solaredge has received special disposition to allow three strings without fuses etc. the optimizers have buck/boost output voltage regulation, as well as inout MPPT. Trying to push outside of those limits is pointlessly voiding a warranty with zero benefit since you can just have another string. Further I have seen strings that are outside of spec with too many watts, and they do NOT behave well. The code is designed for some conditions, going outside of that produces poor results.

[nwdiver]

With all electronics there are test conditions that they validate for. With these in particular there are very stringent limits that they test for and have approval for since solaredge has received special disposition to allow three strings without fuses etc. the optimizers have buck/boost output voltage regulation, as well as inout MPPT. Trying to push outside of those limits is pointlessly voiding a warranty with zero benefit since you can just have another string. Further I have seen strings that are outside of spec with too many watts, and they do NOT behave well. The code is designed for some conditions, going outside of that produces poor results.

Thank you; I'm just trying to understand the operation since this is something I'm not familiar with. My initial impression was that if you had for example a string with E/W panels you could have 4kW facing W and 4kW facing E and rarely if ever suffer from clipping but it appears even this would be unacceptable since 8 > 6....

[ButchDeal]

Thank you; I'm just trying to understand the operation since this is something I'm not familiar with. My initial impression was that if you had for example a string with E/W panels you could have 4kW facing W and 4kW facing E and rarely if ever suffer from clipping but it appears even this would be unacceptable since 8 > 6....

That is a perfectly acceptable layout you just wouldn't out it in one string. Two parallel strings would be fine.., why would you want it in one string? No reason at all.

[JSchnee21]

You just need to be sure that your two separate strings (E & W) each have sufficient panels to be above the minimum, per string. So at least 8 or 9 panels per string. The SE permissible DC to AC over subscription rate differs between the older A-Series (mostly discontinued) and the newer HD series. Higher over subscription is permitted for the HD series -- up to approx 1.5 or so (see spec sheet). Higher (>1.2x) over subscription rates can be smart for certain applications (e.g. East / West arrays), or in cases or heavy shading, or if a subset of the panels are sub-optimal for some reason -- North, inclination, shaded at a particular time of day, etc.. They do not make sense when all panels are of the same orientation and inclination (e.g South facing, inclination near latitude)

To ensure optimal performance and warranty coverage, strings need to of the correct length (more than min, less than max), strings need to be below the max wattage per string, and DC/AC ratio needs to be below the limit for inverter model. Of course you need to choose the correct optimizer for your panels / panel type as well.

One other minor point, the Wattage rating on the HD series is the max. Aka what you see is what you get (under optimal conditions -- which are rare). For the older A-series, some models, not all (mostly larger inverters) would tolerate short duration of output above the name plate. For example, my 11.2kW actually maxes out at 11.8 or so (12kW according to the firmware setting). Similarly the older 7.6kW A-series supported up to 8kW, where as the newer 7.6kW HD clips hard at 7.6kW.

Separate from the inverter, it is very rare for panels to output at STC levels, and when they do, they rarely exceed STC levels by more than 20-30% and then only for a few seconds / minutes. So on cold sunny days, with cloud edges, my 330W panels might briefly hit 360-390W for a few seconds at most when the sun first peeks around a cloud. This is nothing to be concerned about, the Optimizers will increase their DC voltage as the inverter "pushes back" and starts to clip for a few seconds/minutes.

[ButchDeal]

You just need to be sure that your two separate strings (E & W) each have sufficient panels to be above the minimum, per string. So at least 8 or 9 panels per string.

minimum string length varies with optimizers: 8 for most but the P405 & P505 is min of 6.

https://www.solaredge.com/sites/default/files/se-P5-series-add-on-power-optimizer-datasheet-na.pdf

The SE permissible DC to AC over subscription rate differs between the older A-Series (mostly discontinued) and the newer HD series. Higher over subscription is permitted for the HD series -- up to approx 1.5 or so (see spec sheet). Higher (>1.2x) over subscription rates can be smart for certain applications (e.g. East / West arrays), or in cases or heavy shading, or if a subset of the panels are sub-optimal for some reason -- North, inclination, shaded at a particular time of day, etc.. They do not make sense when all panels are of the same orientation and inclination (e.g South facing, inclination near latitude)

OP is talking about HDWave which is the newer versions.
Over subscription is NOT for strings though.