Voc > MPPT upper range "grey area" (EG4 18k PV)

[hybe022]

Hi. Image below is from an EG4 18k PV Datasheet.

I'm just curious, what happens to the tracker if you happen to fall in the 501V-599V grey area range?
do you just get less efficiency from the MPPT?
If so, does it apply to other brands as well?

Thanks.



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[timselectric]

Yes
And yes

 

[mciholas]

It may refuse to use the power above 500 volts. I'd ask EG4 about this.

Most efficient is Vmp of the string around 360 volts.

Mike C.

 

[Brucey]

Hi. Image below is from an EG4 18k PV Datasheet.

I'm just curious, what happens to the tracker if you happen to fall in the 501V-599V grey area range?
do you just get less efficiency from the MPPT?
If so, does it apply to other brands as well?

Thanks.
View attachment 282810


}

From how I read that if it's over 500V it won't be producing anything till it drops below that level. No damage but no output either. Basically you need to target a working voltage range of 250V to 500V for max performance.

My midnite hawkes bay 90A has a working range of 185V to 585V but they aren't a budget option.

 

[timselectric]

From how I read that if it's over 500V it won't be producing anything till it drops below that level. No damage but no output either. Basically you need to target a working voltage range of 250V to 500V for max performance.

My midnite hawkes bay 90A has a working range of 185V to 585V but they aren't a budget option.

It will still work in the upper range. Just less efficient dealing with the higher voltage.

 

[Brucey]

It will still work in the upper range. Just less efficient dealing with the higher voltage.

I read that as zero output below 140V and above 500V. But no magic smoke till 600V.

 

[timselectric]

I read that as zero output below 140V and above 500V. But no magic smoke till 600V.

Zero output, until above 100v (wake up voltage).

edit: Actually needs 140v for sustained output.

 

[RCinFLA]

On most HF hybrid inverters, the SCC is a switching boost power supply circuit.

There are two voltage limits that must not be exceeded.

The first limit is usually the hard limit imposed on the output voltage of the SCC boost converter. It's limit is related to the maximum internal high voltage DC bus of the inverter.

Second is PV input SCC switching devices must not be allowed to exceed their breakdown voltage rating. This can cause permanent failure of SCC converter. This is usually checked by inverter voltage checks before SCC starts up. Static (non-switching) condition before SCC boost converter is activated has a higher breakdown voltage then active running condition so initial measure before activation can help prevent SCC overvoltage damage.

At full illumination, Vmp is 0.81 to 0.85 x Voc of array.

When full PV power is not needed due to fully charged battery, no grid export allowed, or no AC output load to consume PV power, the SCC lighten load on PV array and allows the operating voltage on PV array to rise to reduce PV output power. In the worst case when little to no PV power is being used, the PV array voltage will approach Voc voltage of array so you must be able to take full PV array Voc on PV input at any time of operation.

The variance in startup Vmp vs running Vmp limits, is caused by stability limits on the Vmp search algorithms and SCC operation.

Initial Vmp startup search must be able to find drop offs on PV array Vmp power search for PV array loading creating an array output voltage above and below actual Vmp point.. If SCC is unable to find a definitive lower voltage drop off in power as it sweeps the PV array loading it may revert to PWM (on-off pulsing) operation, with SCC assuming the Vmp it too low for stable boost converter operation.

SCC boost converter switching duty cycle gets shorter with higher peak current as SCC boost converter must boost the PV input voltage to a greater boost ratio to achieve regulated SCC output voltage. This is a minimum duty cycle/peak current allowed to maintain SCC stability.

Once SCC has done the initial Vmp search it reverts to a tracking mode which just looks for incremental rise or fall in tracking voltage from PV array. It can track follow down to a lower Vmp voltage during this running tracking mode.

 

[1201]

Hi. Image below is from an EG4 18k PV Datasheet.

I'm just curious, what happens to the tracker if you happen to fall in the 501V-599V grey area range?
do you just get less efficiency from the MPPT?
If so, does it apply to other brands as well?

Thanks.
View attachment 282810


}

Nothing happens.

From my observations there is no power in that range.

 

[Brucey]

Zero output, until above 100v (wake up voltage).

edit: Actually needs 140v for sustained output.

Right and there's a 500V top end to that entry. Prwsumably they are limiting to 500V for actual output due to some internal aio limitation.

 

[hybe022]

Thank you all for your inputs.

Zero output, until above 100v (wake up voltage).

edit: Actually needs 140v for sustained output.

100V maybe just enough to power the inverter itself
140V to get output

Nothing happens.

From my observations there is no power in that range.

looks like playing it safe by removing 1 panel is better then?

Here's my working scenario

585W panels
Panel Voc is 51.5V
Panel Vmp is 43.2V

10x panel in a string gives
Voc 515V
Vmp 432V

Yes Voc is 515V, which is lower than 600V
But will that likely give me problems
in a very small load + full battery scenario
since Voltage will likely go up and exceed 500V mppt range

 

[timselectric]

Right and there's a 500V top end to that entry. Prwsumably they are limiting to 500V for actual output due to some internal aio limitation.

The 500-599v range is there for cold weather VOC rise.
It will still function, but isn't as efficient in that range.
Best efficiency is near the recommended 360v.

 

[Brucey]

Thank you all for your inputs.


100V maybe just enough to power the inverter itself
140V to get output




looks like playing it safe by removing 1 panel is better then?

Here's my working scenario

585W panels
Panel Voc is 51.5V
Panel Vmp is 43.2V

10x panel in a string gives
Voc 515V
Vmp 432V

Yes Voc is 515V, which is lower than 600V
But will that likely give me problems
in a very small load + full battery scenario
since Voltage will likely go up and exceed 500V mppt range

I would stick with 10 panel strings. Because the working Vmp will always be less than 500V except perhaps at first light of dawn, or when battery is full. At which point you dont need charging. Once load increase string voltage will drop into the working range.

That's assuming you are taking into account your record lowest temps and adjusting max anticipated voc appropriately

 

[Brucey]

The 500-599v range is there for cold weather VOC rise.
It will still function, but isn't as efficient in that range.
Best efficiency is near the recommended 360v.

If that was the case the operating range limit should go up to 600V? And then full power range topping out at 500V.

 

[timselectric]

If that was the case the operating range limit should go up to 600V? And then full power range topping out at 500V.

I believe that it does. It's just weird that they show 3 ranges.
EG4 is known for confusing information.
I would be curious to see the specs of the original Luxpower version.

 

[1201]

looks like playing it safe by removing 1 panel is better then?

Here's my working scenario

585W panels
Panel Voc is 51.5V
Panel Vmp is 43.2V

10x panel in a string gives
Voc 515V
Vmp 432V

Yes Voc is 515V, which is lower than 600V
But will that likely give me problems
in a very small load + full battery scenario
since Voltage will likely go up and exceed 500V mppt range

No it won't give you problems as long as you don't exceed 600v even at coldest time of year. There is no power available at VOC. Which means if there is power then you are not at VOC or even close.

My strings are 14x * 37 VOC or 518vdc

As soon as they start making any power, voltage drops to between 400-450v

 

[kennyb]

It's been very overcast and cold here. My arrays have been making a few hundred watts each at best.

I have the luxpower version.

One string spiked to 499 and then just slightly over 500 for few minutes. The mppt on that string went to 0 until the voltage dropped below 500 again.

Perhaps it was a cloud, perhaps not. But my observation for far is that it doesn't produce power over 500v.

 

[hybe022]

I believe that it does. It's just weird that they show 3 ranges.
EG4 is known for confusing information.
I would be curious to see the specs of the original Luxpower version.

here's the Luxpower version, very similar.

No it won't give you problems as long as you don't exceed 600v even at coldest time of year. There is no power available at VOC. Which means if there is power then you are not at VOC or even close.

My strings are 14x * 37 VOC or 518vdc

As soon as they start making any power, voltage drops to between 400-450v

assuming a tropical country for Voc,
does that mean i can safely do
11x 51.5 Voc = 566.5V
11x 43.2 Vmp = 475.2V

 

[hybe022]

It's been very overcast and cold here. My arrays have been making a few hundred watts each at best.

I have the luxpower version.

One string spiked to 499 and then just slightly over 500 for few minutes. The mppt on that string went to 0 until the voltage dropped below 500 again.

Perhaps it was a cloud, perhaps not. But my observation for far is that it doesn't produce power over 500v.

well, my idea of 11x string might not work then.
What's your panel configuration?

 

[mciholas]

Here's my working scenario

585W panels
Panel Voc is 51.5V
Panel Vmp is 43.2V

10x panel in a string gives
Voc 515V
Vmp 432V

My understanding is that the MPPT will not pull power from an input over 500 volts.

If that is the case, you have a situation where as the sun rises and the voltage increases, the MPPT keeps the panels loaded near Vmp and all is well. If, however, the MPPT unloads the panels for any reason, even partially, the voltage will rise to near Voc and may hit 500 volts, then the MPPT unloads them completely. Now the voltage stays at Voc until the sun sets. So it has this "latching" effect due to the voltage rising when the panels are unloaded.

There is some debate/confusion in this thread about exactly what the EG4 MPPT does above 500 volts. That needs to be clarified. I'm in the "it won't use power above 500 volts" camp on this one, admittedly without actual testing on my part. The specs are seemingly clear, 140 to 500 volts for MPPT function, 600 volts tolerated for safety. if the MPPT worked to 600 volts, why is 500 volts mentioned?

My assumption is that the inverter high rail must be limited to 500 volts to protect the AC generation side of things, so the MPPT can shut down the input at the point but also tolerate up to 600 volts itself.

9 panels * 43.2 volts is about perfect. 8 panels would also be quite good. 10 is too many.

I would suggest going for 8 panels, gathering the orphans into a separate string. Assuming you have at least 4 panels in that string, it will generate power, and 6 will make near full power. If that doesn't work, go for 7 string panels and have a long orphan string. You didn't detail your total panel count, so giving precise advice isn't possible.

Mike C.

 

[kennyb]

well, my idea of 11x string might not work then.
What's your panel configuration?

10s
Voc 49.1
Vmp 40.8

This has only been an issue once when it was -20c and the string in question was partially covered in snow and producing sub 300w.

 

[timselectric]

here's the Luxpower version, very similar.
View attachment 282820



assuming a tropical country for Voc,
does that mean i can safely do
11x 51.5 Voc = 566.5V
11x 43.2 Vmp = 475.2V

I would stick with 10.

 

[1201]

here's the Luxpower version, very similar.
View attachment 282820



assuming a tropical country for Voc,
does that mean i can safely do
11x 51.5 Voc = 566.5V
11x 43.2 Vmp = 475.2V

Yes. You can safely do 11x in a tropical country

BUT. then you are locked into a 600v mppts and your choices of inverter will be limited in the future.

If you do strings under 500voc you will have many more inverters to choose from in the future.

 

[rogerheflin]

I believe that it does. It's just weird that they show 3 ranges.
EG4 is known for confusing information.
I would be curious to see the specs of the original Luxpower version.

Generally the MPPT drops voltage to 85% of VOC.

So if you had a VOC of say 590V, the MPPT would load it up and reduce the voltage to around 500V. If the voltage is much higher than that then the MPPT is really not drawing any power. There might be an issue at load loads when the MPPT cannot load the string up enough to lower the voltage or the MPPT operating range listed may be "typical" operating range and no one considers a lightly loaded string were the voltage may be higher.

 

[sunshine_eggo]

Hi. Image below is from an EG4 18k PV Datasheet.

I'm just curious, what happens to the tracker if you happen to fall in the 501V-599V grey area range?

This will essentially NEVER happen.

Vmp is about 80% of Voc, so if you perfectly hit 600Voc, you'll be at 480Vmp.