Hybrid Inverters That Can Use AC Output of Enphase Microinverters?

[pone]

I am a newbie to solar, and in doing my first review of my site, I have significant shading issues. This makes microinverters attractive since the difference in output for each panel could be significant, and I do not want my worst panel taking down the performance of other panels. Do any of the popular hybrid inverters (EG4, Sol-Ark, or Deye) have good options to use the AC output of microinverters as their input power, then do the AC to DC conversion internally to store to batteries? Obviously that requires some power losses doing that conversion.

 

[Quattrohead]

Yes all of the mentioned can do something called AC coupling.

 

[pone]

Yes all of the mentioned can do something called AC coupling.

So how is that done? Do I send the microinverter outputs to the "Generator" port on the inverter? Most of these inverters appear to have ports and breakers corresponding to

a) AC outputs/inputs to grid
b) AC outputs to a critical AC load
c) DC outputs/inputs to batteries
d) AC inputs from a generator

 

[pone]

Now I am wondering if I just send the microinverter outputs to a critical loads panel, and do the inverters have an ability to take any excess AC on that back and divert it to the battery or the utility panel/grid?

 

[DougL]

So how is that done? Do I send the microinverter outputs to the "Generator" port on the inverter? Most of these inverters appear to have ports and breakers corresponding to

a) AC outputs/inputs to grid
b) AC outputs to a critical AC load
c) DC outputs/inputs to batteries
d) AC inputs from a generator

On the EG4 18kpv you connect to the GEN input and set the config for AC-coupling. This way the GEN input will get an AC signal even when the grid goes down and it can direct power from that input to charge batteries along with running loads.

 

[pone]

On the EG4 18kpv you connect to the GEN input and set the config for AC-coupling. This way the GEN input will get an AC signal even when the grid goes down and it can direct power from that input to charge batteries along with running loads.

On EG4 is it possible to send the microinverter output straight to your critical loads panel and then have any excess energy go back to the inverter to power the batteries or the main panel? The advantage to that would be that if you lose your inverter, you still have energy going to your critical loads....

 

[Quattrohead]

Yes the inverter will handle all of this automagically.

 

[RCinFLA]

HF inverters are more vulnerable to AC coupling excess power absorption. Using the firmware reconfigured generator port allows the HF inverter to immediately release from PV GT inverter feed if HF hybrid inverter gets into trouble with excess power.

Freq shifting by hybrid inverter causes PV GT inverters to back down their output, but its reaction time is too slow to prevent possible HF hybrid inverter damage. This is why gen port PV GT inverter disconnect is necessary.

Two examples where frequency shifting is not fast enough. (freq shifting can take a couple of seconds to react)

1) back feeding large amount of PV power to grid and grid suddenly goes down.

2) Off grid, large PV production and large house loads consuming the generated power. Someone shuts off a large house load leaving a lot of excess PV power to immediately deal with.

 

[DougL]

HF inverters are more vulnerable to AC coupling excess power absorption. Using the firmware reconfigured generator port allows the HF inverter to immediately release from PV GT inverter feed if HF hybrid inverter gets into trouble with excess power.

Freq shifting by hybrid inverter causes PV GT inverters to back down their output, but its reaction time is too slow to prevent possible HF hybrid inverter damage. This is why gen port PV GT inverter disconnect is necessary.

Two examples where frequency shifting is not fast enough. (freq shifting can take a couple of seconds to react)

1) back feeding large amount of PV power to grid and grid suddenly goes down.

2) Off grid, large PV production and large house loads consuming the generated power. Someone shuts off a large house load leaving a lot of excess PV power to immediately deal with.

Nice! Living up to your forum label "Solar Wizard". Thank you for your service.

 

[pone]

HF inverters are more vulnerable to AC coupling excess power absorption. Using the firmware reconfigured generator port allows the HF inverter to immediately release from PV GT inverter feed if HF hybrid inverter gets into trouble with excess power.

Freq shifting by hybrid inverter causes PV GT inverters to back down their output, but its reaction time is too slow to prevent possible HF hybrid inverter damage. This is why gen port PV GT inverter disconnect is necessary.

Two examples where frequency shifting is not fast enough. (freq shifting can take a couple of seconds to react)

1) back feeding large amount of PV power to grid and grid suddenly goes down.

2) Off grid, large PV production and large house loads consuming the generated power. Someone shuts off a large house load leaving a lot of excess PV power to immediately deal with.

Do you design hardware? You are showing a very deep knowledge of these systems, and I appreciate that.

What if I went for an inverter that is not high-frequency, such as the Schneider XW Pro? This has an enormous surge capacity. But would it be happy to take in my micro inverter AC power from panels on the critical loads network instead of the generator port?

 

[RCinFLA]

LF inverters are inherently bi-directional power flow with their MOSFET PWM on primary side of heavy LF transformer.

HF inverters have to switch their battery to HV DC converter from forward power to reverse power for battery charging. This takes several milliseconds for the switch over during which time there no excess PV power sent to batteries. SolArk, Deye, and EG have a large bank of high voltage DC capacitors that provide a small amount excess power absorption.

This bidirectionality makes LF much better at handling sudden AC coupling excess PV power. You still need to worry about battery state of charge, keeping a reserve of not quite fully charged battery to allow room for AC coupling excess power back push to batteries without inverter D.C. input voltage being pushed beyond max. limit for hybrid inverter.

 

[pone]

This bidirectionality makes LF much better at handling sudden AC coupling excess PV power. You still need to worry about battery state of charge, keeping a reserve of not quite fully charged battery to allow room for AC coupling excess power back push to batteries without inverter D.C. input voltage being pushed beyond max. limit for hybrid inverter.

Do you have any opinion on the Schneider XW Pro inverter?

 

[Quattrohead]

Do you have any opinion on the Schneider XW Pro inverter?

They are amazing inverters but not for the DIY crowd, very complicated to get working properly.

 

[pone]

They are amazing inverters but not for the DIY crowd, very complicated to get working properly.

Is it correct that Schneider does not make an XW Pro larger than 6 kW? It's clear they are focused on high end applications, so it's unbelievable that they would not support 12 kW and 18 kW options. From what I am seeing stringing two 6 kW systems together is non-trivial, requiring both software configuration and extra wiring steps. For my applications a single 12 kW box that used a transformer and could handle big surges easily would be an ideal product. I'm not thrilled about the extra complexity of stringing multiple 6 kW boxes together.

And it looks like I should probably try to find an installer with a lot of Schneider experience, not just an experienced electrician.

 

[pone]

This bidirectionality makes LF much better at handling sudden AC coupling excess PV power. You still need to worry about battery state of charge, keeping a reserve of not quite fully charged battery to allow room for AC coupling excess power back push to batteries without inverter D.C. input voltage being pushed beyond max. limit for hybrid inverter.

This review of XW Pro versus Sol-Ark seems to prove very well that the LF designs handle motor loads whereas HF inverters struggle to even meet their rated loads when dealing with motor starts:

By the way, there is a way to configure XW Pro to interface with a battery management system and deal with state of charge.

 

[bestconcreteblock]

Someone shuts off a large house load leaving a lot of excess PV power to immediately deal with.

I have trouble with this explanation that Victron also uses to describe AC coupling.

It is my understanding that current is drawn from the PV GT inverter at a rate that is controlled by the voltage difference between the PV GT inverter and the grid voltage. This voltage difference is controlled by the PV GT inverter. Using the term "excess power" doesn't really make sense to me. "Excess Voltage"... Maybe.

 

[Quattrohead]

Yeah these explanations have never made much sense to me either, I mean you turn the light switch off, the electric stops instant it's not like it blows your wire out of the wall.

 

[ksmithaz1]

This review of XW Pro versus Sol-Ark seems to prove very well that the LF designs handle motor loads whereas HF inverters struggle to even meet their rated loads when dealing with motor starts:

By the way, there is a way to configure XW Pro to interface with a battery management system and deal with state of charge.

This video is over 2 years old. I clicked thru noticed a bit of bias, which is OK, I'm sure if I was selling 'Golden Sunshine' solar products I would probably bias my presentations a little, nothing super flagrant here. Noted a number of comments complaining about the software/firmware for the unit being horrid (likely at the time).

The round trip loss is significant, but to be fair, pretty much 8 hours is the limit for solar production, so you only have 16 hours of conversion loss with an HF vs 24 on an LF. Here in AZ that is significant, because that represents over half of my daily power usage in the summer, other places could go the other way.

A few other items as well, Much of the firmware on these HF units have improved dramatically, and some of the newer HF units are claiming even better handling of hard starting inductive loads than the current crop. I'm sorry, but this will continually get better as time passes, and I would expect many of the devices like Well pumps and the like will have built in soft start functionality as time moves forward just like the latest inverter A/C tech. There was never any demand for these products in the past, but with the adoption of localized power production in more rural spaces there is now also a demand for improvements in things like well pumps and other motors with high inductive startup loads. As these products mainstream the cost differences will diminish to the point that nobody will buy the old stuff.

Output/lb of gear might be fun on this as well.

 

[ksmithaz1]

This bit of propaganda by EG4 presents loading an 18Kpv to shutdown

I can say I've *never* had my inverters shut down from being overloaded. Will has done a number of video's beating up a number of HF inverters as well. I'm going to struggle with the argument for LF inverters at this point. With the current evolution of HF solar inverters, pretty much everyone is abandoning the LF model.

 

[kscessnadriver]

I see the HF hater/LF shills are out in full force again

 

[ksmithaz1]

I see the HF hater/LF shills are out in full force again

Meh, LF is better at starting heavy inductive loads, I looked it over when I put my stuff in. The problem is cost and weight. There are folks getting these because they are on-sale, the problem is they are also EOL. Frankly I was torn between Sol-Ark and EG4, $$$ made the choice, but I knew I was going to endure some pain with a product shipping with wet paint. The HF stuff has gotten so much better at this over the last couple years. In fact the comparison video above was using an older 12K for the HF unit, and it was still pretty decent. All these units have been thru multiple firmware updates, and I'd bet the latest releases of the hardware will be even better, as the problems in the field are noted and corrected.

I just don't see a future in low frequency inverters, copper wire is expensive in windings and adds significant weight.

 

[pone]

This video is over 2 years old. I clicked thru noticed a bit of bias, which is OK, I'm sure if I was selling 'Golden Sunshine' solar products I would probably bias my presentations a little, nothing super flagrant here. Noted a number of comments complaining about the software/firmware for the unit being horrid (likely at the time).
View attachment 274645
The round trip loss is significant, but to be fair, pretty much 8 hours is the limit for solar production, so you only have 16 hours of conversion loss with an HF vs 24 on an LF. Here in AZ that is significant, because that represents over half of my daily power usage in the summer, other places could go the other way.

A few other items as well, Much of the firmware on these HF units have improved dramatically, and some of the newer HF units are claiming even better handling of hard starting inductive loads than the current crop. I'm sorry, but this will continually get better as time passes, and I would expect many of the devices like Well pumps and the like will have built in soft start functionality as time moves forward just like the latest inverter A/C tech. There was never any demand for these products in the past, but with the adoption of localized power production in more rural spaces there is now also a demand for improvements in things like well pumps and other motors with high inductive startup loads. As these products mainstream the cost differences will diminish to the point that nobody will buy the old stuff.

Output/lb of gear might be fun on this as well.

I mostly ignore the detailed testing done on the Sol-Ark, as that might be a hatchet job, and I also sensed some bias. But the unmistakable evidence in that video is that LF inverters truly shine in abusive conditions where there are massive increased loads for short periods of time. Conceptually this must be the case because of their design, and the testing reinforces that. To me this has real-world value, as even a single family home might have the oven, electric stove, clothes dryer, and HVAC systems all turn on in close proximity to each other, creating very large surge events. LF inverters have the best chance of being reliable in such environments.

In terms of conversion losses, I had ChatGPT construct a table (attached) to put some approximate data behind your point: at low power draws, the LF inverters become more inefficient. On a 6 kW inverter, drawing at 2 kW steady-state, the LF inverter is about 3% less efficient than HF inverter. But if you have a low load under 500 watts, LF inverters can have 10%+ additional conversion losses. But, to be fair, does that even matter because the losses are against low loads. So numerically that does not stack up to much. Further, the idle losses of the Schneider LF inverter is under 35 watts, versus 100+ watts for the HF inverter.

 

[pone]

I can say I've *never* had my inverters shut down from being overloaded. Will has done a number of video's beating up a number of HF inverters as well. I'm going to struggle with the argument for LF inverters at this point. With the current evolution of HF solar inverters, pretty much everyone is abandoning the LF model.

Succinctly, what do you think are the reasons for abandoning the LF model? Is the only issue conversion losses?