Gen2 vs. Gen3 Prius inverter for home PV

[NiHaoMike]

I'm looking to build my own inverter for a home PV (solar power) system. Part of that is because I like to build stuff, part of that is because so far, I have only found one (really expensive) off the shelf inverter with most of the features I want. Most notably powering loads on the AC "input" side without exporting to grid, since getting paid to export to grid involves too much hassle for my preferences. Instead, I plan to use an EV battery (most likely a Nissan Leaf or Chevy Volt pack, either the whole pack or part of one) as a buffer and a thermal storage system using a heat pump compressor to heat or cool water in tanks for HVAC. The solar production goes into charging the batteries, operating the thermal storage compressor, or powering other AC or DC loads.

How I propose to use the Prius inverter:
MG2: 2 phases for AC "input" (120V/240V US mains), 1 phase for AC output (120V UPS), all via LC filters. Neutral created using center tap of external capacitor bank connected to DC bus of inverter. (Will have to figure out how to handle DC imbalance when disconnected from grid.)
MG1: all 3 phases to thermal storage compressor.
Boost Converter: high voltage battery interface if pack voltage is less than 340V or so of peak 240V mains.
DC/DC: low voltage battery charging, could it reach the 16V or so needed to charge a 4S lithium pack?
A/C inverter: all 3 phases to thermal storage condenser fan, will have to use different solution if Gen3.

Control for all of the above will be handled in a FPGA, with some sort of embedded computer connected to it handling the high level control like network communication. From what I have read, the Gen2 inverters are wired so that if enabled, the individual phases can either be high or low but not open, while the Gen3 inverters allow an open state, which I prefer when I only want power to flow in one direction. (Correct me if I'm wrong or if there's a trivial mod to the Gen2 to allow that function.) Are there any other things to be aware of like different switching frequencies? The Gen3 inverters cost more so I would prefer to go for a Gen2 if it doesn't involve too many tradeoffs.

To elaborate on the "AC input", it connects to a 120/240V split phase circuit, then there are current sensors installed on the main feed in the breaker box that send readings to the control circuit. If there's an AC load, the inverter will source current to offset what the load is drawing up to the limit of the PV or surplus battery power available. I might add a contactor to allow that to do double duty as a "lower priority" UPS function, but planning to leave that out at first to reduce complexity.

[arber333]

It seems like you expanded a bit from my concept of Prius gen 3 charger.
viewtopic.php?f=14&t=257

Also i had in mind a charge pump that could in fact do what you intend, and more...
viewtopic.php?f=7&t=82&hilit=charge+pump

development TBD...

[NiHaoMike]

It seems like you expanded a bit from my concept of Prius gen 3 charger.
viewtopic.php?f=14&t=257

Also i had in mind a charge pump that could in fact do what you intend, and more...
viewtopic.php?f=7&t=82&hilit=charge+pump

Basically that but in reverse. It takes DC and makes AC that is in step to what the load is drawing at any moment.

[Plebian]

Hello NiHaoMike,

I like where you are going with this concept, especially using thermal energy as a means of storage which is something I contemplate frequently also! I have gone down some rabbit holes in regards to cryogenics and liquefaction of air and other gas's as a means of high concentration energy storage. The mainstream contemporary scientific script that the energy required in liquefaction of air requires to much energy and is an inefficient means of energy storage is laughable at best and malicious and evil at worst, when you research some technologies that have been floating around and dissappeared or distorted from newer versions of "scientific' mainstream western literature.

How have you progressed with it all? I currently have a prius gen 2 available to strip the inverter off and and hoping to use it for similar although initially less complex a setup. This is my first time on and posting to this forum and I am still at the early stages of learning electronics so I'm probably not of much assistance to yourself with this type of technical detail. If you have any documentation or resources that might be useful to myself to help with customizing the gen 2 inverter to use as a home solar inverter I'd be extremely grateful if you could share or point me to their location online

[Kevin Sharpe]

Jack from EVTV is looking for a HV solar inverter/charger... maybe he'd help fund the development?

[johu]

... dissappeared or distorted from newer versions of "scientific' mainstream western literature.

Please do not nurture conspiracy theories here. You've been warned.

[Plebian]

No mention of any conspiracy or theory so not the intent. I'll make sure to communicate clearer next time with specific references to any specific situation or context to avoid any misinterpretation.

Again any assistance or guidance in the right direction would be greatly appreciated, especially with the current global uncertainty.

The variant of the Prius parts I have available right now are from Australia also.

[RichardZ]

Has anyone tried to put high voltage DC from solar panels in to the Gen 3 inverter with a logic board?, will it pass through the rectifier stage without problems?
I've got 26 solar panels that produce 30 volt each, so 12 will give 360 volts and with two in parallel 24 panels will give 16 Amp.
There's a video of testing the Gen 3 inverter and if I understand correctly, the single phase input is converted to DC, then the battery DC is boosted to match the rectified AC before the charge sequence begins.
Running the Prius AC air con pump as a heat pump is a great idea, so you can potentially keep a Prius battery pack charged and use any excess solar power to run the heat pump.
I am keen to get 3 phase in the workshop and run some low power 3 phase machines, not daily but just as and when I need them for a project.
Most of the energy in our house goes in to heating water, central heating, showers, washing machine etc.
LED lighting could perhaps be fed from the DC/DC converter plenty power there.

[NiHaoMike]

No need to waste an inverter/rectifier phase for that, getting to the DC bus connections is as easy as removing a cover.

[RichardZ]

Thanks
Looking at the ABB ACS355 it's like you said, they describe how to connect the solar DC input to the brake + _ (DC bus) terminals of the VFD, plus they seem to have firmware for MPPT to optimise the solar output.
So technically it's possible to develope the Gen 3 inverter to have input from: solar PV / 3 phase generator / single phase mains.
(not simultaneously)
And have 2 times 3phase output with VFD of say 10 KW for about 30 minutes from an old Prius battery(?)--- Heat pump and DC LED lighting output.
(simultaneously )
Wow that's a lot of off grid capability running silent and free.
Oh yeah plus you can potentially (fast or slow) charge your EV battery with any one of the power sources.
Is there a project page for this topic? I might start one, once I get a bit more hardware together.

[Kevin Sharpe]

And have 2 times 3phase output with VFD of say 10 KW for about 30 minutes from an old Prius battery(?)

The Prius Gen 2 battery has a 1.3kWh capacity and could potentially deliver 10kW for ~5 minutes depending on the efficiency of the inverter.

[RichardZ]

Oops, turns out the power from a Prius battery is very limited, more like 5 minutes of 10KW in stead of 30.
Direct PV drive through an inverter heat pump is still worth a try though, it's a system that stores energy without the need for a battery.

[NiHaoMike]

Direct PV drive through an inverter heat pump is still worth a try though, it's a system that stores energy without the need for a battery.

I plan to still use a battery since the dynamic range of off the shelf HVAC compressors is limited - 2:1 is about the limit for most although a few can do 3:1 to 4:1 by mode switching.

[RichardZ]

Would a belt driven automotive air con compressor not have the dynamic range?
I need to select a 3 phase motor for a truck size air con compressor, and initially I'll try to run it off 2.25 KVA PV using an ABB CS355.
I found one of these inverters and thought its worth a try and see if it will work like a solar pump.
The ABB is 5.5 KW and uses MPPT PV input via the brake + / - connectors, not tested the thing yet, nor the power out of the solar system.
The air con system I have got is a new installation that was meant to go on a military truck (24 Volt), so motor choice and minimum rpm is an interesting concept. A proper Frankenstein set up!
Would the Prius inverter in combo with the air con and the battery do the trick, or perhaps a bigger EV battery?

[NiHaoMike]

The limiting factor is the minimum speed needed to operate the oil pump. Most use centrifugal pumps, while high dynamic range compressors use gear pumps or separately driven pumps. That sort of variable speed compressor is not very common on the surplus market.

I haven't looked into how automotive compressors are designed, the main problem is that they are not built to operate for a lot of hours at close to full power.

[RichardZ]

We have some Carolla hybrids at work which were left for a few months and the main batteries were drained.
The dealer just jumped them by connecting the starter pack to some 12V terminals, there's a youtube clip with this example as well.
Does that mean that these inverters can boost towards the HV battery and charge them, is that a route open to Solar input DC as well?

[RichardZ]

Is it possible to use the Gen3 inverter and logic board to run different inputs and outputs based on Can Bus?
I would like to charge with solar, start and charge with a small single cylinder engine using a stand alone MG motor, run a Prius air con compressor and have a 3 or single phase outlet?
I know that's asking a lot but is it possible to multi task?