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Modified Sine Inverters


edmundp

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18 minutes ago, The Terrible Triplett said:

Obviously no-one is going to connect a grid-tie inverter to a wall outlet, that is DB board.

You sure about that? I've been in contact with a guy who was selling a pv+micro inverter combo that you simply plug into a wall outlet... :-) Refer previous discussion of gumtree cowboys :-)

 

21 minutes ago, The Terrible Triplett said:

For my solar system, I am in the clear!!!

Pictures or it didn't happen. :-P From what I heard last, you had some loose wires... which you obviously neatened up :-)

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16 minutes ago, edmundp said:

What exactly is this anti islanding concept?

Okay, so what is Islanding? Well, suppose I'm pushing back into the grid, and we're like 6 houses in the street, two on each phase, and something bad happens and my phase is disconnected from the transformer... but the house three down is still connected to me, and if they aren't using more power than my surplus, I can feed back power to them and the two of us can form a little power island. Meanwhile the guys from the power company can't touch the wires without being electrocuted.

So anti-islanding is this scheme whereby inverters detect that and disconnect from the grid. And of course there are huge regulations around it. The Victron inverters do have anti-islanding, but it isn't up to spec for the local conditions. Our local regulations require two switches (not just one) and one must be a mechanical switch (such as a contactor), they cannot both be electronic. The Victron systems only do the electronic side. That is good enough in the UK, but not here.

So that is the first half of the story. The second half is that every Multiplus and Quatro inverter is already capable of acting like a hybrid, like an infini in other words, except the charge controller is separate. It can push power back into the grid, mix grid, solar and battery, all that cool stuff. But for that to work, it has to run interactive with the grid, and once you do that, you must have anti-islanding.

So the way to fix it is to add a separate (approved!) anti-islanding device, such as the Ufe ENS26 or the Ziehl UFR1001-e. As far as I know both those devices are approved in Cape Town (but I will have to verify). So once I have one of those between the multiplus and the grid, I can run grid-interactive. I will most likely use the hub-4 scheme, with an AC-sensor right after the meter, to avoid actual feedback. The Multiplus will then feed only essential stuff on its output, push back "to the rest of the house" up to the point where the meter stands still.

That is the idea. And here is the official documentation about it, except I will be pushing in on the DC bus.

https://www.victronenergy.com/live/system_integration:hub4_grid_parallel

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Ok. So in simple terms - what would a user need to:

Not feed back to grid.

Using a 3kVA 24v Multiplus

That can import power from grid if usage goes above 3kVA?

Is it even possible?

Sent from my SM-N900 using Tapatalk

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29 minutes ago, SilverNodashi said:

yup, that's all you need. 

Yup, that device is all you need. It's spec'ed to the German VDE-AR-N 4105, so it really ticks all the boxes. Sometimes you can pick them up on ebay for less, but then the shipping kills the deal.

ABB also makes one that should be sufficient, but isn't on the list: http://za.rs-online.com/web/p/monitoring-relays/8762557/

So the 11k sounds steep... but it's already significantly cheaper than it was a few months ago.

So, you'll need the Ziehl device (7k), the CCGX (another 7k), and the AC sensor (another 4k), so it's a good 18k worth of stuff. Mighty steep... but I was already making plans for the big battery bank I was going to buy which would have been double that... so you can see why I'm suddenly back in love with my original goal of 2013? :-)

2 hours ago, edmundp said:

Not feed back to grid.

So here is how it works. There's a piece of software that runs on the CCGX. It takes all the numbers from the various sensors (AC consumed, battery level), makes a decision, and then instructs the inverter to push power into the grid, or take power from it. If the Multiplus it hears nothing from the CCGX for 500 cycles (10 seconds) it switches to bypass mode. So that's the safety function.

Since there is an AC sensor on the input, the software can calculate a feedback rate that is less than your consumption and thereby avoid feeding back. There's two things I don't know: 1) How fast does it react to changing power levels, and 2) if the current hub-4 implementation can do this balancing yet. If it doesn't react quickly enough, it might trip some prepaid meters. So truth be told: Technically it is possible, but there's some homework left to be done.

2 hours ago, The Terrible Triplett said:

I presume your can go with the free Pi version of the Color Control GX, not the actual one?

The software required for this might not be packaged for the Rpi (yet?) The dbus-cgwacs software (that reads the AC sensor) is open source, and it looks like that's all that is needed. But even then, it's not a deal breaker, as far as I know there is an official release for the Beaglebone Black, and that is only about twice the price of the Rpi.

So honestly... there's still work left here to be done.

Edit: Checked quickly, cgwacs (https://github.com/victronenergy/dbus-cgwacs) is packaged for the Rpi already.

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Then again, the infini (ootb, out of the box) doesn't have a grid limiter either, so there will be extra cost there, and you also don't have to use the CCGX, you can use cheaper hardware, so techies CAN get the price a good 5k lower... and you get the VRM site stuff for free on top of all that, so as a value proposition... and given the rock-solid blue inverter below all that, it's still a fairly good value proposition. Especially if you already have the hardware as I do :-)

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Just now, plonkster said:

Then again, the infini (ootb, out of the box) doesn't have a grid limiter either, so there will be extra cost there, and you also don't have to use the CCGX, you can use cheaper hardware, so techies CAN get the price a good 5k lower... and you get the VRM site stuff for free on top of all that, so as a value proposition... and given the rock-solid blue inverter below all that, it's still a fairly good value proposition. Especially if you already have the hardware as I do :-)

A Microcare grid limiter can be had for R2.3k. 

 

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13 minutes ago, SilverNodashi said:

as far as I know, no. 

Mmmmmh. Now I wonder how that thing even works. If it's like an AC sensor with a comms interface... well then you already know what's going through my mind now. Read it... integrate it :-)

Edit: I googled into pteradactyl's ad on BoB, which states explicitly that this only works with the MC inverter. It looks, from the complete lack of info to suggest something else, that it uses PLC (power line communication) to talk to the inverter. Very competitive price for that kind of product! The other two I know is the Victron one (around 4.5k) and the WattNode that is used with the Solar Edge inverters (also around 4k).

Anyone have a broken MC limiter lying around that I can play with? :-)

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5 hours ago, plonkster said:

Then again, the infini (ootb, out of the box) doesn't have a grid limiter either, so there will be extra cost there, and you also don't have to use the CCGX, you can use cheaper hardware, so techies CAN get the price a good 5k lower... and you get the VRM site stuff for free on top of all that, so as a value proposition... and given the rock-solid blue inverter below all that, it's still a fairly good value proposition. Especially if you already have the hardware as I do :-)

The infini does not need it. It's all built in already. You just set in the software what limit you want to the grid.

Realy the price alone makes it almost impossible to look somewhere else if you look at all that you get in the infini

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2 hours ago, viper_za said:

The infini does not need it. It's all built in already. You just set in the software what limit you want to the grid.

Realy the price alone makes it almost impossible to look somewhere else if you look at all that you get in the infini

The topology I am talking about is where you have only part of the house on the inverter, and want to push back just enough to power "the rest of the house", but not so much that it trips your prepaid meter. So the Infini is such good value that you can get the "big one" and just have the whole house on it, so it is really hard to have an apples for apples comparison, but say you put the Geyser on the grid, how would you use surplus to party power the geyser for example... :-) It really isn't a problem, just saying... that's sort of the space where I'm dabbling.

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Thank you all for the detailed explanation.

One thing I am not yet clear on - I do not want to feed back to grid at all. In fact this must not even be possible.

But I might need to import from grid should the load go beyond a certain threshold, i.e. 3000VA thus taking 3000VA from inverter and "combine" that with let's say 500VA from grid to give 3500VA. This will happen very seldom, but happens occasionally due to ill-household-communication....

@plonkster - sorry for the 20 questions, but it is a bit of different thinking this.

Edit: Let me explain further in terms of what was just posted. My entire home except for geyser backup and swimming pool pump is wired through inverter. Thus - my base load is 90% of the time sub 500W, but sometimes someone? switches on everything at the same time in lethal combinations - i.e. microwave while dishwasher is running, etc. How do I in those circumstances import power from grid to overcome the shortfall - without the entire system tripping and sending the house in an emotional downward spiral? :) 

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37 minutes ago, edmundp said:

Thank you all for the detailed explanation.

One thing I am not yet clear on - I do not want to feed back to grid at all. In fact this must not even be possible.

But I might need to import from grid should the load go beyond a certain threshold, i.e. 3000VA thus taking 3000VA from inverter and "combine" that with let's say 500VA from grid to give 3500VA. This will happen very seldom, but happens occasionally due to ill-household-communication....

Edit: Let me explain further in terms of what was just posted. My entire home except for geyser backup and swimming pool pump is wired through inverter. Thus - my base load is 90% of the time sub 500W, but sometimes someone? switches on everything at the same time in lethal combinations - i.e. microwave while dishwasher is running, etc. How do I in those circumstances import power from grid to overcome the shortfall - without the entire system tripping and sending the house in an emotional downward spiral? :) 

The infini will be able to do that. You disable "feed back to the grid", so no power will be fed back and if your load exceeds what your panels and/or battery can supply, the remainder will be drawn from the grid - that is how the hybrid works. Some people on this forum have had loads of about 8KW (266%) on the 3KW infini without any issues. I did a test on mine once where I loaded it with 5.5KW for about 15 minutes without any issues. I would not recommend doing it 24/7, but periodically should not be a problem.

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@SilverNodashi- how would you rate the overall efficiency of the Infini?

How responsive is the MPPT portion in terms of demand/power usage changes? Let me explain - one of my pet peaves with the Axpert is the slow response time of the MPPT. Quite often when the batteries are nearly full and due to either a substantial change in load or sudden light condition change the MPPT will first maintain current level (either boosting charge volts by up to 1.5V above setpoint for a few seconds or dipping the same) then followed by yet another boost or fall, followed by a fall and then only settle down. Each phase lasts a couple of seconds. Repeat this a couple of times a day and it leads to all sorts of data anomalies. Plus the DC bus voltage on the inverter side ranges between 396VDC and 451DC when this occurs - I do not think this is so healthy.

And then the ever important question in my mind - what is standby usage in idle?

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