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Forum Index : Electronics : Mack-OffGrid -- 100 Volt -- WarpVerter
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mackoffgrid Guru  Joined: 13/03/2017 Location: AustraliaPosts: 460 |
Having the experience of working on my 26 volt Warpverter I'm already well on my way to designing my next Warpverter - the 100 Volt 3 phase WarpInverter. My three phase inverter is simply three inverters, synchronised 120 degrees from each other. Why 100v ? Because it's cooler to have a 100 Volt inverter than a 96 Volt inverter.  I am persuaded by Tony's arguments to use a Diode isolated, 100 Volt battery, online solar array. The site currently has no power system at all. This is where the house will be and more importantly, this is where the machinery shed is. We'd like to be able to power hungry devices such as welders, compressors, and maybe a car hoist (hydraulic pump). So a 100 Volt system system gives me a better basis for more powerful surge handling capacity. I have always planned on installing a 10kW solar array but since solar panels are becoming quite inexpensive, I shouldn't be surprised if I eventually end up closer to 20kW. Tony's diode isolated method is attractive because it provides the full capacity of the solar array, instantly, as well as the batteries to drive any surge requirements. This is a formidable combination. I do have some of my own add-on ideas to add to this but they're not germane to this discussion. The decision to make the solar array permanently online wasn't quite that simple. This affects the dynamic range of the input voltage to the inverter. Under cloudy conditions, and I am 15km from the coast so I do get quite variable conditions, the system could be down to the batteries and at 100v. In ten seconds time I could be in a patch of clear midday sky, by which time the array has lifted the DC rail to 160 volts, maybe more. If Tony wasn't living with these conditions already I would have been a slower to try this. So ... The inverter has to have a wide dynamic input voltage range. It's not that difficult a decision to make a Three Phase Inverter since I'd always make a secondary / backup unit. Going Three phase just means I need a third unit. But.. my three phase Warpverter will be just a network of three individual single phase Warpverters controlled by an external controller. These Warpverters will be multi-mode inverters being able to change from three stand-alone inverters, doing there own thing, to syncing up to act as a three phase system. The control system should also be able to run two or even the three Warpverters in parallel to create a larger single phase should it be necessary. Then there's the switch-gear to interlock and make sure the correct phase is connected to the right distribution feed etc. And feedback systems to ensure power sharing isn't too far out of wack.... I had planned to make the individual inverters good for 6kW continuous or near enough. 6kW would make quite a reasonable inverter, a Three phase inverter at 6kW per phase, 18 kWatts should start and run any compressor or hydraulic pumps that I'd operate. The mechanical design will deviate significantly from the 26v Warpverter. Mark's Locker idea is much closer, a vertical stack of transformers from the bottom, Aerosharp heatsinks with the fins in the vertical direction, and heatsinks kept intact and isolated from Mosfets etc. Capacitor bank as a seperate module. There is NO rush to build the Three phase Warpverter, by the time it takes me to gather all the bits and test fresh designs it'll be this time next year before serious testing will be afoot. Cheers Andrew |
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| arthur8 Regular Member  Joined: 08/05/2019 Location: BrazilPosts: 69 |
Nice, Andrew. I love three phase inverters. Will be looking your topic, i want to make a three phase inverter in the future too. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Great stuff Andrew. The rather unconventional system I have here has been running for almost two years without any problems. Still tinkering about with the finer details of the battery charging current profile, and individual battery cell monitoring, and the cell balancing system, but the inverter part of it has never missed a beat. Inverter will run quite happily straight off the solar panels without anything else during the day. Inverter design operating voltage range is 90v to 180v, but the solar voltage never gets higher than 145v, and the battery never lets it get any lower than 95v near end of discharge. Three individual phase locked inverters makes perfect sense, the voltage correction on each phase can then work quite independently for unbalanced loads. Your Nano board would be preferred, but my hardware Warpverter control board could very easily be phase synchronized by applying a very narrow reset pulse to the address counter reset pin. That would force the zero crossing point, and phase correct every cycle. So only a very simple system for locking three phases together at 120 degrees would be required. Even easier with Andrew's Nano. Andrew and I have already discussed all of this, and our ideas coincide perfectly. Cheers, Tony. |
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| mackoffgrid Guru Joined: 13/03/2017 Location: AustraliaPosts: 460 |
Tony, I'll make the system work with either the stm32_Warpverter or an Eprom based controller. Yes, the nice thing is that the 3 inverters do not have to be of equal size. Using current sensors, a feedback mechanism can balance the load. I have a lot of the electronics designed in my head and on back of envelopes, but the next step is the transformer design. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
The transformers are the main starting point. If I was going to start this all over again from scratch, I think I would have wound my transformers with two 90v primaries that could then be wired either in parallel or series. Its not a big deal at the winding stage, but I wish now that I had thought of doing this at the time, it woulds have been so simple then. A one hundred volt system is very good for 5Kw, but for say 10Kw or more, I think 200v dc needs some serious consideration. Fifty amps or less is pretty easy to deal with, but a hundred amps or more starts to need some rather serious and expensive hardware on the dc side. Cheers, Tony. |
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| mackoffgrid Guru Joined: 13/03/2017 Location: AustraliaPosts: 460 |
Transformer Design : - Flux Density Tony, Thanks for the real world Solar voltages, its narrows my design parameters. At this stage I'm happy for the output to sag when Vin < 100V. I don't have panels yet, may not for some time. So I'm going to assume for operating range is 100 Volts to 150 Volts, but with the realisation that the no load voltage may be 180V. So, I'm thinking of setting B (tesla) to 1.5T when Vin = 150 which gives me a B of 1.0T at 100 volts, so the night time core losses will somewhat lessened. But, at Vin = 180 Volts B = 1.8T I have no problem with extra losses at Vin=180 because its almost never going to happen except on startup of the entire system. But I still need to allow for it. At what Flux Density does the transformer cease to be a transformer (or dangerous)? >2T? Cheers Andrew |
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LadyN Guru Joined: 26/01/2019 Location: United StatesPosts: 408 |
I don't know why, but everytime I read this, it makes me very very happy. A few months ago, when I would ask this and people would say I was dreaming and this possibly could not happen, I would be disappointed and look for solutions because I knew that there had to be a way to do direct instead of batteries being mandatory. ... but I did not know how. The same people, now, months later, still say solar direct possibly cannot happen, but now I understand what could happen (eg: supply sag), under what circumstance (eg: cloud cover) and how to mitigate it (eg: load share with grid). Thanks to each of you wonderful people. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Natasha, there is a caveat with that. If there is only 1Kw of solar on a gloomy day, and your refrigerator takes 200 watts, but needs a 3.5Kw surge to start up, you may be in trouble unless there is some very serious capacitance that can support that extra load for just a second or two. Its almost mid winter down here, and really grey skies for days on end, and my battery never gets a full refill. So early morning my battery is very low. It will run things fine, but it struggles starting my refrigerator. I get a huge scary voltage dip. So it WILL work straight from solar, but the sun actually needs to be there !  !![quote]So, I'm thinking of setting B (tesla) to 1.5T when Vin = 150 which gives me a B of 1.0T at 100 volts, so the night time core losses will somewhat lessened. But, at Vin = 180 Volts B = 1.8T[/quote] If you go into all this flux density calculation stuff a bit deeper, it starts to get really complicated. As the dc voltage rises the flux density is supposed to rise in proportion, but the primary never sees a pure sine wave voltage, or a full 50%/50% duty cycle square wave voltage either for that matter. So the real flux density is going to be lower because of the third (zero voltage) logic state we are using in all of our inverters. Not only that, apart from the largest inverter, the switching frequency is higher than 50Hz, so volt microseconds are far less as well. Plus at higher voltages our lookup table makes all the switching events a bit shorter. Now initially, I assumed that the smaller inverters could be designed with fewer turns because of the much faster switching, but doing that increases both eddy current and hysteresis core losses to an unacceptable degree. So based on my own practical experience of what works, and what does not, I have suggested to everyone that all four transformers be simply designed for one Tesla with sine wave drive, and the rms value equal to the lowest dc voltage. This assumption is fiction, but it hugely simplifies the design, because on line flux calculators are readily available, and the resulting transformers will all work very well. We can just ignore all the really complicated design stuff, and just assume this is a normal everyday sine wave transformer. And it will work. Idling power does rise with higher dc voltage, but when that happens it will be from excess solar, so it does not matter. When running off battery at night, we will be way down low near the minimum of the voltage window, where idling power becomes much more important. And we can get pretty good performance down there. Cheers, Tony. |
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| mackoffgrid Guru Joined: 13/03/2017 Location: AustraliaPosts: 460 |
Thanks Tony, I appreciate the the little bit of extra explanation - it was enough to satisfy my query without getting bogged down in math and minutia.  So, in my case I'll be designing for 1T at 100 Vrms. It was pretty much where I was thinking and you've nailed it down. You would like to go to two primaries so you could expand to 180 Volt battery and solar? I had to build my bravery just to go to 100V (180V unloaded). I got zapped by 240ac several times when I was in my late teens but the last one left me shaking and a little burn on my finger. Never been shocked since. Over the years my bravado tank has been totally emptied. Cheers Andrew |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
[quote]So, in my case I'll be designing for 1T at 100 Vrms. It was pretty much where I was thinking and you've nailed it down.[/quote] If you expect the absolute minimum will be 100v, then that is where its going to drop out of voltage regulation. [quote]You would like to go to two primaries so you could expand to 180 Volt battery and solar?[/quote] I will probably never do it, but 180v would have been a nice option to have. The IGBTs would be more efficient and less stressed, and the electrolytics would store more Joules. I can understand why the 48v guys are stuck there, HY4008s are dirt cheap, and its below the statutory 60v ELV threshold. But some people are talking about building 10Kw+ inverters at 48v which will present some interesting problems from the high current and high losses aspect. Cheers, Tony. |
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| LadyN Guru Joined: 26/01/2019 Location: United StatesPosts: 408 |
Tony, in your experience, do you think the Chinese would sell > 60V inverters? The Chinese don't seem to care much about safety or standards - they sell anything for which there's a high volume demand but there seems to be a severe lack of > 60V inverters on our usual sources, which means there's a significant lack in demand for > 60V inverters. If this is the real reason - Why? |
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| kentfielddude Regular Member Joined: 09/05/2019 Location: United StatesPosts: 89 |
It's based off of lead acid batteries. There's a lot of 48v systems and equipment pre-existing . Finding a mppt charge controller for a 96v battery system is difficult but most support 48v. You do get those grid tie inverters that take 200-500v dc in. Additionally the higher voltage requires parts that are generally more expensive and not worth the cost for a small inverter. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
More than a few high voltage dc input grid tie inverters are manufactured in China, even if the company that finally markets them is "Western". As Natasha says, the Chinese will rapidly exploit any product where there is a perceived demand. Mike, while you are thinking through the whole transformer design in greater depth, and its a pretty interesting and unique application ! there is one very curious aspect. All four transformers have square wave voltages on both primaries and secondaries. The flux in the core also switches very abruptly to support those voltages. So essentially from the voltage aspect these are high frequency transformers with fast voltage rise times. The main issue with that concerns charging and discharging stray winding capacitance. As the switching frequency becomes faster, particularly in the smallest inverter, the required flux swings to support the voltages become very much lower, and that greatly reduces eddy current effects in the core that would normally become a problem at higher frequencies. All four transformers have perfect continuous 50Hz sine wave currents in both the secondaries and primaries. This has no effect on the rapid flux swings in the core, but it has a very important effect on the windings. The windings themselves work exactly as a more usual sine wave driven transformer, without any additional high frequency effects such as skin effect. We can just use the standard design wire current density of four amps per mm squared without any other other design issues. So for current, these are all just normal low frequency transformers. Cheers, Tony. |
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| Solar Mike Guru Joined: 08/02/2015 Location: New ZealandPosts: 1138 |
I was asked the question today, when we move to the new site can we get our 3 phase workshop equipment running from the battery bank..... said will investigate. We currently have 3 x 50 volt @300AH battery banks, so 50v @900 AH at the 20 hr discharge rate. I could build 3 x 5kw 50v inverters all synced from a 120 degree 3Ph generator board, that would have more than enough grunt to start the big planer. Or place all batteries in a series 150v bank and design everything to run off the higher voltage.... Any Ideas ? Cheers Mike |
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| mackoffgrid Guru Joined: 13/03/2017 Location: AustraliaPosts: 460 |
Mike, I'm not telling you anything new, 50v design is probably a bit cheaper in parts, a bit safer to play with, 150V will work a bit better. I think If you are adding a solar array then it tips it even more in favour of 150 volts. Cheers Andrew |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
I would go 150 volts too. The trick would be to have two pole isolation switches on each 50v battery bank, so that each battery can be completely isolated from everything else for maintenance. I have been running a 100v battery and have never even had a faint tingle... ever.` Cheers, Tony. |
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| mackoffgrid Guru Joined: 13/03/2017 Location: AustraliaPosts: 460 |
Having a brother that's had a quad bypass, and a cousin just this week had a dual bypass, I feel rather apprehensive about receiving shocks. Tony's experience has relieved me of most of my anxiety and these shocking youtubes helped a little more.ElectroBoom - High Voltage AC/DC Effect on Human Body Great Scott - AC VS DC - Pain Test (Experiment) I don't think either video represents the likely mechanism of how we receive a shock. But it does show relative experiences. Cheers Andrew |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
I read something a long time ago about shock susceptibility, and it appears that skin condition has a lot to do with how high you jump at a certain voltage.... Worst case is wet skin, and women tend to have more moisture in their skin, especially if they are constantly rubbing skin moisturizer into their hands, as many do. Men have far less of a conductive skin problem, and us old wrinkled grey haired guys are the luckiest of all as far as having a very high skin resistance goes. I originally faced my 100v battery with much trembling terror, but after having full contact several times, and never even feeling a tingle, I am now far less concerned. Mind you, I always TRY to power down or isolate anything I am working on, but its no longer the nightmare it once was. Cheers, Tony. |
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