Some time ago, I talked to a very well educated technician about this problem. He told me, that technically, of course there is a solution. One way of having 3-phase converted to single-phase (with balanced loads on the 3-phase end) is power electronics converters. (not directly the same approach as dpeilows ATS device with UPS inside; but have you seen its dimensions? and 288kg? puh!).
But in this case, he sayed that here we are in the part of industrial power electronics, no "playground items", and for 15kVA with european certifications, he expected this in the price-range between 8k EUR and 10k EUR, likely more....
Another solution is a theoretical one. Use a 3-phase motor, and the motor shaft connect to an alternator. There, use only one phase of the alternator. You will have your single phase, and the primary load on the 3-phase motor is balanced. Well, efficiency isnt the thing of that solution. And the lack of sound of EVs you wont experience - because you then will have it in your garage while charging ...
So, solution seems to be as simple to as to live with the unbalaced loads.
One important thing is: power is not power. There is a wide variation of how power can be drawn out of the grid. And this variations have different "Netzrückwirkungen" (grid retroactive effects? grid feedback?).
So with variant A, you might be allowed to draw the amount of x kVA out of the grid. But with variant B, you might not be allowed.
Here is the link of the (in austria at least, in germany and switzerland also what I have understood) responsible regulation, the TOR:
A&B - Strom
scroll down till the files beginn with "TOR". unfortunately, its hundreds of pdfs in german language.
From what I have understood:
This thing is based on law from the european legislative. Each country then puts this in its national law.
For me, its seems they devide into different devices based on the technics, and on this different technics, a device can draw different power amount out of the grid. But when you are manufacturer of a device and within that limits, nothing can "happen" to you, you can sell this device - you have legal certainty.
This amounts are very low, on one part there were only 1.5kVA, the maximum I found was 4.7kVA.
When you and your device do exeed this, then there is a procedure. Its in "Hauptabschnitt D2, page 146" - the form you have to fill out and submit to your grid provider. Then they will judge it if -the way you are drawing out the power of their grid- will influence their grid; and therefore they will allow you or not.
I do my best to translate some kind of things they are asking here:
- Power/max.Power
- 230V/400V/3x400V/others
- alternation of load often yes/no
- Stromrichter ("power converter? line-commutated power converter?") yes/no
- Energy back to the grid yes/no
- Power factor correction yes/no; if yes, which type, kvar
- Direktanlauf(direct start?)/Anlaufhilfe(?)/Leistungssteuerung(power control?)
- Phase controlled modulator yes/no
- Schwingungspaketsteuerung (?) yes/no
- Pulssteuerung (? pulse controlled?) yes/no
- Drehstromsteller (AC power controller? regulator?) yes/no
- Frequenzumrichter (frequency converter / inverter?) yes/no, if yes, from Hz to Hz
- Stern-Dreieck-Anlauf (star-delta connection ?) yes/no
- Starting under load yes/no
- how often starting in which time period
- proportion of starting current vs. regular current
Based on this technical data, they may calculate and allow you to use or not use the device, and make additional suggestions. But "device has xy kW / kVA" is not enough for their judging.
Hmm. You see its very complicated. I have my exemption
But overall, dpeilow is right. The most cheapest and easiest solution is to change the charging electronics. I have talked to the same technician on this issue, and told him about the ACP licence technics using the motor for charging, etc.; but he said nice, but however the car "internally" works, it is not that complicated to design a device to accept 3-phase input at an of course balanced load. (he explained somthing from a few diodes here, some bridge rectifier circuit there; but I am not that kind of technician to understand this ;-), over all minimal costs).
But it would need some time to make an own EU-PEM accepting 3-phase from the grid, and a new connector (5pin at least, when not taking the blue Mennekes one which would be the only useful solution); this would lead in a new Mobile connector, etc.
But time is the only thing Tesla does NOT have when it comes on deliveries of european cars; its a pitty that they have overseen this completely, like other things on the european homologation.