I would like to purchase or build a simple AC-DC power supply, with 400V/32A 3-phase input, and DC output adjustable (by a microcontroller which I would add) between 300-400VDC and upto 100A (not exceeding 22kW total). The purpose would be to charge an electric vehicle via the fast charge port (CCS or ChaDeMo), which provides direct DC access to the vehicle's battery (usually around 350VDC and 15-70kWh depending on car type). Such power supplies are really expensive (I haven't found any under 5000$) and I have a hard time understanding exactly why they are so expensive. It doesn't need to be isolated, since all parts are extremely well protected from touching. The output voltage is pretty close to the input voltage, and never higher, so shouldn't a rather simple PWM regulation be enough, no transformers, no big voltage differences? (I know such a power supply is not enough to charge an EV, the microcontroller part needs to communicate with the car via CAN (ChaDeMo) or Powerline (CCS), and multiple safety circuits must be implemented, but I already know how to do that, what's missing is the power supply part).
Power factor correction is the hidden biggy with any powerful 3 phase AC to DC converter. It’s simply not the case that the rather elegant 3 phase rectifier circuit can be piggy backed with a boosting power factor correction circuit. This will not work. This is because the elegant 3 phase rectifier (used for many tens of years if not a hundred years) just doesn’t allow it to happen. See this for an explanation.
This won't work: -
Because the current in each phase falls to zero while its respective voltage is still very high: -
The only viable alternative is to regard the 3 phases as 3 individual supplies and have power factor correction replicated for each. Then there is the requirement to maintain load balance so, there has to be significant cross checking between each phase and finally, each of the 3 boost converter's outputs has to be managed so that it can be adequately merged with the other two boosted DC voltages: -
There is a lot of overhead here and I reckon power factor correction alone is about 50% of the BoM cost for the circuits.
I’m not saying that $5k is a justifiable price to pay of course but given the market and trends and hidden complexity of PFC, it doesn't surprise me at all.