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Electric vehicle VFD with DC bus and regen braking

Thread starter #1
Hi all.

Do we have any members with experience in constructing an electric vehicle drive controller including regen braking and CANBUS control functionality ?

My starting point is Fuji or Infineon /semikron IGBT in triple bank econopak form in size of 1200 V / 200 - 300 amp modules.

There are a few gate driver packs available , some of which solder directly to the IGBT module.

I have spent around 8 hours reading manufacturers specifications so far . some of which give rough assembly guides but I am hoping to find someone who has already been there done that and can give some shortcuts to avoid another 20 hours of study.

The typical functions in an Electric vehicle controller are to utilise a battery pack connected at the DC bus of the “VFD” ,( in reality though it’s half a VFD )

I have seen people using an off the shelf VFD / VSD in home built EV’s and just connecting the battery pack at the DC bus but to get one of 200 kW they are usually huge , I think it’s possible to build one in a footprint not much bigger than a double DIN car stereo.

The vehicles foot accelerator is a linear potentiometer , or sometimes two of them in parallel to act as a self checking redundant control input , ie if one pot fails the other one prevents the risk of reversion to an instant full throttle state.

CANBUS connectivity is desirable , so any gate module chosen has to have that capability.

a programmable interface is also required for setting function conditions for things like rate of regen braking influenced by a pressure sensor in the brake pedal and fail safes such as switching down the controller if it passes temperature limits , or if the water cooling temperature suddenly changes preset limits .

Anyone have thoughts to share on hardware configuration and software control ?
 

picbits

Well-Known Member
#2
The vehicle throttle body is often a 0.5-4.5v on one "track" and the other track is a 4.5v to 0.5v (or similar configuration) - this enables shorts / cable breaks etc to be detected. They are also often a 0-5v and a 0-2.5v output on the throttle pedal.

I've been working on some Bosch throttle bodies over the last couple of weeks and they are using hall effect sensors with magnets on the throttle drive for feedback.

I can't help you much more than that as the majority of stuff we work on is sworn to secrecy but the throttle stuff is pretty out there already.
 

picbits

Well-Known Member
#4
Some of the analog(ue) pedals I've played with have had carbon tracks which you use to make a potential divider so with a 5v supply will give you 0.5v to 4.5v. If you get an open circuit you'll get 0 volts (<0.5v is an error) or if it is shorted to 12v or 5v will be above the maximum 4.5v - some basic "error checking" there. Then there is the second track which is either half track one voltage or an inverse so 4.5v to 0.5v.

I've also come across the hall effect units which give out a straight voltage vs pedal or throttle body position.

We deal with a lot of different vehicle manufacturers so can get some quite "interesting" variations that we have to work around. You can get anything from a resistance based device to a PWM controlled device and occasionally a pure CANBUS based device. Keeps you on your toes.

Don't get me started on "smart" ABS sensors either with multilevel current signalling ...........
 
Thread starter #5
Thankyou , yup there is a lot out there , I should buy a few throttle pedal assemblies from the various EV manufacturers and pick the one best suited to my controller rather than reinvent the wheel.

I honestly don’t know yet if they use a pure resistance Pot or if it is a voltage output like your mirrored fly by wire throttle < > throttle body paired coupling.

It’s all good brain food :)
 

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