Francisco's Electric Pajero

Post up a thread for your EV. Progress pics, description and assorted alliteration
antiscab
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Real Name: Matthew Lacey
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Re: Francisco's Electric Pajero

Post by antiscab »

francisco.shi wrote: Fri, 16 Apr 2021, 21:01 I have been thinking making it V2H capable.
The plan is to connect an inverter via the DC charge port.
I am going to make an isolated bidirectional DC link and feed the output to a solar inverter via the solar panel inputs and the solar panels will go to my converter. So that way I can feed the house from the solar or from the car.
You could use a separate inverter for the V2H - an export limiting inverter would probably be most cost effective (fronius, goodwe, etc)
the upgrade for a fronius symo to do export limiting is only $500 on 3-phase
Matt
2017 Renault zoe - 25'000km
2007 vectrix - 156'000km
1998 prius - needs Batt
1999 Prius - needs batt
2000 prius - has 200 x headway 38120 cells
francisco.shi
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Re: Francisco's Electric Pajero

Post by francisco.shi »

coulomb wrote: Fri, 16 Apr 2021, 21:36
Neat! Presumably, you'll have some sort of adjustable sag that the inverter sees, so it knows when to stop drawing power (when it sees what it thinks is the maximum power point).
That is one way. So the add on box will have a CT to decide how much power to give the inverter and make the bus sag until the MPPT draws the right power.
The main disadvantage is that I could not charge from the grid using this setup.
In my opinion any car should be able to share the battery thru the DC charge port. This way it would not need any hardware changes in the car. All it would need is a software update to stop the car disconnecting the battery if it sees the charger trying to discharge the battery.
francisco.shi
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Re: Francisco's Electric Pajero

Post by francisco.shi »

I did a bit more work on the inverter software today.
I have been having some problems with the control loop. As the speed goes up it gets to a situation where the control loop seems to be unable to control the current.
Here are the readings from the Q axis.
Q axis.
Q axis.
20210501_220428.jpg (1.38 MiB) Viewed 163 times
The feedback goes down even as the output goes up and also the current goes up. Eventually it trips on overcurrent.
Here is the D axis sowing the same problem.
D axis
D axis
20210501_220504.jpg (1.37 MiB) Viewed 163 times
After some thinking and doing a few tests I came to the conclusion that the problem is due to the measurement and the update of the output taking place too far apart. After the measurement is taken the control loop does the calculations and it then updates the PWM values which get updated on the next PWM cycle. The end result is that as the speed goes up the rotor angle changes enough that when the update happens it is already too far off. I had already added some compensation for the rotor speed. The problem was that there are 2 PWM cycles between the measurement and the update but I was only allowing for 1 cycle.
Here is with the fix implemented.

The motor got to about 8krpm (about 100kph)
I didn't get a plot of the currents. I will do that later and will post them.
Tomorrow I will do some work on the field weakening.
antiscab
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Re: Francisco's Electric Pajero

Post by antiscab »

I look forward to seeing your field weakening results

Are you planning on doing field strengthening too? (more low end torque and more effective low speed regen)
Matt
2017 Renault zoe - 25'000km
2007 vectrix - 156'000km
1998 prius - needs Batt
1999 Prius - needs batt
2000 prius - has 200 x headway 38120 cells
francisco.shi
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Joined: Mon, 17 Sep 2018, 16:30
Real Name: Francisco
Location: Brisbane, Strathpine

Re: Francisco's Electric Pajero

Post by francisco.shi »

From the maths it seems field strengthening should allow for more torque at low speeds but I am not sure if it works. I am not sure if something in the magnetic path may saturate or if the windings will be able to take enough current.
I have done some testing on field weakening before but it appears very inefficient. So far to get the motor to spin at twice the speed I have had to apply the rated current to the D axis which leaves nothing for the Q axis. If I did field strengthening I would expect a similar problem. I didn't test the field weakening under load so I can't tell how well it will work and when I tried to do the field strengthening I did not seem to get more torque. I didn't measure the torque accurately because I have no way of measuring the torque on the motor especially when it is moving at speed.
The only way I can apply a load to the motor is to drive the car.
The other problem I have testing field weakening is that my driveway is not long enough to get to speed and maintain the speed and I don't want o drive the wreck on the road. It is a bit too obvious.
The plan for field weakening is to come up with a method of calculating the current that I need to apply to the D axis. I need to measure something and then increase the current as the speed increases.
One idea is to look at the output voltage and increase the D current as the output voltage gets close to saturation and run a control loop that keeps the output voltage from reaching saturation.
francisco.shi
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Real Name: Francisco
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Re: Francisco's Electric Pajero

Post by francisco.shi »

I didn't get any work done today. Some friends came over and ended up just playing with the car.
But I did get some videos:

This is a demonstration of the one pedal braking accuracy.
I would challenge any other EV driver to do the same without touching the brake.
This one I just wanted to do an acceleration test to compare to before when it had only one motor but didn't take it from the right angle.
fffffred
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Re: Francisco's Electric Pajero

Post by fffffred »

amazing work @francisco.shi
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