Quote:
Originally Posted by cts_casemod
Sure. Angle estimations based on the operational characteristics as that motor generates two types of torque. So you need to calculate the optimum commutation angle, where the maximum torque per amp is generated
Rather than elaborate, on that engineer description, have a look at this video from 16:00 onwords
The bottom end is, if you treat the prius as a PMBLDC you will not be able to get the full performance from it, so it does require some extra work, to which FOC on its own wont solve. |
Thanks for the link cts_casemod!
Hmmm, ok - then I guess I mis-communicated. I understood angle estimators to be necessary when you didn't have an accurate way of measuring the motor angle (such as sensorless control) or were using an asynchronous machine.
I am using an extremely accurate position sensor, coupled with current sensors on at least two phases, bus voltage sensors, and motor temperature sensors. Motor speed will be derived from the position sensor. So, the bottom end is I thought I was using all this information to accurately calculate an angle - not "estimate" it.
That's actually an extremely helpful link - I was going through all the equations in my motor control books trying to come up with the equation he gives at 21:20 - this saves me a LOT of time.
The problem is I'm still trying to calculate the currents in the first place. They are functions of the motor resistance, inductance, and frequency. The ORNL tests on the 2010 Prius give resistance values, but they don't seem to provide any inductance numbers. One VERY interesting thing he points out in the video is that the optimum current angle is also related to the magnitude of the CURRENT. Jeeeze! This makes backing out the current from those ORNL output plots even more difficult. Since the current is related to the frequency, it could be controlled by either the PWM pulse width or even the switching frequency. Fortunately, all the ORNL tests are conducted with a switching frequency of 5kHz. Changing that number can dramatically change results. At this point, I'm trying to back out some reasonable inductance numbers, which are heavily reliant on switching frequency.
For P-hak, the description from about 12:30 onward describes the motor. At 19:00 he points out that the optimum torque angle is NOT 90 degrees, agreeing with what I said in my previous post. He specifically says it's not a simple "quadrature relationship" at 19:30 - this means straight SVPWM won't be enough to maximise the output of the motor.
The common assumption is that a PMBLDC motor can be pushed to 2X the base speed. In the case of the Prius motor, that's only 2*3000 RPM, or 6000 RPM. However, since the Prius motor is an IPMSM, using FOC
WITH THE RIGHT ALGORITHMS ORNL was able to push this motor to over 13,000 RPM.
So, no, I am NOT treating the motor like a PMBLDC motor; that should have been apparent in all my previous posts. Notice he quotes ORNL in the video, just like I did.
So, no I'm not going to be using FOC with fixed parameters, I will be using equations that take into account the motor's operating conditions, including it's speed.