I hope somebody will be able to help me here.
I'm working on EV traction inverter firmware development for PMSM motors. I have MCSPTR2A5775E: MPC5775E Development Kit as a reference and I'm developing my own algorithm to drive a PMSM. In the example software for the Dev Kit we can see that several PMSM FOC control methods have been used (Voltage control, Current control, Speed control etc). I wondering, what would be the most suitable PMSM FOC control method out of Current control and Speed Control to be used in EV applications ?
Thanks & Regards,
Motor control kit MCSPTR2A5775E provides several different control strategies based on traditional FOC and one standardized U/f control scheme.
This portfolio of control structures is targeting the final application debug.
U/f control or Scalar control is mostly dedicated to position sensor debugging. You can verify the polarity of position and its accuracy.
In FOC voltage control, you can verify the current sensing accuracy as well as current sensor polarity.
FOC Current control is dedicated to application current loop tuning.
You can modify current loop PI gains. The current loop represents the based line for all traction applications. The FOC current loop or Torque loop is the most frequently used motor control structure for traction drive use-case. Torque is proportional to current. Current multiply by torque constant is resulting in torque. The torque constant is an electric machine-specific number.
At the end of our example, there is a FOC speed loop. This scheme is dedicated to speed control loop tuning. In the traction drive use case this control strategy represents the cruise control.
The most suitable control strategy for the main traction drive is current control and speed control.
Thank you very much for your answer.
One thing to get clarified, what is the possibility and effectiveness of implementing field weakening and regenerative braking algorithms along side current control rather than speed control.
with best regards,
The current loop provides independent control of both Id as well as Iq current.
Id is also known as flux component of stator current can be used for magnetic flux supporting and also weakening. Proper sign in the Id component of current allows us to change magnetic flux. This change is resulting in field weakening operation as well as in reluctance torque excitation.
The presence of reluctance torque depends on PMSM machine geometry especially inductances in d and q axes.
Iq is also known as the torque component of current and is responsible for synchronous torque production. Iq can be controlled independently too.
In main traction drive applications, we are using tables for getting the proper combination of Id and Iq related to the required torque. This is the most commonly used control strategy for the main traction drive use case which requires independent control of both Id and Iq currents.
Regenerative braking is possible in the current loop too. The Current loop allows us to operate in all four quadrants.
Thank your very much for your explanations and clear answers throughout the thread. Pleasure to have get clarified the problems I had regarding FOC algorithms.
With best regards,