Understanding how to set MTPA Reference block settings

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Hi everyone,
I am failrly recent to MATLAB and SIMULINK. I am trying to use to Motor Control blockset in Simulink to implement an FOC algorithm. I am using the MTPA Reference block for Simulink to calculate the Id and Iq currents for me but there are parameters in the block I don't understand. What is the difference between max current and base current ? How do you calculate stator d-axis inductance ? Is this given in the motor datasheet or do we have to calculate it ? And if so, how do I do it ? What is the per-unit (PU) in I/P singal units ? Why would you choose this rather than SI units ? Also is the permanent magnet flux linkage meant to be in the motor datasheet ? I am modelling the iPower Gimbal motor GBM2804H-100T. Please your help would be really appreciated.

Answers (1)

Sharat Yadav
Sharat Yadav on 26 Sep 2021
Edited: Sharat Yadav on 26 Sep 2021
Hello Jefazo,
1. What is the difference between max current and base current ?
Base Current: Current corresponding to 1 per-unit. In general, the maximum current detected by an Analog to Digital Converter (ADC) is often selected as the base current.
Let's say,
Motor Rated Current = 5A, Inverter Rated Current(Max Current Sensed by the inverter ADC) = 20A.
So, the inverter allows maximum 4pu of current.
MPTA blocks enables a user to go in the field weakening region and based on certain operating point a user might want to allow to inject more current than the motor rated current (this can be a requirement in below base speed operations as well).
Max Current: Maximum current allowed to be injected in the motor. Its basically greater than the rated current of the motor.
2. How do you calculate stator d-axis inductance ? Is this given in the motor datasheet or do we have to calculate it ? And if so, how do I do it ? Also is the permanent magnet flux linkage meant to be in the motor datasheet ?
MCB offers Parameter Estiamtion tools, for more details visit: https://www.mathworks.com/help/mcb/gs/estimate-motor-parameters.html , this gives the required motor parameters for efficient closed loop control, Such as Ld,Lq and Flux Linkages.
3. What is the per-unit (PU) in I/P singal units ? Why would you choose this rather than SI units ?
Embedded systems engineers use the PU-Unit system for optimized code-generation and scalability, especially when working with fixed-point targets.
For more details in PU system kindly visit: https://www.mathworks.com/help/mcb/gs/per-unit-system.html
Hope this helps.
Thanks
Sharat.

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