Maximum Torque Per Voltage(MTPV) control of an IPMSM Power Drop issue in Deep Flux weakening Areas

I have a 6KW motor so theorictically after constant torque region the power must be maintained constant at 6KW.My problem is that power is dropping at high RPMS.The flux weakening method I use now is Voltage Saturation Method However when I load the motor the Vd saturates to vmax(Vdc/sqrt(3) )before I can get 6KW power thus I cannot push more id and I am getting almost 25% less power in Higher RPM areas.The Motor is an IPMSM with infinite speed (-sif/Ld) is less than imax.So Will implementing MTPV help in getting more power out of the motor.I currently switch from MTPA to fw along the current limit circle using voltage saturation Now how to identify transistion point from fw region 1 to MTPV region that from Current limit circle along the voltage limit circle to the center of the voltage limit circle which is inside the current limit circle in this case.What are the equations governing this operation.Upon searching mathworks references I found MTPA control reference block which has two equations governing fw control in IPMSMS one which gives max torque for a given speed value and one for a given speed and torque value.How to transistion between these two modes and which equation is the one representing MTPV operation.

Answer 1

[Vinay]

Hi @PRATHEESH S

MTPV (Maximum Torque Per Voltage) is used in high-speed region to maximize torque under voltage constraints.

MTPV solves the optimization:

Subject to the voltage constraint given as

​

Where:

• : PM flux linkage
• ​: d-q axis inductances
• : d-q axis currents
• : inverter voltage limit

The MTPV trajectory is the set of (id,iq) that maximize torque under the voltage constraint.

For more information on the equations governing the MTPV algorithm, please refer to the resources below.

https://ut3-toulouseinp.hal.science/hal-03545358/document

https://www.researchgate.net/publication/329793601_Operational_Improvement_of_Interior_Permanent_Magnet_Synchronous_Motor_Using_Fuzzy_Field-Weakening_Control

I hope this helps!

[PRATHEESH S]

Thank you

Answer 2

[Raghunath Rachabattuni]

Hi @PRATHEESH S,

For implementing MTPV beyind FW region of operation (wherever it is possible depending on the motor's parameters), feel free to use the block "LUT based PMSM Control Reference". Also refer to the detailed description at the following link

PMSM Constraint Curves and Their Application - MATLAB & Simulink Example

And visit the following link to watch a video on the same subject:

Optimal Torque Control Workflow for Permanent Magnet Synchronous Motors - MATLAB & Simulink