Applying FOC techniques to control PMSM with PWM

The speed-control concept of PMSM includes speed and current loops as FOC theory.

The concept here is

• Firstly, measure current Iabc from PMSM and convert to (d,q) frame by Park-Clarke transformation
• The PMSM measured speed goes to speed controller, which will gives output as current Iq_ref
• Id_ref is set to zero because we want to control the speed lower than nominal speed of PMSM. If we want to control speed higher than nominal speed of PMSM, Id_ref is set below zero according to flux decay principle.
• Then, two currents Id and Iq go to PI controller, compares with Id_ref, Iq_ref and export two stator voltages u_sd, u_sq
• Two stator voltages u_sd, u_sq go to inverse Park-Clark transformation, which gives out three phase AC Uabc
• After that, Uabc go to PWM block, generate PWM pulse to 6 valves of IGBTs of the Inverter block.

Some important equations:

Relationship between electric and mechanism

Stator voltages usd, usq in (d,q) frame

Flux equations in (d,q) frame

Electrical moment equation

If isd is set to zero, electrical moment me only depends on isq (because flux p is constant)

Stator currents equations in (d,q) frame

Result simulations with speed, moment, current Isq, current Isd

We can see that the speed is tracked to speed_reference, electrical moment is tracked to load, Isd to set to zero as expectation.

Acknowledgments

• I really appreciate Assoc. Prof. PhD Tien Dung Le and senior Quang Vu Truong - University of Da Nang, University of Science and Technology, Vietnam for supporting me this work.
• "Truyền động điện thông minh" book, Prof. PhD Nguyen Phung Quang, Ha Noi University of Science and Technology.