DC CURRENT LIMITATION IN FOC OF PMSM

I am trying to simulate vector control of pmsm .The id iq PI takes care of the phase currents.I need to limit power also without using a PI because I already have speed PI and another PI used for FLUX weakeaning (voltage regulation based).So if have to implement it in hardware there would be 5 PI if i use a PI for DC current which is undesirable as my MCU is not that powerful.Is there any other logic to implement DC current limiting without using a PI in FOC of PMSM

Answer 1

[Pratyush]

Hi Pratheesh,

To limit power in a PMSM vector control system without adding another PI controller, you can directly limit the DC current based on power calculations. Here's what you can try:

• Determine the electrical power based on speed reference and torque command. Adjust for flux weakening if applicable.
• Calculate the maximum allowable DC current (I_{DC_{max}}) using the maximum power limit (P_{max}) and the DC link voltage (V_{DC}).
• Before setting I_d and I_q references, ensure the estimated I_{DC} won't exceed I_{DC_{max}}. If it does, scale down I_d and I_q references to keep I_{DC} within limits.
• Use a scaling factor based on the ratio of I_{DC_{max}} to the estimated I_{DC} from your current references. Adjust I_d and I_q accordingly to maintain the power within desired limits.

This would avoid the need for an additional PI controller by directly managing the power demand through current limiting, making it suitable for systems with limited computational resources.