Maximum Torque per Voltage Flux-Weakening strategy with speed limiter for PMSM drives

In this project, an improved Permanent Magnet Synchronous Motors (PMSMs) Flux Weakening (FW) control scheme, based on applications for electric vehicles is introduced. The new function of the proposed algorithm is the inclusion of both the accelerator pedal as a torque guide and the Cruise Speed Limiter (CSL) as a speed limit in a single scheme, without interfering with each other until that limit is reached. 

The existing dq-axis references are computed using a polar co-ordinate system and a per-unit system from the proposed algorithm. Moreover, because of voltage loop which changes the current-vector angle, it takes advantage of the smooth transition between the Low Back Electromotive Force (LBEF) zone and the FW zone. 

Another key advantage of the proposed system is its ability to operate without modifying the algorithm in all the dq-plane during the Maximum Torque per Ampere (MTPA), Constant Torque (CT), Current and Voltage Limit (CVL), Maximum Torque per Voltage (MTPV) and Constant Speed (CS) strategies. The proposed method is simulated and the results are verified by using a real exterior-rotor Interior Permanent Magnet Synchronous Motor (IPMSM) direct-drive e-motor bike.

Keywords: Flux Weakening, Maximum Torque per Voltage, Permanent magnet motors, Torque control, Velocity control.