Derivative Speed Feedback Scheme for Improved Speed Control of Interior Permanent Magnet Synchronous Machine at Overmodulation Region

Linear region which is inside the inscribed circle of the voltage hexagon in the voltage plane is widely used in the permanent magnet synchronous machine (PMSM) drives for steady operation. For electric vehicles, however, torque and speed capabilities under limited battery voltage are of great importance. Hence, the area outside the inscribed circle, known as overmodulation region, must be utilized to enhance the capability. With the exploiting of overmodulation region, the dynamic voltage is less and the degradation of speed control is inevitable. A new algorithm is presented in this paper to overcome the issues. A better control of speed in the overmodualtion region can be obtained with a low total harmonic distortion (THD). The effectiveness of the proposed method is verified by simulations.