PMSM motor drive for Electric Vehicle applications

To control air pollution in urban areas and to reduce carbon print in the cities, nowadays EV’s are preferred over IC engine vehicles. Earlier Electric vehicles used DC motor and Induction motors. But Brushless Permanent Magnet motors are preferred over Induction motor for EV’s due to their High Torque density, high-power density and highly efficiency. Prevalent Electric vehicles today have Brushless DC motors. Compared to BLDC, PMSM motor have smoother control and negligible torque ripplesThus, PMSM motor is preferred over BLDC for Electric Vehicle, because of its sinusoidal back emf which results in smoother control, and results into smoother and more comfortable driving experience to users. Methodology Sensor based field-oriented control (FOC) is implemented in 48 V 5kW Interior PMSM motor. . To start the Synchronous motor initial position of the rotor magnetic field should be known. After rotor alignment, incremental encoder is used to detect the rotor position or rotor flux position. As incremental encoder gives relative position, rotor is aligned to a known position, and then algorithm moves to closed loop FOC. In FOC, the sensed stator current is decomposed into torque and flux producing component, thus achieving decoupled control of PMSM drive. Space vector pulse width modulation is used to control the stator voltage vector. During low speed with high torque requirement the motor is operated in constant torque region and moves into field weakening region during high speed cruising operation. Regenerative braking implemented by setting negative reference for torque producing component of stator current. Results In FOC, maximum torque is achieved during acceleration from zero to low speed operation. Wider field weakening range is obtained. Smoother control of PMSM with negligible torque ripple is achieved due to Sinusoidal Back EMF.