Comparison of drive performance of PM synchronous machine fed by inverters with different PWM strategies in constant torque and constant power regions

Constant torque and constant power operation performance of permanent-magnet synchronous motors, particularly in the constant power region, not only depends on the flux-weakening control schemes but also relies on the PWM strategies. In this paper, the hysteresis control and SVPWM (including linear and over-modulation) are considered due to their popularity. An improved current regulated delta modulation (CRDM) is developed to improve the performance in both constant torque and constant power regions. The analyses, verified experimentally, show that the improved CRDM strategy demonstrates an improved torque capability which is nearly the same as SVPWM in the constant torque region, and an enlarged speed range compared with hysteresis control.