OVERMODULATION STRATEGY FOR HIGH-PERFORMANCE TORQUE CONTROL

In the overmodulation region, the operation of the electrical drive sy stem with a current controller is characterized by a rapid deteriorati on of motor torque and speed. It is desirable to use the overmodulatio n strategy, which guarantees the fast response even in transient state and satisfies the overall closed-loop control performance. In this pa per, in order to improve the dynamic characteristics of the electrical drive, a new overmodulation technique is proposed. Considering the cu rrent transition characteristics, an efficient overmodulation strategy is introduced to achieve better transient performance through an adeq uate voltage selection. With the help of a new overmodulation strategy , required electrical torque can be directly produced as quickly as po ssible, and stable drive characteristics can be achieved in the transi ent condition. The proposed method has been implemented on an actual i nverter system and thoroughly tested on a 900-W interior permanent mag net synchronous machine (IPMSM) to confirm its feasibility.