Overmodulation strategy for high performance torque control

In the overmodulation region, the operation of the electrical drive system with a current controller is characterized by a rapid deterioration of the motor torque and speed. It is desirable to use the overmodulation strategy that extends the normal operating range even in the transient state. In this paper, in order to improve the dynamic characteristics of the electrical drive, a new overmodulation technique is proposed. Considering the current transition characteristic, an efficient overmodulation strategy is introduced to achieve better transient performance through adequate voltage selection. With the help of new overmodulation strategy, the required electrical torque can be directly produced as quickly as possible and stable machine drive characteristics can be achieved even in the transient condition. The proposed method has been implemented on an actual inverter system and thoroughly tested on a 900 W interior permanent magnet synchronous motor (IPMSM) to confirm its feasibility.