Consideration of Carrier Based Signal Injection Method in Three Shunt Sensing Inverter for Sensorless Motor Control

This paper considers the carrier based signal injection method in three shunt sensing inverter (TSSI) for sensorless motor control and analyzes the loss according to the injection axis of the voltage signal. To remove both phase current and rotor position sensors, sensorless method and phase current reconstruction method can be simultaneously considered. However, the interaction between two methods can be incurred when both methods inject the voltage signal simultaneously. In this paper, the signal injection based sensorless method with 120° OFF Discontinuous PWM (DPWM) is implemented in TSSI to avoid this interaction problem. Since one leg does not have switching event for the one sampling period in 120o OFF DPWM, the switching loss is altered according to the injection axis. The switching loss of the d-axis injection case can be up to 32% larger than the one of the q-axis injection case. Other losses according to the injection axis are also analyzed.