Minimum Voltage Injection for Sensorless Control of IPMSMs using Three-Shunt Current Sensors

This paper presents a switching-frequency voltage injection method for low-speed sensorless control using three-shunt current sensing inverters (TCSIs). Due to the current sensing limitations of TCSIs, the injection frequency is limited to half of the switching frequency using conventional injection-based sensorless methods – PWM modification is required to achieve switching-frequency voltage injection. Therefore, this paper proposes a switching-frequency voltage injection method that requires no PWM modification. The rotor position is estimated by utilizing current derivatives measured from a single active vector. To accurately measure current derivatives, a minimum duration of the active vector is required. To ensure this condition, the minimum voltage injection (MVI) method is introduced, which guarantees sufficient duration of the V1, V3, or V5 vector. The effectiveness of the proposed method is experimentally validated, demonstrating rotor position estimation errors within 0.1 rad.