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 V<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</inf>, V<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf>, or V<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</inf> vector. The effectiveness of the proposed method is experimentally validated, demonstrating rotor position estimation errors within 0.1 rad.