Estimation of D-Q Inductances and Initial Rotor Position Considering Voltage Distortions in High-Speed Motors for Air Compressors of Fuel-Cell Systems

It is difficult to use a position sensor for high-speed motors because of mechanical limitations such as vibration and heat. When the initial position of the motor is unknown, there is a risk of initial start failure or temporary reverse rotation. Reverse rotation would cause slight damage to an airfoil bearing in high-speed applications, degrading its durability. Therefore, an initial position estimation algorithm is required for high-speed motor drives. Additionally, to implement current controllers and sensorless control algorithms, it is necessary to know the electrical parameters. This study proposes a method for estimating the dq-axis inductances and initial position. The inductances are estimated considering the voltage distortion caused by the inverter nonlinearity; thus, the inductance values are identified with less variation regardless of the injected voltage levels. Moreover, because the inductances can be estimated even at a low voltage, there is low risk of rotor movement during the estimation process. Simulation and experimental results for a 120-krpm high-speed motor for fuel-cell systems verified the effectiveness of the proposed method.