Position Detection and Speed Recording Method for Power-Off IPMSM in Full-Speed Range Based on Ultrahigh Frequency Signal Injection

For the sensorless interior permanent magnet synchronous motor, this letter proposes a rotor position and speed recording method applied in full-speed range after the main power supply is off. The proposed method injects ultrahigh-frequency (UHF) sinusoidal voltage into the motor windings after the motor is powered off, and then calculates the motor rotor position and speed in real time by detecting the root mean square (RMS) value of the UHF sinusoidal signals. Based on the UHF signal injection method designed for the low-speed region, this letter improves the injection and detection timing and optimizes the online calculation method of rotor position and speed. The proposed method can work only when there is no power supplied to the motor, and it is used solely for the purpose of recording. This letter implements the first inductance-based full-speed motor power-off rotor position detection and speed calculation. It breaks the cognitive limitation that the inductance-based rotor position detection method is only applicable to the low-speed region.