A Sensorless Vector Control Scheme with High Bandwidth Current Loop for Surface Mounted Permanent Magnet Synchronous Machine Based on High Frequency Square Wave Type Voltage Injection

摘要

Thanks to stator flux based observer running at middle and high speed and various high frequency injection (HFI) methods operating in zero and low speed region, position sensorless field oriented vector control system of permanent-magnet synchronous machine (PMSM) has attracted much attention. Nowadays, Most of HFI methods adopt sinusoidal type voltage at high frequency as injection signal, its frequency being one-tenth of PWM switching frequency or so. Restricted by low pass filters (LPFs) and/or band pass filters (BPFs) used, the control system is implemented with narrow current loop bandwidth and high-frequency audible noise. In order to solve these problems, this paper proposes a new HFI method based on square wave, with its injection frequency equivalent to PWM switching one. Also LPFs and BPFs are replaced with a new demodulation method and then rotor position and velocity can be estimated with rotor position observer. To validate the proposed scheme, a prototype is designed with DSP-TMS320F28335. Whole control system has been designed including initial rotor position determination, magnetic polarity judgment and rotor position and speed estimation by the proposed HFI scheme in low-speed region. Experiments show that the proposed schemes are of good dynamic performance and no additional audible noise is added, its bandwidth of current loop being 500Hz, which approach to that of vector control system of PMSM with encoder.