A starting method and design of sensorless vector controller for PMSM automotive compressors

Abstract

Aiming at the problems of large starting inrush current and frequent overcurrent protection triggering under heavy load in the sensorless drive system of permanent magnet synchronous motors (PMSM) for vehicle air-conditioning compressors, this paper designs a low-cost sensorless vector controller. A back-EMF state observer is adopted to estimate the rotor position and rotational speed, and a smooth-switching startup algorithm based on vector angle tracking is proposed. On the hardware side, a three-shunt-resistor sampling scheme combined with current reconstruction technology eliminates position sensors and dedicated current sampling chips, which reduces equipment size and hardware cost. A test platform equipped with a 1.5 kW rotary electric compressor is built for experimental verification. The test results demonstrate that the proposed controller achieves stable speed regulation within the range of 2000–5400 r/min. Under 320 V DC bus voltage and an 18 kg heavy-load condition, the starting current inrush is suppressed to only 7.8 A. The system features slight speed fluctuation and low operating noise. It is applicable to miniature vehicle compressors with power below 1.5 kW and possesses promising engineering application prospects.