Position Sensorless Drive Technique For Surface-mounted Permanent Magnet Synchronous Motor

Surface-mounted permanent magnet synchronous motors (SPMSMs) havebeen widely used in many fields, such as aerospace, industry and domesticappliances due to the benefits of high power density, high efficiency, compactstructure and simpler control system, etc. The position sensorless controltechnique can reduce the cost and improve the reliability of the control system.Therefore, it has important theoretical and practical value to study positionsensorless control technique for PMSMs. This paper mainly studied the positionsensorless control technique for SPMSMs under the background of low-cost andreliable integrated fan system based on SPMSM. Besides, a DC bus voltagecontrol strategy is proposed to cope with short-term power failures such asvoltage dips and interruptions, improving reliability of the integrated fan systemfor industry application.In low speed range, the Back-EMF based sensorless technique suffered fromthe low amplitude of Back-EMF. To solve the problem, a sensorless startupmethod with current regulation was introduced. The self stabilization mechanismof startup method was analyzed and a guideline was also given to start up themotor to certain speed even under different load condition. To achieve a smoothtransition from startup control to sensorless FOC, an easy-realizing transitionstrategy was introduced.In order to achieve a better performance for sensorless field oriented control(FOC) in the medium and high speed range, a novel sliding mode observer (SMO)was studied. In the novel SMO, an adaptive Back-EMF observer was presented toreplace the low-pass filter in the traditional SMO, achieving a full-order stateobserver for motor current and Back-EMF with better precision and reliability. Aquadrature phase-locked loop (PLL) was adopted to extract the rotor position andspeed information from the estimated Back-EMF, which could increase theresistance to high-frequency interference. The guideline for parameter selectionwas given on basis of the analysis of the bandwidth and dominant poles of thePLL.In order to improve reliability of the integrated fan system for industryapplication, the DC bus voltage control strategy was proposed to cope withshort-term power failure such as voltage dips and interruptions. The math modeland energy flow was analyzed for three-phase voltage source PWM rectifier,then the voltage and current double closed-loop control strategy was put forward.In case of short-term power failure, the mechanical energy stored in motor and load side was used to guarantee the stability of the DC bus voltage.At last, all the methods presented in this paper were validated using thesimulation and experimental results on a500W SPMSM for fan application.