转矩脉动抑制
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直接转矩控制磁链低频脉动分析及抑制丁惜瀛夏强赵鑫杨树平刘强(沈阳工业大学电气工程学院,沈阳110023)绱要本文蔗计算杭仿真鳃方法,详细分析了篮接转矩控制系统低频脉动的产生原因,解析了电机温升引起的定子电阻变化对定予磁链的估计精度的影响,提出用改进型磁链观测器替代传统的积分观测器;同时针对低频时逆变器开关频率避低导致转矩脉动增加的问题,细化磁链位置判别,降低传统露壹接转矩控割系统麓低频磁链辣赫,使控刽系统有更高戆嚷应速度和更强戆鲁槔性。
并用M a t l a b/Si m ul i nk软件建立了该直接转矩系统的仿真模型,仿真结果表明了改进方案的有效性。
关键词:直接转矩控嬲;低频脉动;磁链观测器;计算机仿真A na l ys i s and R e st r ai n of L ow Fr equency R i ppl e f or D i r ect T or queC ont r ol of F l ux L i nkageD i n g X i y#,g X i a Q i ng Z h ao x滚Y ang Shupi ng Li u Q i ang(School of E l ect r i ca l E ngi neer i ng,Shenyang U ni ve r si t y of T echnol ogy,Shenyang110023)A bs t r act I n t hi s pa pe r,t he r ea s o n of l o w蠹eq uen cy r i ppl e i n di r ec t t or que cont rol s ys t em i s di s c us s ed usi ng com p ut er s i m ul at i on m et hod,t he i nf l uence of st at o r r e si st a nc e change caused by m ot or t em perat ure r i se t o pre ci si on of st at or f l u x l i nka ge com p ut e is been anal ys ed.T he pap er br i ngs f or w ar d t hat t he t r a di t i on al i n t egr a l ob s er ver s houl d be subst i t ut e d by a novel f l ux obser ver.A i m i ng at t he i nc r ea s ed t or que r i ppl e pr ob l em caus ed by l ow i nver t e r s w i t ch f r equ ency at l ow fr e que ncy,t he pap er re fi ne d t he par t i t i on of f l ux posi t i on t o dec re a se t he l ow f r equ ency f l ux r i ppl e i n t he t r adi t i ona l di r ec t t or que c ont rol,w hi ch m a ke cont rol s ys t em have m or e r a pi d r es ponse s peed and m o r e H i gh l y R ob ust.T he pap er set up s i m ul a t i on m od el of di r ec t t or que c ont r ol s ys t em us i ng M at l a b/Si m ul i nk,t he s i m ul a t i on r esu l t i ndi c at ed t he va l i di t y of t he i m pr oved m e t hod。
International Journal of Automotive Technology, Vol. 12, No. 2, pp. 291−297 (2011)DOI 10.1007/s12239−011−0034−8Copyright©2011KSAE
1229−9138/2011/057−16
291TORQUE RIPPLE MINIMIZATION CONTROL OF PERMANENTMAGNET SYNCHRONOUS MOTORS FOR EPS APPLICATIONS
G. H. LEE1), W. C. CHOI1), S. I. KIM2), S. O. KWON2) and J. P. HONG2)*
1)Graduate School of Automotive Engineering, Kookmin University, Seoul 136-702, Korea2)Department of Automotive Engineering, Hanyang University, Seoul 133-791, Korea
(Received 18 February 2009; Revised 9 August 2010)ABSTRACT−This paper identifies a control method used to reduce torque ripple of a permanent magnet synchronous motor(PMSM) for an electric power steering (EPS) system. NVH (Noise Vibration Harshness) is important for safe and convenientdriving. Vibration caused by motor torque is a problem in column type EPS systems. Maintaining a very low torque ripple isone solution that allows for smoother steering. Theoretically, it is possible to design and drive the motor without torque ripple.However, in reality, a PMSM system torque ripple is caused by the motor itself (saturation in the iron core and EMF distortion)and the imperfect driver. This paper analyzes torque ripple of a PMSM system, and an advanced PMSM control method forthe column typed EPS system is presented. Results of the analysis indicate that the compensation current is needed in orderto minimize torque ripple when a PMSM is driven.
KEY WORDS:Electric power steering, Magnetic saturation, PMSM, Torque ripple, Deadtime, EMF distortion
1. INTRODUCTIONResearch is being performed to improve the fuel efficiencyof vehicles. One of the main areas of focus is on thesteering of auxiliary equipment. Electric Power Steering(EPS) is receiving more attention than Hydraulic PowerSteering (HYPS). Electric power steering (EPS) is a systemthat supplies motor power directly to the steering to assiststeering torque while HYPS uses an oil pump that is drivenby the engine (Shimizu and Kawai, 1991). A permanent magnet synchronous motor (PMSM) hasbeen used to improve the performance of EPS. Since aPMSM has many advantages, such as high efficiency andhigh torque per rotor volume, it is especially suitable forautomotive applications in which space and energy savingsare critical (Miyoshi et al., 2005). In a column type EPSsystem, the PMSM is linked to the steering shaft via areduction gear. This connection transfers the motorvibration and torque fluctuation directly through thesteering wheel to the hands of the driver (Zhang et al.,2008). For this reason, only the ripple between one andthree percent of rated torque is permitted. Several technical papers have presented a motor designandcontrol technique to reduce cogging torque and torquepulsation (Islam et al., 2005; Mattavelli et al., 2005; Bianchiet al., 2002; Lee et al., 2008). However, this paper discussesan estimation method of compensation current for suppress-
ing torque ripple caused by a PMSM (Lee et al., 2008).In an EPS application, the magnetic saturation in thestator core and distortion of EMF is inevitable due tospatial and cost limitations(Lee, 2010). Imperfections of alow voltage inverter for EPS can be severe. This paper alsoanalyzes torque ripple caused by the motor, deadtimeeffects, and current offset problems of the PMSM driver.The harmonic current distribution is calculated using finiteelement analysis, and the effective dead time compensationmethod is proposed.
2. TORQUE RIPPLE OF PMSM2.1. Torque Ripple of PMSM for the EPSFigure 1 indicates a fabricated PMSM for the column typeEPS system. The rotor configuration was skewed to reducecogging torque. Segment type and ring type rotors are usedfor the purpose of this research. The specifications for aPMSM are listed in Table 1. Cogging torque and totalharmonic distortion (THD) of a back-EMF required in themotor are less than 0.02 Nm and 0.7% respectively. If therotor of a SPMSM is composed of segment-type permanentmagnets, there is relatively low THD in the back-EMF(0.7%). A ring-type magnet has a higher THD in the back-EMF (2.3%) and an acceptable level of productivity.The torque waveforms of segment and ring magnets areshown in Figure 2. In order to measure torque rippleaccurately, the motor is driven at 10 rpm, and input currentis controlled with a THD less than 0.5%. As the magnetictorque increases, the electric frequency increases by a*Corresponding author. e-mail: hongjp@hanyang.ac.kr