TORQUE RIPPLE MINIMIZATION IN FIELD ORIENTED CONTROL IN PERMANENT MAGNET SYNCHRONOUS MOTOR DRIVE

Transcription

1 TORQUE RIPPLE MINIMIZATION IN FIELD ORIENTED CONTROL IN PERMANENT MAGNET SYNCHRONOUS MOTOR DRIVE Thanu James 1, B.Adhavan 2, Dr. C.S.Ravchandran 3 PG Student [PED], Dept. of EEE, Sr Ramakrshna Engneerng College, Combatore, Tamlnadu, Inda 1 Assocate Professor, Dept. of EEE, Sr Ramakrshna Engneerng College, Combatore, Tamlnadu, Inda 2 Professor and Dean, Dept. of EEE, Sr Ramakrshna Engneerng College, Combatore, Tamlnadu, Inda 3 ABSTRACT: The Permanent Magnet Synchronous Motors are specal electrcal machnes whch can become a best replacement for Inducton motor n the near future. The constructon of the motor s smlar to the nducton motors where the stator s smlar to these motors and the rotor conssts of permanent magnets. A substantal ar gap s generated and produced wth the use of permanent magnets n the rotor for manufacturng hghly competent and effcent motor drve for automaton. The man dsadvantage seen n these types of motors are the producton of pulsaton torque whch ncreases the nose and vbraton of the motor drve thereby reduces the effcency of the drve. Ths paper dscusses about varous control technques to reduce the torque pulsatons n the motor by usng the conventonal controller and Fuzzy controller. The desgn and analyss of the varous systems s done n MATLAB 2010b and the comparson s studed to analyse the best technque for torque rpple mnmzaton n feld orented control n Permanent magnet synchronous motor drve. Keywords: Permanent magnet synchronous motor, Proportonal Integral Controller, Fuzzy Logc Controller, Space Vector Pulse Wdth modulaton I. INTRODUCTION The Permanent magnet synchronous motor (PMSM) are closely related to brushless DC (BLDC) motors whose feld exctaton s provded by permanent magnets and but has snusodal back EMF. Therefore they are consdered as a combnaton of both Inducton motors and BLDC motors as the stator constructon s smlar to Inducton motors. These drves are manly used n Ar condtoner and AC Refrgerator compressors, washng machnes, Automated Electrcal power steerng, Machne tools and Tracton control applcatons. These motors are wdely used n low and md power applcatons such as Computer perpheral equpment s, Robotcs, Adjustable speed drves and Electrc vehcles due to the advantages lke hgh effcency, hgh power factor, hgh power densty, compactness and mantenance free operaton. Also these motors are preferred over the tradtonal brushtype dc motors because of the absence of commutators, whch mnmzes mechancal wear and tear of the brushes and ncreases the lfe span of the motor. However, the man dsadvantage of PMSMs s the parastc torque pulsatons. The presence of these torque pulsatons results n nstantaneous torque that pulsates perodcally wth rotor poston. For the operatons wth reduced speed applcatons, these pulsatons are reflected as perodc pulsatons n the motor speed.there are varous sources of torque pulsatons n a PMSM such as the coggng, flux harmoncs, errors n current measurements, and phase unbalancng. In vew of the ncreasng popularty of PMSMs n ndustral applcatons, the suppresson of pulsatng torques has receved much attenton n recent years. Copyrght to IJAREEIE

2 Many technques based on both motor desgns and control technques have been proposed n lterature to dmnsh the torque rpples n the PMSM [8]. Nonlnear torque controller centered on flux/torque estmate s ntroduced to reduce the nfluence of the harmoncs of the flux. The effect of the coggng torque s mnmzed at lower motor speed usng nternal model prncple and adaptve feed forward compensaton technque. The dsadvantage s that the practcal mplementaton of the model requres addtonal work [7]. The torque rpples are parastc and can lead to torque pulsatons, vbratons and nose. These effects are analyzed and modeled usng the complex statevarable method. A fast current control system s produced to produce hghfrequency electromagnetc torque components for compensaton [6]. An embedded phase doman model s used to reducethe numercal nstabltes of the system. Both the conventonal and embedded phase doman model models are shown to provde dentcal results n the steady state and transent stuatons; however the conventonal model becomes unstable quckly f the tmestep s ncreased [5].An applcaton of ntellgence strategy lke fuzzy logc s used to reduce the torque rpples assocated wth drect torque control n PMSM [9]. II. FIELD ORIENTED CONTROL Feld orented control s an effcent method to control a PMSM n adjustable speed drve applcatons wth quckly changng load n a wde range of speeds ncludng hgh speeds where feld weakenng s requred. It demonstrates a synchronous motor to be controlled lke a separately excted dc motor by the orentaton of the stator mmf or current vector n relaton to the rotor flux. Feld orented control conssts of vectors to control the stator currents. Ths control s based on projectons whch transform a three phase tme and speed dependent system nto a two coordnate (d and q coordnates) tme nvarant system. These projectons lead to a structure analogous to that of a DC machne control. The feld orentated controlled machnes need two constants as nput references: the torque component (algned wth the q coordnate) and the flux component (algned wth d coordnate). Ths marks the control n every workng operaton (steady state and transent) and ndependent of the lmted bandwdth mathematcal model. Thus t solves the classc scheme problems, n the followng methods: 1. The ease of reachng constant reference (torque component and flux component of the stator current). 2. The ease of applyng drect torque control, because n the (d,q) reference frame the expresson of the torque s: T (1) R sq By mantanng the ampltude of the rotor flux (Ψ R ) at a constant value, we have a lnear connecton between torque and torque component ( sq ). We can then control the torque by controllng the torque component of stator current vector. The threephase voltages, currents and fluxes of ACmotors can be analysed n terms of complex vectors n space. Consderng that a, b, c are the stator phase currents, a b c 0 (2) Ths current space vector depcts the snusodal three phase system. It stll needs to be converted nto a two tme nvarant coordnate system. Ths transformaton can be dvded nto two steps: 1. (a,b,c) to (α,β) (the Clarke transformaton) whch outputs a two coordnate tme varant system. s a 1 2 s a b 3 3 (3) The nverse Clarke transformaton converts a 2phase (α,β) to a 3phase ( sa, sb, sc ) system. Copyrght to IJAREEIE

3 sa s sb s s 1 3 sc s s (4) (α,β) to (d,q) (the Park transformaton) whch outputs a two coordnate tme nvarant system. cos sn sd s s sn cos (5) sq s s where s the rotor flux poston. Inverse Park transformaton modfes the voltages n d,q rotatng reference frame n a two phase orthogonal system. Vs ref Vsdref cos Vsqref sn Vs ref Vsdref sn Vsqref cos (6) III.CONTROL TECHNIQUE I CONTROLLER WITH HYSTERESIS PULSE WIDTH MODULATION Proportonal and Integral () controllers were developed because of the desrable property that systems wth open loop transfer functons of type 1 or above have zero steady state error wth respect to a step nput. These controllers have constant parameter values whch nclude the Proportonal constant (K p) and Integral tme constant (K ). The general approach to tune controllers s to have hgh Integral gan. And then ncrease the proportonal constant to get satsfactory response. Start to add n ntegral tme constant untl the steady state error s removed. The block dagram of FOC n PMSM drve usng and Hysteress PWM s shown n the Fg. 1.The output waveform of the Control Technque I s shown n the Fg. 2 and the zoomed output response of torque s shown n the Fg. 3. Copyrght to IJAREEIE

4 AC supply Rectfer V dc _ Controller sdref = 0 _ sqref _ q d Park Inverse Transformaton Hysteress PWM Inverter Torque Estmator and Poston Sensng Theta Park Transformaton α β Clark Transformaton a b PMSM Shaft Fg. 1 Block dagram of FOC n PMSM usng and HPWM LOAD Fg. 2 Torque Response of FOC n PMSM drve usng controller and Hysteress PWM Fg. 3 Zoomed Torque Response of FOC n PMSM drve usng controller and Hysteress PWM Copyrght to IJAREEIE

5 Inference: Rated Torque=8 Nm Torque rpple (%) = (Peak to peak torque/ Average torque ) * 100 = ( )/8 *100 = 52.5% IV. CONTROL TECHNIQUE II FUZZY LOGIC CONTROLLER WITH HYSTERESIS PULSE WIDTH MODULATION The Fuzzy logc (FL) whch s one of the soft computng technques whch works on human ntellgence s defned as a multvalued logc whch deals wth dffcultes that have fuzzness or vague data.the fuzzy logc s a problemsolvng technque that provdes tself for mplementaton n systems rangng from smple, large, networked,embedded, acquston and control system problems. The man prncple behnd fuzzy logc approach s to mtate a human decson makng characterstcs to solve complex problems. The nputs to the controller are Torque error and change n Torque error and the output s torque lmt (T*) are descrbed n the Fg. 4, 5 and 6. The nputs and output contan membershp functons wth fve lngustc varables; namely HN Hgh Negatve, LN Less Negatve, ZE Zero, HP Hgh Postve, LP Less Postve and the rules for generatng the controller s shown n the Table 1. HN LN ZE LP HP 8 0 Fg. 4 Torque Error 8 HN LN ZE LP HP 1 0 Fg. 5 Change n Torque Error 1 HN LN ZE LP HP Fg. 6 Torque Lmt Copyrght to IJAREEIE

6 Table 1 Fuzzy Rules E HN LN ZE LP HP CE HP ZE LP HP HP HP LP LN ZE LP HP HP ZE HN LN ZE LP HP LN HN HN LN ZE LP HN HN HN HN LN ZE The block dagram of the Fuzzy controller wth HPWM n FOC of PMSM drve s descrbed n the Fg. 7.The output response of Torque wth Fuzzy logc controller and HPWM s shown n the Fg. 8 and the zoomed output response of the torque s also shown n the Fg. 9 to obtan the nference. AC supply Rectfer V dc _ Fuzzy Controller sdref = 0 _ sqref _ q d Park Inverse Transformaton Hysteress PWM Inverter Torque Estmator and Poston Sensng Theta Park Transformaton α β Clark Transformaton a b PMSM Shaft LOAD Fg. 7 Block dagram of the FLC wth HPWM n FOC of PMSM drve Fg. 8 Output Torque Response wth Fuzzy Controller and HPW M n FOC of PMSM drve Copyrght to IJAREEIE

7 Fg. 9 Zoomed Torque response wth Fuzzy Controller and HPW M n FOC of PMSM drve Inference: Rated Torque=8 Nm Torque rpple (%) = (Peak to peak torque/ Average torque) * 100 = ( )/8 *100 = % V.CONTROL TECHNIQUE III CONTROLLER WITH SPACE VECTOR PULSE WIDTH MODULATION From the lterature, t has been found that Space vector modulaton (SVM) s the most acceptable and wdely used pulse wdth modulaton technques as t elmnates the 3 rd order harmoncs to a greater extent. There are eght swtchng vectors namely from V 0, V 1, V 2, V 3 tll V 7 whch represent eght voltage structures. Here to properly dstrbute the voltages, they are provded wth two zero vectors (V 0 and V 7 ) and the rest 6 vectors are named as Actve vectors. Ths PWM technque estmates the reference voltage V ref by a combnaton of the swtchng patterns wth the eght vectors for the nverter n Table 2. The block dagram shows the controller wth the advanced control technque SVPWM n FOC of PMSM drve s shown n the Fg. 10. The output response of the torque s shown n the Fg. 11 and also the zoomed output response of the control technque III s explaned wth the nference n the Fg. 12. Table 2 Swtchng Patterns of SVM Vector A B C A B C V AB V BC V CA V 0 ={000} V 1 ={100} V dc 0 V dc V 2 ={110} V dc V dc V 3 ={010} V dc V dc 0 V 4 ={011} V dc 0 V dc V 5 ={001} V dc V dc V 6 ={101} V dc V dc 0 V 7 ={111} Copyrght to IJAREEIE

8 AC SUPPLY RECTIFIER T ref T m Controller sdref =0 sqref q d Park V a nverse transformaton Vb Space Vector PWM (SVPWM) V dc INVERTER theta q d Park transformaton a b Clark transformaton a b Torque and poston sensng PMSM SHAFT LOAD Fg. 10 Block dagram of controller wth SVPWM technque n FOC of PMSM drve Fg. 11 Output Torque Response of wth SVPWM technque n FOC of PMSM drve Fg. 12 Zoomed output Torque response of controller wth SVPWM n FOC of PMSM drve Copyrght to IJAREEIE

9 Inference: Rated Torque=8 Nm Torque rpple (%) = (Peak to peak Torque/ Average Torque ) * 100 = ( )/8 *100 = 1.675% VI. CONTROL TECHNIQUE IV FUZZY CONTROLLER WITH SPACE VECTOR PULSE WIDTH MODULATION Human experts mostly depend on common sense to solve challengng problems. Fuzzy logc (FL) s one of such ntellgent control technques whch solves problems usng human ntellgence. Fuzzy system conssts of manly three unts namely; fuzzfer, defuzzfer and an nference engne. The fuzzfer unt converts the crsp data nto fuzzy data. Ths fuzzy data wth the help of fuzzy rules s gven nto to the fuzzy nference engne. The engne evaluates the nput and produces approprate fuzzy output. Then the defuzzfer unt converts ths fuzzy nput nto human understandable crsp data. Fuzzy logc has found mportance due to the effcent behavour and they are manly used n Automaton applcatons. Here the block dagram of Fuzzy logc Controller wth SVPWM technque n FOC of PMSM drve s shown n the Fg. 13. The output Torque response of control technque IV s shown n the Fg. 14 and the zoomed output torque response s shown n Fg. 15 to obtan the nference of the technque. AC SUPPLY RECTIFIER T ref T m Fuzzy Logc Controller( FLC) sdref =0 sqref q d Park V a nverse transformaton Vb Space Vector PWM (SVPWM) V dc INVERTER theta q d Park transformaton a b Clark transformaton a b Torque and poston sensng PMSM SHAFT LOAD Fg. 13 Block dagram of FLC wth SVPWM n FOC of PMSM drve Copyrght to IJAREEIE

10 Fg. 14 Output Torque of FLC wth SVPWM n FOC of PMSM drve Fg. 15 Zoomed output Torque response of FLC wth SVPWM n FOC of PMSM drve Inference: Rated Torque=8 Nm Torque rpple (%) = (Peak to peak Torque/ Average Torque)* 100 = ( )/8 *100 = 1.536% VII.DISCUSSION It s clear that the varaton n Torque shown n Table 3 s less n case of Fuzzy logc controllers and they can acheve a mnmum torque rpple than other control technques. Table 3 Comparson of Varous Control Technques CONTROL TECHNIQUE TORQUE RIPPLE (%) Control Technque IV ( FLC SVPWM) Control Technque III ( SVPWM) Control Technque II (FLC HPWM) Control Technque I ( HPWM) 52.5 Copyrght to IJAREEIE

11 It has been vewed that the control strategy IV has helped n reducng the torque rpples from 52.5% to 1.536%. Thus by usng FLC based controller, rpples are reduced to a greater extent. VIII. CONCLUSION Fuzzy logc controller based Torque controller model of PMSM motor drve have been analysed and smulated usng MATLAB 2010b and the results have been presented to vsualze the comparson between varous control technques. The results obtaned from control technque IV demonstrate fast and satsfactory response wth load perturbaton. In future mplementaton, Hybrd Fuzzy controllers can be used n replacement to controller. ACKNOWLEDGEMENT I would lke to extend my earnest thanks and grattude to my project supervsor Prof. B. Adhavan for hs constant support and encouragement durng the course of my project. I m truly overwhelmed by hs honored gudance and nspraton from the begnnng to the end of ths project. REFERENCES [1]Adhavan.B,Kuppuswamy.A, Jayabaskaran.G and Jagannathan. V., Feld orented control of Permanent Magnet Synchronous Motor (PMSM) usng Fuzzy logc controller, n Proc. RAICS, 2011, pp [2]Baslo.J.C and Matos.S.R, Desgn of and D controllers wth transent performance specfcaton, IEEE Educaton, vol. 45, pp , Nov [3]Bmal.K.Bose, Modern Power Electroncs and AC Drves, PHI Learnng Prvate Lmted, [4] R. Krshnan, Permanent Magnet Synchronous and Brushless DC Motor Drves, CRC Press, [5]Dehkord.A.B, Gole.A.M and Magure.T.L, Permanent Magnet Synchronous Machne Model for Real Tme Smulaton, Int. Conf.IPST 05, 2005,Montreal, Canada. [6]Heydar. F, Shekholeslam. A, GorganFrouzjah.K and Ardeshr. G, Predctve Feld Orented Control of PMSM Usng Fuzzy Logc, Int. Conf. Power System, [7] Jahns.T.M andsoong.w.l, Pulsatng torque mnmzaton technques for permanent magnet AC motor drvesa revew, IEEE Trans. Ind. Elect., vol. 43, pp , Apr [8]Kovacc, Bogdan.S and Crnosja.P., Fuzzy Rule Based Model Reference Adaptve Control for PMSM Drves, Proc. IECON 93,1993, pp [9]L.N, We.X and Feng.X, An Improved DTC Algorthm for Reducng Torque Rpples of PMSM Based on Fuzzy Logc and SVM, IntConf Artfcal ICAIE 2010, 2010, pp [10] B.Adhavan, M.S. Brundha, Dr. C.S. Ravchandran and Dr. V. Jagannathan, Torque Rpple Reducton n Permanent Magnet Synchronous Motor usng Fuzzy logc control, Australan Journal of Basc and Appled Scences, vol. 7, pp , Copyrght to IJAREEIE