Flux Weakening Control for Stator-Doubly-Fed Doubly Salient Motor

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1 Page EVS25 Shezhe, Chia, Nov 5-9, 2010 Flux Weakeig Cotrol for Stator-Doubly-Fed Doubly Saliet Motor Mig Cheg, Yagag Shu School of Electrical Egieerig, Southeast Uiversity, Najig , Chia Phoe: Fax: Abstract To satisfy the demads of electric vehicles (EVs) of fast torque respose i wide rage of velocity, the priciple of flux weakeig of the stator-doubly-fed doubly saliet (SDFDS) motor which is desiged for EVs has bee studied ad aalyzed. Ad its advatage of regulatig the field flux idepedetly has bee fully utilized. The flux weakeig strategy is proposed ad high performace of SDFDS motor drive is acquired at high speed. Simulatio ad experimet are carried out based o Matlab/Simulik ad experimet platform. The simulatio ad experimetal results with good speed adjustig performace verify the effectiveess of the flux weakeig cotrol strategy of SDFDS motor drive. Keywords: Stator-Doubly-Fed doubly saliet motor, flux weakeig, speed cotrol, EVs 1 Itroductio As eergy crisis ad eviromet pollutio are icreasigly itesified over the world, the electric vehicles (EVs) become the competitive substitute for gasolie vehicles which cosume lots of oil ad exhaust emissios [1]. I order to eable EVs directly competig with gasolie vehicles, the aims of the EV motor drive are to pursue high efficiecy over wide speed rage, high power desity, high cotrollability, high reliability ad maiteace free operatio [2]-[6]. As so far, four types of motor drives have bee applied to EVs. They are brushed DC motor drives, iductio motor (IM) drives, PM sychroous or PM brushless motor drives, ad switched reluctace motor (SRM) drives [2]-[3]. As a ovel motor desiged for EVs, the stator-doubly-fed doubly saliet (SDFDS) motor [4]-[5], [7] has the feature of regulatig the field flux idepedetly ad effectively, which makes the implemetatios of the flux weakeig for expadig the speed rage ad o-lie efficiecy optimizatio easier tha other motors [8]-[9]. Fig.1 shows the cross-sectio of a 3-phase 12/8-pole SDFDS motor. The back electromagetic force (EMF) becomes so big whe the motor is at high speed that the flux has to be weakeed for speed icreasig. The rotor flux of iductio motor is i iverse proportio to speed for flux weakeig [10]. As for PM sychroous motors [11], the demagetizig curret i d is obtaied by flux-weakeig characteristics as a fuctio of the operatig speed. Prior agle cotrol is used for PM brushless motors to icreasig the motor speed [12]. Ad the coductio agle is adjusted for high speed ruig as to the switched reluctace motor [13]. The advatage of the SDFDS motor of regulatig the field flux idepedetly has bee fully utilized i this paper. The flux weakeig strategy is proposed ad high performace of the SDFDS motor drive is acquired at high speed. Both simulatio ad experimet are carried out. Good speed adjustig performace is achieved, verifyig the effectiveess of the flux weakeig cotrol system of the SDFDS motor drive. EVS25 World Battery,Hybrid ad Fuel Cell Electric Vehicle Symposium 1

2 Page Figure 1: Cross-sectio of the 12-8 pole SDFDS motor 2 Priciple Aalysis of Flux Weakeig Three phase full bridge circuit ad its coductio priciples used for the SDFDS motor drive is show i Fig. 2, where the piecewise liear iductace model is utilized so as to make it easy to aalyze the SDFDS motor drive. The voltage equatio of the SDFDS motor is show as follows: U = i R + e p p p bp = ir + e + e p p fp rp (1) where, ebp = efp + erp is the total back dlpf electromagetic force, efp = if ω is the dθ back electromagetic force of field excitatio, dlp erp = ip ω is the back electromagetic force dθ of reluctace; U p, i p, ad R p are phase voltage, phase curret ad widig resistace, respectively. L p, L pf,, ad i f are phase self-iductace of armature widig, mutual-iductace betwee armature widig ad field widig, ad field curret, respectively. Ad ω, ad θ are rotor agular velocity ad rotor positio agle, respectively. ψ ψ C ψ A ψ B a b c θ /( o ) i A θ /( o ) i B i C TT 5 6 TT 1 6 TT 1 2 TT 2 3 TT 3 4 TT 4 5TT 5 6 θ /( o ) θ /( o ) Ra e fa era Rb e fb erb Rc e fc e rc (a) Commutatig mode (b) three-phase full-bridge coverter Figure 2: Three phase full bridge circuit ad its coductio priciples EVS25 World Battery,Hybrid ad Fuel Cell Electric Vehicle Symposium 2

3 Page Accordig to the operatio priciples of the SDFDS motor, the electromagetic torque of phase p ( p =A, B, C) ca be expressed as: easily by regulatig the field curret compared to other motors. i f, as T ( θ, i) = T + T p rp fp 1 2 Lp = ip + i i 2 θ Lpf ipif θ p f L pf θ (2) 1 L 2 p where, Trp = ip is the reluctace 2 θ L pf torque; T fp = i pi f is the field torque. The θ field torque T is much larger tha the reluctace torque fp T rp, thus the electromagetic torque T ( θ, i) ca be simplified as T fp. p As the voltage equatio (1) showed, whe the speed rises, the back electromagetic force e icreases correspodigly. As the phase voltage of armature widig U is fixed, the armature curret p i p decreases, which makes the electromagetic torque T p reduce. Ad the mechaical movemet equatio of the SDFDS motor is: dω Te = J + Bω + Tl (3) dt where, T e is the total electromagetic torque, Te = TA + TB + TC, J is the rotatioal iertia, B is the frictio coefficiet ad T l is the load torque. Te Tl Accordig to (3), the motor speed ω = at B the steady state, amely the steady state motor speed depeds o the total electromagetic torque T e. Based o the above aalysis, the icrease of back electromagetic force makes the decrease i phase curret whe the motor works at high speed. Thus the total electromagetic torque T e miishes, which restrai the rise of motor speed. Hece, the motor flux has to be weakeed i order to exted the rage of speed. As for the SDFDS motor, the flux weakeig cotrol ca be attaied bp 3 Flux Weakeig Strategy for SDFDS Motor Fig.3 shows the simulated output torque characteristics versus field curret i f at the speeds of 2000,2500,3000 r/mi. It ca be see that as the field curret decreases, the output electromagetic torque first icreases ad the decreases. Thus the speed also first icreases ad the decreases whe the field curret decreases. Hece, the key of flux weakeig cotrol for the SDFDS motor is to get the field curret T e max I f at which the electromagetic torque reach the peak value. The the flux weakeig compoet I Δ is proportioal to electromagetic torque approximately whe the field curret T max I [ I e, I ]. The the covetioal PI f f fn regulator ca be used to realize flux weakeig for extedig the rage of speed. Based o the above aalysis, the flux weakeig cotrol strategy of the SDFDS motor ca be developed as follows: I. Whe the referece speed of motor ref is less tha or equal to the rated speed N, the stadard motor cotrol of regulatig the speed is adopted; II. Whe the referece speed of motor f ref is higher tha the rated speed N, the flux weakeig cotrol strategy is adopted for regulatig the speed: 1 Whe the feedback speed fb is less tha or equal to the rated speed N, the stadard motor cotrol of regulatig the speed is adopted; 2 Whe the feedback speed is higher tha the rated speed N, the flux weakeig cotrol strategy is adopted. The referece armature curret is set to be the omial value i pn, ad the flux weakeig compoet fb I Δ depeds o the output of speed PI regulator. The referece value of field curret is i = i fn I Δ, ad its EVS25 World Battery,Hybrid ad Fuel Cell Electric Vehicle Symposium 3

4 Page upper limit is I. I Δ T e max f ca be obtaied by Δ Δ i ( k) = i ( k 1) + k e ( k) + kδ e ( k) (4) p i The cotrol cofiguratio of flux weakeig cotrol strategy of the SDFDS motor drive at high speed is show i Fig =2000(r/mi) =2500(r/mi) =3000(r/mi) 2.5 Te (N.m) Field curret If (A) Figure 3: Curve of output torque ad field curret uder differet speed Yes ref N? No i = i ; fn i ( k) = i ( k 1) + k e ( k) + kδe ( k); pref pref p i Yes fb > N? No Δ Δ i ( k) = i ( k 1) + kpe( k) + kiδe( k); i = i i Δ ; fn i ; pref = ipn i ; = ifn i ; pref = ipmax Figure 4: Cotrol cofiguratio of flux weakeig cotrol strategy of SDFDS motor drive EVS25 World Battery,Hybrid ad Fuel Cell Electric Vehicle Symposium 4

Page000571 Figure 5: Simulatio model of flux weakeig cotrol of SDFDS motor drive at high speed 4 Simulatio I order to verify the effectiveess of the proposed flux weakeig cotrol scheme, a simulatio

6 uder the flux weakeig cotrol strategy. As illustrated i Fig. 6, the speed of SDFDS motor ca reach the referece value rapidly ad there is o steady speed error.

5 Page Figure 5: Simulatio model of flux weakeig cotrol of SDFDS motor drive at high speed 4 Simulatio I order to verify the effectiveess of the proposed flux weakeig cotrol scheme, a simulatio model is developed i Matlab/Simulik software, as show i Fig. 5. Whe the referece speed is 3000 r/mi at o load, the armature curret, field curret, ad step respose curve of speed are show i Fig. 6 uder the flux weakeig cotrol strategy. As illustrated i Fig. 6, the speed of SDFDS motor ca reach the referece value rapidly ad there is o steady speed error. The good speed adjustig performace is achieved whe the proposed field weakeig cotrol strategy is used. (a) Phase curret 5 Experimetal Results I order to further ivestigate the effectiveess of the proposed field weakeig cotrol strategy ad to verify the theoretical simulatio, a prototype of the SDFDS machie has bee desiged ad fabricated, as show i Fig. 7. The mai desig data of the prototype are listed i Table 1. The experimetal setup cosists of a 3-phase 12/8-pole SDFDS motor with its stator coected to a IGBT-based PWM coverter. A TMS320F2812 DSP based digital cotrol platform is desiged for implemetig efficiecy optimal algorithm. The block diagram of flux weakeig cotrol ad experimetal system are show i Fig. 8 ad Fig. 9, respectively. (b) Field curret (c) Speed Figure 6: Simulatio curves of flux weakeig cotrol EVS25 World Battery,Hybrid ad Fuel Cell Electric Vehicle Symposium 5

6 Page The experimets o the prototype machie were carried out at the same operatig poit as the simulatio. Comparig Fig. 10 with Fig.6 shows that the experimetal results agree with simulated results well, verifyig the effectiveess of the proposed scheme. Figure 7: Prototype machie i f i p ref e i pref u i θ Figure 8: Block diagram of flux weakeig cotrol of the SDFDS motor drive Figure 9: Schematic diagram of the SDFDS motor drive EVS25 World Battery,Hybrid ad Fuel Cell Electric Vehicle Symposium 6

Page000573 Table 1 Mai desig data of the prototype machie Items Parameter (a) Phase curret Rated power 750W Rated voltage 190V Reated field voltage 70V Rated phase curret 6A Rated field curret 1A

7 Page Table 1 Mai desig data of the prototype machie Items Parameter (a) Phase curret Rated power 750W Rated voltage 190V Reated field voltage 70V Rated phase curret 6A Rated field curret 1A Armature resistace/phase 0.62Ω Field widig resistace 19Ω Number of stator pole 12 Number of rotor pole 8 Number of phase 3 Rated torque 4.77Nm Rated speed 1500 r/mi 6 Coclusio (b) Field curret I this paper, the priciple of flux weakeig of the SDFDS motor has bee studied ad aalyzed. The flux weakeig strategy is proposed to satisfy the demads of fast torque respose i wide rage of velocity for EVs. Based o Matlab/Simulik ad experimet platform, simulatio ad experimets are carried out to realize the flux weakeig cotrol of the SDFDS motor drive at high speed. Ad good speed adjustig performace is achieved, which verify the effectiveess of the flux weakeig cotrol strategy for the SDFDS motor drive. Ackowledgemet This work was supported by the Key Techology R&D Program of Jiagsu Provice, Chia (No. BE ). (c) Speed Figure 10: Measured curve of flux weakeig cotrol Refereces [1] C.C. Cha, The State of the Art of Electric, Hybrid, ad Fuel Cell Vehicles, Proceedigs of the IEEE, 2007, Vol. 95, No. 4, 2007, pp EVS25 World Battery,Hybrid ad Fuel Cell Electric Vehicle Symposium 7

8 Page [2] X.D. Xue, K. Cheg, N.C. Cheug, Selectio of electric motor drives for electric vehicles, Australasia Uiversities Power Egieerig Coferece, Australasia, 2008, pp [3] G. Nada, N.C. Kar, A Survey ad Compariso of Characteristics of Motor Drives Used i Electric Vehicles, Electrical ad Computer Egieerig, CCECE '06, Caada, May 2006, pp [4] Mig Cheg, Yig Fa ad K.T. Chau, Desig ad aalysis of a ovel stator-doubly-fed doubly saliet motor for electric vehicles, Joural of Applied Physics, May 2005, Vol. 97, No. 10, May 2005, pp. 10Q [5] Yig Fa ad K.T. Chau, Desig, modelig ad aalysis of a brushless doubly-fed doubly-saliet machie for electric vehicles, Iteratioal Coferece o Electrical Machies ad Systems (ICEMS2005), 2005, Vol. I, pp [6] K.T. Chau, C.C. Cha, Liu Chuhua, Overview of permaet-maget brushless drives for electric ad hybrid electric vehicles, IEEE Trasactios o Idustrial Electroics, Vol. 55, No. 6, 2008, pp [7] Mig Cheg, Wei Hua, Jiazhog Zhag ad Wexiag Zhao, Overview of stator-permaet maget machies, IEEE Trasactios o Idustrial Electroics, November 2011, Vol. 58, No. 11, pp [8] Xiagxi Kog, Mig Cheg, Yagag Shu, Flux-weakeig cotrol of costat power of stator-doubly-fed doubly saliet motor for electric vehicles. Proceedigs of 11 th Iteratioal Coferece o Electrical Machies ad Systems (ICEMS2008), Oct , 2008, Wuha, Chia, pp [9] Xiaoyog Zhu, Mig Cheg, Desig, aalysis ad cotrol of hybrid excited doubly saliet stator-permaet-maget motor, Sciece Chia Tech Sci., Ja. 2010, Vol. 53, No. 1, pp [10] Hai-ya Liu, Yi Wag, Jie Liu, et al., Field-weakeig cotrol of iductio motor for electric vehicles, Electric Machies ad Cotrol, Vol. 9, No , pp [11] Ruzhe Dou, Xuhui We, Aalysis of field weakeig operatio for the direct torque cotrol of PMSM, Proceedigs of the CSEE, Vol. 25, No. 12, 2005, pp (i Chiese). [12] La Ya, Yikag He, Derog Yag, The approach of the flux weakeig operatio study for a BLDCM with hybrid rotor structure, Proceedigs of the CSEE, 2003, Vol. 23, No. 11, 2003, pp (i Chiese). [13] T. Humisto, P. Pillay, Flux weakeig operatio of switched reluctace motors, IEEE Power Egieerig Society Witer Meetig, 2001, vol.3, pp Author Prof. Mig Cheg School of Electrical Egieerig, Southeast Uiversity, Najig , Chia Tel: Fax: mcheg@seu.edu.c He received the B.Sc. ad M.Sc. degrees from the Departmet of Electrical Egieerig, Southeast Uiversity, Najig, Chia i 1982 ad 1987, respectively, ad Ph.D. degree from the Departmet of Electrical ad Electroic Egieerig, The Uiversity of Hog Kog, Hog Kog i His research iterests iclude electrical machies, motor drive for EVs ad reewable eergy techology. Yagag Shu School of Electrical Egieerig, Southeast Uiversity, Najig , Chia Tel: Fax: shuyagag@qq.com He received the B.Sc.(Eg.) ad M.Sc. (Eg.) degrees from the School of Electrical Egieerig, Southeast Uiversity, Najig, Chia, i 2007 ad 2010, respectively. His research iterests iclude motor drives ad motor cotrol EVS25 World Battery,Hybrid ad Fuel Cell Electric Vehicle Symposium 8

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