R. Linga Swamy and P. Satish Kumar

Transcription

1 Speed Control of Space Vector Modulated Inverter Driven Induction Motor R. Linga Swamy and P. Satih Kumar Abtract: In thi paper, v/f control of Induction motor i imulated for both open loop and cloed loop ytem. The induction motor (IM) i fed from three phae bridge inverter which i operated with pace vector modulation (SVM) Technique. Among the variou modulation trategie Space Vector Modulation Technique i the efficient one becaue it ha better pectral performance and output voltage i more cloed to inuoidal. The performance of SVM technique and Sine triangle pule width modulation (SPWM) technique are compared for harmonic, THD, dc bu utilization and Output voltage and oberved that SVM ha better performance. Thee technique when applied for peed control of Induction motor by v/f method for both open loop and cloed loop ytem it i oberved that the induction motor performance i improved with SVM. Index Term: Space vector modulation, SPWM, v/f control of Induction motor. I. ITRODUCTIO With the development in power electronic witche and low cot computational hardware ac induction motor drive now compare favorably to DC motor on conideration uch a power to weight ratio, acceleration performance, maintenance, operating environment, and higher operating peed without the mechanical commutator, cot and robutne of the machine, and perhap control flexibility are often reaon for chooing induction machine driver in mall to medium power range application. Up to date, due to the improvement of fat-witching power emiconductor device and machine control algorithm, more precie PWM (Pule Width Modulation) method find particularly growing interet. A large variety of method for PWM exit on which a urvey wa recently given. For the ac machine drive application, full utilization of the dc bu voltage i extremely important in order to achieve the maximum output torque under all operating condition. In thi apect, compared with any other PWM method for the voltage ource inverter, the PWM method baed on voltage pace vector reult in excellent dc bu utilization. Moreover a compared to ine triangle PWM method, the current ripple in teady tate operation can minimized in thi method. The peed or torque of an induction machine can be controlled by variou modulation trategie for inverter. In thi paper v/f control of IM for both open loop and cloed loop ytem uing the bet modulation trategy known a SVM technique i imulated and compared with the conventional SPWM technique and hown that IM performance i improved. With SVM the performance of IM i improved becaue it eliminate all the lower order harmonic in the output voltage of the inverter (tator voltage of the IM) when compared to the conventional SPWM technique. The performance of the IM can be further improved by eliminating the current harmonic in the tator current of the IM. II. SPACE VECTOR MODULATIO In Fig 1 the typical power tage of the three phae inverter and the equivalent circuit of a machine are preented. A hown in thi figure, the voltage applied to machine i defined a V an,bn,cn and the V a,b,c denote the pole voltage produced in the inverter tage in thi paper. And, the available eight different witching tate of the three phae inverter are depicted in the Fig 1. ote that all the machine terminal are connected to each other electrically and no effective voltage are applied to machine when the zero vector preented by Vo and V7 are elected. Manucript received December, 14, 2007.Thi reearch work wa upported by Electrical engineering Department, Univerity college of engineering, Omania Univerity, Hyderabad, Andhra Pradeh, India. R. Linga Swamy i with Electrical engineering Department, Univerity college of engineering, Omania Univerity, Hyderabad, A.P., India ( id: rlwamy@gmail.com). P. atih kumar i with Electrical engineering Department, Univerity college of engineering, Omania Univerity, Hyderabad, A.P., India ( id: atih_8020@yahoo.co.in). Fig.1. Three phae inverter fed induction motor

2 Fig.1. Switching tate diagram with Eight witching tate Therefore the ix voltage vector can be elected to apply an effective voltage to the machine and thee vector can be located on the vector pace repreented with the tator fixed d-q reference frame a hown in the fig 2. If a contant reference voltage vector V*or V ref i given in one ampling period, thi vector can be generated uing zero vector (V 0 or V 7 ) in combination with only two nearet active vector (V [n] and V [n+1] ). Thee two active vector are conidered a the effective vector to generate deired output voltage. From the average voltage concept, the reference vector can be written a following during one ampling period. V* = (T 1. Vn+ T 2. Vn+1)/T (1) ote that, in fact the effective time doen t imply the actual witching time. The witching time complie with the time delay from the initial point of one ampling period the activation time of witching device. Therefore in order to evaluate the active witching time, the effective time hould be recombined to the location of the reference vector. In fig 3, the relationhip between the effective time and the actual gating time i depicted when the reference vector i located in the Sector-1. In thi cae the V 1 vector i applied to the inverter during T 1 interval, and conequently V 2 vector i applied during T 2 interval. In the three phae ymmetry modulation method, the zero equence voltage vector i ditributed ymmetrically in one ampling period to reduce the current ripple. Thu, in general, the witching equence i given by within two ampling period. With the point of view of the upper witching device of one inverter leg, the former equence ( equence) i called O equence, and the latter ( ) i called OFF equence in thi paper. Therefore, the actual witching time correponding to the cae of ector -1 can be written a, On gating Sequence Off Gating Sequence T ga =T 0 /2 T ga = T 0 /2+T 1 +T 2 T gb =T 0 /2+T 2 T gb =T 0 /2+T (5) T gc =T 0 /2+T 1 +T 2 T gc =T 0 /2 (Where T 1, T 2 are the applied effective time correponding to the active vector.) And, the effective time can be deduced a, V *. T 3 in( π / 3 α) T1 = (2) V DC.2 / 3 in( π / 3) V *. T 3 in( α) T 2 = (3) V DC.2 / 3 in( π / 3) T 0 = T 3 -T 1 -T (4) Where T 0 i the time correponding to null vector V DC i the DC linkage Voltage and T 3 i ampling time Fig.2.Space vector diagram of the effective vector Fig.3. Actual gating ignal pattern of the pace vector PWM (in the cae of the ector -1) From thi analyi, the conventional pace vector modulation tak can be olved into following tep to make the actual PWM pattern. Step: 1) Sector Identification: By comparing the tationary frame d-q component of the reference voltage vector, the ector where the reference vector i located i identified. Step: 2) Calculating the Effective Timer: Uing the d-q component of reference vector and the DC link voltage information, the effective time T1, T2 are calculated. Step: 3) Determining the witching Time: uing the correponding ector information the actual witching time for each inverter leg i generated from the combination of the effective time and zero equence time.

3 III. MATHEMATICAL MODEL OF IDUCTIO MACHIE The induction machine i implemented in imulink uing the following mathematical model V qa =r i q + ωλ d + p λ q (6) V`qr = 0 = r`ri`qr +( ω ω ) λ `dr + p λ qr (7) r V d = r i d - ωλ q + p λ d (8) V`dr = 0 =r`r i`dr ( ω ωr ) λ `qr + p λ `dr (9) ω =angular peed of arbitrary reference frame P=d/dt Where λ q =(l +L m )i q + L m i`qr = L i q + L m i`qr (10) λ `qr =(l`r+l m )i`qr + L m i q =L`ri`qr + L m i q (11) λ d = (l +L m ) i d + L m i`dr =L i d + L m i`dr...(12) λ `dr =(l`r + L m )i`dr + L m i d =L`ri`dr + L m i d...(13) Therefore i i` i i` q qr d dr 1 L Lm 0 0 q ` 0 0 = Lm L r λ`qr - (14) 0 0 L L m λ d 0 0 Lm L`n λ`dr And Pm 3 P Lm T e = = [ λ`dr iq λ`qr id ] - (15) ωm 2 2 L`r Te TL ω m = J + B λ ; ω r = 2 P ω m (16) Fig.4. Phae voltage Van,Vbn,Vcn uing SPWM Torque developed, Speed (rpm), Flux b) Open loop SVM Fig.5a. how the output phae voltage of SVM inverter and Fig.5b how torque developed, peed and flux of IM with open loop control. It can be oberved that peed of the induction motor i increaed with SVM for ame D.C input voltage IV. SIMULATIO Simulation were carried out for contant v/f control of induction motor drive uing SVM and SPWM technique for open and cloed loop ytem. The parameter of the induction motor ued for imulation are a follow: 220V, 50Hz, 4pole, 3hp R =0.55Ω, L =93.38mH R r =0.78Ω, L r =93.36mH, Lm=90.5mH J=0.019KG-M 2, B= , T L =10.32-m; The inverter witching frequency i 2.1 khz the D.C link voltage i Vand the modulation index i 0.7 for both SVM and SPWM a) Open loop SPWM Fig.4a. how the output phae voltage of SPWM inverter and Fig.4b how torque developed, peed and flux of IM with open loop control. Fig.5. Phae Voltage Van,Vbn,Vcn uing SVM Torque developed, Speed (rpm), Flux

4 d) Cloe loop SVM Fig.6 & 7 how the Ref peed, actual peed, torque developed and flux for cloed loop control of SVM inverter fed IM. Fig.6. Ref Speed *, Actual Speed (rpm), Torque developed, Flux Fig.9. Ref Speed *, Actual Speed (rpm), Torque developed, Flux g) Cloed loop v/f control when the motor i decelerating e) Cloe loop SVM Fig.7 how the SIMULIK block diagram of cloed loop peed control of SVM Inverter fed IM. iga,igb,igc Van,Vbn,Vcn,vzn fr v 0 peed iga iga Van van f igb igb Vbn vbn Step -K- Gain * Saturation ( ) peed controller l SVM igc p/2/60 igc vdc IVERTER f Vcn Vzn Load torque Fig.7. Simulation block diagram of cloed loop SVM Tl vcn T l Te lam dr+qr IDUCTIO MOTOR *,,Te,flux Fig.10. Ref Speed *, Actual Speed (rpm), Torque developed, Flux h) Harmonic Spectrum Fig 11a & 11b how the harmonic pectrum of output phae voltage obtained uing Fat Fourier Tranform technique for SPWM and SVM inverter repectively. It can be oberved that all the lower order harmonic are reduced for SVM when compared to SPWM. f) Cloed loop v/f control when the motor i accelerating Fig. 9 &10 how ref peed, actual peed, torque developed and flux for cloed loop control of SVM inverter fed IM when motor i accelerating and decelerating repectively.

5 Fig.11. Harmonic Spectrum of Phae Voltage with SPWM Harmonic Spectrum of Phae Voltage with SVM i) Comparion table of SPWM and SVM Table-1 compare the variou performance detail of SPWM /SVM inverter fed IM. Input Dc voltage to inverter i BV. TABLE-1 Control Strategy R.M.S. Phae R.M.S. Line Fundame ntal Fundame ntal T H Speed (RPM) voltage Voltage Phae Voltage Line Voltage D SPWM SVM R.Linga Swamy obtained the B.Tech degree in Electrical and Electronic engineering from Gokaraju Rangaraju intitute of Engineering and Technology, Hyderabad in 2002 and the M.Tech degree in power electronic and drive from IT, Warangal in Preently he i working a an Aitant Profeor in department of electrical engineering, Univerity College of Engineering (Autonomou), Omania Univerity, Hyderabad, Andhra Pradeh, India. P. Satih Kumar obtained the B.Tech degree in electrical and electronic engineering from JTU College of Engineering, Kakinada, A.P., India in 1996 and the M.Tech degree in power electronic from JTU College of Engineering, Hyderabad in He worked in variou Private Engineering College in Andhra Pradeh for more than 11 year a Aociate Profeor in the Department of Electrical and Electronic Engineering. Preently he i Aitant Profeor in department of electrical engineering, Univerity College of Engineering (Autonomou), Omania Univerity, Hyderabad, Andhra Pradeh, India VI. COCLUSIOS Simulation of pace vector modulation (SVM) technique and inuoidal PWM (SPWM) technique ha been done uing MATLAB. The v/f control of Induction motor drive for both open loop and cloed loop ytem ha been imulated. The tranient behavior of the ame motor operated with fixed upply voltage and no feedback control i compared with the cloed loop control. It i oberved that SVM generate le harmonic ditortion in the output voltage and more efficient ue of upply voltage in comparion with SPWM and hence Motor performance i improved. REFERECES [1] Joohn-heok Kim, eung-ki ul A novel voltage Modulation Technique of the pace vector PWM, IPEC-Yokohama 95. [2] S.R.Bowe, ew inuoidal pule width modulation inverter, Proc.Int. Elect. Eng., vol. 122,pp ,1975. [3] K.Zhou, D. Wang Relationhi between Space Vector Modulation and three phae carrier-baed PWM: Acomprehenive analyi, IEEE Tran. Ind. Elec. Vol. 49,pp feb.2002 [4] D.C Lee.G-M.Lee, A ovel over modulation technique for pace vector PWM inverter, IEEE Tran [5] J.Holtz, Pule width modulation for electronic power converion, Proc.IEEE, vol.82,pp , Aug [6] J.Holtz, Pulewidth modulation-a Survey, in Proc. IEEE PESC 92,1992, pp