SIMULATION OF DIRECT TORQUE CONTROLLED PERMANENT MAGNET SYNCHRONOUS MOTOR DRIVE

Transcription

1 SIMULATION OF DIRECT TORQUE CONTROLLED PERMANENT MAGNET SYNCHRONOUS MOTOR DRIVE Selin Özçıra Nur Bekiroğlu Engin Ayçiçek Yiliz Technical Univerity, Department of Electrical Engineering, 449 Beikta, Itanbul, Turkey Key wor: Permanent magnet ynchronou motor, irect torque control, pace vector moulation ABSTRACT In thi tuy, the tructure an the control metho of permanent magnet ynchronou motor (PMSM) are analye an a imulation i realize uing conventional Direct Torque Control (DTC) metho. A a reult of thi analyi, it i oberve that the increae of the electromagnetic torque i irectly proportional to the increae of the angle between the tator an rotor magnetic flux linkage. I. INTRODUCTION Nowaay, a in every area of the technology, a evelopment proce ha been proceee in inutrial riving ytem. The improvement of the witching pee of the witching equipment ha enable control technique which have high witching frequency an feaibility of high efficiency riving ytem. Uing complex control algorithm ha become available with the evelopment in microproceor technology. The application of vector control for inuction an ynchronou motor can be given an example of thi. A a reult of evelopment of variou algorithm for ytem moelling an control application, inuction an ynchronou motor are being ue in application where DC motor were ue. However, inuction motor efficiency change with lip value, it nee reactive current, an not able to prouce the high torque / weight ratio which neee for high performance application uch a robotic, therefore ifferent olution are being tuie, an ifferent motor eign have been evelope. One of thee recently evelope motor i the permanent magnet ynchronou motor. In application where high performance i emane, ome propertie of the permanent magnet ynchronou motor uch a high torque, high power, high efficiency an low noie have mae it more popular compare to other alternating current motor [1]. Epecially becaue of the high power enity, permanent magnet ynchronou motor i applicable for area uch a robotic, automation an aeronautic technologie. Since the excitation flux i upplie by the magnet an ue to the magnet characteritic an location, permanent magnet ynchronou motor have both of a ynchronou machine an a irect current machine characteritic. Unloae conition, velocity i irectly proportional to voltage an inverely proportional to the flux an loae conition, it i irectly proportional to the current an flux. Synchronou motor have three phae wining in their tator, jut like the inuction motor. However, the rotor tructure i ifferent. By uing permanent magnet in tea of wining on the rotor, iavantage of the bruh an collector are eliminate. Alo, ince the excitation loe are eliminate, thermal limit are expane an higher power value can be obtaine from a machine of ame volume. Uing high energy permanent magnet uch a Sm Co 17 or N-Fe-B on the rotor, keep the air gap flux enity at higher value than of woune machine an eliminate the copper loe of the rotor wining, thu provie the higher efficiency compare to the inuction motor at ientical power value. Alo the motor imenion are conierably reuce []. Permanent magnet ynchronou motor i an AC motor that ha wining in the tator lot. The flux generate by tator current i almot inuoial. Therefore, the ame control metho ue for the inuction motor can alo be ue for the permanent magnet ynchronou motor []. Thee control are; V/f control, fiel oriente control, an irect torque control. The choice of irect torque control from thee metho give avantage uch a; fater torque control, high torque at low level pee an high pee enitivity. II. DIRECT TORQUE CONTROL (DTC) OF THE PERMANENT MAGNET SYNCHRONOUS MOTOR The torque of the permanent magnet ynchronou motor i controlle by inpecting the armature current ince electromagnetic torque i proportional to the armature current. For high ynamic performance, the current control i applie on rotor flux (q) reference ytem that i rotate at ynchronou pee. In thi ytem, if the change of the back electromotor force (emf) an the

2 inuctance are inuoial, armature circuit inuctance an magnet magnetic flux are contant. The main principle of DTC i to elect the appropriate voltage vector accoring to the tator magnetic flux, ifference between the reference an real torque. The current control circuit that i contitute with the pule with moulation (PWM) comparator circuit i not ue in DTC. Therefore, if the DTC metho i compare to PWM current control, it yiel avantage uch a; le parameter epenence an fat torque repone. If the initial poition of the rotor i known, it i poible to work with DTC without enor [4]. III. MOTOR EQUATIONS IN STATOR FLUX REFERENCE SYSTEM Stator magnetic flux vector ψ an rotor magnetic flux vector ψ M, can be repreente on rotor flux (q), tator flux (xy) reference ytem a hown in Figure 1. The angle between the tator an rotor magnetic fluxe δ, i the loa angle. δ i contant for a contant loa torque. In that cae both the tator an the rotor fluxe rotate at contant pee. However uner ifferent loa δ varie. Either the tator current rotation pee or the variation of δ i controlle in orer to control the increae of the torque. β y i q iy q i θ r δ i i x ψ M Figure 1. Stator an rotor magnetic fluxe in ifferent reference ytem ψ = Li +ψ M (1) ψ = L i () q q q u = Ri + ψ ωrψ q t () uq = Riq + ψ q +ωrψ t (4) Te = p( ψiq ψ qi) (5) Te = p Miq ( Lq L ) iiq ψ i obtaine [5]. The ymbol of parameter are a follow; ψ α x (6) ψ axi tator magnetic flux, ψ q axi tator magnetic flux, q ψ M rotor magnetic flux, L axi tator leakage inuctance, L q axi tator leakage inuctance, q R tator wining reitance, T e electromagnetic torque, p ouble pole number, Uing the tranformation in equation (7) an Figure 1, the expreion (8) are obtaine, uing (8), equation (6), can be tranforme into equation (9) F co δ in δ F x F = q in co F δ δ y Here F repreent the voltage, current an magnetic flux. Uing Figure 1; ψ in δ= ψ co q (7) (8) ψ δ= ψ i obtaine. The expreion ψ ; repreent the tator magnetic flux amplitue. When the neceary term are place uing Figure 1, the following equation i obtaine. Te = p ( ix in iy co ) q ( ix co iyin ) ψ δ+ δ ψ δ δ = p i + i i + i ψψq ψ ψ ψq ψq x y x y ψ ψ ψ ψ Te = p ψ iy (9) It i clear that electromagnetic torque i irectly proportional to the y-axi component of the tator current [6]. Controlling irectly y-axi component of the tator current provie appropriate election of the voltage witching vector. Depening on le parameter i the main avantage of tator current control. It i poible to ay that in a practical application the etimation technique hown in equation (6) require aturation-epenent inuctance. Therefore in equation (9) irect torque control over the tator current control i more convenient. IV. STATOR MAGNETIC FLUX CONTROL Torque can be controlle by keeping the tator magnetic flux contant an increaing the rotation pee. Stator

3 magnetic flux an pee control i realize uing the correct tator voltage vector. VOLTAGE SPACE VECTOR GENERATION The main principle of DTC i etermination of correct voltage vector uing the appropriate witching table. The etermination proce i bae on the torque an tator magnetic flux hyterei control. Stator magnetic flux can can be calculate uing equation (10) [7]. t+ t ( u ) ψ = R i t (10) t If the tator reitance i neglecte in Equation (10), tator magnetic flux can be expree irectly a the integral of the voltage pace vector. t+ t ψ = ut (11) t Equation (11) how that the tator magnetic flux an the voltage pace vector have the ame irection. Therefore, tator magnetic flux amplitue an irection control i feaible by uing the correct voltage pace vector. The voltage vector are etermine in orer to control the tator magnetic flux amplitue. Voltage vector plane i v 4 v v 5 v 4 4 θ θ 5 v v 5 v 6 v 6 θ 4 v4 θ1 v v5 6 θ θ 5 6 v v 6 Figure. Vector for pace vector moulation v v ivie into ix ection a hown in Figure. Two ajacent voltage vector that yiel the lowet witching frequency are electe in orer to increae or ecreae the amplitue of ψ. Here, when the tator magnetic flux i move clockwie in ection 1, voltage pace vector v i electe in orer to increae the tator magnetic flux amplitue an voltage pace vector i electe in orer to ecreae the amplitue. When the tator magnetic flux move clockwie, if till in ection 1, v 6 i ue to increae the amplitue an v 5 i ue to ecreae the amplitue. The torque of the permanent magnet ynchronou motor can be controlle uing DTC by mean of controlling the tator magnetic flux rotation pee in cae where the tator magnetic flux amplitue i kept contant. However, ince the magnet on the rotor are continuouly rotating, tator magnetic flux oe not change when v 0 an v 8 zero vector are ue. Therefore, zero vector are not ue in DTC for permanent magnet ynchronou motor [8]. V. MODEL VERIFICATION Here the MATLAB/Simulink moel of the permanent magnet ynchronou motor i evelope accoring to the q moel. In the imulation, the tator magnetic flux amplitue value i aume to be the ame a the value of the permanent magnet flux. Meaning that flux reference i applie a 0.5Wb. The inverter c bu voltage i 164.4V. Alo at t=0.0, a ifferential tep from Nm to -Nm an at t=0.09 from -Nm to Nm i applie to the referan torque value. Motor parameter are; p=, R = 5.8Ω, ψ M = 0.5Wb, L = 44.8mH, Lq = 10.7mH, J = kgm, Bm = Figure how the imulink iagram of the irect torque control for permanent magnet ynchronou motor. Figure. DTC imulink iagram of the PMSM

4 VI. SIMULATION RESULTS The ytem ynamic repone are hown below with a ampling time 100µ. Figure 7. Reference torque imulation repone Figure 4. Stator magnetic flux imulation repone Figure 8. Actual torque imulation repone Figure 5. Stator magnetic flux vector trajectory imulation Figure 9. Spee imulation repone Figure 6. Stator magnetic flux vector imulation repone

5 VII. CONCLUSION Motor criteria uch a urability, high performance, high power factor, eay an cheap control, low maintenance eman have le to a new type of motor excitate by permanent magnet. In thi tuy, control metho of permanent magnet ynchronou motor are analye an by mean of pace vector theory, irect torque control DTC metho i ue to control the motor. DTC i intene for an efficient control of the torque an flux without changing the motor parameter an loa. Alo the flux an torque can be irectly controlle with the inverter voltage vector in DTC. Two inepenent hyterei controller are ue in orer to atify the limit of the flux an torque. Thee are the tator flux an torque controller. In the performe imulation, certain tator flux an torque reference are compare to the value calculate in the river an error are en to the hyterei comparator. The output of the flux an torque comparator are ue in orer to etermine the appropriate voltage vector an tator flux pace vector. Vector location are hown in Figure 5. In thi tuy, DTC proce of the permanent magnet ynchronou motor i explaine an a imulation i contitute. It i conclue that DTC can be applie for the permanent magnet ynchronou motor an i reliable in a wie pee range. Epecially in application where high ynamic performance i emane DTC ha a great avantage over other control metho ue to it property of fat torque repone. In orer to increae the performance, control perio houl be electe a hort a poible. When the ampling interval i electe maller, it i poible to keep the banwith maller an to control the tator magnetic flux more accurately. Alo it i important for the enitivity to keep the DC voltage in certain limit. A a improvement approach, a LP filter can be ae to the imulation in orer to eliminate the harmonic. 4. Zhong, L., Rahman, M. F., Hu, W. Y., Lim, K. W., Analyi of Direct Torque Control in Permanet Magnet Synchronou Motor Drive, IEEE Tranaction on Power Electronic, pp , Tang, P., Yang, G., Luo, M., Li, T., A Current Control Scheme with Tracking Moe for PMSM Sytem, Sytem an Control in Aeropace an Atronautic 1t International Sympoium, pp , Luukko, J., Pyrhönen, J., Selection of the Flux Linkage Reference in a Direct Torque Controlle Permanent Magnet Synchronou Motor Drive, IEEE, in Proc. AMC 98-COIMBRA, pp , Rahman, M. F., Zhong, L., Haque, E., Selection of Voltage Switching Table for DTC Controlle Interior Permanent Magnet Motor, School of Electrical Engineering an Telecommunication, The Univerity of New South Wale, Syney, NSW 05 Autralia, Sun, D., Weizhong, F., Yikang, H., Stuy on the Direct Torque Control of Permanent Magnet Synchronou Motor Drive, Electrical Machine an Sytem, ICEMS 001. Proceeing of the Fifth International Conference, pp , SIMULINK Dynamic Sytem Simulation for MATLAB Moeling, Simulation, Implementation, The MathWork, Inc. Natick, Maachuett, USA, REFERENCES 1. Laurent, J., Jabbar, M. A.,Qinghua, L., Optimization of the Contant Power Spee Range of a Saturate Permanent-Magnet Synchronou Motor, IEEE Tranaction on In. App., Vol.4, No.4, pp , Texa Intrument, Digital Signal Proceing Solution for Permanent Magnet Synchronou Motor, Application Note Literature Number: BPRA044, pp. 11-1, Bizot, C., Brotte, J., Lungeanu, M., Poulen, B., Séra, D., Sørenen, M. B., Senorle Control for PMSM, Power Electronic an Drive, Intitute of Energy Technology, Aalborg Univerity, Denmark, 00.