A Novel Start-Up Scheme of Stator Flux Oriented Vector Controlled Induction Motor Drive Without Torque Jerk

Transcription

1 A Novel Start-Up Scheme of Stator Flux Oriented Vector Controlled nduction Motor Drive Without Torque Jerk Tae-Won Chun, Meong-Kyu Choi * Bimal K. Boe Dept. of Electrical Engineering, Univerity Mu-Gu-Dong, Nam-Gu, Ulan, (Zip-code : ), KOREA twchun@uou.ulan. ac.kr of Ulan * Dept. of Electrical Engineering, Univerity of Tenneee 419 Ferri Hall, Knoxville, TN , U.S.A. bboe@utk.edu Abtract - The paper propoe a novel zero peed tart-up cheme of a tator flux oriented vector-controlled induction motor drive without any torque jerk. A programmable 3-tage low pa falter (LPF) method i ued for flux etimation. However, the torque jerk hould be generated at the tranition dne to the time delay of tator flux caued by 3-tage LPF. At tandtill conditiow a method i derived to calculate a tator flux with only tator current. A feedforward control trategy of the tator flux i uggeted to prevent the torque jerk during the tranition from tandtill mode to the vector control mode. Through experimental reult with 32-bit DSP, the performance of the tart-up cheme i verified.. NTRODUCTON Recently, tator flux oriented vector controlled induction motor drive ytem i receiving wide attention in the literature [1]. The advantage of tator flux orientation i that it ha le influence on parameter variation effect. The etimation of tator flux i only enitive to the tator reitance variation which i eay to compenate. For the tator flux oriented vector control, the tator flux can be eaily calculated from the machine terminal voltage and current a follow. tart the induction motor with indirect vector control and then witched to direct vector control when the motor peed begin to develop. But the implementation of thi method i difficult and alo large torque jump may occur during tranition. n thi paper, the tandtill equation for etimating the tator flux at a zero peed are derived with current model of induction motor. The tator flux build up to rated tator flux with the tandtill equation, and then the drive tranition to the tator flux oriented vector control mode a the motor peed begin to develop. But the torque jerk hould be generated at the tranition due to the time delay of tator flux caued by 3-tage LPF. n order to prevent the torque jerk at the tranition, the feedforward control of tator flux i uggeted, which compenate for the time delay of tator flux.. DESCRPTON OF CONTROL STSTEM Fig. 1 how the block diagram for a tator flux oriented vector controlled induction motor drive ytem with the tart-up cheme. The baic method for etimating the flux i by pure integration, in which the voltage meaured noie, integration drift and parameter detuning effect can poe ignificant problem, epecially at low frequency. To overcome the problem, ome method have been uggeted. The enor of voltage and current are calibrated every time the ytem i tarted [2]. A low-pa filter i ubtituted for the pure integral, where the gain of filter i adjuted with tator frequency [3,4]. But the method uggeted by the above paper are inufficient to olve the problem. A programmable 3-tage low pa filter (LPF) method propoed at paper [5] i ued for flux etimation in thi tudy. Although the programmable 3-tage LPF get ideal integration at any frequency, there are two problem. One problem i that the drive i not elf-tarting, and the another problem i that the LPF caue time delay of tator flux at tranient condition, epecially at low frequency. The paper [6] ha propoed to W. Standtill Equation v; V;k ~ u k, / ~ n ib rrogrammarue #. < 3- tage >V f.,. COe d, Q Fig. 1 Block diagram of tator flux oriented vector control ytem with tart-up cheme. H X/01/$10.00 (C) 2001 EEE 148

2 The torque control and tator flux control are ued in the outer loop. n the tandtill (SS) mode, tator flux ignal are obtained from the tandtill equation and the tator flux etablihe to the rated value before applying the torque command. When the ynchronou peed CO. reache a threhold value (& a motor peed begin to develop, the drive i witched to the tator flux oriented vector control (SVC) mode, where the programmable 3-tage LPF i ued for tator flux etimation. And alo, a the machine top (zero peed) in SVC mode, the operation i witched back to SS mode. At tranition from SS mode to SVC mode, ome torque jerk may be generated if there are ome mimatching with two mode during the tranition. The magnitude of tator flux, ynchronou peed and angle, torque are calculated with tator flux and tator current at 2-axi tationary reference fi-ame.. STANDSTLL MODE OF NDUCTON MOTOR The induction motor i tarted with current model of induction machine, and the tandtill equation from current model will be derived to build up the tator flux to the rated flux at a zero peed. From the rotor voltage equation at 2-axi tationary reference frame, the d- and q- axi rotor flux linkage can be obtained a follow. ( where TV= RF/ L, : rotor time contant) The tator and rotor flux linkage are expreed a The tator flux linkage can be expreed in term of the rotor flux linkage and tator current a follow. (where LO = (L,L, - L~)/L,.) Through from (7) to (1 O), d- and q-axi tator flux can be calculated with only tator current. V. PROGRAMMABLE 3-STAGE CASCADED LPF The programmable 3-tage LPF i ued to calculate tator flux in tator flux oriented vector control ytem [5], and Fig.2 how the block diagram for implementing programmable 3- tage LPF. (lo) -. + R.ij, -4 Ez E,: ~-($~ E,; ~-($~ LPF1 z-$~ LPF1 z-()~ ~d_ol vq%_ol LPF2 1-$ ~ LPF2 +($d ~d-02 VQL02 LPF3.+ LPF3 Z-@d ~d_03 vm_03 G, G, % v:, Fig. 2 Block diagram for implementing programmable 3-tage LPF. A the machine i at tandtill, after ubtituting co, = O into (1) and (2), the rotor flux linkage can be expreed a tator current. (7) A the LPF perform integration of a inuoidal ignal, the output ignal of LPF lag phae 90 with attenuating a l/a& The ignal voltage behind the tator reitance drop are integrated within the cacaded low-pa filter etimation block. Thi block eentially conit of three identical programmable low-pa filter with the phae hift ((T/2) - r$a)/ 3 per tage at any frequency, where q+ i the phae hift of the analog hardware filter. The time contant of 3-tage LPF, and the compenation gain (G3) i programmable a a fnnction of frequency o a to get ideal integration at any frequency. The frequency dependent phae lag (+ with time contant Tk for the analog hardware filter are (8) (11) 149

3 become the output of LPF3, and the output of LPF2 lead The time contant T and phae hift ~d for each programmable LPF are expreed a =;tan[+oh}] ~d = -+~ -3 tan- (me, (12) (13) phae r#dwith multiplying ~- with repect of output of LPF3, and alo the output of LPF 1 lead phae 2@dwith multiplying 7 [1+ ( roe)] with repect of output of LPF3. The three output of LPF are aigned to the initial value of each LPF in the feedforward control, and Fig.3 and Fig.4 how,where ynchronou peed (D. can be calculated with tator current and voltage, and tator flux [2]. waveform for v:, and y:, and initial value of k.tage LPF repectively. At the programmable 3-tage LPF hown in Fig.2, the output of each LPF lag phae ~d and attenuate a 1/~- with repect of the input of each LPF, The compenation gain G, can be derived a G, =+k+(wzl[l+(ubj T e (14) V. FEEDFORWAED CONTROL OF STATOR FLUX When the drive i tranitioned to SVC mode, firtly the initial value of 3-tage LPF are determined with d- and q-axi tator flux calculated in SS mode, and then the programmable 3-tage LPF i applied to calculate the tator flux. The programmable 3-tage LPF give compenation for frequency dependent phae hift and gain by the hardware filter, and o it get ideal integration at any frequency. However, the programmable 3-tage LPF caue the time delay of tator flux at the tranient condition, and o the tator flux decreae rapidly at the tranition to SVC mode, and then the tator flux reduction generate ome jerk of motor torque at the tart-up. The feedforward control of tator flux i uggeted to compenate for time delay of tator flux, and o it prevent the torque jerk at the tranition to SVC mode. f the difference between the reference (rated) tator flux and the actual tator flux i greater than the tolerant limit (E) at tranient tate, the tator flux etablihe to reference tator flux by adjuting the initial value of 3-tage LPF. At the feedforward control of tator flux, the three initial value of LPF in Fig.2 are calculated in the revere direction from reference tator flux v:. Firtly, d-axi and q-axi tator flux can be written a Fig. 3 Waveform for & and initial value of LPF am *M & [Deg] Fig. 4 Waveform for ~~, and initial value of LPF. The initial value of d-axi tator flux LPF can be derived repectively. * ~d_03 = ~ = $Coee (17) A the output of each LPF are derived in revere direction from the d- and q- axi tator flux hown in (15) and (16), the input of LPF hould be obtained from the output of previou LPF, The tator flux divided by the correction gain G, 150

4 Correpondingly, the initial value of q-axi tator flux LPF can be derived repectively. SS Mode 1. SVC Mode o 4.* vq.02 = %+@e)2sin(@.+@d) ~ (20) (21) Yg 0.4 Y ~/min(oe+2#3d) Yq.ol ~ (22) V. SMULSON AND EXPERMENTAL RESULTS A. Simulation reult Digital imulation i carried out to verify the performance of the feedforward control of tator flux. Fig.5 and Fig.6 how the tart-up repone without and with the feedforward control of tator flux repectively. n the SS mode, d-axi tator flux build up to rated tator flux, while the q-axi tator flux remain O. When the tator flux etablihe to rated flux, torque command i applied. A the ynchronou peed reache a threhold value (at =5 rad/), the drive i witched to SVC mode. A hown in Fig.5, at the intant of tranitioning to SVC mode, the tator flux decreae o rapidly due to the time delay of tator flux, and then increae lowly to rated flux. A the tator flux decreae o rapidly, the torque jerk i generated during the tranition. A hown in Fig.6, the tator flux i kept contant with the feed forward control, and o there i no torque jerk during tranitioning to SVC mode. SS Mode L SVC Mode 9 1 ] ~ 4; 0, 300 [Del ,9 1,2 1,5 B. Experimental Reult Time [ee] Fig. 6 Start-up repone with feedforward control. Fig.7 how the block diagram of hardware configuration Torque D ~ F] AD 12-bit Cent rol Sytem DSP TMS320C30 L, *, Fig. 7 Sytem hardware configuration The current regulated PWM GBT inverter and 3 HP induction motor are available for experiment. The parameter of induction motor are given in Table. 1. Table 1. Parameter of induction motor ee 45: 300 [DL%l! Time [ee] Fig. 5 Start-up repone without feedforward control. Stator reitance R = [Q] Rotor reitance Rr = [Q] Stator inductance L = 83.9 [mh] Rotor inductance Lr = 85.3 [mh] Mutual inductance Lm = 81.4 [mh] Moment of inertia J = [Kgm2] Pole P=4 151

5 The control ytem i implemented with 32-bit TMS320C30 operating with a clock frequency of 33MHz and the ampling interval i 200w for peed and tator flux control. A pace voltage algorithm i ued for maximum utilization of dc link voltage, The dc link voltage, tator voltage and tator current are ened by iolation device and 12-bit A/D converter. The dc motor driven by de-to-de converter i ued for controlling the load torque of induction motor Fig.8 how experimental reult for tator flux and current at SS mode. The d-axi tator flux build up to rated flux (0.39 Wb.) by d-axi tator current while q-axi tator flux and current remain 0, After 0.5ec, the d-axi tator flux reache the rated flux. i& 00. i~, r 00 J h n r T!me (0.2 ldw ) (a) d-q axi tator current [ 1 A/dw] Time (0.5 kiiv.) (a) torque [1.5 Nm/div], tator flux [0.065 Wb/div], ynchronou peed [25 radl /div] t,,, ). ~q 0.0 r / f & #- k 1 1! NT) J Time (0.5 /div.) (b) d-& q-axi tator flux [0.13 Wb/div] Y;, Fig. 9 Start-up repone without feedforward control h Time (0.2 /div.) (b) d-q axi tator flux [0.13 Wb/div] Fig. 8 Stator current and flux repone at SS mode. Fig.9 and Fig. 10 how the experimental reult without and with the feedforward control of tator flux repectively at the torque command of 8 N.m, A hown in Fig.9, at the intant of tranitioning to SVC mode a the ynchronou peed reache a threhold value (5 rad/), the tator flux decreae o rapidly and then the torque jerk i generated. A hown in Fig. 10, the tator flux remain contant with the feedforward control, and o induction motor tart moothly without torque jerk during the tranitioning to SVC mode. 152

6 contant for etimating tator flux i ued to olve the problem y: of integration at low peed. n order to prevent the torque jerk 0.0 at the tranition, the feedforward control of tator flux i uggeted, which compenate for time delay of tator flux at tranient tate. t wa hown that the induction motor tart 1 1! 1 moothly without torque [.- ierk through both imulation and y$ experimental reult, 0.0 REFERENCES L Time (0.5 ktiv.) (b) d-& q-axi tator flux [0.13 Wb/div] Fig. 10 Start-up repone with feedforward V. CONCLUSON control. n thi paper, a novel tart-up cheme for tator flux oriented vector controlled induction motor drive i preented, where ac machine tart at zero peed in the SS mode, and tranition to vector control mode a the peed begin to develop. At a zero peed, the method to calculate the tator flux with only tator current i derived. The 3-tage LPF with programmable time [1] Xingyi Xu, Rik De Doncker, and D.W.Novotny, A tator flux oriented induction machine drive, Conf. Rec. of PESC, 1988, pp [2] Xingyi Xu, and D. W.Novotny, mplementation of direct tatnr flux orientation control on a veratile DSP baed ytem, EEE Tran. on nd. AppL, VOL27, No.4, July/Aug., 1991, PP [3] K. H.Hurt, T.G.Habetler, G. Griva, and F.Profumo, Zero-peed tacho-le LM. torque control : imple a matter of tatnr voltage integration, Conf. Rec. of EEE-APEC, 1997, pp [4] M.R.Zolghadri, C.Pelion, and D. Roge, Strt up of global direct torque control ytem, Conf. Rec. of PESC, 1996, pp [5] B. K.Boe, and N. R.Patel, A programmable cacaded low-pa filter baed flux ynthei for a tator flux oriented vector controlled induction motor drive, EEE Tran. On nd. Elec., VOL44, No. 1, Feb., 1997, pp [6] B.K,Boe, M.G,Simoe, D. R. Creceliu, K.Rajaahekara, and R.Martin, Speed enorle hybrid vector controlled induction motor drive, EEE- AS Annual Meeting, 1995, pp