orque Ripple minimization technique in irect torque control inuction motor rive inoini Bhole At.Profeor, Electrical Department College of Engineering, Pune, INDIA vbb.elec@coep.ac.in B.N.Chauhari Profeor,Electrical Department College of Engineering, Pune, INDIA bnc.elec@coep.ac.in ArbinKumar Reearch Scientit D.R.D.O.Pune,INDIA arbinmani@gmail.com Abtract hi paper conier irect torque control trategie in inuction motor rive to minimize torque ripple. Spacevector moulation an moifie pace vector control concept i implemente to eign the controller. Baic DC metho uffer from torque ripple problem an witching frequency variation.[1] orque ripple are minimize uing pace vector moulation technique but execution time in three phae to two phae tranformation an reference voltage calculation require more, comparing with other metho by etermination of effective time vector. Sector an angle etermination an proceure of etermination of reference vector i eliminate in moifie Space vector moulation metho. Simulation tuie have been carrie out for three metho.baic DC reult in, change in flux, change in pee an change in loa are imulate in Matlab an compare with other two trategie on the ame platform.hi paper mainlyhighlight performance of the rive in ynamic torque an flux repone. Keywor Baic DC;SPWM;torque ripple I. INRODUCION Worlwie on inutrial, commercial platform, inuction motor are ue. Comparing with all pee control metho tator voltage variation metho i aopte univerally in which change in the magnitue of tator voltage, change the pee. Due to contant air gap flux requirement, along with magnitue of tator voltage upply frequency alo change to keep v/f ratio contant. ariable frequency i require to vary rotor pee a pee epen on ynchronou pee of rotating magnetic fiel. ariable magnitue of tator voltage i require to limit tator current a at low frequency impeance reuce an tator current increae. If pee control of lip ring inuction motor i coniere then external reitance are ae through lip ring. Aition of thee reitance introuce more copper lo an comparing with all metho it lea to one of the iavantage of lip ring inuction motor. Spee of inuction motor can be controlle by following control metho: Scalar Control: voltage / frequency (v/f ) i the baic, economical an imple control ue in mot of the inutrie. It i calle a calar a magnitue of tator voltage an frequency i varie to vary the pee. It iopen loop an le precie control a far a pee an torque variation i concerene.flux an torque are controlle inirectly. In calar control parameter are ientifie continuouly o the pee variation i to.5 % an ynamic repone i aroun 45 to 50 m. ector Control- It i cloe loop control an in thi control current an voltage are continuouly ene. It i avance control metho an worlwie accepte. It i precie an accurate pee an torque control. ue to complexity in computational algorithm it area i limite. Direct torque control- DC i an alternative avance pee control metho to vector control.due to implicity in algorithm an control it i popular. It performance i alo comparable with vector control. Spee control of inuction motor i poible in four quarant with help of DC. By imple control algorithm it poible to control flux an torque irectly with appropriate tator voltage vector. II.BASIC DC SCHEME Fig.1 how chematic of Baic DC,in which torque an flux are controlle irectly by election of inverter voltage pace vector from a look up table.[4] he electromagnetic torque can be expree in vector form a given in Eqn. (1)-(3) a: 3 ( ) λ an e 3 p L ( ) m e ' r L r L () herefore, magnitue of torque become 3 p L ( ) i n γ m e ' r L r L m e ' r r i (1) (3) 3 p L ( ) in L L + γ (4) Proceeing of the 1 t International an 16 th National Conference on Machine an Mechanim (inacomm013), II Roorkee, Inia, Dec 18-0 013 1014
Where γ i the angular iplacement of tator flux with repect to rotor flux. Due to high time contant, the rotor flux oe not change intantly an tator flux changeue to change in tator voltage, the correponing change of γ angle i γ,o the change in torque Eqn. (5) a : e expreion i given by 3 p L ( ) in L L γ m e ' r + r (5) In the controller torque error, flux error an tator flux poition i etimate uring each ampling perio an compare with reference value an from look up table elect expecte value of tator voltage among eight value an accoringly witching of inverter take place. Schematic of Baic DC i hown in Fig.1. Fig. : SM DC cheme with ector an angle etermination k + (6) I ( k p ) ( ) k I q ( k p + ) ( e e ) + ω (7) Anelectromagnetic torque i given by Eqn. (8) p 1. 5 i (8) e q Fig.1: Baic DC cheme FEAURES of BASICDC Inverter output voltage vector i only controlling parameter. ariation in tator flux are controlle by change in the tator voltage. Any change in the tator flux pace vector lea to change in the torque value. DISADANAGE ofbasicdc Hyterei ban control generate flux an torque ripple an witching from one tate to another i not mooth-lea to witching lo. II.SPACE ECOR DC SCHEME WIH SECOR AND ANGLE DEERMINAION Fig. how chematic of SM-DC of inuction motor. wo PI controller are implemente, one to control the flux an other for the torque. Stator flux error an torque error are ingle input to each of the controller. DQ component of reference voltage vector are the two correponing output of the PI controller. he roll of SM controller i to prouce three time ignal an next three voltage vector a an output of the inverter. PI controller i preent in the torque channel. [5] It control the torque value even if the etimation ha error in the lat term. he error in the magnitue of flux value i input of one PI controller prouce axi component of voltage vector.for each ampling perio, approximate the voltage will be given a: R i + / (9) R At high pee, the ignoring i voltage rop, voltage become proportional to change in flux an the Ri rop i witching frequency1/. At low pee the conierable. Calculation of voltage term require intantaneou pee an the magnitue of tator flux. he SM unit generate the inverter control ignal.[6] It receive reference voltage in a tator reference frame. he witching between two ajacent active voltage vector an zero vector uring one witching perio i the baic principle of SM technique. + q α a r c t a n + θ q Where θ i tator flux poition. (10) Proceeing of the 1 t International an 16 th National Conference on Machine an Mechanim (inacomm013), II Roorkee, Inia, Dec 18-0 013 1015
ADANAGES OF SPWM-DC SM-DC technique give ripple free operation for entire pee range. Improvement in flux, torque, pee repone. Repone i fat an controller i robut like BASIC DC Switching frequency i high an controllable. III MODIFIED SPACE ECOR DC SCHEME (Without angle an ector etermination) Fig.3: Moifie SM DC cheme without angle an ector etermination Fig no.3 i the block iagram of Moifie SMDC cheme without angle an ector etermination in which he q component of the reference vector are contructe by repective flux error component without PI regulator.[7] he proceure i a follow: R i + t (11) If reitance of tator wining i negligible, Eqn. (11) can be moifie a: t (1) If the time interval i mall, thi equation can be written a: t (13) Eqn. (13) can be re-written a + j ( + j ) t (14) q q Comparing real an imaginary part of Eqn. (14) give: t t (15) q t t q q q (16) t i equal to the ampling time. Hence q Where component of reference voltage vector ( + j q ) are etermine in a imple manner a given by Eqn. (15) an (16) without any reference frame tranformation. Spee of the reference flux pace vector i erive by aition of lip pee an actual rotor pee. he actual ynchronou pee of tator flux vector i calculate from machine moel. After each ampling interval, actual tator flux vector i correcte by the error an it trie to attain the reference flux vector. hu flux error i minimize in each ampling interval. he q component of reference voltage vector are tranforme to three phae reference voltage r, y, b which give voltage ignal for SM.[8] hee voltage can be converte to correponing three imaginary time r, y, b hee three imaginary time can generate reference voltage ignal. hee are following tep to fin three reference voltage vector:- Step 1: Calculate three phae voltage from q axi component of reference voltage vector.eqn.(17) r 1 3 + y q 1 3 b q (17) Step : calculate three imaginary time with repect to three reference voltage Eqn.(18) r b y r c y c b c x x x (18) From three time on r,y,b axe three correponing voltage are generate voltage an compare with the ymmetrical triangular wave to generate trigger pule for SM-INERER an correponing voltage i applie to Inuction Motor to prouce neceary torque. Proceeing of the 1 t International an 16 th National Conference on Machine an Mechanim (inacomm013), II Roorkee, Inia, Dec 18-0 013 1016
ADANAGES OF SM-DC SCHEME (without ector an angle etermination): Moifie SM-DC technique give ripple free operation for entire pee range. Improvement in flux, torque, pee repone. Repone i fat an controller i robut like BASIC DC. Calculation of angle an ector etermination i eliminate; it oe not require any reference frame tranformation. Le memory pace an computation time require. I SIMULAION RESULS he Inuction motor moel i imulate in Mat lab. Simulation tuie have been carrie out for SM-DC an Baic DC uing Matlab/Simulink oftware. Oe1 Euler metho with ampling time of 100µ i ue. Reference flux i 1.0 wb an pee i change from 750 rpm to 1350 rpm. Loa torque i zero in the flux variation an pee variation metho an loa i change from 0 to 10 Nm at 0.5 ec in loa variation metho. Performance point of view,baic DC, SM-DC (with ector an angle) an SM-DC (without ector an angle) are tuie in imulation. Stator flux ha been plotte a hown in Fig. 4(a)-(c) repectively for three cheme. Wherea change in loa torque ha been hown in Fig.5(a)-(c) repectively. Fig. 4 (a):dq Axi Stator Flux plot- Baic DC Fig. 4 (c):dq Axi Stator Flux plot- Moifie SM DC (without ector an Angle) Comparing with Baic DC an SM-DC(with ector an angle) flux plot, above flux plot i harp, without tarting tranient mean flux ripple are le with mooth tarting.. Change in the loa orque: Fig. 5 (a):baic DCChange in the loa from 0 to 10nm at 0.5 ec Fig. 5 (b):sm-dc(with ector an angle) Change in the loa from 0 to 10 nm at 0.5 ec Fig. 4 (b):dq Axi Stator Flux plot- Moifie SM DC (withectoran Angle) Fig. 5 (c):sm-dc(without ector an angle) Change in the loa from 0 to 10 nm at 0.5 ec Proceeing of the 1t International an 16th National Conference on Machine an Mechanim (inacomm013), II Roorkee, Inia, Dec 18-0 013 1017
Obervation (Baic DC): When loa i change from no loa to rate value, torque change to rate value with taring tranient with more ripple an 50 % variation from the rate value i oberve. Spee attain it rate value moothly. Ripple are oberve in tator flux. Nearly 0 % variation i oberve from reference value. Ripple are oberve in tator phae current a ripple in the tator flux. Obervation: When pee change take place from 750 to 1350 rpm,in the baic DC more torque ripple are oberve. orque variation i 50% In SM DC an Moifie SM DC( without ector an angle) torque ripple are almot reuce 7 to 8 % 4. Change in the tator flux from 1 to 0.7 wb Obervation(SM- DC with ector an angle): When loa i change from no loa to rate value, torque change to rate value with taring tranient an ripple are le an 10 % variation from bae torque value i oberve. Spee attain it bae value moothly. Ripple are le oberve in tator flux only 4%variation from the reference flux value. Ripple are le in tator phae current. SM-DC (with ector an angle) enhance performance of Inuction Motor rive with better complexity. Obervation:(SM-DC without ector an angle) When loa i change from no loa to rate value, torque change to rate value without taring tranient with le ripple.10 % variation from bae torque value. Spee attain it bae value moothly. Ripple are oberve in tator flux. 4% variation from reference value i oberve. Ripple are le in tator phae current. SM-DC(without ector an angle) enhance performance of Inuction Motor rive with le computational time. 3. Change in the pee: Fig. 8: Baic DC( change in flux) Obervation: When flux i reuce to 0.7mwb at 0.4 ec, baic DC cheme repon the change an torque ettle after 0.1 ec after the change. No change in the pee i oberve. Change in magnitue of tator current an ripple are oberve uring 0.4 ec to 0.5 ec. Similar repone i oberve for SM DC (With ector an angle) an SM-DC (without ector an angle) with le ripple in torque an tator current.. CONCLUSION Fig. 6:Change in the pee from750 RPM O 1350 rpm) Fig. 7 (a):baicdc Fig. 7 (b):sm DC (with ector an angle) Fig. 7 (c):sm DC (without ector an angle) orque ripple are le in SM-DC metho PI controller ue in SM-Controller improve performance in torque repone a proportional controller eliminate teay tate error an integral controller eliminate overhoot of the repone. Saturator are ue to keep voltage value within limit. While hyterei comparator ue in conventional metho prouce torque ripple a they accept any value of torque within the banwith choen.a banwith i more ripple are more an a banwith i le ue to high frequency witching. Smooth torque evelopment in SM-DC metho, at no loa conition when pee i varie from half to rate pee, torque i evelope moothly in SM-DC both metho. Proceeing of the 1 t International an 16 th National Conference on Machine an Mechanim (inacomm013), II Roorkee, Inia, Dec 18-0 013 1018
In SM-DC (without ector an angle metho) PI controller are not ue hence rie time i more than conventional an SM-DC(with ector an angle metho) Simulation reult of both SM-DC metho are ame but for without ector an angle metho le computation time i require than SM- DC with ector an angle a calculation of reference voltage, ector an angle are eliminate. A hown, the Fig.9 repreent the experimental etup in the machine laboratory on which experimental valiation i going on. Fig.9: Experimental et up REFERENCES [1] Peter a. Senor le vector an irect torque control, Oxfor Univerity Pre,Lonon,1998. [] N. Mohan Avance Electrical Drive, 001. [3] Boe B.K., Moern Power Electronic an AC Drive PEA, 00. [4].G.Habetler, Direct orque control of Inuction Machine Uing Space ector Moulation IEEE-IA,ol-8,199. [5] CritianLacu, Ion Bolea, A Moifie orque Control For Inuction Motor Senor le Drive. IEEE-IA,ol 36,000. [6] Project on Space vector PWM inverter by Jin-Woo-Jung [7] Arbinkumar,B.G.Fernane, Direct torque Control of hree phae Inuction motor Uing SPWM without Sector an angle Determination 11th International power Electronic an motion control conference,004. [8] Arbin Kumar, B.G.Fernane Simplifie SPWM-DC Of 3 Phae Inuction Motor Uing he Concept Of Imaginary Switching ime IEEE-IES,004. Proceeing of the 1 t International an 16 th National Conference on Machine an Mechanim (inacomm013), II Roorkee, Inia, Dec 18-0 013 1019