ISSN: [Basnet* et al., 6(3): March, 2017] Impact Factor: 4.116

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1 IJESR INERNAIONAL JOURNAL OF ENGINEERING SCIENCES & RESEARCH ECHNOLOGY DIREC ORQUE CONROLLED INDUCION MOOR DRIVE FOR ORQUE RIPPLE REDUCION Bigyan Banet Department of Electrical Engineering, ribhuvan Univerity, Nepal DOI:.528/zenodo ABSRAC hi paper preent the performance analyi of direct torque control (DC) and DC baed pace vector modulation (SVM) technique controlled induction motor drive. DC drive utilize hyterei comparator and uffer from high torque ripple and variable witching frequency. While the SVM-DC reduce torque ripple preerving DC merit. SVM-DC calculate the required voltage vector to compenate the flux and torque error generating SVM for each ampling period. he imulation i performed uing PSIM and how the better performance of SVM-DC over baic DC. KEYWORDS: Direct torque control, induction motor, pace vector modulation INRODUCION he DC ha wider indutrial application due to everal feature i.e. quick torque repone and robutne againt motor parameter variation [-4]. Unlike, field oriented control (FOC), DC ha le complexity in it implementation due to non dependence of machine parameter. E.g. DC only ue the tator reitance to etimate the tator flux and torque [3]. In the baic conventional DC, flux and electromagnetic torque are controlled by electing optimum inverter witching tate. he DC cheme conit torque and flux hyterei band, withing table, flux and torque etimation block. Le parameter dependency make DC more robut and eay to implement. However, difficulty in controlling flux and torque at low peed, high ditortion in current and torque during ector alteration, variable witching frequency are ome diadvantage of DC. Alo higher torque ripple generate noie and vibration, cauing error in enorle drive. he reaon behind high torque and current ripple in DC i due to the preence of hyterei comparator and limited number of available voltage vector. he olution to minimize the torque ripple i uing SVPWM technique in DC cheme. Since, SVM techinque generate a reference tator voltage vector with a contant frequency at every ampling time, inverter produce a voltage vector in any direction of any magnitude, giving the mooth change in torque. DIREC ORQUE CONROL SCHEME Fig. how the block diagram of the baic DC cheme. A contant DC voltage i applied to the inverter. he output of inverter are connected to the induction motor. DC of induction motor i divided in three tep; orque and Flux Etimation he feedback flux and torque are calculated from the machine terminal voltage and current. hi etimation block alo calculate the ector number in which the flux vector lie. hree phae voltage and current are tranformed to tationary frame uing Clark tranformation a given below. i α= i a, i i 2i () a b 3 [25]

2 v α= v a, v va 2vb. 3 (2) w e w Ψ + - w r + - e Ψ Hyterei control Ψ H Ψ H Switching table θ orque and Flux Etimator a b c Inverter abc M Fig.. he block diagram of baic DC he flux and torque are calculated by tator current and voltage. he tator flux i given a v Ri dt. (3) v Ri dt. (4) he magnitude of tator flux i given a (5) 2 2 Sector number for flux vector i etimated by tan / (6) he electromagnetic torque can be calculated uing flux, current and number of pole..5p i i (7) e orque and Flux Control he reference and are compared with repective etimate value and error are proceed by hyterei band controller. he flux controller and torque controller are according to following, H = for e HB (8) H = - for e - HB (9) H = for e > + H = - for HB () > HB () H = for - HB < e > + HB (2) Switching table he witching election block a hown in Fig. receive the input ignal H, Hψ and θ, generate the deired control voltage vector a given in look-up table hown in able. [26]

3 able. Switching table of inverter voltage vector H ψ H I II III IV V VI v 2 v 3 v 4 v 5 v 6 v v v 7 v v 7 v v 7 v 6 v v 2 v 3 v 4 v 5 v 3 v 4 v 5 v 6 v v 2 v v v 7 v 7 v 7 v v 5 v 6 v v 2 v 3 v 4 Fig. 2 how the relationhip of inverter voltage vector and flux (ψ). Neglecting the tator reitance R of the machine, we can write d v ( ) dt v t Equation (3) how that the flux can be changed incrementally by applying tator voltage vector for an increment time. he flux can be increaed by the vector and it can be decreaed by the vector. Similarly, torque i increaed by the vector and decreaed by the vector. Meanwhile, zero vector hort circuit the machine terminal and keep the flux and torque unaltered. (3) 3 2 v3 v v4 Ɵ v w e v5 O v6 Fig. 2 Inverter Voltage vector and correponding tator flux variation SVM-DC SCHEME he block diagram of the SVM-DC cheme i hown in Fig. 3. Here the torque and flux etimator are ued to find the flux and the torque. Numeric calculation and controller are ued intead of witching table and hyterei controller. regulate flux and torque error giving reference voltage vector in d-q coordiante. And voltage vector in α-β coordinate are delivered to SVM block. Space Vector PWM (SVPWM) refer to a pecial technique of determining the witching equence of the upper three power tranitor of a three-phae voltage ource inverter (VSI). It ha been hown to generate le [27]

4 harmonic ditortion in the output voltage or current in the winding of the motor load. SVPWM provide more efficient ue of the dc bu voltage, incomparion with the direct inuoidal modulation technique. w e w Ψ e Ψ V d V q dq v α v β Inverter with SVM M θ Ψ orque and Flux Etimator abc w r Fig. 3. he block diagram of SVM-DC he dwell time calculation i achieved by volt-econd balancing equation, a v v v v (4) ref a 2 b For kth ector a b 3V a V d ref b in k 3 3 V ref ( k ) in Vd 3 SIMULAION RESULS he imulated reult for baic DC and SVM-DC are hown in Fig. 4. for the imilar peed reference. In both the cae the inuoidal tator current waveform i achieved. For no load cae, the DC cheme contain larger amount of torque ripple which i alo reflected in the current waveform. hi can be een in Fig. 4, that the ripple i reduced from.9 N-m to.5 N-m. Alo the flux trajectory i nice and mooth in the cae of SVM-DC cheme compared to baic DC. Since the flux i mooth, the torque calculated i alo moothed. hu, it i clear from the imulation reult, the torque and current ripple ha been reduced. Fig. 5. Show the imulated reult for the dynamic performance of the SVM-DC. Fat dynamic performance of the DC cheme i preerved giving mooth rotor peed repone. Unlike from the conventional DC, SVM-DC ue the flux angle to calculate rotor voltage. angle to calculate voltage reference for SVM i alo hown in the imulation reult. (5) [28]

5 I II Fig.4. Simulated reult with (I) Baic DC cheme (II) SVM-DC cheme with no load and peed reference 8 rpm: (a) three phae tator current, (b) torque ripple, (c) excitation reference frame flux trajectory Rotor Speed (a) Flux theta SVM Angle (b) Fig.5. Simulated reult with (a) Speed repone of peed reference 4-8 rpm (b) flux theta and SVPWM voltage angle. CONCLUSION hi paper ha reviewed the baic Direct orque Control cheme and SVPWM inverter fed DC for induction motor drive. SVM-DC operated by three-phae ac voltage with variable magnitude and frequency cheme improve the drive performance in term of reduced torque ripple and flux pulation. REFERENCES [] G. S. Buja and M. P. Kazmierkowki, "Direct torque control of PWM inverter-fed AC motor-a urvey," IEEE ran. Ind. Electron., vol. 5, no. 4, pp , Aug.24. [2] K. B. Lee and J. H. Song, "orque ripple reduction in DC of induction motor driven by three-level inverter with low witching frequency," IEEE ran.power Electron., vol. 7,, pp , Mar. 22. [3] D. Caadei, F. Profumo, G. Serra, and A. ani, "FOC and DC: wo viable cheme for induction motor torque control", IEEE ran. Power Electron.,vol.7, no. 5, pp , Sep. 22. [4] Y. Zhang and J. Zhu, "Direct torque control of permanent magnet ynchronou motor with reduced torque ripple and commutation frequency," IEEE ran. Power Electron., vol. 26, no., pp , Jan. 2. [29]