R dt 2. INDIRECT FIELD ORIENTED CONTROL OF INDUCTION MOTOR

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1 Indiect Field Oiented Contol of Induction Moto Using Fuzzy Logic Aun Kuma R PG Schola, PED, SELECT, VIT Univesity, Chennai Campus aunkumalmc@gmail.com Abstact: This pape pesents a fuzzy logic based speed contol system fo a cuent souce PWM invete fed indiect field oiented contol of induction motos (IM). In this wok the conventional contolle is eplaced by fuzzy based intelligent contolle. The fuzzy logic contolle employs diffeent types of membeship functions fo each paamete fo the efficient contol of the ive system. The pefomance of the fuzzy based contolle is analyzed using a digital simulation in MATLAB/Simulink. The esults ae compaed with a conventional contolle. The fuzzy logic contolle gives bette esult. Keywods: - Fuzzy logic, intelligent contolles, field oiented contol, Induction Moto ives 1. INTRODUCTION Induction motos ae the most commonly used electic ives in the industies due to its obustness, less maintenance, and low cost. The electic ives must possess good dynamic esponse to espond to vey small changes in the load o in the efeence speeds. By using field oiented contol of induction motos this equiement is achieved easily. The induction moto is un like a sepaately excited DC moto using the field oiented contol. The advantages of the AC ives ove DC ives ae unalteed. Thus a ive system with a good dynamic esponse is developed. In conventional field oiented contol, a contolle is used to contol the speed of the induction moto ive. The use of contolle induces many poblems like high oveshoot, oscillation of speed and toque due to sudden changes in load and extenal distubances. This behavio of the contolle causes deteioation of ive pefomance. To ovecome this disadvantages an intelligent contolle based on fuzzy logic is employed in the place of the conventional contolle. The fuzzy logic based contolle has advantages ove contolle like simplicity in contol, and it can be designed without knowing exactly the mathematical model of the system to be contolled In this pape a fuzzy based contolle is used in field oiented contol of the induction moto ives 2. INDIRECT FIELD ORIENTED CONTROL OF INDUCTION MOTOR The indiect vecto contol method is essentially same as the diect vecto contol except the unit vecto is geneated in an indiect manne using the measued oto speed ω and the slip speed ω s1. The field oientation was made accoding to the oto flux vecto. The magnitude of the oto flux is obtained using a flux obseve, but the fequency of the oto field is neithe computed no estimated but it is imposed depending on the load toque value i.e. the slip fequency, and then integated to obtain the imposed oto flux position (angle λ ). A field weakening system is used to contol the speed of the moto when the speed ises above the nominal value. The mathematical model of induction moto is given by. θe = (1) The oto cicuit equation R Lm Ri ds sl q (2) dt L L q R Lm q Ri qs sl dt L L Fo decoupling contol, the stato flux component of cuent i ds should be aligned on the d e axis, and the toque component of cuent i qs should be on the q e axis, that leads to ψ q = and ψ = ψ then: L R dt m ds (3) Li (4) As well, the slip fequency can be calculated as: sl LR m i qs L (5) It is found that the ideal decoupling can be achieved if the above slip angula speed command is used fo making

2 the field oientation. The contol oto flux ψ and can be substituted in equation (2), so that oto flux set as (6) Li m ds The electomagnetic toque developed in the moto is given by Te 3 P Lm i 22L qs (7) The Simulink model of indiect vecto contol of induction moto is shown in figue 1. ce(t s ) = e(t s ) - e(t s -1) (9) Whee ce denotes the change of eo e, ω*(ts) is the efeence oto speed, ω(ts) is the actual speed, e(ts- 1)is the value of eo at pevious sampling time. The output vaiable is the change in toque ΔT which is integated to get the efeence toque as shown in the equation T * (t s ) = T * (t s -1) + ΔT (1) As shown in figue 3 of fuzzy logic contolle it has fou functional blocks Fuzzification, Intefeence mechanism, knowledge base and Defuzzification. ce ω* FUZZY CONTROLLER PWM INVERTER IM ω e Te I * qs Fig 2 Block diagam of fuzzy logic based contolle Fig 1 Simulation cicuit fo indiect vecto contol of induction moto 3. DESIGN OF FUZZY LOGIC CONTROLLER FOR INDUCTION MOTOR DRIVES The block diagam of fuzzy logic contolle is given in figue 2. The fist input is eo e and second is the change in eo ce at the sampling time t s. The two input vaiables ae calculated e(t s ) and ce(t s ) at evey sampling time as e(t s ) = ω * (t s ) ω(t s ) (8) Fig 3 functional block diagam of fuzzy logic contolle A. Fuzzification The cisp values of input paametes e(t s ) ans ce(t s ) ae fuzzified in this stage. The fuzzification maps the input vaiables to linguistic labels of fuzzy sets. Membeship function is associated with each label with tiangula shape which consists of two inputs and one output. The univese of discouse of all the input and output vaiables ae established as (-1, 1). The suitable scaling factos ae chosen to bought the input and output vaiables to this univese of discouse

3 The poposed contolle uses following linguistic labels NL, NM, NS, ZE, PS, PM, PL fo each of the inputs and an additional fou labels NLM, NMS, PMS, PLM fo the output membeship functions. B. Knowledge base and infeence mechanism Knowledge base involves defining the ules epesented as IF-THEN ules statements govening the elationship between input and output vaiables in tems of membeship function. In this stage the input vaiables e(t s ) and ce(t s ) ae pocessed by the infeence mechanism that executes 7*7 ules epesented in ule table shown. Consideing the fist ule, it is epesented as IF change in speed eo is NB and change in speed is NB, THEN the output will be NB. The Mamdani s algoithm fo geneating the infeence. Fig 5 Membeship function of input vaiable ce C. Defuzzification This stage intoduces diffeent methods that can be used to poduce fuzzy set value fo the output fuzzy vaiable ΔT. Hee the cente of gavity o centoid of aea(coa) method is used to calculate the final fuzzy value ΔT(t s ). Defuzzification using COA method means that cisp output of ΔT*(t s ) is obtained by using cente of gavity, in which the cisp output ΔT(t s ) vaiable is taken to be the geometic cente of the output fuzzy vaiables value μ out (ΔT)aea, whee μ out (ΔT) is fomed by taking the union of all the contibutions of ules with the degee of fulfilment geate than zeo. Then the COA expession with discetized univese of discouse can be witten as ΔT= Fig 6 Membeship function of output vaiable u * Then T e obtained by integation which is used to calculate i * qs. The membeship functions defined fo the input and output vaiables is shown in figue 4,5 and 6.The thee dimensional contol suface is shown in the figue 5. The ule base of the fuzzy contolle is given in the table 1. Fig 7 Thee dimensional plot of contol suface Fig 4 Membeship function of input vaiable e

4 Speed in ad/sec Speed in ad/sec Speed in ad/sec e & ce Table 1 Fuzzy ule base NL NM NS ZE PS PM PL 1 1 NL NL NL NLM NM NMS NS ZE NM NL NLM NM NMS NS ZE PS NS NLM NM NMS NS ZE PS PMS ZE NM NMS NS ZE PS PMS PM PS NMS NS ZE PS PMS PM PLM PM NS ZE PS PMS PM PLM PL PL ZE PS PMS PM PLM PL PL Time in sec Fig 6 No load esponse 7 4. SIMULATION RESULTS AND DISCUSSIONS The machine is initially at stand still with no load. The efeence speed is linealy inceased fom zeo to 1 ad/sec simulation wee caied out on both contolle and fuzzy logic contolle on the indiect vecto contol of induction moto Fig 6 shows the and with a command speed of 1 ad/sec applied with o load condition. The contolle shows an oveshoot and takes longe time to settle down at the nominal value. The shows a smooth esponse to the command speed and it settles down in small time duation Fig 7 and 8 shows the esponse of the induction moto to vaiable command speed applied to it unde no load condition. The contolle shows oveshoot in both esponses. The shows a smooth and fast esponse to the change in command speed. Fig 9 shows the esponse of the moto at loaded condition. The moto speed is set as 1 ad/sec and the load of 1 Nm is applied at.5 sec. The contolle esponse shows a huge decease in speed of the induction moto duing loaded condition. The has a low op in esponse compaed to the contolle Time in secs Fig 7 Two efeence speed esponse Response with load Time in secs Fig 8 Two efeence speed esponse

5 Speed in ad/sec [2] Biachi Naayan Ka, K B Mohanty, Indiect Vecto Contol of Induction Moto Using Fuzzy logic Contolle, IEEE 11 [3] Iulian Biou, Vigil Maie, Soin Pavel, Calin Rusu, Indiect Vecto Contol of an Induction Moto with Fuzzy Logic based Speed Contolle ; Advances in Electical and Compute Engineeing, Volume 1 Numbe 1, 1. [4] Tipua P, Sinivasa Kishoe Babu, Fuzzy Logic Speed Contol of Thee Phase Induction Moto Dive, Wold Academy of Science, Engineeing and Technology Time in sec Fig 9 Response when the moto is loaded 5. CONCLUSION The pefomance of the fuzzy logic based intelligent contolle fo the indiect vecto contol PWM cuent fed induction moto ive has been veified and compaed with that of conventional contolle pefomance. The simulation esults show that the designed fuzzy logic based intelligent contolle ealizes a good dynamic behavio of the moto to sudden changes with a apid settling time, no oveshoot and has a bette pefomance than contolle. The obustness of the fuzzy logic contol duing sudden changes in load has been seen. Machine details 6. APPENDIX Powe : 5HP Rated Speed : 1445 pm Rated Voltage : 415 V Fequency : 5 Hz Poles : 4 Rs : 7.34Ω Ls :.521H L :.521H Lm :.521H Inetia constant :.16 kgm 2 Viscous constant :.35 kgm/s [5] F BLASCHKE, The pinciple of field oientation as applied to the new tansvecto closed loop contol system fo otating field macine,siemens Rev, Vol.34,no.3 pp217-2, May [6] M Nasi Udin, Tawfik S Radwan and M Azizu Rahman, Pefomance of fuzzy logic Based indiect vecto contol fo induction moto ive IEEE Tans.Industy-Application,Vol.38,no.5,Septembe/Octobe 1 [7] Maiun N, Noo S B M, Jasmi J, Bennanes O S, Fuzzy logic based contolle fo an indiect contolle thee phase induction moto, TENCON 4 IEEE Region 1 Confeence,Publication Yea 4 [8] L.Zhen and L.Xu, Fuzzy leaning enhanced speed contol of an field-oiented induction machine ives, IEEE Tans.Contol System Technology, Vol-8, no-2,pp ,mach. [9] Biou, I.; Imecs, M.: Speed contol of induction moto ive with fuzzy-logic contolle, based on a DSP computing system. In Poceedings of the Intenational Symposium on Powe Electonics, Electical Dives, Automation and Motion SPEEDAM', Ischia, Italy, June 13-16,, pp. A1.19 A1.24. [1] Vinod Kuma, R. R. Joshi, Hybid Contolle based Intelligent Speed Contol of Induction Moto, Jounal of Theoetical and Applied Infomation Technology, Decembe 6, Vol. 3 No. 1, pp REFERENCES [1] Bimal K Bose, Moden Powe Electonics and AC Dives, Thid edition, INDIA: Peason Education, Inc., 7