A Comparative Analysis of Different MRAS Schemes for Speed Sensorless Induction Motor Drives Employing PI and Fuzzy Controllers

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1 A Compaative Analysis of Diffeent MRAS Schemes fo Speed Sensoless Induction Moto Dives Employing PI and Fuzzy Contolles M.Ankaao 1, M.Vijaya Kuma 2, K.Tija 3 1 Ph.D. Reseach Schola, Depatment of Electical and Electonics Engineeing, JNTUA, Anathapuamu, Andha Padesh, India. 2 Pofesso, Depatment ofelectical and Electonics Engineeing, JNTUA, Anathapuamu, Andha Padesh, India. 3 Student, Depatment of Electical and Electonics Engineeing, JNTUA, Anathapuamu, Andha Padesh, India. Abstact MRAS speed estimatos ae becoming moe popula ove the yeas because of thei high accuacy and flexibility in estimating speed of Induction moto dive without speed sensos to be mounted on the shaft. This pape consides thee MRAS configuations they ae Roto flux, Back-Emf and Reactive powe based methods. The pefomance of these MRAS schemes is analyzed fo vaiations in toque.the effectiveness of MRAS is analyzed fo vaious speed anges. Reactive powe based MRAS is poven to have the fastest esponse of the emaining two MRAS schemes intems of fast settling time and it has vey good esponse at high speeds as well. These estimatos ae then meged with an Indiect field oiented contol and caefully tested on simulation. Also a compaison is caied out between the thee MRAS schemes using both PI and FUZZY logic contolle. Keywods: Induction moto dives (IMD), Indiect field oiented contol(ifoc),sensoless speed contol, Speed estimatos, MRAS, Roto Flux, Instantaneous Reactive Powe, Back EMF, Fuzzy Logic Contol(FLC) MRAS BASED SPEED ESTIMATORS The basic MRAS stuctue is shown in the fig 2.1.the stuctue has two models one is efeence model (RM) and the othe is adjustable model (AM). An adaptive mechanism is pesent. The eo fom RM and AM is fed to the adaptive mechanism.the paametes in the RM ae fixed and the paamete values in AM ae vaied based on eo between efeence and adjustable model values so that the eo between two models becomes zeo. The thee MRAS schemes ae explained as follows. INTRODUCTION The adjustable speed dives (ASDs) withimds ae making significant effects in loadsbecause of obustness, effective pefomance and ugged stuctue. Theyae globally used in vaious industial applications as taction locomotives,electic vehicles, and electic populsionships. The vecto contol o FOC of an IMD wokslike a sepaately excited DC moto [2].The FOC method suffeswith few dawbacks, such as; it equies,cuent contolles,co-odinate tansfomations, andissensitive to vaiations in paametes. These FOC schemedawbacks ae educedwith a new contol stategy intoduced by Toshihiko andisao Takahashi which is named as IFOC scheme [3]. The DFOC of an IMD equie the oto shaft angula position infomation which is measued using speed sensos mounted on oto shaft. The speed sensousage is encounteed with fewdawbacks. Those dawbacks have made speed senso less IFOC dive vey attactive ove thedfoc dive. The popula MRAS techniques ae: Back-emf [7], oto-flux [8], eactivepowe [9]. OF all the thee MRAS schemes Reactive powe gives fast esponse and good pefomance at all speeds. Figue 2.1.Basic stuctue of MRAS A)Roto flux based MRAS speed estimation: Hee in this scheme the output of both AM and RM is intems of oto flux. The following equations fom Eq. no (1) to (5) ae used in the modeling of oto flux based MRAS speed estimation. a) Refeence model: Ψ s q s Ψ d = L [ (V s L qs R s i s qs σl s i s qs ) ](1) m = L [ (V s s L ds R s i ds σl s i s ds ) ](2) m Wheeσ = 1 L2 m L s L b) Adjustable model: 13898

2 s dψ q s dψ d = 1 T Ψ s q = 1 T Ψ s d c) Adaptive mechanism: + ω Ψ s d ω Ψ s q ω = {K P + K I P } (Φ qφ d Φ d φ q)(5) + 1 s T i qs (3) + 1 s T i ds (4) Figue 2.3Stuctue of Back emf base MRAS Speed estimato Figue 2.2Stuctue of Roto flux MRAS based Speed estimato B) Back Emf based MRAS speed estimation: Hee in this scheme output of both AM and RM is induced Emf. The following equations fom eq.no(6) to (12) ae used in the modeling of Emf based MRAS speed estimation. a) Refeence model: e md = V s ds {R s i s ds e mq = V s qs {R s i s qs b)adjustable model: + σl s i s ds }(6) + σl s i s qs } (7) e md = ( L2 m ) ( di md )(8) L e mq = ( L2 m ) ( di mq ) (9) Whee di md di mq L = ω i mq 1 T i md + 1 s T i ds (10) = ω i mq 1 T i md + 1 s T i ds (11) c) Adaptive mechanism: C)Reactive powe based MRAS speed estimation: Hee in this scheme output of RM is instantaneous eactive powe and output of AM is steady state eactive powe. Eo between the two eactive powes is fed to the pi integal contol and the oto speed is estimated. The following equations fom Eq. no (13) to (16) ae used in the modeling of eactive powe based MRAS speed estimation. a) Refeence model: The diect measuement of pe phase eactive powe can be done by using pak s tansfomation fom the teminals of the moto. Q = 1 (V as i cs V cs i as )(13) 3 b) Adjustable model: The equation fo steady state eactive powe is given by the following equation. Q = 1 (V as i cs V cs i as ) (14) 3 The ight hand side solution of the above equation is expessed in the stationay efeence fame as follows: s i s qs Q = ( 1 T ) ( L m L ) (Ψ d ω L m L (Ψ s d i s qs c) Adaptive mechanism: Ψ s q i s ds ) + + Ψ s q i s ds ) + σl s (i ds s i s qs i s qs i s ds )(15) ω = {K P + K I P } (Q Q) (16) ω = {K P + K I P } (e m e m ) (12) 13899

3 Table I: Rule Matix fo FLC Figue 2.4.Stuctue of Reactive powe based MRAS Speed estimato MRAS BASED SPEED OBSERVER USING FUZZYLOGIC ADAPTATION MECHANISM The FLC is a nonlinea, adaptive contol appoach and itoffes ugged pefomance unde sudden change in speed andload distubances.flc has seveal advantages ove othe contolles they ae it is vey obust and can be easily modified and it can use fo multiple inputs and multiple outputs finally it is vey cheape and quick to implement. The FLC can handle complicated nonlinea system which has a degee of uncetainty and also does notequie pecise mathematical modeling and paametes unlike constant gain in PI contolle, which makes the contolle suitable fo theimd [10]. a.design of Fuzzy Rule Base The FLC tansfes a linguistic contol appoach into anautomatic contol appoach, and fuzzy ule bases ae designedby an expeienced knowledge. The FLC ule base designinvolves designing ules which elates the input vaiables to the output model popeties [8, 10]. The poposed FLC adaptation mechanism, which is designed to estimate the otospeed while the IMD is in opeating condition. The eosignal between the RM and the AM is used to detemine theoto speed estimation though a FLC adaptationmechanism. The fuzzification stage input vaiables fo the oto speed estimations ae eo signal ξ ω and ate of change in eo signal ω Δξ and the output vaiable is the estimated oto speed ωˆ. The five fuzzy sets ae selected to convet the numeical vaiables into linguistic vaiables, which ae eviewed in Table 1. This membeship functions(m.f) ae samefo the two input vaiables and one output vaiable, which ae chaacteized using Mamdani max-min opeation type tiangula M.Fs is shown in Fig The FLC univese of discouse in between -1 to 1 is chosen fo the input and fo output vaiables. SIMULATION RESULTS An equivalent simulation model of each of the above speed obseves is built in Simulink and the dynamic pefomanceis obseved fo speed change and toque petubations.the simulation esults of the estimato models ae analyzed and compaed. (a) Roto Flux based MRAS estimato: Figue4.1.Compaison of estimated speed with PI and FLC Figue 3.1 The fuzzy input and output vaiables with nomalized tiangula wave foms

4 Figue 4.2.Iabc, Toque and Speed duing application of step toque of 10 Nm at 1.8 sec, N=150 pm High speed pefomance (N=900 pm): Figue 4.5.Iabc, Toque and Speed duing application of step toque of 10 Nm at 1.8 sec, N=150 pm High speed pefomance (N=900): Figue 4.3.Iabc, Toque and Speed at N= 900 pm (b) Back EMF based MRAS Estimato: Figue 4.6.Iabc, Toque and Speed at N=900 pm Figue4.4.compaision of estimated speed with PI and FLC 13901

5 (C)Reactive Powe Based MRAS estimato: Figue FLC based Reactive Powe-MRAS, Back -Emf MRAS, Roto Flux-MRAS Figue4.7Compaison of estimated speed with PI and FLC Roto esistance and stato esistance of IMD Figue 4.11Roto esistance of IMD duing application of step toque Figue4.8.Iabc, Toque and Speed duing application of step toqueof 10 Nm at 1.8 sec, N=150 pm High speed pefomance (N=900): Figue 4.12Stato esistance of IMD Figue 4.9.Iabc, Toque and Speed at N=900 pm CONCLUSION A method of estimating speed of the IMD with vaious MRAS schemes has been poposed and the vaiation in the paametes such as speed, cuent and oto esistance has been tacked with application of step toque.in view of speed estimation oto flux scheme eaches the highest estimated speed of148 pm which is neaest to the efeence speed 150 pm.even though oto flux has eached highest estimated speed but it has poo pefomance in view of ise time and settling time when compaed to eactive powe method.the 13902

6 analysis has poved the supeioity of the Reactive powe based MRAS speed estimato ove the othe two configuations intems of the tacking capability and paamete vaiations.a compaison table has made between thee MRAS schemes with both PI and FLC in tems of thei estimated speeds and settling times which is shown in the table below. Table 2. Compaison between thee MRAS schemes with PI and FLC. [7] Lin-Yu Lu, Tzu-Wei Yeh, Chia-Chi Chu, Back-EMF- BasedModel-Refeence Adaptive Sensoless Contol fo Gid-Connected DFIGs, IEEE /13, [8] Keyuan Huang, Ying Zhang, Shoudao Huang, Lei Xiao, AMRAS Method fo Sensoless Vecto Contol of Induction MotoBased on Instantaneous Reactive Powe, Hunan Univesity,Changsha, China. [9] F.Z.Peng, T.Fukao, Robust speed identification fo speedsensolessvecto contol of induction motos, IEEETansactions of Industy Applications, Vol.30, No.5, pp , Septembe/Octobe [10] Cao-Minh Ta, Toshyuki Uchida, Yoichi Hoi, MRASbasedSpeed Sensoless Contol fo Induction Moto Dives UsingInstantaneous Reactive Powe, The 27th Annual Confeence ofthe IEEE Industial Electonics Society, pp , 2001 REFERENCES [1] B.K. Bose, Moden Powe Electonics and AC Dives, NewDelhi, India: Pentice-Hall, 2006, ch. 8, pp [2] H.MadadiKojabadi, L.Chang, and R.Doiaswami, RecentPogess in Senso less Vecto-Contolled Induction MotoDives, Poceedings of the Lage Engineeing SystemsConfeence on Powe Engineeing, IEEE , pp , [3] V.Vema, M.J.Hossain, T.Saha, C.Chakaboty, Pefomance ofmras Based Speed Estimatos fo Gid Connected Doubly fedinduction Machines duing Voltage Dips, IEEE /12, [4] Teesa Olowska-Kowalska, Mateusz Dybkowski, Stato Cuent-Based MRAS Estimato fo a Wide Range Speed-Sensoless Induction-Moto Dive, IEEE Tansactions onindustial Electonics, Vol.57,No.4, pp , Apil [5] AbdelahamanYousifEshagLesan, MamadouLamineDoumbia,Piee Sicad, Compaative Study of Speed EstimationTechniques fo Sensoless Vecto Contol of InductionMachine, IEEE /12, pp , [6] Ahmad RazaniHaon, NikRumziNikIdis, Simulation ofmras-based Speed Sensoless Estimation of Induction MotoDives using MATLAB/SIMULINK, Fist Intenational Poweand Enegy Confeence, Putajaya, Malaysia, pp ,