Direct torque control of dual star induction motor using a ...

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Direct torque control of dual star induction motor using a fuzzy-PSO hybrid approach Ghoulemallah Boukhalfa, Sebti Belkacem, Abdesselem Chikhi and Said Benaggoune Department of Electrical Engineering, Faculty of Technology, University of Batna2, Fesdis, Algeria Abstract This paper presents the particle swarm optimization (PSO) algorithm in conjuction with the fuzzy logic method in order to achieve an optimized tuning of a proportional integral derivative controller (PID) in the DTC control loops of dual star induction motor (DSIM). The fuzzy controller is insensitive to parametric variations, however, with the PSO-based optimization approach we obtain a judicious choice of the gains to make the system more robust. According to Matlab simulation, the results demonstrate that the hybrid DTC of DSIM improves the speed loop response, ensures the system stability, reduces the steady state error and enhances the rising time. Moreover, with this controller, the disturbances do not affect the motor performances. Keywords Dual stator induction motor (DSIM), Direct torque control (DTC), Speed control, particle swarm optimization (PSO), Fuzzy logic control (FLC) Paper type Review Article Nomenclature P Number of pole pairs J The moment of inertia f r The friction coefficient T em The electromagnetic torque T r The load torque Ω r is the mechanical rotation speed of the rotor R s1 ,R s2 Stators resistances R r Rotor resistance L s1 ,L s2 Stators inductances L r Rotor Inductance L m Mutual inductance n number of particles in the group d dimension index t pointer of iterations (generations) Direct torque control of dual star induction motor © Ghoulemallah Boukhalfa, Sebti Belkacem, Abdesselem Chikhi and Said Benaggoune. Published in Applied Computing and Informatics. Published by Emerald Publishing Limited. This article is published under the Creative Commons Attribution (CC BY 4.0) license. Anyone may reproduce, distribute, translate and create derivative works of this article (for both commercial and non-commercial purposes), subject to full attribution to the original publication and authors. The full terms of this license may be seen at http://creativecommons.org/licences/by/4.0/legalcode Publishers note: The publisher wishes to inform readers that the article Direct torque control of dual star induction motor using a fuzzy-PSO hybrid approachwas originally published by the previous publisher of Applied Computing and Informatics and the pagination of this article has been subsequently changed. There has been no change to the content of the article. This change was necessary for the journal to transition from the previous publisher to the new one. The publisher sincerely apologises for any inconvenience caused. To access and cite this article, please use Boukhalfa, G., Belkacem, S., Chikhi, A., Benaggoune, S. (2020), Direct torque control of dual star induction motor using a fuzzy-PSO hybrid approach, New England Journal of Entrepreneurship, Vol. ahead-of-print No. ahead-of-print. https://10.1016/j.aci.2018.09.001. The original publication date for this paper was 06/09/2018. The current issue and full text archive of this journal is available on Emerald Insight at: https://www.emerald.com/insight/2210-8327.htm Received 15 April 2018 Revised 19 August 2018 Accepted 2 September 2018 Applied Computing and Informatics Emerald Publishing Limited 2210-8327 DOI 10.1016/j.aci.2018.09.001

Transcript of Direct torque control of dual star induction motor using a ...

Direct torque control of dual starinduction motor using a fuzzy-PSO

hybrid approachGhoulemallah Boukhalfa, Sebti Belkacem, Abdesselem Chikhi and

Said BenaggouneDepartment of Electrical Engineering, Faculty of Technology, University of Batna2,

Fesdis, Algeria

AbstractThis paper presents the particle swarm optimization (PSO) algorithm in conjuctionwith the fuzzy logic methodin order to achieve an optimized tuning of a proportional integral derivative controller (PID) in the DTC controlloops of dual star inductionmotor (DSIM). The fuzzy controller is insensitive to parametric variations, however,with the PSO-based optimization approach we obtain a judicious choice of the gains to make the system morerobust. According to Matlab simulation, the results demonstrate that the hybrid DTC of DSIM improves thespeed loop response, ensures the system stability, reduces the steady state error and enhances the rising time.Moreover, with this controller, the disturbances do not affect the motor performances.

Keywords Dual stator induction motor (DSIM), Direct torque control (DTC), Speed control, particle swarm

optimization (PSO), Fuzzy logic control (FLC)

Paper type Review Article

NomenclatureP Number of pole pairsJ The moment of inertiafr The friction coefficientTem The electromagnetic

torqueTr The load torqueΩr is the mechanical

rotation speed ofthe rotor

Rs1, Rs2 Stators resistances

Rr Rotor resistanceLs1, Ls2 Stators inductancesLr Rotor InductanceLm Mutual inductancen number of particles in

the groupd dimension indext pointer of iterations

(generations)

Direct torquecontrol of dualstar induction

motor

© Ghoulemallah Boukhalfa, Sebti Belkacem, Abdesselem Chikhi and Said Benaggoune. Published inApplied Computing and Informatics. Published by Emerald Publishing Limited. This article is publishedunder the Creative Commons Attribution (CC BY 4.0) license. Anyone may reproduce, distribute,translate and create derivative works of this article (for both commercial and non-commercial purposes),subject to full attribution to the original publication and authors. The full terms of this license may beseen at http://creativecommons.org/licences/by/4.0/legalcode

Publishers note: The publisher wishes to inform readers that the article “Direct torque control ofdual star induction motor using a fuzzy-PSO hybrid approach” was originally published by theprevious publisher of Applied Computing and Informatics and the pagination of this article has beensubsequently changed. There has been no change to the content of the article. This change wasnecessary for the journal to transition from the previous publisher to the new one. The publishersincerely apologises for any inconvenience caused. To access and cite this article, please useBoukhalfa, G., Belkacem, S., Chikhi, A., Benaggoune, S. (2020), “Direct torque control of dual starinduction motor using a fuzzy-PSO hybrid approach”, New England Journal of Entrepreneurship, Vol.ahead-of-print No. ahead-of-print. https://10.1016/j.aci.2018.09.001. The original publication date forthis paper was 06/09/2018.

The current issue and full text archive of this journal is available on Emerald Insight at:

https://www.emerald.com/insight/2210-8327.htm

Received 15 April 2018Revised 19 August 2018

Accepted 2 September 2018

Applied Computing andInformatics

Emerald Publishing Limited2210-8327

DOI 10.1016/j.aci.2018.09.001

vti,m velocity of particle atiteration I

w inertia weight factorrand ( ) randomnumber between

0 and 1

pbesti best previous position ofthe ith particle

gbest best particle among allthe particles inthe population

C1,C2 acceleration constantsubscripts s, r indicate the variables

and parameters of

stators and rotor,respectively

subscripts 1, 2 denote variables andparameters of stator 1and 2 respectively

Vds1, Vqs1, Vds2, Vqs2 respectively statorvoltages in the d-q axis

Ids1, Iqs1, Ids2, Iqs2 components of the statorcurrents in the d - q axis

Idr, Iqr the rotor currentsψds1, ψqs1, ψds2, ψqs2 components of the stator

flux linkage vectors ind-q axis

ψdr, ψqr respectively rotor fluxes

1. IntroductionIn high-power applications, the dual star induction motor has largely replaced the inductionmachines whose roles were predominant in the industry [1–5]. The dual star induction motoris constituted of two windings with phases shifted from one another by an angle of 30electrical degrees. These windings are usually powered by a six-phase inverter fed byvariable speed drives. The main advantages of the DSIM are: [6] their higher torque density,reduced harmonic content of the DC link current and the reliability of this machine whichallows a functioning with one or several phases of defective motor. However the control ofDSIM is considered to be complicated because the difficulty of obtaining the decoupling of thetorque and the flux. To overcome these difficulties, high-performance algorithms have beendeveloped [7–14].

To satisfy the performance of an electromechanical system drive, the generally usedstrategy consists in controlling the speed by a PID controller to cancel the static error andreduce the response time. This speed is often characterized by an overshoot at startup anddepends on the parameters of the machine. In order to overcome these complications, severalmethods have been developed to adjust the PID regulator.

Auto-tuning is one of these methods, which is used in PID controllers [15]. Theperformance of the control loops is improved by automatically adjusting the PID gainparameters of the conventional controllers.

The self-tuning method has been suggested by many researchers [16,17]. A self-adjusting mechanism has been set up to adapt the PID regulator in case of anydisturbances.

The use of optimization algorithms as alternative methods for tuning PID controllershas been a recent topic of research in electric machines control. New optimizationtechniques are proposed, for instance, the Imperialist Competitive Algorithm (ICA) [18],evolutionary algorithm [19], Genetic Algorithm (GA) [20–21], BAT algorithm [22],Particle Swarm Optimization (PSO) [23–26], and Ant Colony Optimization (ACO)algorithm [27], Harmony Search (HS) [28], hybrid GA [29–30], adaptive Cuckoo Searchalgorithm (CS) [31].

PSO was first used by Eberhart and Kennedy in 1995 [32]. This approach isinspired by the social behavior shown by the natural species. In recent years, particleswarm optimization has appeared as a new and popular optimization algorithm dueto its simplicity and efficiency. The role of the PSO in this study is to suggest anadequate adjustment of the parameters (kp, Ki, Kd) to satisfy some drive systemrequirements.

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In last years, the FLC has improved results of nonlinear and complex processes [33]. Themain idea of this approach is that it does not need a precise mathematical model of the electricmachine, FLCs are robust and their performance is insensitive to parameter variations. Withthe increasing evolution of approximation theory, the adaptive control methods have beenpresented to cope with the nonlinear systems with parametric uncertainty based on fuzzylogic system (FLS) [34], neural networks (NNs) [35], adaptive fuzzy and NN controlapproaches via backstepping methods [36,37].

There are two disadvantages in the conception of a FLC. The first one is the obtaining of asuitable rule-base for the application, while the second is the selection of scaling factors priorto fuzzification and after defuzzification, in order to overwhelm these drawbacks andexpedite the determination of the design parameters and to reduce the time consumption.Several solutions are adapted to remedy these problems. In [38,39] the authors presents an online method for adapting the scaling factors of the FLC, the authors suggest a solution todesign an adaptive fuzzy controller. The objective of the proposed form is to adapt onlinescaling factors according to a performance measure in order to refine the controller andincrease the performance of the drive system.

In this paper, we investigate the performance of PSO for optimizing the gains of the fuzzy-PID speed controller of the DSIM.

2. Modeling of the dual star induction motorThe DSIM dynamic equations in the reference d-q can be reported as follow [4]:8>>>>>>>>>>>>>>>>>>>>>><

>>>>>>>>>>>>>>>>>>>>>>:

Vds1 ¼ Rs1ids1 þ d ψds1

dt� ωsψqs1

Vqs1 ¼ Rs1iqs1 þd ψqs1

dtþ ωsψds1

Vds2 ¼ Rs2ids2 þ d ψds2

dt� ωsψqs2

Vqs2 ¼ Rs2iqs2 þd ψqs2

dtþ ωsψds2

Vdr ¼ 0 ¼ Rridr þ d ψdr

dt� ðωs � ωrÞψqr

Vqr ¼ 0 ¼ Rriqr þd wqr

dtþ ðωs � ωrÞwdr

(1)

where the fluxes equations are:8>>>>>><>>>>>>:

ψds1 ¼ Ls1ids1 þ Lmðids1 þ ids2 þ idrÞψqs1 ¼ Ls1iqs1 þ Lmðiqs1 þ iqs2 þ iqrÞψds2 ¼ Ls2ids2 þ Lmðids1 þ ids2 þ idrÞψqs1 ¼ Ls1iqs1 þ Lmðiqs1 þ iqs2 þ iqrÞψdr ¼ Lridr þ Lmðids1 þ ids2 þ idrÞψqr ¼ Lriqr þ Lmðiqs1 þ iqs2 þ iqrÞ

(2)

For studying the dynamic behavior, the following equation of motion was added:

JdΩr

dt¼ Tem � Tr � frΩr (3)

Direct torquecontrol of dualstar induction

motor

The model of the DSIM has been completed by the expression of the electromagnetic torqueTem given below:

Tem ¼ pLm

Lm þ Lr

ðψdrðiqs1 þ iqs2Þ � ψqrðids1 þ ids2ÞÞ (4)

A schematic representation of the stator and rotor windings of dual star induction motor isgiven in Figure 1.

3. Direct torque control (DTC) of the DSIMThe classical DTC, proposed by [40], is based on the following algorithm:

– Divide the time domain into periods of reduced duration Ts;

– For each clock struck, measure the line currents and phase voltages of the DSIM;

– Reconstitute the components of the stator flux vector and estimate the electromagnetictorque, through the estimation of the stator flux vector and the measurement of theline current;

– The error between the estimated torque and the reference one is the input of a threelevel hysteresis comparator when this latter generates at its output the value ofþ1 toincrease the flux and 0 to reduce it and thus increasing the torque –1 it reduce this fluxand 0 to keep it constant in a band;

– The error between the estimated stator flux magnitudes is the input of a two levels ofthe hysteresis comparator, which generates at its output the valueþ1 to increase theflux and 0 to reduce it;

– Select the state of the switches to determine the operating sequences of the inverterusing the switching table. The input quantities are the stator flux sector and theoutputs of the two hysteresis comparators.

The block diagram of the DTC of DSIM is shown in Figure 2.

Vsb1Sb1

Sc2isc2Sc1

Sa2

Sb2

α=30°

θr

Ra

Rb

Rc

Vsa1

Vsa2 isa2isb1Vsb2

isb2

Vsc1isc1

Vsc2

ira

irb ircSa1

isa1

Figure 1.Schematicrepresentation of dualstar inductionmotor (DSIM).

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Moreover, Table 1 presents the sequences corresponding to the position of the stator fluxvector to the different sectors. The flux and the torque are controlled by two hysteresiscomparators at 2 and 3 levels, respectively, in the case of a two-level voltage inverter Table 5.

The expression of the stator flux is described by:

ψ sα1:2 ¼Z t

0

ðVsα1;2 � Rsisα1;2Þdt

ψ sβ1:2 ¼Z t

0

ðVsβ1;2 � Rsisβ1;2Þdt(5)

where Vsα1;2 and Vsβ1;2 are the estimated components of the stator vector voltage. They areexpressed from the model of the inverter.

4. Particle swarm optimization algorithmPSO uses a population of individuals to discovery the high solution in a search area amongthe neighboring solutions. The individual is defined by a particle, which displacesstochastically in the guidance of its preceding finest position and the best past location ofthe swarm.

Presume that the size of the swarm is n and the search area ism , next the position of the ithparticle is given as xi5(xi1, xi2,. . ... . . ,xid). The finest previous positions of the ith particle areconsidering by [32]:

cflx ccpl 1 2 3 4 5 6 Corrector

0 1 V2 V3 V4 V5 V6 V1 2 levels0 V7 V0 V7 V0 V7 V0

�1 V6 V1 V2 V3 V4 V5 3 levels1 1 V3 V4 V5 V6 V1 V2 2 levels

0 V0 V7 V0 V7 V0 V7

�1 V5 V6 V1 V2 V3 V4 3 levels

Speed

sensor

3

3

(a,b,c,1)ss

Flux and Torque Estimation

ˆ s

s

DSIM Switching

Table (ccpl)

1

0 +

- (cflx) sref

+-

Inverter2

s

( , ,1,2)sI

sψ̂ˆ( , ,1,2)s

(a,b,c,2)ss

Inverter1

Vdc

( , ,1,2)sV

a,b,c

refΩ

r

+ -

PID Controller

1 2 3

4 5 6

1

-1

0

emT

emΤ̂

ˆem Τ

em Τ

Table 1.Control strategy with

hysteresis comparator.

Figure 2.Block diagram of the

DTC of DSIM.

Direct torquecontrol of dualstar induction

motor

pbesti ¼ ðpbesti1; pbesti2; :::; pbestidÞ (6)

The index of the best particle amongst the group is gbestd. The velocity of particle ith isrepresented as:

vi ¼ ðvi1; vi2; ::::; vidÞ (7)

The modified speed and position of each particle can be calculated using the current and thedistance from pbesti,d to gbestd as expressed in the following equations:

vtþ1i:m ¼ w:vti:m|fflffl{zfflffl}

inertia

þC1* randðÞ*�pbesti;m � Xt

i;m

�|fflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl{zfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl}

personelinfluence

þC2* randðÞ*�gbesti;m � xti;m

�|fflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl{zfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl}

socialinfluence

(8)

xtþ1i;m ¼ xti;m þ vtþ1

i;m i ¼ 1; 2; :::; n ; m ¼ 1; 2; . . . ; d (9)

where: n is the number of particles in the group, d is the dimension index, t is the pointer ofiterations (generations), vti,m is the velocity of particle at iteration i, w is the inertia weightfactor, rand ( ) is the random number between 0 and 1, pbesti is the best previous position ofthe ith particle, gbest is the best particle among all the particles in the population, C1,C2 areacceleration constant. Velocity vector for position update is depicted in Figure 3.

4.1 Algorithm steps for PSOThe working of PSO algorithm is interpreted in the consecutive steps.

Step 1: We establish the values of PSO algorithm constants as an inertia weight factorW5 0.8, with acceleration constants C15 C25 2. The PSOmain program has to optimize inthis case three parameters, Ke, Kd and β to the fuzzy controller, and search optimal value of thethree-dimensional search space.

Step 2: So we arbitrarily configured a swarm of “50” population in three-dimensionalsearch space using (xi1, xi2, xi3), and (vi1, vi2, vi3) as preliminary situation along with velocity.Considered the primary fitness function of any also to the position with minimum fitnessfunction is displayed as best, so the optimal fitness function as pbest1.

Figure 3.Description of asearching pointby PSO.

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Step 3: Run theprogrambymeans of PSOalgorithm throughn numbers of iterations, aswell,the program finds the final optimal value of the fitness function as “best fitness” with the lastoverall optimal point as “gbest”. The PSO parameters are described in Table 2 in the Appendix.

The flowchart for fuzzy PSO-DTC-DSIM is shown in Figure 4.

4.2 Fitness function4.2.1 The conception of fitness function. To evaluate the static and dynamic conduct of thecontrol system, it is found that IAE offers good system stability with reduced oscillations theIAE criterion is widely adopted [41]:

Yes

No

Run the Fuzzy-DTC control model for each set

of parameters

Start

Generate initial populations

Calculate parameters (ke,kd , β )

of fuzzy-PID controller

Calculate the fitness function

of fuzzy-PID controller

Calculate the pbest of each particle and gbest of

population

Update the velocity, position,

gbest and pbest of particles

Stop

Maximum iteration

number reached?

Output the parameters (ke,kd , β )

of fuzzy-PID controller

Figure 4.Flowchart for fuzzy

PSO-DTC-DSIM.

Direct torquecontrol of dualstar induction

motor

IAE ¼Z

0

jeðtÞjdt (10)

5. Design of PID-PSO controller type FLC for the DSIMThe optimization of the FLC gains using PSO can be given by the input variable {e}, and theerror change {ec} as follows:

eðtÞ ¼ Ωref �ΩrðtÞ (11)

ecðtÞ ¼ deðtÞdt

(12)

Table 3 illustrated the performance of PID controller in the AppendixThe fuzzy PI controller is the commonly used because the PD one encounters difficulties in

deleting the steady state error. However, the fuzzy-PI gives a poor performance in thetransient response in higher order systems because of its inherent internal integrationoperation. It is therefore more convenient to combine PI and PD actions to design a fuzzy PIDcontroller (FLC-PID) to achieve proportional, integral, and derivative control action. It isimperative to obtain an FLC-PID controlled by adding the fuzzy-PD controller output and itsembedded part. The fuzzy-PID controller is depicted in Figure 5. Table 4 represented theperformance of fuzzy controller is in the Appendix.

Controllers Parameters

Kp 37.5Ki 0.35Kd 0

Descriptions Parameters

Number of particles in the swarm 50Number of Iterations 10Number of components or dimension 3Inertia weight factor w 0.8C15C2 2

ke

kdeddt α

PSO IAE

e

Fuzzy

Controller em Τ-

+

r

Feedback

u

U

E

E

ref

DTC-DSIM

+

+

r

Table 3.Performance of PIDcontroller.

Table 2.Parameters of PSOalgorithms.

Figure 5.The proposed controlstructure for PID-PSOtype FLC.

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The output u of the fuzzy PID is presented by:

u ¼ αU þZ

βU dt (13)

where: U is the output of the FLC.The relationship between the input and output variables is given by [42]:

U ¼ Aþ PE þ D dE=dt (14)

where: E 5 Ke.e and dE/dt 5 Kd.de/dt according to Figure 5.Therefore, from Eqs. (13) and (14) the controller output is expressed by the following

equation:

u ¼ αAþ βA:t þ αKe:Peþ βKd:D:eþ βKe:P

Zedt þ αKd:D:de=dt (15)

Finally, the components of PID-FLC can be deducted as follows:The proportional gain: αKe. PþβKd.D; The integral gain: β Ke.P; The derivative

gain: αKd.D.

5.1 FuzzificationThe inputs to the Fuzzy-PSO have to be fuzzified before being fed into the control rule andgain rule determinations. The triangular membership functions (MFs) used for the input(e, ec and, ΔTem) are shown in Figures 6 and 7. Linguistic variables are (NB, NM, NS, ZE, PS,PM, PB).

Where: NB is Negative Big, NM is Negative Medium, NS is Negative Small, EZ is EqualZero, PS is Positive Small, PM is Positive Medium, PB is Positive Big.

5.2 Inference and defuzzificationThe present paper uses MIN operation for the calculation of the degree m(ΔTem) associatedwith every rule, for example, m(ΔTem)5Min[m(e),m(ec)].

In the defuzzification stage, a crisp value of the electromagnetic torque is obtained by thenormalized output function as [33]:

du ¼Pm

j¼1μðΔTemjÞΔTemjPm

j¼1μðΔTemjÞ (16)

where: m is the total number of rules (7*7), m(ΔTem) is the membership grade for the n rule,ΔTem is the position of membership functions in rule n in U (�15,�10,-5,0,10,15).

Controller Fuzzy-PSO

Input scaling factor ke optimized 3.1604Input scaling factor kd optimized 3.6741β is the gain of the integral component 0.8081α scaling factor for the output u 1

Table 4.Performance of fuzzy-

PSO controller.

Direct torquecontrol of dualstar induction

motor

5.3 Control rule determinationThe logic of determining this rule matrix is based on a global knowledge of the systemoperation. As an example, we consider the following two rules:

if e is PB and ec is PB then ΔTem is PB

if e is ZE and ec is ZE then ΔTem is ZE

They indicate that if the speed is too small compared to its reference (e is PB), so a big gain(ΔTem is PB) is required to bring the speed to its reference and if the speed reaches itsreference and is established (e is ZE and ec is ZE) so impose a small gain ΔTem is ZE.

Table 5 represents the inference rules.

-15 -10 -5 0 5 10 150

0.2

0.4

0.6

0.8

1ZE PS PM PBNSNMNB

-1.5 -1 -0.5 0 0.5 1 1.50

0.2

0.4

0.6

0.8

1 ZE PS PM PBNSNMNB

Figure 7.Membership functionsfor ΔTem.

Figure 6.Membership functionsfor e and ec.

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6. Simulation results and discussionThe results were obtained using a PSO algorithm programmed and implemented inMATLAB. The parameters of the DSIM are presented in Table 6 (Appendix). To illustrate theperformances of the DTC of the DSIMwe replaced the classical PID controller by a fuzzy-PSOtechnique in Figure 8. The simulation is carried out under the following conditions: thehysteresis band of the torque comparator is set to ±0.25 Nm and that of the flux comparatorto ± 0.5 Wb.

Figure 9 depicts the waveforms of the improved performances of speed control. It can benoticed that the use of the fuzzy-PSO controller allows the speed to judiciously follow itsreference value of 100 rad/s despite the presence of a load torque of 14Nm at t5 0.6 s. In fact,this behaviour represents a clear improvement in dynamic response with a hybrid controller

Rated Power 4.5KW

Stator Resistance Rs15 Rs2 3.72URotor Resistance Rr 2.12UStator Inductance Ls 0.022HRotor Inductance Lr 0.006HMutual Inductance Lm 0.3672HPole Pairs P 1Machine Inertia J 0.0662 kg.m2Viscous Friction Coefficient fr 0.001 kg.m2/s

Ωref

Speed

sensor

3

3

(a,b,c,1)ss

Flux and Torque

Estimation

s

DSIM Switching

Table (ccpl)

1

0 +

- (cflx) sref

+-

Inverter2

s

( , ,1,2)sI

sψˆ ( , ,1,2)s

(a,b,c,2)ss

Inverter1

Vdc

( , ,1,2)sV

a,b,c

+ -

Fuzzy controller

PSO IAE

1 2 3

4 5 6

sψ̂

1

-1

0

Ωr emT̂

emT

ˆem Τ

emT

ecΔTem NB NM NS ZE PS PM PB

E NB NB NB NB NB NM NS ZENM NB NB NB NM NS ZE PSNS NB NB NM NS ZE PS PMZE NB NM NS ZE PS PM PBPS NM NS ZE PS PM PB PBPM NS ZE PS PM PB PB PBPB ZE PS PM PB PB PB PB

Table 6.DSIM parameters [12].

Figure 8.Block diagram of theproposed DTC-fuzzy-

PSO tuning speedcontroller.

Table 5.Inference rules.

Direct torquecontrol of dualstar induction

motor

that is adjusting strictly the values of the parameters by increasing the constant ofintegrationwithout an overshoot at the level of the dynamic response of the speed, contrary toa drive with a standard DTC-PID where the speed has underwent slightly rejected.

Performance with each controller is also analyzed through these of Integral Squared Error(ISE), Integral Absolute Error (IAE) and Integral Time Squared Error (ITSE), and the resultsdescribed in Table 7 confirm the improved performance with the fuzzy-PSO algorithm.

In Figure 10 the electromagnetic torque produced by theDSIM controlled byDTC-PID andDTC-fuzzy-PSO is presented. In this figure, it can be noticed that the ripple is not the same forthe two techniques. It is clear that the classical DTC-PID present two problems, steady stateerror and high torque ripples. On the other hand, the DTC-fuzzy-PSO corrects the steady stateerror and reduces the torque ripples.

Controllers IAE ISE ITSE

PID 0.5473 0.1498 0.1348Fuzzy-PSO 0.2072 0.0215 0.0193

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9-10

0

10

20

30

40

50

60

Time (s)

Tor

que

(N.m

)

PIDFuzzy-PSO

0.58 0.6 0.62 0.648

10121416

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.90

20

40

60

80

100

120

140

Time (s)

Spee

d (ra

d/s)

0.2 0.22 0.24949698

100102

0.6 0.605 0.61

99

100

101

PIDFuzzy-PSO

Table 7.Comparison ofperformance index.

Figure 10.Electromagnetictorque comparison ofthe two strategies.

Figure 9.Comparison of therotor speed regulationof the standard DTCand hybrid DTC.

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In Figure 11, it can be observed that the currents are sinusoidal and current ripples havealso a notable reduction in fuzzy-PSO controller compared to the standard controller.

Figure 12 shows the trajectory of stator flux for the standard DTC and the hybrid DTC. Itcan be seen that this hybrid strategy has less ripple.

Figure 13 summarizes the evolution of the fitness function with respect to the number ofiterations.

7. ConclusionIn this paper, a comparative study between the conventional DTC of the DSIM with PIDcontroller andDTC-fuzzy-PSO has been presented for a speed controller. From the simulationstudies, hybrid controller produced better performances in terms of a fast rise time, a smallovershoot, reduced torque and flux ripples. Therefore very satisfactory performances havebeen achieved. Furthermore, the effectiveness of the proposed algorithms is evaluated andjustified from performance indices IAE, ISE and ITSE. According to the yielded simulationresults one can conclude that this algorithm is suitable for applications requiring a high

-1.5 -1 -0.5 0 0.5 1 1.5-1.5

-1

-0.5

0

0.5

1

1.5

phisd1 (Wb)

phis

q1(W

b)

PIDFuzzy-PSO

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9-60

-40

-20

0

20

40

60

Time(s)

Stat

or c

urre

nt is

a1(A

)

PIDfuzzy-PSO

Figure 12.Stator flux trajectory in

the stator1.

Figure 11.Phase current in the

stator 1for both hybridDTC and standadDTC.

Direct torquecontrol of dualstar induction

motor

tracking accuracy in presence of external disturbances. In future, the work can be extendedby the applications of the intelligent hybrid techniques like neuro-fuzzy-GA, neuro-fuzzy-PSO, neuro-fuzzy-ACO.

AbbreviationsDSIM dual star induction motorFLC fuzzy logic controllerPSO particle swarm optimizationDTC direct torque controlPID proportional integral derevativeIAE the integral of absolute value of the errorISE the integral of square errorITSE the integral of time multiply square error

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AppendixSee.

Corresponding authorSebti Belkacem can be contacted at: [email protected]

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