Australian Journal of Basic and Applied Sciences

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1 Australan Journal of Basc and Appled Scences, 9(16) Specal 2015, Pages: ISSN: Australan Journal of Basc and Appled Scences Journal home page: Performance Evaluaton of Control Strategy on Buck-Boost Converter Fed DC Motor Usng Artfcal Bee Colony Algorthm 1 S. Ben John Stephen and 2 T. Ruban Devaprakash 1 Assstant Professor, Electrcal and Electroncs Engneerng, Noorul Islam Unversty, Taml Nadu, Inda 2 Professor & Prncpal, Heera College Of Engneerng & Technology, Kerala, Inda A R T I C E I N F O Artcle hstory: Receved 20 January 2015 Accepted 02 Aprl 2015 Publshed 20 May 2015 Keywords: Pulse Area Modulaton; buck-boost converter; ac-dc converter; dc motor; Artfcal Bee Colony Algorthm A B S T R A C T Ths paper presents comparson of the performance of buck-boost converter fed DC motor usng Artfcal Bee Colony algorthm wth that of Pulse Area Modulaton controller. It presents the use of Artfcal Bee Colony algorthm n the controller appled to ac-dc buck-boost converter fed dc motor. The proposed technque mproves the performance of Buck-Boost converter fed DC motor. The performance of the algorthm s qute comparable wth the results of the well-developed PAM Technque. The smulaton models of buck-boost converter fed dc motor are used to nvestgate the performance of the proposed confguraton. Comparsons between responses of the proposed Artfcal Bee Colony algorthm and conventonal controller technques are provded through smulaton AENSI Publsher All rghts reserved. To Cte Ths Artcle: S. Ben John Stephen and T. Ruban Devaprakash, Performance Evaluaton of Control Strategy on Buck-Boost Converter Fed DC Motor Usng Artfcal Bee Colony Algorthm. Aust. J. Basc & Appl. Sc., 9(16): , 2015 INTRODUCTION Generally, a dode brdge and a actor connected across the output termnals are employed for the converson of ac to dc. In ths converson, the harmonc components present n the nput current are hgh and we cannot vary the output dc voltage. Buck- Boost converter s used to decrease or ncrease the output voltage level n proporton to nput and so t s called or known as step-down/step-up converter also. Snce these converters have power devces, effect of swtchng and passve components lke nductors and actors, they are non-lnear systems (Prabha, D.M.M.S., S.P. Kumar, G.G. Devadhas, 2011). Many technques have been proposed to mprove the nput power factor and reduce the nput current harmonc components (Prasad, A.R., P.D. Zogas, S. Manas, 1990). The converson of ac to dc usng a dode brdge and a dc chopper has the advantage of hgher nput power factor [ee, Y.J., K.Y. Suh, D.W. Chung, 1987] than that of the thyrstor brdge. But, due to the lower-order harmoncs, the source current s dstorted. Pulse Wh Modulaton technque (Mech, A., S. Funabk, 1993) s also used n many attempts to mprove the performance of the swtchng devce. Ths paper descrbes the Artfcal Bee Colony Algorthm for the buck-boost converter fed dc motor. The Artfcal Bee Colony Algorthm s based on pulse area modulaton. The performance and adaptablty of speed control systems are mproved by usng ths controller. The ABC-PAM controller s smulated and the smulaton results are presented. Mathematcal Model of Buck-Boost Converter: A. Prncple of Operaton of Buck-Boost Converter: A confguraton of ac-dc buck-boost converter fed dc motor s shown n Fg.1. In ths confguraton, separately excted dc motor s used. Ths converter confguraton conssts of a dode brdge, an IGBT (swtchng devce), an nductor, a dode and an output actor. The output voltage magntude of Buck-Boost converter s ether greater than or less than the nput voltage magntude. Hence ths converter s also called as step-down or step-up chopper. In ths converter confguraton, the energy wll be stored n the nductor when IGBT s ON and energy wll be transferred to the load (dc motor) when IGBT s OFF. By approprately swtchng the IGBT, the stepup and step-down characterstcs of the output voltage can be easly obtaned. The proposed confguraton of buck-boost converter s approprate for low and medum power applcatons, such as power supples and motor drves. The ac-dc buck-boost converter can be especally suted as a front-end power source n varable-speed drve systems. Correspondng Author: S. Ben John Stephen, Assstant Professor, Electrcal and Electroncs Engneerng, Noorul Islam Unversty, Taml Nadu, Inda. Tel: E-mal: benjohnstephen@gmal.com

2 198 S. Ben John Stephen and T. Ruban Devaprakash, 2015 Australan Journal of Basc and Appled Scences, 9(16) Specal 2015, Pages: Fg. 1: Schematc dagram of AC-DC buck-boost converter fed dc motor. There are two dfferent power stages n the converson process, whch are the rectfcaton and the control stages. In the frst stage, a smple dode brdge rectfer s used to unfy the drecton of motor current and the supply voltage. In the second stage, an IGBT operatng n the choppng mode s used to control the ampltude of the output average voltage. As a result of the rectfcaton stage, the waveforms of the load voltage and current are repettve at a frequency equals double the supply frequency. B. Transent Analyss: In the model formulaton of Buck-Boost Converter, the assumptons are (a) power electronc components are deal (b) swtchng frequency s much greater than the supply frequency. So, the nput and output voltages can be consdered constant n each swtchng perod. The state varables can be obtaned from the IGBT and dode swtchng condtons. These state varables descrbe the dynamc behavor of buckboost converter fed dc motor. The output voltage of the dode brdge s gven by the expresson v vn vn, m snwt (1) The voltage equaton of a separately excted dc motor s gven by dm vo Rmm m kmwm (2) and the electromagnetc torque equaton s dwm Telectro Toad J Bwm (3) where km s the motor constant whch s gven by km kv f (4) and the electromagnetc torque developed s Telectro, develop kmm (5) The analyss s formed n a generalzed form that s applcable rrespectve of the number of pulses per supply cycle. For ths purpose, the supply voltage s assumed snusodal. Accordng to the selected current drectons n the three modes, the followng state/performance equatons can be formed: d v n motor dvo C Mode 2 (Dschargng Mode) d vo 0 n dv C Mode 3 motor o motor n 0 dv C o (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) C. Steady State Analyss: An approxmate equvalent crcut can be obtaned usng steady state analyss. Durng the swtchng perod of the swtchng devce IGBT, the nput voltage can be assumed constant due to hgh swtchng frequency. The average nductor voltage can be wrtten as a functon of the IGBT duty cycle D durng each swtchng cycle and s gven by v t Dvt 1 Dv o t (17) where v(t) s the average output voltage of the dode brdge and v o (t) s the average output voltage of the dc converter durng one swtchng perod. The voltage across the nductor s gven by dt v t t (18) where s the average current through the nductor durng each swtchng perod. From the above equatons, we can obtan the followng relaton d Dvt 1 Dvout t (19) Durng the chargng mode, energy s stored n the nductor. Durng the dschargng mode, the nductor current produces an output current. Hence, the average nput and output currents durng one swtchng perod are wrtten as n out t D t t 1 D t Substtutng Eq. (21) nto Eq. (19) gves (20) (21) Mode 1 (Chargng Mode)

3 199 S. Ben John Stephen and T. Ruban Devaprakash, 2015 Australan Journal of Basc and Appled Scences, 9(16) Specal 2015, Pages: D dout vt v t 2 out 1 D 1 D (22) The steady state equvalent crcut for the ac-dc buck-boost converter s represented by the Eq. (22) and s shown n Fg. 2. From the equvalent crcut, we can obtan the current relaton as t dvout C out t motor t (23) In order to obtan a smooth dc voltage, the output actor value should be hgh. Due to the large actor value, we can assume that the average values of the v out (t) and out (t) are constant and the average value of the second component of (22) s equal to zero. The relaton between the output voltage and the nput voltage as a functon of duty cycle s gven by v out t t D v 1 D (24) From ths equaton, t s clear that the proposed converter functons as a boost converter for duty cycle greater than 0.5 and as a buck converter for duty cycle less than 0.5. For duty cycle equal to 0.5, the output voltage s equal to the dc rectfed voltage. In practce, for hgh swtchng frequency, the duraton of mode 3 s very short. In such a case, we can neglect the mode 3. Fg. 2 represents the approxmate dc equvalent crcut of ac-dc buckboost converter. The nput to the dc dc converter s the fully rectfed voltage v(t) and D s the duty cycle of IGBT. In ths converter, the polarty of output voltage s opposte to that of fully rectfed voltage. So, ths converter s also called as nvertng converter. Fg. 3: PAM Control Crcut. When IGBT s on, energy wll be stored n the nductor. The nductor voltage s amplfed and ths voltage s appled nto the ntegratng crcut. In order to get a saw-tooth wave, the ntegratng crcut s reset at a constant nterval. The gradent of ths sawtooth wave s proportonal to the ampltude of the nductor current. PWM pulses can be obtaned by comparng the saw-tooth wave wth the full-wave rectfed nput voltage. These PWM pulses are used to drve the swtchng devce IGBT. In the PAM based control crcut, the ampltude of the reference wave can be controlled by the multpler. Snce the DC output voltage V out s compared to the reference voltage V ref, the value of V out wll be mantaned at a constant voltage. B. PAM Gatng Sgnals Generaton: The generaton of pulses usng PAM technque s llustrated n Fg.4. The swtchng devce IGBT s controlled by usng these gatng sgnals. When the current n the nductor ncreases gradually, the current becomes a saw-tooth wave whose gradent ncreases gradually as shown n Fg. 4. If the reference voltage s constant, the duty rato decreases gradually. So, the waveform of source current becomes square wave whose pulse wh decreases gradually and peak value ncreases gradually. Fg. 2: Approxmate dc equvalent crcut of ac-dc buck-boost converter. Controller Based on Pulse Area Modulaton: Ths secton descrbes the use of Pulse Area Modulaton technque n the controller for Buck- Boost converter fed DC Motor. The proposed confguraton usng Pulse Area Modulaton control crcut has been smulated and the waveforms have been presented. A. Pulse Area Modulaton Technque: The mplementaton of control crcut usng Pulse Area Modulaton technque s shown n Fg. 3. Fg. 4: PAM Gatng Sgnals. If the reference voltage s constant, there wll be no change n the areas of the pulses. But f the reference voltage waveform ncreases or decreases,

4 200 S. Ben John Stephen and T. Ruban Devaprakash, 2015 Australan Journal of Basc and Appled Scences, 9(16) Specal 2015, Pages: there wll be proportonal changes n the area of pulses. The pulse area s equal to the nstantaneous value of the nput current. Thus, f sne wave s used as reference waveform nstead of constant voltage waveform, the nput current waveform wll be changed nto a sne wave. By usng ths concept, we can mprove the nput power factor. C. Smulaton of PAM Controller: To study the performance of buck-boost converter fed dc motor, smulaton has been done. For the smulaton, a dc motor of rated Voltage=180 V, Current=8.5 A, power=1.5 kw and rated speed of 735 rpm havng armature resstance R m =2.85 Ω, armature nductance m =5.5mH, motor constant K m =2.22V/(rad/s) and J=0.26 kgm 2 s used. In order to apply a rated voltage of 180 V to the motor at a duty cycle of 0.8, the maxmum source voltage s selected as V. In ths confguraton, actor C of 333 µf, nductor of 96 mh and swtchng frequency of 1.80 khz have been chosen. The smulated characterstcs of the motor armature voltage, armature current and speed usng PAM technque s shown n Fg.5. (b) (c) Fg. 5: Smulated characterstcs of motor armature current, armature voltage and speed usng PAM technque (a) Artfcal Bee Colony-PAM Based Control Method: Ths secton descrbes the use of Artfcal Bee Colony algorthm n the controller for buck-boost converter fed dc motor. Fg. 6: Block Dagram of ABC-PAM Controller. The block dagram of ABC-PAM control model for the proposed converter s shown n Fg. 6. Error, e(t) s the dfference between the output voltage of the converter and a desred voltage value. Error s the nput of the ABC-PAM controller. et Vref Vo t (25) In the above equaton, e(t) s the error sgnal and V ref s the reference voltage. In the ABC-PAM control, the voltage across the reactor and full wave rectfed nput voltage are the controller parameters. ABC algorthm s used to defne these parameters optmally to make the system

5 201 S. Ben John Stephen and T. Ruban Devaprakash, 2015 Australan Journal of Basc and Appled Scences, 9(16) Specal 2015, Pages: stablty and obtan an effectve or robust transent response. A. Artfcal Bee Colony Algorthm to Optmze the Parameters: ABC s a robust optmzaton method s based on the foragng behavor of honey bees. It conssts of two phases.e., explotaton phase performed by employed & onlooker bee and exploraton phase performed by scout bee (Karaboga, D., B. Akay, 2012). In the ABC algorthm, artfcal bees whch are employed, onlooker and scout search the food source whch has the hghest nectar amount by modfyng the food postons by tme. In the ABC, whle a possble soluton of the problem corresponds to poston of a food source, ftness of the assocaton soluton corresponds to nectar amount of ths source. ABC algorthm works at 10 steps descrbed below (Sönmez, Y., 2013). Step1: Input data: mts of the controller parameters are read at ths step. In ths study, used lmts for the controller parameters are gven n Table 1. Table 1: mts of ABC-PAM parameters. Controller Parameters Range Mnmum Maxmum V 0 65 V n 0 70 Step 2: Intalzaton of ABC parameters: ABC parameters lke maxmum cycle number, colony dmenson, lmt parameter and number of varables are ntalzed. Step 3: Intal populaton: A set of ntal populaton wth M solutons x k (k=1,2, M) s produced randomly and ther ftness are determned. Here each soluton of x k represented by D-dmensonal vector corresponded to number of controller parameters optmzed. Step 4: Ftness evaluaton of the populaton: At ths step, ftness values obtaned from the ftness functon belong to each soluton s evaluated. The ftness functon used n ths study s descrbed as follows. ft n e 2 t t 1 (26) where e(t) s the error value descrbed n Eq. (25) and n s the maxmum teraton number n smulaton of operatng buck-boost converter for determned controller parameters at one cycle of ABC algorthm. Step 5: Set the cycle counter to 1: Step 6: Modfcaton of solutons (food source postons): In order to get better nectar amount, food sources are modfed and replaced by a new one va employed bees. Then the nectar amounts of modfed food sources are tested. If the new source has better nectar amount than old one, the new food source are kept the memory, otherwse t dscards. Ths process s descrbed as follows. v x x x k 1,2,..., M kl kl kl kl nl and j 1,2,..., D (27) where v kl s the new food source poston, n and l are randomly determned ndexes, β kl s a number determned randomly between -1 and +1. Step 7: Employng of onlookers and calculaton of probabltes: After the search process s over, the onlookers wat at the dance area for the nectar amount and poston nformaton. The poston nformaton and nectar amount are shared wth the onlookers by the employed bees. Accordng to a probablty value P k, onlooker bees prefer a food source. The probablty value P k s descrbed as follows. ft k Pk M ft l l 1 (28) where ft k s the ftness value of the k th soluton descrbed n Eq. (26) and M s the total number of food sources. Then, at ths step, onlooker bees modfy the food sources gven n Eq. (27) and test the nectar amount as n the case of Step 6. Step 8: Abandonng from the exploted source: At ths step, the food source s abandoned and replaced wth a new one by scout bees f there s no further mprovement n a food source. In the Artfcal Bee Colony algorthm, abandonng the food source s done based on the lmt parameter whch s predetermned number of cycles. Dscoverng a new food source by a scout s descrbed as follows. l l l l xk xmn rand 0, 1 xmax xmn (29) l l xmax and xmn are maxmum and mnmum lmts of the parameter to be optmzed. Step 9: Memorze the best soluton so far Step 10: Increase the cycle counter Step 11: Stoppng the algorthm Steps between 6 and 10 are repeated untl reach the Maxmum Cycle Number (MCN) determned before. Then, the searchng process s stopped.

6 202 S. Ben John Stephen and T. Ruban Devaprakash, 2015 Australan Journal of Basc and Appled Scences, 9(16) Specal 2015, Pages: B. Smulaton of ABC-PAM Controller: ABC-PAM Controller for buck-boost converter fed DC Motor s smulated n order to nvestgate performance of the proposed algorthm. The results obtaned n PAM Controller are compared wth that of ABC-PAM algorthm to show the effectveness of the ABC-PAM. For smulaton, the same dc motor parameters are chosen as n secton III. Smulated characterstcs of motor armature voltage, armature current and speed usng ABC-PAM Controller are shown n Fg.7. (a) Fg. 7: Smulated characterstcs of motor armature current, armature voltage and speed usng ABC- PAM Controller. C. Advantages of ABC-PAM Control: Comparng the smulated characterstcs of the dc motor shown n Fg.5 and Fg.7, t s clear that the peak overshoot of speed s less n model usng ABC- PAM controller than that of Controller based on PAM technque for the same dc motor and load condtons. Concluson: Ths paper presented the applcaton of Artfcal Bee Colony algorthm n the control of buck-boost converter fed dc motor, hghlghtng ts superor performance compared to the conventonal methods. The proposed converter confguraton uses only one power swtchng devce. Due to ths, the sze of the proposed converter s small and the energy loss s less. Snce t uses only one IGBT, t s convenent for an economcal varable dc voltage supply. The effects of the ABC-PAM algorthm on system performance of the buck-boost converter are nvestgated. Results show that ABC-PAM controller produces better results than PAM based controller to control the buck-boost converter n the way of settlng tme, and peak overshoot. The settlng tme and peak overshoot of the speed of motor s less n models usng ABC-PAM controller when compared to other conventonal control technques. Thus, the performance of the ABC-PAM Controller s superor to the conventonal control technques. REFERENCES (b) (c) Chen, J., D. Maksmovc, R. Erckson, Buck-Boost PWM Converters havng two ndependently controlled swtches n Proc. IEEE PESC, pp: Cheng, C.H., P.J. Cheng, M.J. Xe, "Current sharng of paralleled DC DC converters usng GA-based PID controllers," Expert Systems wth Applcatons, 37: Itoh, R., K. Isshzaka, Sngle-phase snusodal converter usng mosfets n IEE Proc., pp: Jallvand, A., H. Vahed, A. Bayat, "Optmal tunng of the PID controller for a buck converter usng bacteral foragng algorthm," n Proc. Intellgent and Advanced Systems Conf., pp: 1-5. Karaboga, D., "An dea based on honey bee swarm for numercal optmzaton," Techncal Report-TR06, Ercyes Unversty, Engneerng Faculty, Computer Engneerng Department. Karaboga, D., B. Akay, "A comparatve study of artfcal bee colony algorthm," Appled Mathematcs and Computaton, 214:

7 203 S. Ben John Stephen and T. Ruban Devaprakash, 2015 Australan Journal of Basc and Appled Scences, 9(16) Specal 2015, Pages: Karaboga, D., B. Akay, A Comprehensve surevy; artfcal bee colony algorthm and applcatons, Artfcal Intellgence Revew, Sprnger. ee, Y.J., K.Y. Suh, D.W. Chung, Optmal PAM strategy for varable-speed drve of three-phase nducton motor n Trans. Korean Inst. Elect. Eng., pp: 616. Mech, A., S. Funabk, Step-up/down voltage PWM ac-dc converter wth one swtchng devce n IEE Proc., pp: Namnabat, M., M.B. Poudeh, S. Eshtehardha, "Comparson the control methods n mprovement the performance of the DC-DC converter," n Proc. Power Electroncs Conf., pp: Ou, C., W. n, Comparson between PSO and GA for parameters optmzaton of PID controller, n Proc. IEEE Mechatroncs and Automaton Conf., pp: Prabha, D.M.M.S., S.P. Kumar, G.G. Devadhas, "An optmum settng of controller for a dc-dc converter usng bacteral ntellgence technque," n Proc. PES Innovatve Smart Grd Technologes Conf., pp: Prasad, A.R., P.D. Zogas, S. Manas, A novel passve wave shapng method for sngle-phase dode rectfers n IEEE Trans. Ind. Electron, pp: 521. Salmon, J.C., Crcut topologes for sngle-phase voltage doupler boost rectfers n Conference Proceedngs of the IEEE Apec 92, Boston, USA, pp: Sönmez, Y., "Estmaton of fuel cost curve parameters for thermal power plants usng ABC," Turksh Journal of Electrcal Engneerng and Computer Scence, 21: Sth, O., B.T. Oo, A Sngle-phase controlled current PWM rectfer n IEEE Trans. Power Electron., pp: 453. Takahash, I., W. Ikeshta, Improvement of nput current waveforms of a sngle-phase rectfer crcut n IEE J.Proc., pp: 174. Yousef, M.R., M.B. Poudeh, S. Eshtehardha, "Improvement performance of step-down converter through ntellgent controllers," n Proc. IEEE Intellgent Systems Conf., 4: