International Journal of Applied Engineering Research ISSN 0973-4562 Volume 9, Number 24 (2014) pp. 23689-23699 Research India Publications http://www.ripublication.com

Design of FLC for OVR Reduction of Negative Output KY

Converter K. R. Sugavanam1, R. Senthilkumar2, S. Sri Krishna Kumar3, S. Karthikumar4,

V. Tamilmullai5

Abstract

Negative Output KY Boost Converter, a recent development in the field of non-isolated DC-DC boost converter is identified for minimum voltage ripple. In this article a Fuzzy controller is designed to minimize the output voltage ripple of the Negative Output KY boost converter output. The Fuzzy Logic Controller is designed in MATLAB/Simulink model and the digitally simulated results show a reduction in output ripple from 60mV of the existing PID controlled converter output to 3mV in the proposed Fuzzy Logic Controlled converter and the settling time of the output is found to be fast in comparison with the existing PID controller output.

Keywords: DC-DC Boost Converter, KY Converter, Fuzzy Logic Control, Voltage Ripple Reduction, PWM control.

Nomenclature CCM Continuous Conduction Mode ESR Equivalent Series Resistant Capacitance FLC Fuzzy Logic Controller LC Inductance Capacitance filter OVR Output Voltage Ripple PID Proportional-Integral-Derivative controller PWM Pulse Width Modulation ce change in error d duty cycle e error NB Negative Big NM Negative Medium PB Positive Big PM Positive Medium Z Zero

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Cb Energy Transferring Capacitor Co Output Capacitor Db Reverse Bias Diode Df Free-wheeling Diode fs Switching frequency L Output Inductor Ro Load Resistor S MOSFET Switch Vi Input Voltage Vo Output Voltage Introduction Innovation of electronic communication systems entails a negative output DC-DC boost converter source for specific input voltage. To ensure robust operation of these systems, design aspects such as output voltage ripple content, settling time and load transient response of the DC-DC boost converter has to be taken into concern.

Conventional non-isolated DC - DC boosting converters be likely to cause large output voltage ripples. The ripple content reduction techniques such as Equivalent Series Resistant (ESR) Capacitor [1] or by adding an inductance capacitance (LC) filter [2] were proposed for the converters working in Continuous Conduction Mode (CCM) [3]-[9] which leads to good load transient response. Also various controlling techniques like coupling inductors [3], voltage control techniques [4]-[9], sliding mode converter [10] and loop bandwidth control [11] were used for voltage ripple reduction. But these converters [3]-[9] have one right half plane zero in CCM mode which is difficult to achieve in practice. In recent decades non-linear control techniques like Fuzzy Logic Control [14]-[15], Neuro-Fuzzy control [16]-[18] and other controlling techniques exhibit better performance over the conventional methods. The KY boost converter [12]-[13] recently proposed by K. I. Hwu and Y. T. Yau produces Output Voltage Ripples (OVR) around 60 mV which is controlled by a conventional PID controller.

In this article Fuzzy Logic Control technique [14] is employed to minimize the output voltage ripple of the KY boost converter and the performance of the converter is estimated. The converter along with Fuzzy Inference System is designed in the Matlab/Simulink model and the simulated results exhibit a reduction in output voltage ripples from 60 mV of the existing PID controlled converter to 3 mV of the proposed Fuzzy controlled converter. The following sections enumerate the design and analysis of the KY Negative Output Boost Converter and its performance.

Negative Output KY Boost Converter The Negative Output KY boost converter [12]-[13] shown in the following fig. 1 operates in two modes of operation based on switching sequence. Negative output KY boost converter consists of switch S with protective diode Ds, inductor L, two

Design of FLC for OVR Reduction of Negative Output KY Converter 23691

capacitors, Cb for transferring energy and Co for output capacitor with load Ro. It also consists of Df, a freewheeling diode and Db, an energy transferring diode.

Fig. 1. Negative Output KY boost converter

In mode 1 operation of Negative Output KY boost converter as shown in fig. 2,

MOSFET switch S is in ON state. As a result inductor L is magnetized to a value equal to the input voltage Vi. Simultaneously in mode 1 capacitor Cb is charged and freewheeling diode Df is in action in mode 1 operation. The following equations (1) represent the mode 1 operation.

L

L

i

o oo

o

ii b

iL vtv vCt R

vi i Ct

(1)

Fig. 2. Mode 1 operation of Negative Output KY boost converter

In mode 2 operation of Negative Output KY boost converter as shown in fig. 3,

MOSFET switch S is in OFF state. As a result inductor L is demagnetized in mode 2 while capacitor Cb is discharged and energy transferring diode Db is conducting. The following equations (2) represent the mode 2 operation.

L

L

i o

b

iL v vt

i i

(2)

Fig. 2. Mode 2 operation of Negative Output KY boost converter

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From the equations (1) and (2), the relationship between input and output voltages, vi and Vo is regarded by the equation (3) as follows, where D is the duty cycle for PWM generation.

11

o

i

VV D

(3)

KY Boost Converter specifications For the proposed controller, the specifications adopted by K. I. Hwu [12] is considered as mentioned in Table I to compare the obtained results with existing technique.

TABLE I: SPECIFICATIONS ADOPTED FOR KY BOOST CONVERTER

Parameter Symbol Value Unit

Input Voltage Vi 5 V Rated Output Voltage Vo 12 V Inductor L 10 H Output Capacitor Co 2200 F Energy Transferring Capacitor Cb 1000 F Load Ro 6 Switching frequency fs 195 kHz

Where Li and Lo are input and output inductors; Cm represents buffer capacitance;

Cb represents energy transferring capacitor; Co represent output capacitor and load resistance is represent by RL.

Modeling of FLC for Negative Output KY Boost Converter Fuzzy Logic Controller [14] [15] designed to control the output voltage ripple of the Negative Output KY boost converter is shown in Fig. 4 in which the input to the Fuzzy controller is error (e) and change in error (ce), where error (e) is the deviation in output voltage Vo and reference voltage Vref. The output of Fuzzy controller is the duty cycle (d) which is fed to a PWM generator to produce control signal which is fed as switching signal to the KY boost converter switches to produce a boosted voltage Vo.

Fig. 4. Block diagram of Fuzzy Controller for KY boost converter

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Fig. 5 shows the Simulink model of the proposed Fuzzy controller for Negative output KY boost converter which shows a Fuzzy controller, PWM generator block with Negative output KY boost converter block with a reference output voltage of 12 V. The switching frequency generated by the PWM block is 195 kHz which is fed to the Negative output KY boost converter.

Fig. 5. Fuzzy control of KY Boost converter Simulink model

KY Boost Converter Simulink modeling The KY boost converter realized in Simulink model is shown in Fig. 6 in which switch is represented by S; Li represents input inductor; Cb represent energy transferring capacitor; Co is output capacitor; Db is energy transferring diode; Df is freewheeling diode and R is load resistor. The switching signal is fed through connector M and the output voltage and output current are taken across the Load R.

Fig. 6. KY boost converter Simulink structure

Fuzzy controller Simulink modeling The Fuzzy controller designed for the proposed technique is Mamdani fuzzy inference system in which the fuzzifier consists of inputs error (e) and change in error (ce) which is classified into Gaussian membership function with five classifications namely negative-big (NB), negative-medium (NM), zero (Z), positive-medium (PM) and positive-big (PB). The defuzzifier consists of output duty cycle (d) which is classified with the above mentioned membership function classifications. Fig. 7, Fig. 8 and Fig. 9 shows the above said classification of input functions e and ce and output function d.

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Fig. 7. Membership function view for input signal error

Fig. 8. Membership function view for input signal change in error

Fig. 9. Membership function view for output signal duty cycle

The Fuzzy knowledge rule base consists of 25 fuzzy rules which define the relation between the input variables and the output variable for controlling the duty cycle (d) to generate PWM signal which is given by the following Table II.

TABLE II: Fuzzy Rule Base

e ce

NB NM Z PM PB

NB NB NB NM NM Z NM NB NM NM Z PM Z NM NM Z PM PM PM NM Z PM PM PB PB Z PM PM PB PB

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The surface view of rule base developed for this controller is depicted by the Fig.10 as given below.

Fig. 10. Fuzzy rule base surface view

Simulation Results The digitally simulated results of the KY boost converter with input voltage 5V and rated output voltage of 12V for a load current of 2A which is simulated with Matlab/Simulink is shown by the following figures Fig. 11 and Fig. 12.

Fig. 11 shows the output voltage waveform of Fuzzy controller for a time period of 0.02 second. The settling time of the output voltage waveform is 3.5mS which is reduced to greater extent by the proposed Fuzzy controller as shown below.

Fig. 11. Output Voltage waveform for PID and Fuzzy controlled Negative Output KY Boost Converter

Fig. 12 shows the output voltage ripple for the proposed Fuzzy controller output.

It clearly shows that the output voltage ripple for an output voltage of 12V is about 3

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mV which is very low when compared to the output of 60mV for the existing PID controller.

Fig. 12. Output Voltage ripple waveform of Fuzzy controlled

KY Negative Output Boost Converter

Conclusion In this paper a Fuzzy Logic Controller is designed and implemented to improve the performance of Negative output KY boost converter and the results of the controller illustrate a reduction in settling time and rapid reduction in output voltage ripple. The resulting output values of the proposed Fuzzy Logic Controller are compared with the existing controller output in the following Table III. The minimization of output voltage ripple from 60 mV to 3 mV is validated through hardware output.

TABLE III: Comparison Of Existing And Proposed Technique Output

Parameter Existing PID controller Proposed Fuzzy Logic Controller

Settling time 50 mS 3.5 mS Output Voltage ripple 60 mV 3 mV

References [1] M.K. Kazimierczuk, R.S. Geise, A. Reatti, Small-signal analysts of a PWM

boost DC-DC converter with a non-symmetric phase integral-lead controller, 17th International Telecommunication Energy Conference ~INTELEC95~, 29 Oct - 1 Nov, 1995, Dayton, OH.

[2] R.B. Ridley, Secondary LC filter analysis and design techniques for current-mode controlled converters, IEEE Trans. Power Electronics, vol. 3, n. 4, Oct 1988, pp. 499 507.

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[3] H.B. Shin, J.G. Park, S.K. Chung, H.W. Lee, T.A. Lipo, Generalised steady-state analysis of multiphase interleaved boost converter with coupled inductors, IEE Proc. Electr. Power Appl., vol. 3 n. 152, 2005, pp. 584 594.

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[5] X. Chen, F.L. Luo, H. Ye, Modified positive output Luo converters, Proc. IEEE PEDS 1999, vol. 1, 1999, pp. 450 455.

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[7] F.L. Luo, H. Ye, Positive output super-lift converter, IEEE Trans. Power Electronics, vol. 18, n. 1, Jan 2003, pp. 105 113.

[8] M. Zhu, F.L. Luo, Development of voltage lift technique on double output transformerless DC-DC converter, Proc. IEEE IECON Conf., 2007, pp. 1983 1988.

[9] M. Zhu, F.L. Luo, Implementing of developed voltage lift technique on SEPIC, Cuk and double-output DC-DC converters, Proc. IEEE ISIE Conf., vol. 2, 2001, pp. 723 727.

[10] A. Savu, C. Radoi, A. Florescu, Sliding Mode PWM Control for a Buck Converter Under DCM/CCM Boundary, International Review of Electrical Engineering, vol. 5, n. 5, Oct 2010, pp. 1963 1971.

[11] Y.U. Hong, S.H. Jung, Y.J. Woo, B.K. Choi, G.H. Cho, Single-chip quasi-PWM DC-DC converter with fast transient response comprising loop-bandwidth control, IEEE Letters, vol. 8, n. 41, 2005, pp. 501 503.

[12] K.I. Hwu, W. C. Tu. Y.H. Chen, A Novel Negative Output KY boost converter, IEEE PEDES, 2009, pp. 1155 1157.

[13] K.I. Hwu, Y.H. Chen, W. C. Tu, Negative Output KY boost converter, IEEE International Symposium on Industrial Electronics, July 5-8, 2009, Seoul, Korea.

[14] N. F. N. Ismail, I. Musirin, R. Baharom, D. Johari, Fuzzy logic controller on DC/DC boost converter, Proceedings of the IEEE PECon, Nov29-Dec1, 2010, Kualalampur.

[15] N. F. Nik Ismail, N. Hasim, R. Baharom, A Comparitive study of Propotional Integral Derivative controller and Fuzzy Logic controller on DC/DC Buck Boost converter, IEEE symposium on Industrial Electronics and Applications ~ISIEA2011~, Sept 25-28, 2011, Langkawi.

[16] S. Karthikumar, N. Mahendran, Modeling of Neuro Fuzzy Controller for Negative Output KY Boost Converter Voltage Ripple Reduction, Elektronika Ir Elektrotechnika, vol, 19. No.6, 2013, pp. 47-50.

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[19] S. Karthikumar, N. Mahendran, S. Karthikraja Neuro-Fuzzy Control of 2nd Order KY Converter, IEEE PEDES, Bangalore, India, Dec 2012.

Authors information

Asst. Prof, V.T.H.T Engineering College, Chennai, India Asst. Prof, V.T.H.T Engineering College, Chennai, India Asst. Prof, V.T.H.T Engineering College, Chennai, India

Assoc. Prof, Saveetha university, Chennai, India

K.R.Sugavanam obtained his B.E in Electrical and Electronics Engineering from University of Madras in 2003, M.E in Power Electronics and Drives from Anna University in 2009. He has nearly eight years of teaching experience in various engineering colleges. He had published manuscripts in various National and International Conferences and Journals. Current research interests include Power

Electronics, Electrical Drives and Special Electric Machines. Mr. K.R.Sugavanam holds life membership in professional society IAENG, ICST,

EAI (eu).

R. Senthil Kumar has completed his graduation in Electrical and Electronics Engineering from Mookambigai College of Engineering, pudukottai under Anna University during 2007, and post-graduation in Power Electronics and Drives from A.C.C.E.T, Karaikudi under Anna University during 2009. He has teaching experience of nearly 5 years in engineering colleges . He had published manuscripts in various

National and International Conferences and Journals His current area of research includes power electronic converters, power electronic applications to power system, circuit analysis for power electronic circuits.

Mr. R. Senthil Kumarr holds life membership in professional society IAENG, ICST, EAI (eu).

S. Sri Krishna Kumar has completed his graduation in Electrical and Electronics Engineering from RVSCET, Dindigul under Anna University during 2008, and post-graduation in Power Electronics and Drives from Government College of Engineering, Salem under Anna University during 2011. He has teaching experience of nearly 3 years in engineering colleges. His current area of research includes power

electronic converters, power electronic applications to power system, circuit analysis for power electronic circuits.

Mr. S.Sri Krishna Kumar holds life membership in professional society IAENG, ICST, EAI (eu).

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S. Karthikumar obtained his B.E in Electrical and Electronics Engineering from University of Madras in 2000, M.E in Applied Electronics from Anna University in 2010 and currently pursuing his research in Power Electronics and Drives from St. Peters University, Chennai, India. He has nearly twelve years of teaching experience in various engineering colleges and has three years research experience.

He had published manuscripts in various National and International Conferences and Journals. Current research interests include Power Electronics, Electrical Drives and Special Electric Machines.

Mr. S. Karthikumar holds life membership in professional societies IEEE, IET, ISTE, IETE, IAENG. Also he is reviewer of various journals such as Taylor and Francis, JEET, ELEKTROTECHNIK journals.

Tamilmullai.V has completed her graduation in Electrical and Electronics Engineering from Dr.M.G.R Engineering College, Chennai under Anna University during 2006, and post-graduation in Power Systems from Govt. College of Technology under Anna University during 2010. She has teaching experience of nearly 4 years in engineering colleges. She had published manuscripts in various

National and International Conferences and Journals. Her current area of research includes power electronic applications to power system, Power System analysis.

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