Mar 14, 2020 | IJMTST |
79 International Journal for Modern Trends in Science and Technology Design and Development of High Step-up DC/DC Converter T Raja Pandiammal 1 | Dr. Sumithira T R 2 1PG Scholar, Department of EEE, Government College of Engineering, Salem, Tamil Nadu, India. 2Assistant Professor, Department of EEE, Government College of Engineering, Salem, Tamil Nadu, India. To Cite this Article T Raja Pandiammal and Dr. Sumithira T R, “Design and Development of High Step-up DC/DC Converter”, International Journal for Modern Trends in Science and Technology, Vol. 06, Issue 02, February 2020, pp.-79-83. Article Info Received on 20-January-2020, Revised on 09-February-2020, Accepted on 16-February-2020, Published on 21-February-2020. In the design of photovoltaic systems connected to the grid system, usually DC-DC converter is essential to increase the output voltage of the photovoltaic input voltage. The most common type of SEPIC (single ended primary inductance converter) DC-DC converters with high gain static is used in order to increase the output voltage of the photovoltaic input voltage and to obtain a high conversion efficiency. However, the conventional SEPIC converters can only be able to increase the static gain by three times of the input voltage in order to meet the dc input voltage of the inverter, the input voltage of the converters have to increase more than 10 times. Therefore, to overcome these problems, this paper proposes the design of DC-DC modified SEPIC converter topology for photovoltaic applications. Modifications to the conventional SEPIC converter is done by adding capacitors and diodes. From the experimental results it is observed that this converter is able to increase the output voltage by ten times to that of input voltage when added with voltage multiplier. KEYWORDS: -photovoltaic, converter, static gain Copyright © 2014-2020 International Journal for Modern Trends in Science and Technology All rights reserved. I. INTRODUCTION Smart grid systems refer to the use of control technology and digital information to increase the security, reliability and efficiency of the electric grid in the world . The smart grid system is integrated from non-conventional energy resources like solar, fuel cell and wind energy. Solar is considered to be the highly potential renewable energy source and hence can be utilized at the maximum . The power from the PV system is distributed in two different condition, one is through grid connected mode and other is through standalone mode. For grid applications, PV systems is connected to a dc-dc converter in series with the inverter to obtain ac power [3-5]. So, there comes a need to develop a converter which will boost up the voltage in such a way so as to meet the practical demands . The Boost converter is able to generate high step-up voltage with high duty cycle. DC-DC converters are used to regulate the voltage to a desired value. There are different converters to obtain the regulated the output voltage . The fluctuation in the value of the line voltage is due to the usage of power electronic devices. In recent scenario there is increasing growth of low voltage storage elements. With development of power electronic device and devices compactness lead to its application in various field such as in battery energy storage system, adjustable speed drives and in battery charging for electric car.There are many fields of application where high static gain, high efficiency, ABSTRACT Available online at: http://www.ijmtst.com/vol6issue02.html International Journal for Modern Trends in Science and Technology ISSN: 2455-3778 :: Volume: 06, Issue No: 02, February 2020 80 International Journal for Modern Trends in Science and Technology T Raja Pandiammal and Dr. Sumithira T R, “Design and Development of High Step-up DC/DC Converter” cost and weight are the prime aspect for implementation of any devices [8-10]. There are different types of topology to convert dc voltage of one level to dc voltage of other level. such like converters are buck converter, Cuk converter, Luo converter and boost converter. Each converter varies in the way they perform depending upon the components used. Some of the converter uses one switch, some uses five to 10 switches. So, in order to increase to increase the static gain of converter generally its circuit complexity will be increased. The proposed topology of modified SEPIC converter aims to reduce the number of switches used and thereby reducing the complexity of the circuit. DC/DC Converter are broadly classified as isolated and non-isolated converter . Isolated converters are used to protect the source and load from getting damaged due to fault by providing an isolation transformer between the source and load. Another way of increasing the static gain is by adding voltage multiplier. Voltage multiplier is the combination of diode capacitor and inductor, connected in cascaded with the existing topology and hence reduce the need of bulk coupled inductor [12-14]. It is possible to achieve a gain of more than ten times with the proposed converter topology. Modification in any converter can be done in two way one by using magnetic coupling and other by using non-magnetic coupling circuit. It has been seen that SEPIC converter with non-magnetic coupling gives the desired gain at limited requirements . The proposed converter operates at fixed switching frequency and duty ratio. These characteristics improve the response speed, reduce passive component size and allow the use of low loss sinusoidal gate pulse. II. PRINCIPLE OPERATION OF PROPOSED MODIFIED CONVERTER The SEPIC converter is a DC/DC converter. It is used to regulate the output voltage from an input voltage. Whatever be the changes in the magnitude of input voltage, corresponding output voltage will be regulated. The existing topology of SEPIC converter consist of two inductor, one capacitor and a diode. All the control action is performed by IGBT. The pulse is generated by using Arduino uno controller. When the pulse is high at the gate terminal of IGBT the switch will get turned on and when the pulse is low the switch will be turned off. Duration for which the inductor is getting charged will define the static gain of the converter. The modified proposed SEPIC converter contain a diode and a capacitor in addition to the existing topology. This combination of diode and capacitor plays the role of voltage multiplier and it is shown in Fig.1. Fig.1 Modified SEPIC converter In this mode of operation switch S is turned off, diode D1 and D2 is in forward biased condition that is it act as short circuited. Here current flows from VS-L1-D2-C2-VS, VS-L1-C1-L2-C2-VS and through VS-L1-C1-D1-C3. Capacitor C3 is getting charged. Since capacitor C3and load R are in parallel the output voltage is equal to the capacitor C3 voltage. The Mode1 operation of proposed converter is shown in the Fig.2 Fig.2 Mode1 operation In this mode of operation switch S is in on condition and diode DM and DO are reversed biased. Here current takes the path VS-L1-S-VS and also current pass through VS-L1-CS-L2-CM and the capacitor CO discharged through load. The input current is the average current across L1 and the output current is the average of current across L2. TheMode2 operation of proposed converter is shown in the Fig.3 Fig.3 Mode2 operation 81 International Journal for Modern Trends in Science and Technology T Raja Pandiammal and Dr. Sumithira T R, “Design and Development of High Step-up DC/DC Converter” III. HARDWARE DEVELOPMENT OF PROPOSED CONVERTER Fig 4. Block diagram of proposed converter A prototype was constructed to verify the properties of the proposed converter in the laboratory. Fig.4 shows the block diagram of the proposed DC-DC converter. Arduino Uno is used to generate gate pulse to trigger switch. MOSFET IRFP4668 is used as switch. An opto isolator is used to connects input and output sides with beam of light modulated by input currents. Two IN4007 diodes are used in the proposed converter. Two inductors of 50µH and 2 mH, one 450V/47µF capacitor, two 450V/2.2µF capacitors are also used, the resistor load is 1KΩ. The switching frequency is 50 kHz. The input voltages are varied from 0V to 30V, while the dc output voltage can be boosted in the range of 0 V to 300V. The input voltage Vin is given by: Vin = L1*diL1/dt The voltage across capacitor C1, Vc1 Vc1 = L2*diL2/dt The voltage across capacitor C2, VC2 VC2 /R = -C2*dVC2/dt VC2 = L2 *diL2/dt Duty Ratio VO/VIN =D/(1-D) (VO+VD)/VIN = D/(1-D) D=(VO+VD)/(VO+Vi+VD) Where: d: duty ratio VO : output voltage Vi : input voltage Maximum duty cycle, Dmax Dmax = (VO+VD)/ (VO+Vimin + VD) Inductor Selection Change in inductor current, ∆IL ∆IL = Iin*40% = IO*(VO/Vi min)*40% The inductance value of inductors L1and L2 is given by L1=L2=L = Vi min*Dmax/∆IL*Fsw = VO(1-D)/Fs. ∆IL IL1 peak = IO((VO+VD)/Vi min)*(1+(40%/2)) IL2 peak = IO((VO+VD)/Vi min)*(1+(40%/2)) If L1 and L2 on same core then L1=L2=L Input Capacitor Selection The rms value of current across capacitor, IC rms IC rms =∆IL /√2 Output Capacitor Selection The rms value of current across output capacitor, IO rms IO rms = IO √(VO+VD)/Vi min The capacitance value of output capacitor, CO CO = IO*D/Vripple*0.5*fs Output Diode Selection VRD= Vi max +Vo max VRD : min peak reverse voltage Design Consideration Switching frequency = 50khz Minimum input voltage =1V Maximum input voltage =5V Maximum output voltage = 50V VO/VIN = 1+D/1-D 50/5=1+ D/1-D= D = 0.81 IO =Pout/Vout=10/50=0.2A INDUCTOR ∆IL = IO*VO/Vi min* 10% =0.2*50/5*.01 =2A L1=L2 =VO(1-D)/fs *∆IL = 50(1-0.81)/10000*2 =50 µH CAPACITOR CO =IO*D/∆VCO*R*fs =0.2*0.81/1*1000*66 = 47 µF C1 = IO/∆VC*fs =2/1*50000 = 2.2 µF TABLE I PROPOSED CONVERTER CIRCUIT PARAMETERS SYMBOL PARAMETER VALUE VIN Input Voltage 30V FS Switching frequency 50KHz LI Inductor 2mH L2 Inductor 50µH C1 Output Capacitor 100µF R Resistor 1KΩ VO Output Voltage 280V CM Capacitor 2.2 µF CS Series Capacitor 47µF LF Filter inductor 1.9mH 82 International Journal for Modern Trends in Science and Technology T Raja Pandiammal and Dr. Sumithira T R, “Design and Development of High Step-up DC/DC Converter” Table I consist of various circuit parameters range such as input voltage, switching frequency, inductor, capacitor, resistor, output voltage, filter capacitor and filter inductor. IV. SIMULATION AND ITS RESULT The simulation model of proposed converter was done in MATLAB/SIMULINK platform 2016a.The simulation model is shown in Fig.5. Fig 5 Simulation of proposed topology It has been observed that in existing topology for input voltage of 5V, the output voltage is equal is 13.98V and in case of simulation of proposed topology for the input of 5V, the output voltage is 48.05V. This clearly shows that in proposed topology the output voltage is increased by 10 times by using voltage multiplier.Simulation result of input voltage of proposed system is shown in fig.6(a)and the Simulation result of output voltage of proposed system is shown in Fig.6(b) (a) (b) Fig.6 Simulation result of (a)input voltage(b)output voltage of proposed topology Fig.7 shows the prototype of complete hardware of proposed topology. 230V ac supply is fed to a single phase 230/15V step down transformer, this 15V ac voltage is fed to a bridge rectifier of driver circuit. The output of the optocoupler is fed to MOSFET of the power circuit. A voltage regulator circuit is used to fed 12V supply to Arduino board. The voltage regulator circuit consist a single-phase transformer, bridge rectifier, 63V/100µF and 63V/4.7µF capacitors, 7812 regulator IC, 1K resistor and a LED. Fig.7 Hardware Prototype The voltage regulator circuit is used to generate 12V supply so as to feed the controller. The controller will work only after providing a dc supply of 12V.The voltage regulator circuit is shown in Fig.8 Fig.8 Voltage regulator circuit 83 International Journal for Modern Trends in Science and Technology T Raja Pandiammal and Dr. Sumithira T R, “Design and Development of High Step-up DC/DC Converter” The driver circuit consist of one 63V/100µF capacitor, two of 1K and 100Ω resistors, a bridge rectifier and an IC base to place optocoupler TLP250. The driver circuit is shown in Fig.9 Fig.9 Driver circuit It has been observed that on complete arrangement of hardware, for variation of input voltage from 0V-30V the output voltage varies from 0V-300V and it is shown in Table II. TABLE II HARDWARE RESULT OF PROPOSED SYSTEM S.NO. INPUT VOLTAGE(V) OUTPUT VOLTAGE(V) 1 10 98.4 2 15 148.3 3 20 199.8 4 25 249.4 5 30 298.2 V. CONCLUSION The conventional SEPIC converter need capacitance with high value and high current handling capacity. The bulk inductor is used in conventional SEPIC converter, so it increases the component size and reduces the response speed. Like conventional SEPIC Converter, the bulk inductor limits the response speed of the multi resonant SEPIC Converter. Unlike the conventional SEPIC converter,modified SEPIC converter bulk inductor is not used and are allowed to operates at fixed frequency and the duty ratio. These characteristics reduce passive component size, improve response speed. Soft switching can be achieved for a wide input and output voltage ranges. A modified SEPIC converter is analyzed and designed. The converter model is simulated on Simulink for open loop and closed loop system. Although the proposed structure presents a higher circuit complexity than the basic converter but higher static gain was obtained for the operation with the low input voltage, low switch voltage operation. REFERENCES  H. Suryoatmojo*), I. Dilianto, Suwito, R. Mardiyanto, E. Setijadi and D.C. Riawan , Design and Analysis of High Gain Modified SEPIC Converter for Photovoltaic Applications IEEE Transactions on power electronics , may 2018  B. Gu, J. Dominic, J. S. Lai, Z. Zhao, C. Liu, “High Boost Ratio Hybrid Transformer DC–DC Converter for Photovoltaic Module Applications,” IEEE Transactions on Power Electronics, vol. 28, no. 4, April, 2013.  R. Gules, W. M. Santos, F. A. Reis, E. F. R. Romaneli, and A. A. 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Sweta Srivastav, Sanjay Kumar Singh, An introduction to Resonant SEPIC converters with variable Input and Output conditions International Referred Research Journal,September ,2012.  Jingying Hu, Student Member, IEEE, Anthony D. Sagneri, Student Member,IEEE, Juan M. Rivas, Member, IEEE, Yehui Han, Member, IEEE, Seth M. Davis, and David J. Perreault, Senior Member, IEEE “High-Frequency Resonant SEPIC Converter With Wide Input and Output Voltage Ranges” IEEE Transaction on power electronics.vol.27,no.1,january 2011.  J. Hu, Design of a low-voltage low-power dc-dc hf converter, M.S. thesis, Dept. Elect. Eng. Comput.Sci.,Massachusetts Institute of Technology (MIT), Cambridge, 2008.  R. C. Pilawa-Podgurski, A. D. Sagneri, J. M. Rivas, D. I. Anderson, and D. J. Perreault, “Very high frequency resonant boost converters,” in Proc. Power Electron. Spec. Conf., Jun. 2007.
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