Mar 14, 2020 | IJMTST |
84 International Journal for Modern Trends in Science and Technology A High Voltage Gain Modified SEPIC Converter K Sangeetha 1 | Dr. S Senthil Kumar 2 1PG Scholar, Department of EEE, Government College of Engineering, Salem, Tamil Nadu, India. 2Associate Professor, Department of EEE, Government College of Engineering, Salem, Tamil Nadu, India. To Cite this Article K Sangeetha and Dr. S Senthil Kumar, “A High Voltage Gain Modified SEPIC Converter”, International Journal for Modern Trends in Science and Technology, Vol. 06, Issue 02, February 2020, pp.-84-89. Article Info Received on 20-January-2020, Revised on 09-February-2020, Accepted on 16-February-2020, Published on 22-February-2020. A high voltage gain modified SEPIC converter is proposed in this paper. This presented converter has many advantages i.e., non-inverting output voltage, lower voltage stress, high efficiency, voltage gain is high without any coupled inductor and transformer, continuous input current. Thus, there is no overshoot voltage at turn-off process for switches. By using same gate pulse for two switches, the CCM mode operation can be easily controlled by this converter, so control system is simple and also wide output values is obtained only by modifying the duty cycle. This modified converter has lower components than conventional converter. The operation and design of modified converter are discussed. The performance of proposed SEPIC converter is verified by simulation results. KEYWORDS: DC-DC converter, non-isolated converter, non-coupled inductor SEPIC converter,SEPIC converter. Copyright © 2014-2020 International Journal for Modern Trends in Science and Technology All rights reserved. I. INTRODUCTION In recent years, high voltage gain is an important research area. Due to increasing in demand of high voltage gain converters for various applications, this converter is proposed. Low power wind turbine, PV, fuel-cells, embedded systems, portable electronic equipment’s, uninterruptable power supply (UPS), electric tractions, battery backup for UPS, automobile headlamps, some medical equipment and battery powered equipment are some applications of high gain DC-DC converters . The boost converter is used to step up the output voltage. In order to boost the output voltage, continuous input current is preferred more than discontinuous input current due to some disadvantages . Boost converter (DC-DC) is used widely to step up the output voltage. But the voltage stress is higher in boost converter and also high rated switch is needed that ends in high conduction loss. And also, traditional buck-boost converter is used to step up or step down the voltage level. But it is not suitable for high voltage gain due to its discontinuous input current. Several dc-dc converters such as the flyback converter, single-ended primary-inductance converter (SEPIC), the Cuk converter, forward converter, inverting buck–boost converter has been proposed to obtain the high voltage gain and high efficiency. In flyback converter, efficiency is low due to its high-leakage inductance. The high gain buck-boost converter without transformer has discontinuous input current and negative polarity so it is not suitable. Mostly isolated DC-DC converters are used for high voltage gain. In isolated DC-DC converters, the overall weight and volume is increased by transformer and also high voltage gain is achieved by transformer turns ratio. During turn off process, the transformer causes voltage spikes due to leakage inductance. The switch voltage is limited 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 85 International Journal for Modern Trends in Science and Technology K Sangeetha and Dr. S Senthil Kumar, “A High Voltage Gain Modified SEPIC Converter” by additional clamping circuits and also it recycles the energy. Due to this, cost and complexity is increased with reduced efficiency . Nowadays, a non-isolated dc-dc converter is used widely because of its simplicity, small size, high efficiency, low cost in comparison with other converters . The non-isolated DC-DC boost converter with additional technique i.e., voltage multipliers, cascaded converters, switched capacitor cell and switched inductor cell. These techniques are operated without using any transformer and coupled inductor to achieve high voltage gain but the larger number of components reduces the efficiency with increased complexity -. Due to unique characteristics of SEPIC converter, it is most widely used in power electronics and other applications. In several papers, high voltage gain SEPIC converter is achieved with transformer and coupled inductor but due to its aforementioned drawbacks, it is not widely used -. To improve the performance and efficiency of SEPIC converter, a modified high voltage gain SEPIC converter is presented in this paper. The proposed converter is uncomplicated with lower number of components to have gain compared with other converters. In CCM mode of operation, the converter control is easy and simple by using same gate pulse for two switches. When compared with other non-coupled inductor SEPIC converter, the number of components and voltage stress are less. There is no voltage overshoot during turn off operation results in lower conduction losses. No clamping circuit is needed. The proposed converter is simple with continuous input current. So, it is suitable for renewable energy applications. The proposed SEPIC DC-DC converter is analyzed and performance are verified by the simulation results for low input voltage and high output voltage. In section II, modes of operation of the proposed SEPIC converter is presented. In section III, design considerations are discussed. In section IV, the proposed SEPIC converter is compared with other converters. In section V, the experimental results are given, Finally, section VI, conclusion is presented. II. OPERATING PRINCIPLE OF PROPOSED SEPIC CONVERTER A modified high voltage gain SEPIC converter is shown in Fig.1. The proposed SEPIC converter consists of one diode D0, three inductors L1, L2 and L3, two switches S1, S2 and two capacitors CS, C0. The input source is Vin and output voltage is V0. The two non-coupled inductor L1, L2 are simultaneously switched and the two inductors are connected in series/parallel at the time of charging mode and discharging mode. Some assumptions are made considered while simplifying the analysis i.e., all the components are ideal, constant capacitor voltage and also number of turns in L1 and L2 are equal.For steady state operation, inductor voltage (VL) and capacitor currents (Ic) are zero. The proposed SEPIC converter can operate in continuous conduction mode and operating principles of continuous conduction mode has two modes mode 1 and mode 2. In mode 1, both the switches are in ON condition . And in mode 2, both the switches are in OFF condition. CCM OPERATION In this operation, there are two operating modes for presented converter. The operation modes are explained in detail as follows. Mode 1: The diode is blocked and Two switches S1 and S2 are simultaneously turned ON. Then the source energy is transfered to L1, L2, L3. The input voltage is across the parallel connected inductors L1 and L2. The load gets charged from stored energy in the output capacitor. The current flow in mode 1 is given in Fig.2(a). The input inductor voltages are obtained as
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