An Improved Single Input Multiple Output Converter

Transcription

1 International Conference on Advanced Trends in Engineering and Technology-04 (FORSCHUNG) 07 An Improved Single Input Multiple Output Parvathy and David E Abstract The aim of this study is to develop a single input multiple output converter which is capable of producing bith dc and different levels of ac voltages The proposed converter can boost the voltage of a low voltage input power source to a controllable high voltage dc bus and middle voltage output terminals and also can invert the voltage to different ac output voltage levels. This coupled inductor based converter the properties of voltage clamping and soft switching thereby achieving the objective of high power conversion efficiency, high step up ratio, and various output voltages with different levels. The SIMO converter topology was designed and simulated using MATLAB/SIMULINK. Keywords DC-DC, H Bridge Inverter, Coupled Inductor, High Efficiency Power Conversion, Soft Switching, oltage Clamping. I. INTRODUCTION HE development of clean energies without pollution have Ta major role in protecting the natural environment on earth. Due to the electrical characteristics of these clean energy, power generated is critically affected by climate or has slow transient response, and the output voltage is easily influenced by load variations []-[4]. Besides other auxiliary components such as balance of plant (BOP), e.g. storage elements, control boards, etc., are usually required to ensure the operation of clean energy. In other words the generated power should satisfy the power demand of the BOP. Thus, various voltage levels should be required in the power converter of clean energy system. In general various Single input single output dc-dc converters with different voltage gains are combined to satisfy the requirement of various voltage levels, so that the system becomes more complicated and the corresponding cost is more expensive. The aim is to design a SIMO converter [] for increasing the conversion efficiency and voltage gain, reducing the control complexity, and saving the manufacturing cost. Some of the existing methods say a SIMO DC DC converter [5] capable of generating buck, boost, and inverted outputs simultaneously. However, over three switches for one output were required. This scheme is only suitable for the low Parvathy v, Dept. of Electrical and Electronics Engineering, Nehru College of Engineering and Research Centre, Thrissur, India. paru.annapurna@gmail.com David E, Dept. of Electrical and Electronics Engineering, Nehru College of Engineering and Research Centre, Thrissur, India. daviddavid984@gmail.com output voltage and power application, and its power conversion is degenerated due to the operation of hard switching. Another was a new DC DC multi-output boost converter [6], which can share its total output between different series of output voltages for low- and high-power applications. Unfortunately, over two switches for one output were required, and its control scheme was complicated. Besides, the corresponding output power cannot supply for individual loads independently. A multiple-output DC DC converter with shared zero-current switching (ZCS) lagging leg [7] is another topology, although this converter with the soft-switching property can reduce the switching losses, this combination scheme with three full-bridge converters is more complicated, so that the objective of high-efficiency power conversion is difficult to achieve, and its cost is inevitably increased. The SIMO converter [] with a coupled inductor uses one power switch to achieve the objectives of high efficiency power conversion, high step up ratio, and different output voltage levels. The techniques of soft switching and voltage clamping are adopted to reduce the switching and conduction losses via the utilisation of a low voltage rated power switch. The problems of stray inductance and reverse recovery currents within diodes in conventional boost converter also can be solved, so that the high efficiency power conversion can be achieved. The voltages of middle voltage output terminals can be appropriately adjusted by the design of auxiliary inductors. The output voltage of the high voltage dc bus can be stably controlled by a simple proportional integral (PI) control. With reference to the above converter, designed SIMO converter another isolated converter whose output is controllable and can produce different levels of ac and dc voltages which can be used in numerous applications. In Section II the converter design analyses are given. In section III simulation results are presented and finally in section I conclusions are drawn. II. CONERTER DESIGN AND ANALYSES The system configuration of the proposed highefficiency SIMO converter topology to generate two different dc voltage levels from a single-input power source is shown in Fig.. This SIMO converter contains five parts including a low voltage-side circuit (LSC), a clamped circuit, a middle voltage circuit, an auxiliary circuit, and a high-voltage-side circuit (HSC). The major symbol representations are summarized as follows. FC (i FC ) and O (i O ) denote the voltages (currents) of the input power source and the output load at the LSC and

2 International Conference on Advanced Trends in Engineering and Technology-04 (FORSCHUNG) 08 the auxiliary circuit, respectively; O and i O are the output voltage and current in the HSC. CFC, C O, and C O are the filter capacitors at the LSC, the auxiliary circuit, and the HSC, respectively; C and C are the clamped and middlevoltage capacitors in the clamped and middle-voltage circuits, respectively. L P and L S represent individual inductors in the primary and secondary sides of the coupled inductor T r, respectively, where the primary side is connected to the input power source; Laux is the auxiliary circuit inductor. The main switch is expressed as S in the LSC; the equivalent load in the auxiliary circuit is represented as R O, and the output load is represented as R O in the HSC. transmit the energy C. As the partial energy of L kp is transmitted to L aux D conducts and supply the power for the output load in the auxiliary circuit. This mode ends, when the secondary side of the coupled inductor releases its leakage energy completely, and the diode D 3 turns OFF. In mode 4 (t 3 t 4 ), the main switch S is persistently turned OFF. The secondary current i Ls flows through D 4 to HSC. In mode (t 4 - t 5 ) the main switch S is persistently turned OFF, and the clamped diode D turns OFF. In this mode, the input power source, the primary winding of the coupled inductor T r, and L aux connect in series to supply the power for the output load in the auxiliary circuit through D. At the same time, the input power source, the secondary winding of the coupled inductor T r, C, and C connect in series to release the energy into the HSC through D 4. Mode 6 (t 5 t 6 ) begins when the main switch S is triggered. The i Laux needs time to decay to zero, the diode D persistently conducts. When i LS decays to zero, this mode ends. Fig.. System Configuration of High-Efficiency Single-Input Multiple-Output (SIMO) The corresponding equivalent circuit given in Fig. is used to define the voltage polarities and current directions. The coupled inductor in Fig. can be modeled as an ideal transformer including the magnetizing inductor and the leakage inductor in Fig.. Fig.. Equivalent Circuit The characteristic waveforms are shown in Fig. 3. In mode (t 0 -t ), the main switch S was turned ON for a span and the diode D 4 turned OFF. D 3 turns on and this mode ends when L aux releases its stored energy completely, and D turns OFF. In mode (t -t ) main switch S is persistently turned ON. v Ls charges the C through the D 3. In mode3 (t -t 3 ), the main switch S is turned OFF. D 3 persistently conducts.when the voltage across the main switch v S is higher than the voltage across the clamped capacitor C. D conducts to Fig.3. Characteristic Waveforms of High-Efficiency SIMO A. oltage Gain The voltage gain G H of the proposed SIMO converter from the LSC to the HSC can be given as

3 International Conference on Advanced Trends in Engineering and Technology-04 (FORSCHUNG) 09 G N + O H () FC d The voltage gain G L of the proposed SIMO converter from the LSC to the auxiliary circuit can be given as G L O FC ( d ) + ( d ) + [8L aux (R O T )] () The system configuration of the fly-back converter generating another controllable voltage is shown below in Fig. 4.The major symbol representation are summarized as follows. FC, 03 are the input and output 5oltages. C 03 is the filter capacitor and R 03 is the output load. The characteristic waveform is also shown in Fig. 6 s Fig. 6 Proposed Generalised Model By the proper switching of the switching devices various dc voltages will be obtained and when the output fed to the H bridge inverter the voltage will get inverted and obtain different levels of ac voltages. B. Design and Simulations The minimum and maximum resistances connected at the auxiliary circuit and the HSC as R G P, R Omax G LFC Pmin ) ( Omin L FC max R G P, R Omax G HFC Pmin ). ( Omin H FC max Fig. 4 System Configuration of Flyback Fig.5 Characteristic Waveforms When the switch S i is on, due to the winding polarities the diode D 5 becomes reverse biased. The continuous conduction mode corresponds to an incomplete demagnetization of the inductor core in the flyback conductor. The inductor core flux linearly increases from its initial value. When the switch is turned off and the energy store in the core causes the current to flow in the secondary winding through D 5. Now the two converter voltages are given to an H bridge inverter with the help of switches where we get different levels of ac voltages. Fig 6 shows the proposed generalize model [0]. In this paper it is designed to get two controllable dc voltages one auxiliary voltage and 7 levels of ac voltages. Furthermore, this converter is operated with a 00 khz switching frequency (f S 00 khz), and the coupling coefficient could be simply set at one (k ) because the proposed circuit has a good clamped effect. The limit for L aux can be calculated as L aux < 0.5d R O T S. The voltage across the main switch S can be rewritten as v S O (N + ) In this, the clamped diode D should be a fast conductive device. Because the clamped voltage of the diode D is the same as the one of the main switch S, a low-voltage Schottky diode can be adopted to conduct promptly with lower conduction loss and reverse-recovery current. During the mode, the diode D turns OFF, and its voltage can be represented by v D O + [L aux (di D dt)] (3) (4) The voltage across the diodes D 3 and D 4, which can be expressed by v + D3, D4 O (C + FC ) [N (N ) ]O (5) In the proposed SIMO converter, the electric charge variation ΔQ, of the filter capacitor for the auxiliary circuit can be represented as ΔQ (O R O)(d d x )Ts COΔO and the voltage ripple of O can be rearranged as (6)

4 International Conference on Advanced Trends in Engineering and Technology-04 (FORSCHUNG) 0 ( O O) (d d x ) (R OCOfS) (7) Moreover, the electric charge variation of the filter capacitor ΔQ for the HSC can be expressed as ΔQ (O R O)dTS COΔO The input power source FC is, for converter auxiliary inductance is μh, the capacitance values for C 85μF/00, C 0 μf/50, C 0 00 μf/35, C 0 0 μf/50, C μf/35 Coupled inductor L p, L s are 3 μh, 75μ H are the specifications designed for simulation. as and the ripple of the output voltage O can be rearranged ( ΔO O ) d (R OCOfS) (9) Fig. 7.Simulation Model of SIMO Fig.8 Simulation Model of Subsystem

5 International Conference on Advanced Trends in Engineering and Technology-04 (FORSCHUNG) III. SIMULATION RESULTS The SIMO converter was simulated using MATLAB/SIMULINK and the resulting waveforms are as shown below. auxiliary battery module or high-voltage dc bus to ensure the property of voltage clamping; iii) an auxiliary inductor is designed for providing the charge power to the auxiliary battery module and assisting the switch turned ON under the condition of ZCS; iv) the switch voltage stress is not related to the input voltage so that it is more suitable for a dc power conversion mechanism with different input voltage levels; and v) the copper loss in the magnetic core can be greatly reduced as a full copper film with lower turns. This high-efficiency SIMO converter topology provides designers with an alternative choice for boosting a low-voltage power source and to get ac voltages. REFERENCES Fig. 9 Input and output waveforms of voltage SIMO The output voltage is shown above. The output voltage at HSC is 00 and at auxiliary side is 5 and Fig. 0 shows the voltage of flyback converter is 50. Fig. shows the inverted voltages having seven levels of ac voltages. Fig.0. oltage of Flyback [] Rong Jong Wai and Kun- Huai Jheng, High efficiency single input multiple output DC-DC converter, IEEE Trans. Power Electron.., vol. 8, no., pp , Feb. 03. [] C.T. Pan, M. C. Cheng, and C.M. Lai, A novel integrated dc/ac converter with high voltage gain capability for distributed energy resource systems, IEEE Trans. Power Electron., vol. 7, no. 5, pp , May 0. [3] S. D. Gamini Jayasinghe, D. Mahinda ilathgamuwa, and U. K. Madawala, Diode-clamped three-level inverter-based battery/ supercapacitor direct integration scheme for renewable energy system s, IEEE Trans. Power Electron., vol. 6, no. 6, pp , Dec. 0. [4] H.Wu, R. Chen, J. Zhang, Y. Xing, H. Hu, and H. Ge, A family of three port half-bridge converters for a stand-alone renewable power system, IEEE Trans. Power Electron., vol. 6, no. 9, pp , Sep. 0. [5] P. Patra, A. Patra, and N. Mishra, A single-inductor multiple output switcher with simultaneous buck, boost and inverted outputs, IEEE Trans. Power Electron.., vol. 7, no. 4, pp , Apr. 0. [6] A. Nami, F. Zare, A. Gosh, and F. Blaabjerg, Muliple Output DC-DC converters based on diode clamped converter configurations, IET Power Electron., vol. 3, no., pp , 00. [7] Y. Chen. Y. Kang, S. Nie, and X. Pei, The multiple-output DC-DC converter with shared ZCS lagging leg, IEEE Trans. Power Electron.., vol. 6, no. 8, pp , Aug. 0. [8] N. Mohan, T. M. Undeland, and W.P. Robbins, Power Electronics: s, Applications, and, Design. New York: Wiley, 995. [9] S. H. Cho, C. S. Kim, and S. K. Han, High efficiency and low-cost tightly regulated dual-output LLC resonant converter, IEEE Trans. Ind. Electron.,vol. 59, no. 7 pp , Jul. 0. [0] M. F Kangarlu and Ebrahim Babaei, A generalized cascaded multilevel inverter using series connection of submultilevel inverter, IEEE Trans. Ind. Electron.,vol., no. pp , Feb. 03. Fig.. Output oltage of the Inverter I. CONCLUSIONS The proposed high efficiency SIMO DC-DC converter is a coupled inductor based converter which can be well applied to Single input power source plus output terminals composed of an auxiliary battery module, a high voltage dc bus, another controllable dc voltage and different levels of ac voltages. The major contribution of the proposed SIMO converter are specified as follows: i) the voltage gain can be substantially increased by using a coupled inductor; ii) the stray energy can be recycled by a clamped capacitor into the