ISSN 2348 2370 Vol.07,Issue.11, August-2015, Pages:2108-2114 www.ijatir.org A New Bidirectional Soft Switching DC-DC Converter using PID Controller P. RAMANA REDDY 1, Y. PERAIAH 2 1 PG Scholar, Dept of EEE, Shree Institute of Technology, A.P, India, 2 Assistant Professor, Dept of EEE, Shree Institute of Technology, A.P, India, Abstract: A soft-switching bidirectional dc-dc converter using a lossless active snubber is proposed in this paper. In the proposed converter, zero-voltage-switching (ZVS) of main switches is achieved by utilizing an active snubber which consists of auxiliary switches, diodes, an inductor, and a capacitor. Although conduction losses associated with additional components increase, switching losses are significantly reduced due to the ZVS operation of main switches. Therefore, total efficiency is improved. Moreover, there is no reverse-recovery problem of the intrinsic body diodes of the switches. The simulation is carried over by the MATLAB-SIMULINK software. Keywords: Bidirectional Dc-Dc Converter, Lossless Active Snubber, Zero-Voltage-Switching. I. INTRODUCTION In recent years, alternative energy systems and applications like eco-friendly cars have been focused on due to the exhaustion of fossil fuel and severe environmental pollution. Bidirectional dc-dc converters are one of the most important energy conversion system in the applications such as plug-in hybrid electric vehicle (PHEV), fuel-cell vehicle, renewable energy system, and uninterruptible power supply (UPS). In PHEV system, the bidirectional dc-dc converter acts as an energy transfer system from a low voltage battery to a DC-link that is an input voltage of an inverter for operating a vehicle motor, or from a DC-link to a battery for charging regenerative energy. Soft-switching bidirectional dc-dc is a converter that achieves ZVS of switches by simply adding an auxiliary inductor and a capacitor. Disadvantage of this converter is that large circulating current always flows through an auxiliary inductor and a capacitor for satisfying soft-switching of switches, irrespective of load. So, high conduction losses are induced from resistance of an auxiliary inductor, a capacitor, a printed circuit board (PCB), and switches. To overcome this problem, a softswitching bidirectional dc-dc converter using a lossless active snubber is proposed. converter. On the other hand, the non-isolated bidirectional dc-dc converter has high efficiency due to simple structure. Recently, soft-switching techniques are applied to the nonisolated bidirectional dc-dc converter to achieve softswitching of power switches in a wide range of load and reduce switching noises. Soft-switching technique makes it possible to have high efficiency by reducing switching losses and it is necessary for miniaturization and light weight Softswitching operation of the main switch is achieved by utilizing an auxiliary circuit consisting of an additional switch, an additional diode, a resonant capacitor, and a resonant inductor. The ZVS of the main switch is achieved. However, the auxiliary circuit makes the output current ripple large. In addition, the energy stored in the resonant inductor during the reverse-recovery of the auxiliary diode can cause large voltage ringing across the switch and diode in snubber circuit. In order to suppress the voltage ringing, additional passive snubbers are required and it will degrade system performance. Softswitching bidirectional dc-dc is a converter that achieves ZVS of switches by simply adding an auxiliary inductor and a capacitor. Disadvantage of this converter is that large circulating current always flows through an auxiliary inductor and a capacitor for satisfying soft-switching of switches, irrespective of load. So, high conduction losses are induced from resistance of an auxiliary inductor, a capacitor, a printed circuit board (PCB), and switches. III. PROPOSED SYSTEM TECHNIQUE To overcome this problem, a soft-switching bidirectional dc-dc converter using a lossless active snubber is proposed. the total amount of the current flowing through the auxiliary circuit decreases significantly since the active snubber operates during short time intervals. Therefore, conduction losses in main switches and auxiliary circuit are significantly reduced and thus overall efficiency is improved. A. Bidirectional Converter Soft-switching bidirectional dc-dc is a converter that achieves ZVS of switches by simply adding an auxiliary inductor and a capacitor. Disadvantage of this converter is that large circulating current always flows through an auxiliary inductor and a capacitor for satisfying soft-switching of switches, irrespective of load. So, high conduction losses are induced from resistance of an auxiliary inductor, a capacitor, a printed circuit board (PCB), and switches. To overcome this The bidirectional dc-dc converter is divided into an isolated type and a non-isolated type. Because an isolated bidirectional dc-dc converter has more than 4 switches and an isolated transformer, it has higher conduction losses and lower efficiency than a non-isolated bidirectional dc-dc problem, a soft-switching bidirectional dc-dc converter using Copyright @ 2015 IJATIR. All rights reserved.
a lossless active snubber is proposed. the total amount of the current flowing through the auxiliary circuit decreases significantly since the active snubber operates during short time intervals. Therefore, conduction losses in main switches and auxiliary circuit are significantly reduced and thus overall efficiency is improved. P. RAMANA REDDY, Y. PERAIAH acts as a synchronous switch in boost operation and as a buck switch in buck operation. The lossless active snubber, which consists of an auxiliary inductor L2, an additional capacitor Ca, blocking diodes D1 and D2, and auxiliary switches S3 and S4, is added into the conventional bidirectional dc-dc converter. In order to minimize the conduction loss in the active snubber and provide soft-switching operation of the main switches S1 and S2, the lossless active snubber operates during short time intervals. The diodes DS1, DS2,DS3 and DS4 are the intrinsic body diodes of S1, S2, S3 and S4. The diodes D3 and D4 are clamping diodes to clamp the voltages across the auxiliary switches and the blocking diodes in the snubber circuit. The capacitors CS1 and CS2 represent the parasitic output capacitances of S1 and S2. Assuming that the capacitance of Ca is large enough, Ca can be considered as a voltage source Vca during a switching period. Fig1. Proposed Bidirectional DC-DC Converter. B. Boost Operation Before, the switches S2 and S4 are conducting. The inductor currents i L1 and i L2 decrease linearly and reach their minimum values I m2 and I s2 respectively at t0. Since the current I s2 is larger than I m2, the switch current I s2 changes the current flow direction from negative to positive. While Boost operation carried out, the converter input is low voltage and the output will be high voltage at other end. C. Buck Operation The buck operation of the proposed converter is similar to the boost operation except that the main inductor current i L1 and the switch currents i S1, i S2 have the opposite direction of those in boost operation. Before t0, the switches S2 and S4 are conducting. At t0, the inductor currents i L1 and i L2 are decreasing linearly and reach their minimum values I m1 and I s2, respectively. D. Soft Switching When we make soft switching circuits we start out with hard switching circuit and than add circuitry (power components) to make it soft. Soft means to achieve smooth current /voltage transitions in the switching moment. By hard Switching we simply means that no special circuitry is added to make the circuit soft. In order to get smooth transitions, the fundamental principle for all Soft Switching techniques is to switch in a moment at zero voltage and zero current, in the main switching devices. At high switching frequency soft switching techniques (ZVS or ZCS) are used to achieve good efficiency and reduced switching stress. In Zero-Voltage Switching (ZVS), the voltage across device is zero just before turn on. On the other hand in Zero-Current Switching (ZCS), the current through device is zero just before turn-off. III. BOOST OPERATION Mode1: The switch S2 is turned off at t0. The parasitic output capacitor Cs1 starts to discharge and Cs2 begins to charge. Assuming that the parasitic output capacitors Cs1 and Cs2 have very small capacitance and the time interval in this mode is very short, the inductor currents il1 and il2 can be regarded as constant and the voltages Vs1 and Vs2 vary linearly. Fig2. Mode1. Mode 2: At t1, the voltage vs2 arrives at Vhi and vs1 reaches zero with the turn-on of Ds1. Since the switch voltage vs1 is zero before the gate pulse of s1 is applied, the ZVS of S1 is achieved. Since the voltages Vl1 and Vl2 across the each inductor are Vlo and Vca respectively, the inductor currents il1 and il2 increase linearly. The circuit diagram is shown below. E. Operation of the Converter The switch S1 acts as a boost switch in boost operation and a synchronous switch in buck operation. The switch S2 Fig3. Mode2.
A New Bidirectional Soft Switching DC-DC Converter using PID Controller Mode3: This mode begins when the inductor current il2 becomes zero and the blocking diode D2 is turned off. After that, the auxiliary switch S4 is turned off in the zerocurrent switching (ZCS) condition. The switch current is1 is equal to the main inductor current il1. the ZVS of S2 is achieved. Since the voltages Vl1 and Vl2 across the each inductor are (Vhi-Vlo) and (Vhi-Vca) respectively, the inductor currents il1 and il2 decrease linearly. Fig4. Mode3. Mode4: At t3, the auxiliary switch S3 is turned on. Since the voltage vl2across the inductor L2 is Vca, the inductor current il2 increases linearly with a slope of Vca/L2. At the end of this mode, the inductor currents il1 and il2 arrive at their maximum values Im1 and Is1, respectively. Fig7. Mode6. Mode 7: This mode begins when il2 becomes zero and the blocking diode D1 is turned off. After that, the auxiliary switch S3 is turned off in the ZCS condition. The switch current is2 is equal to the main inductor current il1. Fig8. Mode7. Fig5. Mode4. Mode 5: The switch S1 is turned off at t4. The parasitic output capacitor Cs1 starts to charge and Cs2 begins to discharge. Assuming that the parasitic output capacitors Cs1 and Cs2 have very small capacitance and the time interval in this mode is very short, the inductor currents il1 and il2 can be regarded as constant and the voltages Vs1 and Vs2 vary linearly. Mode 8: At t7, the auxiliary switch S4 is turned on. Since the voltage vl2 across the inductor L2 is -(Vhi-Vca), the inductor current il2 decreases linearly with a slope of (Vhi-Vca)/L2. At the end of this mode, the inductor currents il1 and il2 arrive at their minimum values Im2 and Is2 respectively. Fig6. Mode5. Mode 6: At t5, the voltage Vs1 arrives at Vhi and Vs2 reaches zero with the turn-on of Ds2. Since the switch voltage Vs2 is zero before the gate pulse of S2 is applied, Fig9. Mode8. IV. BUCK MODES OF OPERATION In this mode of operation the output voltage is absolutely decreases at the rate od duty cycle ratio. To obtain this range of voltages following modes of operations have to be done.
Mode 1: The switch S2 is turned off at t0. In a similar way to mode 1 in boost operation, the switch voltages Vs1 and Vs2 vary linearly. P. RAMANA REDDY, Y. PERAIAH the end of this mode, the inductor currents il1 and il2 arrive at their maximum values Im1 and Is1, respectively. Fig13. Mode4. Fig10. Mode1. Mode 2: At t1, the voltage Vs2 arrives at Vhi and Vs1 reaches zero with the turn-on of Ds1. In a similar way to mode 2 in boost operation, the ZVS of S1 is achieved. Since the voltages Vl1 And Vl2 across the each inductor are Vl0 and Vca respectively, the inductor currents il1and il2 increase linearly. Mode 5: The switch S1 is turned off at t4. The parasitic output capacitor Cs1 starts to charge and Cs2 begins to discharge. Assuming that the parasitic output capacitors Cs1 and Cs2 have very small capacitance and the time interval in this mode is very short, the inductor currents il1 and il2 can be regarded as constant and the voltages Vs1 and Vs2 vary linearly. Fig14. Mode5. Fig11. Mode2. Mode 3: This mode begins when il2 becomes zero and the blocking diode D2 is turned off. After that, the auxiliary switch S4 is turned off in the ZCS condition. The switch current is1 is equal to the main inductor current il1. Mode 6 : At t5, the voltage Vs1 arrives at Vhi and Vs2 reaches zero with the turn-on of Ds2. In a similar way to mode 6 in boost operation, the ZVS of S2 is achieved. Since the voltages Vl1 and Vl2 across the each inductor are (Vhi-Vlo) and (Vhi-Vca) respectively, the currents il1 and il2 decrease linearly. Fig12. Mode3. Mode 4: At t3, the auxiliary switch s3 is turned on. Since the voltage Vl2 across the inductor L2 is Vca, the inductor current il2 increases linearly with a slope of Vca/L2. At Fig15. Mode6. Mode 7: This mode begins when il2 becomes zero and the blocking diode D1 is turned off. After that, the auxiliary
A New Bidirectional Soft Switching DC-DC Converter using PID Controller switch S3 is turned off in the ZCS condition. The switch current is2 is equal to the main inductor current il1. Fig16. Mode7. Mode 8: At t7, the auxiliary switch S4 is turned on. Since the voltage Vl2 across the inductor L2 is (Vhi-Vca), the inductor current il2 decreases linearly with a slope of (Vhi-Vca)/L2. At the end of this mode, the inductor currents il1 and il2 arrive at their minimum values -Im1 and Is2 respectively Fig19. Switching Sequence S1, S2, S3, S4 for both buck & Boost mode. Fig17. Mode8. V. SIMULATION RESULTS We can simulate the dynamic behavior of the system and view the results as the simulation runs. To ensure simulation speed and accuracy, Simulink provides fixedstep and variable-step ODE solvers, a graphical debugger, and a model profiler Fig20. Buck Mode. Fig18. Boost Mode Vin=48V Vout=100V. Fig21. Output voltage for buck mode.
Fig22. Closed loop for bidirectional converter (Buck Mode). Fig23. Output voltage of Buck Converter in closed loop mode VI. CONCLUSION In this paper, a soft-switching bidirectional dc-dc converter using a lossless active snubber has been proposed. In the proposed converter, ZVS of the main switches and ZCS of the auxiliary switches are always achieved. In addition, by utilizing the active snubber, there is no reverse-recovery problem of the intrinsic body diodes of the switches. Since the active snubber operates in a short time, the increased conduction loss of the proposed converter is relatively lower than the soft-switching bidirectional converter in Fig. 1. Thus, the overall efficiency improvement is achieved over a wide range of load. At light load, the conduction loss can be reduced and the efficiency can be improved by reducing VII. REFERENCES [1] S. Haghbin, S. Lundmark, M. Alakula, and O. Carlson, Grid-connected integrated battery chargers in vehicle applications review and new solution, IEEE Trans. Ind. Electron., vol. 60, no. 2, pp. 459 473, Feb. 2013. [2] J. Cao and A. Emadi, A new battery/ ultra capacitor hybrid energy storage system for electric, hybrid, and plugin hybrid electric vehicles, IEEE Trans. Ind. Electron., vol. 27, no. 1, pp. 122 132, Jan. 2012. P. RAMANA REDDY, Y. PERAIAH [3] T. Park and T. Kim, Novel energy conversion system based on a multimode single-leg power converter, IEEE Trans. Power Electron., vol.28, no. 1, pp. 213 220, Jan. 2013. [4] M. Jang, M. Ciobotaru, and V. G. Agelidis, A singlephase grid-connected fuel cell system based on a boostinverter, IEEE Trans. Power Electron., vol. 28, no. 1, pp. 279 288, Jan. 2013. [5] W. Li, H. Wu, H. Yu, and X. He, Isolated windingcoupled bidirectional ZVS converter with PWM plus phaseshift (PPS) control strategy, IEEE Trans. Power Electron., vol. 26, no. 12, pp. 3560 3570, Dec. 2011. [6] M. Rolak and M. Malinowski, Dual active bridge for energy storage system in small wind turbine, in Proc. AFRICON, 2011, pp. 1 5. [7] S. D. G. Jayasinghe, D. M. Vilathgamuwa, and U. K. Madawala, Diode-clamped three-level inverter-based battery/super- capacitor direct integration scheme for renewable energy systems, IEEE Trans.Power Electron., vol. 26, no. 12, pp. 3720 3729, Dec. 2011. [8] M. Arias, M. M. Hernando, D. G. Lamar, J. Sebastián, and A. Fernández, Elimination of the transfer-time effects in lineinteractive and passive standby UPSs by means of a small-size inverter, IEEE Trans Ind. Electron., vol. 27, no. 3, pp. 1468 478, Mar. 2012. [9] C. Yao, X. Ruan, X.Wang, and C. K. Tse, Isolated buckboost DC/DC converters suitable for wide input-voltage range, IEEE Trans. Power Electron., vol. 26, no. 9, pp. 2599 2613, Sep. 2011. [10] J.-Y. Lee, Y.-S. Jeong, and B.-M. Han, An isolated DC/DC converter using high-frequency unregulated resonant converter for fuel cell applications, IEEE Trans. Ind. Electron., vol. 58, no. 7, pp. 2926 2934, Jul. 2011. [11] D. Vinnikov and I. Roasto, Quasi-Z-source-based isolated DC/DC converters for distributed power generation, IEEE Trans. Ind. Electron., vol. 58, no. 1, pp. 192 201, Jan. 2011. [12] T.-F. Wu, Y.-C. Chen, J.-G. Yang, and C.-L. Kuo, Isolated bidirectional full-bridge DC-DC converter with a flyback snubber, IEEE Trans. Power Electron., vol. 25, no. 7, pp. 1915 1922, Jul. 2010. [13] R. K. Singh and S. Mishra, Amagnetically coupled feedback-clamped optimal bidirectional battery charger, IEEE Trans. Ind. Electron., vol. 60, no. 2, pp. 422 432, Feb. 2013. [14] H.Wu, J. Lu, W. Shi, and Y. Xing, Nonisolated bidirectional DC-DC converters with negative-coupled inductor, IEEE Trans. Power Electron., vol. 27, no. 5, pp. 2231 2235, May 2012. [15] P. Das, S. A. Mousavi, and G. Moschopoulos, Analysis and design of a nonisolated bidirectional ZVS-PWM DC-DC converter with coupled inductors, IEEE Trans. Power Electron., vol. 25, no. 10, pp. 2630 2641, Oct. 2010. [16] P. Das, B. Laan, S. A.Mousavi, and G. Moschopoulos, A nonisolated bidirectional ZVS-PWM active clamped DC- DC converter, IEEE Trans. Power Electron., vol. 24, no. 2, pp. 553 558, Feb. 2009. [17] H.-L. Do, Nonisolated bidirectional zero-voltageswitching DC-DC converter, IEEE Trans. Power Electron., vol. 26, no. 9, pp. 2563 2569, Sep. 2011.
A New Bidirectional Soft Switching DC-DC Converter using PID Controller [18] D.-Y. Jung, S.-H. Hwang, Y.-H. Ji, J.-H. Lee, Y.-C. Jung, and C.-Y. Won, Soft-switching bidirectional DC/DC converter with a LC series resonant circuit, IEEE Trans. Power Electron., vol. 28, no. 4, pp. 1680 1690, Apr. 2013. [19] B.-R. Lin and C.-H. Chao, Analysis, design, and implementation of a soft-switching converter with two three-level PWM circuits, IEEE Trans. Power Electron., vol. 28, no. 4, pp. 1700 1710, Apr. 2013. [20] I.-O. Lee and G.-W. Moon, Soft-switching DC/DC converter with a full ZVS range and reduced output filter for high-voltage applications, IEEE Trans. Power Electron., vol. 28, no. 1, pp. 112 122, Jan. 2013. Author s Profile: P. Ramana Reddy born in Andhra Pradesh, India. He received his bachelor degree in electrical and electronics engineering (EEE) in 2012 from Jntu Anantapur. He is currently pursuing his master of technology on power electronics and drives (Pe&D) in Shree institute of technology Tirupati Andhra Pradesh. His research interest includes on power electronic devices and their application in power systems. Y. Peraiah received B.Tech degree EEE in 2011, M.Tech degree in 2013 and currently working as an Asst.Professor in Department of EEE, Shree Institute Of technology, Tirupati, Andhra Pradesh, India