Research of Switched Inductor Boost Converter Based on Topology Combination

Transcription

1 2017 2nd International Seminar on Applied Physics, Optoelectronics and Photonics (APOP 2017) ISBN: Research of Switched Inductor Boost Converter Based on Topology Combination Zhuo JING, Song GAO, Chao-bo CHEN, Shen-hao GAO ABSTRACT According to the voltage gain of boost converter at the photovoltaic inverter system, a high gain switched inductor boost converter is proposed in this paper by analyzing and studying the voltage gain ability of traditional switched inductor boost converter which improves the switched inductor three-terminal network topology. The working principle and working characteristics of the designed boost topology are analyses in detail, and the corresponding mathematical model is established. Compared with the traditional converter, the proposed converter has some advantages which improving the boost ability and decreasing the voltage stress of the switch tube. Moreover, the simulations are shown to verify the correctness of the theoretical analysis. INTRODUCTION Recently, the renewable energy resources are increasingly used to produce energy. Solar energy can be considered as the best renewable energy because of the earth surface receives an amount of solar energy which is more than the world energy demand. As a result, solar cells and solar power generation becomes the popular topics which addressed by many researches and projects 1,2, and the high-gain DC-DC converter as a key composition in photovoltaic system has been extensively used and researched 3,4. The traditional switched inductor boost converter 5 has the characteristics of small inductor in size, mutual symmetry and the large gain enhancement space compared to the boost converter. However, the input gain is limited, and the power switch voltage stress is equal to the output voltage which has high power switch conduction loss. Furthermore, the voltage stress produced by the output diode is equal to the output voltage which results more serious problem of the reverse recovery. In order to improve the above disadvantages of switched inductor boost converter, the literature 6 proposed to add the coupling inductor and clamp circuit to improve the voltage gain, but the leakage inductance affect the conversion efficiency, increase the voltage stress of power switch, and electro magnetic interference(emi) problem are more serious. This paper improved the switching inductor three-terminal network, and proposed a switched inductor boost converter based on the topology combination which has high voltage gain and small power stress of the power switched tube. Finally, the paper analyses the working principle of the proposed boost converter, and verifies the correctness of the theoretical analysis by circuit simulation. Zhuo JING 1, Song GAO 1, *, Chao-bo CHEN 1 and Shen-hao GAO 1 1 School of Electronic Information Engineering, Xi an Technological University, , Xi an, China Corresponding author: gaos@xatu.edu.cn 329

2 SWITCHED INDUCTOR BOOST CONVERTER The traditional switched inductor boost converter is shown in Fig.1. (Switched Inductor Boost Converter, SIBC) Figure 1. Switched inductor boost topology. The operating principle of the SIBC is similar to that of the boost converter. 7 By controlling the turn-on and turn-off of the switching device SW1, the duty cycle is adjusted to achieve the purpose of boost, and the boost gain is higher than that of the conventional boost converter. It should be noted that the inductance values of L 1 and L 2 are equal, which ensures that the inductor in parallel charging and series discharging process voltage value is equal, that is L + L = L 1 2 u + u = u L1 L2 L The equivalent structure of the SIBC is shown in Fig.2. (1) (a) SW1 turns on (b) SW1 turns off (c) SW1 and diodes are off Figure 2. Equivalent circuit of the SIBC. By analysing the switching state of the equivalent circuit, assuming that the switching period of the switching device SW1 is T, the on-time is T 1, the turn-off time is T 2, and T 1 + T 2 =T, the duty cycle is D=T 1 / T. According to the average of the inductor L 1 and L 2 in a switching cycle time is 0, can obtain: Vin Vo DVin + (1 D) = 0 (2) 2 After simplification, get the following formula: 1+ D Vo = Vin (3) 1 D When the SIBC operated in the inductor current continuous conduction mode (CCM), the voltage gain 8 G 1 is: 1+ D G1 = (4) 1 D SWITCHED INDUCTOR BOOST CONVERTER BASED ON TOPOLOGICAL COMBINATION In this paper, three kinds of high-gain switched inductor three-terminal networks are obtained by series-connected voltage source in the branch of SIBC. After analysing, the circuit in Fig.3 (a) is selected which reduces the voltage stress of the active switch tube 330

3 SW1 and the diode VD while maintaining a high voltage gain. And used a large capacity capacitor C c instead of the voltage source u c, added a branch to provide the charging current, finally obtained the high-gain switched inductor three-terminal network based on topological combination shown in Fig.3 (b). (a) (b) Figure 3. High-gain switched inductor three-terminal network. The topology of the improved SIBC based on the topology combination is shown in Fig.4. Compared with the interleaved parallel boost converter 9, the improved topology can realize current sharing automatically, the control circuit is simple which does not require current-sharing control. Figure 4. Switched inductor boost circuit based on topology combination. The following assumptions are made before analysing the working principle: (1) the inductors L 1, L 2, L 3 are operated in the current continuous conduction mode. (2) Capacitors C 1 and C 2 are large enough to keep their voltage constant; (3) all devices are ideal devices with no parasitic parameters. As the general requirements of the gain is greater than 4 occasions only use boost circuit, this paper focuses on the switch duty cycle D> 0.5, Fig.5 is an equivalent circuit diagram when the state is D> 0.5. (a) Working state 1 (b) Working state 2 (c) Working state 3 Figure 5. Equivalent circuit diagram when D> 0.5. It can be seen that when D> 0.5, in the first state, the power supply DC charged to the inductor L 1, L 2, L 3 respectively in parallel, and the load is supplied by capacitor C 1. The second state is the most critical part where connects the power supply in series with the inductor L 3 to charge the capacitor, the voltage is equal to the sum of the power supply and the inductor voltage after charging, and at this time, the load is still supplied by capacitor C 1. The third state is the inductors L 1, L 2 discharging state, the DC power supply, L 1, L 2 and C 2 are connected in series to load power supply, and to charge C

4 PERFORMANCE ANALYSIS Voltage Gain In order to obtain the voltage gain of the circuit, it is necessary to calculate the inductor L 1 and L 2 according to the volt-second balance principle, and get the formula (5). Since the inductor L 1 is exactly the same as L 2, it is only need to calculate the L 1. (1 D) Ts ( Uin + Uc Uo) DTs Uin + = 0 (5) 2 Finished: (1 + D) Uin = ( Uo Uc)(1 D) (6) According to the principle of volt-second balance to calculate the L 3, get the following formula: U (1 ) in = Uc D (7) Take formula (7) into (6) can be obtained: Uin (1 + D) Uin = ( Uo )(1 D) (8) 1 D Finished: Uo 2 + D G2 = = (9) U in 1 D G 2 is the voltage gain of switched inductor boost converter based on the topology combination. Switch Tube Voltage Stress The voltage stress of switch tube S 1, S 2 and diode VD1, VD2 are: Us 1 = Uds 1 = Uo Uc2 (10) Us2 = Uc2 (11) Uds2 = Uo (12) It can be seen from the equation (10) that the voltage stress of the switch S1 is the output voltage U o - U c2, while the voltage stress of switch device in the traditional boost circuit or the switched inductor boost circuit is the output voltage U o. The voltage stress of the switch S 2 is U c2 which is far less than the U o according to the above analyses. It was found that the proposed topology effectively reduces the voltage stress of the main switching device S 1. SIMULATION ANALYSIS The simulation parameters are as follows: the input voltage V in = 10V, the inductor L 1 = L 2 = L 3 = 1mH, the output end of the capacitor C 1 = 4.7µF, C 2 = 3.3µF, the load resistor R = 10Ω, the duty cycle of switches S 1 and S 2 are equal (D 1 = D 2 = 0.6). The converter designed in this paper is compared with SIBC, and the following simulation results are obtained. (1) The output voltage comparison: Fig.8 is the comparison chart of the output voltage V o between SIBC and the switched inductor boost converter based on topology combination. It can be seen that when the input voltage is 10V, the SIBC output voltage is about 30V, and the switched inductor boost converter based on topology combination output voltage can reach about 65V in the same duty cycle. The simulation results of 332

5 voltage gain are consistent with the previous theoretical analysis, which proved that the designed converter has higher voltage gain. 80 output voltage Vo(V) switched inductor Boost converter based on topology combination switched inductor Boost converter Time t(s) Figure 8. The output voltage comparison. (2) Power switch voltage stress comparison: the following switch on the voltage stress analysis is still compared with the SIBC. This comparison has compared the output side of the capacitor voltage stress when the output voltage is the same. The comparison results are shown in Fig.9 and Fig voltage stress Us1(V) Figure 9. The voltage stress at S1 when the voltage is 65V. Figure 10. SIBC power switch voltage stress. It can be seen from Fig.9 and Fig.10 that when the output voltage is 65V, the voltage of the SIBC power switch tube is 65V, which is equal to the output voltage, while the voltage stress of the proposed switched inductor boost converter power switch S1 is 40V and the voltage stress is reduced 20V, which not only reduces the switching moment of the switching losses, but also expands the power switch device selection. SUMMARY Voltage Stress of SIBC Switch tube(v) Time t(s) The basic principle of switched inductor boost converter is studied and analysed in this paper. On this basis, the switched inductor three-terminal network of switched inductor boost converter is improved, and a switched inductor boost converter based on topological combination is designed. The mathematical model of the designed converter is obtained by analysis and calculation. The correctness and feasibility of the proposed converter is further verified by simulation analysis. Compared with the conventional switched inductor boost converter, the proposed converter has the following Time t(s) 333

6 characteristics when the switching duty ratio D> 0.5: firstly, the boost capability is doubled; secondly, the voltage stress of the active switch is reduced about 35%; finally, the boost unit can realize current sharing automatically, and the control circuit is simple which does not require current-sharing control. ACKNOWLEDGEMENT This research was financially supported by the International Science and Technology Innovation Cooperation between Governments Project of National Key Research and Development Program (2016YFE ), the International Science and Technology Cooperation Key Project of Shaanxi Province (2016KW-062) and Xi'an Weiyang District Science Technology Bureau Project (201610). REFERENCES 1. Pujol, L., et al. Outdoor Characterization and Performance Evaluation of Integra Sun Prototype CPV Module. Methods in Enzymology (2010): Law, Daniel C., et al. Future technology pathways of terrestrial III V multijunction solar cells for concentrator photovoltaic systems. Solar Energy Materials & Solar Cells 94.8(2010): Li, Wuhua, et al. Interleaved High Step-Up Converter with Winding-Cross-Coupled Inductors and Voltage Multiplier Cells. IEEE Transactions on Power Electronics 27.1(2011): Li, Wuhua, et al. High-Step-Up and High-Efficiency Fuel-Cell Power-Generation System with Active-Clamp Flyback Forward Converter. IEEE Transactions on Industrial Electronics 59.1(2011): Abdel-Rahim, Omar, et al. Switched inductor boost converter for PV applications. Applied Power Electronics Conference and Exposition IEEE, 2012: Luo Quanming, Zhang Yang, Yan Huan, et al. An active-clamp high step-up boost converter with coupled-inductor. Proceeding of the CSEE, (2014): Saitoh, Mitsuyori. DC-DC boost converter. US, US Chang, Yuen Haw, and Y. J. Chen. High-Gain Switched-Inductor Switched-Capacitor Step-Up DC-DC Converter. Lecture Notes in Engineering & Computer Science (2013): Kolluri, Sandeep, and N. L. Narasamma. Analysis, modeling, design and implementation of average current mode control for interleaved boost converter. IEEE, International Conference on Power Electronics and Drive Systems IEEE, 2013: