CONTROL OF COMBINED KY AND BUCK-BOOST CONVERTER WITH COUPLED INDUCTOR

Transcription

1 International Journal of Scientific Engineering and Applied Science (IJSEAS) - Volume-1, Iue-7,October 015 COTROL OF COMBIED KY AD BUCK-BOOST COVERTER WITH COUPLED IDUCTOR OWFALA A 1, M AASHIF 1 MEA EGIEERIG COLLEGE, PERITHALMAA, KERALA, IDIA MEA EGIEERIG COLLEGE, PERITHALMAA, KERALA, IDIA Abtract In thi paper a voltage-booting converter i preented, which combine one KY converter and one ynchronouly rectified buck-boot converter. The correponding voltage gain i greater than that of the exiting tep-up converter. It overcome all the diadvantage of older converter. It ha added advantage uch a it output terminal ha got inductor thu making output free from ripple. More over it energy lot in the leakage inductor i replaced to the output capacitor. It alo contain one charge pump and coupled inductor with turn ratio. Since the propoed converter poee an output inductor and output capacitor the output current i no pulating and voltage i free from ripple. The propoed converter i firt modeled with PI Controller. For better ytem dynamic performance converter i modeled with Fuzzy Logic Controller. The propoed converter give output voltage of 7 V from 1 V DC. The fundamental output frequency wa 50 Hz and the witching frequency wa 100 khz. The experiment reult of two control method how that fuzzy control method need much le time to reach teady tate than that of PI control.. Keyword: Coupled inductor, Magnetizing inductor, Charge pump,energy tranferring capacitor. 1. Introduction Thi converter combine one KY converter, one traditional ynchronouly rectified (SR) buck-boot converter, and one coupled inductor with the turn ratio, which i ued to improve the voltage gain. Therefore, the voltage gain i higher than that of the converter in and can be determined by adjuting both the duty cycle and the turn ratio. Moreover, the duty cycle and the turn ratio are independent, which mean that tuning the duty cycle doe not affect the turn ratio and vice vera. In addition, the propoed tep-up converter ha no floating output and ha an output inductor; hence, the output current i non pulating. Furthermore, part of the leakage inductance energy can be recycled to the output capacitor of the SR buck-boot converter. In thi paper, a detailed decription, along with ome experimental reult, i given to provide the effectivene of the propoed converter. Fig.1. Propoed tep-up converter Fig.1. how the propoed converter, which contain two MOSFET witche S 1 and S, one coupled inductor compoed of the primary winding with p turn and the econdary winding with turn, one energy-tranferring capacitor C 1, one charge pump capacitor C, one diode D 1, one output inductor L o, and one output capacitor C o. In addition, the input voltage i denoted by V i, the output voltage i 43

2 ignified by V o, and the output reitor i repreented by R o. Aumption to be made are: 1) The coupled inductor i modeled a an ideal tranformer except that one magnetizing inductor L m i connected in parallel with the primary winding and one leakage inductor L l1 i connected in erie with the primary winding. Therefore, coupling coefficient k i defined a L m /(L m + L l1 ). ) The propoed converter operate in the poitive current mode. That i, the current flowing through the magnetizing inductor L m and the output inductor L o are alway poitive. 3) The dead time between the two MOSFET witche are omitted. The MOSFET witche and the diode are aumed to be ideal component. 4) The value of all the capacitor are large enough uch that the voltage acro them are kept contant at ome value. 5) The magnitude of the witching ripple i negligible. Therefore, the mall ripple approximation will be adopted herein in the analyi. A. Voltage Gain Conidering Coupling Coefficient Equal to One B. Voltage Gain Conidering Coupling Coefficient ot Equal to One. Baic Operating Principle The following analyi contain the explanation of the power flow path for each mode, along with the correponding equation and voltage gain. Inherently, there are two operating mode in the propoed converter. Moreover, the gate driving ignal v g1 and v g of the two witche S 1 and S have the duty cycle of (1 D) and D, repectively, where D i the dc quiecent duty cycle created from the controller. In addition, the input current i denoted by i i, the current through the p winding i ignified by i p, the current through the winding i repreented by i, the current through L m i denoted by i Lm, the current through L o i indicated by i Lo, and the current through R o i ignified by I o. On the other hand, the voltage acro L m or the voltage acro the p winding i ignified by V p, the voltage acro the winding i repreented by V, the voltage acro C 1 i indicated by V C1, the voltage acro C i denoted by V C, and the voltage acro L o i decribed by V Lo. It operation i analyzed in two way: Mode 1 Mode Fig.. Key waveform of the propoed converter. 44

3 A. Voltage Gain Conidering Coupling Coefficient Equal to One Fig.3. Power flow in mode 1 with coupling coefficient equal to one. Mode 1: During thi interval, a hown in Fig.3., S 1 i turned off but S i turned on. Therefore, input voltage V i i impoed on p, thu cauing L m to be magnetized and the voltage acro to be induced, equal to V i / p. In addition, D 1 become forward-biaed; C i charged to V i + V C1 + V i / p ; and the voltage acro L o, i.e., V Lo, i a negative value, equal to V C V o, thu making L o demagnetized. A a conequence, input voltage V i, together with the voltage acro C 1 (V C1 ), plu the induced voltage on (V ), plu the voltage acro L o (V Lo ), provide the energy to the load. In addition, the aociated equation are a follow: VP (1) VLo VC Vo () Fig.4. Power flow in mode with coupling coefficient equal to one. Mode : During thi interval, a hown in Fig.4. S 1 i turned on but S i turned off. Therefore, the V C1 voltage i impoed on p, thereby cauing the magnetizing inductor L m. to be demagnetized and the voltage acro to be induced, equal to V C1 / p. In addition, D 1 become revere biaed, the voltage on L o i a poitive value, equal to V i +V C1 + V C V o, thu cauing L o to be magnetized. A a reult, the input voltage V i, together with the voltage acro L m (V p ),plu the voltage acro C (V C ), provide the energy to L o and the load. In addition, the correponding equation are a follow: Vp VC1 (3) VLo Vc1 Vc Vo (4) By applying the voltage-econd balance principle to L m over one witching period, the following equation can be obtained: 1 D V C 1 D 0 (5) In addition, by rearranging the above equation, the voltage acro C 1, i.e., V C1, can be obtained a follow: Vc1 D 1 D (6) Likewie, by applying the voltage-econd balance principle to Lo over one witching period, the following equation can be obtained: (VC V0) D ( VC1 VC V 0) (1 D) 0 (7) The voltage acro C, i.e., V C, can be repreented by VC VC1 (8) p ext, baed on (6) (8), the correponding voltage gain can be expreed to be V0 D (9) 1 D p From (9), it i hown that 0 < D < 1. B. Voltage Gain Conidering Coupling Coefficient ot Equal to One In thi cae, the coupling coefficient k i not equal to one, i.e., the leakage inductor L l1 i taken into account. Moreover, the operating mode are alo the ame a thoe mentioned in mode1 of previou cae. Fig.5. Power flow in mode 1 with coupling coefficient maller than one. 45

4 Mode 1: During thi interval, a hown in Fig.5. the following equation, containing coupling coefficient k, can be obtained. At the ame time, both L m and L l1 are imultaneouly magnetized. Hence, the correponding equation are a follow L V L L S S V Vp k (11) p p m p V i (10) m l1 In addition, the voltage on C and L o can be depicted a follow S VC VC1 V VC1 k (1) p VL 0 C V Vo (13) Likewie, by applying the voltage-econd balance principle to L o over one witching period, the following equation can be obtained to be Vc Vo D Vc Vc V0 1 D 0 (18) 1 ext, ubtituting (1) and (17) into (18) yield the voltage gain V0 D (19) 1 D p From equation 19 it i clear that voltage gain can be changed by adjuting duty cycle and turn ratio independently. So thi converter can achieve much higher gain than that of other converter. Fig.7. Curve of voltage gain veru duty cycle for the propoed converter with different value of coupling Fig.6. Power flow in mode with coupling coefficient maller than one. Mode : During thi interval, a hown in Fig.6. the voltage acro L o and C 1 are to be expreed a follow. Above all, part of the energy tored in L m and L l1 can be tranferred to C 1. Hence, the correponding equation are Vp kvc1 (14) VL VC 1 VC V 0 0 (15) By applying the voltage-econd balance to both L m and L l1 over one witching period, one can get 1 D V C 1 D 0 (16) Sequentially, by rearranging the above equation, the voltage acro C 1, i.e., V C1, can be obtained to be D Vc1 (17) 1 D p Fig.7. how the voltage gain vere duty cycle with ame coefficient of coupling k and different turn ratio. We can ee that a duty cycle increae gain increae and alo a turn ratio n ( ) increae gain increae. Fig.8. Comparion of voltage gain vere duty cycle for ame turn ratio but different coupling coefficient p 46

5 Fig.8. how voltage gain veru duty cycle for different coefficient of coupling k with ame turn ratio n ( ). Here we can ee that a coupling p coefficient increae gain increae. 4. Deign Conideration of Circuit Component 4.1 Calculation of magnetizing inductor To make ure that Lm alway operate in the poitive region, the required equation i a follow DT DT Lm (0) i I Lm Lm,min where I Lm,min i the minimum dc current in Lm. Finally, the value of Lm i et at μh. 4. Calculation of Output Inductor Fig.9. Comparion of voltage gain vere duty cycle for 3 type of converter of [17], [9] and [1] In fig.9. we can ee that voltage gain of converter [9] and traditional boot converter with ame turn ratio n ( ) and coupling coefficient i much lower than p that of propoed converter. 3. Sytem deign of the Converter How to deign the magnetizing inductor Lm, the energy tranferring capacitor C 1, the charge pump capacitor C, the output capacitor C 0, and the output inductor L 0 i hown a follow. Table. 1 Sytem pecification of propoed From the indutrial viewpoint, the output inductor i generally deigned to have no negative current when the output current i above 0% 30% of the rated output current [0]. Therefore, in thi paper, the boundary between the poitive and negative current i aumed to be at 0% of the rated output current. Hence, the value of L o can be obtained in (33), hown at the bottom of the page. Eventually, the value of L o i et at 188 μh. L0 Δt L0 Δi Lm (V V V V )(1 D)T Δi i C1 C 0 (1) L0 4.3 Calculation of Energy-Tranferring Capacitor Auming the peak-to-peak value of the capacitor voltage during the charge period, i.e., Δv C1, i et to 1% of V C1 or le, i.e., Δv C1 i maller than 10 mv, the value of C 1 can be obtained a follow: ic1δt C 1 ΔV C1 ( Ii, rated I0, rated )(1 D) T () (0.001 V ) C1 where I i,rated i the dc input current I i under rated condition. Eventually, two 470-μF capacitor with poitive terminal connected in erie are elected for C 1 47

6 4.4 Calculation of Charge Pump Capacitor Auming the variation in capacitor voltage during the dicharge period, i.e., Δv C i et to 0.1% of V C or le, i.e., Δv C i maller than 60 mv, the value of C can be obtained a follow: i Δt I rated(1 D)T C C Lo, (3) ΔV (0.001 V ) C where I Lo,rated i the dc current in L o under rated condition. Finally, two 47-μF capacitor connected in parallel are choen for C. 4.5 Calculation Output Capacitor A generally known, the output filter i ued to filter out the output current ripple a much a poible. Prior to deigning C o, the output voltage ripple Δv o i aumed to be maller than 0.1% of the rated output voltage,i.e., Δv o i maller than 7 mv. Therefore, the equivalent erie reitance of the output capacitor, i.e., ESR, can be repreented by ΔV V 0 ESR (4) ΔiL ΔiL0 Eventually, two 0-μF capacitor connected in parallel are elected for C o C 5. Control method applied with deign conideration In order to achieve a contant voltage of 7 V at output tage of the propoed converter we can do two type of control. They are PI control and Fuzzy baed control. 5.1 Control of propoed converter baed on PI control Fig.10. how the overall ytem block diagram baed on PI control. Firt of all the output voltage i compared with a contant voltage of 7V. Then thi error i given to PI controller. Then thi ignal i compared with a awtooth ignal, the reultant pule i given to MOSFET S directly and noted and given to MOSFET S 1. There are two tep to tune the parameter of the proportional gain kp and the integral gain ki in the PI controller. 1) Step 1: Start with k p = 0 and k i = 0, and trim kp until a mall reidual error i received. ) Step : Increae k i until the ytem reache an almot zero final error. 5. Control of propoed converter uing Fuzzy baed control Fig.11. Propoed overall ytem block diagram uing Fuzzy baed control Fig.11. how the overall ytem block diagram of propoed converter baed on fuzzy control. Firt of all the output i compared with a contant dc voltage of 7V to produce the error. Here the error and error change are the premie. Then premie are given to fuzzy rule baed inference. Here mamdani method i ued to infer the rule. Here the crip value i converted to fuzzified value then it i defuzzified baed on the centroid method. Then we will get the error change a crip value. Then previou error i added to get the error ignal. Thi ignal i compared with the awtooth repeating ignal to get the pule. Thi pule i directly given to MOSFET S and noted and given to S 1. Fig.10. Propoed overall ytem block diagram baed on PI control 48

7 6. Comparion of fuzzy and PI control baed output Fig.1. Output voltage baed on PI control Fig.14. Voltage acro witche S 1 and S Fig.13. Output voltage baed on Fuzzy control Output of fuzzy baed control i free from tranient and peak overhoot. More over ettling time i le for fuzzy baed ytem compared with PI baed control. Fig.15. Output Voltage & Current acro a load of 400 Reitor 7. Experimental et up of the converter Thi chapter decribe the verification of the propoed ytem operation with an experimental et up. Hardware et up conit of power circuit, control circuit, gate driving circuit and control circuit power upply.output voltage from the circuit i given to 4n5 inorder to regulate the voltage.then thi voltage i given to dpic30f010 inorder to produce the required gating pule.thi gate pule i given to FA739 which i a gate driver inorder to drive the gate pule to witch and alo provide iolation for power circuit and control circuit.lm317 i ued to regulate the voltage. Fig. 16. Voltage acro Energy Tranferring Capacitor C1 49

8 REFERECES Fig.17. Voltage acro Charge Pump Capacitor C Hardware reult of the propoed cloed loop tep up DC-DC converter are in agreement with the analyi carried out. 8. Concluion A high tep-up converter ha been preented here. By combining the coupled inductor and the witched capacitor, the correponding voltage gain i higher than that of the exiting tep-up converter combining KY and buck-boot converter. Detailed analyi of the ingle tage converter ha been preented. Baed on the analyi, deign of variou circuit component are preented. Both open loop and cloed loop control cheme of the configuration ha been explained in detail. Cloed loop control i done uing two control method ie; Conventional PI Controller and Fuzzy logic controller. A comparion of the reult obtained from the imulation of two control method i done and can be inferred that Fuzzy baed Controller i better than PI Controller. Simulation reult how the validation of the propoed topology and it analyi. The propoed ingle tage DC-AC inverter ha many remarkable feature a lited below: 1)Propoed converter ha no floating output )It ha one output inductor; hence, the output current i nonpulating. 3)The tructure of the propoed converter i quite imple and very uitable for indutrial application. Hardware etup of DC-DC converter i implemented. From 1V DC upply we get 7V DC output voltage from the imulation and hardware. More over the reult i valid when load i changed. [1] R. Lin, F. Y. Hieh, and J. J. Chen, Analyi and implementation of a bidirectional converter with high converter ratio, in Proc. IEEE ICIT, 008, pp [] K. B. Park, G. W. Moon, and M. J. Youn, oniolated high tep-up tacked converter baed on boot-integrated iolated converter, IEEE Tran. Power Electron., vol. 6, no., pp , Feb [3] C. M. Lai, C. T. Pan, and M. C. Cheng, High-efficiency modular high tep-up interleaved boot converter for DCmicrogrid application, IEEE Tran. Ind. Electron., vol. 48, no. 1, pp , Jan./Feb. 01. [4] F. L. Luo, Analyi of uper-lift luoconverter with capacitor voltage drop, in Proc. IEEE ICIEA, 008, pp [5] L. S. Yang, T. J. Liang, H. C. Lee, and J. F. Chen, ovel high tep-up DC DC converter with coupled-inductor and voltagedoubler circuit, IEEE Tran. Ind. Electron., vol. 58, no. 9, pp , Sep [6] C. T. Pan and C. M. Lai, A highefficiency high tep-up converter with low witch voltage tre for fuel-cell ytem application, IEEE Tran.Ind. Electron., vol. 57, no. 6, pp , Jun [7] K. I. Hwu and Y. T. Yau, KY converter and it derivative, IEEE Tran.Power Electron., vol. 4, no. 1, pp , Jan [8] K. I. Hwu and Y. T. Yau, A KY boot converter, IEEE Tran. Power Electron., vol. 5, no. 11, pp , ov [9] K. I. Hwu and Y. T. Yau, Inductorcoupled KY boot converter, IET Electron. Lett., vol. 46, no. 4, pp , ov [10] K. I. Hwu and W. C. Tu, Voltagebooting converter with energy pumping, IET Power Electron., vol. 5, no., pp , Feb. 01. [11] K. I. Hwu, Y. T. Yau, and Y. H. Chen, A novel voltage-booting converter 430

9 with paive voltage clamping, in Proc. IEEE ICSET, 008, pp [1] K. I. Hwu and Y. T. Yau, Two type of KY buck-boot converter, IEEE Tran. Ind. Electron., vol. 56, no. 8, pp , Aug [13] Y. Deng, Q. Rong, Y. Zhao, J. Shi, and X. He, Single witch high tep-up converter with built-in tranformer voltage multiplier cell, IEEE Tran.Power Electron., vol. 7, no. 8, pp , Aug. 01. [14] W. Li,W. Li, X. He, D. Xu, and B.Wu, General derivation law of noniolated high-tep-up interleaved converter with built-in tranformer, IEEE Tran. Ind. Electron., vol. 59, no. 3, pp , Mar. 01. [15] R. J. Wai and R. Y. Duan, Highefficiency power converion for low power fuel cell generation ytem, IEEE Tran. Power Electron., vol. 0, no. 4, pp , Jul [16] K.I.Hwu and W.Z.Jiang, Voltage Gain Enhancement for a Step-Up Converter Contructed by KY and Buck-Boot Converter, IEEE Tran. Power Electron, vol.61, no.7, pp , May013. Acknowledgment The author would like to thank the Referee and the Aociate editor for their ueful comment and uggetion. 431