Review of Impedance Source Dc-Dc Converters

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1 2018 IJSRS olume 4 Issue 3 Print ISSN : Online ISSN: X National Conference on Advances in Engineering and Applied Science (NCAEAS) 29 th January 2018 Organized by : Anjuman College of Engineering and echnology (ACE) Nagpur, Maharashtra, India, In association with International Journal of Scientific Research in Science and echnology Review of Impedance Source DcDc Converters Nitesh Funde, Mohini Sonparote, Dipali Pimpalkar, Mayuri hakare Department of Electrical engineering, YCCE, Nagpur, Maharashtra, India ABSRAC Nowadays due to the requirement of renewable energy sources, distributed generations (DG) are widely used. In such applications, DG grid connection is required through DCac inverters. But the DC output from fuelcell is in low quantity, therefore there must needed the network which boosted up the DC voltage to the required level. o fulfill this requirement, Impedance Source DC to DC converter is required. Impedance Source Converter is an advanced technology in electrical energy conversion, overcome limitations of traditional converters. his paper presents different types of impedance source networks for DC to DC power conversion. All types of impedance networks adapt a unique impedance network to connect a converter main circuit to source from which the supply is taken. hus, providing the features that cannot available in the traditional voltagesource and currentsource converters in which capacitor and inductor are used, respectively. he impedance source converter overcomes all the problems, barriers and limitations of the traditional converters and provides a new power conversion concept. hese impedance source networks can be used in all DCDC, acdc, acac, DCac power conversion. So this paper describes the operating principle, simulation results and sizing of components of three types of impedance network and its comparison. Keywords: Fuel cell, DCDC converter, Impedance source converter, Quasi Zsource converter, Quadratic converter I. INRODUCION Nowadays due to the requirement of renewable energy sources, distributed generations (DG) are widely used. In such applications, DG grid connection is required through DCac inverters. But the DC output from fuel cell and Photo oltaic panel is so small as compared to grid voltage. herefore, there must need of the network which boosts up the DC voltage to the required level. o fulfil this requirement DCDC converter has been connected in between DG and inverter. In conventional method boost, buckboost converters are used. But, due to their disadvantages all the researchers working on the Impedance Source DC to DC converters [12]. here is two traditional converters viz., current source converter and voltage source converter. In voltage source converter, a DC voltage is supplied by a relatively large capacitor which feeds the main converter circuit. he DC source may be a battery, fuelcell stack, diode rectifier and it may be a capacitor [34]. his voltage source is widely used but it has conceptual barriers and disadvantages are as follows [5] NCAEAS4409 NCAEAS ACE JanuaryFebruary2018 [ (4) 3 : ] 544

2 olume 4 Issue 3 IJSRS/Conf/NCAEAS/ACE/2018/01 he ac output voltage is limited and it cannot exceed the DCrail voltage or DCrail voltage has to be greater than ac input voltage. Hence, voltage source converter is a buck inverter for DC to ac conversion and the voltage source inverter is a boost converter for ac to DC conversion. For such application where only one drive is desirable but the availability of DC voltage is limited, in that case an additional DC to DC boost converter is required to obtain a desired output voltage. his additional converter increases system cost and reduces efficiency. Sometime, shootthrough may occur due to Electromagnetic Interference, it causes the destroying devices and reliability reduces. In current source inverter, a DC current source feeds the main converter circuit. he current source may be a large inductor supplied by voltage source such as a battery, fuelcell, diode rectifier, or it may be a thyristor converter. he current source has following disadvantages [5] he ac output voltage is greater than the original DC input voltage which feeds the DC inductor or the DC output is smaller than the input ac voltage. Hence, the current source converter for DC to ac conversion and the current source converter is a buck converter for ac to DC conversion. For application where variable voltage range is required, an extra DC to DC buck or DC to DC boost converter is essential. his additional converter increases system cost and reduces efficiency. Sometime, shootthrough may occur due to Electromagnetic Interference, it causes the destroying devices and reliability reduces. Both current and voltage source converters having following common problem [5]. heir output voltage range is limited to either greater or smaller than the input voltage. hat is, they are either a boost or a buck converter and they cannot be buckboost converter simultaneously. Both the circuits cannot be exchange with each other. hat is, voltage source converter cannot be used as a current source converter or cannot be vice versa. In both the circuits, due to EMI shootthrough occurs and reduces reliability. herefore, to overcome all these disadvantages and limitations, the impedance source network is used. here are three impedance networks as follows [6] Zsource converter Quasi Zsource converter Quadratic Zsource converter hey all having the advantages like higher efficiency, reduces voltage stress, avoid the damaging to the circuit due to EMI etc. In this paper there are five sections. Second, third and fourth section represents the review and mathematical modeling of ZSC, QZSC and Quadratic converter respectively. Fifth section signifies the component size and comparison between all impedance converters. II. REIEW OF ZSOURCE CONERER In Figure 1 shows proposed structure of simple Zsource converter. It familiarizes a unique impedance converters International Journal of Scientific Research in Science and echnology ( 545

3 olume 4 Issue 3 IJSRS/Conf/NCAEAS/ACE/2018/01 network to connect the converter main circuit to the DC source. Load or another DCAC converter can be connected after Zsource converter, for providing the exclusive features which is not available in traditional voltage source and current source converters in which capacitors and inductors are used, respectively. he Z source converter overcomes these disadvantages [7]. In the two port network of Zsource converter consists of two capacitors C1 and C2, two inductors L1 and L2 and they are all connected in X shape to provide an impedance source. he voltage source or current source can be used as a DC source. herefore, DC source can be a fuelcell stack, an inductor, a capacitor, diode rectifier or a thyristor converter. he inductors used may be split inductors or two separate inductors. In this, same ratings of inductors are used and same ratings of capacitors are used [7]. traditional voltage and current source converters [8]. he Zsource converter operates in two switching states i.e. shootthrough state and nonshootthrough state. he Figure 2 shows equivalent circuit of the Zsource converter in shootthrough state and Figure 3 shows equivalent circuit of Z source converter in nonshootthrough state. In nonshootthrough state, the output switch is open and diode which is connected at the input side is in forward biased, i.e. it is in on state [910]. And in shootthrough state, diode is in off state and the switch which is connected at the output side is closed. his Zsource converter can be used for all DC to ac, ac to DC, ac to ac and DC to DC conversion. Example of z source converter is a Zsource inverter used for DC to ac conversion for fuelcell applications. Fuelcell is widely used for fuelcell vehicles and distributed power generation. Fuelcell normally produces a voltage (2:1 ratio) depending on current taken from the stacks. herefore, a boost DC to DC converter is needed because the traditional voltage source inverter cannot produce DC voltage greater than the DC input voltage. he diode is used in series with the fuelcell before the Zsource network for preventing the reverse current flow. he main feature of the Zsource converter is that output voltage may be any value between zero to infinity inattentive of the fuelcell voltage. It means that, the Z source converter is a buckboost converter that has a wide range of obtainable output voltage. his feature is not available in International Journal of Scientific Research in Science and echnology ( 546

4 olume 4 Issue 3 IJSRS/Conf/NCAEAS/ACE/2018/01 L D L 1 ON. C OFF.( in C ) 0 (9) C 1 C 2 in S O C OFF (10) in OFF ON L 2 i ON.0 OFF ( 2 C in ) (11) Figure 1: Equivalent circuit of Zsource converter From equation (11), ON D L 1 L1 C1 C2 1 1 D.. in C C1 C2 in 2 OFF 1 2D 1 (12) in d C1 L2 C2 o C. in Where, Boost Factor, 1 D 1 2D (13) (14) Figure 2: Equivalent circuit of shootthrough state of Zsource converter L1 L2 III. REIEW OF QUASI ZSOURCE DCDC CONERER in d C1 C1 Figure 3: Equivalent circuit of nonshootthrough state of Z source converter From the equivalent circuits, L1 L2 L2 C2 C2 c1 c2 c L1 L2 L O (1) (2) Nonshootthrough state occurs for an interval OFF during the switching cycle. From Fig.3, d in (3) L in C (4) 0 c L 2 C in (5) Shootthrough state occurs for an interval of ON, during the switching cycle. From Fig (6) L C (7) d 2 C (8) Here, O= DC source voltage and ON OFF= In steady state, the average value of the inductors over one switching period () should be zero [11]. hus, we get he Fig. 4 shows the equivalent circuit for Quasi Z source converter. Quasi Zsource converter adapts unique impedance network. his network consists of two identical inductances L 1 and L 2 and two identical capacitances C 1 and C 2. Like Zsource converter, QZS converter also operates in two states. With this network shoot through state can be apply to boost the voltage [12]. It helps the network to avoid damage during shootthrough state or any other fault occurrence. Fig. 5 shows the shoot through state of Quasi Zsource converter and Fig. 6 shows the nonshoot through state of Quasi Z source converter. During shootthrough state, the higher value of voltage obtained at output due to boost conversion. During nonshoot through state, it will work normally as traditional voltage source converter [13]. he advantages of QZS converter over the Zsource converter are reducing voltage stress, drawing continuous current from the supply and reduced voltage stresses on capacitors [14]. For the nonshootthrough state L1 in C1 L2 c2 0 C1 L2 C1 C2 (15) (16) (17) International Journal of Scientific Research in Science and echnology ( 547

5 in L 1 C 2 D 1 L 2 C 1 O S Figure 4: Equivalent circuit of Quasi Z Source Converter C 2 in L1 L1 C1 C2 C 1 L 2 L2 Figure 5: Equivalent circuit of Shootthrough state of Quasi Z source converter I o olume 4 Issue 3 IJSRS/Conf/NCAEAS/ACE/2018/01 I. REIEW OF QUADRAIC CONERER In many industrial applications switched mode DCDC converters with high voltage conversion ratio are widely used. In traditional converters, the voltage conversion ratio is limited due to power loss of switches as well as component stresses which results in increased duty cycle and limitations on conversion ratio. he modified method to obtain the high voltage gain is quadratic converter [1516]. he quadratic converter network consists of two identical inductors L 1 and L 2, capacitor C and two diodes D 1 and D 2 shown in Fig.7. he voltage across capacitor is equal to the output boosted voltage. hus the voltage across capacitor is always higher than the input voltage [1718]. here are two working states of quadratic converter as shown in Fig. 8 and Fig. 9. D2 L1 D1 L2 C 2 C2 L 1 D1 L 2 in C o S L1 L2 in C1 C 1 O S Figure 7: Equivalent circuit of Quadratic Converter D 2 L 1 I L1 D1 L2 I L2 Figure 6: Equivalent circuit of Nonshootthrough state of Quasi Z source converter For shootthrough state L2 L1 I C Io in O C C2 L1 C2 in (18) (19) 0 0 (20) L2 C1 At steady state, the average voltage across the both inductors over one switching cycle is zero. We get, Figure 8: Equivalent circuit shootthroughstate of Quadratic Converter L1 I L1 D2 D 1 L2 IL2 in o C C2 0 C1 C2 (21) L2 ON C1 OFF C in 1 1 2D Where, β is the boost factor and D is the Duty Cycle, D ON in (22) (23) L1 IC Figure 9: Equivalent circuit of nonshootthroughstate of Quadratic Converter When switch S is ON, the diode D 2 will be ON and diode D 1 in OFF condition for duration ON of switching L2 S International Journal of Scientific Research in Science and echnology ( 548

6 olume 4 Issue 3 IJSRS/Conf/NCAEAS/ACE/2018/01 cycle. At this state, capacitor of quadratic converter charges its inductors. When the switch S is OFF, the diode D 1 will be ON and diode D 2 is in OFF condition for duration OFF of switching cycle. At this state quadratic converter inductors charge capacitor and provide voltage at output. From Fig. 8, in L1 L2 C (24) C L2 (25) in L2 (26) From Fig. 9, in L1 C (27) C L2 0 (28) L2 C 0 (29) β= Boost factor 0 i L2 ON C OFF C L1 0 (34) C1 C 0 ON OFF (35) C (1 D ) P max s D 2 R % C OFF in 1 1 D 2 (39) herefore, the quadratic converter provide high voltage gain and suitable for high voltage ratio applications.. SIZING OF COMPONENS he major components of the impedance network based DCDC converter are inductor and capacitor. For designing the converter the size of inductor and capacitor play important role and it should be as minimum as possible. At shoot through state during boost conversion mode, inductor will limit the current Let, the average voltage in inductor L 1 is zero then, ripple I (R C %) through the devices. he maximum ON in OFF in C L1 0 (30) calculate by, C ON OFF (31) in OFF ON L1 L2 L C1 C 1 in 1 ON power Pmax operation is chosen, the inductor value is (32) (1 D ) 2 D L in s (1 2D )P max R C % (40) I C 1 he capacitor absorb the current ripple and limit the (33) in 1 D voltage ripple ( R %) on the devices and so as to keep Let, the average voltage in inductor L 2 is zero then, the output voltage constant can be calculated by, 0 1 he values of the passive component i.e. inductor (36) and C 1 ON capacitor for impedance source converters are calculated in the able with the following specification C 1 in=230, D=0.3, P max=4kw, Switching Frequency (37) in 1 D F s=10khz, Current Ripple R C=25%, oltage Ripple R =3%; C (38) in C in 1 D 2 (41) (42) (43) International Journal of Scientific Research in Science and echnology ( 549

7 olume 4 Issue 3 IJSRS/Conf/NCAEAS/ACE/2018/01 ABLE I INDUCOR AND CAPACIOR RAING FOR DIFFEREN IMPEDANCE CONERERS Sr. No. Converter Name Inductor Size Formulae (L 1 L 2 L) Capacitor Size Formulae (C 1 C 2 C) Inductor and Capacitor Size 01 Zsource converter L (1 D ) 2 in s D (1 2D )P R % C (1 2D ) Pmax s D 2 R % max C in L = 277mH C =30µF 02 Quasi Zsource converter L (1 D 2 ) in s D (1 2D )P R % C (1 2D ) Pmax s D 2 R % max C in L = 277mH C =30µF 03 Quadratic Converter L 2 in s D (1 D )Pmax RC % C (1 D ) Pmax s D 2 R % in L = 226mH C = 53µF III. CONCLUSION In present days, Distributed Generations are widely used. For this, dc to ac inverters are required. But more power generation from dc is not possible. herefore, there is requirement of dc to dc boost converter. herefore, this paper has presented different types of impedancesource converters for obtaining dc to dc power conversion. All three types of impedance converter adapt unique impedance network to connect the converter main circuit to the power source. hus it provides main feature which cannot be implemented in the traditional voltage and current source converters. hus, all types of impedance converters overcome theoretical limitations found in voltagesource converter and currentsource converter and provide an important power conversion concept. he paper described the proposed structure and operating principle of Zsource, Quasi Zsource and Quadratic Z source converters. his paper also described the factor (boost factor) which is responsible for boosting up the voltage. Because of impedance networks the cost reduces, component minimizes and the efficiency increases. he paper also described the applications of converters like Zsource converter is most suitable for fuelcell applications, Quasi Z source converter is most suitable for P power generation and Quadratic converters are used where the used of Z source converter and Quasi Z source converter is restricted. I. REFERENCES [1]. R. D. Middlebrook, "ransformer less DCtoDC converters with large conversion ratios," In elecommunications Energy Conference, INELEC 84 International, pp , [2]. G. R. Walker, P. C. Sernia, "Cascaded dc dc converter connection of photovoltaic International Journal of Scientific Research in Science and echnology ( 550

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