Abstract–This project proposes a design method forZ-source network based on inductor current. In Z-source inverter, when thevariation of the output current from the Z-source network is large, thevariation of the inductor current and the capacitor voltage increase in theZ-source network.

Therefore, discontinuous current mode (DCM) conditiontransiently occurred in the Z-source network inductors. DCM condition affectsthe operation of the z-source inverter. Against the problem, this projectproposes a new design method of the Z-source inverter to maintain continuouscurrent mode (CCM) condition. The proposed method is confirmed by simulationresults and circuit experiments.

I.INTRODUCTIONThe multiple-input DC–DC converter is useful tocombine several input power sources whose voltage levels or power capacity aredifferent and to get regulated output voltage for the load. Solar panel isarranged by a combination of more PV cells.

Solar panel direction depends uponthe maximum point of the solar radiation, and the radiation is absorbed. The power is stored in battery or directlyconnected to the dc-dc converter for using the dc load.A multiple-input DC–DC converter is useful to obtain the regulated outputvoltage several input power sources such as a solar and fuel cell source. A basic block diagram shows that solarenergy source is connected to DC-DC Converter transfers energy to the load. FIG.

1.EXSISTINGSYSTEMPhotovoltaic technology is the one that convertssolar energy directly into electricity, through the use of solar cells orsimilar devices. A solar cell constitutes the basic unit of a PV generatorwhich, in turn, is the main component it. A photovoltaic generator, also knownas a photovoltaic array, is the total system consisting of all PV modulesconnected in series or parallel with each other .

Solar energy, along with otherrenewable energy resources, that does not deplete in source, is reliable, andenvironment-friendly. Especially, solar power is arguably thecleanest, most reliable form of renewableenergy available, and that can be used power home. Solarowered photovoltaic(PV) panels convert the sun’s rays intoelectricity by exciting electrons in silicon cells using the photons of lightfrom the sun.II.Z- SOURCE INVERTERTraditionalsingle-phase voltage-source converter (abbreviated as V source converter).Themain converter circuit, is feed by dc voltage source with large capacitor .Thedc voltage source can be a battery, diode rectifier, fuel-cell stack, and/orcapacitor.

F2our switches are used in the main circuit; each is composed of apower transistor and freewheeling diode to provide bidirectional current flowand unidirectional voltage blocking capability. The V-source converters arewidely used. There are twoFIG.1.Traditional v- Source Inverterthe traditionalsingle-phase current-source converter (abbreviated as I-source converter)structureZ-source inverter (ZSI) which is based on Z-sourcenetwork can be used to buck and boost the output AC voltage, which is notpossible using traditional voltage source or current source inverters.

Also theZSI has the unique ability to short the dc link, which is not possible in thetraditional voltage source inverters. This improves the reliability of thecircuit .Actually concept of boosting the input voltage is based on the ratioof “shoot-through” time to the whole switching period. Z-source converter wherean impedance network is placed between d.c. link and inverter. Z-sourceinverter (ZSI) provides a greater voltage than the d.c.

link voltage. Itreduces the inrush current in the current because of twoinductors in z source network. It forms a second order filter the undesirablevoltage sags of the dc voltage source. FIG.

2.Topology of the single phase Z-source inverterWhere the impedance network is placed between thepower source and the single phase inverter The presence of 2 inductors & 2capacitors in Z-source network, allows both switches of same phase leg ON statesimultaneously, called as shoot-through state & gives boosting capabilityto the inverter without damaging the switching devices. During shoot throughstate energy is transferred From capacitor To inductor & hence Z-sourceinverter(ZSI) gains the voltage boosting capability Diode is required toprevent the discharge of overcharged Capacitor through the source.III.MODES OF OPERATIONThis shoot-through zero state (or vector) is notpresent in the traditional VSI, otherwise shoot-through would occur. This extrazero state (vector) is called the shoot through zero state (or vector). Thisshoot-through zero state can be produced in seven different ways:• shoot-through via any one phase leg•combinations of any two phase legs•all three phase legsThe Z-source network has accomplished theshoot-through zero state. This shoot-through zero state gives the specialbuck-boost feature to the inverter.

Figure-6.1 depicts the equivalent circuitof the ZSI when seen from the dc link . The inverter bridge is similar to ashort circuit when the inverter bridge is in the shoot-through zero state, asdepicted in whereas the inverter bridgebecomes an equivalent current source as depicted in Figure-6.3 when it is inone of the six active states . The inverter bridge can also be illustrated by acurrent source with zero value (i.e.

, an open circuit) when it is in one of thetwo conventional zero states.FIG.2 Equivalent Circuit of ZSI whenviewed from dc link FIG.3 Equivalent Circuit of ZSI in Shoot-through stateFIG.4 Equivalent Circuit of ZSI in Active StateIt is supposed that L1 is = L2, and C1 = C2. Theoutput ac voltage equation of PWM based ZSIis given by:………..

(1) Where Vac is maximum sinusoidal inverter outputvoltage, B is boost factor, M is the modulation index and Vo is input dcvoltage. The product (B.M) is called inverter gain and is expressed by G. So, equation (1) can be written asVac = GVo/2 …………..

(2)Boost factor is decided from the given relation…. (3)IV.SIMULATIONDIAGRAMFIG.

1 SIMULATION OFHYBRID SYSTEMFIG.2SIMULATION OF FUEL CELLV.SIMULATION RESULTSFIG.1SOLAR CELL INPUTFIG.2 FUEL CELL INPUTFIG.3 DC OUTPUTFIG.4AC OUTPUTVI.

CONCLUSIONHybrid energy systemthat combines Photovoltaic (PV) and hydrogen fuel cell energy using z sourceinverter is simulated. The output voltage from combined solar energy and hydrogen fuel cell energy is regulated usingz source inverter. Two different types of loads (ac and dc load) is used.

Thesimulation is done with help of MATLAB software and simulation results areobtained. In future the same circuit can be extended for more than two sources.REFERENCE1 Edwin Deepak., “Performance analysis of z source cascaded h-bridge multilevel inverter based on multicarrier pwm techniques.” 2 S.

Satchya, C.Karthikeyan,Fuzzy logic based z source inverter for hybridenergy resources. 3 T.Lakshmikanth, C.K.

Rambabu, R.Punyavathi “Z source multilevel inverterbased pv generation system” 4 Milchilegovo, Dimitrivinnikov, Ryszarad”Impedence source inverterbbased high power dc-dc converter fuel cellapplication”5 Byamaheshnayak,Saswani,Swapna dash”Performance analysis of different control stratagies in z source inverter”6 Valluri,sathyasrinivas,E.Vagrilkumar,K.

Baya.,”A two input single output zsourced dc-dc converter for renewable applications”7 Daniel pradeep, Damodharan.S, vidhya, Arun.V.

S,Rajkumr.m”Innovativedc-dc converter for hybrid energy sources using multi inputs” Abstract–This project proposes a design method forZ-source network based on inductor current. In Z-source inverter, when thevariation of the output current from the Z-source network is large, thevariation of the inductor current and the capacitor voltage increase in theZ-source network. Therefore, discontinuous current mode (DCM) conditiontransiently occurred in the Z-source network inductors. DCM condition affectsthe operation of the z-source inverter. Against the problem, this projectproposes a new design method of the Z-source inverter to maintain continuouscurrent mode (CCM) condition.

The proposed method is confirmed by simulationresults and circuit experiments.I.INTRODUCTIONThe multiple-input DC–DC converter is useful tocombine several input power sources whose voltage levels or power capacity aredifferent and to get regulated output voltage for the load.

Solar panel isarranged by a combination of more PV cells. Solar panel direction depends uponthe maximum point of the solar radiation, and the radiation is absorbed. The power is stored in battery or directlyconnected to the dc-dc converter for using the dc load.A multiple-input DC–DC converter is useful to obtain the regulated outputvoltage several input power sources such as a solar and fuel cell source. A basic block diagram shows that solarenergy source is connected to DC-DC Converter transfers energy to the load. FIG.1.EXSISTINGSYSTEMPhotovoltaic technology is the one that convertssolar energy directly into electricity, through the use of solar cells orsimilar devices.

A solar cell constitutes the basic unit of a PV generatorwhich, in turn, is the main component it. A photovoltaic generator, also knownas a photovoltaic array, is the total system consisting of all PV modulesconnected in series or parallel with each other .Solar energy, along with otherrenewable energy resources, that does not deplete in source, is reliable, andenvironment-friendly. Especially, solar power is arguably thecleanest, most reliable form of renewableenergy available, and that can be used power home. Solarowered photovoltaic(PV) panels convert the sun’s rays intoelectricity by exciting electrons in silicon cells using the photons of lightfrom the sun.II.

Z- SOURCE INVERTERTraditionalsingle-phase voltage-source converter (abbreviated as V source converter).Themain converter circuit, is feed by dc voltage source with large capacitor .Thedc voltage source can be a battery, diode rectifier, fuel-cell stack, and/orcapacitor.F2our switches are used in the main circuit; each is composed of apower transistor and freewheeling diode to provide bidirectional current flowand unidirectional voltage blocking capability. The V-source converters arewidely used. There are twoFIG.1.

Traditional v- Source Inverterthe traditionalsingle-phase current-source converter (abbreviated as I-source converter)structureZ-source inverter (ZSI) which is based on Z-sourcenetwork can be used to buck and boost the output AC voltage, which is notpossible using traditional voltage source or current source inverters. Also theZSI has the unique ability to short the dc link, which is not possible in thetraditional voltage source inverters. This improves the reliability of thecircuit .Actually concept of boosting the input voltage is based on the ratioof “shoot-through” time to the whole switching period.

Z-source converter wherean impedance network is placed between d.c. link and inverter. Z-sourceinverter (ZSI) provides a greater voltage than the d.

c. link voltage. Itreduces the inrush current &hormonics in the current because of twoinductors in z source network. It forms a second order filter &handles the undesirablevoltage sags of the dc voltage source. FIG.

2.Topology of the single phase Z-source inverterWhere the impedance network is placed between thepower source and the single phase inverter The presence of 2 inductors & 2capacitors in Z-source network, allows both switches of same phase leg ON statesimultaneously, called as shoot-through state & gives boosting capabilityto the inverter without damaging the switching devices. During shoot throughstate energy is transferred From capacitor To inductor & hence Z-sourceinverter(ZSI) gains the voltage boosting capability Diode is required toprevent the discharge of overcharged Capacitor through the source.III.

MODES OF OPERATIONThis shoot-through zero state (or vector) is notpresent in the traditional VSI, otherwise shoot-through would occur. This extrazero state (vector) is called the shoot through zero state (or vector). Thisshoot-through zero state can be produced in seven different ways:• shoot-through via any one phase leg•combinations of any two phase legs•all three phase legsThe Z-source network has accomplished theshoot-through zero state. This shoot-through zero state gives the specialbuck-boost feature to the inverter. Figure-6.

1 depicts the equivalent circuitof the ZSI when seen from the dc link . The inverter bridge is similar to ashort circuit when the inverter bridge is in the shoot-through zero state, asdepicted in whereas the inverter bridgebecomes an equivalent current source as depicted in Figure-6.3 when it is inone of the six active states . The inverter bridge can also be illustrated by acurrent source with zero value (i.e.

, an open circuit) when it is in one of thetwo conventional zero states.FIG.2 Equivalent Circuit of ZSI whenviewed from dc link FIG.3 Equivalent Circuit of ZSI in Shoot-through stateFIG.4 Equivalent Circuit of ZSI in Active StateIt is supposed that L1 is = L2, and C1 = C2. Theoutput ac voltage equation of PWM based ZSIis given by:………..(1) Where Vac is maximum sinusoidal inverter outputvoltage, B is boost factor, M is the modulation index and Vo is input dcvoltage.

The product (B.M) is called inverter gain and is expressed by G. So, equation (1) can be written asVac = GVo/2 ………….. (2)Boost factor is decided from the given relation….

(3)IV.SIMULATIONDIAGRAMFIG.1 SIMULATION OFHYBRID SYSTEMFIG.

2SIMULATION OF FUEL CELLV.SIMULATION RESULTSFIG.1SOLAR CELL INPUTFIG.2 FUEL CELL INPUTFIG.3 DC OUTPUTFIG.4AC OUTPUTVI.CONCLUSIONHybrid energy systemthat combines Photovoltaic (PV) and hydrogen fuel cell energy using z sourceinverter is simulated. The output voltage from combined solar energy and hydrogen fuel cell energy is regulated usingz source inverter.

Two different types of loads (ac and dc load) is used. Thesimulation is done with help of MATLAB software and simulation results areobtained. In future the same circuit can be extended for more than two sources.REFERENCE1 Edwin Deepak., “Performance analysis of z source cascaded h-bridge multilevel inverter based on multicarrier pwm techniques.” 2 S.

Satchya, C.Karthikeyan,Fuzzy logic based z source inverter for hybridenergy resources. 3 T.Lakshmikanth, C.K.Rambabu, R.Punyavathi “Z source multilevel inverterbased pv generation system” 4 Milchilegovo, Dimitrivinnikov, Ryszarad”Impedence source inverterbbased high power dc-dc converter fuel cellapplication”5 Byamaheshnayak,Saswani,Swapna dash”Performance analysis of different control stratagies in z source inverter”6 Valluri,sathyasrinivas,E.Vagrilkumar,K.Baya.,”A two input single output zsourced dc-dc converter for renewable applications”7 Daniel pradeep, Damodharan.S, vidhya, Arun.V.S,Rajkumr.m”Innovativedc-dc converter for hybrid energy sources using multi inputs”