Abstract–This project proposes a design method for

Z-source network based on inductor current. In Z-source inverter, when the

variation of the output current from the Z-source network is large, the

variation of the inductor current and the capacitor voltage increase in the

Z-source network. Therefore, discontinuous current mode (DCM) condition

transiently occurred in the Z-source network inductors. DCM condition affects

the operation of the z-source inverter. Against the problem, this project

proposes a new design method of the Z-source inverter to maintain continuous

current mode (CCM) condition. The proposed method is confirmed by simulation

results and circuit experiments.

I.INTRODUCTION

The multiple-input DC–DC converter is useful to

combine several input power sources whose voltage levels or power capacity are

different and to get regulated output voltage for the load. Solar panel is

arranged by a combination of more PV cells. Solar panel direction depends upon

the maximum point of the solar radiation, and the radiation is absorbed. The power is stored in battery or directly

connected to the dc-dc converter for using the dc load.A multiple-input DC–DC converter is useful to obtain the regulated output

voltage several input power sources such as a solar and fuel cell source. A basic block diagram shows that solar

energy source is connected to DC-DC Converter transfers energy to the load.

FIG.1.EXSISTING

SYSTEM

Photovoltaic technology is the one that converts

solar energy directly into electricity, through the use of solar cells or

similar devices. A solar cell constitutes the basic unit of a PV generator

which, in turn, is the main component it. A photovoltaic generator, also known

as a photovoltaic array, is the total system consisting of all PV modules

connected in series or parallel with each other .Solar energy, along with other

renewable energy resources, that does not deplete in source, is reliable, and

environment-friendly. Especially, solar power is arguably the

cleanest, most reliable form of renewable

energy available, and that can be used power home. Solar

owered photovoltaic(PV) panels convert the sun’s rays into

electricity by exciting electrons in silicon cells using the photons of light

from the sun.

II.Z- SOURCE INVERTER

Traditional

single-phase voltage-source converter (abbreviated as V source converter).The

main converter circuit, is feed by dc voltage source with large capacitor .The

dc voltage source can be a battery, diode rectifier, fuel-cell stack, and/or

capacitor.F2our switches are used in the main circuit; each is composed of a

power transistor and freewheeling diode to provide bidirectional current flow

and unidirectional voltage blocking capability. The V-source converters are

widely used. There are two

FIG.1.

Traditional v- Source Inverter

the traditional

single-phase current-source converter (abbreviated as I-source converter)

structure

Z-source inverter (ZSI) which is based on Z-source

network can be used to buck and boost the output AC voltage, which is not

possible using traditional voltage source or current source inverters. Also the

ZSI has the unique ability to short the dc link, which is not possible in the

traditional voltage source inverters. This improves the reliability of the

circuit .Actually concept of boosting the input voltage is based on the ratio

of “shoot-through” time to the whole switching period. Z-source converter where

an impedance network is placed between d.c. link and inverter. Z-source

inverter (ZSI) provides a greater voltage than the d.c. link voltage. It

reduces the inrush current in the current because of two

inductors in z source network. It forms a second order filter the undesirable

voltage sags of the dc voltage source.

FIG.2.Topology of the single phase Z-source inverter

Where the impedance network is placed between the

power source and the single phase inverter The presence of 2 inductors & 2

capacitors in Z-source network, allows both switches of same phase leg ON state

simultaneously, called as shoot-through state & gives boosting capability

to the inverter without damaging the switching devices. During shoot through

state energy is transferred From capacitor To inductor & hence Z-source

inverter(ZSI) gains the voltage boosting capability Diode is required to

prevent the discharge of overcharged Capacitor through the source.

III.MODES OF OPERATION

This shoot-through zero state (or vector) is not

present in the traditional VSI, otherwise shoot-through would occur. This extra

zero state (vector) is called the shoot through zero state (or vector). This

shoot-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 legs

The Z-source network has accomplished the

shoot-through zero state. This shoot-through zero state gives the special

buck-boost feature to the inverter. Figure-6.1 depicts the equivalent circuit

of the ZSI when seen from the dc link . The inverter bridge is similar to a

short circuit when the inverter bridge is in the shoot-through zero state, as

depicted in whereas the inverter bridge

becomes an equivalent current source as depicted in Figure-6.3 when it is in

one of the six active states . The inverter bridge can also be illustrated by a

current source with zero value (i.e., an open circuit) when it is in one of the

two conventional zero states.

FIG.2 Equivalent Circuit of ZSI when

viewed from dc link

FIG.3 Equivalent Circuit of ZSI in Shoot-through state

FIG.4 Equivalent Circuit of ZSI in Active State

It is supposed that L1 is = L2, and C1 = C2. The

output ac voltage equation of PWM based ZSI

is given by:

………..(1)

Where Vac is maximum sinusoidal inverter output

voltage, B is boost factor, M is the modulation index and Vo is input dc

voltage. The product (B.M) is called inverter gain and is expressed by G.

So, equation (1) can be written as

Vac = GVo/2

………….. (2)

Boost factor is decided from the given relation

…. (3)

IV.SIMULATION

DIAGRAM

FIG.1 SIMULATION OF

HYBRID SYSTEM

FIG.2

SIMULATION OF FUEL CELL

V.SIMULATION RESULTS

FIG.1

SOLAR CELL INPUT

FIG.2 FUEL CELL INPUT

FIG.3 DC OUTPUT

FIG.4

AC OUTPUT

VI.CONCLUSION

Hybrid energy system

that combines Photovoltaic (PV) and hydrogen fuel cell energy using z source

inverter is simulated. The output voltage from combined solar energy and hydrogen fuel cell energy is regulated using

z source inverter. Two different types of loads (ac and dc load) is used. The

simulation is done with help of MATLAB software and simulation results are

obtained. In future the same circuit can be extended for more than two sources.

REFERENCE

1 Edwin

Deepak., “Performance analysis of z source cascaded h-bridge multilevel inverter based on multi

carrier pwm techniques.”

2

S.Satchya, C.Karthikeyan,Fuzzy logic based z source inverter for hybrid

energy resources.

3

T.Lakshmikanth, C.K.Rambabu, R.Punyavathi “Z source multilevel inverter

based pv generation system”

4 Milchilegovo, Dimitrivinnikov, Ryszarad

“Impedence source inverterbbased high power dc-dc converter fuel cell

application”

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 z

sourced dc-dc converter for renewable applications”

7

Daniel pradeep, Damodharan.S, vidhya, Arun.V.S,Rajkumr.m”Innovative

dc-dc converter for hybrid energy sources using multi inputs”

Abstract–This project proposes a design method for

Z-source network based on inductor current. In Z-source inverter, when the

variation of the output current from the Z-source network is large, the

variation of the inductor current and the capacitor voltage increase in the

Z-source network. Therefore, discontinuous current mode (DCM) condition

transiently occurred in the Z-source network inductors. DCM condition affects

the operation of the z-source inverter. Against the problem, this project

proposes a new design method of the Z-source inverter to maintain continuous

current mode (CCM) condition. The proposed method is confirmed by simulation

results and circuit experiments.

I.INTRODUCTION

The multiple-input DC–DC converter is useful to

combine several input power sources whose voltage levels or power capacity are

different and to get regulated output voltage for the load. Solar panel is

arranged by a combination of more PV cells. Solar panel direction depends upon

the maximum point of the solar radiation, and the radiation is absorbed. The power is stored in battery or directly

connected to the dc-dc converter for using the dc load.A multiple-input DC–DC converter is useful to obtain the regulated output

voltage several input power sources such as a solar and fuel cell source. A basic block diagram shows that solar

energy source is connected to DC-DC Converter transfers energy to the load.

FIG.1.EXSISTING

SYSTEM

Photovoltaic technology is the one that converts

solar energy directly into electricity, through the use of solar cells or

similar devices. A solar cell constitutes the basic unit of a PV generator

which, in turn, is the main component it. A photovoltaic generator, also known

as a photovoltaic array, is the total system consisting of all PV modules

connected in series or parallel with each other .Solar energy, along with other

renewable energy resources, that does not deplete in source, is reliable, and

environment-friendly. Especially, solar power is arguably the

cleanest, most reliable form of renewable

energy available, and that can be used power home. Solar

owered photovoltaic(PV) panels convert the sun’s rays into

electricity by exciting electrons in silicon cells using the photons of light

from the sun.

II.Z- SOURCE INVERTER

Traditional

single-phase voltage-source converter (abbreviated as V source converter).The

main converter circuit, is feed by dc voltage source with large capacitor .The

dc voltage source can be a battery, diode rectifier, fuel-cell stack, and/or

capacitor.F2our switches are used in the main circuit; each is composed of a

power transistor and freewheeling diode to provide bidirectional current flow

and unidirectional voltage blocking capability. The V-source converters are

widely used. There are two

FIG.1.

Traditional v- Source Inverter

the traditional

single-phase current-source converter (abbreviated as I-source converter)

structure

Z-source inverter (ZSI) which is based on Z-source

network can be used to buck and boost the output AC voltage, which is not

possible using traditional voltage source or current source inverters. Also the

ZSI has the unique ability to short the dc link, which is not possible in the

traditional voltage source inverters. This improves the reliability of the

circuit .Actually concept of boosting the input voltage is based on the ratio

of “shoot-through” time to the whole switching period. Z-source converter where

an impedance network is placed between d.c. link and inverter. Z-source

inverter (ZSI) provides a greater voltage than the d.c. link voltage. It

reduces the inrush current &hormonics in the current because of two

inductors in z source network. It forms a second order filter &handles the undesirable

voltage sags of the dc voltage source.

FIG.2.Topology of the single phase Z-source inverter

Where the impedance network is placed between the

power source and the single phase inverter The presence of 2 inductors & 2

capacitors in Z-source network, allows both switches of same phase leg ON state

simultaneously, called as shoot-through state & gives boosting capability

to the inverter without damaging the switching devices. During shoot through

state energy is transferred From capacitor To inductor & hence Z-source

inverter(ZSI) gains the voltage boosting capability Diode is required to

prevent the discharge of overcharged Capacitor through the source.

III.MODES OF OPERATION

This shoot-through zero state (or vector) is not

present in the traditional VSI, otherwise shoot-through would occur. This extra

zero state (vector) is called the shoot through zero state (or vector). This

shoot-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 legs

The Z-source network has accomplished the

shoot-through zero state. This shoot-through zero state gives the special

buck-boost feature to the inverter. Figure-6.1 depicts the equivalent circuit

of the ZSI when seen from the dc link . The inverter bridge is similar to a

short circuit when the inverter bridge is in the shoot-through zero state, as

depicted in whereas the inverter bridge

becomes an equivalent current source as depicted in Figure-6.3 when it is in

one of the six active states . The inverter bridge can also be illustrated by a

current source with zero value (i.e., an open circuit) when it is in one of the

two conventional zero states.

FIG.2 Equivalent Circuit of ZSI when

viewed from dc link

FIG.3 Equivalent Circuit of ZSI in Shoot-through state

FIG.4 Equivalent Circuit of ZSI in Active State

It is supposed that L1 is = L2, and C1 = C2. The

output ac voltage equation of PWM based ZSI

is given by:

………..(1)

Where Vac is maximum sinusoidal inverter output

voltage, B is boost factor, M is the modulation index and Vo is input dc

voltage. The product (B.M) is called inverter gain and is expressed by G.

So, equation (1) can be written as

Vac = GVo/2

………….. (2)

Boost factor is decided from the given relation

…. (3)

IV.SIMULATION

DIAGRAM

FIG.1 SIMULATION OF

HYBRID SYSTEM

FIG.2

SIMULATION OF FUEL CELL

V.SIMULATION RESULTS

FIG.1

SOLAR CELL INPUT

FIG.2 FUEL CELL INPUT

FIG.3 DC OUTPUT

FIG.4

AC OUTPUT

VI.CONCLUSION

Hybrid energy system

that combines Photovoltaic (PV) and hydrogen fuel cell energy using z source

inverter is simulated. The output voltage from combined solar energy and hydrogen fuel cell energy is regulated using

z source inverter. Two different types of loads (ac and dc load) is used. The

simulation is done with help of MATLAB software and simulation results are

obtained. In future the same circuit can be extended for more than two sources.

REFERENCE

1 Edwin

Deepak., “Performance analysis of z source cascaded h-bridge multilevel inverter based on multi

carrier pwm techniques.”

2

S.Satchya, C.Karthikeyan,Fuzzy logic based z source inverter for hybrid

energy resources.

3

T.Lakshmikanth, C.K.Rambabu, R.Punyavathi “Z source multilevel inverter

based pv generation system”

4 Milchilegovo, Dimitrivinnikov, Ryszarad

“Impedence source inverterbbased high power dc-dc converter fuel cell

application”

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 z

sourced dc-dc converter for renewable applications”

7

Daniel pradeep, Damodharan.S, vidhya, Arun.V.S,Rajkumr.m”Innovative

dc-dc converter for hybrid energy sources using multi inputs”