electrical seminar

8/3/2019 Electrical Seminar

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IMPEDENCEIMPEDENCE -- SOURCESOURCE

INVERTER FOR MOTORINVERTER FOR MOTORDRIVESDRIVES


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OBJECTIVE

To implement an Impedance Source Inverter for

motor drives. Which can be used as Buck-Boost the

input voltage, minimizes the Harmonics, increases the

efficiency and reduces the cost.


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Traditional Source InvertersTraditional Source Inverters

Voltage Source Inverter.Voltage Source Inverter.

Current Source Inverter.Current Source Inverter.


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Voltage Source InverterVoltage Source InverterProblemsProblems This inverter can be used onlyThis inverter can be used only

for Buck operation.for Buck operation.

For application where theFor application where therequired output voltage is high,required output voltage is high,

an additional dcan additional dc--dc boostdc boostconverter is needed to obtain aconverter is needed to obtain adesired ac output.desired ac output.

This inverter does not haveThis inverter does not haveability to provide rideability to provide ride--throughthrough

during voltage sags .during voltage sags . additional power converteradditional power converterstage increases system cost andstage increases system cost andlowers efficiency.lowers efficiency.

It is immune to noise.It is immune to noise.

M2

M1

V1

50v

D4

1

2

D3

1

2

M6

M5

M4

M3

D6

1

2

D5

1

2

1

2

1

2

C3

1

2

A

B

CTO LOAD


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Current Source InverterCurrent Source InverterProblemsProblems

This Inverter can be used for onlyThis Inverter can be used for onlyBoost operation.Boost operation.

The dc link Filter Inductor is large,The dc link Filter Inductor is large,costly and Contributes to lossescostly and Contributes to losses

The open circuit by noise is theThe open circuit by noise is themajor concernmajor concern

Can cause high voltage spikes onCan cause high voltage spikes onmotor terminals.motor terminals.

Usually not possible to use withUsually not possible to use withmore than one motor.more than one motor.

Lower efficiency due to high powerLower efficiency due to high powerlossloss

M2

M1

V1

50v

D4

1

2

D3

1

2

M6

M5

M4

M3

D6

1

2

D5

1

2

1

2

1

2

L61 2

A

B

CTO LOAD


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FEATURES OF ZFEATURES OF Z SOURCE INVERTERSOURCE INVERTER TheThe impedanceimpedance sourcesource inverterinverter cancan provideprovide BuckBuck--BoostBoost

operationoperation..

TheThe outputoutput voltagevoltage rangerange isis notnot limitedlimited..

ItIt isis lessless effectedeffected byby EMIEMI noisenoise.. ThisThis InverterInverter provideprovide rideride--throughthrough duringduring voltagevoltage sagssags

ItIt reducesreduces thethe harmonicsharmonics thereforetherefore increaseincrease thethe powerpowerfactorfactor andand efficiencyefficiency..

TheThe impedanceimpedance sourcesource inverterinverter costcost isis lowlow.. TheThe impedanceimpedance sourcesource inverterinverter conceptconcept cancan bebe appliedapplied inin

allall acac--acac ,, dcdc--dc,dc, acac--dc,dc, dcdc--acac powerpower conversionconversion


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Proposed ZProposed Z--Source Inverter UnitSource Inverter Unit


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Block DiagramBlock Diagram Impedance SourceImpedance Source

Inverter for A.C DrivesInverter for A.C Drives

AC To DC

Rectifier

IMPEDANCE

NETWORK

Three Phase

Inverter

PWM Thecni

AC

Supply

PWM Technique

Motor


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Z Source Inverter mainly consist of three

parts. They are

1. 3 Diode Rectifier

2. Impedance Network

3. 3 I nverter


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When an ac supply is given to the Diode Rectifier, it converts the ac voltage to dc

voltage.

The diodes are numbered in order of conduction sequences and each diodeconduct for120 degrees.

The conduction sequence of diode is 16, 63, 32, 25, 54, and 41.

The pair of diodes which are connected between that pair of supply lines havingthe highest amount of instantaneous line-to-line will conduct .

It is commonly used in high power

applications.

A3 Diode Rectifier is shown in Fig 1.


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Fig 3 shows a Two Port Impedance Network.

These networks are used in filter sections and are also used as attenuators and

they are sometimes used in preference to ladder structure in some specialapplications.

This lattice network, L1 and L2 are series arms inductances,C1 and C2 are diagonal

capacitances and it consists of split inductors L1 and L2 and capacitors C1 and C2

connected in X-shape.

This network is coupled with the main circuits and the source.


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Inductor and capacitor requirements:

The Impedance source network is a combination of two inductors and two

capacitors. The impedance source network is the energy storage or filtering element for the

Impedance source inverter. This impedance source network provides a second

order filter.

During Buck operation the two inductors (L1and L2) approaches to zero and the

Impedance source network reduces to twocapacitors (C1 andC2) in parallel and

becomes traditional voltage source.

Similarly, during Buck operation the two

capacitors (C1 and C2) approaches to zero,

the Impedance source network reduces

to two inductors (L1 and L2) in series and

becomes a traditional current source.

The equivalent circuit of Impedance Network

is shown in Fig 4.


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When the obtainable dc voltage is given to the inverter it converts the dc

voltage to ac voltage.

Basically, there are two possible schemes of gating the switches. In onescheme, each switch conducts for180o and in othe scheme, each switch

conducts for120 degrees.

Fig 5 shows a 3 phase inverter.


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ApplicationApplication

Variable Speed DrivesVariable Speed Drives

For Fuel Cells in motor vehicles.For Fuel Cells in motor vehicles.

Variable speed drives.Variable speed drives.

Uninterruptible power supplies.Uninterruptible power supplies.

Induction heating.Induction heating.

High voltage dc transmission linesHigh voltage dc transmission lines

The impedance source concept can be applied in allThe impedance source concept can be applied in all

acac--ac , dcac , dc--dc, acdc, ac--dc, dcdc, dc--ac power conversionac power conversion

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