Comparison of Traditional Inverters and Z-source Inverter.

Presented by:ANKIT N. BRAHMBHATTANKIT N. BRAHMBHATT

P11EL032

Comparison of Traditional Inverters source Inverter.

Presented by:ANKIT N. BRAHMBHATT

Guided By:DR. ANANDITA CHOWDHU

ANKIT N. BRAHMBHATT

P11EL032

OverviewIntroduction.

Z-source Inverter.

• Equivalent Circuit.

• Control Techniques.

• Output Voltage Equation.• Output Voltage Equation.

Comparison of VSI, CSI and ZSI.

Simulation Results.

Conclusion.

References

Overview

Introduction

There exist two traditional inverters: voltagecurrent-source inverters.

Traditional Voltage Source

Introduction

There exist two traditional inverters: voltage-source inverters and

Source Inverter

The VSI is widely used. It, however,theoretical barriers and limitations:

1) The ac output voltage is limitedvoltage or the dc-link voltage hasvoltage. Therefore, the VSI is a buck

For applications where over drivevoltage is limited, an additionalvoltage is limited, an additionalobtain a desired ac output.

The additional power converter stageefficiency.

however, has the following conceptual and:

below and cannot exceed the dc-linkhas to be greater than the ac output

buck (step-down) inverter.

drive is desirable and the available dcdc-dc boost converter is needed todc-dc boost converter is needed to

stage increases system cost and lowers

2) The shoot-through problem bynoise’s misgating-on is a major problem

Dead time has to be provided inproblem, which causes waveform distortion

Traditional Current-source Inverter

electromagnetic interference (EMI)problem to the inverter’s reliability.

in the VSI to prevent shoot throughdistortion.

source Inverter

The CSI has the following conceptuallimitations:

1) The ac output voltage has to be greaterfeeds the dc inductor. Therefore, the CSI

For applications where a wide voltagedc buck converter is needed.

The additional power conversion stageefficiency.efficiency.

2) At least one of the upper devices andgated on and maintained on at any timedc inductor would occur and destroy the

The open-circuit problem by EMI noise’sof the inverter’s reliability.

Overlap time for safe current commutationcauses waveform distortion

conceptual and theoretical barriers and

greater than the original dc voltage thatCSI is a boost (step-up) inverter.

voltage range is desirable, an additional dc–

stage increases system cost and lowers

and one of the lower devices have to betime. Otherwise, an open circuit of thethe devices.

noise’s misgating-off is a major concern

commutation is needed in the CSI, which also

Z-Source Inverter

General structure of the Z

Source Inverter

General structure of the Z-source Inverter

Z-source inverter employs a uniqueinverter main circuit to the power source,that cannot be observed in the traditional

To describe the operating principlewill focuses on an application examplepower conversion needed for fuel-cell

Because fuel cells usually produceBecause fuel cells usually producedepending on current drawn from theneeded because the VSI cannot producethe dc voltage.

unique impedance network to couple thesource, for providing unique features

traditional VSI and CSI.

and control of Z-source inverter, weexample of the Z-source inverter for dc-ac

cell application.

produce a voltage that changes widelyproduce a voltage that changes widelythe stacks, a dc–dc boost converter is

produce an ac voltage that is greater than

For such fuel-cell applications Z-an ac voltage greater and less than

Traditional two-stage power conversion for fuel

-source inverter can directly producethan the fuel-cell voltage.

stage power conversion for fuel-cell applications.

Z-source inverter for fuelsource inverter for fuel-cell applications.

Equivalent Circuits of Z

The three-phase Z-source inverter bridgestates unlike the traditional three-phase

The traditional three-phase VSI has

However, the three-phase Z-sourcestate when the load terminals arelower devices of any one phase leg (ilower devices of any one phase leg (i

We call this third zero state the shoot

This shoot-through zero state is forbidden

The shoot-through zero state can beshoot-through via any one phase leg,and all three phase legs.

Circuits of Z-source inverter

bridge has nine permissible switchingphase VSI that has eight.

six active states and two zero states.

source inverter bridge has one extra zeroshorted through both the upper and

(i.e., both devices are turned on).(i.e., both devices are turned on).

shoot-through zero state.

forbidden in the traditional VSI.

be generated by seven different ways:leg, combinations of any two phase legs,

The inverter bridge is equivalentbridge is in the shoot-through zero state

Equivalent circuit of the Z-source inverter when the inverter bridge is in the shootthrough zero state.

to a short circuit when the inverterstate.

source inverter when the inverter bridge is in the shoot-through zero state.

Whereas the inverter bridge becomesin one of the six active states.

Note that the inverter bridge can bewith zero value (i.e., an open circuit)traditional zero states.

Equivalent circuit of the Z-source inverter when the inverter bridge is in nonshoot-through switching states.

becomes an equivalent current source when

be also represented by a current sourcecircuit) when it is in one of the two

source inverter when the inverter bridge is in through switching states.

Control Techniques of Z

All the traditional pulse width modulationto control the Z-source inverter.

There are three main techniques for

• Simple Boost Control• Simple Boost Control

• Maximum Boost Control

• Maximum Boost Control with 3rd

Control Techniques of Z-source inverter

modulation (PWM) schemes can be used

for control of Z-source Inverter

Harmonic Injection

Simple Boost Control

-10

-5

0

5

10

Contr

ol sig

nals

0 0.01 0.02 0.03 0.04

0 0.01 0.02 0.03 0.040

0.5

1

Gate

puls

es

of

Sap

0 0.01 0.02 0.03 0.040

0.5

1

Time (second)

Gate

puls

es

of

San

Simple Boost Control scheme for ZSI

Simple Boost Control

Carrier

Va

Vb

Vc

Vp

Vn

0.05 0.06 0.07 0.08 0.09 0.1

0.05 0.06 0.07 0.08 0.09 0.1

0.05 0.06 0.07 0.08 0.09 0.1

Time (second)

Simple Boost Control scheme for ZSI

Output Voltage The peak dc-link voltage across inverter

Where, is peak value of dc-link voltage

is Boost Factor expressed as

iv

B

=

−

=

TTT

TB

1

0ˆ VBv

i×=

Where, is Total time period of onezero state time period and is Time period

×−

=

−

=

T

TTTB

0121

T

1T

Output Voltage Equationinverter bridge can be written as

…..…………… (1)

voltage and is input dc voltage.

…..…………… (2)

0V

T

switching cycle and is Shoot-throughperiod of non shoot-through state.

T

T0

0T

Output peak phase voltage from the inverter can be expressed as

Where M is modulation index. Using (1) & (3), can further express as

2

ˆˆ

i

ac

vMv ×=

2ˆ 0

VBMv

ac××=

For the traditional VSI with PWM we have well known relationship

From (4) the output voltage can be stepped up and down by choosing an appropriate buck-boost factor, ,

2ˆ

0V

Mvac

×=

BB

Output peak phase voltage from the inverter can be expressed as

…..…………… (3)

Where M is modulation index. Using (1) & (3), can further express as

…..…………… (4)

acv

For the traditional VSI with PWM we have well known relationship

…..…………… (5)

From (4) the output voltage can be stepped up and down by choosing an

The buck-boost factor, , is determinedfactor, B. The boost factor, B as expressed(i.e., interval ratio) of the shoot-throughstates of the inverter PWM.

Note that the shoot-through zero stateinverter, because it equivalently produce

MBB

=

BB

inverter, because it equivalently produceterminal. The available shoot-throughthat is determined by the modulation index

…..…………… (6)

determined by the modulation index, M and boostexpressed in (2), can be controlled by duty cyclethrough zero state over the nonshoot- through

state does not affect the PWM control of theproduce the same zero voltage to the load

BM ×

produce the same zero voltage to the loadperiod is limited by the zero-state period

index.

Comparison of VSI, CSI and ZSI.VSI CSI

Buck Inverter (Step-

down) only

Boost Inverter

only

Sensitive to EMI noise.

Shoot-Through is a

Sensitive to EMI

Open circuit

major problem. inductor is

problem.

Comparison of VSI, CSI and ZSI.CSI ZSI

Inverter (Step-up) Buck-Boost Inverter (both

step up and down)

EMI noise.

circuit of dc

Shoot-Through and open

circuit of dc inductor are

a major not problems in this case.

Shoot-Through is created

intensely to boost dc-link

voltage.

VSI CSI

If output voltage required

is higher than input

voltage then additional

boost converter is

required. Additional

If output

required is

input voltage

additional

converter isrequired. Additional

power conversion stage

increases cost and lowers

efficiency.

converter is

Additional

conversion

increases

lowers efficiency

CSI ZSI

output voltage

lower than

voltage then

buck

is required.

Both higher and lower

output voltage can be

provided using single

stage power conversion

only. This reducesis required.

power

stage

cost and

efficiency

only. This reduces

complexity, cost and

increase efficiency.

VSI CSI

For adjustable speed

drive application VSI are

only applicable where

For adjustable

drive application

only applicable

input voltage is always

higher than required

output voltage.

input voltage

less than required

voltage.

CSI ZSI

adjustable speed

application CSI are

applicable where

For adjustable speed

drive application ZSI can

be used for any range of

voltage is always

required output

input and output voltage.

Simulation Results

VSI

Simulation circuit

ZSI

Simulation Results

Simulation circuit

Impedance NetworkImpedance Network

LC Filter

InverterInverter

Load

Simulation Parameters

Z-source Impedance values :

Input voltage (dc) :

Output voltage (ac) :

Load :Load :

Carrier wave frequency :

Cut-off frequency of LC-filter :

Simulation Parameters

L1=L2=200µH and C1=C2=400µF

400V

415V, 50Hz

RL load of 10Ω and 20mHRL load of 10Ω and 20mH

10 KHz

1 KHz

Simulation results of the ZSI withresults of the traditional VSI with SPWMmodulation index and same load is shown

0

200

400

600

Output Voltage (Volt)

0.1 0.11 0.12 0.13 0.14 0.15-600

-400

-200

0

Time(Second)

Output Voltage (Volt)

Output Line Voltages of ZSI

with simple boost control scheme andSPWM scheme for same input, sameshown

0.15 0.16 0.17 0.18 0.19 0.2

Time(Second)

Output Line Voltages of ZSI

0

100

200

300Output Voltage (Volt)

0.1 0.11 0.12 0.13 0.14 0.15-300

-200

-100

Time(Second)

Output Line Voltages of VSI

0.15 0.16 0.17 0.18 0.19 0.2

Time(Second)

Output Line Voltages of VSI

400

500

600

700

800

900

1000D

C lin

k V

oltage

(Volt)

0.1 0.11 0.12 0.13 0.14 0.150

100

200

300

Time (second)

DC

lin

k V

oltage

DC-Link Voltage of ZSI

0.15 0.16 0.17 0.18 0.19 0.2

Time (second)

Link Voltage of ZSI

Conclusion

The Z-source inverters employs a uniqueto couple the Inverter main circuitunique features that cannot be observedand current-source inverters.

The Z-source converter overcomesbarriers and limitations of the traditionalbarriers and limitations of the traditionalcurrent-source inverter and provides

The Z-source inverter can boost–size, increase efficiency, increase reliability

Conclusion

unique impedance network (or circuit)circuit to the power source, thus providing

observed in the traditional voltage-source

overcomes the conceptual and theoreticaltraditional voltage-source inverter andtraditional voltage-source inverter and

provides a novel power conversion concept

–buck voltage, minimizes componentreliability and reduce cost.

Reference

1) F. Z. Peng, “Z-source inverter,” IEEE Trans510, March/April 2003

2) T.Meenakshi, K.Rajambal, “IdentificationInverter”, Asian Power Electronics Journal,

3) Miaosen Shen, Alan Joseph, Jin Wang,“Comparison of Traditional Inverters and“Comparison of Traditional Inverters andIEEE Power Electronics in Transportation

4) B.Y. Husodo, M. Anwari, S.M. Ayob, TaufikInverter Control Methods”, IEEE IPEC 2010

5) F.Z. Peng, M. Shen, and Z. Qiang, “MaximumIEEE Transactions on Power Electronics,

Reference

Trans. Industry Applications, vol. 39, pp. 504–

“Identification of an Effective Control Scheme for Z-sourceJournal, Vol. 4 No.1 April 2010.

Wang, Fang Z. Peng and Donald J. Adams,and Z-Source Inverter for Fuel Cell Vehicles”and Z-Source Inverter for Fuel Cell Vehicles”

Transportation, pp. 125-32, October 2004.

Taufik, “Analysis and Simulations of Z-Source2010.

“Maximum Boost Control of the Z-Source Inverter”,vol. 20, no.4, pp. 833-838, July 2004.

Thank you.Thank you.