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Presented by:

Md. Mustafa Zaved

Department of Electrical and Electronic Engineering

International Islamic University Chittagong

A Comparative Analysis Among PWM Control Z-source Inverter

with Conventional PWM Inverter for Induction Motor Drive

Md. Khurshedul Islam, Md. Mustafa Zaved, Air Mohammad Siddiky

and Khandakar Abdulla Al Mamun

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Why Inverter for Induction Motor?

• In the last century DC motor widely used in the industries for variable speed application.

• In that times induction motor only used for constant speed application due to unavailability of variable frequency voltage supply.

• But now days, with the development of power electronics, it has made possible to supply variable frequency voltage

• Due to the availability of variable frequency voltage, induction motor has taken the workhorse of the industry because of its robustness, less maintenance, high efficiency & low cost

• There are basically two ways to obtain variable frequency voltage1. Cycloconverter 2. Inverting Process

• Cycloconverter is suitable for large applications, such as locomotives and cement mills

• Inverting process is very much suitable for small & medium application • PWM technique is widely used to vary both frequency & voltage

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Conventional Inverters for Motor Drive

On the Basis of AC output waveform, conventional inverters are two types1. Current Source Inverter 2. Voltage Source Inverter

Fig2: Basic Circuit Diagram of Conventional VSIFig1: Basic Circuit Diagram of Conventional CSI

Limitations of CSI:• Boost Converter• Possibility of miss gating• Contains more harmonics• Slower dynamic response

Limitations of VSI:• Buck Converter• Possibility of miss gating• Also contains some harmonics• Required additional boost converter

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Z-Source Inverters for Motor Drive

Advantages of ZSI:• The Source either be voltage or

current source• Provides buck-boost capability• Contains lower harmonics and EMI

noise than conventional

Fig: Basic Circuit Diagram of Z-source Inverter

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Circuitry Arrangement

Fig1 : Simulation circuit arrangement of CSI for Motor Drive Fig2 : Simulation circuit arrangement of VSI for Motor Drive

Fig3 : Simulation circuit arrangement of VSI for Motor Drive

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Comparison of Rotor Speed

DriveTorque

CSI VSI ZSI

0 N-m

4 N-m

7 N-m

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Comparison of Electromagnetic Torque

DriveTorque

CSI VSI ZSI

0 N-m

4 N-m

7 N-m

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Comparison of Rotor Current

DriveTorque

CSI VSI ZSI

0 N-m

4 N-m

7 N-m

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Comparison of Stator Current

DriveTorque

CSI VSI ZSI

0 N-m

4 N-m

7 N-m

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Conclusion

• This paper focus on a comparative analysis of conventional and Z-source inverter for motor drive.

• Z- source fed induction motor provides high starting torque• Quicker operation• Reduces the settling time of rotor and stator currents as

compared to CSI and VSI fed IM.

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