Z-SOURCE INVERTER FOR ADJUSTABLE SPEED DRIVES

Presentation by

M. PURUSHOTHAM

Roll.No: 9781D5405

M.Tech (PE&ED),II Year

Under the Guidance of

G.RAVI BABU

Department of Electrical & Electronics EngineeringSRI VENTATESWARA COLLEGE OF ENGINEERING & TECHNOLOGY R.V.S.Nagar,Chittoor-517127

ABSTRACT

This paper presents a Z-source inverter system and control for adjustable speed drives (ASD).

The Z-source inverter employs a unique LC network to couple the inverter main circuit to the diode front end. The Z-source converter overcomes the conceptual and theoretical barriers and limitations of the traditional converters

INTRODUCTION

THERE EXIST TWO TYPES OF TRADITIONAL CONVERTERS

voltage-source (or voltage-fed) and current-source (or current-fed) converters (or inverters depending on power flow directions)

The voltage-source converter is widely used.

VOLTAGR SOURSE INVERTER

Fig. 1. Traditional Voltage-source converter

Fig. 2. Traditional Current-source converter

CURRENT SOURSE INVERTER

Common problems for both VSI & CSIThey are either a boost or a buck converter and

cannot be a buck–boost converter.

Their main circuits cannot be interchangeable. In other words, neither the V-source converter main circuit can be used for the I-source converter, nor vice versa.

They are vulnerable to EMI noise in terms of reliability.

Z-SOURCE CONVERTER

To overcome the above problems of the traditional V-source and I-source converters.

It employs a unique impedance network (or circuit) to couple the converter main circuit to the power source.

EQUIVALENT CIRCUIT, OPERATING PRINCIPLE,

AND CONTROL The unique feature of the Z-source inverter is

that the output ac voltage can be any value between zero and infinity regardless of the fuel-cell voltage.

The three-phase Z-source inverter bridge has nine permissible switching states (vectors) unlike the traditional three-phase V-source inverter that has eight

This shoot-through zero state (or vector) is forbidden in the traditional V-source inverter, because it would cause a shoot-through.

Fig. 9. Equivalent circuit of the Z-source inverter viewed from the dc link when the inverter bridge is in the shoot-through zero state.

Fig. 10. Equivalent circuit of the Z-source inverter viewed from the dc link when the inverter bridge is in one of the eight non shoot-through switching states.

CIRCUIT ANALYSIS AND OBTAINABLE OUTPUT VOLTAGE

Z-source rectifier/inverter system for adjustable-speed drives.

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