Report of Project 18pulse

7/28/2019 Report of Project 18pulse

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Report

On

Simulation of 18 pilse

converter

Prepared by Guided By

Manish G Prajapati Mr Pramod S Modi

Submitted to

Electrical Engineering Department,

Faculty of technology and engineering

The M.S.U Baroda

Project


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INDEX

1. INTRODUCTION2.SIMULATION CIRCUIT OF 18 PULSE CONVERTER3.SIMULATION RESULT OF 18 PULSE CONVERTER


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1 INTRODUCTION

Eighteen-pulse converter are frequently specified by consulting engineersfor heating, ventilating and air conditioning applications because of their

theoretical ability to reduce harmonic current distortion, but very little

information has been published showing how eighteen-pulse converter perform

under actual operating conditions with unbalanced input line voltages. Thisreport presents test data which demonstrate that eighteen-pulse converter do

not achieve the level of harmonic mitigation most engineers expect and that

these converter may not meet the requirements of IEEE-519 under practical

operating conditions. In the mid 1960s when power semiconductors were only

available in limited current ratings, eighteen-pulse converter provided a simplerand more cost effective approach to achieving higher current ratings than directparalleling of power semiconductors. With this approach a converter could be

easily constructed with almost three times the horsepower available from the

largest six pulse converter. The technique is still employed today in very large

converter applications. In addition eighteen pulse converter have become a

popular approach to harmonic mitigation.

Eighteen pulse rectifiers can be constructed to operate in parallel or

series. In a series configuration, three six-pulse rectifiers, each generating one

third of the DC link voltage, are series connected. The series connection avoids,issues associated with current sharing and eliminates the need for an interphase

reactor. For applications where harmonic mitigation rather than high currentratings are the objective, this solution is much simpler to implement than the

parallel connection. Using the series rectifier connection, it is very easy to

construct an eighteen-pulse converter from a standard six-pulse converter if the

six-pulse converter has its DC bus terminals available or permits access to one

side of the DC bus. Many standard AC converter provide terminals in the DC

bus to accommodate an external DC link choke. These same terminals can be

used to add two external rectifiers converting the converter to eighteen-pulseoperation. The net result is a system solution well within the means of many

system integrators. A typical diagram of a series connected eighteen pulse

converter constructed from a standard sixpulse converter, two external rectifiers

and a conventional 18 pulse isolation transformer appears in figure 1.

The converter has terminals available to connect a DC link choke. These

terminals are used to connect the two external rectifiers in series with the

converter internal rectifier. The eightee pulse transformer is designed to provide


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Fig 18 pulse converter

one third the normal input voltage to each of the three rectifiers at a 20 degree

phase displacement from each other. The 20-degree phase shift is obtained by

phase shifting the transformers secondary windings. The circuit in figure 1

simply uses an isolation transformer with a delta primary, and three delta

connected secondary windings, one shifted + 20 degrees, one shifted -20

degrees and one in phase with the primary.


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2 SIMULATION OF 18 PULSE CONVERTER USING

MATLAB

Fig Shows the simulation circuit diagram of 18 pulse converter.

In this converter two zig zag transformer and one star star 3 phase

transformer are used. Upper zig zag Transformer provide the +20

phase difference and lower zig zag transformer provide the -20 Phase

difference. And the Middle star- star Transformer provide the 0

phase difference. Simulation result shows the output voltage has 18

pulse in the one AC supply cycle.

Fig Simulation circuit diagram of 18 pulse converter


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3 SIMULATION RESULT OF 18 PULSE CONVERTER

Report of Project 18pulse

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