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Space Vector Pulse Width Modulation--doubt..please Help


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#1 ansha

ansha

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Posted 10 January 2009 - 05:54 PM

Hi all
I am an engineering student from india. I am planning to do a project on speed control of 3 phase induction motor using space vector PWM. Its V/f control...My idea of the project is given below

3 phase ac supply can be represented by a space vector.

Magnitude of space vector represents voltage and speed of rotation represents frequency

for v/f control we have to modify both the above factors

in every inverter branch 1 represents tat phase is connected to +ve, 0 means it is connected to -ve
(dnt knw if im confusing.please c the link below)

http://www.feec.vutb.../03-SmileCz.pdf

so different instants in 3 phase ac cycle can be represented by 8 vectors each represented by

(100, 110, 010, 011, 001, 101, 000, 111)

When the first six vectors are applied in sequence to gates of inverter, it completes one rotation of space vector and thus one cycle of 3 phase ac

The whole vector space is divided to 6 sectors. Suppose the frequency we need is such that space vector complete should complete one rotation in 60ms.So it will have 10ms to complete one sector.To get reduced voltage for required v/f ratio, i will sample this. I mean 1st sector is formed by 100 nd 110. So for example i will sample 100 for 2 sec, 110 for 2 seconds nd remaining time 000 or 111. So i will get an average reduced voltage.
K i was just trying to make u all clear wat i have in mind

I guess the vectors wont be continous nd thus the corresponding 3 phase ac. So i plan to divide each sector to 60 divisions(1 degree each). In each division i will sample by using time formulas given in the above pdf file

Now comesthe doubt.Is wat i said just a theoretical understanding and is the understanding correct. Can i do it in practice.I plan to write the program to generate clock signals using an arduino board.Using the formulas in above link, i will sample 60 times in each sector varying the angle of space vector.Get the frequency from the user, and find out voltage from the v/f ratio. Using formulas the mocroprocessor will calculate time for sampling for tat particular voltage. Also the time alloted for each sector varies according to frequency ie speed of rotation.(hope im not confusing)

With the above said program, can i run a 3kw 3 phase induction motor at different speeds depending on frequency selected by the user

I have only a 220v dc supply available.How can i use it on an inverter so as to produce 400v ac using space vector technique. Is any other components required??

What are my chances of incoporating regenerative breaking to the design and how?? I plan to make inverter using IGBTs.Is it suitable for the task

Thankyou all for reading this patiently. Please help me on this as soon as possible




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