Single-phase fully-controlled thyristor converter simulation using simulink

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Michail
Michail 2016-1-14
评论： ABHISEK BHUJABAL 2018-8-28
Hi!
I am trying to implement a simple single-phase fully-controlled thyristor converter using Simulink.
As load I have placed just an inductor, the firing angle is set to a=60 deg., f=50 Hz and the rms of the voltage source is 230 V. The output voltage is the one on the picture below,
How can I fix the part I have circled? The waveform is supposed to be repetitive, so there should be a negative part as in the next half-periods.

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回答（2 个）

Pavel Dey
Pavel Dey 2016-1-21
As far as I understood from your model is that you are using a pulse to trigger the gate and the input is a sine wave. However, at the beginning the thyrister is simply off since no pulse has yet been applied in the gate. So it wont be affected by the input signal. Hence, the output is simply unaffected by the input sine wave at the initial stage. Once the thyristor is turned on by pulse it provides output and stay turned on until it is reverse biased. Then the other thyristor is turned on. It goes on like this. It is nothing but just that none of the thyristor is turned on at the beginning. It cannot follow the downward signal because it is not at all active then.
If you simply make the firing angle 0, you will observe a rectified sine wave.
I hope that helps.
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Michail
Michail 2016-1-21
The operating principle as you describe it is correct. Unfortunately, setting the firing angle to zero is not the solution. The purpose is to implement a fully-controlled converter instead of just a rectifier. Through the firing angle of the thyristors we are supposed to be able to control the output DC voltage.

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Mohamed Hassanien
Hi Michail,
Unfortunately I have a question for you instead of an answer :) , How did you transfer the firing angle ( 60 degree) to phase delay ( seconds ) so you can use it in the pulse generator ?
In my case I am using the same principle to get variable dc o/p ( 9 12 15 7 ) from 230 AC .. Also, I am using the equation : V(dc) = ((2*Vm)/ pi) * Cos(alpha) to get the alpha, but the problem that I don't know how to use it as phase delay ( seconds ) ?.
Appreciate your help.
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Michail
Michail 2017-2-7
编辑：Michail 2017-2-7
Hello again Mohamed,
I think you miss an sqrt(2) in you formula. The average DC output of this fully controlled converter is Vdc = 0.9*Vs*cosα where Vs is the rms voltage of your source (230V). If you want your output to be 12V then your delay angle should be around 86.67 degrees. What you have to consider is the ripple in your output and how to eliminate it.
I suggest you to have a look in the literature. Mohan, Undeland and Robbins have authored a really great book.
KR, Michail

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