Problem in "abc - dq0" Transformation using "Phase-Locked Loop" in Simulink Model.

Hello all,

I am using a very simple block to transfer from 3 pahse abc voltage to 2 phase dq using the attached model. I am not using the built-in model as I am told by my instructor to implement the 3-phase PLL (phase-locked Loop) to implement the transformation.

I am expected to see the output DQ as 1 and 0. 0 for Q voltage and 1 for D, if the input magnitude is 1 ofcourse.

Now, in the attached file, I have a simple function and the output of the DQ block is fed into a PLL loop made by me to feedback the (wt = omega*t) component which is used in the function block.

Can anyone tell me why am I getting a -1 instead of a 1 for D voltage.

Function block codes...

First block -

function [Va,Vb,Vc] =  ThreePhaseSystem(a,f,t)
x=2*pi*f*t;
Va = a*sin(x);
Vb = a*sin(x-(2*pi/3));
Vc = a*sin(x+(2*pi/3));
end

2nd Block -

function [Vd,Vq] = fcn(Va,Vb,Vc,w)
Vd = (2/3)*((Va*sin(w))+(Vb*sin(w-(2*pi/3)))+(Vc*sin(w+(2*pi/3))));
Vq = (2/3)*((Va*cos(w))+(Vb*cos(w-(2*pi/3)))+(Vc*cos(w+(2*pi/3))));
end

The "Q" output of this block is fed into a PI controller with Kp = -100, and Ki = -10000. Output is integrated again and fed into the 2nd block.

Your help will be greatly appreciated.

Thanks, Faisal Khan

[Azzi Abdelmalek]

What is w?

[Faisal]

w is the phase. theta from the equation.

[Azzi Abdelmalek]

Its not easy to guess without your model

Answer 1

[Sabin]

Without a model is difficult to tell. My guess is that the angle is not correct, may have an offset that is not accounted for.