The function rotation_dq calculates the matrix R_dq that is the restriction of R_dqo from dqo to dq.
The matrix R_dqo rotates dqo variables around the o-axis in dqo-space with arbitrary angle theta.
It takes the form
[cos(theta), -sin(theta), 0] R_dqo(theta) = [sin(theta), cos(theta), 0] [ 0, 0, 1]and has the real eigenvector
{0, 0, 1}in the dqo reference-frame.
Coefficient matrices of the form (symmetrical systems)
[x, 0, 0 ] X = [0, x, 0 ] [0, 0, xo]are invariant under transformations R_dqo
The connection between R_dqo and R_abc is the following
R_dqo = P0*R_abc*P0'.with P0 the orthogonal transform 'Transforms.P0'.
function rotation_dq extends Icons.Function; input SI.Angle theta "rotation angle"; output Real[2, 2] R_dq "rotation matrix"; end rotation_dq;