#### 4.2 DC Power Flow

For the DC power ﬂow problem [20], the vector consists of the set of voltage angles at
non-reference buses

| (4.14) |

and (4.1) takes the form

| (4.15) |

where is the matrix obtained by simply eliminating from
the row and column corresponding to the slack bus and reference angle, respectively.
Given that the generator injections are speciﬁed at all but the slack bus,
can be formed directly from the non-slack rows of the last four terms of
(3.32).

The voltage angles in are computed by a direct solution of the set of linear
equations. The branch ﬂows and slack bus generator injection are then calculated
directly from the bus voltage angles via (3.29) and the appropriate row in (3.32),
respectively.