  We propose a new method for generating semidefinite relaxations of optimal
power flow problems. The method is based on chordal conversion techniques: by
dropping some equality constraints in the conversion, we obtain semidefinite
relaxations that are computationally cheaper, but potentially weaker, than the
standard semidefinite relaxation. Our numerical results show that the new
relaxations often produce the same results as the standard semidefinite
relaxation, but at a lower computational cost.
