A new version of exact decoupled second order AC-DC load flow in rectangular coordinates

This paper presents a new framework for second order AC-DC load flow in rectangular coordinates. Such a formulation is completely expressible in the Taylor series and contains derivatives up to the second order only, the third and other higher order derivatives being zero. The Jacobian matrix is kept constant and thereby, needs to be computed and triangularised once only in the iterative scheme. The newly developed super second order (SSO) algorithms for the AC system load flow are computationally more efficient and reliable than the Newton-Raphson (NR) and fast decoupled (FD) load flow algorithms. In addition to presenting a sound derivation of the standard version of the SSO load flow, a new version is proposed which presents better performance when applied to a system with critical R/X ratio. Test results are presented, compared and discussed. The proposed method performs satisfactorily and its computational requirements are comparable with those of FD AC-DC load flow