  In real-time applications involving power flow equations, measuring of
voltage phase angle difference of the connected buses is essential. However, it
needs special techniques to measure voltage angle difference, which may enlarge
the computational burden of the working controller and hence, may make the
control process slow. In this paper, authors investigate the approximation of
angle difference to zero and its effects on the convergence speed and optimal
solutions of a distributed algorithm. To test this approximation, a distributed
nonlinear algorithm is proposed to optimize the multi-objective function which
includes power loss, voltage deviation and cost of reactive power generation,
by controlling the reactive power generations from distributed generators.
Authors investigate the reasons which may outlaw making this approximation and
finally, propose a condition to make such approximation. Importance of making
this approximation in terms of fast convergence of the algorithms is also
illustrated.
