An Improved Three-phase Power Flow Method for Distribution Network

The paper deeply analyses coupling and asymmetry phenomenon in three-phase power system and comes to the asymmetry of network parameters is the nature of symmetrical component method's failing in three-phase decoupling, so in order to get more accurate result, distribution network elements' modeling must base on abc coordinate. Jacobi matrix formula of three-phase Newton-Raphson algorithm is precisely deduced. Considering the iterative initial value selection problem of Newton method because of long radial network, one method of initial value calculation is put out: For a given three-phase distribution network, first remove the few loop closing branches if exiting and simplify the three-phase system to a single-phase system, use forward-backward algorithm to calculate the single phase system. Then use the single-phase calculation node voltage to construct a positive sequence three-phase node voltage as the initial value of three-phase newton-raphson power flow calculation. The method overcomes the deficiency of the forward-backward and Newton algorithm power flow for their shortcomings respectively, IEEE33 node case shows that this method can solve newton algorithm's initial value selection problem in radiation network and at the same time improve its convergence speed.