A load flow calculation method with optimal multipliers for integrated AC/DC power systems

In this paper, the optimal multiplier technique widely used in the load flow calculation for AC power systems is extended to the integrated AC/DC power systems in detail and in depth. With the implementation of the optimal multiplier modification to the standard simultaneous method, the modified method is able to not only behave well for unsolvable cases by not diverging but also improve the convergence characteristics for solvable cases. To examine the effectiveness of the proposed approach, case studies based on the 22-bus integrated AC/DC power system are demonstrated. The performance of the simultaneous method with and without optimal multipliers for a variety of solvable and unsolvable cases is compared. It is also observed that the solution of the proposed method may oscillate because the optimal multiplier at some iteration is unreasonably large, which provides little assistance and even deteriorates the solution. For this reason, the proposed method is improved further by setting an upper bound on the optimal multiplier. Test results indicate that the improved method could get the faster and more robust performance, regardless of system solvability.