Load flow based on Newton's method using Norton equivalent circuit for AC-DC multiterminal systems

Abstract

This paper presents the Newton-Raphson approach using new equations to the power-flow analysis in steady-state for multiterminal DC-AC systems. A flexible and practical choice of per-unit system is used to formulate the DC network and converter equations. A converter is represented by Norton's equations of a current source in parallel with the commutation resistance. Unlike in previous literature, the DC network equations are used to derive the controller equations for the DC system using a subset of specifications. The specifications considered are power at all terminals except the slack terminal where the DC voltage specified. Similar Newton's approach uses six variables per converter but this approach uses three variables per converter: This property provides less storage requirement and computation time than the others. Unlike the proposed paper, in some papers based on Newton's method the main problem is that some oft he diagonal elements of Jacobian matrix are weak and zero, and partial pivoting in the solution by triangular reduction is essential.