The use of analytical converter loss formula to eliminate DC slack/droop bus iteration in sequential AC-DC power flow algorithm

Abstract

In conventional sequential AC-DC power flow algorithm, DC slack bus iteration (SBI) or droop bus iteration (DBI) is used to update converter loss of the DC slack or droop buses in each AC-DC power flow iteration. The use of SBI or DBI causes additional computational burden on top of the iterative solution of AC-DC power flow, reducing the computational efficiency of the power flow. This letter proposes a novel method to eliminate the SBI or DBI while preserving the accuracy of power flow algorithm. Moreover, a generalized converter loss formula for modular multilevel converters with different submodule types, i.e., half-bridge, full-bridge or mixed half- and full-bridge is derived to eliminate the SBI or DBI. The proposed algorithm is validated using two interconnected AC-DC grid consisting of the IEEE 39-bus AC grid and a 6-terminal DC grid and the IEEE 300-bus AC grid integrated with a 10-terminal DC grid, respectively.