Decoupled Sequential Power Flow Study in MT-MVDC Distribution Systems based on Novel NR/Estimation-Correction Algorithm

In order to address the gap in comprehensive power flow (PF) analysis of multi-terminal medium-voltage direct current (MT-MVDC) distribution systems, this paper proposes a novel decoupled sequential PF algorithm based on Newton-Raphson (NR)/estimation-correction method. The presented algorithm is designed for an MT-MVDC distribution network and takes into account the PF equations of both generic ac/dc and dc/dc converters. The MVDC PF study is the main focus and the power losses of voltage source converters (VSCs) & dc/dc converters are considered for accurately deriving the dc powers at MVDC links. The proposed algorithm only requires to define a single dc power or current bus type, hence the bus type definition is simplified and the solution of multiple sub-Jacobian matrices can be avoided. A binary search method is employed to correct the estimated initial dc power/current values, which contributes to the searching time reduction. Although an external correction iteration is required in the dc PF derivation, the proposed algorithm still improves on the computation efficiency in comparison with coupled sequential ac/dc PF algorithms. An MT-MVDC distribution network incorporated into IEEE 14 bus system verifies the validity and efficiency of the proposed algorithm.