Distributed power flow analysis for hybrid AC/HVDC grids by network decomposition

This paper proposes a distributed method for solving power flow problems for hybrid AC/HVDC grids using network decomposition. The hybrid system is decomposed at the AC side point of common coupling (PCC) buses. The power flows of the resulting subsystems are solved separately with fixed boundary conditions. The solutions are iterated with updated boundary conditions and coordinated by a master program until convergence. The method described here has a few advantages compared to previous decomposition methods: 1) all grid specific features are encapsulated and handled in self-contained power flow modules, which allows the re-use of existing AC grid PF program with no modification; 2) all equations in a DC grid are solved simultaneously and it requires no additional DC slack bus iterations, which enables the handling of various DC grid modeling features and easy maintenance and upgrade. The proposed method is illustrated by using a test hybrid AC/DC grid consisting of two asynchronous AC systems, one interconnecting multi-terminal DC grid and one embedded multi-terminal DC grid, involving both monopolar and bipolar DC grid designs.