Hierarchical power flow algorithm for standalone hybrid AC/Multi-DC microgrids

Recent development in hybrid ac/dc microgrid has led researchers to study the mixed ac/dc power flow algorithm. This paper proposes a hierarchical approach to solve power flow of islanded hybrid ac/dc microgrids based on the well-established Newton Raphson approach where the ac and dc power flow is solved iteratively. It also takes into account the absence of slack bus in islanded operation, the coupling of ac frequency and dc voltage, as well as the droop control of distributed generations. To achieve power sharing between the ac and dc subgrids, this method incorporates the interlinking converter droop constants in the equation. The algorithm was implemented in Matlab and tested on modified systems involving one ac and single/multiple dc subgrids. Simulation results show the adaptability of the proposed algorithm in solving mixed power flow of several interconnected hybrid grids. Such straightforward and easy-to-implement algorithm will aid the design and planning process of microgrids.