Parallel AC-DC interlinking converters in the proposed grid-connected hybrid AC-DC microgrid; planning

The hybrid AC-DC microgrid was developed by connecting the AC, and DC microgrids through a bi-directional AC-DC interlinking converter. The proposed hybrid AC-DC microgrid is created by adding a series converter between the DC bus and utility for compensation of utility voltage power quality problems. The parallel interlinking converters could enhance the capacity of apparent power exchanging between the AC and DC buses, SIC. This paper investigates a tradeoff between two objectives including the annualized investment cost, and reliability index cost, for finding an optimum number (n) of parallel interlinking converters. The solving procedure is performed as a two-stage hierarchical problem. In the first stage, SIC is calculated by considering the power flow satisfaction and power quality improvement. The reliability analysis is done by extraction of the expected apparent power shortage index (EVAS). In the second stage, a decision-making process is adopted to select a proper solution (n) with minimization of the annualized investment cost, and reliability index cost. The simulations are executed on a typical grid-connected proposed hybrid AC-DC microgrid with experimental data of the AC and DC DGs and loads. Simulation results show the effectiveness of the proposed method for finding an optimum number of parallel interlinking converters.