Enhancing Power Sharing in Bipolar DC Microgrids with Impedance Shaping Schemes

The hybridization of DC power supply systems with AC smart distribution networks provides several advantages and represents a promising approach for modern green energy infrastructure. These systems involve the connection of multiple DC distributed generators (DGs) in parallel to supply power to local and common DC loads. In terms of flexibility, affordability, size, and ease of control, DC microgrids outperform AC microgrids. However, due to variations in electrical (and physical) distances between the sources, voltage drops occur, leading to imbalances in load power distribution among the DGs. In DC microgrid architectures, the bipolar configuration is seen to be more economical and practical. In islanded system, one major issue is power sharing which is solved by the virtual resistance (VR) technique. This paper validates control techniques for changing the virtual resistance (VR) values in a self-regulating way to provide better proportional power sharing amongst distributed generation (DGs) for DC bipolar microgrids. Matlab-Simulink is used for validating the control strategies. The simulations consider linear and non-linear self-regulating virtual resistance with linear and non-linear droop controllers. Different ratings of DC-DC converters, and different types of DC loads such as constant resistance, constant current, constant power load (CPL), and dynamic (motor) loads are considered. Verification for a meshed network is also shown.