Advanced Power Management Algorithm in DC Microgrid Subsystem Controlled by Smart Transformer

Abstract

Smart transformer is excellent solution for integration of AC and DC microgrids with different voltage parameters. It provides the advanced control algorithms to improve the voltage and current quality in LV microgrid and MV distribution grid. It can also be responsible for the proper power management in interconnected AC as well as DC microgrids. Taking into consideration the DC microgrid the power balance and DC voltage level is normally provided by hybrid energy storage system. However the battery capacity is limited and then the additional processes have to be conducted to keep the power balance. The advanced power management algorithm has to considered the communication infrastructure in the microgrid but it also should provide proper power sharing when the communication is corrupted. From the other hand, the power electronics converters connected to the DC microgrid (a smart transformer DC link sub-circuits, RESs or constant power loads) should work with a nominal DC voltage level. Therefore, it should be kept by the control system as long as possible. Using the smart transformer as a control system for the microgrid the energy can be provided in many ways (from MV grid, by AC load reduction or by lower DC voltage in critical situation). Thus, a novel power management algorithm implemented in smart transformer control has been developed and presented. It includes five processes with decision flowcharts based on the battery state of charge. The simulation research has been conducted and briefly described in this paper, proving the proper operation of developed solution.