Coordinated Voltage Control of a Grid Connected Ring DC Microgrid With Energy Hub

This paper presents a supervisory control scheme for the mitigation of voltage regulation issues in a ring dc microgrid with energy hub (EH). The EH is installed with battery banks, proton exchange membrane based fuel cell and electrolyzer stacks representing an energy source-storage unit. In a ring dc system, power injection and absorption at different buses can cause significant voltage deviations throughout the system. This situation is further aggravated due to the intermittent nature of PV power generation. To resolve this issue, a supervisory control scheme is proposed which utilizes a centralized communication system to estimate the network voltage profile and generates desired voltage and current references for the controllable sources. The proposed system consists of dispatchable and non-dispatcable energy sources. Conventionally, in a grid connected system, a bidirectional voltage source converter (VSC) maintains the network voltage while the energy storage system remains at standby/fully charged. This paper suggests to utilize both VSC and EH in a coordinated manner, so as to maintain the voltage at the load terminals within a tolerance band. The proposed ring dc microgrid model is simulated in MATLAB/Simulink environment and the simulation results validate the effectiveness of the supervisory control under wide variations in system operating conditions.