Enhancing power flow management in interconnected AC minigrids with back-to-back converters

Abstract

The integration of renewable energy sources (RES) into minigrids presents challenges related to grid stability, load balancing, and efficient energy utilization. Interconnected minigrids, when managed effectively, can maximize RES power utilization, and provide better load support thus enhancing power system reliability. However, achieving seamless power flow between these minigrids requires some creative approaches towards solutions. Back-to-back converters play a huge role in managing power flow within interconnected minigrids. By enabling bidirectional energy exchange, these converters enhance power flow management which entails improving reserve capacity utilization and keeping the frequency in both the minigrids within acceptable range. In this study, the model system comprises two standalone minigrids, each with its own RES, and loads, interconnected to the AC bus via back-to-back converters. A global droop control scheme is applied to manage the power sharing between the interconnected minigrids. The key parameters being monitored are the active power (P) and the frequency (f) and the performance of the back-to-back converters proposed is validated through MATLAB/Simulink simulations and the results compared based on these scenarios: the two minigrids interconnected with the back-to-back converters without global droop control scheme to a global load, and the two minigrids interconnected and operating with global droop control to the global load. The study resulted in the system model maintaining a stable frequency of 60Hz corrected down from 60.3Hz and 60.05Hz during the solar generation dip and a reduced peak ROCOF of 4Hz/s down from 7Hz/s. Load demand also shared equally with each minigrid supplying 0.5 pu active power, contributing to an enhanced power flow management system for interconnected AC minigrids by leveraging back-to-back converters and droop control.