Presynchronization of Weak Source in Microgrid

This letter deals with connection of a master-slave controlled microgrid with a grid or an alternative grid-forming source (AGFS). To match the microgrid frequency, phase and voltage with those of the incoming AGFS, a grid forming master VSC uses secondary control, typically in form of a pre-synchronization to make such connection seamless, whether the microgrid is grid-interactive or standalone. However, the contemporary control techniques are sluggish, cause phase-frequency interplay, transients, phase jumps, and notably, they do not deal with a weak incoming source. These limitations are addressed by a novel pre-synchronization control presented in this letter. The proposed technique is simulated using MATLAB/Simulink and validated on a lab test-bench by implementing the control algorithm on a DSP platform. The control performance shows a quick and transient-free pre-synchronization even under disturbances in the AGFS output.