Distributed Tie-Line Power Flow Control of Autonomous DC Microgrid Clusters

For microgrids (MGs) owned by different utilities, it is always desirable that the steady state impact of load or generation changes in one MG, does not affect the generation cost in another MG. To ensure this, the power flow through the tie-line is typically regulated at a pre-scheduled value thereby enforcing the individual MGs to manage their respective load at steady state. To this end, this article presents a distributed control scheme to regulate tie-line power flow between two autonomous dc MG clusters. In this article, a unifying hierarchical control scheme based on distributed communication is proposed where the tie-line power flow control based on a pinning control strategy is unified with the distributed optimization and average voltage regulation control loops. The distributed optimization utilizes economic dispatch to minimize the operating costs of the DG, while the average voltage control regulates the MGs average voltage at its nominal value. With the application of this approach, the responsibility of tie-line regulation is distributed in an economic manner without degrading the voltage quality in the system. Time-domain simulations, real-time simulation using Ethernet-based transmission control protocol/internet protocol (TCP/IP) communication, and experimental results are presented to validate the performance of proposed distributed control under normal and faulty system conditions.