Distributed Secondary Voltage Control in Islanded Microgrids With Consideration of Communication Network and Time Delays

The extensive usage of open communication mechanisms in distributed secondary control of islanded microgrids (MGs) suggests that the effects of the communication network and time delays on system performance cannot be negligible. Based on the relationship between convergence and algebraic connectivity, this paper proposes an optimal design for a directed communication topology and pinning location through the mirror operation and global propagation rates, respectively. Alternatively, a small-signal dynamic model of an MG equipped with time-delayed distributed secondary voltage control is derived, to investigate the delay-dependent stability of MG system in terms of the controller, network and pinning conditions. An analytical formula is then developed to determine the individual delay margins with respect to different sets of controller gains and pinning. Through a series of trials, the qualitative effects of controller parameters and pinning conditions on delay margins can be used to guide the design of both controllers and pinning for the improved system performance. The effectiveness of proposed methodology is verified via the real-time hardware-in-the-loop (HIL) simulations.