Diffusion-based distributed secondary control scheme in islanded AC microgrids

Distributed control methods based on consensus algorithms have been fully investigated in recent years. However, convergence and stability issues of the consensus algorithms can be very tricky on some occasions. Established on hierarchical architecture, a dynamic diffusion algorithm-based distributed secondary control is proposed for islanded ac microgrids. Firstly, mathematical analysis shows the diffusion algorithm generally has a faster convergence speed and a larger stability region. Further, conforming to the discrete nature of this kind of distributed protocol, an overall system model containing the microgrid plant, the primary controller, and the secondary controller are established in the discrete domain with the communication delay. Moreover, parameter sensitivity and stability region of some key control parameters are analyzed based on the eigenvalue contours. To verify the effectiveness of the proposed method and the correctness of the theoretical analysis, a simulation with three parallel voltage source inverters is presented. Real-time simulation results on OPAL-RT platform approve that the proposed distributed secondary control surpasses the consensus-based approach with faster convergence speed, higher parameter tolerance, and larger stability region.