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This paper proposes a novel distributed bilayer coordinated control scheme (BCCS) to realize the autonomous economic operation of islanded hybrid AC/DC microgrids, which only requires a sparse communication link. In the lower layer, the optimal power reference iterative algorithm (OPRIA)-based droop control is proposed to realize the economic dispatch of each subgrid individually, while the frequency of AC subgrid and the bus voltage of DC subgrid are regulated to their rated values. Then, the upper-layer control for the interlinking converter is designed to achieve the global economic operation of the hybrid AC/DC microgrid through optimizing the exchanging power between AC and DC subgrids. The proposed BCCS has the advantage of reaching the economic operation and frequency/voltage regulation simultaneously for the hybrid AC/DC microgrid. Besides, the proposed BCCS realizes the stable and economic operation with less communication, flexible controllability, and good compatibility of renewable energy sources. Numerical simulation results based on Matlab/Simulink verify the effectiveness and excellent performance of the proposed BCCS even with the integration of renewable energy sources, and the test based on RT-LAB illustrates the good real-time performance of the proposed control scheme.This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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In wind farms, the uncertainty of wind power and the incoordination of multiple time scales increase the difficulty of voltage/var control (VVC), and result in the reactive power output of VVC devices becoming unreasonable. This will decrease the power quality and even cause the voltage collapse of wind farms at large voltage deviations. For these problems, hierarchical control of VVC devices is a promising solution, as VVC devices can adjust the reactive power output in different control strategies. Therefore, this paper proposes a three‐stage robust voltage/var optimal control strategy for wind farms. The robust optimization model is introduced to solve the VVC problem caused by the uncertainty of wind power in this strategy. Besides, compared with traditional VVC strategies, the proposed strategy can coordinate different control stages and VVC devices at multiple time scales by combining centralized and local VVC strategies, which achieves voltage/var optimal control objectives. Simulation results demonstrate the good performance of the proposed strategy in mitigating system voltage violation rate and power loss of the wind farm.

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