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The grid-connected control technology of ac/dc hybrid microgrids affects power quality, stability, robustness, and other indicators. In order to achieve high-quality and reliability of ac/dc hybrid microgrids connected to a distributed network, this paper proposes a robust control method for grid-connected ac/dc hybrid microgrids based on mixed sensitivity. First, the grid-connected model of ac/dc hybrid microgrids is equivalent to the superposition theorem; then, the problem of how to control grid-connection can be transformed to the problem of how to deal with mixed sensitivity by considering the influence of the distributed network on ac/dc hybrid microgrids as a disturbance. Second, the grid-connected robust controller can be obtained by using the Riccati method repeatedly, which can ensure good nominal performance of the system and enhance the robustness of the system. Finally, the validity and feasibility of the proposed control method can be verified with three simulation conditions. [ABSTRACT FROM AUTHOR]

• Fitted the efficiency curve function of BPCs based on the efficiency data. • Calculated the economically optimal distribution scheme of BPCs. • Proposed an economically power distribution method for BPCs. • Proposed a nonlinear control method for BPC which used to control the dc bus voltage. Parallel bidirectional power converters (BPCs) can support each other's power between the ac grid and the dc grid, and they play an important role in maintaining the dynamic power balance in an ac/dc hybrid microgrid. This paper proposes a nonlinear coordinated control strategy for parallel BPCs when the hybrid ac/dc microgrid operates in grid-connected mode. First, taking the minimization of the sum of the power losses of the BPCs as the objective, this strategy can obtain the economically optimal distribution scheme for power transmission among parallel BPCs according to the efficiency curves of the BPCs. Second, distributing the transmission power according to the economically optimal distribution scheme rather than distributing the transmission power equally among parallel BPCs can not only reduce the sum of the power losses of the BPCs but also increase the power margin of the BPC that is used to control the dc bus voltage after a power disturbance. Third, a nonlinear control method that is based on the state-dynamic feedback linearization theory is proposed for the BPC that is used to control the dc bus voltage. This method can quickly re-establish the dc bus voltage if a power disturbance occurs and realize high dynamic voltage quality. Finally, the performance of the proposed control strategy is verified in MATLAB/Simulink. [ABSTRACT FROM AUTHOR]