Research On Plug And Play Control Strategy For Hybrid AC-DC Microgrid

In recent years,distributed generation has been widely used in microgrids.The traditional power grid is distributed to the user side in the form of AC power,and most distributed generation has natural DC characteristics and most of the consumer equipment on the user side is DC loads.Therefore,hybrid AC-DC microgrids have gradually become the development direction of future intelligent distribution networks.The rapid growth of user-side renewable energy sources and electric vehicles had made the energy interaction between sources,loads,and microgrids more frequent.In addition,the inertia of the microgrid is small and it is easy to be disturbed to cause bus voltage and frequency fluctuations.Therefore,one of the key issues is how to achieve the "plug and play" operation while ensuring that the bus voltage and frequency are stable.In order to realize the "plug and play" operation of distributed power generation,load,etc.,this paper proposeed a dynamic compensation control structure based on a robust residual generator.First,the state-space model of each power electronic converter was established.Secondly,the state space expression of the robust residual generator was derived from the model of each power electronic converter.The model matching theory was used to reduce the dimension of the voltage loop compensation controller.The linear matrix inequality was used to solve the compensation controller of the non-minimum phase system.In order to further improved the dynamic response speed of the converter,according to the circuit model and dynamic compensation structure of the converter,a current loop compensation controller was designed to cancel the internal disturbance brought by the voltage loop compensation controller.In addition,a perturbation distribution strategy was proposed for transient circulating currents between converters in a DC droop system,and a voltage offset was obtained based on the perturbation distribution coefficient.Matlab/Simulink simulation experiments were performed under load switching,unbalanced load switching,distributed generation output power fluctuation,and distributed power switching,respectively,to verify the effectiveness of the proposed control strategy.A small-signal model of the system under the proposed control strategy was established,and the stability is analyzed by the eigenvalue method.Finally,a Star Sim hardware-in-the-loop simulation platform was established for verification.The experimental results prove that the dynamic compensation control architecture based on the robust residual generator proposed in this paper can effectively improve the bus voltage changes caused by sudden power changes;The imbalance at the time of entry is reduced to less than 2%;the circulation effect of the converter switching is reduced.