Coordinated control of voltage regulation and power distribution in islanded DC microgrid

Abstract

[Objective] When traditional droop control is adopted for multiple distributed generators(DG) in the DC microgrid, there are challenges of achieving the control objective of accurate load distribution of multi-DG, stabilizing bus voltage, and ensuring safe operation considering DG capacity. A distributed control strategy for voltage regulation and power distribution in an islanded DC microgrid is thus proposed. [Methods] First, through theoretical derivation, bus voltage drop deviation and current correction deviation were analyzed, and a unified controller was designed, which compensated for the bus voltage drop caused by the traditional droop control while achieving accurate distribution of load power. A current limiting element was introduced to ensure that the output current of each DG did not exceed the limit. The stability analysis of the microgrid system was also carried out in conjunction with the proposed control strategy. Finally, a simulation model was built using MATLAB/Simulink software for verification. [Results] The result show that the proposed single-controller strategy can ensure that the bus voltage is continuously stabilized at the rated value, achieve a high-precision distribution of load power, and remain unaffected by load power fluctuation. The current limiting element can set the maximum limiting current to ensure that the output current of the DG does not exceed the limit. Stability analysis shows that the system is stable and unaffected by the change of the droop coefficient and the cut-off frequency. [Conclusion] The result indicate that the proposed unified controller strategy for bus voltage compensation and load power distribution can effectively achieve multiple control objective, reduce the system communication pressure, decrease the operation complexity, and realize efficient and stable operation of the microgrid.

Keywords

DC microgrid / distributed secondary control / consensus algorithm / voltage compensation / power distribution / influence factor