Overvoltage suppression method for DC microgrid under inter-pole short-circuit fault

Aiming at the problems that the existing methods do not fully consider the influence of fault states and have poor overvoltage suppression effects and irregular voltage waveforms, an overvoltage suppression method for DC microgrids under inter-electrode short-circuit fault (SCF) conditions is studied and proposed. First, we construct the structure of the DC microgrid and analyze the fluctuation factors of the DC bus voltage (DBV), determine the bus voltage level and deviation, and innovatively introduce a four-threshold DBV control strategy tailored for the inter-pole SCF conditions. Second, centering on the inter-pole SCF scenario, error tests were conducted on the voltage transformers and current transformers in the DC microgrid. For the first time, the transformer error measurement was integrated into the overvoltage suppression framework. Finally, a method for formulating the regulation domain of the voltage control vector based on the photovoltaic grid connection conditions is proposed. The experimental results show that this method can effectively suppress the overvoltage under the inter-electrode SCF condition. The voltage fluctuation range is narrowed to ±8.3 V, the waveform distortion rate is reduced to 1.5%, and the fault recovery time is shortened to 48.9 ms. The voltage ripple rate is only about 5%, which is more than half lower than the 18% of other control schemes. This method can effectively suppress overvoltage under inter-pole SCF conditions, output regular voltage waveforms, and ensure safe operation of the power grid.