Calculation Method for Critical Permeability of Inverter Power Supply Considering Instantaneous Overcurrent Protection

With the widespread application of clean energy in power systems, traditional distribution networks have become multi-source power grids containing large-scale distributed power sources. When a fault occurs in the distribution network, it is necessary to consider the control strategy and corresponding output characteristics of distributed power sources in order to accurately remove the fault point. Inverter-Interface Distributed Generator (IIDG), represented by photovoltaic power generation, is one of the typical clean energy sources. After IIDG is connected to the grid, it will have a significant impact on the operating characteristics of the instantaneous overcurrent protection in the distribution network, especially the quick break protection on the source side of distributed power sources. This article provides a detailed study of the relationship between the capacity of distributed power sources and fault currents, analyzes the impact of inverter type power sources on the action characteristics of source side instantaneous overcurrent protection in distribution networks, and provides a calculation method for the proportion of distributed energy with complete rejection of current protection to system capacity, i.e. the critical permeability. This provides a reference for subsequent research on current protection and new energy admission capacity.