Voltage and Frequency Control of Off-Grid Inverters Based on Adaptive Droop Control

In the event of a grid fault, inverters are required to operate in islanded mode to ensure that critical loads are not affected, which means that inverters must have the capability to independently support the user-side load in off-grid operation. However, it is difficult for traditional droop control to achieve stable voltage and frequency control under load fluctuations. This paper proposes an improvement to the traditional droop control by introducing adaptive parameters to enable voltage and frequency regulation for off-grid inverters. By dynamically calculating voltage and frequency control errors, the proposed method adaptively adjusts the droop curve intercept to achieve self-restoration of voltage and frequency after disturbances. Furthermore, by collecting information on voltage and frequency fluctuations, the slope of the droop curve is adaptively modified to suppress the amplitude of voltage and frequency fluctuations following disturbances. Simulation results demonstrate the effectiveness and superiority of the proposed control strategy compared to traditional droop control.