Current Saturation Analysis of Droop Controlled Voltage Source Converter

Droop controlled voltage source converters (VSCs) are very sensitive to overloading due to the low current capacity of switching devices, which implies that VSCs must switch from normal voltage control mode to current control mode at faults or load disturbance and therefore occur transient instability. This paper reviews current saturation phenomenon and reason of droop controlled VSCs. In particular, the boundary conditions between current saturation mode and normal mode are analyzed to express VSC’s static active power critical value at normal mode. Then, the influence of grid parameters and control parameters for current saturation is analyzed. Finally, the effectiveness of theoretical analysis is verified in MATLAB/Simulink and hardware-in-the-loop experiments based on RTLAB. The normal unsaturated VSC’s static active power critical value of theoretical calculation is basically consistent with the simulation.