Design of a multifunction novel flexible fault current limiter for AC distribution network.

Based on the separation voltage type of cascaded H bridge-modular multilevel converters (CHB-MMC) and current predictive model control (CPMC) technology, a novel flexible fault-current limiter (NFFCL) is firstly proposed for restraining the negative impact of the distribution network's disturbance in this paper. When a disturbance occurs, the inner-loop CPMC of the multilevel converters establish the value function to offer the specific current, thus increasing the voltage deviation at both ends of the series capacitor or generating reverse harmonic compensation voltage. In that case, three single-phase MNFFCLs can be regarded as variable voltage sources to eliminate the negative effects of faults or harmonics. Owing to the multi-capacitance series structure, the maximum voltage drops of the single capacitance can be predetermined by the number of capacitors. And with the low voltage drop of single capacitance, the output current of the CHB-MMC can also be controlled within an acceptable range. Through the simulation results, the disturbance's negative impact on the non-fault area can be eliminated almost 100%.