In view of voltage stability issue due to AC and DC faults in multi-DC fed AC systems

a new double-loop voltage stability control strategy based on MMC-UPFC is proposed in this paper. Firstly

the double-loop control structure（current inner loop and double feed-forward control outer loop）is deduced based on the voltage balance equation of MMC-UPFC shunt converter

in which the current inner loop is used to control the voltage stability of AC side. The double feed-forward control outer loop

on one hand

not only provides input reference value for the current inner loop

but also

on the other hand

feedbacks the reactive power compensation

tracks real time reactive power balance situation of the system so to achieve fast stability of voltage at steady and fault conditions. Then

a simulation model based on PSCAD is set up for verification. It is shown by the result that the control strategy proposed in this paper has good control performance under different operating conditions and has wide applicability.