In this paper

the variation of equivalent impedance of grid due to shunt number of modular three level static var compensator is concerned and

on this basis

the improvement strategy to the traditional active damping strategy is proposed.Firstly

single unit small signal equivalent model is set up in this paper

and it is expanded to multiple units of shunt models from PCC.It is concluded from the analysis of the feature of resonance current that in the N units of shunt system the equivalent grid side impedance of single unit is expanded N times.At the same time

the influence of shunt unit numbers of the system on the resonance feature is analyzed and the new active damping strategy of modular three level static var compensator is proposed.Finally

the correctness of the modeling and resonance feature analysis for the multiple units of shunt system is verified by the experimental study and that the proposed new active resonance damping strategy can suppress effectively the resonance of the shunt system.