This paper dealt with a STATCOM (static compensator), considered the combination of the robust performance against commutation failure and low capital cost of filter size in HVDC system. Especially, the main target of this paper is to improve the performance of dynamic voltage control at the inverters of very weak AC systems which has harmonic instability and commutation failure phenomena. PSCAD/EMTDC simulations are presented to demonstrate the robust performance and to validate the proposed system in case of considering a saturation phenomena of HVDC transformer.