Abstract: The conventional grid voltage observation methods of flexible DC power converters need to design

multiple observers，and use multiple filters，which are also affected by DC-offset. So，a grid voltage observation

method of flexible DC power converters based on single sliding mode observer and single third-order generalized

integrator was presented. The grid voltage observation method based on sliding mode observer was first

introduced . Then，by making full use of the advantages of the second-order generalized integrator，a grid voltage

observation method based on single sliding mode observer and single second-order generalized integrator was

proposed. To realize DC-offset suppression，the input-output relationship of the third-order generalized integrator

was further analyzed，a grid voltage observation method based on single sliding mode observer and single thirdorder generalized integrator was finally proposed. The proposed method only needs one sliding mode observer andone third-order generalized integrator to observe the grid voltage and eliminate the influences of DC-offset.

Comparative simulation and experimental researches verify the effectiveness of the proposed method.

      Key words: sliding mode observer；grid voltage observation；second-order generalized integrator；third-order

generalized integrator；DC-offset