The stable operation of microgrid controlled by grid-forming inverter is extremely critical. The interconnection line of inverter can hardly keep consistent in impedance index, which will cause the trouble that the output power of inverter is not commensurate with its own capacity. The concept of parameter perturbation is introduced to solve the mismatch problem of output power. With the constant perturbation of droop coefficient, the information of optimizing virtual impedance can be obtained from the change of inverter state, and voltage compensation based on active power is established to suppress voltage fluctuations during the perturbation process. The accuracy of the perturbation and voltage compensation is verified in simulation