The design of microgrids at the level of distribution systems requires a stable behavior for multiple operation states. The tools used to study the stability of such systems require the estimation of the grid impedance. By the use of the grid impedance estimation around an operation point, it is possible to define a space variable-parameter to obtain a qualitative or quantitative measure from the operation to the unstable boundary. This study presents a comparison of the Kalman filter and the recursive least squares method for the estimation of the grid impedance. The grid impedance is estimated by the technique based on two neighbor operation points. The results were validated by a hardware in the loop and an experimental setup. Finally, the estimated values of the grid impedance of a microgrid are used with a large signal stability study of a dc constant power load.