Systems, methods, techniques and apparatuses of state estimation are disclosed. One exemplary embodiment is a method comprising determining, with a state estimator, a state estimate based on power grid data corresponding to characteristics of a power grid received from a plurality of local controllers; calculating, with the state estimator, a first gain matrix based on a Gauss-Newton method; updating, with the state estimator, the state estimate based on the first gain matrix; calculating, with the state estimator, a second gain matrix based on Newton's method; updating, with the state estimator, the state estimate based on the second gain matrix; and iteratively recalculating the second gain matrix and updating the state estimate based on the second gain matrix until the state estimate converges.