Power grid impedance online identification method and system based on Kalman filtering

The invention discloses a power grid impedance online identification method and system based on Kalman filtering, applied to an inverter grid-connected system, and the method comprises the steps: building a dynamic equation and a measurement equation of system discretization; establishing a dynamic noise variance matrix and a measurement noise variance matrix; giving a state vector initial value and an error variance matrix initial value at an initial moment; establishing a state transition array and a measurement array of the system at the current moment, and calculating an anterior difference array; calculating a system Kalman gain matrix at the current moment; calculating a system state vector estimation value at the current moment; calculating a system error variance matrix at the current moment; and judging whether the result of the state vector is converged or not, if so, ending the process, and calculating to obtain a power grid resistance estimation value and a power grid inductance estimation value c