The invention relates to a small
signal impedance modeling method for a second-order generalized
integrator-
phase locked loop (SOGI-PLL). The modeling method comprises six steps: 1, a DC component mu<dq> (t) under a rotating coordinate
system is calculated,
power grid voltage different from a base
wave frequency and a
phase angle small interference
signal are injected respectively under a rectangular coordinate
system, and the relationship between input
power grid voltage under a stationary coordinate
system and an output small
signal under the rotating coordinate system is analyzed; 2, a
transfer function for an imaginary axis output disturbance component and a
phase angle disturbance component under the rotating coordinate system is built; 3, a
transfer function for a
power grid voltage disturbance component and a
phase angle disturbance component under the stationary coordinate system is built; 4, a
transfer function for a
reference current disturbance component and a phase angle disturbance component is built; 5, a transfer function for a
reference current disturbance component and a power
grid voltage disturbance component under the stationary coordinate system is built; and 6, a complete single-phase SOGI-PLL impedance model is built. The modeling method provided by the invention has the advantages of simple and convenient calculation, and accurate modeling.