The present invention discloses a nonlinear modeling method for a synchronous rotating coordinate
system phase-locked loop based on the sector
interval method, belonging to the technical field of nonlinear modeling of grid-connected
converters. Based on the
nonlinear model of the synchronous rotating coordinate
system phase-locked loop, its
operating point is converted to the coordinate origin, and the sine nonlinear link in the phase-locked
loop control is selected as the
fuzzy object; the initial sector interval is designed according to the selected
fuzzy object; the phase-locked
loop control state matrix is determined according to the designed sector interval; the
linear matrix inequality of the phase-locked
loop control system is written based on the state matrix, the common
positive definite matrix P is solved, and the size of the sector interval of the phase-locked loop fuzzy system is adjusted by the presence or absence of the matrix P, that is, the maximum
universe of discourse of the state variables in the
fuzzy object is obtained; the
membership function and fuzzy rules of the phase-locked loop
control system are determined according to the maximum
universe of discourse, and the
equivalent model of the system is constructed by the
membership function and fuzzy rules. The present invention can achieve accurate modeling with fewer fuzzy rules.