The invention discloses a fan grid-connected sub-synchronous oscillation suppression and high-frequency
harmonic suppression method based on
virtual impedance. Aiming at the problem of sub-synchronous oscillation possibly caused by fan
grid connection under the background of a complex
power grid, an impedance
analysis method is adopted for modeling or measuring to obtain a fan converter impedance model and a
power grid impedance model, different
virtual impedance links are designed at different frequency bands and added into a fan
control system, so that the effects of sub-synchronous oscillation suppression and higher
harmonic suppression are achieved, and the grid-connected stability of the fan is improved. The fan grid-connected sub-synchronous oscillation and high-frequency
harmonic suppression method provided by the invention comprises the following steps of: performing impedance modeling on a fan according to a
hardware structure and a
control system structure of the fan to obtain fan impedance Zinv; carrying out impedance measurement on a
power grid to which the fan is connected by adopting equipment to obtain power
grid impedance Zg; separating sub-synchronous frequency and higher harmonic
voltage components in the grid-connected
voltage, and adding the sub-synchronous frequency and higher harmonic
voltage components into a converter
control system through designed
virtual impedance; and calculating the parameters of the virtual impedance for the sub-synchronous frequency and the higher harmonic according to the national
wind power grid-connected stability requirement and the grid-connected harmonic standard. Therefore, the
system can show impedance meeting the
stability margin under the sub-synchronous frequency and each high-frequency harmonic wave, so that the grid-connected stability of the
system is improved, and the sub-synchronous oscillation inhibiting capability and the high-frequency harmonic wave inhibiting capability of the
system are improved.