Fan grid-connected sub-synchronous oscillation suppression and high-frequency harmonic suppression method based on virtual impedance

Abstract

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.

Description

technical field [0001] The invention belongs to the technical field of wind power generators, and in particular relates to a method for suppressing subsynchronous oscillation and high-frequency harmonics of wind turbine grid-connected based on virtual impedance. Background technique [0002] Power electronic converters are widely used in wind turbine grid-connected interface devices due to their flexible control and high efficiency. As the installed capacity of wind turbines continues to increase, the interaction between power electronic equipment in wind turbines and AC / DC grids may lead to subsynchronous oscillations. The problem will affect the stable operation of the power system, and even cause the wind turbine to go off-grid in severe cases. [0003] Aiming at the subsynchronous oscillation problem caused by wind turbine grid connection under the complex power grid background, the main analysis methods in the industry are mainly time domain analysis method and frequenc...

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Problems solved by technology

[0005] In order to overcome the deficiencies of the prior art above, the present invention provides a virtual impedance-based wind turbine grid-connected subsynchronous oscillation suppression and high-frequency harmonic suppression method, which solves the problems caused by optimizing control parameters on the basis of improving system stability. The problem that the dynamic performance of the controller has a great influence, also solves the limitation of the suppression effect and the problem of high-order harmonic oscillation that may be brought about by the additional damping control in the process of suppressing the subsynchronous oscillation

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