Comprehensive control method of double-fed wind power system under asymmetrical grid voltage condition

Abstract

The invention discloses a comprehensive control method of a double-fed wind power system under the asymmetrical grid voltage condition, which is characterized by comprising the following steps of: 1, establishing a POI (point of interconnection) positive sequence voltage and negative sequence voltage mathematical model of a wind power generator under the condition of asymmetrical voltage sag so as to obtain control methods for controlling POI currents to carry out positive sequence voltage support and negative sequence voltage rejection in sequence; 2, establishing a stable-state mathematicalmodel of a double-fed generator; 3, establishing a decoupling and synthetizing control method of positive sequence active and reactive voltage and negative sequence active and reactive voltage of a converter; 4, establishing the optimum allocation plan of positive and negative sequence currents in the positive sequence voltage support and negative sequence voltage rejection methods, and calculating amplitude values and phase positions of positive and negative sequence synthesizing currents of targets output by a generator system; and 5, carrying out PWM (pulse width modulation) voltage control of a current closed-loop on the converter. The method is used to obviously improve grid-connected conditions of the double-fed wind power system in a wind power station under the asymmetrical grid voltage condition.

Description

technical field [0001] The invention relates to a ride-through control method of a doubly-fed wind power generation system under an asymmetric drop state of grid voltage, and belongs to the technical field of wind power generation. Background technique [0002] Due to the maturity and stability of the doubly-fed wind power generation system, many wind farms are dominated by doubly-fed wind turbines. In recent years, the research on doubly-fed power generation systems in the wind power industry has mainly focused on the operation under grid faults and low-voltage ride-through of the system. Many low-voltage ride-through control strategies of wind power generation systems are aimed at symmetrical grid voltage drops, but more than 80% of grid voltage drops are asymmetrical drops. A small voltage asymmetry will cause a high degree of imbalance in the stator current, resulting in unbalanced heating of the stator windings and torque ripples in the generator, which will eventually...

AI Technical Summary

Problems solved by technology

A small voltage asymmetry will cause a high imbalance of the stator current, which will cause the heating of the stator winding to be unbalanced and cause the generator to generate torque ripple, which will eventually cause the power input to the grid to oscillate

Due to the lack of control strategies for asymmetric voltage faults, some high-power wind power generation systems will be disconnected from the grid

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