Low-voltage ride-through realization method for double-fed wind turbine generator with adaptive function on voltage drop

Abstract

The invention discloses a low-voltage ride-through realization method for a double-fed wind turbine generator with an adaptive function on voltage drop. A comprehensive strategy is divided into two modes by considering voltage drop degree and stator variable resistance crowbar protective applicable range: when the grid-connected point voltage U of a wind power plant is within Xp.u-0.9p.u, low-voltage ride-through of the unit is realized by a unloading circuit and grid side dynamic reactive control by combination with a static var generator; and when U is less than Xp.u, low-voltage ride-through of the unit is realized by stator variable resistance crowbar protection, the unloading circuit and the grid side dynamic reactive control by combination with the static var generator, wherein the grid side dynamic reactive control and the stator variable resistance crowbar protection are subjected to parameter adjustment by taking the grid-connected point voltage as the reference so as to realize the adaptive function on the voltage drop degree. By adoption of the method, the low-voltage ride-through capability, the fault ride-through capability and transient state vibration resistance of the unit are greatly improved while the stable operating capability of the unit and the system after fault ride through is improved.

Description

technical field [0001] The invention belongs to the technical field of wind power generation, in particular to a method for realizing low-voltage ride-through of a doubly-fed wind generator (DFIG) adaptive to voltage drop. Background technique [0002] As of the end of 2014, my country's new installed wind power capacity has hit a record high, and the installed capacity of wind power continues to rank first in the world. As the proportion of wind power grid-connected capacity in the power system continues to increase, the impact of wind power off-grid on the safe operation of the grid is becoming more and more serious. In recent years, wind power bases in Jiuquan, Gansu, Xinjiang and other wind power bases in our country have repeatedly experienced large-scale wind turbines being disconnected from the grid due to minor faults in the power grid, which has seriously affected the overall security and stable operation of the power grid system, confirming the impact of wind power...

AI Technical Summary

Problems solved by technology

[0003] At present, the low-voltage ride-through technology of doubly-fed wind turbines is mainly summarized in three aspects according to the principle: 1. The low-voltage ride-through technology that reduces the input power of the unit-side converter, such as pitch angle adjustment, and limits the electromagnetic power of wind turbines, but there are Shortcomings such as slow response speed and long fault recovery time; 2. The low-voltage ride-through technology for eliminating unbalanced power at the DC bus, such as unloading circuits, energy storage devices, and adding auxiliary converters, has the disadvantages of large volume, poor reliability, and energy storage 3. Low-voltage ride-through technology that increases the output power of the grid-side converter of the unit, such as the reactive power control strategy of the unit and reactive power compensation, but there are limited adjustment capabilities and the ability to eliminate imbalances Insufficient and other shortcomings

Through comparison, it is found that the current low-voltage ride-through technology has more or less obvious disadvantages in terms of dynamic response speed, power fluctuation range, structural complexity, economy, fault recovery time, reliability, and adjustment ability.

The biggest disadvantage of the existing low-voltage ride-through technology for doubly-fed wind turbines is that it cannot take into account both the low-voltage ride-through capability of the unit and the stable operation of the unit after the voltage drop is over.

The fundamental reason is that the current low-voltage ride-through technology for doubly-fed wind turbines cannot adapt to changes in grid voltage drops to varying degrees.

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