Method for realizing low-voltage ride-through of doubly-fed fan through modulation and bus sag

Abstract

The invention discloses a method for realizing low-voltage ride through of a doubly-fed fan through modulation and bus sag. According to the method, when the voltage of a grid-connected point drops to0.9 times of a nominal value or below, the output voltage of a rotor-side converter in a linear modulation mode is improved through sag control over the bus voltage of the grid-side converter preferentially; when the induced voltage of the rotor winding exceeds the linear modulation control range of the RSC due to a serious drop fault, the output voltage of the RSC is further improved through a strategy of combining grid-side bus voltage sag control and RSC nonlinear modulation, so that the control capability on the overvoltage of a rotor winding is enhanced. By the adoption of the control method, the range and frequency of crowbar resistance action on the rotor side can be effectively reduced, and the requirement of power grid specifications for the fault ride-through operation capacityof a grid-connected wind turbine generator can be better met.

Description

technical field [0001] The invention belongs to the related field of wind power generation, and in particular relates to a method for realizing low-voltage ride-through of double-fed wind turbines through modulation and busbar drooping. Background technique [0002] In recent years, with the expansion of the single-unit capacity of wind turbines and the rapid increase in the proportion of total installed capacity in the power grid, countries around the world have issued wind power grid-connected guidelines, which put forward clear requirements for the stability and reliability of grid-connected wind turbines. . Grid codes require wind turbines to have low-voltage ride-through capability, including that wind farms should provide reactive current support during grid faults. However, in the event of a power grid drop fault, the rotor side converter (RSC) of a doubly-fed wind turbine is bypassed in order to achieve self-protection and easily triggers the crowbar resistor Crowba...

AI Technical Summary

Problems solved by technology

However, in the event of a power grid drop fault, the rotor side converter (RSC) of a doubly-fed wind turbine is bypassed in order to achieve self-protection and easily triggers the crowbar resistor Crowbar, losing power control over the wind turbine. How to reduce the operating frequency of the crowbar and Range has become an important part of realizing low voltage ride through (Low voltage ride through, LVRT)

[0003] It should be pointed out that when the grid voltage drop is small, the range of the RSC linear modulation area can be increased by appropriately increasing the DC bus voltage of the Grid Side Converter (GSC), thereby slightly improving the doubly-fed asynchronous wind turbine ( Doubly fed Induction Generator, DFIG) low-voltage ride-through capability, but because the DC bus voltage needs to be less than the breakdown voltage of the bus capacitor, the DC bus voltage cannot be increased without limit, and cannot cope with most voltage drop faults, so how to further improve the fault ride-through period The voltage output capability of the RSC becomes another key for double-fed wind turbines to achieve low voltage ride through

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