Comprehensive low voltage ride-through method for doubly-fed fan based on stator series dynamic reactor

Abstract

The invention relates to a comprehensive low voltage ride-through method for a doubly-fed fan based on a stator series dynamic reactor. The method comprises the following steps: when the grid voltagedrop is detected, performing control according to a transient control mode 1, wherein the transient control mode 1 is a comprehensive traversing mode in which the stator series reactor with a large value is input and a RSC adopts a control strategy of active transient flux linkage attenuation, and the setting principle of the large reactor in the mode 1 is to ensure that the peak value of the rotor current does not exceed the limit after the fault occurs; observing the modulus value of the transient induced electromotive force in real time, and switching to a control mode 2 when the modulus value decays to the set threshold value, wherein the setting principle is to ensure that the rotor current does not exceed the limit after reactor witching; restoring the normal control of the fan, andcutting off the series reactor after a delay of 100 ms, when the grid voltage returns to normal.

Description

technical field [0001] The invention relates to a low-voltage ride-through scheme of a double-fed fan, in particular to a comprehensive strategy for improving the low-voltage ride-through performance of a double-fed fan by dynamically adjusting a stator series reactance value. Background technique [0002] The ever-improving energy transition requirements, the ever-changing wind power generation technology and abundant wind energy resources have made wind power generation strongly supported and developed around the world. Double-fed asynchronous wind turbines (DFIG) have become one of the mainstream wind turbine types due to the characteristics of small converter capacity and independent decoupling control of active and reactive power. [1] . However, the stator of DFIG is directly connected to the grid and is sensitive to grid-side voltage disturbances. Its low-voltage ride-through technology (LVRT) is still a hot research topic at present. Especially with the continuous i...

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Problems solved by technology

[0004] Research on software control strategies mainly includes control strategies for the purpose of de-excitation [3] , A control strategy dominated by limiting the rotor overcurrent [4] and Transient Nonlinear Controller Design [5] etc. These strategies can play a certain control effect when the voltage drops slightly. However, due to the limited capacity of the converter, it is still necessary to use hardware measures when the grid-side voltage drops deeply; although the mainstream rotor crowbar method in the hardware measures can suppress Fan rotor overcurrent, but it is difficult to effectively solve the problem of DC bus overvoltage and absorbing a large amount of reactive power from the system [6] ;Rotor side series current limiting resistor [7] Uninterrupted control of RSC can be realized, but the current injection capability of the rotor-side converter (RSC) will be reduced; other hardware ride-through methods such as series grid-side converter (SGSC) [8] , dynamic voltage restorer [9] etc. can significantly improve the ride-through performance of DFIG, but the utilization rate of these devices is low, and it is contrary to the low-cost advantage of DFIG; the stator series reactance is a kind of ride-through method with better active performance [10-11] , but it is difficult to suppress the fault overcurrent and give full play to the contradiction of RSC transient control ability at the same time, and the transient impact caused by cutting off the series reactance after the fault will also threaten the operation safety of DFIG, so it is necessary to carry out the stator series reactance method In-depth research and improvement

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