Doubly-fed asynchronous generator set low voltage ride through control system and control method thereof

Abstract

The invention discloses a doubly-fed asynchronous generator set low voltage ride through control system and a control method thereof. The system comprises a doubly-fed asynchronous generator, a converter, a current detection module, a Crowbar circuit control module and a Crowbar module, wherein the doubly-fed asynchronous generator is connected with the electrical network, the converter is arranged between the doubly-fed asynchronous generator and the electrical network, and the current detection module, the Crowbar circuit control module and the Crowbar module are sequentially connected and are then arranged between the converter and the doubly-fed asynchronous generator. According to the system, the current change rate is calculated by setting the Crowbar circuit control module, the current peak value and the peak value arrival time are predicted, the proper time and the optimum resistance value for access of a Crowbar circuit are acquired, the optimum access resistance value and the access time of the Crowbar circuit are guaranteed according to low voltage faults in different levels, the recovery time of the low voltage faults is effectively ameliorated, energy consumption is reduced, and low voltage ride through capability of the doubly-fed asynchronous generator set is greatly improved.

Description

technical field [0001] The invention relates to a low-voltage ride-through control system of a doubly-fed asynchronous generator set and a control method thereof. Background technique [0002] With the doubly-fed induction generator (Doubly-fed Induction Generator, DFIG) accounted for a sudden increase in the capacity of the grid year by year, when the grid fault causes the voltage drop at the grid-connected point, if all the wind turbines of the large-capacity wind farm are disconnected from the grid, it will It will adversely affect the safe operation of the power system, and even cause the power system to collapse in severe cases. Therefore, wind turbines are required to have Low Voltage Ride-through (LVRT) capabilities. [0003] The existing low voltage ride through technology is mainly realized by adding a short-circuit protection (crowbar) circuit on the rotor side. For example, the Chinese patent with the publication number CN 102005779A proposes a converter-based low...

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Problems solved by technology

[0004] However, none of the above methods considered the range of resistance connected to the crowbar circuit, and different resistance ranges will affect the recovery time of the power grid. In response to this problem, Zhang Man et al. According to the resistance of the Crowbar circuit in the article "Generator Low Voltage Ride Through", a dynamic change resistor is connected in parallel to effectively improve the robustness of the Crowbar circuit

However, this method cannot choose to connect different crowbar resistors according to the peak value of the current, and when the current threshold is exceeded, the reduced resistance is a constant value, so it cannot improve the recovery time of low voltage faults.

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