Method for improving grid-connected operation capability of doubly-fed wind turbine generator under power grid fault

Abstract

The invention discloses a method for improving a grid-connected operation capability of a doubly-fed wind turbine generator under a power grid fault. The method comprises the following steps of when agenerator terminal voltage Usm is less than or equal to 0.9 p.u. and a rotor current Irm is greater than or equal to 2.0 p.u. due to a power grid fault, inputting Crowbar and locking a rotor side converter; when the rotor current Irm is detected to be less than or equal to 1.9 p.u., quitting the Crowbar, and setting a rotor side converter control instruction value to be Psc and Qsc; calculating the generator terminal voltage and minimum grid-connected duration time td, min after control is implemented; when t is less than td and Usm is greater than 0.9 p.u. within min, setting the instructionvalue to be Psn and Qsn; otherwise, maintaining the Psc and Qsc, detecting whether a parameter is out of limit; if so, when the t is greater than td, quitting the doubly-fed wind turbine generator after the min; and if not, when the Usm is greater than 0.9 p.u., setting the instruction value to be Psn and Qsn. By using the method, a flexible power control capability and a safety margin of the doubly-fed wind turbine generator can be fully used, a continuous grid-connected operation capability of the doubly-fed wind turbine generator under the power grid fault is improved, and effective technical measures can be provided for operation control of a high-proportion wind power system.

Description

technical field [0001] The invention relates to the field of power system protection and control, in particular to a method for improving the grid-connected operation capability of a doubly-fed wind turbine under grid failure. Background technique [0002] In order to solve the global energy crisis, wind power is developing rapidly around the world. Power grids in areas rich in wind energy have gradually formed a grid pattern with a high proportion of wind power. Traditional wind turbines use cage-type induction generators or wound-type induction generators, and the stator windings of the generators are directly connected to the step-up transformer, which are called Type I and Type II wind turbines, respectively. Among them, the type II unit installs a variable resistor on the rotor winding, and realizes constant power output under gust of wind through the adjustment of the variable resistor. However, the speed of such a wind turbine is constant, and the output power canno...

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Problems solved by technology

However, because the existing methods do not fully consider the change of the control capability of the DFIG during the grid fault and the influence of the grid voltage control on the minimum duration, which greatly limits the grid-connected operation capability of the DFIG during the grid fault. It hinders the application of doubly-fed wind turbines in grid emergency control

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