A method for improving grid-connected operation capability of doubly-fed wind turbines under grid failure

Abstract

The invention discloses a method for improving the grid-connected operation capability of doubly-fed wind turbines under grid failure. When the grid failure makes the machine terminal voltage U sm ≤0.9p.u. and rotor current I rm ≥2.0p.u., put into Crowbar and block the rotor side converter; when the rotor current I is detected rm Exit Crowbar when ≤1.9p.u., set the control command value of the rotor-side converter to P sc , Q sc ; Calculate the machine terminal voltage and the minimum grid-connected duration t after the control is implemented d,min ; at t < t d,min Inner U sm When >0.9p.u., set the command value as P sn , Q sn ; otherwise, always keep P sc , Q sc , and detect whether the parameter exceeds the limit, if it exceeds the limit, when t>t d,min After that, the doubly-fed wind turbine will exit. If the limit is not exceeded, when U sm >0.9p.u., set the command value to P sn , Q sn . This method can give full play to the flexible power control capability and safety margin of the doubly-fed wind turbine, improve the continuous grid-connected operation capability of the doubly-fed wind turbine under grid failure, and provide effective technical measures for the operation control of a high-ratio 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...

AI Technical Summary

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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