Double-fed power generation system, three-level converter and control method of three-level converter

Abstract

The invention provides a doubly-fed power generation system, a three-level converter and a control method of the three-level converter. After the slip frequency meets a condition is determined, i.e. the three-level converter is in a low slip condition,according to the slip frequency, detected in real time, of a rotor side in the three-level converter, the wave sending control of a rotor side module in the three-level converter is controlled to be switched from a conventional wave sending control mode to an average current wave sending control mode, so that the current when the wave sending vector is a zero vector is equalized, and the problem that a single tube bears large current for a long time to cause overheating failure is avoided.

Description

technical field [0001] The invention relates to the technical field of power electronics, in particular to a doubly-fed power generation system, a three-level converter and a control method thereof. Background technique [0002] With the rapid development of the wind power industry, the power level requirements of wind turbines are gradually increasing. If you want to maintain the AC voltage at 690V, it will inevitably lead to an increase in the number of wind turbine cables, which in turn will lead to an increase in the cost of the whole machine. Therefore, many complete machine suppliers have increased the grid-connected voltage to 1000V voltage level. Due to the constraints of module voltage stress, wind power converters mostly use three-level module solutions at this voltage level. [0003] However, although the three-level converter effectively solves the module voltage stress problem under the 1000V voltage level condition, there is another problem, which is specifical...

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Problems solved by technology

[0003] However, although the three-level converter effectively solves the module voltage stress problem under the 1000V voltage level condition, there is another problem, which is specifically manifested as: in the doubly-fed wind power generation system or doubly-fed pumped storage power generation system Among them, the rotor-side inverter of the three-level converter is the core component for exciting the motor. When it runs near the synchronous speed point, there will be a DC excitation phenomenon, that is, the three-phase current of the rotor is DC

Under this working condition, a switch tube in the three-level converter will continue to conduct. If the system runs for a long time, it will inevitably cause the switch tube to explode, which seriously affects the reliability of the product operation.

[0004] In order to solve this problem in the prior art, the number of parallel switching tube modules is increased to increase the derating factor of the switching tubes, but this leads to a substantial increase in the cost of the three-level converter

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