Method for improving reliability of power device of doubly-fed wind-electricity converter

Abstract

The invention discloses a method for improving reliability of a power device of a doubly-fed wind-electricity converter. The method includes increasing current flowing through the doubly-fed wind-electricity converter on the premise of keeping constant system output and no power requirement, namely increasing operating current of the doubly-fed wind-electricity converter under conditions of breeze or quite low generation power of a fan, and low current operation is avoided under conditions of breeze or quite low generation power of the fan. The method for improving reliability of the power device of the doubly-fed wind-electricity converter has the advantages that the principle is simple, control performance of the doubly-fed wind-electricity converter under the condition of breeze can be improved, operating reliability of the doubly-fed wind-electricity converter and the power device thereof is improved, the service lives of the same are prolonged and the like.

Description

technical field [0001] The invention mainly relates to the technical field of wind power, in particular to a method for improving the reliability of power devices of doubly-fed wind power converters under light wind conditions. Background technique [0002] Wind power is currently the new energy with the most mature technology, the most large-scale development conditions and the most commercial development prospects. With the continuous increase of the power of wind turbines, currently domestic wind turbines with a maximum of 6 MW have been developed and put into commercial application. The use of doubly-fed wind turbines to generate electricity is currently the mainstream way of wind power generation. Large-capacity doubly-fed wind power converter is a key component of current doubly-fed wind turbines. Its control performance determines the quality of electric energy generated by the unit, and its operational reliability will seriously affect the power generation of the un...

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Problems solved by technology

If this spike voltage exceeds the reverse bias safe operating area, there is a risk of breakdown of the IGBT element

[0007] 2. When the working current is small, there is a dead zone oscillation phenomenon, that is, in the dead zone time, affected by the distributed capacitance and the inductance of the main circuit of the converter, the IGBT terminal voltage will oscillate, and the dead zone terminal voltage oscillation may cause FWD small pulse width conduction When the tiny turn-on pulse width is small to a certain extent, the peak voltage Vsp of the IGBT element FWD may completely exceed the withstand voltage of the element during reverse recovery.

In the case of strong wind, the output current of the grid-side converter is large and smooth. However, in the case of small or light wind, there is such a problem worthy of attention: that is, when the wind is small or light, the wind power converted by the wind turbine If it is too small, the effective value of the current of the grid-side converter is very small, and the current under small currents is concentrated near the zero point and the positive and negative directions frequently change after passing through the zero point (such as figure 1 shown); according to the previous analysis and according to the current industry control method, the wind power converter basically works under the condition of small current in the case of light wind, which will greatly reduce the reliability and service life of the power device of the converter. The author calls this problem phenomenon as the small current operation phenomenon in the breeze condition

[0010] Because the personnel engaged in the development of converter technology generally lack in-depth research on the failure of converter power devices due to the frequent zero-crossing of the converter when the current is running at low currents, or ignore the impact of this problem, the current doubly-fed wind power converter In order to simplify the control, the reactive current command of the grid-side converter is generally taken as 0 no matter in the case of strong wind or light wind. The result is that in the case of light wind, the grid-side converter will In the case of small current operation, the current is often concentrated near the zero point and the positive and negative directions frequently change after passing through the zero point, which may easily cause premature failure of power devices

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