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Optimal control method for system stability based on grid-friendly dfig control strategy

A system stability and control strategy technology, applied in the direction of single-network parallel feeding arrangement, etc., can solve the mutual constraints of grid-friendly DFIG control strategies, the influence of different voltage drop ranges on power angle stability, and the effect of improving the voltage drop level, etc. problems, to achieve the effect of reducing the risk of off-grid, improving the stability of power angle, and reducing the depth of voltage drop

Active Publication Date: 2021-11-23
CHINA THREE GORGES UNIV
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Problems solved by technology

Although the design starting points of the above three types of grid-friendly DFIG control strategies are different, because the time scale of the speed (active power) control and reactive power control in the DFIG control system coincides with the electromechanical time scale of the system, when a short-circuit fault occurs in the system, the DFIG temporarily The state active / reactive power control will respond to the change of the DFIG machine terminal voltage, while the virtual inertia control will respond to the instantaneous deviation of the system frequency, and rapidly change the transient active and reactive power output characteristics of the DFIG, thereby stabilizing the power angle of the system And the voltage drop has different effects
[0003] Although the impact of the above three types of grid-friendly DFIG control strategies on system stability has been fully studied, the research usually only focuses on the impact of a single control strategy on system stability, and less consideration is given to the interaction between control strategies. Therefore, it is possible to make the grid-friendly DFIG control strategies restrict each other in practical applications and affect their respective control effects
For example, the influence of transient active and reactive power control on the effect of virtual inertia control. Although virtual inertia control has the ability to improve the stability of system power angle, this advantage will be limited by transient active and reactive power control under certain conditions.
Another example is the influence of virtual inertia control on the effect of transient reactive power control, which will affect the improvement effect of DFIG on the voltage drop level in faults under certain conditions

Method used

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  • Optimal control method for system stability based on grid-friendly dfig control strategy

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Embodiment

[0084] The two-area four-machine system is adopted, as shown in Figure 5(a), and the parameters are as follows:

[0085] 1. Network parameters:

[0086] In order to simulate a typical wind power transmission system in the Three North Regions of my country where the inertia of the synchronous motor at the receiving end is much greater than the inertia of the synchronous motor at the sending end, the G3 inertia of the synchronous motor is set to 50 times the G1 inertia, and other parameters are the same as the original system. G1 is set as a PV node, and G3 is a balance node. The synchronous motors G2 and G4 and their step-up transformers in the original two-area system are removed. Line parameters and bus voltage levels are the same as those of the original system.

[0087] The parameters of the step-up transformer T1 are consistent with the parameters of the step-up transformer Trf 0.69 / 20kV in the DFIG_2.5MW model in the DIgSIENT / PowerFactory Templates module, and the posit...

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Abstract

Based on the grid-friendly DFIG control strategy, the system stability optimization control method includes determining the optimal control model for the interaction effect of the traditional grid-friendly DFIG control strategy; using the cross-transient active power control model to analyze the change of DFIG active output during the system short-circuit fault ; Use the reactive power correction current control model with additional constraints to analyze the change of DFIG reactive power output during the system short-circuit fault; comprehensively evaluate the effect of system stability improvement after optimal control. The method of the present invention considers the mutual influence of control strategies, and analyzes various factors such as the influence of active power limiting and restoration on the virtual inertia control effect, the influence of virtual inertia control on the transient reactive power control effect, etc., and adopts the cross-transient active power control The strategy and the reactive power correction current control strategy with additional constraints analyze the DFIG output changes during the system short-circuit fault, and finally make a comprehensive evaluation of the system stability improvement effect after the optimal control.

Description

technical field [0001] The invention relates to the field of power grid optimization control, in particular to a system stability optimization control method based on a power grid-friendly DFIG control strategy. Background technique [0002] Under the idea of ​​wind farm grid friendliness, in the DFIG general model, the active power setting can be limited during the short circuit period and the active power recovery period after the short circuit, so as to reduce the load pressure of the converter and reduce the transient state of the impact of too fast recovery of active power Active power control; and transient reactive power control that can improve reactive power injection during short circuit and reduce the risk of DFIG off-grid. In addition, in order to ensure the frequency stability of the system when a large active power deficit (or surplus) occurs in the system, virtual inertia control has also become a research hotspot in recent years. Although the design starting...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02J3/48H02J3/50
CPCH02J3/48H02J3/50
Inventor 张磊许忠义叶婧胡汉梅张闯吴罗兰陈俊慧余朋军徐加宝朱泽伟
Owner CHINA THREE GORGES UNIV
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