Symmetric Fault Transient Control Method Considering Saturation Characteristics of Virtual Synchronous Machine

Abstract

The invention discloses a symmetric fault transient stability analysis and control method in consideration of saturation characteristic of a virtual synchronous machine. Currently, a researching method which is related with transient stability of a virtual synchronous machine on the condition of large interference is not suitable for the symmetric shortcircuit fault of a power grid. According to the method of the invention, through establishing a system equivalent model before the symmetric fault of the power grid, in the symmetric fault of the power grid and after the symmetric fault of the power grid, through analyzing a transient stability mechanism and an instability process on the condition that the saturation characteristic of the virtual synchronous machine is considered, a fact that a main influence factor for transient stability of the system is power angle magnitude is obtained. Based on the fact, a corresponding measure is presented, thereby effectively suppressing transientenergy and improving transient stability of the system.

Description

technical field [0001] The invention relates to the technical fields of distributed power generation and power electronics, in particular to a symmetrical fault transient control method considering the saturation characteristics of a virtual synchronous machine. Background technique [0002] Most of the electricity in the traditional grid is provided by large synchronous generators. Since the rotor of the synchronous generator has a mechanical moment of inertia, it can contain a large amount of kinetic energy. When the grid is disturbed or faulty, the kinetic energy of the rotor can be used to exchange energy with the grid to Maintain grid stability. However, in recent years, with the development of new energy power generation technology, distributed power sources with inverters as the main interface have been more and more widely used. Compared with synchronous generators in traditional power systems, inverters have almost no With the moment of inertia, it is difficult to ...

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Problems solved by technology

[0009] 2) The large interference mainly comes from the drop of the external voltage amplitude, and this analysis method is not applicable when a symmetrical short-circuit fault occurs on the line;

[0010] 3) Neglecting the voltage reduction caused by the reactive power-voltage droop regulation of the virtual synchronous machine, it is considered that the output voltage of the virtual synchronous machine V o remains unchanged, but in fact due to the existence of the limiting link, the voltage drop during the fault process is large and cannot be ignored, and after the fault is removed, the virtual synchronous machine output voltage V o The recovery process of the system will also affect the transient energy of the system and its stability

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