A method and system for controlling power angle and current and voltage of virtual synchronous machine under fault

Abstract

The invention discloses a method and system for controlling power angle and current and voltage of a virtual synchronous machine under fault conditions, and belongs to the technical field of new energy grid-connected system control. In the event of a fault, this method first obtains fault information immediately through traveling wave ranging, and then synchronously adjusts the active power outer loop and reactive power outer loop control parameters of the virtual synchronous machine to achieve precise control of its transient power angle and improve Transient stability after a virtual synchronous machine fault, while meeting the current limit of the converter or the terminal voltage requirements of the machine. In order to adapt to the change of the operating state of the system after a fault, the present invention designs a control strategy in two stages according to the fact that the system is in a fault or after a fault tangent. In addition, a closed-loop feedback link is designed to improve the robustness of the control strategy. The invention realizes the transient power angle stability of the virtual synchronous machine under failure, ensures current limitation and voltage support at the same time, and improves the transient performance of the virtual synchronous machine under failure.

Description

technical field [0001] The invention belongs to the technical field of new energy grid-connected system control, and more specifically relates to a method and system for controlling the power angle and current and voltage of a virtual synchronous machine under fault conditions. Background technique [0002] With the increasing application of renewable energy, more and more flexible and controllable Voltage Source Converters (Voltage Source Converters, VSCs) are connected to the grid. In order to solve the problem of reduced inertia and damping caused by the grid connection of VSCs, virtual synchronous generators (Virtual Synchronous Generators, VSGs), which can simulate the output characteristics of traditional synchronous generators (Synchronous Generators, SGs), have gradually been widely used. While VSG benefits from the operation mode similar to SG, it also faces the problem of transient stability after large disturbances such as grid voltage drop, transmission line faul...

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Problems solved by technology

[0003] Usually, the control strategy for transient power angle stability of VSG includes adjusting the active power and reactive power reference value, or adjusting the virtual inertia and damping parameters, but the above methods cannot quantitatively design the specific adjustment amount, and the operating conditions of the system change Poor adaptability, and unable to meet the current limit and voltage support of VSG after a fault

On the other hand, the current limiting control strategy for VSG includes saturated module current limiting and virtual impedance current limiting, but both of them will in turn affect the transient power angle stability of VSG

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