Method and system for controlling power angle, current and voltage of virtual synchronous machine under fault

Abstract

The invention discloses a method and system for controlling the power angle, current and voltage of a virtual synchronous machine under a fault, and belongs to the technical field of new energy grid-connected system control. According to the method, fault information is obtained in real time through traveling wave distance measurement under the fault condition, then active power outer loop and reactive power outer loop control parameters of the virtual synchronous machine are synchronously adjusted, accurate control over the transient power angle of the virtual synchronous machine is achieved, the transient stability of the virtual synchronous machine after the fault is improved, and meanwhile, the current limitation or terminal voltage requirements of a converter are met. In order to adapt to the running state change of the system after the fault, a control strategy is designed in two stages according to the condition that the system is in the fault or after fault line removal. In addition, a closed-loop feedback link is designed to improve the robustness of the control strategy. According to the method and system, the transient power angle stability of the virtual synchronous machine under the fault is realized, meanwhile, the current limitation and the voltage support are ensured, and the transient performance of the virtual synchronous machine under the fault is improved.

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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