Virtual synchronous generator fault current suppression method based on adaptive virtual impedance

Abstract

The invention relates to a virtual synchronous generator fault current suppression method based on adaptive virtual impedance. When a power grid fails, the voltage of a power grid drops, a VSG can generate large fault current, particularly at the moment when a fault occurs and is removed, the VSG can generate large impact current; when the output current of the VSG exceeds the maximum value of thecurrent capable of being borne by an inverter, irreversible damage to the VSG system can be caused, and meanwhile, the stability of the power grid is further reduced. The VSG does not have a fault ride-through capability, so that the VSG can only have the fault ride-through capability through a reasonable control scheme. According to the method of the invention, VSG fault current is suppressed bythe self-adapting of virtual impedance and the modification of a VSG reference voltage during the fault, so that the VSG has the fault ride-through capability on the premise of not changing a controlstructure. The method has high control precision. With the method adopted, fault current and impact current can be effectively suppressed; and the control structure is not changed.

Description

technical field [0001] The invention relates to an inverter grid-connected control technology, in particular to a virtual synchronous generator fault current suppression method based on an adaptive virtual impedance. Background technique [0002] Grid-connected inverters are widely used as the interface between distributed power generation and the grid. Since power electronic equipment cannot provide inertia and damping for the grid like synchronous generators, with the continuous improvement of the penetration rate of distributed power generation , so that the inertia and damping of the power grid are seriously insufficient, so that the system does not have enough time to restore the frequency to a steady state when the frequency fluctuates, reducing the stability of the power grid. Virtual synchronous generator technology simulates the operating characteristics of synchronous generators, provides inertia and damping for the grid, and becomes an effective way to solve this ...

AI Technical Summary

Problems solved by technology

[0004] The invention aims at the problem that when the VSG grid-connected model suffers a large disturbance, the output current of the VSG increases and causes damage to the inverter, or the VSG is forced to leave the grid during a fault period, resulting in a large fault current, and proposes a The VSG fault current suppression method based on adaptive virtual impedance, this method can suppress the maximum value of the inverter output current and the steady-state value during the fault period when the system is subjected to a large disturbance, so as to ensure that the VSG system can be normal during the fault period and improve the transient stability margin of VSG. In addition, because the method does not change the control structure of the entire system, the difficulty of evaluating the transient stability of large power grids has not increased due to the implementation of the method.

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