Virtual impedance access method and device based on short-circuit ratio and electronic equipment

Abstract

The invention provides a virtual impedance access method and device based on a short-circuit ratio and electronic equipment. A doubly-fed unit output impedance model comprises a rotor side impedance relation model, a short-circuit ratio and stator side drop voltage relation model and a short-circuit ratio and line impedance relation model under the condition of a weak power grid. Whether there is short-circuit fault misjudgment caused by voltage fluctuation variation or not is judged according to a preset condition; if it is judged that there is a short-circuit fault, the fault short-circuit current is calculated according to the rotor side impedance relation model, the short-circuit ratio and stator side drop voltage relation model and the short-circuit ratio and line impedance relation model; and a target virtual impedance access value is determined according to the fault short-circuit current and a preset maximum allowable current. Under the condition of a weak power grid, the optimal virtual impedance access value of a doubly-fed unit in the case of a power grid fault can be calculated in a short-circuit ratio optimal impedance calculation mode, so that the doubly-fed unit achieves the optimal fault ride-through capability.

Description

technical field [0001] The invention relates to the technical field of new energy power generation, in particular to a virtual impedance access method, device and electronic equipment based on short-circuit ratio. Background technique [0002] With the continuous development of new energy sources, the installed capacity of new energy generators such as wind power photovoltaics is gradually increasing, and the scale of wind power access is increasing. The high penetration rate of wind power will lead to a decrease in the strength of the power grid. When wind power is connected to a weak grid, the grid line impedance cannot be ignored. The current wind turbines are mainly double-fed units, that is, the stator side is directly connected to the grid, and the rotor side is connected to the grid through a converter. When a short-circuit fault occurs in the power grid, under a strong power grid, the voltage at the stator terminal of the doubly-fed unit drops the same as the grid v...

AI Technical Summary

Problems solved by technology

Because the rotor side of the doubly-fed generator will be connected to the grid through the converter, at present, certain control measures are usually taken on the rotor side to control the generator set, and when a short-circuit fault occurs, an overcurrent will appear on the rotor side, causing damage to the converter. In the face of low-voltage faults, the traditional vector control strategy of doubly-fed units cannot complete the fault ride-through and suppress the fault short-circuit current well. In view of this situation, the existing research has proposed many improvement measures to strengthen the fault ride-through capability. There are two ways to directly add additional hardware equipment and optimize the control strategy of the doubly-fed unit itself to improve the fault ride-through performance of the system

[0003] At present, in the method of directly adding additional hardware equipment, the method of connecting a crowbar circuit or connecting an actual resistor in series on the rotor side is often used to reduce the fault short-circuit current and enhance the fault ride-through capability ; In terms of optimizing the control strategy of the double-fed unit itself, the voltage-type virtual synchronous optimal control strategy is used to replace the traditional vector control strategy, but these improvement measures are less concerned about the non-negligible line impedance in the case of a weak grid. Influence of the magnitude of the fault short-circuit current

In weak power grids with small short-circuit ratio, the existence of line impedance affects the feasibility of improvement measures. At present, virtual synchronization measures are often used instead of traditional vector measures to obtain better control under weak power grid conditions, but commonly used virtual synchronization control measures Because it does not have the ability of fault ride-through, the overcurrent on the rotor side will damage the converter when a short-circuit fault occurs, and it is necessary to consider adding a virtual impedance

In the existing technology, the influence of factors such as line impedance and voltage flicker in the weak power grid is not considered. Improper selection of virtual impedance resistance or misjudgment of faults may occur. Excessive resistance of virtual impedance or wrong connection will reduce the The dynamic performance of the control system makes the control response slow down, and too small impedance will lead to the inability to completely suppress the overcurrent, etc.

It can be seen that in the prior art, there is a problem that the calculation accuracy of the virtual impedance access value is low and the voltage fluctuation in the case of a weak power grid is not considered.

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