A virtual capacitor control method for doubly-fed wind power grid-connected system

Abstract

The invention discloses a virtual capacitance control method of a double-fed wind power generation grid-connected system. The method is characterized by using the double-fed wind power generation grid-connected system to adopt a motor routine; acquiring a three-phase voltage signal VPCC of a grid-connected point during a fault period; and calculating an input voltage V'PCC of a phase-locked loop of the double-fed wind power generation grid-connected system according to the following formula, wherein the obtained voltage V'PCC is input into the phase-locked loop of the double-fed wind power generation grid-connected system when a symmetric short-circuit fault occurs in a power grid, and a stator side output impedance and a grid side inverter output impedance of the double-fed wind power generation grid-connected system meet set requirements. Therefore, an input voltage of a phase-locked loop module of the double-fed wind power generation grid-connected system can be controlled to improve dynamic stability of the system during a fault period. According to the method, controller interaction of the double-fed wind power generation grid-connected system caused by a high line impedanceduring the symmetric short-circuit fault of the power grid can be weakened, an electrical distance between a wind power system and a fault point is equivalently reduced, and a small signal stability margin of the system is improved.

Description

technical field [0001] The invention relates to an improved virtual capacitance control method of a doubly-fed wind power generation grid-connected system, which is applicable to a doubly-fed wind power generation grid-connected system under a symmetrical short-circuit fault of an AC power grid. The dynamic stability of the grid-connected power generation system solves the problem of small disturbance instability of the doubly-fed wind power grid-connected system during grid faults. Background technique [0002] As the penetration rate of new energy power generation in the power system continues to increase, the power grid presents the characteristics of a weak synchronous power grid. The phase-locked loop and the rotor current loop are strengthened by the interaction of high grid line impedance, especially during the short-circuit fault of the grid, the DFIG grid-connected system may be dynamically unstable during the short-circuit fault, which seriously affects the DFIG an...

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Problems solved by technology

However, this literature does not deal with the oscillation problem caused by the interaction of controllers through high line impedance. The impedance reshaping control strategy proposed in this literature has limitations in solving the oscillation problem caused by controller interaction.

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