Flexible DC transmission dynamic stability determining and controlling method

Abstract

The invention discloses a flexible DC transmission dynamic stability determining and controlling method which comprises the steps of: unlocking a converter station of a flexible DC transmission system, and allowing the flexible DC transmission system to operate in a non-island control mode; extracting corresponding parameters of the flexible DC transmission system, wherein the parameters include an AC system voltage effective value Ut0, a flexible DC external reactive power Qvsc0, a gain kp of a phase locked loop PLL, and a proportional integral time constant ki of the phase locked loop PLL; calculating a short-circuit ratio SCR, the per-unit value of Ut0 and Qvsc0; calculating a key stable component; and checking the sign of the key stable component and determining the stability of the flexible DC transmission system. The method of the invention only needs to simply calculate the value of the key stable component, determines the stability of the system by the sign of the value, is simple and easy, and is beneficial to engineering practice.

Description

technical field [0001] The invention relates to the technical field of flexible direct current transmission system control, in particular to a method for judging and controlling the dynamic stability of flexible direct current transmission. Background technique [0002] Compared with traditional LCC-HVDC, flexible direct current transmission VSC-HVDC can provide reactive power support for AC system without commutation failure, so it has wider application prospects in weak connection scenarios. In particular, in the island control mode (constant AC voltage, constant AC frequency), it can realize new functions that conventional transmission methods do not have, such as flexible grid connection of new energy, power transmission to passive systems, and auxiliary grid black start. [0003] When the VSC-HVDC is connected in parallel with the AC system, the system frequency is determined by the AC main network. At this time, the VSC must adopt the non-islanding control mode, but it...

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