A method for judging and controlling dynamic stability of flexible direct current transmission

Abstract

The invention discloses a method for judging and controlling the dynamic stability of flexible direct current transmission. The judgment method includes the following steps: unlocking the converter station of the flexible direct current transmission system, allowing the flexible direct current transmission system to operate in a non-island control mode; extracting the flexible direct current The corresponding parameters of the power transmission system, the parameters include the effective value of the AC system voltage U t0 , flexible DC output reactive power Q vsc0 , the gain k of the phase-locked loop PLL p and the proportional-integral time constant k of the phase-locked loop PLL i ; Calculate the short circuit ratio SCR, and calculate U t0 , Q vsc0 The per unit value of ; calculate the key stability component; check the sign of the key stability component and determine the stability of the HVDC system. The method of the invention only needs to simply calculate the value of the key stable component, and judge the stability of the system through the sign of the value, which is simple and easy to implement, 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...

AI Technical Summary

Problems solved by technology

[0008] 2) Through the impedance modeling of the system, whether the input impedance characteristic of the system is negative is used to judge whether the system is stable. First, the overall modeling is required; : Wu Wenhua, Chen Yandong, Luo An, Zhou Leming, Zhou Xiaoping, Yang Ling, Huang Xucheng. DC Impedance Modeling, Oscillation Analysis and Suppression Methods of Island VSC-HVDC Transmission System. Proceedings of the Chinese Society for Electrical Engineering, 2018, 38(15):4359-4368+ 4636. "A Virtual Resistor Current Limit Control Method for Suppressing Continuous Commutation Failure in Traditional DC Transmission")

Images