A Control Method for Suppressing Low Frequency Oscillation Propagation in the DC Side of Flexible DC Transmission System

Abstract

The invention discloses a control method for suppressing the propagation of low-frequency oscillation on the direct current side of a flexible direct current transmission system. It includes the following steps, step 1: put P ac Set as the outer loop control input signal, set P dc Set as the outer loop control input backup signal; Step 2: collect the DC voltage and DC current of the flexible DC transmission converter respectively to obtain the spectrum results; determine whether there is a low frequency oscillation component; Step 3: when the DC voltage or DC When the current contains low frequency oscillation components, set the input signal of the outer loop active power control unit to P dc ; Step 4: For P ac Perform fast Fourier analysis to obtain the spectral results; determine whether there are low-frequency oscillation components; Step 5: When P ac If it contains low-frequency oscillation components, put in the low-frequency oscillation suppression device on the AC side, and skip to step 4. The invention has the advantage of effectively suppressing the propagation of the AC low-frequency oscillation to the DC side of the flexible DC power transmission.

Description

Control method for suppressing low-frequency oscillation on DC side of HVDC flexible transmission system technical field The present invention relates to the technical field of power system power transmission and distribution, more specifically it is to suppress low-frequency oscillation in flexible DC Control method for DC side propagation of power transmission system. More specifically, it is a suppression of low frequency oscillation based on DC power feedback A control method for DC side propagation in flexible DC transmission systems. Background technique The flexible direct current transmission technology based on voltage source converter (Voltage Source Converter, VSC) is not Depends on the AC system to provide the commutation voltage, so it is possible to connect passive or weak AC systems. Among the many VSC topology types, Modular Multilevel Converter (MMC) is more suitable for high voltage and large capacity applications. It is the main application top...

AI Technical Summary

Problems solved by technology

If the low-frequency oscillation in the DC voltage or DC current is not suppressed, it will lead to low-frequency oscillation pollution of the entire DC network, affecting all converters connected to the DC network

However, the literature does not propose corresponding countermeasures

[0006] It can be seen that under the conventional vector control strategy, the flexible HVDC converter connected to the weak grid is prone to low-frequency oscillations, and the low-frequency oscillations on the AC side can be coupled through the active power between the AC and DC sides of the HVDC system. Penetrate the converter and spread to the DC side, endangering the safe and stable operation of all converter stations connected to the DC network

Images