Reduced-Order Small-Signal Model of Double-Terminal Flexible DC Transmission System Applying Equilibrium Theory

doi:10.12204/j.issn.1000-7229.2020.09.013

Abstract

Abstract:

In order to improve the calculation efficiency of small-signal stability analysis of DC transmission system, a small-signal reduced-order model of DC transmission system is established. Taking the two-terminal flexible DC transmission system as the research object, this paper firstly establishes the small-signal model of the two-terminal flexible DC system, and then selects the order of the system state variables according to the number of Hankel singular values on the basis of the equilibrium theory, and realizes the reduction of the small-signal model through matrix transformation. By calculating the dominant eigenvalue trajectories of the full-order system and the reduced-order system, it is verified that the reduced-order system and the full-order system have the same small-disturbance stability. The simulation results show that there is a similar dynamic response before and after the order reduction, which verifies the accuracy of the reduced-order model. In the face of complex networks, the order reduction method based on equilibrium theory can not only reduce the complexity of the model and improve the computational efficiency, but also predict the stability of the system.

Key words: small-signal model, equilibrium theory, model reduction, flexible DC transmission

CLC Number:

TM721.1

LI Shen, YAN Yunsong, LI Han, LI Xianyun, WANG Shuzheng, WANG Jianyu, CHEN Yonghua. Reduced-Order Small-Signal Model of Double-Terminal Flexible DC Transmission System Applying Equilibrium Theory[J]. ELECTRIC POWER CONSTRUCTION, 2020, 41(9): 115-123.

Figures/Tables 10

Fig.1 Two-terminal DC transmission system

Fig.2 Control block diagram of VSC

Fig.3 T-type equivalent model of DC transmission line

Table 1 Calculation of Hankel singular value

Table 2 Parameter table of two-terminal DC transmission system

Fig.4 Comparison of step response waveforms between reduced-order model and accurate model

Table 3 Calculation results of maximum absolute error and average error

Fig.5 Dominant eigenvalue trajectories of reduced-order model and full-order model

Fig.6 Active power waveform with step change of kpdo

Fig.7 DC voltage waveform under step change of kpdo

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