Abstract

Small-signal stability analysis of the voltage source converter (VSC) based multi-terminal DC (MTDC) grids has been mainly focused on the dynamics of AC/DC converters while there is a lack of consideration of DC networks with DC power-flow controllers. In this paper, an integrated small-signal model is established to investigate the interactions between VSC and DC current flow controllers (CFC). The impacts of the control system of CFC on small-signal stability of the integrated system and the impacts of the control system of VSC on the DC networks with CFC are discussed via eigenvalue analysis. The above interactions are demonstrated through dynamic simulations against both small and large disturbances using real time digital simulator (RTDS).

Highlights

  • V OLTAGE source converter (VSC) based multi-terminal DC (MTDC) system is the preferred solution for grid connection of large-scale offshore wind farms [1], [2], as it is the feasible option for long distance submarine interconnection of passive and weak systems [3], [4]

  • The published papers on small-signal stability of VSC MTDC systems have mainly been focused on the dynamics of VSCs while there is a lack of considerations of DC networks with current flow controllers (CFC)

  • Modal analysis results have been verified by the dynamic simulations in real time digital simulator (RTDS) under both small and large AC/DC disturbances and DC system grounding fault applied in III.B.3)), which illustrates the incorporation of CFC has been shown to affect dynamic stability of the existing MTDC/AC system especially the adjacent VSC converters

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Summary

INTRODUCTION

V OLTAGE source converter (VSC) based multi-terminal DC (MTDC) system is the preferred solution for grid connection of large-scale offshore wind farms [1], [2], as it is the feasible option for long distance submarine interconnection of passive and weak systems [3], [4]. In [8] the small-signal stability analysis has been carried out for a symmetric bipolar MTDC grid where different modes and interactions between AC systems and VSC following various disturbances were characterized. The published papers on small-signal stability of VSC MTDC systems have mainly been focused on the dynamics of VSCs while there is a lack of considerations of DC networks with CFC. There is a lack of analysis on the potential impacts of DC power-flow controller on existing MTDC system in terms of network stability and dynamic performance under disturbances. SMALL-SIGNAL STABILITY MODEL OF THE INTEGRATED AC/DC SYSTEMS WITHOUT/WITH CFC Fig. 1 shows the generic topology of a generalized AC/DC system, which consists of CFC-integrated DC networks, VSC and AC networks. First-order IEEE type 2 exciter and third-order power system stabilizer controllers are used with synchronous generators

VSC MODEL
AC NETWORK
TEST SYSTEM
IMPACTS OF CONTROL PARAMETERS OF VSC ON CFC
Findings
CONCLUSION
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