Event under the auspices of the Ministry of Economy of Slovak Republic

Studies on interactions in Multi-Infeed systems

*Mateusz Polewaczyk
Warsaw University of Technology, Faculty of Electrical Engin

Sylwester Robak
Warsaw University of Technology, Faculty of Electrical Engineering, Institute of Electrical Power Engineering


     Last modified: 2017-04-29

Abstract
The increasing usage of HVDC transmission system makes that converter stations of HVDC links may be situated in close electrical proximity. In this way, is created a Multi-Infeed HVDC system, in which HVDC link may interact with each other. This causes some problems associated with proper operation of HVDC links.
The main purpose of this paper is to analyze the interactions of HVDC connections in Multi-Infeed systems. The scope of this research is to analyze of voltage interactions, fault time recovery after disturbances and commutation failures during HVDC converter operation in different system variants.
First part shortly presents the current knowledge of Multi-Infeed HVDC (MIDC) systems. There is presented review of test methods and indicators used in the analysis of MIDC systems.
Second part describes test model of MIDC system, developed in different variants. In the research there are examined influence of: short circuit power level in nodes with HVDC converters, electrical distance between adjacent HVDC connections, inductance of smoothing reactor and converter station operation mode on HVDC connections performance. In the analysis of MIDC systems there are used models of Line Commutated Converters.
Results of the analysis of voltage interactions indicate that there are higher interactions between two inverter stations, in compare with one rectifier and one inverter station.
Voltage interactions appeared between HVDC links being situated in close proximity and decrease with increasing the distance between these HVDC converter stations. Moreover voltage interaction on rectifier station is lower than on inverter station. Nonetheless voltage interaction on inverter station is not affected by adjacent converter station operating mode (regardless if this is a rectifier or inverter). The lower short-circuit power in adjacent nodes with HVDC converter causes the higher voltage interaction on analysed nodes. The paper shows that commutation failure behaviour is different in Multi-Infeed systems compared to single HVDC connection.

Conclusions
Interactions between HVDC links in MIDC system are complex issue and make such connections should not be regarded as independent links. Simulation results indicate that the interactions between HVDC systems depend on a number of factors such as: short-circuit power level, electrical distance or converter station operation mode.
A notable progress in the development of power electronics devices will gradually increase the available nominal parameters, increase reliability, and expansion of existing applications. It should therefore expect a further increase number of HVDC systems.
Thus, there is a necessity to intensify research work in order to reduce the negative effects of interactions occurring in MIDC systems.

 

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