Abstract
DC grids based on VSC-HVDC could be a competitive and an attractive option for many applications such as renewable energy interconnection or for power supply to large metropolitan areas for many reasons. A detailed 121st order multiple-input multiple output small-signal dynamic model of a DC grid network is presented in this paper. It contains control systems, and detailed representations of the AC and DC side. Aspects such as DC voltage droop control, the cut off frequency of the DC voltage feedback filters are discussed in detail. An eigenvalues stability study is used to find the optimum values of the droop gains and the cut off frequency of the DC voltage feedback filters. The model accuracy is verified using detailed PSCAD simulation. Testing on the detailed simulator PSCAD/EMTDC is carried out all over to validate the conclusions that obtained from analytical studies.
Highlights
High voltage direct current (HVDC) transmission based on Voltage Source Converters (VSC) has been implemented in many projects since 1996 and it is becoming accepted in power industry
This paper studies a detailed analytical model for a DC grid which should have good accuracy within frequency range for main HVDC control loop, i.e. below 100Hz
A small-signal 121st order analytical model for detailed DC network based on VSC-HVDC is presented
Summary
High voltage direct current (HVDC) transmission based on Voltage Source Converters (VSC) has been implemented in many projects since 1996 and it is becoming accepted in power industry. All installations operate as 2-terminal systems, there has been significant interest for developing multiterminal VSC HVDC. M-VSC-HVDC can be an attractive alternative to AC transmission in urban areas where underground cable transmission is preferred for safety and environmental reasons [8]. These systems can be used for urban area interconnection and power quality improvement. The current controlling terminals should have a droop DC voltage feedback [14-17]. A dynamic study is required in order to evaluate dynamic instabilities caused by droop gains and to examine possible negative interactions between terminals in a DC grid. The DC droop gains and the associated filters will be selected based on the eigenvalue analysis for the overall DC grid PSCAD /EMTDC detailed model will be used for model verification and to prove the theoretical analysis of DC droop gains
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