High Voltage Direct Current systems based on Voltage Source Converters (VSC-HVDC) are increasingly being considered as a viable technology with advantages, above all when using underground or submarine cables, for bulk power transmission. In order to fully understand how VSC-HVDC systems can be best used within existing power systems, it is necessary to adapt conventional tools to carry out system-wide studies including this technology. Along this line, this paper proposes a simplified algorithm to solve optimal power flows (OPFs) in hybrid VSC-based Alternating Current/Direct Current (AC/DC) grids with multi-terminal VSC-HVDC systems. The proposed algorithm makes it possible to seamlessly extend a previous large-scale AC case to which several multi-terminal VSC-HVDC systems must be added. The proposed approach combines two ideas used previously in two different modelling approaches: each VSC is modelled as two generators with a coupling constraint; and DC grids are modelled as notional AC grids, since, in per unit, the equations for the former are a particular case of the latter with resistive lines and no reactive-power injections. In the proposed approach, the hybrid VSC-based AC/DC system is transformed into an equivalent only-AC system. Therefore, the OPF solution of the AC/DC system can be found with the same tool used for the previous AC problem and a simple extension of the original case.
Keywords: VSC HVDC; HVDC transmission; Multi-terminal; Optimal power flow; Power systems
International Journal of Electrical Power & Energy Systems. Volume: 110 Pages: 781-794
JCR Impact Factor and Scopus quartile: 3.610 - Q1 (2017)
DOI reference: 10.1016/j.ijepes.2019.03.044
Published on paper: September 2019. Published on-line: April 2019.
J. Renedo, A.A. Ibrahim, B. Kazemtabrizi, A. García-Cerrada, L. Rouco, Q. Zhao, J. García-González. A simplified algorithm to solve optimal power flows in hybrid VSC-based AC/DC systems. International Journal of Electrical Power & Energy Systems. vol. 110, pp. 781-794, September 2019. [Online: April 2019]