Maybe this paper could help you

Sang-Seung Lee; Yong Tae Yoon; Seung-Il Moon; Jong-Keun Park, "VSC-HVDC model-based power system optimal power flow algorithm and analysis," Power and Energy Society General Meeting (PES), 2013 IEEE , vol., no., pp.1,5, 21-25 July 2013

Some more:

Jef Beerten, Stijn Cole, and Ronnie Belmans."Generalized Steady-State VSC MTDC Model for Sequential AC/DC Power Flow Algorithms", IEEE TRANSACTIONS ON POWER SYSTEMS, VOL. 27, NO. 2, MAY 2012

Wang Feng, LeAnh Tuan, Member, Lina Bertling Tjernberg,

Anders Mannikoff, and Anders Bergman, "A New Approach for Benefit Evaluation of Multiterminal VSC–HVDC Using A Proposed Mixed AC/DC Optimal Power Flow", IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 29, NO. 1, FEBRUARY 2014

Hi

If you use DIgSILENT PowerFactory you can see the attached demo file.

Please change  HVDC Link.pdf file to HVDC Link.pfd

Maybe my  paper could help you,:

https://www.researchgate.net/publication/273036574_AC_Versus_DC_Link_Comparison_Based_on_Power_Flow_Analysis_of_a_Multimachine_Power_System

This paper presents a comparison between HVDC link and an HVAC link in a 29 Bus multimachine system, based on load flow analysis using Newton-Raphson method for the AC link case, and sequential method for the HVDC link case.

Article AC Versus DC Link Comparison Based on Power Flow Analysis of...

HI Mostafa Eidiani maybe do you have an example with HVDC-VSC for the same case one system in 50Hz and another one in 60Hz???

Regards...

For power flow you can use Portunus and/or Cerberus http://www.adapted-solutions.com/Web/index.html .

Hi,

Please, search for the following book in chapter 3.4, I hope you will find what are looking for.

Regards

https://onlinelibrary.wiley.com/doi/book/10.1002/9781118960486