This chapter presents a cyber-physical approach to design of HVDC control system architectures and evolving HVDC grid operation and control modes. In addition, the chapter describes the communication system architectures needed for centralized and distributed operation and control of HVDC grids. Modeling and analysis methods suitable to analyze such systems using graph theoretic concepts, and also the design of distributed control systems utilizing a Multi-Agent approach and its dependence on the information graph theory. The chapter is concluded with a description of an application for distributed control of DC grids utilizing the concepts introduced. The application is presented both with regards to comparison with other design choices and analysis of performance and robustness of the algorithm versus communication metrics.