Meshed HVDC grids have been gaining a strong interest for a few years now. As DC grids consist of multiple technologies from multiple vendors, the requirements for Factory Acceptance Tests will likely include real-time simulation with physical controls of each converter connected to the same grid. These tests will ensure that each facility's control, protection and communication do not degrade the performance of the DC and AC grids. But running DC grid models in real-time is a technical challenge due to the size of the system, the number of signals to be exchanged with the physical controls, and the relatively small time steps required by the VSC technology. This paper illustrates this topic by using the DC grid test system proposed by CIGRE. The test system model is described with the optimizations required to meet real-time constraints. The task separation required to solve this complex system on multiple CPUs is presented. Since it is usually quite complex to achieve efficient task separation with a reasonable number of CPUs, different task grouping algorithms are discussed. Automatic and manual task separation is applied to find the optimum solution. Finally, the real-time simulation results are validated against EMT offline simulation.
