Research on the mesh network mode and distribution technology of the DC grid power transmission

It was described that the mesh network mode, insteading of the widespread end-to-end mode, would become the mainstream of the power transmission of the DC grid, due to being in line with the trendy of the technologies and needs development of the power grid. It was pointed out that the power transmission optimization strategy of the DC grid, aiming to meeting the requirements of security, economic, market and environment, and so on, had solid theoretical foundation together with potential of implementation in projects, due to being based on the high controllability of the operation, decoupling between active and reactive power control, decoupling between AC and DC grid simulation, improving technology economy of devices and engeering aspects. Based on the characteristics of the space-time distribution, the strong connectivity of the network structure, power transmission separation, and so on, aiming to realization of harmonization between accuracy and complexity of mathematical models and their solution algorithm, the proposed technological roadmap includes adopting the network flow analysis method, introducing the principle of user-optimized equilibrium (UE), transferring the constraint conditions into mathematical equations and inequalities, utilizing some reasonable assumptions conditions, establishing Beckmann transmission optimization distribution mathematical model, utilizing Frank-Wolfe algorithm to obtain the global unique optimal solution, verifying its correctness and advantages by an example. Moreover, the limitations were analyzed in the aspects of the line costs, the network structures, the line losses, the power and load changes, the capacity of the DC lines, and so on, and inconsistencies and its causes of operation performances were researched between the simulation model and the real system. Meanwhile, some further research aspects were proposed, including improving and standardizing simulation models, pursuing efficient algorithm, introducing security constraints, implementing dynamic optimization, and so on. © 2015 Chin. Soc. for Elec. Eng.