Research On The Application Of HVDC Light Based On Voltage Source Inverter

The stable energy supply is the basis and premise of the social stability and the economic development for a national. As the traditional fossil energy reserves are depleted and the destruction for the natural environment, Energy conservation and emissions reduction, development of new energy, and to choose the road of sustainable development has become an important part of national development strategy. As a new transmission technology, VSC-HVDC,when it was proposed, quickly became the focus of attention of relevant exp erts and scholars because of its economic and technical advantages inherently. As its application in practical engineering, the requirements of its voltage and capacity are increasing continuously, but the VSC-HVDC based on traditional converter structure is limited in the two aspects of the ascension space, because of the study of the theory of the power electronic devices and manufacturing technology level at present. The modular multilevel converter(MMC) has become the research hotspot for the general scientific and technical workers, because of the significant advantage in solving the problem of voltage and capacity of the VSC-HVSC with its design flexibility and expand convenience. In this paper, VSC-HVSC has been chosen for the research object, and the topology and control strategy of the MMC is focus on research.First, in this paper, the advantages and application prospects of VSC-HVDC are analyzed from its composition and basic theory, and the research status of the technique were summarized.Secondly, the working process for the three sub module of MMC(HBSM,FBSM, CDSM) are discussed. On the basis of the discussion, the operation principle of the MMC was researched intensively, the principle of its fault clearance were analyzed.Furthermore, the mathematical model for the MMC-HVDC were constructed under two kinds of coordinate system, and its internal circulation and the capacitor voltage of the sub module were analysised in-deeply.In addition, the concept of predictive control was introduced, the application for the FCS-MPC in the control system of MMC-HVDC was researched deeply based on the discussion of the basic idea and characteristics for the finite set of control model predictive control(FSC-MPC).And the optimization function of FCS-MPC were redesigned,to avoid the difficulty of parameter design caused by the introduction of weight value when it apply into the multi-objective control system, and its validity is verified through the simulation.Finally, the advantage of the application for the MMC-HVDC in wind power grid is pointed out based on the research of the wind turbine operating characteristic and the contrast of commonly used wind power grid technology, and verified the feasibility of its application in wind power grid through the model with the strategy of constant voltage and constant frequency in Simulink.