A control strategy for VSC-HVDC system based on analytic expression

In VSC-HVDC transmission system, good control strategy depends on precise mathematic model. However, there is no such direct analytic expression model presented up to now. A control strategy based on analytic expression for VSC-HVDC is presented in this paper, which is connected with active ac power system in both sides, based on the steady model of VSC. The analytic expression about the two controlling variables and the two controlled variables is deduced from VSC power transmission equations according to the basic steady models of the constant dc voltage side and the constant dc current side. A controller is designed, which adopts the main analytic expression model assisted by the closed loop feedback control model. Simulation results testify the feasibility of the control strategy and show that the controller has such advantages as simple structure, quickly responding speed, precise control, etc