Dynamic Model and Control of Voltage Source Converter Based HVDC

This paper proposes a dynamic model and control strategies of a voltage source converter (VSC) based high voltage direct current transmission system. Assuming there is no zero-sequence components exist and the AC network is balance, so there are no negative-sequence components and the voltage and current variables are all positive-sequence components expressed in the positive-sequence frame. In this paper, direct current control strategy and dual closed loop structure are proposed. Decoupled control structure consisting of current feed back and voltage feed forward is adopted in the inner current control loop which can track the reference current quickly. The outer loop controller is power regulators, which combines the inverse steady state model with PI regulator, and can control the active and reactive power separately. The simulation tests realized by PSCAD-EMTDC that VSC transmission system connect two active networks have been adopted. The simulation results verify the validity of the mathematical model and the feasibility of the proposed control strategies.