WSEAS Transactions on Systems
Print ISSN: 1109-2777, E-ISSN: 2224-2678
Volume 12, 2013
Research on Direct Power Control of Modular Multilevel Converter Based VSC-HVDC for Offshore Wind Farm
Authors: Xingwu Yang, Guoqiang Wang
Abstract: Control methods for novel modular multilevel converter (MMC) were studied and applied to voltage source converter based HVDC (VSC-HVDC) for offshore wind farm. The system output characteristics under different modulation methods were analyzed. Different balancing control methods of sub-module (SM) capacitor voltage were designed for n+1 and 2n+1 level output respectively, then the generation principles of 2n +1 level were described in detail. Two DC output ways for MMC which are with and without additional DC capacitors were compared. The simulation results showed that the 2n+1 MMC with additional DC capacitors had better performance and was more suitable for VSC-HVDC system. Meanwhile, the strategy of virtual flux direct power control (VF-DPC) was applied for MMC focusing on the power estimation method of this topology. The control method designed in this paper was compared with the traditional strategy of double closed loop vector control and the results showed that the control system of this paper possessed better dynamic response. Finally, MATLAB was used for testing under various conditions, the results show that the designed method is correct and effective.