Dual-Mode Control of AC/VSC-HVDC Hybrid Transmission Systems With Wind Power Integrated

This paper proposes a novel dual-mode control scheme for the control of an ac/voltage-source converter (VSC)-HVDC hybrid transmission system with the wind farm connected. First, a novel ac voltage and phase-angle control scheme is designed for the active power control of the wind farm side voltage-source converter (WFVSC) such that the switching of control schemes of WFVSC is no longer required when the ac lines are switched on or off the transmission system. This results in the proposed dual-mode control scheme being able to accommodate different operation modes of the ac/dc hybrid transmission systems. Second, an improved direct-current vector control scheme has been designed for the control of grid-side VSC (GVSC) to provide better control of the dc voltage of the GVSC. Moreover, simulation studies have been undertaken on a two-terminal VSC-HVDC and an ac hybrid transmission system under a variety of operating conditions, which have validated the feasibility performance of the proposed control scheme.