On Technical Advantages of VSC with Parallel Connection: From Viewpoints of Over-Current, Overload Capacity and Dynamical Var Support

During the further development and utilization of clean energy base with vast engineering restriction, the installed capacity of newly built and planned clean energy stations has increased significantly. When the collected power is sent out via the Voltage Source Converter-Based High Voltage Direct Current (VSC-HVDC) system, higher requirements are placed on the transmission capacity. However, the traditional view is that as the over-current capacity of Insulated Gate Bipolar Transistor (IGBT) device is very weak, the transmission power of VSC-HVDC is limited. Focusing on the specific scenario of longdistance transmission of clean energy through VSC-HVDC system, a research framework based on VSC with parallel connection is proposed, which can provide a new solution to this problem. Three scenarios are analyzed and discussed which provides a feasible technical path for applying parallel connection to large-capacity VSC-HVDC system. And they are traditional valve group structure, the mere parallel connection and the parallel connection with constant AC voltage control mode. The simulation in PSD Power Tools <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">®</sup> environment validates the correctness and effectiveness of the proposed method.