Analysis of Coordinated Control Strategy for Large-scale Renewable Energy VSCHVDC Integration

When a large-scale renewable energy source is connected to a VSC-HVDC grid and the VSC-HVDC system is used for long-distance transmission, the operational characteristics of the renewable energy and the VSC-HVDC grid will affect each other. The adaptability of the renewable energy to the VSC-HVDC grid will become an important factor affecting the operation of the grid. China has built the Nanao three-terminal VSC-HVDC project, the Zhoushan five-terminal VSC-HVDC project, and the two- terminal of the Xiamen VSC-HVDC project. Breakthroughs have been made in the impact of AC/DC system interconnection and key equipment technologies for VSC-HVDC transmission systems, especially VSC-HVDC converters and control protection technology. This paper focuses on the two main problems with renewable energy island integration. The first problem is how the VSC-HVDC grid provides a stable AC voltage to the renewable energy source without AC grid support. The second issue is how to maintain the energy balance of the VSC-HVDC system in the event of a fault. When the receiving end fails, the power energy cannot be sent out. When the sending end fails, the energy will accumulate in the VSC-HVDC grid. The resulting overvoltage and overcurrent problems require new control protection technology to will be introduced in this paper.