Study of Coordination Control for VSC-MTDC Under New Developing Trend

With the developing of voltage source converter based multi-terminal dc transmission (VSC-MTDC) technology, DC grid of meshed topology is the trend of VSC-MTDC; moreover, it will be widely used for large scale renewable energy integration. For DC grid of meshed topology, the control aspect is of great importance, while the randomness and volatility of renewable energy will affect the stability of DC grid. The control stability of the VSC-MTDC, especially the control of DC voltage, will face new challenges. This paper focus on the developing trend of VSC-MTDC, the control requirements of DC grid of meshed topology and the effects of large scale renewable energy to the VSC-MTDC are analysed. And mainstream coordinating control strategies under the new situation are compared through the way of theoretical analysis. Simulations based on PSCAD/EMTDC are carried out in a five-terminal meshed VSC-MTDC system with an isolated wind farm, a passive network and three ac synchronized power grids, proving the accuracy of theoretical analysis. Then control characteristics and applicability of the coordinating control strategies for meshed VSC-MTDC with large scale renewable energy integration are concluded.