Control of a multi-terminal HVDC system for the exchange of primary reserve power across AC grids

为了将北部和波罗的海计划或在建的海上风力发电场的电力远距离输送到德国南部和西部的城市地区，目前正在讨论在现有交流电网的基础上实现高压直流(HVDC)电网。与此同时，还在讨论在北海建设高压直流输电网络，以便将邻国彼此连接起来，并连接风力发电场。本研究项目致力于开发一种高压直流换流站的控制结构，将多个偏远地区的直流电网与一个或多个交流电网连接起来。这种控制结构一方面应该能够分散地控制直流电压，因此也可以实现大的直流电网。另一方面，根据交流电网的已知控制过程，应提供特殊的直流潮流处理手段。除了海上发电的纯分布外，这种直流电网还允许灵活的输电服务。这尤其适用于不同交流电网之间的备用电力交换和储能发电厂的使用。控制器应能根据实际需要自动管理该备用电源的转移。

For the transmission of electricity from offshore wind farms that are planned or in construction in North- and Baltic Sea over large distances to the urban areas in south- and west-Germany, the realization of a high-voltage-direct-current (HVDC) grid in addition to the existing AC-grid is currently in discussion. At the same time the construction of an HVDC grid in the North Sea for the connection of the neighbouring countries to each other and to the wind farms is also in discussion. This research project focuses on the development of a control structure for the HVDC converters, which connect the dc grid at multiple, remote locations with one or several AC-grids. The control structure shall on the one hand be able to control the DC-voltage decentrally, so that also large DC-grids are feasible. On the other hand, according to the known control processes in AC-grids, special means to handle the dc power flow shall be provided.Besides the pure distribution of the offshore generated power, such a dc grid also allows flexible power transmission services. This especially goes for the exchange of reserve power between the different AC-grids and the usage of storage power plants. The control shall be able to manage this reserve power transfer automatically and according to the actual demand.