With the rapid development of wind power and solar power generation as well as steady development of AC and DC transmission lines

China's power system exhibits two important characteristics and trends: high proportion of renewable energy and AC/DC hybrid power grid in recent years. Based on an analysis of the present development and existing problems concerning collaborative optimization operation of AC/DC hybrid system with a high proportion of renewable energy

the key technologies demanding prompt research in four aspects are proposed

respectively. That is

situation awareness of AC/DC hybrid system under dual uncertainties of source and load

coordinated control of large renewable energy clusters considering the broadband stability constraints

flexible reconfiguration and cooperative operation with the interaction of source-grid-load in distribution systems with a high proportion of renewable energy

and multi-scale operation optimization and decision making in AC/DC hybrid system with a high proportion of renewable energy integrated. Difficulties and challenges are previewed.