Carbon peaking and Carbon neutrality target has become the core energy development strategies in China. Promoting the development of emerging power systems based on renewable energy and broad acceptance of distributed energy resources (DERs) is an important way to realize the strategy. Power grid planning methods that are compatible with the development of emerging power systems shall fully consider the Carbon emissions of power generation

assurance of zero-Carbon and low-Carbon power transmission and avoid the curtailment of solar and wind energy due to transmission congestion. At the same time

the high proportion of DERS in the planning is fully explored and the collaboration of power distribution systems could facilitate the efficient accommodation of renewable energy. To this end

in this paper a collaborative grid planning model for transmission and distribution systems towards low-Carbon target is proposed. For a distribution system with a high proportion of DERs

the feasible region projection method is used to equivalently represent its feasible region as a set of constraints that can be integrated into the planning model. On the one hand

this set of equivalent constraints greatly reduces the complexity of the planning model and avoids the solving difficulties caused by considering the detailed distribution system. On the other hand

the equivalent constraints can not only effectively describe the physical limitations within the distribution system

but also accurately reflect the economic and operational characteristics of the distribution system in the power grid planning model. The case study verifies the effectiveness of equivalent constraints in describing the physical limitations within the distribution system and reflecting the economic and operational characteristics of the distribution system. In addition

the results also show that by exporting power from renewable energy

expanded transmission lines can alleviate local line congestion

help renewable energy accommodation

and reduce Carbon emissions.