  Peer-to-peer (P2P) energy trading is a promising market scheme to accommodate
the increasing distributed energy resources (DERs). However, how P2P to be
integrated into the existing power systems remains to be investigated. In this
paper, we apply network charge as a means for the grid operator to attribute
transmission loss and ensure network constraints for empowering P2P
transaction. The interaction between the grid operator and the prosumers is
modeled as a Stackelberg game, which yields a bi-level optimization problem. We
prove that the Stackelberg game admits an equilibrium network charge price.
Besides, we propose a method to obtain the network charge price by converting
the bi-level optimization into a single-level mixed-integer quadratic
programming (MIQP), which can handle a reasonable scale of prosumers
efficiently. Simulations on the IEEE bus systems show that the proposed optimal
network charge is favorable as it can benefit both the grid operator and the
prosumers for empowering the P2P market, and achieves near-optimal social
welfare. Moreover, the results show that the presence of energy storage will
make the prosumers more sensitive to the network charge price changes.
