An investment game model for offshore power grid multi-stage expansion planning

The offshore power grid (OPG) which connects multiple neighboring coastal countries is an effective solution to collect and deliver electricity generated by offshore wind farms (OWFs). The transmission network investment decision of the OPG expansion tends to be decentralized where individual stakeholder's strategies are interactive. This paper proposes a two-stage game model to tackle the conflict between the minimum expenditure and the maximum profit of each investor. In the first stage, a cooperative game model is formulated where the players are the OWF investors and the strategies are the connection typologies. The cost of the High Voltage Alternating Current (HVAC) transmission system and the offshore hubs is to be minimized and allocated to each player according to the Shapley value method. In the second stage, a non-cooperative game model is proposed where the players are the coastal countries, represented by onshore nodes and the strategies are the topology of the High Voltage Direct Current (HVDC) transmission system connecting the onshore nodes and the OWFs/offshore nodes. The net present value (NPV) ratio of each player is to be maximized and the Nash equilibrium (NE) is found in different modes. The case study on an OPG with three onshore nodes and two OWFs verifies the effectiveness of the proposed model.