Firefly algorithm based dynamic coalition formation strategy in micro-grids

With micro-grids (MGs) emerging as participants in the electricity market, cooperation between MGs has proved to improve the economic efficiency of the whole community. Coalition formation is one of the key problems in the cooperative game theory to reach the optimal decision-making under conflict and cooperation. This paper proposed a direct trading scheme based on firefly algorithm to determine the optimal coalition structure of all MGs in the micro-grid distribution network. The economic power transaction among MGs is modelled as a coalitional game considering generation cost, utility price and pricing mechanism of MG direct trading. In the coalition, MGs perform direct power transaction with other MGs rather than trade with utility so as to bring monetary benefits. Firefly algorithm (FA) is applied to calculate payoff function of each coalition groups among MGs and to allow them to maximize their utilities. The proposed algorithm is implemented dynamically at every time slot of a day and is subjected to a set of constraints comprising the surplus or demand of each MG. Simulation results show that the cooperative algorithm acquires an average 99.75% more profit than the non-cooperative method.