A Method of Selecting Cable Configuration for Microgrid Using Minimum Spanning Tree

In a microgrid (MG) connecting household PV systems, we want the flow of energy in each link to be bidirectional so that energy can be shared among the households. To serve such goal, there are many possible cable configurations. Based on minimum spanning tree (MST) problem, this paper proposes a method for selecting a cost effective cable configuration provided a map of households and their maximum loads. First, the MST that connects all nodes is found using the Prim's algorithm and considering distances between all pairs of households as the weights. This guarantees the minimum distance of the cables. Then, cable size for each link in the MST is chosen based on a current constraint stating that cable rated current must be greater than maximum current flow in the cable. The maximum current flow is computed by choosing the greater value of the sum of the maximum loads in the two subtrees resulting from taking off the link from the MST. Finally, the voltage drops of all paths must be less than a specific value. By computing and ranking the voltage drops, the cable size along the path with the highest voltage drop that violates the constraint is increased until there is no violation. The cable configurations resulting from the proposed method are evaluated by comparing with the conventional cable configurations using the same cable size that covers maximum current flow. The results showed that proposed configuration can reduce cost about 48 % by average.