Delay Constrained Communication Network Design for PMU to Multiple Control Center Data Transfer

In a smart grid environment, communication network plays an important role as it must deliver data from the Phasor Measurement Units (PMUs) in the Substations (SSs) to the Control Center(s) (CCs) in real time. Accordingly, communication network design has received considerable attention from smart grid researchers in the last few years. In a recent paper, we studied this problem where all the substations were sending data to a single CC and formalized it as the Rooted Delay Constrained Minimum Spanning Tree problem. As the number of substations in a geographic area is often large, PMU data from the substations do not directly go to the Control Center (CC) and instead goes to multiple Local Controls Centers (LCC) within a specified delay threshold. The aggregated data from the LCCs is then sent to the CC. In this paper, we extend our earlier results by considering Multiple Local Control Centers (MLCCs) where the PMU data must arrive from the SSs to a LCC within a specified delay threshold. This gives rise to a new problem, where we need to create a Delay Constrained Spanning Forest instead of a Delay Constrained Spanning Tree as in earlier studies. We provide (i) an optimal solution for the problem using Integer Linear Programming, (ii) a Lagrangian Relaxation, and (iii) a Heuristic solution. Finally, we evaluate the performance of our solution techniques with real substation location data of Arizona.