Hierarchical Distributed Consensus for Smart Grids

Abstract

Reaching consensus in distributed systems is a topic with a long record of suggestions, discussions and approaches to solve. One instance of such a distributed system is the emerging Internet-of-Energy: Thousands of Smart Grid service providers participate in the orchestration of a multitude of intelligent energy devices and distributed energy resources (DER), to keep the balance between consumption and injection of electrical power. The traditional approach of reaching consensus with Paxos has serious drawbacks regarding scalability and dynamicality of node participation. Our work builds upon the results of Paxos and a number of its successors, such as Raft and Flexible Paxos, and takes on a more topologically driven perspective: We discuss a variant of Paxos that provides two important innovations towards applicability in future Smart Grids. First, leader election is explicitly bound to a number of nodes that are affected of the desired transaction, forming an election cluster. Election clusters (EC) are agreed upon dynamically in each round to achieve parallelizability of consensus depending on the grid topology and inter-dependability of nano- and micro-grids. Second, we describe a hierarchical extension of this scheme, where an aggregation of the achieved consensus is part of a higher level consensus scheme encompassing all nodes. This way, we achieve loose coupling combined with partial order of events, implementing a hierarchically distributed global consensus.