Gridlink provides a communication infrastructure for the implementation of distributed control systems in Java. It is a completely decentralized solution where the communication partners dynamically form a cluster of known instances during execution. Gridlink uses a distributed event bus based on an asynchronous communication model. A typical Gridlink system is built from a set of modules that execute a distributed application and that communicate with each other by exchanging messages. We present a smart grid use case dealing with the detection and handling of voltage band violations in low voltage networks deployed in secondary substation nodes.

The aim of this work is to study how the temporal behavior of time-triggered distributed systems is influenced by a drift of their underlying quartz. More especially, we focus on convergence-average clock synchronization used e.g. for TTP/C and FlexRay. We show that, for a fault free system in a stable environment, the global time converges to an interval spanned by the accuracies of the physical clocks independently of the system history. Although this result seems quite intuitive, it is not self-evident, given the complex behavior of distributed clock synchronization. Moreover, this proof allows to derive diagnosis information about the underlying quartz and is the enabler of remote system test.

This paper proposes the integration of internal and external clock synchronization by a combination of a fault-tolerant distributed algorithm for clock state correction with a central algorithm for clock rate correction. By means of hardware and simulation experiments it is shown that this combination improves the precision of the global time base in a distributed single cluster system while reducing the need for high-quality oscillators. Simulation results have shown that the rate-correction algorithm contributes not only in the internal clock synchronization of a single cluster system, but it can be used for external clock synchronization of a multi-cluster system with a reference clock. Therefore, deployment of the rate-correction algorithm integrates internal and external clock synchronization in one mechanism. Experimental results show that a failure in the clock rate correction does not hinder the distributed fault-tolerant clock state synchronization algorithm, since the state correction operates independently from the rate correction. The paper introduces new algorithms and presents experimental results on the achieved improvements in the precision measured in a time-triggered system. Results of simulation experiments of the new algorithms in single-cluster and multi-cluster configurations are also presented.