Guaranteeing Input Tracking For Constrained Systems: Theory and Application to Demand Response

A method for certifying exact input trackability for constrained discrete time linear systems is introduced in this paper. A signal is assumed to be drawn from a reference set and the system must track this signal with a linear combination of its inputs. Using methods inspired from robust model predictive control, the proposed approach certifies the ability of a system to track any reference drawn from a polytopic set on a finite time horizon by solving a linear program. Optimization over a parameterization of the set of reference signals is discussed, and particular instances of parameterization of this set that result in a convex program are identified, allowing one to find the largest set of trackable signals of some class. Infinite horizon feasibility of the methods proposed is obtained through use of invariant sets, and an implicit description of such an invariant set is proposed. These results are tailored for the application of power consumption tracking for loads, where the operator of the load needs to certify in advance his ability to fulfill some requirement set by the network operator. An example of a building heating system illustrates the results.Comment: Technical Not

An Inertial Parallel and Asynchronous Forward-Backward Iteration for Distributed Convex Optimization

Two characteristics that make convex decomposition algorithms attractive are simplicity of operations and generation of parallelizable structures. In principle, these schemes require that all coordinates update at the same time, i.e., they are synchronous by construction. Introducing asynchronicity in the updates can resolve several issues that appear in the synchronous case, like load imbalances in the computations or failing communication links. However, and to the best of our knowledge, there are no instances of asynchronous versions of commonly known algorithms combined with inertial acceleration techniques. In this work, we propose an inertial asynchronous and parallel fixed-point iteration, from which several new versions of existing convex optimization algorithms emanate. Departing from the norm that the frequency of the coordinates' updates should comply to some prior distribution, we propose a scheme, where the only requirement is that the coordinates update within a bounded interval. We prove convergence of the sequence of iterates generated by the scheme at a linear rate. One instance of the proposed scheme is implemented to solve a distributed optimization load sharing problem in a smart grid setting, and its superiority with respect to the nonaccelerated version is illustrated

Learning Proximal Operators with Gaussian Processes

Several distributed-optimization setups involve a group of agents coordinated by a central entity (coordinator), altogether operating in a collaborative framework. In such environments, it is often common that the agents solve proximal minimization problems that are hidden from the central coordinator. We develop a scheme for reducing communication between the agents and the coordinator based on learning the agents' proximal operators with Gaussian Processes. The scheme learns a Gaussian Process model of the proximal operator associated with each agent from historical data collected at past query points. These models enable probabilistic predictions of the solutions to the local proximal minimization problems. Based on the predictive variance returned by a model, representative of its prediction confidence, an adaptive mechanism allows the coordinator to decide whether to communicate with the associated agent. The accuracy of the Gaussian Process models results in significant communication reduction, as demonstrated in simulations of a distributed optimal power dispatch application

Vapor-deposited hydrogenated and oxygen-deficient molybdenum oxide thin films for application in organic optoelectronics

Vapor-deposited molybdenum oxide films are used as low resistance anode interfacial layers in applications such as organic light emitting diodes (OLEDs) and organic photovoltaics (OPVs). A versatile method for the vapor deposition of molybdenum oxide layers is presented, which offers the control of the oxygen stoichiometry of the deposited films and their doping with hydrogen. The possibility of tuning the electronic structure of the deposited molybdenum oxides is also investigated by controlling oxygen deficiency and hydrogenation (the incorporation of hydrogen within the molybdenum oxide's lattice). To take advantage of the altered electronic properties of the non-stoichiometric Mo oxides, we embedded them as anode interfacial layers in organic optoelectronic devices. Large improvement in the operational characteristics of both electroluminescent devices and bulk heterojunction solar cells was achieved and correlated with the oxygen deficiency and the hydrogen content of the Mo oxides.</p