Resilient Distributed MPC Algorithm for Microgrid Energy Management under Uncertainties

This paper proposes a resilient distributed energy management algorithm able to cope with different types of faults in a DC microgrid system. A distributed optimization method allows to solve the energy management problem without sharing any private data with the network and reducing the computational cost for each agent, with respect to the centralised case. A distributed MPC scheme based on distributed optimization is used to cope with uncertainty that characterizes the microgrid operation. In order to be resilient to faults that limit the amount of power available to consumers, we propose to adaptively store an amount of power in the storage systems to support the loads. A soft constraint on the minimum energy stored in each battery is introduced for feasibility and to cope with persistent faults. The effectiveness of the method is proved by extensive simulation results considering faults on three types of components: renewable generator, distribution grid and communication network

Nonlinear simulation of masonry vaults under earthquake loading

Masonry vaults are present in a large number of historical structures and often used as floor-ing and roofing systems in monumental palaces and religious buildings, typically incorporat-ing no backfill. Many of these structures are located in seismic regions and have been shownto be particularly vulnerable during recent earthquakes, with a need for accurate modelling to avoid future losses. Masonry vaults are often analysed using limit analysis procedures un-der the hypotheses of no-tension material and absence of sliding along the masonry joints.However, this method can be inaccurate for barrel vaults found in buildings, which are typi-cally slender with no backfill. In this case, the masonry tensile strength and the progressive damage propagation play an important role in the nonlinear behaviour and ultimate strength of the vault. In this study, a detailed mesoscale finite element mesoscale approach is used to model slender unreinforced barrel vaults subjected to cyclic quasi-static and dynamic load-ing. According to this approach, 3D solid elements connected by 2D damage-plasticity inter-faces are used to represent the arrangement of bricks and mortar present in the masonry. Theproposed numerical description is first validated against the results from physical tests on a barrel vault under quasi-static cyclic loading. Subsequently, the shear response of a prototype vault is analysed by performing nonlinear simulations under prescribed horizontal displace-ments at the supports, considering also the influence of previous damage induced by earth-quakes with different magnitudes

Fault diagnosis for uncertain networked systems

Fault diagnosis has been at the forefront of technological developments for several decades. Recent advances in many engineering fields have led to the networked interconnection of various systems. The increased complexity of modern systems leads to a larger number of sources of uncertainty which must be taken into consideration and addressed properly in the design of monitoring and fault diagnosis architectures. This chapter reviews a model-based distributed fault diagnosis approach for uncertain nonlinear large-scale networked systems to specifically address: (a) the presence of measurement noise by devising a filtering scheme for dampening the effect of noise; (b) the modeling of uncertainty by developing an adaptive learning scheme; (c) the uncertainty issues emerging when considering networked systems such as the presence of delays and packet dropouts in the communication networks. The proposed architecture considers in an integrated way the various components of complex distributed systems such as the physical environment, the sensor level, the fault diagnosers, and the communication networks. Finally, some actions taken after the detection of a fault, such as the identification of the fault location and its magnitude or the learning of the fault function, are illustrated

Influence of mortar coating type on the shear resistance of a GFRP based strengthening technique for brick masonry walls

A strengthening technique for increasing both the in-plane and out-of-plane resistance of masonry walls based on the application on both sides of the wall of a mortar coating reinforced with glass fiberreinforced polymer (GFRP) meshes is herein considered. A recent experimental campaign evidenced the effectiveness of this technique both in terms of resistance and deformation capacity of masonry walls. The paper focuses on the in-plane behavior of reinforced masonry, collecting the results of diagonal compression tests performed on solid brick masonry specimens enhanced by considering 17 different types of mortar for the coating (tensile resistances ranging from 0.7 to 3 MPa, Young modulus from 6000 to 23000 MPa). These experimental results are useful to extend the validity of an analytical formulation proposed by the authors and to investigate on the behavior of the reinforced masonry when the coating mechanical characteristics vary considerably. It emerged that the effectiveness of the reinforcement decreases with the increase of the mortar resistance and that the assessment of the reinforced masonry resistance as sum of the resistances of the masonry and that of the reinforced coating in not always on the safe side but has to be corrected through a coefficient. Based on the experimental results, a characteristic curve at 5% fractile was provided for this coefficient in function of the tensile strength of the mortar; the curve is represented by a decreasing exponential function with an asymptotic value at 0.8

Strengthening of masonry vaults through a thin extradoxal layer of fiber reinforced lime mortar

A technique to strengthen existing masonry vaults consisting in the application at the extrados of a GFRP mesh reinforced mortar coating is herein presented.The effectiveness of the technique is investigated through non-linearstaticanalysisutilizinga2Dsmearcrackmodel.Solidbrickbarrelvaultswiththreedifferent aspect ratio between the arch rise and the curvature radius are considered (1, 0.75 and 0.6). Two different load patterns are analyzed: vertical and horizontal load, with distributions proportional to the self-weight. The mechanical characteristics of the masonry, the GFRP mesh and the reinforced mortar coating are assessed through experimental tests. The simulations permitted to evaluate the collapse mechanisms of the vaults, governed by the flexural behavior.The great effectiveness of the reinforcement technique was evidenced by comparing both the resistance and the displacement capacity of reinforced and unreinforced vaults

Cyclic tests on thin masonry vaults strengthened through composite reinforced mortar

2noThe paper deals with the strengthening of thin masonry vaults by means of a CRM (Composite Reinforced Mortar) strengthening technique based on Glass Fiber-Reinforced Polymer (GFRP) meshes embedded in a 30 mm thick mortar matrix, applied at the vault extrados or intrados and connected to the masonry abutments through steel bars and GFRP elements. The experimental campaign concerned quasi static cyclic tests performed on four full-scale samples, supporting their self-weight only and subjected to uniform horizontal transversal loading. The results of the tests are described in terms of crack pattern, failure mode and load-displacement graphs, referring both to the horizontal displacement monitored at the crown section and to the sliding at the spring sections. High improvements in terms of both resistance and displacement capacities emerged in respect to the plain masonry and the connection with the abutments resulted fundamental for ensuring the reinforcement effectiveness.reservedmixedNatalino Gattesco; Ingrid BoemGattesco, Natalino; Boem, Ingri

Diagonal compression tests on masonry walls strengthened with a GFRP mesh reinforced mortar coating

The paper presents the results of a broad experimental investigation conducted through diagonal compression tests on masonry specimens strengthened with a mortar coating applied on both surfaces of the wall and reinforced with a glass fiber reinforced polymer (GFRP) mesh. Four types of masonry, three different types of masonry mortar and five diverse GFRP meshes for the reinforcement were considered. In particular, solid brick masonry 250 and 380 mm thick, two-leaf brick masonry with rubble conglomerate infill and rubble stone masonry were tested. The diagonal compression tests, performed on 60 square masonry specimens with loading-unloading cycles up to the collapse, evidenced a good effectiveness of the strengthening technique in terms of both resistance and ductility. Results also showed the resistance increment in reinforced samples is generally greater for weaker masonry types and, referring to a single masonry type, for specimens built with a weaker mortar. Furthermore, the different GFRP meshes influenced very little the resistance of specimens, but higher reinforcement contents induced a lower decrease of the diagonal load after the cracking

Handling power losses in a DC microgrid through constrained optimization

This paper extends a hierarchical control approach for power balancing in a meshed DC microgrid while minimizing the power losses in the central transmission network. The control strategy is divided into three layers in hierarchical framework: i) the high level solves a continuous-time optimization problem which minimizes the DC-bus power loss and the electricity cost from the external grid power purchase through the combined use of differential flatness with B-splines parametrization; ii) the middle level employs a tracking Model Predictive Control (MPC) method which mitigates the discrepancies among the optimal and the actual profiles; iii) the low level controller handles the switching activity of the converters. The proposed approach is validated in simulation for a specific meshed DC microgrid system