One of the most recent topics in variable-structure\ud
systems theory is represented by the second-order sliding-mode\ud
control (2-SMC) methodology. This approach guarantees the same\ud
robustness and dynamic performance of traditional first-order\ud
SMC algorithms, and, at the same time, attenuates the chattering\ud
phenomenon, which is the main drawback in the actual implementation\ud
of this technique. In the present paper, a recently-proposed\ud
2-SMC algorithm is used to synthesize a robust dc-drive control\ud
system which does not require current feedback and demands only\ud
rough information about the actual motor parameters. Stability\ud
and performance are analyzed, and an experimental comparison\ud
with a proportional–integral-based control scheme is reported
Islanding is known as a management procedure of the power system that is implemented at the distribution level to preserve sensible loads from outages and to guarantee the continuity in electricity supply, when a high amount of distributed generation occurs. In this paper we study islanding on the level of the transmission grid and shall show that it is a suitable measure to enhance energy security and grid resilience. We consider the German and Italian transmission grids. We remove links either randomly to mimic random failure events, or according to a topological characteristic, their so-called betweenness centrality, to mimic an intentional attack and test whether the resulting fragments are self-sustainable. We test this option via the tool of optimized DC power flow equations. When transmission lines are removed according to their betweenness centrality, the resulting islands have a higher chance of being dynamically self-sustainable than for a random removal. Less connections may even increase the grid’s stability. These facts should be taken into account in the design of future power grids.
An optimal energy storage system (ESS) management procedure devoted to full renewable energy sources (RESs) exploitation is presented in this paper. It consists of an appropriate scheduling procedure and a real-time control strategy, which both aim to increase the RES penetration level as much as possible. In particular, the one-day-ahead scheduling procedure synthesizes the combined RES-ESS energy production profile with the aim of minimizing the RES energy production curtailments by means of ESS energy buffering. The real-time control strategy is developed in order to track the scheduled profile as well as possible by mitigating forecasting errors, thus improving RES reliability. The worth and effectiveness of the proposed management procedure is verified through a wide simulation study, which is carried out by means of the Matlab software package
This paper presents the synthesis and practical implementation of a robust digital differentiator that provides the first and second derivative of a sampled smooth signal. The robustness of the proposed digital device, based on second-order slidingmodes (2-SMs), is analyzed with respect to measurement errors. Experimental results on an induction motor (IM) drive show that fast and accurate estimates of speed and torque can be obtained in several operating conditions by double differentiation of the encoder position measurement.
A vanadium-redox-flow-battery (VRFB) model suitable for annual energy feasibility analyses of distributed storage implementation is presented in this paper. The validation of the proposed 6-kW/20-kWh VRFB semiempirical model, which takes into account auxiliary power consumption and operational aspects such as startup and standby behavior, is reported. The comparison between the simulation and the experimental results shows a good matching, quantified by the maximum root-mean-square deviation of the stack energy equal to 1.57% and 2.47% during charge and discharge, respectively. Moreover, the VRFB model is used in an application model of a residential building including a photovoltaic system and heat pump. Based on variation of control parameters, the energy efficiency for the proposed application has been maximized. Finally, a comparison with a scaled VRFB model (3 kW/10 kWh) is discussed with respect to the increase of the VRFB utilization and overall energy efficiency, confirming the effectiveness of the proposed model for distributed energy storage sizing and management in residential systems
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