Alfonso Damiano

Second-order sliding-mode control of DC drives

One of the most recent topics in variable-structure systems theory is represented by the second-order sliding-mode control (2-SMC) methodology. This approach guarantees the same robustness and dynamic performance of traditional first-order SMC algorithms, and, at the same time, attenuates the chattering phenomenon, which is the main drawback in the actual implementation of this technique. In the present paper, a recently-proposed 2-SMC algorithm is used to synthesize a robust dc-drive control system which does not require current feedback and demands only rough information about the actual motor parameters. Stability and performance are analyzed, and an experimental comparison with a proportional-integral-based control scheme is reported.

Robust speed and torque estimation in electrical drives by second-order sliding modes

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 sliding-modes (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.

Real-Time Control Strategy of Energy Storage Systems for Renewable Energy Sources Exploitation

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.

Operating Constraints Management of a Surface-Mounted PM Synchronous Machine by Means of an FPGA-Based Model Predictive Control Algorithm

A model predictive control algorithm (MPC) suitable for Surface-Mounted Permanent Magnet Synchronous Machines (SPMs) is presented in this paper. It is based upon an accurate discrete-time model of the drive, accounting for both voltage saturation and current limitation constraints. It aims to properly manage these constraints in order to guarantee a good exploitation of both transient and steady state SPM performances, especially over flux-weakening operation. The effectiveness of the proposed MPC is first validated by a simulation study, in which the sensitivity of the proposed MPC against un-compensated inverter un-idealities and parameter uncertainties is properly highlighted and discussed, as well as the effects of sudden load torque variations. Then, an experimental study is performed on a radial-flux SPM driven by a Field Programmable Gate Arrays (FPGA) control board. The performances achievable by the proposed MPC are compared with those obtained by a conventional PI-based control system in order to highlight the improvements, especially regarding transient and flux-weakening operation.

Vehicles to grid (V2G) concept applied to a Virtual Power Plant structure

Renewable energy sources will play an increasingly central role in the power network of the future. The will to reduce the dependence on fossil sources as well as growing environmental awareness, both individually and governmentally, is forcing governments throughout the world to invest an enormous amount of capital in renewable energy sources. The European Union, through its Energy and Climate Policy, has fixed an ambitious target: to provide, 20% of electricity from renewable sources by 2020. The additional volatility introduced by renewable energy source to the grid can be compensated by energy storage systems as well as by demand control measurements and by the reinforcement of the power grid. These solutions can improve the system reliability of the electric grid and the efficiency of the energy supply and give more flexibility to the system. This study analyzes the possibilities to use electric vehicles connected to the grid as energy storage system within a Virtual Power Plant structure. Through the formulation of an optimization problem the optimal number of electric vehicles has been evaluated.

Optimization of harmonic performances in multilevel converter structures

In recent years, multilevel power converters have been gaining more and more interest in high voltage and high power conversion applications. Within this scenario, a very interesting approach lies in the use of semiconductors with different voltage ratings and different switching characteristics. For this aim, both GTOs and IGBTs could be employed, but a better technological solution surely lies in the use of IGBTs only, with different voltage ratings. Optimized multilevel power converter structures, based on the multi-point-clamped (MPC) concept or on the series connection of H-bridge inverters, could then be developed, exploiting the possibilities arising from the use of different voltage levels. The authors have developed an optimal modulation strategy that uses the redundant switching configurations of the MPC converter structure to achieve an increment of the output voltage level number. The novel approach proposed permits a reduction of the harmonic content of the voltage/current waveforms and an interesting optimization of the switching stresses of power semiconductor devices.

Experimental analysis of lithium iron phosphate battery performances

In this paper a study and an experimental analysis on lithium iron phosphate battery under different operating conditions is reported in order to investigate its potential application to electric vehicles and hybrid electric vehicles. The analysis of unloading and loading characteristics and the energetic analysis of storage process efficiency have been developed. Unloading and loading characteristics, temperature sensitivity in a range of −15° C to +50° C have been determined. To evaluate lithium iron phosphate battery dynamic performance for electric vehicle application a typical dynamic load variations test has been conducted.

Green Power Grids: How Energy from Renewable Sources Affects Networks and Markets

The increasing attention to environmental issues is forcing the implementation of novel energy models based on renewable sources. This is fundamentally changing the configuration of energy management and is introducing new problems that are only partly understood. In particular, renewable energies introduce fluctuations which cause an increased request for conventional energy sources to balance energy requests at short notice. In order to develop an effective usage of low-carbon sources, such fluctuations must be understood and tamed. In this paper we present a microscopic model for the description and for the forecast of short time fluctuations related to renewable sources in order to estimate their effects on the electricity market. To account for the inter-dependencies in the energy market and the physical power dispatch network, we use a statistical mechanics approach to sample stochastic perturbations in the power system and an agent based approach for the prediction of the market players’ behavior. Our model is data-driven; it builds on one-day-ahead real market transactions in order to train agents’ behaviour and allows us to deduce the market share of different energy sources. We benchmarked our approach on the Italian market, finding a good accordance with real data.

Direct torque and flux control of induction motor drives

A general approach to direct torque and flux control of an induction motor fed by a VSI is presented in the paper. The inverter switching patterns are generated as a function of the reference values of both the electromagnetic torque and of the controlled flux. In particular, the proposed control algorithm is independent of which kind of flux is controlled-rotor or stator. The results obtained by means of a real-time simulation show that the proposed control strategy allows very fast and accurate response of the drive.

A Vanadium-Redox-Flow-Battery Model for Evaluation of Distributed Storage Implementation in Residential Energy Systems

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.