Design and practical implementation of a fractional order proportional integral controller (FOPI) for a poorly damped fractional order process with time delay

One of the most popular tuning procedures for the development of fractional order controllers is by imposing frequency domain constraints such as gain crossover frequency, phase margin and iso-damping properties. The present study extends the frequency domain tuning methodology to a generalized range of fractional order processes based on second order plus time delay (SOPDT) models. A fractional order PI controller is tuned for a real process that exhibits poorly damped dynamics characterized in terms of a fractional order transfer function with time delay. The obtained controller is validated on the experimental platform by analyzing staircase reference tracking, input disturbance rejection and robustness to process uncertainties. The paper focuses around the tuning methodology as well as the fractional order modeling of the process' dynamics

Advanced Testing Chain Supporting the Validation of Smart Grid Systems and Technologies

New testing and development procedures and methods are needed to address topics like power system stability, operation and control in the context of grid integration of rapidly developing smart grid technologies. In this context, individual testing of units and components has to be reconsidered and appropriate testing procedures and methods need to be described and implemented. This paper addresses these needs by proposing a holistic and enhanced testing methodology that integrates simulation/software- and hardware-based testing infrastructure. This approach presents the advantage of a testing environment, which is very close to f i eld testing, includes the grid dynamic behavior feedback and is risks-free for the power system, for the equipment under test and for the personnel executing the tests. Furthermore, this paper gives an overview of successful implementation of the proposed testing approach within different testing infrastructure available at the premises of different research institutes in Europe.Comment: 2018 IEEE Workshop on Complexity in Engineering (COMPENG

The PP&S100 Project: Process Control as an Information System Instance

The Project PP&S100, Problem Posing & Solving, is part of a set of initiatives promoted by the General Directorate of the Italian Ministry of Education, Research and University, for supporting the many innovations that have recently affected curricula at the upper secondary level. Main goals of the project include strengthening computer science culture and enhancing its role as a scientific discipline; founding education processes on logics, mathematics and computer science weaved together to pursue an interdisciplinary scenario, building a culture of "problem posing and solving" by investing across a broad disciplinary group of subjects, ensuring growth of computer science based training of trainers and practicing activities within specific social networks and virtual learning environment to share learning materials, teaching supplies, mentoring and self-evaluation. This work presents a hierarchical conceptual model for "Computational Thinking" assumed by PP&S100, formalized according to the outcomes shown by information systems courses held at the Politecnico di Torino and validated using Process Control as an information system instanc

Optimization of building performance via model-based predictive control

Il controllo predittivo basato su modello (MPC) è una tecnica di controllo avanzata che ha svolto un ruolo importante nella gestione di molti processi nel settore industriale. Oggi, nell’ottica di una gestione energetica efficiente degli edifici, l’utilizzo di questa strategia si sta dimostrando una soluzione promettente per ridurre al minimo i consumi e i costi energetici complessivi. Tuttavia, gli studi sulla sua fattibilità tecnica in edifici esistenti sono ancora in una fase iniziale. Pertanto, il risultato principale di questa tesi è la progettazione e lo sviluppo di un prototipo hardware e software per la verifica sul campo di un sistema di controllo predittivo, basato su modello, integrando un modello predittivo virtuale della porzione dell'edificio in esame, il controllore e l'interfaccia grafica per i dispositivi di monitoraggio e regolazione utilizzati. Inoltre, particolare attenzione è stata posta sulla fattibilità tecnica relativa all'implementazione di un tipico sistema MPC, che include un sottosistema di monitoraggio, un set di acquisizione dati e un metodo di identificazione del sistema per ottenere il modello per il controllore, mediante un approccio di modellazione grey-box. La fase di modellazione e l'approccio empirico sviluppato sono presentati nella prima parte di questa tesi di ricerca, mentre la parte centrale riguarda: lo sviluppo del prototipo di controllo predittivo, basato su modello, all'interno di uno strumento virtuale del software LabVIEW e la descrizione del test sperimentale, effettuato durante la stagione di riscaldamento, garantendo la normale operatività dell’edificio durante l'intero periodo di monitoraggio. Infine, è presentato lo studio sviluppato in ambiente di simulazione per indagare il potenziale della logica di controllo per la valutazione di scenari di riqualificazione. Il focus è sulla definizione dei principali componenti del simulatore MPC e sui risultati ottenuti testando uno degli scenari di intervento.Model Predictive Control (MPC) is an advanced control technique which has played an important role in the management of many processes in the industry sector. Nowadays, in the perspective of an efficient building energy management, the exploitation of this strategy is proving to be a promising solution for minimising overall energy consumptions and costs. However, investigations on the feasibility of the technique in real existing buildings are at an initial stage. Hence, the main outcome of this dissertation is the design and development of a prototype hardware and software set up for on-field testing of a model-based predictive control system, integrating a virtual predictive model of the portion of the building under investigation, the controller and the interface to the monitoring and regulation devices used. Moreover, this research is addressed to investigate the technical feasibility of the development and deployment of a typical MPC system, which includes a monitoring sub-system, a data acquisition set up and a system identification method to obtain the model for the controller by means of a grey-box modelling approach. The modelling phase and the empirical approach developed are presented in the first part of this research thesis, while the core part concerns: the development of the MPC prototype, within a virtual instrument of LabVIEW software and the description of the experimental test, which was carried out during heating season, ensuring normal building operation during the entire monitoring period. Finally, this dissertation presents the study developed in simulation environment to investigate the potential of the control logic for the evaluation of retrofitting scenarios. The focus is on the definition of the main MPC simulator components and on the results obtained by testing one of the intervention scenarios

The study of the self-damping properties of overhead transmission line conductors subjected to wind-induced oscillations.

Doctoral Degree. University of KwaZulu-Natal, Durban.Conductors are flexible, elastic structural components of power lines. The relatively high flexibility of the conductors, coupled with the long spans and the axial tension, makes conductors to be highly prone to dynamic excitation such as wind loading. The problem of the dynamic behavior of overhead power transmission line conductors under the action of wind and other forms of excitations is very important, since it proffers the optimal design of the line in terms of its dynamic characteristics. Thus, mechanical vibration of power lines needs to be mitigated, especially from aeolian vibration as they can lead to damage of the lines causing power interruptions. The dynamic behaviour of conductors can be influenced by its damping. However, available tools for the analysis of this phenomenon is scarce. The objective of this study is to evaluate the conductor self-damping. The goal is to characterize and ascertain the influence of various conductors’ parameters on the amount of energy dissipation. In this study, a numerically based investigation of the response of conductors was carried out i.e. finite element analysis (FEA or FEM). This was used to model the conductor using a new modeling approach, in which the layers of its discrete structure of helical strands were modelled as a composite structure. Due to the helical structure of the conductor strands, this give rise to inter-strands contacts. During bending caused by external loading, the stick-slip phenomenon does occur around the contact region resulting in damping of energy out of the system. Characterizing the damping mechanism as hysteresis phenomenon, this resulted from coulomb’s dry-friction with the stick-slip regime at contacts points between the conductor strands. Employing contact mechanics to characterize and the use of FEM to discretize these contact regions, parameters such as the contact forces, strain and stress were established. When the conductor experiences a dynamic excitation in a sinusoidal form, a hysteresis loop is formed. The use of contact region parameters, to evaluate the area of the hysteresis loop and the area of the loop determines the amount of self-damping. Experimental studies were conducted to validate the FEM model. Two forms of experiment were done. The first was the sweep test, done at a specified axial tension i.e. as a function of its ultimate tensile strength. This was used to determine the resonance frequencies for the conductors. In the second test, using the determined resonance frequencies from the first test were used to vibrate the conductors at these frequencies to establish the hysteresis loop at the same specified axial tension. The experiment was conducted with four different conductors with different number of layers. This was used to establish the relation between the numbers of layer and the amount of damping from the conductor. The conductors’ vibration experimental results obtained at a defined axial tension (as percentage of its UTS) correlate with that of FEM model. The results obtained showed a general increase in the resonance frequencies of vibration and a decrease in damping as the axial tension of the conductor is increased. The establishment of the hysteretic constitutive behaviour of strands under specific loading conditions as described in the thesis, using this FEM model, an algorithm was developed to evaluate the conductor self-damping. Based on this algorithm, computer programs have been developed to evaluate the conductor’s dynamic behaviour and implemented in MATLAB environment. Due to the very close relation between damping and conductor fatigue, this model can also be extended to investigate fatigue failure of conductors

Analog Testing, Characterization, and Low-Order Model Extraction using LabVIEW Automation

Testing circuits is a hands-on, time intensive process; it is also one of the most important steps in a design cycle. The most well designed circuit is only an academic exercise if it does not work in real life. The time and cost associated with bench level testing pales in comparison to testing for extreme environments. Testing in extreme heat, cold or radiation introduces a large set of challenges that are rarely encountered in standard bench level testing. The two most pronounced problems are the inaccessibility of the devices under test and time constraints, both short and protracted. Due to the physical properties of devices and circuits there is a short window in which all testing must be conducted for each incremental step during extreme environment tests. This time requirement does not present a significant challenge when testing a single circuit or device, but the cost associated with this testing is enough to encourage a more efficient method. The primary goal of this work is to reduce the time required to perform tests through the use of automation and parallel test schemes. The automation software chosen for this project was LabVIEW. LabVIEW is a graphical based programming language with an extensive library of functions for interfacing with test instrumentation. Due to the graphical nature of this language, display of measurement data is essentially a byproduct of the program. This allowed for confirmation of proper operation and immediate rectification if a problem was discovered. This paper will cover the key parameters of common devices and circuits, methods for extracting these parameters from other prevailing effect, and methods for automating these tests through the use of computer based tools such as LabVIEW

Nonlinear Analysis and Control of Interleaved Boost Converter Using Real-Time Cycle to Cycle Variable Slope Compensation

Switched-mode power converters are inherently nonlinear and piecewise smooth systems that may exhibit a series of undesirable operations that can greatly reduce the converter's efficiency and lifetime. This paper presents a nonlinear analysis technique to investigate the influence of system parameters on the stability of interleaved boost converters. In this approach, Monodromy matrix that contains all the comprehensive information of converter parameters and control loop can be employed to fully reveal and understand the inherent nonlinear dynamics of interleaved boost converters, including the interaction effect of switching operation. Thereby not only the boundary conditions but also the relationship between stability margin and the parameters given can be intuitively studied by the eigenvalues of this matrix. Furthermore, by employing the knowledge gained from this analysis, a real-Time cycle to cycle variable slope compensation method is proposed to guarantee a satisfactory performance of the converter with an extended range of stable operation. Outcomes show that systems can regain stability by applying the proposed method within a few time periods of switching cycles. The numerical and analytical results validate the theoretical analysis, and experimental results verify the effectiveness of the proposed approach