FG Regelungssysteme und Netzleittechnik
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The ongoing and unprecedented transformation of power systems leads to a reduction in the number of conventional power plants, which are the classical actuators of the grid. In addition, this development results in a decreasing system inertia, which is expected to yield faster frequency dynamics. Therefore power-electronics-interfaced units have to take over system control tasks and, in particular, frequency control. For this purpose, accurate and fast estimation algorithms for time-varying frequency signals are needed. Motivated by this fact, we propose a time-varying parameter estimator and a tuning criterion, which for sufficiently small initial estimation errors allows to reconstruct the time-varying frequency signal of a symmetric three-phase waveform in finite time. The proposed estimator is derived by using a time-varying version of the super twisting algorithm and its performance is illustrated via numerical examples.
Microgrids are distributed systems with high share of inverter-interfaced renewable energy sources where stable and reliable system operation is realized by suitably controlling the inverters. In this work, we focus on secondary frequency control, which is an important ancillary service provided by the inverters. In the literature on secondary frequency control, the effect of clock drifts has often been neglected. However, clock drifts are practically unavoidable parameter uncertainties in inverter-based microgrids and we show that the most commonly employed distributed secondary frequency controllers exhibit performance deteriorations when taking clock drifts explicitly into consideration. Motivated by this, we propose a novel alternative control law called generalized distributed averaging integral (GDAI) control, which achieves the secondary control objectives of steady-state accurate frequency restoration and proportional power sharing in the presence of clock drifts. In addition, we derive a sufficient tuning criterion in the form of a set of linear matrix inequalities (LMIs) which guarantees robust stability of the closed-loop equilibrium point in the presence of uncertain clock drifts. Finally, our analysis is validated extensively via simulation with comprehensive comparisons to other related distributed control approaches.
In der vorliegenden Arbeit wird die Eignung von Künstlichen Neuronalen Netzen hinsichtlich der Modellierung des komplexen Prozessverhaltens in einer Flachglasschmelzanlage analysiert. Die Identifikation und das Training der neuronalen Prozessmodelle erfolgen mit Messdaten einer Schmelzwanne für Flachglas. Im Vordergrund steht die Evaluation einer geeigneten Netzstruktur und die Parametrierung der Netzparameter. Dabei wird der Einfluss der einzelnen Netzparameter in Bezug auf die Genauigkeit der Netze eingehend untersucht. Anhand von Testdaten wird nachgewiesen, dass die qualitätsbestimmenden Temperaturen und der Glasstand mit Künstlichen Neuronalen Netzen hinreichend genau berechnet werden können.
Auf Basis der entwickelten neuronalen Prozessmodelle wird anschließend eine modellbasierte prädiktive Regelstrategie beschrieben. Neben der Auswahl des Gütekriteriums und des Optimierungsalgorithmus zur Berechnung zukünftiger Stellgrößen werden Richtlinien zur Dimensionierung der verfügbaren Reglerparameter abgeleitet.
Rural electrification has been one of the challenges faced by the government of Ghana due to extremely high cost of electricity extension to the rural areas. In order to meet up this challenge, the government of Ghana has been keen with the introduction of renewable energy programs as a solution for rural electrification. However, most of programs are also faced with the problem of being sustainable. After government and sponsors hand-over completed project to local users, they usually last only few years of their life span and are abandoned. This challenge has inspired this study to identify the potential barriers to the sustainability of rural electrification programs through technical and socio-economic evaluation of a solar PV rural electrification project in Ghana.
The approach of this study selected an on-going solar PV project (community solar system-CSS), that has been introduced on a pilot base across the whole of Ghana, which is to be adopted as a standard system for electrification solutions in rural areas in Ghana. This project was subjected to both technical and socio-economic evaluations covering 13 rural communities across the southern part of the country. Stakeholder interviews and review of literature were additional methodologies employed to gather information pertinent to the theme of the study.
The results of the study show that technically, the CSS project has simple design and operational technologies, which gives it high integration potential. However, the project faces the problem of technology misuse by the rural users and frequent failure of its components. The socio-economic barriers identified are: (1) ineffective management of the project due to a long chain of bureaucratic administrative management system, inadequate monitoring and supervision, and inconsistency in standardizing the cash flow of the project, and (2) low electricity capacity of the CSS project and other similar small scale renewable projects to meet the electricity requirements of the rural populates. These problems lead to gradual decline of users’ interest for such small scale renewable energy projects and subsequently result in project abandonment. It was concluded that small scale renewable energy programs lack the capacity to fully meet the energy requirement of rural populates; however, they are crucial as intervening solutions and play key role in rural development.
Zentraler Gegenstand der Arbeit ist die Anwendung von Robustheitskriterien im Frequenzbereich für den Entwurf robuster Regler mit einfacher Struktur. Im Blickpunkt stehen dabei unkomplizierte Regelstrecken aus Energie- und Verfahrenstechnik. Die gemessene Sprungantwort der Regelstrecke ist Ansatzpunkt für die hier vorgeschlagene Modellierungsmethode. Bevorzugt für die Kombination von PT1-Glied als nominelles Modell und PI-Regler folgen Untersuchungen zum erreichbaren Regelverhalten und die Überführung von Zeitbereichsvorgaben in eine frequenzabhängige Wichtungsfunktion. Die Robustheitskriterien werden grafisch durch punktweise Analyse auf dem gerasterten Parametergebiet ausgewertet, worin alle geeigneten Kombinationen der Reglerparameter als Lösung markiert werden. Die Algorithmen wurden in MATLAB-Programmen realisiert. Als Anwendungsbeispiele enthält die Arbeit den Reglerentwurf für einen Neutralisationsprozess, ein instabiles System und eine Druckregelstrecke.