Institution
Aalborg University – Esbjerg
About: Aalborg University – Esbjerg is a based out in . It is known for research contribution in the topics: Control theory & Photovoltaic system. The organization has 309 authors who have published 775 publications receiving 13638 citations. The organization is also known as: Aalborg University – Esbjerg & AUE.
Topics: Control theory, Photovoltaic system, Wind power, Voltage, Hypermedia
Papers published on a yearly basis
Papers
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TL;DR: In this paper, the authors analyze the stability problems of grid connected inverters used in distributed generation and demonstrate that the use of active damping helps to stabilise the system in respect to many different kinds of resonances.
Abstract: The aim of this paper is to analyze the stability problems of grid connected inverters used in distributed generation. Complex controllers (e.g., multiple rotating dq-frames or resonant-based) are often required to compensate low frequency grid voltage background distortion and an LCL-filter is usually adopted for the high frequency one. The possible wide range of grid impedance values (distributed generation is suited for remote areas with radial distribution plants) challenge the stability and the effectiveness of the LCL-filter-based current controlled system. It has been found out and it will be demonstrated in this paper that the use of active damping helps to stabilise the system in respect to many different kinds of resonances. The use of active damping results in an easy plug-in feature of the generation system in a vast range of grid conditions and in a more flexible operation of the overall system able to manage sudden grid changes. In the paper, a vast measurement campaign made on a single-phase system and on a three-phase system used as scale prototypes for photovoltaic and wind turbines, respectively, validate the analysis.
997 citations
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TL;DR: In this article, a hybrid system consisting of a proportional integral (PI) controller plus a generic hth harmonic resonant controller implemented in a frame rotating at the n th harmonic frequency is discussed in detail.
Abstract: Voltage source inverters connected to the grid in applications such as active rectifiers, active filters, uninterruptible power supplies, and distributed generation systems need an optimal ac current control. To obtain zero steady-state error at the fundamental frequency (i.e., unity power factor), the use of a standard integrator in a rotating frame is as effective as the use of a resonant controller in a stationary frame. However, the grid voltage harmonics influence the current controller and generate current harmonics unless several integrators in multiple rotating frames or resonant compensators in a stationary frame are adopted. In this letter, a hybrid system consisting of a proportional integral (PI) controller plus a generic hth harmonic resonant controller implemented in a frame rotating at the n th harmonic frequency is discussed in detail. The hth harmonic controller is able to decrease both the (h - n)th and (h + n)th harmonics, while the PI controller is able to decrease other harmonics if the synchronization phase signal adopted for the frame transformation is unfiltered. It is demonstrated that the use of a PI and sixth harmonic resonant compensator is effective for both positive and negative sequence fifth and seventh harmonics; hence, four harmonics are compensated with the proportional integral-resonant (PI-RES) controller implemented in a synchronous frame. Simulation and experimental tests validate the proposed analysis
662 citations
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TL;DR: Flow cytometric analysis revealed reduced damage with respect to cytoplasmic membrane potential and integrity in cells grown in the dynamic environments of the large scale reactor and the scale-down reactor.
443 citations
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TL;DR: The Unified Form Language (UFL) as mentioned in this paper is a domain-specific language for representing weak formulations of partial differential equations with a view to numerical approximation, which has been used to effortlessly express finite element methods for complex systems of PDEs in near-mathematical notation.
Abstract: We present the Unified Form Language (UFL), which is a domain-specific language for representing weak formulations of partial differential equations with a view to numerical approximation. Features of UFL include support for variational forms and functionals, automatic differentiation of forms and expressions, arbitrary function space hierarchies for multifield problems, general differential operators and flexible tensor algebra. With these features, UFL has been used to effortlessly express finite element methods for complex systems of partial differential equations in near-mathematical notation, resulting in compact, intuitive and readable programs. We present in this work the language and its construction. An implementation of UFL is freely available as an open-source software library. The library generates abstract syntax tree representations of variational problems, which are used by other software libraries to generate concrete low-level implementations. Some application examples are presented and libraries that support UFL are highlighted.
338 citations
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TL;DR: In this article, the use of large eddy simulations (LES) in numerical simulations of the gas-liquid flow in bubble columns is studied, and the LES shows better agreement with the experimental data than simulations using the k-var epsilon model, when the drag, lift and virtual mass forces are used, the transient behaviour that was observed in experiments can be captured.
321 citations
Authors
Showing all 309 results
Name | H-index | Papers | Citations |
---|---|---|---|
Frede Blaabjerg | 147 | 2161 | 112017 |
Henrik Jeldtoft Jensen | 102 | 1286 | 48138 |
Remus Teodorescu | 84 | 606 | 38521 |
Henrik Madsen | 81 | 848 | 27121 |
Youmin Zhang | 58 | 582 | 15226 |
Ramjee Prasad | 55 | 1004 | 22849 |
NG Niels Deen | 48 | 256 | 9101 |
Jakob Stoustrup | 44 | 331 | 7162 |
Gert Frølund Pedersen | 40 | 575 | 7807 |
Kim H. Esbensen | 39 | 216 | 12851 |
Istvan Z. Kovacs | 38 | 196 | 6287 |
Norbert Krüger | 37 | 229 | 9130 |
Per Stoltze | 37 | 73 | 7022 |
Sanjeevikumar Padmanaban | 34 | 367 | 5244 |
Ahmad Arabkoohsar | 33 | 142 | 2764 |