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Direct Predictive Current Control of GridConnected Neutral Point Clamped Inverterfor Wave Power Extraction
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
2010 (English)Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
2010.
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:uu:diva-218178OAI: oai:DiVA.org:uu-218178DiVA: diva2:695002
Conference
International Symposium on Power Electronics Electrical Drives Automation and Motion (SPEEDAM), 2010
Available from: 2014-02-09 Created: 2014-02-09 Last updated: 2014-03-05
In thesis
1. Grid Connected Three-Level Converters: Studies for Wave Energy Conversion
Open this publication in new window or tab >>Grid Connected Three-Level Converters: Studies for Wave Energy Conversion
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis presents an electrical system analysis of a wave energy converter (WEC) for the objective of grid connection. To transfer the enormous amount of power from waves to the load centers, efficient power electronic systems are essential. This thesis includes the modeling of a buoy–translator dynamics and the modeling of a linear permanent magnet generator along with simulation and experimental validation. Diode bridge rectifiers are considered for rectification to avoid the complex linear generator control at the input side. To reduce the size and the cost of energy storage elements, DC voltage regulation is done using a DC/DC converter.

To achieve smooth and high power, many WECs need to be connected to a common DC link. A neutral point clamped inverter is considered for the DC/AC conversion due to its advantages over conventional topologies. Various pulse width modulation schemes are tested for the inverter to choose the optimum PWM method. The harmonics in the inverter output voltage is derived numerically and compared with simulation and experiment to understand the effect of dead-time in the inverter operation.

Depending on the load current drawn from the inverter, the voltages in the two input capacitors of a three-level neutral point clamped inverter deviates from equilibrium unless the neutral point is grounded. To avoid this voltage imbalance as well as to regulate the DC link voltage a dual output boost converter with pulse delay control is proposed. The modeling, simulation and experiments show an improvement in the compensation voltage using pulse delay control compared to the previously proposed methods in the literature. The synchronous current control and the grid connection of the three-level converter have been accomplished in the laboratory. 

Finally, the three-level power converter system has been tested with a linear permanent magnet generator at Lysekil to analyze the controller requirements.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2014. 78 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1123
Keyword
Wave energy, power converters, control strategies, grid connection
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Electronics
Identifiers
urn:nbn:se:uu:diva-218219 (URN)978-91-554-8875-8 (ISBN)
Public defence
2014-03-26, Häggsalen, Lägerhyddsvägen 1, Angstrom laboratory, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2014-03-04 Created: 2014-02-10 Last updated: 2014-12-02Bibliographically approved

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Krishna, RemyaLeijon, Mats

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