Search for dissertations about: "direct ac ac"

Showing result 1 - 5 of 53 swedish dissertations containing the words direct ac ac.

2. 1. Modeling of Modular Multilevel Converters for Stability Analysis

   Author : Luca Bessegato; Stefan Östlund; Staffan Norrga; Lennart Harnefors; Xiongfei Wang; KTH; []
   Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Modular multilevel converters MMCs ; stability; admittance; frequency-domain analysis; linearization techniques; current control; voltage control; ac ac converters; railway engineering.; Modulära multinivåomvandlare MMC ; stabilitet; admittans; frekvensanalys; linjäriseringsmetoder; strömreglering; spänningsreglering; ac ac omvandlare; järnvägsteknik.; Electrical Engineering; Elektro- och systemteknik;

   Abstract : Modular multilevel converters (MMCs) have recently become the state-of-the-art solution for various grid-connected applications, such as high-voltage direct current (HVDC) systems and flexible alternating current transmission systems (FACTS). Modularity, scalability, low power losses, and low harmonic distortion are the outstanding properties that make MMCs a key technology for a sustainable future. READ MORE

4. 2. Modeling and Control of VSC-HVDC Links Connected to Weak AC Systems

   Author : Lidong Zhang; Hans-Peter Nee; Alan Wood; KTH; []
   Keywords : Control; modeling; multivariable feedback control; HVDC; power systems; stability; subsynchronous torsional interaction; voltage-source converter; weak ac systems;

   Abstract : For high-voltage direct-current (HVDC) transmission, the strength of the ac system is important for normal operation. An ac system can be considered as weak either because its impedance is high or its inertia is low. READ MORE

5. 3. AC losses in HTS as a function of magnetic fields with arbitrary directions

   Author : Anna Wolfbrandt; Sven Hörnfeldt; Ole Tönnessen; KTH; []
   Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Electronics; High-temperatur superconductors; AC loss modelling; hysteresis; E - J characteristic; Elektronik; Electronics; Elektronik;

   Abstract : Although a superconductor has zero resistivity when carrying a direct current, losses do occur when it is exposed to an alternating magnetic field and/or is carrying an alternating current. The magnitude of these so-called AC losses depends on the operating temperature, the amplitude and the direction of the magnetic field, the transport current, and the frequency. READ MORE

6. 4. On Techno-economic Assessment of a Multi-terminal VSC-HVDC in AC Transmission Systems

   Author : Feng Wang; Chalmers tekniska högskola; []
   Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Transmission Grid.; Loss minimization; AC DC system; Transmission expansion planning; Multi-terminal VSC-HVDC; Cost minimization; Cost-benefit analysis; Electric power system; Optimal power flow;

   Abstract : The Voltage Source Converter based Multi-Terminal high voltage Direct Current transmission system (VSC-MTDC) is currently considered as an attractive technical option for increased transmission capacity and improved controllability and flexibility of an electric power grid, thanks to its unique performance characteristics, and the possibility of using the extruded XLPE cables. In the planning process of embedding a VSC-MTDC system into an ac transmission grid, one must assess the potential values in terms of improved energy efficiency, i. READ MORE

7. 5. On Stability Enhancement in AC/DC Power Systems through Multi-terminal HVDC Controllers

   Author : Omar Kotb; Mehrdad Ghandari; Oriol Gomis Bellmunt; KTH; []
   Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; AC DC power system; hybrid MTDC; multi-terminal HVDC; small signal stability; VSC-MTDC; Electrical Engineering; Elektro- och systemteknik;

   Abstract : Due to the increasing share of renewable energy sources in modern power systems and electricity market deregulation, heavy inter-regional and cross-border power flows are becoming a commonplace in system operation. Moreover, large-scale integration of renewable energy sources is expected to pace up, therefore new solutions have to be developed to integrate these intermittent sources, which are also characterized by being distributed over large geographical areas, such as offshore wind farms. READ MORE