Sökning: "DC systems"

Visar resultat 11 - 15 av 231 avhandlingar innehållade orden DC systems.

1. 11. The control of VSC-HVDC and its use for large industrial power systems

   Författare :Cuiqing Du; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; VSC-HVDC; inner current controller; outer controller; PWM; dc dc converter; voltage dips; dc networks;

   Sammanfattning : With the recent developments in semiconductors and control equipment, Voltage Source Converter based High Voltage direct Current (VSC-HVDC) has become feasible. Due to the use of VSC technology and Pulse Width Modulation (PWM), it has a number of potential advantages: short circuit current reduction; rapid, independent control of the active and reactive power, etc. LÄS MER

3. 12. Control and Analysis of Pulse-Modulated Systems

   Författare :Stefan Almér; Ulf Jönsson; Gilead Tadmor; KTH; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Pulse-width modulation; Periodic systems; Stability analysis; Harmonic analysis; Lyapunov methods; Dynamic phasors; Harmonic transfer function; Switched mode power converters; Sampled data modeling; H-infinity synthesis; Optimization; systems theory; Optimeringslära; systemteori;

   Sammanfattning : The thesis consists of an introduction and four appended papers. In the introduction we give an overview of pulse-modulated systems and provide a few examples of such systems. Furthermore, we introduce the so-called dynamic phasor model which is used as a basis for analysis in two of the appended papers. LÄS MER

4. 13. Efficient Modeling of Modular Multilevel Converters for HVDC Transmission Systems

   Författare :Noman Ahmed; Hans-Peter Nee; Tim Green; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; High-Voltage dc; Modular Multilevel Converter; Voltage-Source Converter; HVDC Grids; Multiterminal DC Systems; Hybrid HVDC Breaker; Modeling; Electrical Engineering; Elektro- och systemteknik;

   Sammanfattning : The drive towards getting more and more electrical energy from renewable sources, requires more efficient electric transmission systems. A stronger grid, with more controllability and higher capacity, that can handle power fluctuations due to a mismatch between generation and load is also needed. LÄS MER

5. 14. Electromagnetic Modelling of Power Transformers for Study and Mitigation of Effects of GICs

   Författare :Seyedali Mousavi; Göran Engdahl; Ebrahim Rahimpour; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; transformer; hysteresis; DC magnetization; GMD; GICs; FEM; reluctance network method; low frequency transients; core losses; winding losses; eddy current losses; transformator; hysteresis; DC; likströmsmagnetisering; GMD; GIC; FEM; reluktansnätverksmodell; lågfrekventa transienter; kärnförluster; lindningsförluster; virvelströmsförluster; Electrical Engineering; Elektro- och systemteknik;

   Sammanfattning : Geomagnetic disturbances that result from solar activities can affect technological systems such as power networks. They may cause DC currents in power networks and saturation of the core in power transformers that leads to destruction in the transformer performance. LÄS MER

7. 15. Dynamic Analysis of Harmonics in Electrical Systems

   Författare :Erik Möllerstedt; Institutionen för reglerteknik; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Automation; converter control; modeling; linear time periodic systems; frequency domain analysis; harmonics; power systems; small signal stability; robotics; control engineering; Automatiska system; robotteknik; reglerteknik;

   Sammanfattning : Frequency domain analysis and design of power systems is complicated in the presence of harmonics, switching dynamics, nonlinearities, unbalances, and for systems with mixed ac/dc dynamics. The reason is that linearization of the system does not lead to a time invariant system, but a system with periodically time varying dynamics, which implies that there is coupling between different frequencies. LÄS MER