scholarly journals Modeling and Enhanced Control of Hybrid Full Bridge–Half Bridge MMCs for HVDC Grid Studies

Energies ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 180 ◽  
Author(s):  
Ricardo Vidal-Albalate ◽  
Jaume Forner
Keyword(s):  
Steady State ◽  
Dynamic Response ◽  
High Voltage ◽  
Direct Current ◽  
Simplified Models ◽  
Multilevel Converters ◽  
Electromagnetic Transient ◽  
High Voltage Direct Current ◽  
Modular Multilevel Converters ◽  
Different Types

Modular multilevel converters (MMCs) are expected to play an important role in future high voltage direct current (HVDC) grids. Moreover, advanced MMC topologies may include various submodule (SM) types. In this sense, the modeling of MMCs is paramount for HVDC grid studies. Detailed models of MMCs are cumbersome for electromagnetic transient (EMT) programs due to the high number of components and large simulation times. For this reason, simplified models that reduce the computation times while reproducing the dynamics of the MMCs are needed. However, up to now, the models already developed do not consider hybrid MMCs, which consist of different types of SMs. In this paper, a procedure to simulate MMCs having different SM topologies is proposed. First, the structure of hybrid MMCs and the modeling method is presented. Next, an enhanced procedure to compute the number of SMs to be inserted that takes into account the different behavior of full-bridge SMs (FB-SMs) and half-bridge submodules (HB-SMs) is proposed in order to improve the steady-state and dynamic response of hybrid MMCs. Finally, the MMC model and its control are validated by means of detailed PSCAD simulations for both steady-state and transients conditions (AC and DC faults).

Comparison Between Two-Level and Modular Multilevel Converters in High Voltage Direct Current Systems Under Fault Conditions

2021 ◽  
Author(s):  
Mikaela T. M. Barra ◽  
Maxwel S. Santos ◽  
Victor R. F. B. de Souza ◽  
Flavio B. Costa ◽  
Luciano S. Barros ◽  
...  
Keyword(s):  
High Voltage ◽  
Direct Current ◽  
Multilevel Converters ◽  
High Voltage Direct Current ◽  
Modular Multilevel Converters ◽  
Current Systems

Low Voltage Skin Burns

PEDIATRICS ◽  
1971 ◽  
Vol 48 (5) ◽  
pp. 831-832
Author(s):  
Charles W. Jarvis ◽  
Donald A. Voita
Keyword(s):  
Cardiac Function ◽  
High Voltage ◽  
Direct Current ◽  
Low Voltage ◽  
Electronic Devices ◽  
Laboratory Safety ◽  
High Voltage Direct Current ◽  
Electrical Devices ◽  
Different Types ◽  
The Subject

The hazards accompanying the increasing use of line-operated electrical devices for diagnosis and therapy as well as the more common hospital appliances such as electrically operated beds, television sets, radio sets, and so forth have been recently reemphasized.1 Most physicians are aware of the dangers of alternating current (60 Hz AC) or of high voltage direct current (DC) , especially in relation to cardiac function. However, few physicians seem to be aware of the hazards of low voltage direct current. A standard text2 on laboratory safety fails to mention the subject. Low voltage direct current is used with many different types of miniature electronic devices and iontophoresis.

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