2,214,103 research outputs found
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Flier for Girls Rock! DC concert at 9:30 Club, August 14, 2010
No full textFlier for Girls Rock! DC showcase at 9:30 Club on August 14, 2010. Flier features a drawing of a four-track recorder and headphones and the Girls Rock! DC logo
Girls Rock! DC 2010 official guide to rock
No full textBooklet containing a description of the Girls Rock! DC summer camp showcase mission and schedule for summer 2010, as well as tips and encouragement for beginning rock musicians
Flier for an AIDS benefit for the Carl Vogel Foundation and the ACT UP DC needle exchange program featuring Holy Rollers, Circus Lupus, Girls Against Boys and 3LG at Sanctuary Theater, December 18
No full textFlier for an AIDS benefit for the Carl Vogel Foundation and the ACT UP DC needle exchange program featuring Holy Rollers, Circus Lupus, Girls Against Boys and 3LG at Sanctuary Theater on Friday, December 18. All ages. Includes phone number for Positive Force DC for information. Features an illustration of a hand with snakes for fingers grasping the world and casting a shadow over a scared-looking man. Includes text \No-one is immune
Flier for a concert to benefit the DC Free Clinic featuring Fugazi, False Face Society, Crash Worship at St. Augustine's School, July 6
No full textFlier to benefit the DC Free Clinic featuring Fugazi, False Face Society, and Crash Worship at St; Augustine School on July 6. The flier features a quote on the footer stating, \you are not what you own....\ and in the background, Giorgio Beverly Hills perfume bottles
Behaviour of Modular Multilevel DC/DC ConverterWith DC Voltage Control Integrated in a Multi-terminal DC System Under Fault Conditions
No full textThe development of multi-terminal DC (MTDC) networks has various challenges as interconnecting grids of different voltages
and grounding schemes, DC grid protection and power flow. DC/DC converter has emerged as the solution for interconnecting
HVDC links with different specifications. In this paper, the Front-to-Front Modular Multilevel Converter (F2F-MMC) topology
is adopted for DC/DC converter, which can act as a firewall between the healthy and faulty grid during DC faults. Along with this,
DC/DC converters when operated in DC voltage control mode can provide supplementary functionalities such as participating in
DC grid voltage management and increasing the reliability of the system. In this study, the F2F-MMC converter is operated with
a virtual resistance DC voltage controller integrated into an MTDC system. A pole-to-pole DC fault is applied on the MTDC grid
and the influence of the virtual resistance controller associated with the DC/DC converter is studied for re-establishing the power
flow after DC faults
EMT simulation of an MTDC system integrating Modular Multilevel DC/DC converter with DC voltage control
No full textThe increasing demand to utilize renewable energy necessitates the transmission of power over long distances. HVDC technology has emerged as the optimal solution for this purpose due to fewer losses and good economic factors. Multi-terminal DC (MTDC) systems are being more focused nowadays, as they offer more advantages over Point to Point (P2P) HVDC scheme because the MTDC network adds more reliability and flexibility to the system. DC/DC converters are emerging as an important device for future MTDC transmission systems. They are required to interconnect HVDC links with different system characteristics such as different DC voltage levels, grounding schemes, and technologies. In addition to this, DC/DC converters are capable of providing additional features in the system like grid protection, DC voltage control, and power flow control. The majority of studies in the literature on DC/DC converters are predominantly focused on the context of either exploring different DC/DC converter topologies or their control and operation in constant power mode for interconnecting HVDC links, suitable for future MTDC grids.
This paper presents an MTDC test case integrating a DC/DC converter where the converter is working with a DC voltage controller and participating in the DC voltage management system. The influence of voltage-controlled DC/DC converter is studied by introducing power disturbances in the MTDC system. The system is modeled and simulated in EMTP software. The droop control technique known for the VSC converter for DC voltage control is extended to obtain a dual droop controller which is used with a DC/DC converter for controlling both DC grid voltages simultaneously. However, this control approach involves designing two droop coefficients for their respective DC grids, complicating the examination of their interaction. Another possibility is to use a new technique called “virtual resistance DC voltage control” which requires tuning only one parameter. The objective is to control DC grid voltages and establish a link between the interconnected networks. The control approach is validated through electromagnetic transient (EMT) simulations. Through the virtual resistance DC voltage control, the interconnected DC grids can share the power disturbance in the system and maintain the DC voltages under their specified limits. This makes the MTDC system more reliable and reduces the stress on the DC voltage management system. Modular multilevel converter (MMC) based topologies are used for DC/DC converters, namely F2F-MMC (front-to-front MMC) which can provide galvanic isolation between the two links and MMC-DC (M2DC) which does not provide galvanic isolation. A comparison analysis has also been made to compare their behavior with a virtual resistance controller. All converters are modeled using reduced order modeling methodology and the DC cables are modeled with wideband models.
The observations in this paper indicate that by employing the virtual resistance DC voltage controller, a connection has been established between interconnected networks, enabling HVDC links to actively participate in and share the power disturbances within the MTDC system. Apart from this, the virtual resistance control behavior remains consistent regardless of the topology of the DC/DC converter, thus demonstrating its robustness as a DC voltage controller
Common Mode Currents in DC Power Routers
No full textThe grid reinforcement and energy redirection needs have led to the emergence of Back-To-Back Voltage Source Converter (BTB-VSC) based dc power routers. This paper investigates the low frequency Common Mode Currents (CMCs) that arise in the system if the employed BTB-VSCs have an un-isolated ac path connected in parallel to their output ports. Simulation results are presented to show a sensitivity analysis of lower order harmonics in CMC with respect to the operating active and reactive power of the dc router, dc link voltage, link resistance, modulation method and pole capacitance. Experimental results are shared to show existance of lower order CMC in 3-wire ac link operating in parallel with the dc power router and these are mitigated using zero sequence controller
DC-091122F
No full textFirst, DC is asked to comment on different motion events exemplified with toys. Afterwards, imagining two children playing hide and seek, sentences on topological relations are elicited. Finally, DC and F make an imaginary travel in which they find a precious stone. In this story sentences with 'putting in' and 'taking out' are elicited
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