- AG 1 Strategic Advisory Group
- AG 2 DC Grid Coordination
- AG 3 Communication and website
- AG 4 HVDC System Performance
- B4-58 Devices for Load flow Control and Methodologies for Direct Voltage Control in a Meshed HVDC Grid
- B4-60 Designing HVDC Grids for Optimal Reliability and Availability Performance
- B4-63 Commissioning of VSC HVDC Schemes
- B4-66 Implications for harmonics and filtering of staggered installation of HVDC converter stations in proximate locations
- B4-67 Harmonic aspects of VSC HVDC, and appropriate harmonic limits
- B4-68 Revision of Technical Brochure 92 - DC Harmonics and Filtering
- B4-69 Minimizing loss of transmitted power by VSC during overhead line fault
- B4-70 Guide for Electromagnetic Transient Studies involving VSC converters
- B4-71 Application guide for the insulation coordination of Voltage Source Converter HVDC (VSC HVDC) stations
- B4-74 Guide to Develop Real-Time Simulation Models (RTSM) for HVDC Operational Studies
- B4-75 Feasibility Study for assessment of lab losses measurement of VSC valves
- B4-76 DC-DC converters in HVDC Grids and for connections to HVDC systems
- B4.72 DC grid benchmark models for system studies
- B4/B5-59 Control and Protection of HVDC Grids
- JWG A3/B4.34 Technical requirements and specifications of state-of-the-art DC switching equipment
- JWG B4/B1/C4.73 Surge and extended overvoltage testing of HVDC Cable Systems
- JWG B4/C1.65 Recommended voltages for HVDC grids
- JWG C2.B4.38 Capabilities and requirements definition for Power Electronics based technology for secure and efficient system operation and control
- JWG C4/B4.38 Network Modelling for Harmonic Studies
B4-76 DC-DC converters in HVDC Grids and for connections to HVDC systems
It is accepted that DC-DC will play an important role in DC grids but the exact functions, performance requirements and applications are not clear. DC-DC converters will be essential in transforming DC voltage but they also may have other functions. As an example, many DC-DC converters can work as DC circuit breakers and fault current limiters. In particular DC-DC converters provide alternative solutions for some DC grid topologies and more work is required to understand how to exploit DC-DC converters in developing/simplifying DC grid protection and control. DC-DC converters might facilitate power exchange between different DC topologies, i.e. monopolar and/or bipolar systems. They could meet other requirements like power control, voltage control, regulation of DC harmonics, energization and start up, and integration of wide range of existing DC systems.
The objectives of the WG are to:
1. Confirm the feasibility of high power DC-DC converters and provide basic technical characteristics in terms of DC configurations (monopole, bipole, symmetric/asymmetric, isolated/non-isolated) and power/voltage ranges.
2. Identify the role and need for DC-DC converters in DC Grids.
3. Evaluate the applications for DC-DC converters in interconnecting HV and MV DC systems.
4. Identify benefits of DC-DC converters in applications of tapping on HVDC
The working group will review principal technology concepts like: non-isolated converters, isolated dual-active-bridge, DC-DC auto-transformers, high/low stepping ratios, multiport converters and others. The performance indicators will be studied, including range/variation of DC-DC stepping ratios, efficiency, DC fault isolation capability and power flow control. The power reversal capability will have important implications on the DC-DC technology costs and losses. In particular this WG will provide guidelines on the power reversal options (DC voltage or DC current reversal) and link these options with DC-DC technologies. It is not the intention to delve in depth in DC-DC technologies (particularly not MV DC-DC concepts), but rather to collate knowledge on accepted technologies and to establish a platform for further developments. Some attention will also be given to DC-DC modelling methods.
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