SuperGrid Institute wishes you an electric new year!
SuperGrid Institute wishes you an electric new year! [...]
Phd Juan PAEZ “HVDC Converters for the interconnection of HVDC grids”
In order to include large-scale renewable sources into the electrical system and to transport high amounts of energy through long distances, the actual AC grid must be upgraded. HVDC transmission grids appear as a promising solution to upgrade the system and answer correctly the future needs and requirements. The development of such grids can be done following two different approaches. For one side, a DC system designed totally from zero following a standardization of HVDC technology, and for the other side, an incremental evolution using the existing HVDC lines. The second approach seems more reasonable due to the reutilization of infrastructure, the inconvenient is that the technology used on each existing line is different. Thus, their interconnection will require DC¬DC converters as interface elements. These structures allow the interconnection of different HVDC schemes and offer more functionalities than only DC voltage adaptation like power flow control and protection.
NPC assessment in insulated DC/DC converter topologies using SiC MOSFETs for Power Electronic Traction Transformer
Power electronic traction transformers (PETT) are multilevel AC/DC on-board converters, studied for railway applications to replace traditional solution with low frequency transformers. This paper focuses on the insulated DC/DC converter in a PETT. Three variants of resonant single active bridges (R-SAB) with 3-level NPC primaries are optimised to maximise the efficiency, under mass and dimension constraints. They are sized and compared for a 2 MW PETT on a 15 kV/16.7 Hz railway infrastructure, using 3.3 kV SiC MOSFETs and nanocrystalline C-core transformers with cast resin insulation and forced air cooling. The highest efficiency at nominal power, 99.17 %, is reached for a configuration with a 3-level full bridge NPC primary, a 2-level full bridge secondary, and a 32.1 L/49.1 kg transformer operating at 6 kHz.
3-phase medium frequency transformer for a 100kW 1.2kV 20kHz Dual Active Bridge converter
The article presents a three-phase Medium Frequency Transformer being a part of a 100kW 1.2kV 20kHz Dual Active Bridge DC-DC converter. The transformer design is detailed focusing on winding and core power loss calculation. The high power three-phase MFT prototype is presented. The experimental results include the transformer impedance characteristics, no load test and three-phase DAB full load test waveforms.
Cost-performance framework for the assessment of Modular Multilevel Converter in HVDC transmission applications
This article proposes a methodology of Cost-Performance Assessment (CPA) enabling the efficient cost evaluation required for the Cost-Benefit Analysis (CBA). The proposed method is applied for the Modular Multilevel Converter (MMC) in offshore wind high voltage direct current (HVDC) transmission. Thanks to the developed model, an analysis of submodule voltage rating is performed demonstrating the interest of this methodology in the evaluation of new technologies for HVDC transmission. The analysis shows that increasing the submodule (SM) voltage could lead to savings in the MMC cost and weight.
Requirements for interconnection of HVDC links with DC-DC converters
The number of high voltage direct current (HVDC) links continue to increase over the years, most of them, for offshore applications or bulk power transmission over long distances. The present paper evaluates the possible development of a direct current (dc) grid in Europe given the present, and future, HVDC links. Eight potential cases for the interconnection between close links are suggested as starting scenario for a multiterminal network. The need of a dc-dc converter and its special requirements are evaluated in function of suggested interconnections. As an example, a case study is chosen to evaluate the behavior of an interconnection between line commutated converter (LCC) and voltage source converter (VSC) link using a front-to-front (F2F) isolated converter.
Assessment of the Impact of Split Storage within Modular Multilevel Converter
This paper deals with the opportunities to introduce split storage into an MMC. The analysis is focused on the internal energy exchange to maintain the proper function of the converter by using circulating current. Analysis shows that, SM capacitor voltage ripple or semiconductors load are greatly influenced by additional circulating current injection. This study helps to design Embedded ESSs in the converter to provide new function like ancillary services for power system operation. Finally, a simulation of an MMC with ESS confirms analytical calculations.
Interest of using a micro-meter spatial resolution to study SiC semi-conductor devices by Optical Beam Induced Current (OBIC)
In this paper we present a new test bench called micro-OBIC used to characterized wide band gap semi-conductor. Micro-OBIC allows to scan an Optical Beam Induced Current (OBIC) signal with a microscopic spatial resolution. We used micro-OBIC to characterize peripheral protection such as MESA, JTE or JTE in high voltage SiC device.
Static and Switching Characteristics of 10 kV-class SiC BJTs and Darlingtons
This paper reports the device design, fabrication and characterisation of 10 kV-class BJT. Manufactured devices have been packaged in single BJT, two paralleled BJTs and Darlington. The static and switching characteristics of the resulting devices have been measured. The BJTs (2.4mm² active area) show a specific on-resistance as low as 198 mΩ·cm² at 100 A/cm² and room temperature for a βMax of 9.6, whereas the same active area Darlington beats the unipolar limit with a specific on-resistance of 102 mΩ·cm² at 200 A/cm² (β=11) for a βMax of 69. Double pulse tests reveal state of the art switching with very sharp dV/dt and di/dt. Turn-on is operated at less than 100 ns for an EON lower than 4mJ, whereas the turn-off takes longer times due to tail current resulting in EOFF of 17.2 mJ and 50 mJ for the single BJT and Darlington respectively when operated at high current density. Excellent parallelisation have been achieved.
Power Hardware In-the-Loop validation of DC-DC power converter for offshore wind energy
he paper describes the development of a power converter small scale mock-up and a real time model of an off-shore wind farm. A Power Hardware In-the-Loop validation is proposed for a demonstration of grid architecture and control principles. The paper presents the design methodology of the PHIL test bench and underlines the contribution of PHIL in the design flow of power converter development for DC grid application. Experimental results of preliminary PHIL tests are presented.
