Silicon (Si) insulated-gate bipolar transistors are widely used in railway traction converters. In the near future, silicon carbide (SiC) technology will push the limits of switching devices in three directions: higher blocking voltage, higher operating temperature, and higher switching speeds. The first silicon carbide (SiC) MOSFET modules are available on the market and look promising. Although they are still limited in breakdown voltage, these wide-bandgap components should improve traction-chain efficiency. Particularly, a significant reduction in the switching losses is expected which should lead to improvements in power-weight ratios. Nevertheless, because of the high switching speed and the high current levels required by traction applications, the implementation of these new modules is critical. An original method is proposed to compare, in terms of stray inductance, several dc bus-bar designs. To evaluate the potential of these new devices, a first set of measurements, based on a single-pulse test-bench, was obtained. The switching behavior of SiC devices was well understood at turn-off and turn-on. To complete this work, the authors use an opposition method to compare Si-IGBT and SiC-MOSFET modules in voltage source inverter operation. For this purpose, a second test-bench, allowing electrical and thermal measurements, was developed. Experimental results confirm the theoretical loss-calculation of the single-pulse tests and the correct operation of up to three modules directly connected in parallel. This analysis provides guidelines for a full SiC inverter design, and prospects for developments in traction applications are presented.

The test and the characterization of medium or high-power electronic converters, under nominal operating conditions, are made difficult by the requirement of high-power electrical source and load. In addition, the energy lost during the test may be very significant. The opposition method, which consists of an association of two identical converters supplied by the same source, one operating as a generator, the other as a receptor, can be a better way to do these test. Another advantage is the possibility to realize accurate measurements of the different losses in the converters under test. In the first part of this paper, the characteristics of the method concerning loss measurements are compared to those of the electrical or calorimetric methods, then it is shown how it can be applied to different types of power electronic converters, choppers, switched mode power supplies, and pulsewidth modulation inverters. In the second part, different examples of studies conducted by the authors, and using this method, are presented. They have varying goals, from the test of soft-switching inverters to the characterization of integrated gate-commutated thyristor (IGCT) devices mounted into 2-MW choppers.

this paper highlights the potential of medium voltage DC electrification for railway traction. A method is proposed for determining the DC voltage level in order to guarantee, in terms of traffic, equivalent performances to an AC electrified railway line. Railroad traffic, type of transport service and railway network topology being given, the analysis method takes into account the following constraints: voltage at the pantograph, heating of overhead-line and rail-to-ground voltage. Once the DC voltage level is chosen, the DC electrification system is compared with a standard 25 kV AC electrification in the case of the French high-speed line from Paris to Strasbourg.

In today's voltage source converter HVDC solutions, insulated-gate bipolar transistors (IGBTs) are used exclusively, generally in module form where the modular multilevel converter is concerned; this entails a number of protective measures that increase complexity and cost. As we move to higher transmitted powers, the use of integrated gate-commutated thyristors (IGCTs) would allow both higher voltages and currents while simultaneously reducing losses, failure rates, and costs, as this paper tries to demonstrate by comparing current production IGCTs with both current module and press-pack IGBTs.

Today, in Electric Railways, the old DC supply systems are reaching their limits. To improve their efficiency and increase railroad traffic, a new DC Electrification has recently been proposed at 9-kV. It is now necessary to prepare the migration of infrastructure and rolling stock, using Power-Electronic-Transformers (PETs), for adaptation to this voltage level. For this application, high efficiency and reduced volume are essential. This paper clearly demonstrates that it is now possible to achieve compact, high-power, isolated DC-DC converters using 3.3-kV SiC-MOSFET power modules with high efficiency. After a preliminary study based on simulations, the paper focuses on characterization and implementation of elementary isolated DC-DC converters. The proposed topology is a series-resonant converter rated for a nominal power of 300-kW at 1.8-kV. First, laboratory testing using an “opposition-method” is used to evaluate the elementary converters up to their nominal power using both electrical and thermal measurements to accurately determine losses and efficiency. At the nominal output power, an efficiency of 98.93% is obtained. This is quite remarkable for an isolated DC-DC converter operating under 1.8-kV with a switching frequency of 15-kHz. Finally, two elementary isolated DC/DC converters are associated in ISOP configuration (Input Seriesed/Output Paralleled) in order to achieve a 3-kV/1.5-kV PET with a nominal power of 600-kW as a prelude to the final 9-kV/1.5-kV power conversion.

Silicon (Si) insulated-gate bipolar transistors (IGBTs) are widely used in power converters. Silicon carbide (SiC) technology will push the limits of switching devices in three directions: higher blocking voltage, higher operating temperature, and higher switching speed. The first SiC-metal-oxide-semiconductor field-effect transistor (MOSFET) half-bridge modules (SiC HBM) are now commercially available and look promising. Although they are still limited in breakdown voltage, these components should, for instance, improve traction-chain efficiencies. In particular, a significant reduction in switching losses is to be expected which should lead to improvements in power-to-weight ratios-of particular interest for rolling-stock. Nevertheless, because of the high switching speed and the high current levels required by traction applications, the implementation of these modules is critical. In this paper, the authors investigate the parallel connection of SiC HBM with a focus on traction equipment. The key points are underlined and an original approach is proposed to design the bus-bar and the gate-drive circuit. Experimental results performed on an opposition method test bench, valid the correct operation of three SiC modules in parallel.