Current state-of-the-art and future prospects for power semiconductor devices in power transmission and distribution applications

Since the first commercially viable thyristors appeared in the early 1960s, there has been a dramatic increase in the switched power ratings and versatility of high-voltage power semiconductor devices. By the mid 1970s, thyristors with switched power ratings of several MVA were being applied in high voltage dc transmission systems and static VAr compensators. The introduction, in the 1980s, of controlled turn-off devices, such as the gate turn-off thyristor (GTO) and insulated gate bipolar transistor (IGBT), broadened the application of high-voltage power devices to hard-switched converters and, by the start of the 21st century, controllable silicon power devices were available with voltage ratings of 12 kV and switched power capabilities of up to 40 MVA. A review of the current state-of-the-art in silicon high-voltage power semiconductor technology covers gate-commutated thyristors (GCT, lGCT) and IGBT devices, including the injection-enhanced IGBT or IEGT. Despite these considerable achievements, there is now mounting evidence that silicon-based power semiconductors are reaching their limit, both in terms of voltage rating and of switched power capability. The introduction of wide-band-gap semiconductor materials such as silicon carbide offers the potential to break through the voltage-switching frequency limitations of silicon, with power-switching frequency products more than two orders of magnitude higher. An analysis of the current status and future prospects for silicon carbide power electronic devices is presented, together with a case study comparing a variety of silicon and silicon carbide solutions in a 10 kV hard-switched converter application. It is shown that an all-silicon carbide switch offers the best electrical performance and lowest cost solution, in spite of higher per unit area device costs.