6.5 kV Silicon Carbide Half-Bridge Power Switch Module for Energy Storage System Applications

As renewable resources such as wind and solar start to penetrate the electrical infrastructure, the transient behavior of these resources requires energy storage systems, such as batteries or flywheels, to buffer the fluctuations in output. Additionally, current silicon based semiconductor switches are limited in their ability to handle higher voltages and thus require large expensive systems to convert renewable resources. Power conversion systems in the 100 to 200 kW range are sought to address needs on the industrial user and community level, however the cost and size of the equipment must come down to meet municipality budgets and space limitations. The impact of a medium voltage switch could greatly shrink the weight and cost of power converters by reducing cable size, transformer size, and eliminating elaborate cooling systems all together. United Silicon Carbide, Inc. proposes to address the need for medium voltage switches by developing a unique 6.5 kV Silicon Carbide switch platform. The proposed switch module will provide a significantly smaller, more efficient and lower cost solution for power converters/inverters and will enable higher DC-Link voltages, up to 4 kV, for utility scale smart grid and energy management applications. By utilizing an approach that does not rely on Metal- Oxide-Semiconductor technology, the proposed module can run at much higher temperatures, thereby reducing cooling requirements dramatically and increasing reliability. The proposed module targets a high operation frequency of ~ 20-30 kHz which enables the use of much smaller transformers and magnetics. The proposed silicon carbide switch module is based on a unipolar design and is expected to overcome the following limitations of the competing technologies: Silicon power switches are plagued by excessive cooling requirements due to high switching and conduction losses, silicon carbide switches using metal-oxide materials suffer from long-term reliability concerns when operating at high temperatures, and silicon carbide bipolar switches which have much lower switching speeds, and suffer from a forward voltage drift problem due to defect propagation. Phase I focused on the device, driver and module designs, proof of high voltage packaging fundamentals as well as the semiconductor material crystal growth. Phase II will involve device processing, module assembly and proof of performance. In addition, USCi will obtain critical application requirements by consulting with a US based power conversion system manufacturer. Commercialization of such powers systems in a Phase III could create an economically attractive public/private partnership that would enable a more distributed behind the meter power generation and storage approach for primary customers utilizing industrial level utilities.