DOE SBIR Phase I/II: A High Frequency Ćuk Converter for Fusion Science Applications

The ability to robustly generate increased pulsed power levels at low cost is a challenge for the fusion energy community. Many applications supported by the Department of Energy’s (DOE) Fusion Energy Science (FES) program would benefit from a commercially available low-cost, robust, high current/voltage pulsed solid-state power supplies including pulsed magnetics, feedback and control systems for dynamic plasma stabilization in tokamaks, inductive and arc plasma sources, Radio Frequency (RF) helicity and flux injection, RF plasma heating and current drive schemes, ion beam generation, and RF pre-ionizer systems. The Pegasus Toroidal Experiment at the University of Wisconsin utilizes solid-state switching for both Local Helicity Injection (LHI) and for magnet driving and control. Pegasus will upgrade their power systems in the near future. A new modular system that addresses the output ripple, efficient capacitor bank utilization, and electromagnetic interference is required.

EHT is developing a Ćuk converter for fusion science applications. The Ćuk converter has low output ripple; high efficiency; voltage gain greater than one, allowing for deeper energy storage utilization; continuous power flow that lowers output EMI reducing noise generation; continuous input and output current – energy flow from the series capacitor allows for greater control of the injector currents; series arrangements can be utilized that isolates individual switch modules so a failure does not potentially damage all solid-state switches. EHT will utilize previously developed precision gate drive technology that allows for high frequency switching, which reduces the capacitor and inductor values significantly, making the design more compact and lower cost.

In the Phase I program, EHT will design, build, and test a Ćuk converter module prototype. EHT will SPICE model the Ćuk converter module to identify challenges that must be overcome in the design process. The PCBs will be designed utilizing EHT switching technology. The Ćuk converter module will be assembled and tested at EHT to map out the safe operating area. With the testing results, the Ćuk converter module design will be reviewed and a plan developed for second generation module to be built in a potential Phase II program. EHT will work with Pegasus to develop a plan to produce Ćuk converter modules that can be delivered to Pegasus for their magnet upgrade in a potential Phase II program.

The domestic fusion science community, specifically the Pegasus Toroidal Experiment, will be the initial beneficiary from the development of the high frequency Ćuk converter switching modules. This new converter would allow for an overall increase for the LHI system to over 32 MVA and continued work in a potential Phase II program would significantly increase at least the Toroidal magnet current drive capability from 12 kA to over 24 kA. There is also an international market for power amplifier and similar devices in private fusion start-ups and international fusion programs and experiments.