A High Frequency Cuk 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.The Pegasus Toroidal Experiment at the University of Wisconsin – Madison utilizes solid-state switching for both Local Helicity Injection (LHI) and for magnet driving and control.Pegasus will upgrade their power systems.A new modular system that addresses the output ripple, efficient capacitor bank utilization, and electromagnetic interference is required.Eagle Harbor Technologies (EHT), Inc.is developing a high-frequency ?uk converter for fusion science applications.The ?uk 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.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 designed, built, and tested a high-frequency ?uk converter.The Phase I converter module could output 400 V and 4 kA for pulse lengths of 25 ms.The ?uk converter modules were tested at Pegasus where efficient capacitor bank utilization was demonstrated.These modules were operated in series and parallel to produce higher output voltages and currents.Additionally, EHT operated the converters in fault conditions in various configurations to identify what techniques are required for fault mitigation.In the Phase II program, EHT plans to develop a bidirectional ?uk converter, which has applications to driving inductive loads, like magnet coils used in fusion science.The bidirectional nature allows energy stored in the inductor to be rapidly removed at the end of a plasma shot, which reduces the heat load on the coil.EHT will design, build, and test bidirectional ?uk converter modules.These modules will also be tested using the capacitor bank and coils at Pegasus.At the end of the program, EHT will deliver several bidirectional ?uk converter modules to Pegasus for driving their poloidal field coils.The domestic fusion science community and specifically the Pegasus Toroidal Experiment would be the initial beneficiary from the development of the high frequency ?uk 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.