DEEP PPU team has achieved one of the main research goals of the project, the Radio-Frequency Generator (RFG) unit has experimentally demonstrated the ability of supplying an emulated Gridded Ion Thruster (GIT) through a 6 meters high frequency harness (hundreds of kHz to 1 MHz), providing 1kW power. High frequency harness has shown appropriate behavior, being designed as a trade-off among high frequency parasitic components: ac resistance, inductance and capacitance. Harness model based on Finite Element Analysis is in good agreement with experimental behavior, being used to design and optimized the high frequency resonant inverter and the filter network of the RFG. The resonant inverter is designed based on GaN semiconductors and has been validated operating in closed loop based on Digital control that is self-synchronized with the resonant frequency of the load.
Proposed DEEP PPU solution for the DC/DC converter of a Radio-Frequency Generator (RFG) has been successfully validated on a 1kW demonstrator based on GaN semiconductors and Digital Control. This DC/DC converter is in charge of the power and voltage regulation of the RFG unit that supplies the Gridded Ion Thruster (GIT). The converter is operated in Triangular Current Mode (TCM) to assure Zero Voltage Operation (ZVS) in the whole operation range to minimize losses and keep sensible temperature in the GaN semiconductors despite operating at hundreds of kHz; 98.7% efficiency is achieved at full power conditions. The use of Digital Control is the enable technology to implement TCM operation and keep ZVS under the whole operation range, being implemented the proposed control algorithm in a FPGA. The innovative concept to measure the inductor current has shown very appropriate behavior to implement the TCM operation. Closed loop operation has been validated under the whole operation range, providing the needed dynamic response required by the GIT.