Multi-Convertor Configurable Simulator for Dynamic Radioisotope Power Systems

This paper presents the multi-convertor configurable simulator (MCCS) that can emulate piston/displacer dynamics and power outputs of various types of sub-kW free-piston Stirling convertors developed at NASA GRC, including Technology Demonstration Convertor (TDC), Advanced Stirling Convertor (ASC), Flexure Isotope Stirling Convertor (FISC), and Sunpower Robust Stirling Convertor (SRSC). The MCCS can emulate up to two pairs of convertors, whereas state-of-the-art Stirling simulators can only emulate up to one pair. Also, the maximum power output for each convertor is designed to be approximately 1kW by using switched-mode AC power supplies. Furthermore, hardware and software changes required to switch between different types of convertors are minimized for easy conversion: 1) a hardware-in-loop (HIL) system enables a quick and easy update of linearized Stirling model parameters in software and 2) the modularized inductor boxes that represent the linear alternator enable easy replacement of the inductors. These features-easy conversion and capability of emulating up to four 1kW-convertors-will enable the validation tests of multi-convertor controller (MCC) concepts that are being developed by APL, the Dynamic Radioisotope Power System (DRPS) generator testbed, and other controller developments for current and future DRPS flight projects. Finally, as a design example, the MCCS is configured to demonstrate the FISC and outputs from the MCCS are compared with experimental data from the actual FISC.