Parallel Control of an Electric Power and Propulsion System for an Interplanetary Spacecraft

This paper proposes an electrical generation scheme, for interplanetary missions, utilizing an MW-scale two-excitation generator (TEG), a rectifier, and an isolated parallel output DC-DC converter (iPOD). The TEG consists of a 9-phase stator configuration with two rotor segments: a wound field (WF) rotor and a permanent magnet (PM) rotor. This configuration allows for a quick response to power variations. By adjusting the injected current to the WF segment, the generator’s total back electromotive force (emf) can be varied, subsequently affecting the output power. This flexibility enables a wide power range for the thruster without requiring modifications to the mechanical rotation speed. The TRG’s output is rectified using a passive rectifier and then connected to the iDC2, which provides two outputs. The primary output connects to a high-voltage DC bus, supplying power to the thruster, while the auxiliary output feeds the low-voltage DC (LVDC) bus for the spacecraft’s power system. The auxiliary output of the converter provides an additional degree of freedom to support power changes in the thruster since the WF segment’s range is limited. Not only iPOD structure allow enhanced control over thruster power but also enables the NEP system to act as a backup power source for the spacecraft’s electrical systems, complementing primary sources like batteries and solar panels. iPOD converts the passive rectifier output through a series switch and a high-frequency transformer that isolates the propulsion system from the power system. This configuration offers control over the power delivered to the thruster, while the auxiliary output regulates power for the LVDC link.