Coupled Electro-Thermal and Storage Dynamics of AM0 Photovoltaic Systems Supplying Megawatt-Scale Space Data Centers: A Simulation-Based Design Study

This paper presents an exploratory simulation-based design study of a 1 MW electrical power subsystem (EPS) for a conceptual space data center in sun-synchronous low Earth orbit (SSO-LEO). The architecture integrates a 3850 m² triple-junction photovoltaic array, a 2.5 MWh battery energy storage system (BESS), and a 400 V HVDC bus supplying constant-power computing loads (CPL). The photovoltaic model is calibrated to 1.6872 MW under 25 °C AM0 reference. Periodic orbital thermal cycling (-92.6 °C to +54.1 °C, with a 144.3 K/min exit transient) reduces sunlight energy collection to 1.5972 MWh against a continuous-operation requirement of 1.6627 MWh (operating generation dropping to 1.5509 MW), yielding an orbital energy margin of -3.9% and an analytical preliminary scaled area of 4008 m² (+4.1%). Thus, while 3850 m² serves as the unadjusted standard reference baseline at 25 °C AM0, the final recommended operational flight array aperture is 4008 m² to ensure full energy closure under hot-orbit conditions. In the post-eclipse tracking window, temperature-compensated predictive MPPT (TC-PMPPT) achieves 98.46% tracking efficiency (+4.78 pp over nominal P&O at Ts = 1.0 s), demonstrating reduced step-size sensitivity across parameter sweeps rather than universal efficiency dominance, as tuned classic methods match it at fast sampling (Ts = 0.2 s). For battery state estimation, selective innovation-driven adaptation restricted to the ohmic resistance process-noise channel (Q(R0)) prevents covariance divergence, achieving zero non-finite runs across an extensive 500-seed Monte Carlo evaluation (0.00% divergence rate vs 8.80% for full-covariance fading UKF) and a high-precision nominal state-of-charge RMSE of 0.297% ± 0.039%. For bus stability, undamped constant-power loads precipitate Middlebrook instability; parallel RC damping with n ≥ 4 satisfies the 6 dB impedance margin. Large-signal 1.0 to 2.2 MW step simulations show that a transient nadir of 344.7 V (55.3 V dip) drives instantaneous load current to 6.38 kA (exceeding the 6.0 kA converter limit), but the system recovers without collapse because the damping capacitor bank supplies the transient deficit current. A 2 kHz PI controller with feedforward achieves the best dynamic recovery. In the equal-power dry mass budget, total mass is reduced by 62.8% (from 46,712 kg to 17,360 kg, saving 29,352 kg), of which 5.16 t is directly attributable to the 400 V bus and GaN conversion. Planar laminated busbars and dynamic charge-recovery hold-up bounds limit required capacitance to 32.5--35.0 mF, far below unoptimized reactive estimates.