Power System Design & Analysis
SpaceTech personnel have been responsible for the design, analysis and procurement of electrical power systems for many space missions including venerable programs like Champ (GFZ-DLR), Grace (NASA-DLR), TerraSAR-X (DLR-EADS), HTV (JAXA).
Moreover, SpaceTech has successfully provided engineering consultancy support world-wide to customers like the Taiwanese space agency NSPO, the Korean space agency KARI and the German national space program AsteroidFinder. SpaceTech is developing solar generators (GökTürk-2, Formosat-5, Sentinel-5 Precursor) and procuring other power hardware for system customers.
This accumulated experience and proficiency allows SpaceTech to offer consultancy and support services for the following power system engineering activities:
- Selection of overall power architectures suitable for specific missions
- Selection of suitable charge and solar array regulator topologies
- Selection of suitable solar generator and battery technologies
- Sizing of on-board electrical power resources (solar generator, battery)
- Analysis of power system capabilities and margins
- Optimization of power system capabilities (solar array sizing, orientation, charge control algorithms)
- Procurement support for on-board electrical power equipment
SpaceTech has developed a spacecraft power simulation and analysis tool allowing single-orbit and multiple orbit simulation of all major power system characteristics on-board a satellite orbiting the Earth on a circular orbit. The tool is implemented in a modular way in order to allow easy adaptation to different mission types and characteristics.
The following main modules are available:
- Orbit and Geometry Module: This module allows the input of the basic orbit parameters and the orientation of solar arrays on the spacecraft. The outputs of this module are the related orbit periods, including sun and eclipse phase discrimination, and, under consideration of the activated manoeuvre in the manoeuvre module, the incident angle of the sun on the different solar array panels as well as the Earth view factor of each panel.
- Spacecraft Manoeuvre Module: This module allows the definition and selection of different sets of manoeuvres over the orbit.
- Thermal Module: This module allows the input of the thermal environment and the thermal characteristics of the solar array cell surface. The output of the module is the cell surface temperature profile over one characteristic orbit.
- Power Consumption Module: This module allows the definition and selection of different sets of power consumption profiles over the orbit.
- Battery Module: This module allows the input of the battery main characteristics as they are used by the Power Analysis Module. The characteristics are dependent on the life time situation.
- Solar Array Module: This module allows the input of the solar cell main characteristics as they are used by the Power Analysis Module. The characteristics are dependent on the life time situation.
- Power Analysis Module: As input this module allows the allocation of solar strings to the solar panels. The output of this module are the generated electrical power at solar array and bus level, the determination of the different on-board currents (discharge, charge, charge excess), the profiling of the battery state-of-charge and the bus/battery voltage. In addition the respective efficiencies of the solar cells will be tracked and fed-back into the thermal model (thermal alpha correction). As the power generation is dependent on the topology of the bus and charge control, different modules are available reflecting the possible combinations of bus topology (non-regulated, regulated) and regulator type (Sequential Serial Shunt, Maximum Power Point Tracker).
- PCDU SAR Dissipation Module: This module allows as input the cross-connection of solar generator strings with the PCDU regulator stages. In accordance with status of switches (Shunt) or the operating point (MPPT) as well as the acting charge currents, the load dependent dissipation of the solar array regulator (SAR) will be determined together with the respective average values over the sun phase and the entire orbit period.
The results of each simulation will be provided in a simulation summary sheet:
In a different mode the tool allows to define a multiple sequence of orbits, each with different spacecraft manoeuvre scenarios and power consumption profiles. The final status of each orbit will be used as input for the respectively consecutive orbit. This simulation mode allows to simulate mission operation sequences and determine the stability of the power system beyond one singulary orbit.
The simulation results will be presented in terms of timelined profiles for
- Solar Panel Projections
- Solar Panel Temperatures
- Required and Generated Power
- Battery State-of-Charge
- Battery Voltage
- Battery Charge/Discharge and Excess Currents
- PCDU SAR Dissipation
The core modules and algortithms of the simulation tool come into application with the overall mission simulator SPADES that has been developed by SpaceTech, as well.