European Space Agency

Investigation into the advantages of Maximum Power Point Tracking for GEO Telecommunications Satellites


This project studied the possibility of improvement of the classical regulated bus by considering the use of a classical regulated topology whose voltage is regulated to maximum power point of the solar array. The project has consisted of two phases: the first one considered whether the basic idea improves the classical regulated bus by using ad hoc developed models; the second one, after positive conclusions of the first, tested the actual behaviour of a low power mock-up of the proposed idea.

The objective was to perform an end-to-end study from the power system to the payload, using the latest ideas and technologies, in order to compare a Maximum Power Point (MPP) and classic fully-regulated maximum current Busses for future GEO Telecommunications spacecraft. The optimization of the end-to-end system shall be taken as meaning the optimisation of the overall solar array power processing and power distribution system up to the TWTAs such as to minimise the cost per TWTA channel per year.


The Phase I of the study consisted of a search and high level comparison of the different candidates to implement an optimum space power system for GEO telecommunication applications including topologies with MPP and without MPP operation and battery above and below the power bus.

The objective of Phase II of the project was:

  • To define the specifications of a mock up system;
  • To study the feasibility of the identified design for space operations;
  • To implement a system test bed that will provide significant data to ensure that the S3MPPR system performs in a reliable manner.


The study has shown, that the addition of a MPPT subsystem to a S3R regulated bus can be performed on an elegant breadboard. FMECA, WCA and PSA analyses have been performed on the Elegant Breadboard Schematics. Non-Compliances and critical failures have been identified, appointing the primary areas where improvement is needed in case of future development. Whereas currently the Elegant Breadboard does not yet perform fully to ECSS design standards, the design concept for which the benefits have been investigated is shown to be feasible.

When implemented in a high power telecommunications satellite, a certain energy gain over the first half of the mission lifetime may be expected. Other system level impacts, such as EMC interaction and bus voltage variations, that may occur due to the specific electrical behaviour of this MPPT, need to be further investigated.


A system test bed that will provide significant data to ensure that the S3RMPPR system performs in a reliable manner and that a space implementation of it may fulfil ECSS-E-20A and ECSS-Q-60-11A. To do that a system specification was defined for a scaled down model of the telecommunications satellite studied in Phase I that may be readily implemented and studied in a laboratory set-up. Further, it was shown by the contractor that the S3RMPPR can be implemented to the ECSS specifications.

The contractor made a full electrical design of a system that could work as S3R regulated bus and as S3RMPPR bus including redundancies. The design included a Worst Case Analysis at System Level for the S3RMPPR, a functional FMECA of the MPPT at subsystem and component level and a Part Stress Analysis for the MPPT Subsystem that made it clear that the proposed topology may qualify for space flight. The final design included the complete schematic files and Bill of Materials for the implementation of the laboratory test bench.

The final test bench to implement was based on the design developed but not including the redundancies and protection elements that they were not part of the study. Nevertheless, dummy protections were included when they affected the efficiency or performances of the system.


Phase 1 concerns the study of an optimised Telecommunications end-to-end system, from Solar Array to Payload. Phase 2 concerns the Design, Building and Testing of a scaled-down model of the proposed system.

Current status

The study has been completed.

Status date

Wednesday, July 10, 2019 - 08:07