PCDU LEO Telecom

Objectives

The goal of the project is to design, develop and qualify a Power Conditioning and Distribution Unit (PCDU) dedicated to the telecom market based on a constellation of satellites in Low Earth Orbit (LEO). One Electrical Model (EM), one Electrical Qualification Model and on test equipment (EGSE) will be manufactured in the frame of the contract.

The target industrial project is the GlobalStar second constellation of satellites.


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Challenges

  • To improve MPPT boost converters topologies,
  • To validate new way to perform module coating,
  • To validate simplified battery management and failure recovery concepts.

Benefits

The contract has allowed to reduce EPS costs by conditioning architecture optimization (w.r.t. SA / PCDU sizing, design and manufacturing constraints), by simplifying battery management and failure recovery concept, by selection of fuse distribution and by improvement of PCDU testability and manufacturing rules. This will allowed to propose production rate compatible with the telecom constellation need and a attractive production cost.

Features


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The PCDU is based on the following architecture.

Primary bus
The main functions of the PCDU are to generate and distribute a single unregulated bus comprised between 23V and 38V providing the necessary power (up to 1.8 kW) to the satellite for its specific mission.

SA interface
SA panels are divided in 18 SA sections, each section interfaces with a non-reliable boost converter. These converters are commanded by two (one per wing) centralized MPPT circuits (that fix the adequate SA voltage in order to obtain the maximum SA power during battery charging) and by one Battery management circuits (that can reduce the SA voltage to limit the battery charge rate at the selected value or if the battery reaches its full charge voltage). SA conditioning circuits operate in cold redundancy.

Battery interface
PCDU interfaces with one Li-Ion battery (9 cells packages in series) ensuring charge limitation and tapering (charge current limit and end-ofcharge voltage values are fixed by OBPE). PCDU also provides under-voltage alarm; cells balancing without autonomy (cells and “three cells” groups monitoring & shunt activation capability) and cells by-pass functions. Finally a Battery isolation based on MOSFETS for Assembly, Integration and Tests (AIT) purpose is also implemented together with dedicated umbilical interfaces.

PL/PF users & heaters distribution
PCDU provides 42 PL/PF lines protected by fuses from which 4 (“Reaction Wheel” lines) can be ON/OFF switched by MosFet inside PCDU. PCDU distributes also power to 16 PL heaters lines, 44 PF heater lines and 4 latch valve lines. PL heater lines are not switchable and are protected by fuse. PF heater lines and latch valve lines are individually switch-able (return line) and are splitted into groups which provides, in case of short failure of individual switch, a second ON/OFF level (performed by a switch in the hot line) protected by fuse.

PYRO actuation
PCDU provides interfaces to 8N+8R EED lines via 3 safety barriers.

Plan

Due to the discrepancy between the execution of the present contract and the real GlobalStar2 industrial advancement, a waiver with regard to the standard flow has been accepted. PDR and CDR have been performed after the end of the manufacturing of the EM, EQM and EGSE.

During the PDR, the design and the resulting analysis have been reviewed and some breadboard test results have been reviewed. During CDR, the design and analyses updated at the end of the development phase (which has led to the release of the manufacturing) and DM and EM electrical test results have been reviewed. During FR, EQM electrical test results have been reviewed.

Current status

The project is now in the end phase. PDR, CDR and FR have been held successfully and the corresponding data packages have been delivered. EM, EQM and EGSE have been manufactured and the test results have been reviewed.

In the frame of this ARTES-4 contract, ESA was involved in the technical assessment of the design, development and qualification of a Power Conditioning and Distribution Unit for commercial telecommunication satellite missions.

During this contract TAS-ETCA has presented a design using a wire link fuse in a hybrid. This design has been carefully reviewed by ESA and found not meet the requirements of the PA & Safety Department.

Moreover several design features concerning the electrical architecture have also been highlighted by the Agency who expressed the risks associated to the proposed design and the non compliances to the Electric and Electronic ECSS standard.

Thales Alenia Space France (first customer of the developed product) has noted the risks identified during the reviews and has indicated that the product design satisfies the need and requirements for commercial telecommunication satellite missions that are targeted with this product.

ESA considered that the design and qualification of the PCDU are consequently under the sole responsibility of Thales Alenia Space France.

Contacts

Status date

Tuesday, January 20, 2009 - 12:07