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High Voltage Electrical Power System Architecture

Periodic Reporting for period 1 - HV-EPSA (High Voltage Electrical Power System Architecture)

Reporting period: 2016-01-01 to 2017-12-31

The main objective of the HV-EPSA project is to break the current state-of-the-art in satellite electrical & power subsystem, expand the present application domain of the classical technologies and perform a full system analysis and validation to optimize the electrical chain including the new electrical propulsion units and communication systems.

The electrical & power subsystem (EPS) is mainly devoted to provide electrical power to all the active systems of a satellite. It generates and distributes a “primary power bus” whose characteristics are optimized to the mission needs. This bus is usually generated from solar arrays and electrochemical batteries. These power sources are controlled by a Power Conditioning Unit (PCU) which delivers the power bus. EPS is a major constituent of a satellite : its cost may reach up to 30% of the total platform cost.

There is a large design variety of power buses, with voltage levels typically ranging from 28 to 100V. This state-of-the-art is well adapted to past and current needs in term of power conditioning & distribution for science and telecommunication satellites. Nevertheless, a short-term need is raising for higher operating voltages, especially for the new electrical propulsion systems and high power payloads.

Increasing the bus voltage represents a real technical challenge. During its life, the satellite has to face many “harsh” environment constraints (radiations, pressure, plasma,…) which limit the choice of high voltage electronic parts and favor destructive electrical discharges or arcs. This study will consider: solar arrays, power conditioning and distribution units (PCDU), cables and connectors, up to the main driving units for high voltage feeds: the EPCs (Electrical Power Conditioner for radio frequency amplifiers supply) and PPUs (Plasma Propulsion Unit for electric thrusters).

The benefits are tremendous: HV-EPSA is an enabler for more powerful spacecrafts, enabling a list of improvements from better embedded payload performance (e.g. more communication bandwidth) but also better servicing (faster in operational orbit), or also improved exploration missions.

This study will enable a full system analysis including units optimization and materials testing within representative environment.
The system analysis is completed, including:
- Definition of key mission scenarios and system needs
- Breakdown of those scenarios on each element of the Power subsystem in order to assess the impact of increasing the voltage in [300-600]V range
- Gather feedback from the units suppliers & analyze it in order to converge on solutions for each scenario,
- To identify the main technical issues and identify ways forward,
- To identify and detail the main tests to be performed in order to assess the feasibility of the high voltage approach on the critical elements of the power subsystem

The subystems analysis reports are completed. These reports covers:
- Battery, PCDU and EPC analysis report, by TAS-B. This report give recommandations about voltage range, EPS architecture, components to be used, insulation solutions, and test to be performed
- PPU analysis report, by SITAEL, with a specific attention paid to direct drive approach, including all consequences
- Radar Analysis report, by TAS-I, which identify benefits from High-Voltage architecture for radar application with very high load in pulsed power demand
- SADM Analysis report, by RUAG with EPFL support, which present potential future topologies for SADM under high-voltage.
- System Analysis report, by TAS-F, which gives a summary of all the subsystems reports presented above, but also a analysis of high-voltage solar array, and high-voltage wires, connectors and heaters

A first milestone was held in end of september 2016. Each analysis report conclusion was reviewed, and the consortium made decisions about mockup definition for test.

Later in October 2016, Sitael performed tests on a 20kW Hall Effect Thruster, in order to get data about plasma environment. SPIS and PicPlus simulation was done, to define the plasma density in the vicinity of Solar Array and Slip Ring Assembly, when the thruster is ON.
Between december 2016 and June 2017, all the mockups have been defined and manufactured:
- RUAG and EPFL: Two different slip-ring (one sealed and the other one with arc mitigation system)
- TAS-F, TAS-B and ONERA: Several Solar Array samples and coupons
- TAS-B: three-port convertor and distribution function for high voltage purpose.
- TAS-F and IONIX: Harness sample (cables and connectors)

This mockups have been tested in relevant environment (vacuum and plasma when applicable), unless for convertors and distributions function which have been tested in laboratory environment.

Between september and december 2017, the test results have been analyzed, and recommendation for designs and future activity have been given.

An overall High-Voltage architecture was proposed in a dedicated deliverable, giving uses cases and expected performances. Business cases and economical interest have also been studied.

Finally, the project identified and very strong interest in high voltage architecture, and proposed realistic solutions. The roadmap has identified the remaining steps to go forward in high-voltage and high-power applications.
The main impact identified up so far is the capability to dramatically enhance the coupling between the power subsystem and the propulsion subsystem for electric propulsion. This opens system architecture trade-offs that still need to be analyzed in the frame of the system analysis before testing it further in the next phases of the project.
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