POWER CONTROL SYSTEM FOR THE AGILE SATELLITE G. Ebale, A. Lamantia, M. La Bella Blu Electronic s.r.l. via Gallarate,150. 20151 Milano (Italy) 7th European Space Power Conference May 9- -13, 2005 13, 2005 Stresa Stresa, Italy , Italy 7th European Space Power Conference May 9
Introduction AGILE (Astrorivelatore Gamma a Immagini Leggero) main features: � detects and images photons in the 30 [MeV] ÷ 50 [GeV] and 10–40 [keV] energy bands. � excellent spatial resolution and timing capability � extremely large field of view covering 15% of the entire sky at energies above 30 [MeV] � based on an innovative design allowing the simultaneous detection of hard X-rays and gamma-rays with high imaging and timing capabilities 7th European Space Power Conference May 9 7th European Space Power Conference May 9- -13, 2005 13, 2005 Stresa Stresa, Italy , Italy 2
Additional technical data � Required orbit: Equatorial (550 km) � Total mass: 300-330 kg � Payload absorbed power: 130 W � Satellite expected orbit life: 2 years � Orbit period: 95,65 min. � Average lighting time is 60.31min. � Maximum eclipse time is 35.4 min. 7th European Space Power Conference May 9 7th European Space Power Conference May 9- -13, 2005 13, 2005 Stresa Stresa, Italy , Italy 3
PEB (Power Electronic Box) features � Solar Array Power managing � Battery reconditioning � Power distribution to the Payload � Power distribution to the OBDH � Power Distribution to the ACS, ORBCOMM, TMTC communication system � Power distribution to the battery and payload heaters � I/F ing with the OBDH (TLC/FLAG/HKM) � OVC/OVV detection on the power distribution lines 7th European Space Power Conference May 9 7th European Space Power Conference May 9- -13, 2005 13, 2005 Stresa Stresa, Italy , Italy 4
PEB specifications Unregulated main bus: 22.5÷35VDC � Maximum battery voltage: 34V � Maximun battery charge/discharge current: 12 A � Nominal battery charge/discharge current: 8 A � OBDH maximum power consumption: 30W � PAYLOAD (gamma ray detector and the associated electronics) � maximum power consumption: 130W PEB maximum power consumption: 70W � Other satellite loads: 100W � � momentum wheel � magnetic torques � magnetometers � battery and payload heaters � Orbcomm � TMTC communication system 7th European Space Power Conference May 9 7th European Space Power Conference May 9- -13, 2005 13, 2005 Stresa Stresa, Italy , Italy 5
POWER SYSTEM ARCHITECTURE 7th European Space Power Conference May 9 7th European Space Power Conference May 9- -13, 2005 13, 2005 Stresa Stresa, Italy , Italy 6
Solar array features: � Maximum dimensions: T Imp Vmp Pmax � 2080 mm (width) [°C] [A] [V] [W] � 1050 mm (length) � 26 mm (thickness) BOL @ -90 16,084 37,41 601,68 � Electrical structure: BOL @ 90 18,285 23,8 435,39 � 14 electrical sections per panel. EOL @ -90 15,942 36,43 580,79 � 6 sections type with 5 strings EOL @ 90 17,455 23,19 404,8 � 8 sections type with 1 string. � Strings formed with 13 solar cells. 7th European Space Power Conference May 9 7th European Space Power Conference May 9- -13, 2005 13, 2005 Stresa Stresa, Italy , Italy 7
Solar array curves: BOL EOL 7th European Space Power Conference May 9 7th European Space Power Conference May 9- -13, 2005 13, 2005 Stresa Stresa, Italy , Italy 8
Battery features: � Battery type: 11 NiH2 cells in series � Battery capacity: 10 °C is 12 Ah (330 Wh) � Battery nominal voltage: 27.5 V � Battery maximum voltage: 34V � Nominal Charge current: from 6 to 8 A � Maximum Charge/discharge current: 12 A � Average power that the battery shall supply in the eclipse periods is: 195 W � Peak power is approximately: 230 W . 7th European Space Power Conference May 9 7th European Space Power Conference May 9- -13, 2005 13, 2005 Stresa Stresa, Italy , Italy 9
Battery reconditioning � PS board � S3R philosophy � Internal logic to manage the redundancy of the CR boards � Solar Array current and voltage monitor � Internal fold back circuits against auxiliary power supply short circuit � Latch up protection 7th European Space Power Conference May 9 7th European Space Power Conference May 9- -13, 2005 13, 2005 Stresa Stresa, Italy , Italy 10
� CR board � Boost topology � Internal logic to manage the MPPT function � Input, output, battery current monitor � Battery voltage monitor � Battery OVV, OVC, OVD detection � Internal fold back circuits against auxiliary power supply short circuit � Latch up protection 7th European Space Power Conference May 9 7th European Space Power Conference May 9- -13, 2005 13, 2005 Stresa Stresa, Italy , Italy 11
Redundancy philosophy Two redundant Power Switches (PSM and PSR) control two redundant Charge � Regulators (CRM and CRR) providing the Solar Array (SA) power to the battery and to the main bus. CRM and CRR can manage about 8 A each to charge the battery, if the battery � needs more current they can work in parallel mode to supply about 12 A 7th European Space Power Conference May 9 7th European Space Power Conference May 9- -13, 2005 13, 2005 Stresa Stresa, Italy , Italy 12
PEB Operational Modes Pos 1: Psa > Pbat+ Pmb, the � system works in S3R domain controlling the total current within the battery. Pos 2: Psa < Pmb+Pbat, a � Maximum Power Point Tracking (MPPT) mode controls the battery charging current. Pos 3: Psa <Pmb, the current � delivered to the node ‘battery + main bus’ is controlled at 8A in the S3R domain Pos 4: Psa@Vbat<Pbat,the � Maximum Power Point Tracking (MPPT) mode is utilised again to control the current delivered to the node “battery+main bus” (Fig. 3 pos 4). 7th European Space Power Conference May 9 7th European Space Power Conference May 9- -13, 2005 13, 2005 Stresa Stresa, Italy , Italy 13
Error signal domain � S3R: 6 high current section with a very large hysteresis for the switch on threshold and switch off threshold (10V). � CR mode with maximum power point tracking 7th European Space Power Conference May 9 7th European Space Power Conference May 9- -13, 2005 13, 2005 Stresa Stresa, Italy , Italy 14
Error signal response to load variation 0,5 A section Main bus variation 200mV/div Error signal variation load variation 1A/div 7th European Space Power Conference May 9 7th European Space Power Conference May 9- -13, 2005 13, 2005 Stresa Stresa, Italy , Italy 15
Error signal response to load variation 2,5 A section Main bus variation 500mV/div Error signal variation load variation 2A/div 7th European Space Power Conference May 9 7th European Space Power Conference May 9- -13, 2005 13, 2005 Stresa Stresa, Italy , Italy 16
Error signal response to load variation CR Main bus variation 200mV/div load variation 2A/div 7th European Space Power Conference May 9 7th European Space Power Conference May 9- -13, 2005 13, 2005 Stresa Stresa, Italy , Italy 17
Power Distribution In order to supply power to the satellite different distribution boards directly connected to the unregulated bus have been foreseen � DC/DC board: � supplies internal and external auxiliary voltages: � ±15V � 12V isolated � 5V � main and redundant electrically and thermally separated lines � Undervoltage and overvoltage protection � Current monitoring 7th European Space Power Conference May 9 7th European Space Power Conference May 9- -13, 2005 13, 2005 Stresa Stresa, Italy , Italy 18
� PR board � Connected to the battery bus through the separation switches by redundant and fault tolerant linear regulators in order to perform basic operations if internal power supply is not available � connects the internal DC/DC converters to the power bus by latching relays and performs a switch over from nominal to redundant DC/DC converter branches in the case of a failure detection (input over-current, output under or over voltage). � provides power distribution to the OBDH main and redundant protected power lines � performs switching and OR-ing of the PEB internal supply lines. � Fold back protection circuits for the auxiliary power supply 7th European Space Power Conference May 9 7th European Space Power Conference May 9- -13, 2005 13, 2005 Stresa Stresa, Italy , Italy 19
� PD board � Supply power to the external loads through dedicated power lines � MAIN and the RED branches designed to guarantee separation between the two branches from an electrical and thermal point of view. � Primary power lines distributed from the PEB individually protected against short circuit through series n-channel power MOS and dedicated current sensing circuits. 7th European Space Power Conference May 9 7th European Space Power Conference May 9- -13, 2005 13, 2005 Stresa Stresa, Italy , Italy 20
� Cross-trapping philosophy for the vital loads nominal and redundant equipment (receivers and transmitters) � fold-back current limiters for the auxiliary supply 7th European Space Power Conference May 9 7th European Space Power Conference May 9- -13, 2005 13, 2005 Stresa Stresa, Italy , Italy 21
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