# Presentation: 143764

## Section 17

_***Section 17***_
***Power***

*** ******. . . Allan Billings***
*EO-1 Power Lead, Swales Aerospace, Inc.*

## Power System PSR Outline

***Power System PSR Outline***

***EO-1 Power System Description***
***Power System Distribution Block Diagram***
***Requirements/Characteristics***
***Analysis/Test Data***
***Test and Verification Matrix***
***Peer Reviews***
***Summary of PSR RFAs***
***Redbook Candidate***
***Action Item Status***
***Power System Statement of Readiness***
***Special Topic 16A--Battery CHG. Algorithm***
***Critical Design Review ---RFA number 8,9***

## EO-1 Power System Description
Unregulated Power Bus (+28Vdc +/- 6 Vdc) Consisting Of:

***EO-1 Power System Description***
*Unregulated Power Bus (+28Vdc +/- 6 Vdc) Consisting Of:*

***PSE***
***Digital, Shunt Regulated, Direct Energy Transfer Power System (Flight Heritage),7 Digitally Switched (BSFR) Solar Array (segment) Shunts (gross power), Two unswitched BSFR and one unswitched GaAs segments.***
***	******Two BSFR Solar Array Segments used in PWM circuit (Boost Converter) for Fine Control.***
***PSE Contains The Following 6 Printed Wiring Boards***
*PSE RSN ---Command, Telemetry and Control for PSE and Interface to Spacecraft on 1773 BUS.*
* **LVPC Provides (Current Limited) Switched (1A) and Unswitched 28V Power to Spacecraft as Well as 5V + - 15V Power to PSE.*
*Output Module 1 and 2 Provides (Current Limited 15A) Switched and Unswitched*
* **Power to Spacecraft.*
*Solar Array Module Provides for Shunting the Solar Array and Charging the Battery *
*Battery Module Provides for Spacecraft and GSE Interface as well as Battery Telemetry*
***Battery***
***Single, Super Nickel Cadmium, 50AHr Battery (Flight Heritage)***
***Solar Array***
***One Deployable Solar Array, 750W BOL at 37V Peak Power Pt,  At 60C, Sun Intensity =.97***
***For further descriptions of the Solar Array see Special Topic on Solar Array.***

## PSE Power Distribution

## PSE Requirements / Characteristics

***PSE Requirements / Characteristics***

***Supports 300 W orbital average power in LEO for a 1-year single string mission .***
***Maintenance of  bus voltage within 28 ±6 V***
***Bus transient < 3 V***
***Bus noise and ripple < 0.5 V***
***Hardware over voltage protection.***
***Compatibility with 50 Ah super NiCd******  ******battery***
***Top level switching, distribution and over-current protection of the S/C primary power.***

***Design can support 400 watts.  Used in MIDEX MAP mission.***
***The Bus is Directly Derived From the Battery Voltage. The Battery Charge Current  and  Bus Power is Derived from a Digital Shunt Regulator with a PWM******	******Boost Regulator for Fine Control.***
***Shunts are sequentially enabled by Hardware when Bus Voltage Exceeds 34.5V***
***Original  MAP Design Modified to Accommodate NiCd Battery. Map used Nickel Hydrogen Battery***
***The LVPC and Two Output Modules are provided for Current Limited Switched and Unswitched Distributed Spacecraft Power.***

***Requirements***

***Compliance / Characteristics***

## Requirements

***T-0 Umbilical power interfaces for ground power and pre-launch operations.***
***PSE mass less than 16 kg.***
***Telemetry signal  processing:***
***Battery current, temperature,  voltage and differential  voltage, ***
***bus voltage, current and temperature,  S/A panel temp.***
***Chassis current, PWM control & status, BSOC, desired current for V/T control***
***desired V for V/T level, LVPC  and load current,  SSPC status & trip level***
***Battery relay status, watch dog reset, reset command counter, etc.***
***Software control of S/A and battery subsystem.***
***Local  power conversion and filtering.***
***Radiation:  > 15 krad (Total dose, MeV of > 35 krad for SEU)***

***1773 interface is used in design.***
***T-0 Umbilical power interfaces for ground power and pre-launch operations are provided.***
***PSE actual weight = 14.8 kg***
***All  the required telemetry is processed by the PSE  RSN which contains A/D, D/A, command & data interface to S/C.***
***Charge current & S/A segments switching are controlled by  flight S/W.***
***LVPC module provides the  local power conversion  and filtering.***
***Ray trace analysis demonstrated PSE meets these requirements***

***Requirements***

***Compliance / Characteristics***

## Power System Requirements / Characteristics

***Power System Requirements / Characteristics***

***Power System Topology***
***Selected shunt regulator direct energy transfer (DET) topology as meeting all system requirements.***
***Used MAP PSE (Power System Electronics) Design---PSE implemented shunt regulator DET topology.***
*MAP PSE design was mature and included software. This approach was designed to enhance reliability and reduce engineering time. Both goals were achieved although significant software changes were made in the design. These were made with close cooperation with the MAP team.*
***Solar Array***
***One deployed wing with three solar panels with BSFR solar cells (14.8% EFF). Additional GaAs Strings added to outer panel to accommodate  increased power requirements for Hyperion. Expected EOL power of 633W at 72C at 33.5V > 10.7%  power margin.***
***One wing, two panel design with all GaAs cells(SJ) considered for total array but not selected due to cost.***
***Battery***
***Super NiCd 50Ahr --One flight battery and one workhorse battery received from TRMM program. Nominal depth of discharge on station is 13%. Worst case depth of discharge at sun acquisition = 30%***
***Battery qualified for TRMM and XTE. Battery GSE/GFE supplied with battery.***

## Power Balance Analysis

***Corrected TB Load Power Data (Orbit Average)***
***294 Watts Science Hot TB***
***298 Watts Standby Cold TB***
***196 Watts Safehold Cold TB***
***Assumptions Made in Analysis***
***Load power drain is orbit averaged value in eclipse and sunlight. ***
***Used  BSFR cell data provided by TECSTAR in the end item data package including the end of life degradation. However a 5 degree pointing error was added. ***
***A math model in Mathcad for the solar array was created. A fixed 1.4A for the GaAs strings was added  to the V/I curves for the BSFR cells. The 1.4A represents the end of life value at the array voltage of 33.5V at 72C.***
***An array (input to PSE) operating point during charge of 33.5V was used ***
***72 degrees is expected to be Solar Array worst case temperature for normal array (no debonding).***

## Power Balance Analysis

_***Solar Array Has PWR Margin Every Orbit---Satisfies CDR RFA 4.09***_

## Power Balance Analysis

***Predicted EOL (1.8 Years)  Solar Array Power Input to PSE***

***Power Balance Analysis***

## Power Balance Analysis

## Power Balance Analysis

***Power Balance Analysis***

## Power Balance Analysis

***Power Balance Analysis***

## Power Balance Test Data

***Power Balance Test Data***

***Power Balance From Launch to Sun Acquisition   (L + 184 minutes). From TV Test Data, Using I&T Battery (not reconditioned prior to TV)***

## Stability Analysis

***Stability Analysis***

***Stability Analysis/Tests***
***Swales performed stability analysis of Power System using MATHCAD and MATLAB by developing a math model. MAP results agreed with Swales. See Swales Technical Report: ***
***	******To Mark Perry, 07/23/99***
***	******Subject: EO1 PSE Software/Hardware Simulation Model, Analysis and Results***
***MAP performed stability analysis of the Power System using a spice and MATLAB model. Model results agreed with measured ETU values of worst case gain margin = - 6.14 dB and worst case phase margin = 67 degrees. ***

## PSE Box Level Proto-Flight Test Flow

**Vibration Test**

**Thermal Test**

_***Rework for Op-amp Repair and 1773 Replacement***_
***Vibration - 3 axis, .04g2/Hz***
***Thermal - 4 cycles, -15oC to +55oC, turn on @-20o & +60o***

_***Rework for 1773 Repair***_
***Vibration - 1 axis, .04g2/Hz***
***Thermal - 4 cycles, -15oC to +55oC, turn on @-20o & +60o***

_***Anomaly During Hot Cycle***_
***Could not command SSPC Corrected  by adding wait state in software***

**Performance Test**

***3 Axis***
***0.16 g******2******/Hz***
***Functional Test Between Axis***
***Aliveness During Vibration***

***4 Cycles***
***+60°C hot turn on***
***+55°C soak, Thermal Performance Test***
***-20°C cold turn on***
***-15°C soak, Thermal Performance Test***

## PSE Subsystem Level Testing

***Performed Load Step Testing ***
***Verified Stability and Time (Software/Hardware) it takes to correct for changes in loads***
***CPT tests of entire S/C characterized over several orbits at different VT levels***
***Further Testing of the PSE ***
_***Tested FDC  functions:***_***  Battery Temperature FDC, Battery Voltage FDC, Battery Differential Voltage FDC***
_***Test Battery PRT:***_***  Battery temperature sensors, both primary (PRT) and backup RT were tested including failure modes.***
_***Partial Power tests:***_***  Tested system with simulated solar array string losses as well as the solar array at EOL and in Eclipse***
***Hardware/Software Model of PSE***
***Used to validate tests or changes in PSE code before actual code is tested in the PSE ***
***Model Validated Through Correlation of Multiple Test Results***

***PSE Subsystem Level Testing***

## Verification Matrix

## Accumulated Power On Time for EO-1 S/C & Components

## Description of Tests in Verification Matrix -- PSE

***Description of Tests in Verification Matrix -- PSE***
***	******	***

***Qualification by Similarity***
***Static Load Test and EMC/EMI Test Performed on MAP PSE--Passed***
***Verification by Analysis***
***Venting/Pressure Profile--Venting put into PSE chassis. ***
***Radiation-- Ray Trace Analysis By Litton showed Compliance to 15KRAD Total Dose***
***Verification by Test***
***Random Vibration --- See previous slide***
***Thermal Cycles ---See previous slide***
***Interface Verification ----Passed***
***Functional--Passed***
***Weight--- Actual Tested weight = 14.8 kg    Requirement  = 16 kg***

***PSE Verified Through Qualification by Similarity,  Verification by Analysis and Successful  Verification by Test***

## Description of Tests in Verification Matrix -- Battery

***Description of Tests in Verification Matrix -- Battery***
***	******	***

***Qualification BY Similarity***
***Venting/Pressure Profile--Passed***
***Verification by Analysis***
***Life Test--Passed***
***Static Load--Passed***
***Verification by Test***
***Random Vibration --Passed***
***Thermal Vacuum --Passed***
***Interface Verification ----Passed***
***Functional--Passed***
***Weight--- Actual Tested weight = 59Kg -- Passed ***

## Test Results:  Calibration / Characterization

***Test Results:  Calibration / Characterization***

***A trending procedure was run in the background throughout TB/TV capturing the critical Power System telemetry points every 15 sec.***
***The bus voltage, battery voltage, battery current, battery temperature, solar array module current, chassis current, output module #1 current, and output module #2 current  were sampled every 15 sec and compared to the GSE/Umbilical telemetry.***
***All PSE telemetry was in agreement with GSE/Umbilical telemetry to within acceptable limits and the error was not changing with TV temperature.***
***The PSE was fully characterized in all modes of operation:  full charge/current limited charge, V/T clamped charge, and trickle charge.***

## Peer Review 

***Peer Review ***

***PSE***
***Peer reviews were held on the design of all PSE hardware under the MAP program***
***Peer Reviews on EO-1 were held between Swales, Litton and NASA in regard to stability issues on the PWM circuit and the power system in general.***
***Extensive software peer reviews were conducted on EO-1 between Swales, NASA and Litton.***
***Solar Array***
***A S/A CDR and Delta CDR ( Hyperion Modification) was conducted with NASA, Swales and Tecstar***
***LAPSS Test Performed at Goddard on ***
***Battery ***
***The battery has flight heritage and was qualified on the MAP program and the TRMM program***

## Summary of Power PSR RFAs

***Summary of Power PSR RFAs***

***RFA #14.02 ******	******Provide Subsystem Environmental Reports---Complete***
***RFA #14.04******	******Verify Proper Response to all Software Commands in the ******	******	******	******PSE.  Complete.***
***RFA #14.05******	******Review Strip Chart Data for Effects During Shock, Vibration ******	******	******and Acoustic Testing. Complete, Reviewed and no effects ******	******	******	******observed.***
***RFA #14.06******	******Determine Normal Spacecraft Load During Science Hot TB,******	******	******Standby Cold TB, and Safehold CTB. Complete.***
***RFA #14.07******	******Determine The Energy Balance for Various Spacecraft ******	******	******	******Modes. Complete--We have positive energy balance in all ******	******	******	******normal spacecraft modes.***
***RFA #14.08******	******Is the PSE RSN Affected by A/D Converete Stuck Bits? No--******	******	******Based on thorough review of spacecraft telemetry.***
***RFA #14.09******	******Determine HSSR Load Susceptibility to Oscillation. Not ******	******	******	******susceptible since all the loads are resistive.***
***RFA #14.12******	******Develop Trending Procedures for Flight Data Processing. --In Process,***
***	******	******expect completion in two weeks.******	******	***

## Redbook Item

***Redbook Item***

***PR- 837-20- 1:  The LVPC total current telemetry PLVPCLDI2 reported a current that exceeded the range of the A/D. The A/D reported an FF (Max Value) for one sample only. The LVPC current trip was not activated and the Umbilical telemetry provided no indication of an over current. The following areas were investigated:***
***FEDS-- The FEDS expert investigated this anomaly to determine if the FEDS system could have caused the telemetry for PLVPCLDI2 to incorrectly report an FF. The FEDS expert indicated that as a result of his investigation, he believes that the FEDS system was not responsible for causing this anomaly. He indicated that the FF was generated in the spacecraft.***
***RSN--- The RSN software expert was asked to determine if the FF reported in the telemetry could be the result of some RSN software/hardware malfunction. The RSN expert indicated that he had no explanation as to why the telemetry reported FF.***
***Hardware-- It is possible to get a true single overcurrent pulse that would generate an FF in the A/D converter and not trip the LVPC while at the same time provide no indication in the Umbilical data. This could happen if the pulse were narrow in time. The A/D has a conversion time of only 25uS and pulses this small could cause the above problem. However there are numerous reasons why this is highly unlikely and are treated in the response to the PR.***
***Conclusion: There is no acceptable answer as to why the PLVPCLDI2 telemetry reported an FF***

## Critical PRs

***Critical PRs***

*** ******PR 682-20-9: Commanded VT levels are only displayed in 0.5 increments even if commanded in other increments. ***
***Resolution--Only command VT levels in 0.5 increments. Place notice in constraints manual.***
*** ******PR 673-40-2 ---Could not separately turn off OM #2 RWA and SADE services without disabling the FDC for the entire OM. ***
*** ******Resolution Fixed in software version 7.8 WOA -719. We can now enable the FDC individually for each service in both output modules.***
*** ******PR 678-20-1--- The Hyperion Heater off command is swapped with the Hyperion Off command.***
***Resolution---This was a PSE software problem and was corrected in version 7.80 of the PSE software load.***
*** ******PR 683-20-3---Cold Resets or warm resets of the PSE RSN cause some zeroized data to be transmitted after the reset. This lasts for about one minute.***
*** ******Resolution---Use as is and place alert in Constraints Manual. The zeroized data does not last long enough to initiate any FDC’s or TSM’s.***
*** ******PR 684-20-1 -- Same as PR 683-20-3 except that in addition the Power ASIST station timing was not in synchronization with the master clock. It was 2 minutes slow. ***
*** ******Resolution-- The resolution was the same as PR 683-20-3 for the zeroized data. Use as is and place an alert in the Constraints Manual. The Power ASIST station timing was corrected in the FEDS system.***

## Action Item Status

***Action Item Status***

***RFAs -- Closed except for PSR RFA #14.12***
***PRs and PARs -- Closed***
***One Redbook Candidate PR - 837-20-1***
***Statement of Readiness & Residual Risks***
***The Power System is Ready for Launch Processing.***
***All required test procedures are complete and released.***
***The Solar Array has successfully passed a final inspection.***
***The Battery handling plan is complete and released.***
***The PSE has been thoroughly tested and is ready for launch.  ***

## Special Topic:

***Battery Charging Control Algorithm***

## Special Topic 16A:  Battery Charging Algorithm 

***Object---The object of the battery charging algorithm is to safely return the battery to 100% state of charge by the end of the orbital day.***
*** ******Maximum Charge Rate --- During orbital day the algorithm will attempt to charge the battery at a ground commandable maximum rate (default = 18A).***
***VT Level --- A VT level of 5 has been selected as the preferred VT on orbit (default VT = 4). When the battery voltage is equal to the temperature corrected VT voltage the battery charge current is reduced to maintain the battery voltage at the VT voltage curve level. One of 8 separate NASA VT curves can be selected by ground command.***
***Amp Hour Integrator--- The algorithm computes amp*hours charging the battery and amp*hours discharging the battery. The amount of amp hours that must be returned to the battery to recover the amp*hours lost during discharge is greater by the C/D ratio.  The default C/D ratio is 1.05 and is adjustable by ground command. When 100% state of charge is obtained, the battery charge current is switched to Trickle Current. ***
***Trickle Current---When the battery state of charge is 100% the algorithm changes the battery current to the trickle value. The default value is .5A and is adjustable by ground command.***
***Verified in PSE FSW Build 8.00 Load and Test. Closed 3/7/00***

## CDR RFA #14.08, #14.09 

***RFA 14.08:  Perform worst case analysis on primary power circuits at worst case loads.***
***Worst case analysis performed on Output Modules with worst case loads on output services. Load currents are below the maximum safe value for the SSPC switches.***
***RFA 14.09:  Attempt to reduce solar array size and thereby reduce cost.***
***There were unacceptable risks in reducing solar array size and it was not reduced. This response was previously provided in much greater detail.  This issue is resolved with no residual risk.***

***CDR RFA #14.08, #14.09 ***