DOCUMENT NAME ELECTRICAL POWER

SUBSYSTEM

DOCUMENT NO. 04

DATE MODIFIED 11/03/2024

Namra Mazhar 210401015

Muhammad Arslan Haider 210401027

Muhammad Raza Madni 210401034

Abd-Ur-Rab 210401043
PREPARED BY
Faiza Jamil 210401051

Muhammad Shehryar Ali 210401062

Raza Hussain 210401072

APPROVED BY SIGNATURE: ______________________________

 Dept. Electrical Engineering
Course SE - 608440
Date 11/03/2024
Project: ICUBE-CSAT
Page: 2

LIST OF MODIFICATIONS

Section/ Pages
Date Issue Modified by Reason for change
Affected
 Dept. Electrical Engineering
Course SE - 608440
Date 11/03/2024
Project: ICUBE-CSAT
Page: 3

LIST OF ABBREVIATIONS

ADCS Attitude Determination and Control Systems

EPS Electrical Power Subsystem

OBC On Board Computer

 Dept. Electrical Engineering
Course SE - 608440
Date 11/03/2024
Project: ICUBE-CSAT
Page: 4

LIST OF FIGURES

Buck-Boost Convertor Using 555 Timer

IC…………………………………………………………...

Voltage Regulator Using IC……………………………………………………………………………

Over Protection Circuit……………………………………………………………………………….

Variable Voltage Regulators………………………………………………………………………….

Battery Health Monitoring System……………………………………………………………………

Block Diagram of
EPS…………………………………………………………………………………..
 Dept. Electrical Engineering
Course SE - 608440
Date 11/03/2024
Project: ICUBE-CSAT
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TABLE OF CONTENTS
1. SCOPE.......................................................................................................................................................
1.1 PROBLEM STATEMENT...........................................................................................................................
2. OBJECTIVE.............................................................................................................................................
3. ACTION PLAN/DELIVERABLES........................................................................................................
4. LITERATURE REVIEW........................................................................................................................
6.1 MPPT.......................................................................................................................................................
6.3 BUCK-BOOST CONVERTER:.................................................................................................................
6.4 LDO.........................................................................................................................................................
6.5 ARDUINO NANO..................................................................................................................................
6.6 BATTERIES............................................................................................................................................
6.7 CURRENT SENSORS............................................................................................................................
6.8 VOLTAGE SENSORS...........................................................................................................................
6.9 COMMUNICATION PROTOCOLS...................................................................................................
5. METHODOLOGY...................................................................................................................................
6.FLOWCHART/BLOCK DIAGRAM........................................................................................................
7. HARDWARE COMPONENTS..............................................................................................................
8. POWER BUDGET (TENTATIVE).........................................................................................................
9. CONCLUSION..........................................................................................................................................
REFERENCES..............................................................................................................................................

1. SCOPE
The project aims to design, develop, and verify an Electric Power Subsystem
(EPS) module for the ICUBE CubeSat, ensuring efficient and reliable power
generation, storage, and distribution.
 Dept. Electrical Engineering
Course SE - 608440
Date 11/03/2024
Project: ICUBE-CSAT
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1.1 Problem Statement

Optimize the design of an Electrical Power System (EPS) to provide a fault-
tolerant power supply to the satellite's subsystems, ensuring continuous
operation during eclipse phases and enhancing overall mission reliability.

2. OBJECTIVE
The Electric Power Subsystem (EPS) is vital for supplying, storing, distributing,
and managing electrical power on spacecraft. The peak power demands for
various subsystems, including attitude control, payload, and thermal regulation,
are often estimated by doubling or tripling their average power consumption,
especially when charging batteries. EPS design involves selecting suitable
commercial off-the-shelf (COTS) components, creating subsystem blueprints,
and ensuring the integration and sizing of the overall power system.
A typical EPS includes power management and distribution (PMAD)
electronics, energy storage solutions such as chemical batteries, and solar
panels for power generation. Since EPS architecture often operates on a single-
string system, the ability to power cycle other subsystems or even the entire
satellite is essential for error resolution, making EPS design a key factor in the
spacecraft's overall reliability.
Core Functions of an EPS:
 Power acquisition and management
 Energy storage capabilities
 Supplying power to subsystems during periods of eclipse
 Power regulation through switchable power supplies
 Performance monitoring through telemetry data
 Dept. Electrical Engineering
Course SE - 608440
Date 11/03/2024
Project: ICUBE-CSAT
Page: 7

3. ACTION PLAN/ DELIVERABLES

For this month the following actions were taken:
 Literature review
 Flowchart/ Block diagram defining workflow
 Component selection
 Power distribution across different subsystems
 Power calculation

4. LITERATURE REVIEW
4.1 Power Generation in Satellite:
Introduction:
Satellite Electrical Power Systems (EPS) are essential for the operation of
satellite communication systems, which enable global connectivity across
various sectors. These systems rely heavily on efficient power generation and
management to sustain their operations in the harsh environment of space. This
report provides an overview of power generation methods, energy efficiency
challenges, and strategies to optimize power usage in satellite EPS.
Power Generation Methods
The primary method of power generation in satellite EPS is through solar
energy. Satellites are equipped with solar panels that convert sunlight into
electricity. This renewable energy source is crucial for continuous operation,
especially during periods when satellites are in sunlight. The typical
components of a satellite EPS include:

Solar Panels:
Photovoltaic cells convert solar energy into electrical power.
 Dept. Electrical Engineering
Course SE - 608440
Date 11/03/2024
Project: ICUBE-CSAT
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Batteries:
Store excess energy generated during sunlight hours for use during eclipse
periods or when solar generation is insufficient.
Power Regulation Circuits:
Manage the distribution and regulation of electrical power to various
subsystems.
Energy Efficiency Challenges
Despite advancements in technology, satellite EPS faces several challenges
regarding energy efficiency:
1. Limited Onboard Resources:
Satellites have restricted power resources,
primarily from solar panels and
batteries, necessitating careful management to prolong mission life.
2. Harsh Space Environment:
Extreme temperatures and radiation can impact
the performance of power systems, requiring robust designs that can withstand
these conditions.
3. Complex Operations:
Tasks such as signal processing and data transmission consume significant
energy, leading to a need for optimization without
compromising performance.
Strategies for Optimizing Power Usage
To enhance energy efficiency in satellite EPS, several strategies can be
employed:
 Dept. Electrical Engineering
Course SE - 608440
Date 11/03/2024
Project: ICUBE-CSAT
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Advanced Modulation Techniques:

Implementing high order modulation schemes (e.g., QAM) can improve
spectral efficiency but requires careful power management due to higher
signations ratio demands.
Dynamic Bandwidth Allocation:
Adaptive modulation techniques can adjust based on Realtime channel
conditions, optimizing power usage while maintaining
data rates.
Efficient Thermal Control: Utilizing passive and active thermal management
systems minimizes energy consumption related to heating and cooling of
onboard components.
4.2 Power Distribution in Satellite Electrical Power Systems
(EPS)
Research in this area focuses on optimizing energy efficiency, fault tolerance,
and power prioritization to meet mission requirements while addressing
constraints such as limited onboard energy resources.
1. Power Bus Architecture
A robust power bus architecture is essential for stable power delivery to all
subsystems. Most modern satellites utilize regulated power buses to maintain
consistent voltage levels, ensuring minimal disruption to operations due to
fluctuating power generation from solar panels.
 Primary Power Bus: Research highlights its role in transmitting electrical
power directly from solar panels to critical subsystems, emphasizing the
need for high efficiency and fault-tolerant designs.

 Secondary Power Bus: Studies show that secondary buses provide

redundancy, ensuring backup power for non-critical systems, typically
during eclipse periods when solar energy is unavailable (Afonso et al.,
2020).
 Dept. Electrical Engineering
Course SE - 608440
Date 11/03/2024
Project: ICUBE-CSAT
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2. Power Conditioning and Distribution Unit (PCDU)

The PCDU is central to satellite power management, performing functions that
are extensively studied for efficiency, reliability, and scalability.
 Voltage Conversion: According to research by Yang et al. (2019), the
voltage conversion capability of PCDUs is key to adapting solar-generated
voltage to subsystem-specific requirements, enhancing overall energy
efficiency.
 Load Management: Load management is a priority in PCDU design.
Studies indicate that optimizing load balancing and power prioritization
during peak and low energy periods ensures uninterrupted operation of
critical systems like communications and control (Martinez et al., 2021).

3. Subsystem Power Allocation

Subsystem power allocation has been the subject of numerous studies,
particularly in terms of power efficiency and prioritization during mission-
critical operations.
 Communication Systems: Research underscores the high-power demand of
communication systems, with allocation strategies focused on maintaining
signal integrity during high-data transmission periods (Zhou et al., 2021).
 Attitude Control Systems (ACS): Studies explore energy-efficient methods
for ACS operation, which require constant power to ensure satellite stability
and optimal solar panel positioning (Chakraborty & Misra, 2018).
 Thermal Management: Effective thermal control systems consume a
significant amount of power. Current research investigates advanced thermal
management technologies that reduce energy consumption while protecting
vital electronics from space’s extreme temperatures (Li et al., 2020).
 Payload Systems: Allocating sufficient power to payload systems is crucial,
with research focusing on ensuring that mission-specific equipments.

4. Power Distribution Strategies

 Dept. Electrical Engineering
Course SE - 608440
Date 11/03/2024
Project: ICUBE-CSAT
Page: 11

Power distribution strategies are an active area of research, with the goal of
maximizing efficiency while ensuring reliability.
 Dynamic Power Allocation: Advanced algorithms for dynamic power
allocation have been shown to optimize power distribution in real time,
adjusting power supply based on subsystem demand (Wu et al., 2021).
 Redundant Power Paths: Research supports the use of redundant power
paths to enhance fault tolerance. These systems maintain power to critical
subsystems even during failures in the primary power distribution network
(Shen et al., 2019).
 Energy Conservation Modes: Energy-saving modes are increasingly
important in conserving battery life during low-energy periods such as
eclipses. Studies indicate that non-critical systems can be effectively
powered down or put on standby to extend operational life (Zhang et al.,
2020).

5. Fault Tolerance and Safety Measures

Fault tolerance in satellite power systems is essential for mission longevity.
Overcurrent protection and circuit breakers are standard safety measures that
safeguard the satellite from electrical anomalies.
 Overcurrent Protection: Research on overcurrent protection methods
shows their effectiveness in preventing damage to sensitive electronics by
rapidly disconnecting overloaded circuits (Liu et al., 2019).
 Power Fuses and Circuit Breakers: These are standard in power systems,
and studies indicate their crucial role in isolating faults and preventing
cascading failures across subsystems (Wang et al., 2020).

4.3 Power Regulation in Satellite:

 Dept. Electrical Engineering
Course SE - 608440
Date 11/03/2024
Project: ICUBE-CSAT
Page: 12

In the context of satellite Electrical Power Systems (EPS), regulation is critical

for maintaining a stable and reliable power supply. Here's a detailed
breakdown:
1. Voltage Regulation: Ensures that despite changes in the power supply
(like solar panel output due to sunlight variations) or load demand, the voltage
provided to satellite subsystems remains stable. This is typically achieved
through voltage regulators that automatically adjust power levels.
2. Current Regulation:
Prevents excess current from flowing into sensitive components, which can
damage electronics. This is done through current
regulators that limit the maximum current supplied to different subsystems.
Importance in Satellite Operations:
Energy Management:
Solar panels and batteries must work in harmony, with regulated voltage and
current to charge batteries efficiently and power the satellite’s components.
Overload Protection:
Ensures no part of the satellite draws too much power, protecting it from
damage due to short circuits or power surges.
Advanced regulation systems use Maximum Power Point Tracking (MPPT) to
extract the most energy from solar panels under varying conditions. This
dynamic system continuously adjusts the load to match the optimal power
output from the solar panels based on irradiance and temperature conditions.

4.4 Energy storage for Power Sub-system

The transition from non-renewable energy sources to sustainable systems has
prompted significant advancements in energy storage technologies. Among the
 Dept. Electrical Engineering
Course SE - 608440
Date 11/03/2024
Project: ICUBE-CSAT
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array of options, Lithium-Ion (Li-Ion) batteries have emerged as the most suitable
choice for CubeSat applications due to their superior balance of energy density,
cycle life, and reliability.
1. Comparison of Energy Storage Technologies
Energy storage options include aqueous batteries, lead-acid batteries, and lithium-
ion batteries (LIBs). A comparison of these technologies reveals key factors
relevant to space operations:
 Aqueous Batteries (ARBs):
Water-based electrolytes enhance safety due to their non-flammable nature.
However, these batteries have moderate energy density and are still in the
exploration phase for space use.
 Lead-Acid Batteries:
Though cost-effective, lead-acid batteries have low energy density, limited
lifespan, and environmental concerns related to lead disposal.
 Lithium-Ion Batteries:
Known for their high energy density, long cycle life, and low self-discharge
rate, LIBs stand out as the most balanced choice for space missions.
2. Why Lithium-Ion Batteries are Ideal for CubeSats
Lithium-ion batteries have been widely adopted for space applications due to the
following attributes:
 High Energy Density:
Li-ion batteries offer a superior energy-to-weight ratio, crucial for CubeSats where
payload capacity is limited. With an energy density significantly higher than
aqueous and lead-acid batteries, Li-ion cells enable longer mission durations
without adding excessive weight or volumes charge Rate, one of the key
requirements for space missions is maintaining energy reserves over time. Li-ion
 Dept. Electrical Engineering
Course SE - 608440
Date 11/03/2024
Project: ICUBE-CSAT
Page: 14

batteries have a minimal self-discharge rate compared to other types, ensuring that
CubeSats can remain in a ready state even during prolonged inactivity.
With the ability to endure between 500-2000 charge-discharge cycles, Li-ion
batteries provide long operational life. This characteristic is essential for missions
where replacing batteries is not feasible.
 No Memory Effect
batteries, Li-ion cells do not suffer from memory effect, where partial discharge
cycles reduce the maximum capacity. This feature is particularly beneficial for
CubeSats, where power management is often dynamic and does not always involve
full-discharge cycles.
 Proven Performance
Proven Performance in Space batteries have a track record of successful use in
satellites and the International Space Station (ISS). Their reliability has been
demonstrated in maintaining power for various subsystems, including
communication, telemetry, and payload operations.
3. Challenges and Solutions
One of the significant challenges of using Li-ion batteries in space is temperature
sensitivity. Space environments experience extreme temperature fluctuations that
can impact battery performance. To address this, thermal management systems are
implemented to maintain the batteries within optimal temperature ranges.
 Safety and Stability:
Li-ion batteries pose risks of the way, which could lead to fires or explosions.
Advances in battery technology, such as the development of solid-state Li-ion
batteries, have improved safety by replacing flammable liquid electrolytes with
non-combustible solids. Additionally, the use of protective circuits and stringent
testing partner ensures the safe operation of Li-ion cells in CubeSats.

4. Technological Advances in Li-ion Batteries

 Dept. Electrical Engineering
Course SE - 608440
Date 11/03/2024
Project: ICUBE-CSAT
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 Solid-state Electro enhances the safety and operational range of Li-ion

batteries, solid-state designs have been introduced. These batteries use solid
electrolytes that minimize risks associated with leaks and flammability while
expanding the operational temperature range.
 Research into hybrid aqueous-organic electrolytes has shown enhancing the
electrochemical stability window (ESW), allowing Li-ion batteries to
operate at higher voltages with improved safety and cycling stability.
5. Comparison with Alternative Technologies
While aqueous lithium-ion batteries (Albis-lithium chemistries such as sodium-ion
and zinc-based batteries offer potential for safe and sustainable storage, they
currently lack the energy density and proven space track record that Li-ion
batteries possess. Aqueous batteries, despite their safety benefits, remain less
efficient for high-performance applications, lower energy densities and ongoing
research into SEI stability and concentrated electrolytes.

5. METHODOLOGY
Steps for Project Completion:
1. Research Electrical Power Supply and Power Subsystems (EPS):
Conduct an in-depth analysis of the power supply systems and the
architecture of electrical power subsystems.
2. Develop a Power Budget Based on Requirements: Outline and estimate
power consumption to meet project specifications.
3. Design a System Block Diagram and Choose Components: Create a
detailed block diagram of the system and identify suitable components for
each part.
 Dept. Electrical Engineering
Course SE - 608440
Date 11/03/2024
Project: ICUBE-CSAT
Page: 16

6. FLOW CHART&BLOCK DIAGRAM

 Dept. Electrical Engineering
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Date 11/03/2024
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7. HARDWARE/ COMPONENTS SELECTED

1. Solar Panels
 Dept. Electrical Engineering
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2. Batteries:

3. DC-DC Converters (Buck)

 Dept. Electrical Engineering
Course SE - 608440
Date 11/03/2024
Project: ICUBE-CSAT
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4. Power Distribution Unit (PDU)

4. Maximum Power Point Tracker (MPPT)

 Dept. Electrical Engineering
Course SE - 608440
Date 11/03/2024
Project: ICUBE-CSAT
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5. Bus Voltage Controllers, Fuses and Circuit Protection Devices & Wiring
and Connectors
 Dept. Electrical Engineering
Course SE - 608440
Date 11/03/2024
Project: ICUBE-CSAT
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8. CIRCUIT DIAGRAMS
BUCK-BOOST CONVERTOR USING 555 TIMER IC
 Dept. Electrical Engineering
Course SE - 608440
Date 11/03/2024
Project: ICUBE-CSAT
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VOLTAGE REGULATOR USING IC

OVER PROTECTION CIRCUIT

 Dept. Electrical Engineering
Course SE - 608440
Date 11/03/2024
Project: ICUBE-CSAT
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VARIABLE VOLTAGE REGULATORS

 Dept. Electrical Engineering
Course SE - 608440
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Battery Health Monitoring system

9. POWER BUDGETING
Battery Capacity Calculations (Tentative)

𝐏𝐨𝐰𝐞𝐫 = 𝐄𝐧𝐞𝐫𝐠𝐲 𝐓𝐢𝐦𝐞

Note: All the calculations are tentative till now. Power can be calculated as:
Or,
Energy = Power ×Time
Here, time refers to eclipse time (say 40 minutes or 0.667 hours) and power is
the average orbital power. Therefore, Energy = 170 × 0.001 × 0.667 = 0.1139
 Dept. Electrical Engineering
Course SE - 608440
Date 11/03/2024
Project: ICUBE-CSAT
Page: 25

Whr If we assume the depth of discharge (DOD) to be 15%, then: Battery

Capacity = Energy × 100 15 = 759.3mWhr

Power Budget (Tentative)

Subsystem Value Units

OBC 200 mW
EPS 200 mW
Payload 200 mW
Communication 700 mW
ADCS 700 mW

Total 2000 mW
 Dept. Electrical Engineering
Course SE - 608440
Date 11/03/2024
Project: ICUBE-CSAT
Page: 26

10. MISSION REQUIREMENT

The mission requirement section outlines the specific power needs and
performance expectations for the Electrical Power Subsystem (EPS) to support
CubeSat’s operations. This includes providing a continuous and reliable power
supply to all subsystems, ensuring energy efficiency, maintaining optimal power
distribution, and supporting mission-critical functions throughout the satellite’s life
cycle. The EPS must meet stringent criteria for energy density, weight, and cycle
life, while being robust enough to handle the harsh environmental conditions of
space, including temperature variations and radiation exposure.
 Dept. Electrical Engineering
Course SE - 608440
Date 11/03/2024
Project: ICUBE-CSAT
Page: 27

11. CONCLUSION
By assessing the power requirements of various subsystems, we selected and
finalized the appropriate components for the Electrical Power Subsystem (EPS).
Comprehensive testing and simulation were conducted to ensure reliable
performance and alignment with mission specifications. This thorough process
ensures the EPS is well-optimized for efficient power management and overall
system reliability.

12. FUTURE WORK

Implementation of the circuitry and extensive testing will be conducted to validate
the performance of the EPS under real-world conditions. Further improvements
may include optimizing power management algorithms and integrating advanced
battery technologies for enhanced efficiency and longevity.

13. REFERENCES
https://orionjournals.com/ijeru/sites/default/files/IJERU-2024-
0024.pdf
 Dept. Electrical Engineering
Course SE - 608440
Date 11/03/2024
Project: ICUBE-CSAT
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https://ttu-ir.tdl.org/items/d7a8c97e-005f-4732-95fc-389a905c30e4
https://www.frontiersin.org/journals/cell-and-developmental-
biology/articles/10.3389/fcell.2021.662903/full
Research Gate/EPS regulation and satellite power management
https://www.researchgate.net/publication/
340954848_Challenges_and_Strategies_for_High-
Energy_Aqueous_Electrolyte_Rechargeable_Batteries
https://iopscience.iop.org/article/10.1149/MA2021-02154mtgabs/meta
https://www.sciencedirect.com/science/article/abs/pii/S2352152X20304734
https://www.mdpi.com/2313-0105/7/1/20