Regenerative Braking during Differnt Motor Directions.pdf
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Transcript of Regenerative Braking during Differnt Motor Directions.pdf
Vignesh Shenoy
Department of Electronics
Carleton University
1125 Colonel by Drive
Ottawa, ON, Canada, K1S 5B6
Dr. Cheryl Cundell
Instructor, Communication Courses for Disciplines and
Professions
School of Linguistics and Language Studies
236 Paterson Hall, Carleton University
Ottawa, ON, Canada, K1S 5B6
December 1, 2015
Dear Dr. Cundell,
This letter is produced as a requirement of CCDP2100 for Section I.
The attached report is my final technical report. The title of the document is Regenerative
Braking during Different Motor Directions.
The research topic that was used for the vehicle design project in regards to Efficiency of hybrid
cars is regenerative braking and how energy is generated during different motor directions. The
question used as a guide for this design project is; how does the regenerative braking system adapt
to different motor directions. The topic of regenerative braking is significant because it will
describe the process of converting movement energy to electrical energy and methods to improve
the overall efficiency. The enhancement of the regenerative braking system benefits energy
consumption rates and energy production rates. Thank you for reading this technical concept
report, if you have any further questions, please feel free to contact me by email at
Sincerely,
Vignesh Shenoy
Regenerative Braking during different Motor Directions
Vignesh Shenoy
CCDP – 2100
Cheryl Cundell
December 1st 2015
Vignesh Shenoy -ii- December 1, 2015 Final Technical Report
Abstract
Regenerative braking is a system that utilizes unused momentum of the vehicle slowing down. As
the wheels of a hybrid electric car slow down, their kinetic energy is redirected to turn a motor
generator. The motor generator spins to create an energy carrying current that is distributed to
various electrical components. Electrical Energy is generated to be charged and stored in electrical
components. The Regenerative Braking System distributes energy to produce forward momentum
and to charge the battery unit. However in practical scenarios, hybrid electric vehicles travel
forwards and backwards, while deaccelerating in both directions. The system adapts to the
direction of the motor by adjusting the orientation of the battery and aligning the rectifier circuits
to allow energy flow. Regenerative Brakes improve the overall efficiency of a hybrid electric car
by generating energy while the vehicle is moving in either direction and aligning rectifier circuits
for faster energy flow.
Table of Contents
Abstract ........................................................................................................................................................ ii
List of Figures ............................................................................................................................................... iv
List of Equations ........................................................................................................................................... iv
Nomenclature .............................................................................................................................................. iv
1.0 Introduction ............................................................................................................................................ 1
2.0 Background ............................................................................................................................................. 1
3.0 Discussion ............................................................................................................................................... 2
3.1 Alternating Current to Direct Current Conversion .............................................................................. 2
3.1.1 Kirchhoff’s Current Law in relation to conversion ....................................................................... 3
3.2 Different Circuit Cycles during different motor directions ................................................................. 4
4.0 Conclusion .............................................................................................................................................. 6
5.0 References .............................................................................................................................................. 7
Appendices ................................................................................................................................................... 8
Vignesh Shenoy -iv- December 1, 2015 Final Technical Report
List of Figures 1) Figure 1: Rectifier Circuit Page 4
2) Figure 2: Kirchhoff’s Current Law at a point on a circuit Page 5
3) Figure 3: Motor Direction Cycles Page 6
List of Equations 1) Equation 1: Sum of current at a point Page 5
2) Equation 2: General Current Law Page 5
Nomenclature
I Current
Vignesh Shenoy -1- December 1, 2015 Final Technical Report
1.0 Introduction The reason this report was produced as a requirement of CCDP Section I. The purpose of the Final
Technical Report is to describe the relationship between Kirchhoff’s Current Law and the
Regenerative Braking Process. This report addresses the research question
-How does the Regenerative Braking System adjust to different motor directions?
A background section is included to introduce the Regenerative Braking process and its
components. A discussion section follows, explaining the technical concepts involved with
charging and discharging a battery during Regenerative Braking. Definitions and figures
displaying the charging process are included. A Conclusion concludes the report by redefining the
purpose and summarizes key points mentioned.
2.0 Background Hybrid electric cars are vehicles that utilize a combustion engine and an electrical motor to produce
the sufficient kinetic energy (energy relating to motion) needed to create forward momentum [2,
pp. 21]. Regenerative Braking is an electronic system that is implemented in hybrid electric cars
to supply energy to the electrical motor while the vehicle is slowing down [1, pp. 1]. The primary
focus of Regenerative Braking is to store and reuse energy that is lost in regular braking systems.
In regular braking systems, as the wheels slow down, their kinetic energy is lost as heat and sound
[2, pp. 228]. However regenerative braking redirects kinetic energy from the wheels to spin a
motor-generator [2, pp. 280]. A motor-generator is a mechanical component that when spun
creates a voltage carrying current [2, pp. 253]. The current produced from the generator is stored
in a battery unit, which is then consumed by various components such as the electrical motor to
produce forward momentum [1, pp. 253]. In addition, momentum can travel forwards and
Vignesh Shenoy -2- December 1, 2015 Final Technical Report
backwards, meaning the Regenerative Braking system must adapt to the direction the motor is
generating in order to achieve efficiency. Regenerative Braking improves the efficiency of hybrid
electric cars by generating electrical energy from the deacceleration of the vehicle.
3.0 Discussion
3.1 Alternating Current to Direct Current Conversion The process of Regenerative Braking can be broken down into three stages; deacceleration, energy
generation and quick access storage. Deacceleration is the reduction of speed in the wheels. As
wheels do not stop instantly, Regenerative Braking utilizes the momentum while the wheels
approach a full stop. The unused momentum is channeled to turn a motor-generator [2, pp. 280].
As the motor-generator spins, it generates a current that carries energy from one component to the
next [2, pp. 157]. The current generated is called Alternating Current, otherwise known as AC. AC
current is current moving backwards and forwards, however for current to be used it must travel
in only one direction [2, pp. 156]. Current travelling in one direction is called Direct Current,
otherwise known as DC. Figure 1 displays the electrical circuit that is implemented in a
Regenerative Braking system to produce direct current, known as a Rectifier Circuit. AC current
enters the rectifier circuit and travels through a rectifier. A rectifier is a circuit component that only
allows current to flow in one direction, meaning the current that exits the rectifier is direct current.
The purpose of converting AC current to DC current is to provide constant energy to an electrical
component, such as a battery [2, pp. 156]. The correct conversion is important in order for energy
to be directed to the electrical motor for the production of momentum [2, pp. 157].
Vignesh Shenoy -3- December 1, 2015 Final Technical Report
Figure 1: Rectifier Circuit [7]
3.1.1 Kirchhoff’s Current Law in relation to conversion As displayed in Figure 1, current enters and exits a rectifier. Since current must flow from one
point of the rectifier to next, Kirchhoff’s Current Law (KCL) states that the value of the current
must be equal. KCL is the theorem that allows current to be converted from AC to DC while
retaining its value of energy [3]. Kirchhoff’s Current Law states that the sum of current entering a
point in the circuit must equal the sum of current leaving. As displayed in Equation 1, the sum
represented by ∑, of I representing current measured in amperes, must equal zero [3]. Figure 2
displays a point on a circuit in the middle. I1 and I2 are currents entering the point, and I3 and I4
are current leaving. Sum of I1 plus I2 must equal sum of I3 plus I4, resulting in Equation 2 [3].
Equation 2 states that I in (current entering) must equal I out (current leaving). Equation 1 and 2
form Kirchhoff’s Current law [3]. KCL justifies AC being converted to DC, to then be stored in
an electrical component.
Vignesh Shenoy -4- December 1, 2015 Final Technical Report
∑𝐼 = 0 Equation (1)
𝐶𝑢𝑟𝑟𝑒𝑛𝑡𝐼𝑛 = 𝐶𝑢𝑟𝑟𝑒𝑛𝑡𝑂𝑢𝑡 Equation (2)
3.2 Different Circuit Cycles during different motor directions Vehicles can produce forward and backward momentum while in operation. Similarly vehicles can
also deaccelerate while moving forwards or backwards. Regenerative Braking must generate
electrical energy in any motor direction to achieve efficiency. Electrical components within the
system adapt to the direction of the momentum by switching the direction current is flowing.
Figure 3 displays two orientations in which the system draws energy and regenerates energy. On
the right side of Figure 3, the vehicle is in the “On” cycle, representing energy being consumed.
The left side of Figure 3 displays the “Off” cycle, representing when the vehicle is slowing down
and generating energy [6]. The single line on the left of the diagrams represents a capacitor, which
quick access energy that the system can use rather than from the battery, represented by the M in
the diagrams. Q1, Q2, Q3 and Q4 are rectifier circuits within the system that redirect current to its
Figure 2: Kirchhoff’s Current Law at a point on a circuit [4]
Vignesh Shenoy -5- December 1, 2015 Final Technical Report
appropriate component. During the “On” cycles, in both directions, rectifier circuits are aligned to
allow energy to be drawn from the capacitors to be stored in the battery unit. During the
regenerative “Off” cycles, energy is produced and stored in capacitors where it can power the
battery unit or the electrical motor [6]. When the vehicle switches motor directions, the alignment
of the battery switches to allow faster energy transfer from rectifier circuits. In the forward “on”
cycle, Q1 is activated to allow faster energy from the capacitor and similarly for the backwards
“on” cycle, Q4 is activated. Regenerative Braking adapts to different motor directions by
dynamically switching the positions of rectifier circuits within the system to allow energy
generating [6]. The different positions of the rectifier circuits allows the system to generate
electrical energy faster creating better efficiency for the hybrid electric car.
Figure 3: Motor Direction Cycles [6]
Vignesh Shenoy -6- December 1, 2015 Final Technical Report
4.0 Conclusion The purpose of the report was to answer the research question on how regenerative braking adapts
to different motor directions as well as describe the technical concepts related to regenerative
braking. The Regenerative Braking process consists of deacceleration, generating electrical energy
and quick access storage. Regenerative Braking converts kinetic energy to electrical energy by
using unused momentum in the wheels while slowing down to generate a current. This current
switches from Alternating to Direct due to Kirchhoff’s Current Law by passing through a rectifier
circuit. Since a motor moves in two directions, rectifier circuits align in two different orientations
to allow energy to be regenerated while moving in either direction. By dynamically changing the
positions of the circuits, Regenerative Braking efficiently generates electrical energy while moving
forwards and backwards.
Vignesh Shenoy -7- December 1, 2015 Final Technical Report
5.0 References
[1] A. Baker, Vehicle braking. London: Pentech Press, 1986.
[2] J. Larminie and J. Lowry, Electric vehicle technology explained. West Sussex, England: J. Wiley, 2003.
[3] Facstaff.bucknell.edu, 'Kirchhoff's Current Law', 2015. [Online]. Available:
http://www.facstaff.bucknell.edu/mastascu/elessonshtml/Basic/Basic4Ki.html. [Accessed: 02-
Nov- 2015].
[4] Upload.wikimedia.org, 2015. [Online]. Available:
https://upload.wikimedia.org/wikipedia/commons/thumb/f/f2/Kirchhoff%27s_Current_Law.svg/
250px-Kirchhoff%27s_Current_Law.svg.png. [Accessed: 02- Nov- 2015].
[5] B. Media, 'Green Car Congress: Recent Hybrid Braking Complaints Highlight Regenerative
Braking Design Issues', Greencarcongress.com, 2015. [Online]. Available:
http://www.greencarcongress.com/2010/02/braking-20100208.html. [Accessed: 02- Nov- 2015].
[6] Hassockshog.co.uk, 'Hassock Hog motor controller description', 2015. [Online]. Available:
http://www.hassockshog.co.uk/motor_controller_description.htm. [Accessed: 01- Dec- 2015].
[7] Lessons in Electric Circuits, 'Discrete Semiconductor Circuits', 2015. [Online]. Available:
https://www.ibiblio.org/kuphaldt/electricCircuits/Exper/EXP_5.html. [Accessed: 01- Dec- 2015].
Vignesh Shenoy -8- December 1, 2015 Final Technical Report
Appendices [1] A. Baker, Vehicle braking. London: Pentech Press, 1986.
Pg. 1:
Vignesh Shenoy -9- December 1, 2015 Final Technical Report
Pg. 253:
Vignesh Shenoy -10- December 1, 2015 Final Technical Report
[2] J. Larminie and J. Lowry, Electric vehicle technology explained. West Sussex, England: J. Wiley, 2003.
Pg. 280:
Vignesh Shenoy -11- December 1, 2015 Final Technical Report
Pg. 228:
Vignesh Shenoy -12- December 1, 2015 Final Technical Report
Pg. 156:
Vignesh Shenoy -13- December 1, 2015 Final Technical Report
Pg. 157:
Vignesh Shenoy -14- December 1, 2015 Final Technical Report
Pg. 21:
Vignesh Shenoy -15- December 1, 2015 Final Technical Report
[3] Facstaff.bucknell.edu, 'Kirchhoff's Current Law', 2015. [Online]. Available:
http://www.facstaff.bucknell.edu/mastascu/elessonshtml/Basic/Basic4Ki.html. [Accessed: 02-
Nov- 2015].
[5] B. Media, 'Green Car Congress: Recent Hybrid Braking Complaints Highlight Regenerative
Braking Design Issues', Greencarcongress.com, 2015. [Online]. Available:
http://www.greencarcongress.com/2010/02/braking-20100208.html. [Accessed: 02- Nov- 2015].
Vignesh Shenoy -16- December 1, 2015 Final Technical Report
[6] Hassockshog.co.uk, 'Hassock Hog motor controller description', 2015. [Online]. Available:
http://www.hassockshog.co.uk/motor_controller_description.htm. [Accessed: 01- Dec- 2015].