Battery-Driven Electric Vehicle with Regenerative Braking
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Battery-Driven Electric Vehicle with Regenerative Braking
𝐈𝐧𝐭𝐫𝐨𝐝𝐮𝐜𝐭𝐢𝐨𝐧
Regenerative braking is one of the important features of modern electric vehicles. When an EV decelerates, the traction motor can temporarily operate as a generator.
Battery-Driven Electric Vehicle with Regenerative Braking
Instead of dissipating all braking energy as heat:
The motor generates electrical energy.
The converter provides a reverse power-flow path.
The recovered energy is transferred to the battery.
Battery current changes direction.
Battery SOC increases slightly during regeneration.
The MATLAB/Simulink model presented here demonstrates both motoring operation and regenerative braking operation.
𝐒𝐲𝐬𝐭𝐞𝐦 𝐎𝐯𝐞𝐫𝐯𝐢𝐞𝐰
The simulation mainly consists of:
Battery energy source
Bidirectional DC-DC converter
DC motor
Speed reference
Speed feedback
PID speed controller
PWM generation
MOSFET switching arrangement
Mechanical load torque
Battery voltage, current, and SOC measurement
Motor speed, current, and electromagnetic torque measurement
The overall energy flow changes according to whether the vehicle is accelerating, running normally, or braking.
Main Simulation Parameters
Parameter | Value Used in the Simulation |
Battery voltage | 60 V |
Initial battery SOC | 50% |
DC motor power | 5 HP |
Motor-related voltage stated in the model | 240 V |
DC supply shown around motor section | 300 V |
Applied load torque | 10 N·m |
Initial speed reference | 120 rad/s |
Braking speed reference | 50 rad/s |
Braking command time | Around 2 s |
Braking transition interval used | About 0.05 s |
𝐖𝐨𝐫𝐤𝐢𝐧𝐠 𝐏𝐫𝐨𝐜𝐞𝐬𝐬
The model operates mainly in two conditions.
𝐌𝐨𝐭𝐨𝐫𝐢𝐧𝐠 𝐎𝐩𝐞𝐫𝐚𝐭𝐢𝐨𝐧
During normal vehicle operation:
Battery → Bidirectional Converter → DC Motor → Mechanical Load
The battery supplies electrical power to the DC motor.
The motor converts this electrical energy into mechanical torque and maintains the commanded vehicle speed.
During this condition:
Battery current is positive in the discharge direction.
Battery SOC gradually decreases.
Motor current is positive.
Electromagnetic torque is positive.
The motor operates in the normal motoring region.
𝐑𝐞𝐠𝐞𝐧𝐞𝐫𝐚𝐭𝐢𝐯𝐞 𝐁𝐫𝐚𝐤𝐢𝐧𝐠
To demonstrate regenerative braking, the reference speed is reduced from:
120 rad/s → 50 rad/s
When the speed command decreases, the rotating motor cannot immediately reduce its mechanical energy.
The DC machine therefore enters a generating condition.
The energy-flow direction becomes:
DC Motor → Bidirectional Converter → Battery
During this interval:
Motor current becomes negative.
Electromagnetic torque becomes negative.
Battery current becomes negative.
Recovered energy flows into the battery.
Battery SOC starts increasing.
Battery terminal voltage also shows a charging response.
This confirms the regenerative braking action.
𝐂𝐨𝐧𝐭𝐫𝐨𝐥 𝐒𝐭𝐫𝐚𝐭𝐞𝐠𝐲
The EV motor is controlled using a closed-loop speed-control system.
Speed Reference
A desired motor speed is provided as the reference signal.
For the first operating condition:
Reference speed = 120 rad/s
For the braking test, the reference is reduced to:
50 rad/s
Speed Feedback
The actual DC motor speed is continuously measured and compared with the reference speed.
The difference between the two signals represents the speed error.
PID Controller
The speed error is processed through a PID controller.
The controller adjusts the switching command so that:
The motor reaches the desired speed.
Speed tracking is maintained during normal operation.
The motor responds to a reduction in speed command.
Regenerative braking can occur during deceleration.
PWM and MOSFET Control
The controller output is processed by the pulse-generation stage.
The generated switching pulses control the MOSFETs of the bidirectional converter.
This switching arrangement enables power flow in both directions.
𝐁𝐢𝐝𝐢𝐫𝐞𝐜𝐭𝐢𝐨𝐧𝐚𝐥 𝐃𝐂-𝐃𝐂 𝐂𝐨𝐧𝐯𝐞𝐫𝐭𝐞𝐫
The bidirectional converter is one of the most important sections of this EV model.
It allows:
Battery-to-motor energy transfer during driving.
Motor-to-battery energy transfer during braking.
From one power-flow direction, the converter performs the required DC-DC conversion for supplying the motor.
When the energy-flow direction reverses, the same converter provides the required path for regenerative charging.
Therefore, a single converter arrangement supports both propulsion and energy recovery.
𝐌𝐨𝐭𝐨𝐫𝐢𝐧𝐠 𝐒𝐢𝐦𝐮𝐥𝐚𝐭𝐢𝐨𝐧 𝐑𝐞𝐬𝐮𝐥𝐭𝐬
Initially, the reference speed is maintained at approximately 120 rad/s.
The actual motor speed gradually follows the reference and reaches the commanded operating point.
Observed Motoring Performance
Variable | Approximate Observed Value |
Reference speed | 120 rad/s |
Actual steady-state speed | Around 120 rad/s |
Speed tracking time | Around 1.5 s |
Motor terminal voltage | Around 150 V |
Battery current | Around 27.5 A |
Motor current | Around 11 A |
Electromagnetic torque | Around 11 N·m |
Applied load torque | 10 N·m |
During this operating condition, the battery supplies power continuously.
Therefore:
Battery SOC decreases gradually.
Battery current remains in the discharge direction.
Motor torque remains positive.
The EV operates in the propulsion mode.
𝐑𝐞𝐠𝐞𝐧𝐞𝐫𝐚𝐭𝐢𝐯𝐞 𝐁𝐫𝐚𝐤𝐢𝐧𝐠 𝐑𝐞𝐬𝐮𝐥𝐭𝐬
The regenerative braking test is introduced by reducing the reference speed from 120 rad/s to 50 rad/s.
Once this command is applied, the actual speed starts decreasing.
More importantly, the electrical and mechanical variables reverse during the braking interval.
Regenerative Braking Response
Variable | Before Braking | During Regeneration |
Speed reference | 120 rad/s | 50 rad/s |
Motor current | Around +11 A | Around −20 A |
Electromagnetic torque | Around +11 N·m | Around −20 N·m |
Battery current | Around +27.5 A | Around −18 A |
Battery SOC | Decreasing | Increasing |
Battery operating state | Discharging | Charging |
Motor operating state | Motoring | Generating |
The change from positive to negative motor current clearly indicates reversal of electrical power flow.
Similarly, the negative electromagnetic torque acts against the direction of rotation and produces the braking action.
𝐁𝐚𝐭𝐭𝐞𝐫𝐲 𝐑𝐞𝐬𝐩𝐨𝐧𝐬𝐞 𝐃𝐮𝐫𝐢𝐧𝐠 𝐁𝐫𝐚𝐤𝐢𝐧𝐠
The battery waveforms provide direct evidence of regenerative energy recovery.
Battery Current
During normal motoring:
Battery current ≈ +27.5 A
During regenerative braking:
Battery current ≈ −18 A
The current-direction reversal shows that energy is no longer being supplied only by the battery. Instead, electrical energy generated by the motor is flowing back toward the battery.
Battery SOC
During motoring:
SOC gradually decreases because the battery supplies the motor.
During braking:
SOC begins to increase because regenerated energy is stored in the battery.
Although the SOC variation is small over the short simulation interval, its increasing trend confirms battery charging.
Battery Voltage
A small increase in battery voltage is also observed during the regenerative interval.
This behavior corresponds to the battery receiving charging power from the DC motor through the bidirectional converter.
𝐌𝐨𝐭𝐨𝐫 𝐁𝐞𝐡𝐚𝐯𝐢𝐨𝐫 𝐃𝐮𝐫𝐢𝐧𝐠 𝐑𝐞𝐠𝐞𝐧𝐞𝐫𝐚𝐭𝐢𝐨𝐧
The DC machine behaves differently during braking compared with propulsion.
Normal Driving
Motor current is positive.
Electromagnetic torque is positive.
Electrical energy is converted into mechanical energy.
Braking
Motor current becomes negative.
Electromagnetic torque becomes negative.
The machine temporarily behaves as a generator.
Mechanical energy is converted back into electrical energy.
This generated energy is transferred through the converter to the battery.
𝐏𝐨𝐰𝐞𝐫 𝐅𝐥𝐨𝐰 𝐒𝐮𝐦𝐦𝐚𝐫𝐲
Operating Condition | Motor Mode | Energy Direction | Battery Condition |
Acceleration / Motoring | Motor | Battery → Motor | Discharging |
Constant-speed operation | Motor | Battery → Motor | Discharging |
Deceleration / Braking | Generator | Motor → Battery | Charging |
Regenerative interval | Generator | Mechanical energy → Electrical energy → Battery | SOC increases |
𝐊𝐞𝐲 𝐅𝐞𝐚𝐭𝐮𝐫𝐞𝐬
MATLAB/Simulink implementation of a battery-driven electric vehicle.
DC motor-based traction system.
Closed-loop PID speed control.
Bidirectional DC-DC converter.
MOSFET-based switching operation.
Battery voltage, current, and SOC monitoring.
Motor speed, current, and torque monitoring.
Forward motoring operation.
Regenerative braking operation.
Bidirectional energy transfer.
Negative motor torque during braking.
Battery-current reversal during regeneration.
Visible increase in battery SOC during regenerative charging.
Speed-reference variation for demonstrating braking behavior.
𝐀𝐩𝐩𝐥𝐢𝐜𝐚𝐭𝐢𝐨𝐧𝐬
This MATLAB/Simulink model is useful for studying:
Electric vehicle propulsion systems
EV regenerative braking
Battery energy recovery
Bidirectional DC-DC converters
DC motor speed control
EV battery charging and discharging
Energy-flow analysis
Motor-to-generator transition
Battery SOC behavior
Power electronic converter control
Electric drivetrain control studies
It can be particularly useful for students, researchers, and engineers who want to understand the basic operating principle of regenerative braking through simulation.
𝐖𝐡𝐲 𝐑𝐞𝐠𝐞𝐧𝐞𝐫𝐚𝐭𝐢𝐯𝐞 𝐁𝐫𝐚𝐤𝐢𝐧𝐠 𝐈𝐬 𝐔𝐬𝐞𝐟𝐮𝐥 𝐢𝐧 𝐄𝐕𝐬
In conventional braking, a significant portion of the vehicle's kinetic energy is dissipated during deceleration.
Regenerative braking provides an alternative approach by recovering part of this energy.
Its main benefits include:
Improved utilization of stored battery energy
Recovery of energy during vehicle deceleration
Increased EV energy efficiency
Reduced dependence on purely mechanical braking
Improved overall electric drivetrain performance
Extension of driving capability through recovered energy
𝐂𝐨𝐧𝐜𝐥𝐮𝐬𝐢𝐨𝐧
The Battery-Driven Electric Vehicle with Regenerative Braking MATLAB/Simulink model successfully demonstrates bidirectional energy flow between the battery and DC motor.
During normal motoring, the battery supplies electrical energy to the motor, resulting in positive motor current and torque while the battery SOC gradually decreases.
When the speed reference is reduced from 120 rad/s to 50 rad/s, the DC machine enters regenerative operation. The motor current changes from approximately +11 A to −20 A, electromagnetic torque becomes negative, and battery current changes from approximately +27.5 A to −18 A.
The negative battery current, increasing SOC, and battery-voltage response confirm that braking energy is being recovered and transferred back to the battery through the bidirectional DC-DC converter.
Overall, the simulation provides a simple and effective platform for understanding EV propulsion, speed control, bidirectional converter operation, and regenerative braking energy recovery in MATLAB/Simulink.
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