Regenerative Braking in BLDC Motor Driven Electric Vehicle

Regenerative Braking in BLDC Motor Driven Electric Vehicle

𝐈𝐧𝐭𝐫𝐨𝐝𝐮𝐜𝐭𝐢𝐨𝐧

Regenerative Braking in BLDC Motor Driven Electric Vehicle

Regenerative braking in bldc motor employing buck converter

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Regenerative braking is an important energy-saving technique used in modern electric vehicles. During normal braking, the vehicle’s kinetic energy is generally converted into heat and lost through the braking system. In a regenerative braking system, part of this kinetic energy is converted into electrical energy and transferred back to the battery.

This MATLAB/Simulink model demonstrates regenerative braking in a BLDC motor-driven electric vehicle. The system combines :

• A battery energy source

• A buck converter

• A voltage source inverter

• A 500 W BLDC motor

• Hall sensor-based commutation

• Speed control

• Running and braking control modes

• Battery-current-based regenerative braking control

The model helps students, researchers, and engineers understand how a BLDC motor operates as a motor during acceleration and as a generator during braking.

𝐒𝐲𝐬𝐭𝐞𝐦 𝐎𝐯𝐞𝐫𝐯𝐢𝐞𝐰

The proposed electric vehicle drive system uses a battery to supply electrical power to the BLDC motor through a power electronic converter and a three-phase voltage source inverter.

During the running mode, power flows from the battery to the motor. During the braking mode, the direction of power flow changes, and energy from the rotating motor is transferred back to the battery.

Main system components

Component	Function
Battery bank	Supplies energy during motor operation and stores recovered braking energy
Buck converter	Controls the DC voltage supplied to the inverter
IGBT switch	Regulates converter output using PWM pulses
Voltage source inverter	Converts DC power into controlled three-phase power
BLDC motor	Provides vehicle propulsion and acts as a generator during braking
Hall sensors	Detect rotor position for electronic commutation
Hall decoder	Generates the required switching sequence
PID speed controller	Regulates motor speed during running mode
PI braking controller	Controls regenerative battery current
PWM generator	Produces switching pulses for the converter and braking operation
Run–brake logic	Selects the appropriate operating mode

𝐒𝐲𝐬𝐭𝐞𝐦 𝐏𝐚𝐫𝐚𝐦𝐞𝐭𝐞𝐫𝐬

The important electrical and mechanical parameters used in the simulation are listed below.

Parameter	Value
Number of batteries	6
Voltage of each battery	12 V
Total battery voltage	72 V
Battery rated capacity	150 Ah
Initial battery state of charge	50%
BLDC motor rated power	500 W
BLDC motor rated voltage	48 V
Reference motor speed	3000 rpm
Running duration	0 to 5 seconds
Braking activation time	5 seconds
Initial battery voltage observed	Approximately 71.5 V
Battery voltage during regeneration	Approximately 71.6 V

𝐖𝐨𝐫𝐤𝐢𝐧𝐠 𝐏𝐫𝐨𝐜𝐞𝐬𝐬

The operation of the model can be divided into two main modes.

1. Running mode

From the beginning of the simulation until five seconds, the system operates in the running mode.

• The reference speed is set to 3000 rpm.

• The actual BLDC motor speed is measured continuously.

• The measured speed is compared with the reference speed.

• The resulting speed error is processed through the PID controller.

• The controller generates a suitable duty-cycle command.

• The duty cycle is processed by the PWM generator.

• PWM pulses control the IGBT switch of the buck converter.

• The converter regulates the voltage supplied to the voltage source inverter.

• The Hall decoder generates six-step switching signals for the inverter.

• The BLDC motor speed is maintained close to the reference value.

In this mode, the direction of energy flow is:

Battery → Buck Converter → Voltage Source Inverter → BLDC Motor

2. Regenerative braking mode

At five seconds, the running command is disabled and the braking command is activated.

• The motor continues rotating because of its mechanical inertia.

• The BLDC motor begins operating as a generator.

• Electromagnetic torque becomes negative.

• Electrical energy is produced by the rotating motor.

• The voltage source inverter provides a path for reverse energy flow.

• The generated energy passes through the converter and diode arrangement.

• The recovered electrical energy is transferred to the battery.

• Battery current becomes negative, indicating charging operation.

• The motor speed gradually decreases from 3000 rpm to zero.

During regenerative braking, the direction of power flow is:

BLDC Motor → Voltage Source Inverter → Converter/Diode Path → Battery

𝐂𝐨𝐧𝐭𝐫𝐨𝐥 𝐒𝐭𝐫𝐚𝐭𝐞𝐠𝐲

The control system coordinates motor speed regulation, inverter switching, and regenerative braking.

Speed-control loop

The speed-control loop is active during normal motor operation.

Its main tasks are:

• Measuring the actual rotor speed

• Comparing actual speed with the 3000 rpm reference

• Processing the speed error through a PID controller

• Generating a duty-cycle command

• Controlling the buck converter using PWM pulses

• Maintaining the desired BLDC motor speed

Hall sensor decoder

The BLDC motor requires electronic commutation because it does not use mechanical brushes.

The Hall sensor decoder:

• Receives rotor-position signals from the Hall sensors

• Identifies the rotor position

• Selects the appropriate inverter switching state

• Generates six switching pulses

• Controls phase energisation in the correct sequence

• Supports both running and braking modes

Running and braking logic

The switching pulses from the Hall decoder are combined with the operating-mode commands.

Operating condition	Run command	Brake command	System action
Normal operation	Enabled	Disabled	Motor follows the reference speed
Braking operation	Disabled	Enabled	Motor decelerates and returns energy to the battery
Motor stopped	Disabled	Limited or disabled	Regenerative current reduces to zero

This logic prevents running and braking commands from being applied incorrectly at the same time.

Regenerative current controller

During braking, the battery current is measured and processed through a PI controller.

The controller:

• Monitors the charging current

• Compares the measured current with the braking-current reference

• Generates the required braking duty cycle

• Produces controlled PWM pulses

• Regulates the amount of energy transferred to the battery

• Prevents uncontrolled regenerative current

  
  

𝐒𝐢𝐦𝐮𝐥𝐚𝐭𝐢𝐨𝐧 𝐎𝐩𝐞𝐫𝐚𝐭𝐢𝐧𝐠 𝐒𝐞𝐪𝐮𝐞𝐧𝐜𝐞

Simulation period	Operating mode	Motor behaviour	Battery behaviour
0 to 5 seconds	Running	Speed maintained near 3000 rpm	Supplies current to the motor
At 5 seconds	Braking initiated	Motor begins decelerating	Starts receiving recovered energy
After 5 seconds	Regenerative braking	Speed falls toward zero	Charging current becomes negative
End of braking	Motor stopped	Torque and speed approach zero	Regenerative charging ends

𝐒𝐢𝐦𝐮𝐥𝐚𝐭𝐢𝐨𝐧 𝐑𝐞𝐬𝐮𝐥𝐭𝐬

The simulation results confirm the successful operation of the regenerative braking system.

Motor speed response

• The BLDC motor reaches the reference speed of 3000 rpm.

• The controller maintains the speed during the running period.

• Braking is activated at five seconds.

• Motor speed decreases rapidly after the braking command.

• The motor eventually reaches zero speed.

This response confirms the correct transition from driving mode to braking mode.

Electromagnetic torque response

• Positive electromagnetic torque is observed during motor operation.

• Torque becomes negative immediately after regenerative braking begins.

• Negative torque opposes rotor rotation.

• The negative torque indicates that the BLDC motor is operating as a generator.

The torque reversal is one of the main indicators of regenerative braking.

Battery current response

During running mode, the battery supplies current to the electric drive. After braking begins, the battery-current direction changes.

• Positive current represents battery discharge.

• Negative current represents battery charging.

• The negative current confirms reverse energy flow from the motor to the battery.

• Charging current continues while sufficient kinetic energy remains in the motor.

Battery state of charge

The battery state of charge increases slightly during braking because recovered energy is stored in the battery.

Although the increase is small during a short simulation period, it demonstrates the effectiveness of regenerative energy recovery.

Battery voltage response

The battery voltage increases from approximately 71.5 V to 71.6 V during regenerative braking.

This voltage increase occurs because:

• The motor generates electrical energy.

• The generated energy is supplied to the battery.

• The battery temporarily enters the charging state.

DC-bus voltage

The DC-bus voltage changes when the operating mode switches from motoring to braking.

• The converter maintains the required voltage during running mode.

• A voltage variation occurs when regenerative braking starts.

• The recovered energy raises the DC-side voltage.

• The braking controller regulates this energy transfer to the battery.

• 
  

𝐑𝐞𝐬𝐮𝐥𝐭 𝐒𝐮𝐦𝐦𝐚𝐫𝐲

Output parameter	Running mode	Braking mode
Motor speed	Maintained near 3000 rpm	Decreases toward zero
Electromagnetic torque	Positive	Negative
Battery current	Positive discharge current	Negative charging current
Battery state of charge	Slightly decreases or remains nearly constant	Slightly increases
Battery voltage	Approximately 71.5 V	Rises to approximately 71.6 V
Power-flow direction	Battery to motor	Motor to battery
Motor function	Propulsion motor	Electrical generator

𝐊𝐞𝐲 𝐅𝐞𝐚𝐭𝐮𝐫𝐞𝐬

• MATLAB/Simulink implementation of a BLDC motor electric drive

• 500 W, 48 V BLDC motor

• 72 V battery-bank configuration

• Buck converter-based voltage regulation

• PID-based motor speed control

• Hall sensor-based six-step commutation

• Automatic transition between running and braking modes

• PI-controlled regenerative battery current

• Reverse energy flow during braking

• Battery state-of-charge monitoring

• Motor speed, torque, current, voltage, and DC-bus analysis

• Clear demonstration of negative torque and charging current

  
  

𝐁𝐞𝐧𝐞𝐟𝐢𝐭𝐬 𝐨𝐟 𝐑𝐞𝐠𝐞𝐧𝐞𝐫𝐚𝐭𝐢𝐯𝐞 𝐁𝐫𝐚𝐤𝐢𝐧𝐠

Improved energy efficiency

A portion of the energy normally lost during braking is recovered and stored in the battery.

Extended driving range

Recovered energy can support future acceleration and improve the effective driving range of the electric vehicle.

Reduced mechanical brake wear

The electric motor provides part of the braking torque, reducing the continuous use of friction brakes.

Better battery-energy utilisation

Energy stored in the battery is used more efficiently because part of the vehicle’s kinetic energy is recycled.

Smooth braking control

Electronic control allows the braking torque and charging current to be adjusted according to operating requirements.

𝐀𝐩𝐩𝐥𝐢𝐜𝐚𝐭𝐢𝐨𝐧𝐬

This regenerative braking system can be studied or adapted for:

• Battery electric vehicles

• Electric scooters

• Electric motorcycles

• Electric bicycles

• Electric three-wheelers

• Light electric utility vehicles

• Automated guided vehicles

• Electric wheelchairs

• Industrial BLDC motor drives

• Educational electric-drive laboratories

• Motor-control and power-electronics research

• Battery energy-recovery studies

  
  

𝐋𝐞𝐚𝐫𝐧𝐢𝐧𝐠 𝐎𝐮𝐭𝐜𝐨𝐦𝐞𝐬

By studying this model, learners can understand:

• BLDC motor operation in motoring and generating modes

• Electronic commutation using Hall sensor signals

• Six-step voltage source inverter control

• Buck converter duty-cycle regulation

• Closed-loop motor speed control

• Regenerative braking pulse generation

• Battery-current direction during charging and discharging

• Interpretation of speed, torque, voltage, current, and state-of-charge waveforms

• Coordination between propulsion and braking control systems

• Energy flow in an electric vehicle drivetrain

  
  

𝐖𝐡𝐲 𝐓𝐡𝐢𝐬 𝐒𝐢𝐦𝐮𝐥𝐚𝐭𝐢𝐨𝐧 𝐈𝐬 𝐔𝐬𝐞𝐟𝐮𝐥

This model provides a simple and visual method for understanding an advanced electric vehicle concept.

It is especially useful for:

• Students learning MATLAB and Simulink

• Researchers analysing electric vehicle energy recovery

• Engineers developing BLDC motor controllers

• Power-electronics learners studying converters and inverters

• Professionals exploring battery charging during vehicle braking

The model connects theoretical regenerative braking concepts with practical simulation waveforms and control blocks.

𝐂𝐨𝐧𝐜𝐥𝐮𝐬𝐢𝐨𝐧

The regenerative braking model demonstrates how kinetic energy from a rotating BLDC motor can be converted into electrical energy and returned to the battery.

During normal operation, the battery supplies power to the motor, and the speed controller maintains the reference speed at 3000 rpm. When braking is activated at five seconds, the motor speed decreases, electromagnetic torque becomes negative, and the battery current reverses direction.

The increase in battery state of charge and battery voltage confirms that regenerative energy is successfully recovered. Therefore, this MATLAB/Simulink model provides a clear and practical platform for studying BLDC motor control, electric vehicle braking, battery charging, and bidirectional energy flow.