Regenerative braking in bldc motor employing buck converter
Regenerative braking in bldc motor employing buck converter
𝐈𝐧𝐭𝐫𝐨𝐝𝐮𝐜𝐭𝐢𝐨𝐧
Regenerative braking is an important technique used in electric vehicle drive systems to recover part of the kinetic energy that would otherwise be lost during braking.
In this MATLAB/Simulink model, a BLDC motor, battery, buck converter, and voltage source inverter are integrated to demonstrate both normal motoring operation and regenerative braking.
The main idea is simple:
During normal operation, the battery supplies power to the BLDC motor.
The motor speed is regulated at the required reference value.
When braking is activated, the BLDC motor behaves as a generator.
The generated electrical energy flows back toward the battery.
The battery current becomes negative, indicating charging.
Battery state of charge increases slightly because of the recovered energy.
This simulation is useful for students, researchers, and engineers studying BLDC motor control, electric vehicle drives, regenerative braking, power converters, and battery charging systems.
𝐒𝐲𝐬𝐭𝐞𝐦 𝐎𝐯𝐞𝐫𝐯𝐢𝐞𝐰
The regenerative braking system consists of the following main sections:
Battery energy source
Buck converter
DC-link section
Voltage source inverter
BLDC motor
Hall sensor decoder
Six-step commutation control
Speed PID controller
PWM generator
Braking control logic
Battery-current PI controller
Running/braking mode selection
Battery SOC, current, and voltage measurement
System Parameters
Parameter | Value |
Battery configuration | 6-series battery |
Battery rated capacity | 150 Ah |
Initial battery SOC | 50% |
Battery-side voltage | Approximately 72 V |
Motor supply voltage | Approximately 60 V |
BLDC motor rated voltage | 48 V |
BLDC motor rated power | 500 W |
Reference motor speed | 3000 rpm |
Normal running period | 0–5 s |
Braking starting time | 5 s |
Battery voltage before braking | Approximately 71.5 V |
Battery voltage during regenerative charging | Approximately 71.6 V |
𝐁𝐋𝐃𝐂 𝐌𝐨𝐭𝐨𝐫 𝐃𝐫𝐢𝐯𝐞 𝐒𝐭𝐫𝐮𝐜𝐭𝐮𝐫𝐞
The battery is connected to the BLDC motor drive through a buck converter and voltage source inverter.
The basic power-flow arrangement is:
Battery → Buck Converter → DC Link → Voltage Source Inverter → BLDC Motor
The buck converter reduces the battery-side DC voltage to a level suitable for operating the motor drive.
The voltage source inverter then converts the DC-link voltage into the required phase voltages for the BLDC motor.
𝐁𝐮𝐜𝐤 𝐂𝐨𝐧𝐯𝐞𝐫𝐭𝐞𝐫 𝐎𝐩𝐞𝐫𝐚𝐭𝐢𝐨𝐧
The buck converter is mainly responsible for controlling the DC voltage supplied to the motor drive.
Its switching operation is controlled by a PWM signal generated from the speed-control system.
During normal running:
Reference speed is compared with actual BLDC motor speed.
Speed error is supplied to the PID controller.
The PID controller generates the required control command.
The command determines the PWM duty cycle.
PWM pulses drive the IGBT of the buck converter.
The converter regulates the voltage supplied to the inverter.
Motor speed is maintained close to the desired value.
The reference speed used in the model is 3000 rpm.
𝐕𝐨𝐥𝐭𝐚𝐠𝐞 𝐒𝐨𝐮𝐫𝐜𝐞 𝐈𝐧𝐯𝐞𝐫𝐭𝐞𝐫
A voltage source inverter is used between the DC link and BLDC motor.
The inverter performs electronic commutation of the BLDC motor.
Its switching sequence is determined using:
Hall sensor signals
Hall decoder logic
Running command
Braking command
Six-step commutation logic
A total of six gate pulses are generated for controlling the inverter switches.
𝐇𝐚𝐥𝐥 𝐒𝐞𝐧𝐬𝐨𝐫 𝐃𝐞𝐜𝐨𝐝𝐞𝐫 𝐚𝐧𝐝 𝐒𝐢𝐱-𝐒𝐭𝐞𝐩 𝐂𝐨𝐧𝐭𝐫𝐨𝐥
The BLDC motor provides Hall sensor information indicating the rotor position.
These Hall signals are supplied to the Hall decoder.
The controller uses the rotor-position information to determine which inverter switches should conduct.
This provides:
Correct phase energization
Proper electronic commutation
Controlled motor torque
Forward motoring operation
Regenerative braking operation
The same Hall-based control system is integrated with the running and braking commands.
𝐖𝐨𝐫𝐤𝐢𝐧𝐠 𝐏𝐫𝐨𝐜𝐞𝐬𝐬
The simulation operates mainly in two modes.
Mode | Time | Motor Condition | Battery Condition |
Running mode | 0–5 s | Motor operates at approximately 3000 rpm | Battery supplies energy |
Regenerative braking mode | After 5 s | Motor speed decreases toward zero | Battery receives recovered energy |
1. Running Mode
From the beginning of the simulation up to 5 seconds:
The system operates in motoring mode.
The battery supplies electrical power.
The buck converter regulates the motor-side voltage.
The inverter drives the BLDC motor.
Motor speed is controlled at approximately 3000 rpm.
Electromagnetic torque remains positive during normal driving.
2. Braking Mode
At approximately 5 seconds:
Braking command is activated.
Normal running command is disabled.
Inverter switching is changed according to the regenerative braking logic.
Motor electromagnetic torque becomes negative.
Motor speed decreases.
The kinetic energy stored in the rotating motor is converted into electrical energy.
The recovered energy is transferred toward the battery.
𝐂𝐨𝐧𝐭𝐫𝐨𝐥 𝐒𝐭𝐫𝐚𝐭𝐞𝐠𝐲
Two important control loops are used in the simulation.
Speed Control
The speed-control section includes:
Speed reference
Actual motor speed
Speed-error calculation
PID controller
Duty-cycle generation
PWM generator
Buck converter IGBT control
The controller continuously adjusts the buck converter switching to maintain the required motor speed.
Regenerative Braking Control
The braking controller operates using the measured battery current.
The control sequence is:
Battery Current → Current Processing → PI Controller → PWM Generation → Braking Signal → Inverter Control
During braking:
Battery current is monitored.
Current feedback is supplied to a PI controller.
PI controller output determines the braking PWM command.
Braking pulses are combined with Hall sensor commutation signals.
The voltage source inverter is controlled to enable regenerative energy transfer.
𝐑𝐮𝐧𝐧𝐢𝐧𝐠 𝐚𝐧𝐝 𝐁𝐫𝐚𝐤𝐢𝐧𝐠 𝐋𝐨𝐠𝐢𝐜
The control system switches between running and braking operation.
Running condition
Run command = Active
Braking command = Inactive
BLDC motor receives power from the battery.
Motor torque is positive.
Speed is maintained near the reference value.
Braking condition
Run command = Inactive
Braking command = Active
Inverter switching pattern is changed.
BLDC motor operates regeneratively.
Motor torque becomes negative.
Battery receives charging current.
𝐑𝐞𝐠𝐞𝐧𝐞𝐫𝐚𝐭𝐢𝐯𝐞 𝐄𝐧𝐞𝐫𝐠𝐲 𝐅𝐥𝐨𝐰
During acceleration and constant-speed operation, the energy direction is approximately:
Battery → Buck Converter → Inverter → BLDC Motor
During regenerative braking, the energy-flow direction changes to:
BLDC Motor → Voltage Source Inverter → Regenerative Path → Battery
The BLDC motor therefore changes from an electrical load to an electrical energy source during deceleration.
𝐒𝐢𝐦𝐮𝐥𝐚𝐭𝐢𝐨𝐧 𝐑𝐞𝐬𝐮𝐥𝐭𝐬
The MATLAB/Simulink results clearly demonstrate the transition between normal operation and regenerative braking.
Motor Speed
Reference speed: 3000 rpm
Motor operates close to 3000 rpm during the running period.
Braking is initiated at approximately 5 seconds.
Motor speed then decreases rapidly.
The rotor eventually approaches zero speed.
This confirms that the braking controller is successfully decelerating the motor.
Electromagnetic Torque
During normal motor operation:
Electromagnetic torque is positive.
When regenerative braking begins:
Electromagnetic torque becomes negative.
Negative torque produces the required braking action.
The motor converts rotational energy into electrical energy.
The negative torque is therefore an important indication of regenerative braking operation.
Battery Current
The battery-current response clearly identifies charging and discharging behavior.
Operating Condition | Battery Current Behavior | Meaning |
Normal motoring | Positive current | Battery supplies energy |
Regenerative braking | Negative current | Battery receives energy |
During braking, the battery current becomes negative, showing that regenerative energy is being transferred back into the battery.
𝐁𝐚𝐭𝐭𝐞𝐫𝐲 𝐒𝐎𝐂 𝐑𝐞𝐬𝐩𝐨𝐧𝐬𝐞
The initial battery state of charge is:
50%
During normal motoring operation:
Battery supplies the motor drive.
SOC gradually tends to decrease.
During regenerative braking:
Charging current flows toward the battery.
Battery SOC increases slightly.
The SOC rise confirms successful recovery of braking energy.
Because braking occurs only for a short duration, the SOC increase is naturally small.
𝐁𝐚𝐭𝐭𝐞𝐫𝐲 𝐕𝐨𝐥𝐭𝐚𝐠𝐞 𝐑𝐞𝐬𝐩𝐨𝐧𝐬𝐞
The battery voltage also provides evidence of regenerative charging.
Condition | Battery Voltage |
Before regenerative braking | Approximately 71.5 V |
During regenerative charging | Approximately 71.6 V |
The slight increase in voltage is associated with the short charging interval during regenerative braking.
𝐑𝐞𝐬𝐮𝐥𝐭 𝐒𝐮𝐦𝐦𝐚𝐫𝐲
Parameter | Normal Running | Regenerative Braking |
Motor speed | Approximately 3000 rpm | Decreases toward zero |
Motor torque | Positive | Negative |
Battery current | Positive | Negative |
Battery SOC | Slowly decreases | Slightly increases |
Battery power flow | Battery to motor | Motor to battery |
Motor operation | Motoring | Generating |
Energy direction | Forward | Reverse toward battery |
𝐊𝐞𝐲 𝐅𝐞𝐚𝐭𝐮𝐫𝐞𝐬
BLDC motor regenerative braking simulation
Buck-converter-based motor voltage control
Six-step inverter operation
Hall sensor-based electronic commutation
PID-based BLDC speed regulation
PI-based regenerative current control
Automatic running and braking mode switching
Battery charging during deceleration
Battery SOC monitoring
Battery current monitoring
Battery voltage monitoring
Motor torque analysis
Rotor-speed analysis
Regenerative energy recovery
MATLAB/Simulink-based implementation
𝐖𝐡𝐲 𝐑𝐞𝐠𝐞𝐧𝐞𝐫𝐚𝐭𝐢𝐯𝐞 𝐁𝐫𝐚𝐤𝐢𝐧𝐠 𝐢𝐬 𝐔𝐬𝐞𝐟𝐮𝐥
Traditional braking systems convert much of the vehicle's kinetic energy into heat.
Regenerative braking allows part of this energy to be recovered.
The main benefits include:
Improved energy utilization
Reduced energy loss during braking
Partial battery recharging
Improved electric-drive efficiency
Reduced dependence on mechanical braking
Better utilization of stored battery energy
Improved understanding of bidirectional energy flow in electric vehicles
𝐀𝐩𝐩𝐥𝐢𝐜𝐚𝐭𝐢𝐨𝐧𝐬
This type of control concept can be studied for:
Electric vehicles
Electric scooters
Electric motorcycles
Battery-powered transportation systems
BLDC motor drives
Electric traction systems
Energy-efficient motor drives
Battery energy recovery systems
Regenerative braking control research
Power-electronic converter studies
Advanced EV drive-control development
𝐖𝐡𝐚𝐭 𝐂𝐚𝐧 𝐁𝐞 𝐒𝐭𝐮𝐝𝐢𝐞𝐝 𝐅𝐫𝐨𝐦 𝐓𝐡𝐢𝐬 𝐌𝐨𝐝𝐞𝐥?
The simulation helps users understand:
How a BLDC motor is electronically commutated
How Hall sensors control inverter switching
How a buck converter regulates motor voltage
How a PID controller regulates motor speed
How regenerative braking creates negative torque
How battery current changes during charging
How SOC responds to recovered braking energy
How motor kinetic energy can be recovered
How running and braking logic can be integrated
How MATLAB/Simulink can be used to analyze an EV motor drive
𝐂𝐨𝐧𝐜𝐥𝐮𝐬𝐢𝐨𝐧
The regenerative braking in BLDC motor employing buck converter simulation demonstrates effective energy recovery during motor deceleration.
During the first 5 seconds, the BLDC motor operates at approximately 3000 rpm under normal running conditions. When the braking command is activated, the motor speed decreases, electromagnetic torque becomes negative, and regenerative energy is transferred back to the battery.
The negative battery current confirms charging operation, while the small increase in battery SOC and voltage demonstrates successful regenerative energy recovery.
The model provides a clear platform for understanding BLDC motor control, buck converter operation, six-step inverter switching, Hall sensor commutation, battery charging, and regenerative braking in electric vehicle drive systems.
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