Regenerative braking in bldc motor employing buck converter
Introduction to the Simulink Model
The simulation model is designed to represent the regenerative braking system in an electric vehicle powered by a BLDC motor. Key components of this model include:
Battery: A 6-series battery pack with a rated capacity of 150 Ah, initially charged to 50%.
Converter: A buck converter to step down the battery voltage.
Voltage Source Inverter: Converts DC to AC to power the BLDC motor.
BLDC Motor: A 500-watt motor, rated at 48 volts, used to drive the electric vehicle.
Hall Sensor and Decoder: Used to measure the rotor position of the BLDC motor.
Control Logic: Generates pulses for the inverter to control motor operation.
Regenerative Braking Logic: Manages the energy feedback from the motor to the battery during braking.
Simulation of Regenerative Braking
The simulation starts with the vehicle operating under normal running conditions. During this period:
Motor Operation: The BLDC motor operates at a constant speed of 3000 RPM, drawing power from the battery.
Speed Control: A PID controller is used to maintain the motor speed by adjusting the duty cycle of the converter.
Energy Flow: The battery supplies power to the motor through the converter and inverter.
At the five-second mark, the simulation applies the braking command:
Kinetic Energy Conversion: As the vehicle slows down, the motor’s kinetic energy is converted back into electrical energy.
Battery Charging: This energy is fed back through the inverter and the converter, and it recharges the battery.
Torque Reversal: The motor torque becomes negative, indicating that energy is being regenerated rather than consumed.
Observations from the Simulation
The simulation provides several key insights:
Battery State of Charge (SOC): During braking, the SOC of the battery increases due to the regenerative energy.
Battery Current: The current becomes negative, which signifies that the battery is being charged rather than discharged.
Motor Speed and Torque: The motor speed decreases to zero as the vehicle comes to a stop, while the torque becomes negative during braking, showing energy regeneration.
Conclusion
Regenerative braking is a vital technology in electric vehicles, allowing them to reclaim energy that would otherwise be lost during braking. This energy is used to recharge the battery, thereby extending the range of the vehicle and improving overall efficiency.
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