Design and simulation of Bidirectional DC-DC buck and boost with Battery Control in MATLAB/Simulink

Introduction

This tutorial guides you through the design and simulation of a bidirectional DC-DC buck and boost converter with battery control using MATLAB/Simulink. Understanding this process is essential for applications in renewable energy systems, electric vehicles, and power management solutions, where efficient power conversion is required.

Step 1: Setting Up MATLAB/Simulink

• Open MATLAB and create a new Simulink model.
• Go to the Simulink Library Browser and locate the required blocks:
  • Power Electronics
  • Sources
  • Sinks
• Drag and drop the blocks needed for the buck and boost converter into your model.

Step 2: Designing the Converter Circuit

• Buck Converter Configuration:

  • Add a voltage source to represent the input voltage.
  • Insert a MOSFET switch, diode, and inductor in series with the load.
  • Connect a capacitor across the output for voltage smoothing.

• Boost Converter Configuration:

  • Use the same voltage source.
  • Position the MOSFET switch, diode, and inductor appropriately to create a step-up configuration.
  • Again, place a capacitor across the output.

Step 3: Implementing Control Strategy

• Incorporate a control system using:

  • Proportional-Integral (PI) controller for voltage regulation.
  • Feedback from the output voltage to adjust the duty cycle of the MOSFET.

• Use the following code snippet to define the PI controller in MATLAB:

  Kp = 1; % Proportional gain
  Ki = 0.1; % Integral gain
  

• Ensure the controller is connected to the MOSFET gate to modulate its operation based on feedback.

Step 4: Adding Battery Control

• Integrate a battery model to simulate energy storage:

  • Use the battery block from the Simulink library.
  • Define the battery characteristics, such as capacity and state of charge (SOC).

• Connect the battery to the output of the converters, ensuring proper switching between charging and discharging modes based on SOC.

Step 5: Simulation Configuration

• Set up simulation parameters:

  • Choose an appropriate time span for the simulation.
  • Select a suitable solver to ensure stability and accuracy (e.g., ode45).

• Run the simulation and observe the output voltage and current waveforms.

Step 6: Analyzing Results

• Use scopes to visualize the results:

  • Check the output voltage for both buck and boost operations.
  • Analyze how efficiently the battery is charged and discharged.

• Make adjustments to the control parameters if necessary to optimize performance.

Conclusion

You have now designed and simulated a bidirectional DC-DC buck and boost converter with battery control in MATLAB/Simulink. Key points include the importance of proper circuit configuration, implementing a robust control strategy, and optimizing the battery management system. For further exploration, consider experimenting with different control algorithms or testing under varying load conditions to enhance your understanding and application of power electronics.