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Design of Buck-Boost converter with PID controller

Design of Buck-Boost converter with PID controller

Introduction to Buck-Boost Converter Design

We'll begin by designing the LC components for the buck-boost converter. The following parameters are considered for our 250-watt converter:

  • Input Minimum Voltage: 27V

  • Input Maximum Voltage: 32V

  • Operating Voltage: 30.7V

  • Output Voltage: -12V

  • Output Current: Determined by the formula P/VoutP/V_{\text{out}}P/Vout​

  • Switching Frequency: 10 kHz

  • ESR (Equivalent Series Resistance) for Input and Output Capacitors

Simulink Model Creation

  1. DC Voltage Source: Set to 30.7V.

  2. IGBT-Diode Combination: Used as the electronic switch.

  3. Series RLC Branch: Representing the inductor.

  4. Diode and Capacitor: For rectification and filtering.

  5. Load Resistor: Calculate the value based on power and voltage.

  6. PWM Generator: Generates the switching signal with a duty cycle of 0.307.

  7. Voltage and Current Measurement Blocks: To monitor output voltage and current.

Assembling the Model

Connect all components to form the buck-boost converter circuit. Ensure proper connections and parameter settings for each component.

PID Controller Implementation

To maintain a stable output voltage, we employ a PID controller. Here's how to tune and integrate the PID controller:

  1. Summing Block: Compare the actual output voltage with the reference voltage (-12V).

  2. PID Controller Block: Configure it as a PI controller for this application.

  3. Tuning the PID Controller:

  • Use the PID Tuner in MATLAB to identify the system response.

  • Simulate the model with initial and final duty cycles to collect identification data.

  • Apply the identified data to tune the controller automatically.

Simulation and Results

After tuning the PID controller, simulate the model to observe the output voltage regulation. The system should maintain the output at -12V with minimal ripple.

Step Response Testing

To test the response of the PID controller to changes in reference voltage:

  1. Step Block: Change the reference voltage from -12V to -10V after 5 seconds.

  2. Monitor the System: Ensure the PID controller adjusts the output voltage accordingly.

The simulation should demonstrate the system's ability to maintain the desired output voltage, even with changes in reference input.

Conclusion

Designing a buck-boost converter with a PID controller involves careful calculation of component values and precise tuning of the controller. By following this process, we can achieve a stable and efficient power conversion system.

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