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Closed loop control of fuel cell with boost converter

Closed loop control of fuel cell with boost converter


Introduction

We will cover how to set up a fuel cell in MATLAB, design a boost converter, and implement a closed-loop control system. This is particularly useful for applications requiring stable and efficient power delivery from a fuel cell.



Setting Up the Fuel Cell

First, let's set up the fuel cell in MATLAB:

  1. Fuel Cell Specification:

  • We are using a proton exchange membrane (PEM) fuel cell with a rating of 1.26 kW and 24V.

  • Apply the settings and review the voltage-current (V-I) characteristics of the fuel cell.

  1. Power and Voltage Calculations:

  • The nominal power is 1.26 kW, but we will design the boost converter for a maximum of 2 kW.

  • The fuel cell operates at around 20V when delivering maximum power.



Designing the Boost Converter

To design the boost converter, we need to determine the values for inductance (L), capacitance (C), and resistance (R). Here are the steps:

  1. Input Parameters:

  • Input voltage: 20V

  • Switching frequency: 10 kHz

  • Desired output voltage: 48V

  1. Calculations:

  • Use appropriate formulas to calculate the maximum inductor current ripple, voltage ripple, and select L and C values accordingly.

  • Ensure the design can handle up to 2 kW, even though the fuel cell will typically operate at 1.26 kW.

  1. Component Selection:

  • Use MATLAB functions to specify values for inductors, capacitors, IGBTs, and diodes.

  • Implement these components in the boost converter circuit.

Implementing the Control System

To maintain a stable output voltage, we need a feedback control system:

  1. PID Controller Setup:

  • Implement a PID controller to regulate the output voltage.

  • The reference voltage is set to 48V.

  1. Simulation:

  • Simulate the model without initial tuning to observe the system response.

  • Tune the PID controller using MATLAB’s PID tuning tools for optimal performance.

  • Simulate again to verify improved performance.

Tuning the PID Controller

To achieve desired performance, tune the PID controller:

  1. Initial Setup:

  • Use MATLAB's built-in PID tuner.

  • Simulate with initial duty cycles to collect response data.

  1. Data Identification:

  • Collect identification data from the system’s response.

  • Estimate the plant model based on the collected data.

  • Adjust parameters to match the desired response.

  1. Final Tuning:

  • Update the PID controller with the tuned parameters.

  • Verify the system's response with the updated settings.

Simulation Results

After tuning the PID controller, observe the following results:

  1. Output Voltage:

  • The output voltage should stabilize at 48V.

  • Monitor the settling time and ensure minimal overshoot.

  1. Current and Power:

  • Review the input and output current, ensuring the fuel cell operates efficiently.

  • Confirm the power delivered matches the design specifications.

  1. System Stability:

  • Check for any oscillations or instability in the output.

  • Fine-tune if necessary to achieve smooth and stable performance.

Conclusion

This tutorial demonstrated the closed-loop control of a fuel cell using a boost converter. By carefully designing the converter and tuning the PID controller, we can achieve a stable and efficient power supply. This method is crucial for applications where consistent power output from a fuel cell is required.

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