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.

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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.