Model Predictive Control of Boost Converter

Summary

This video provides an in-depth guide on designing a Model Predictive Control (MPC) system for a boost converter, with a focus on controlling inductor current and output voltage. The process includes system modeling, using Euler's method for current prediction, and creating a cost function to minimize error. The video walks through MATLAB/Simulink code implementation, optimization of switching frequency, and tuning of a PI controller. It highlights the balance between switching frequency and control accuracy, offering practical insights for real-world applications of MPC in power electronics.

Takeaways

• 😀 The video demonstrates how to design a Model Predictive Control (MPC) for a Boost Converter, focusing on input current or output voltage control.
• 😀 A key system parameter needed for MPC is the derivative equation of the converter, which includes the inductor current.
• 😀 Euler's forward method is used to approximate the prediction of the control variable (inductor current) in the MPC.
• 😀 The boost converter has two possible switching states (S1 = 1 or 0), and the system model changes depending on these states.
• 😀 The inductor voltage is derived differently depending on whether the switching state is on or off, affecting the derivative equation for the inductor current.
• 😀 The design utilizes MATLAB Simulink to model the predictive control function and implement the control algorithm for the Boost Converter.
• 😀 A cost function (G) is defined as the absolute error between the reference inductor current and the predicted value, which is minimized during control.
• 😀 The algorithm iterates over possible switching states to minimize the error and determine the optimal switching state for the Boost Converter.
• 😀 To reduce switching frequency, a modified cost function is introduced, adding an additional factor that controls the switching position frequency.
• 😀 The video also covers the design of an output voltage controller using a PI controller to generate a reference inductor current based on the output voltage error.

Q & A

What is the main control variable used in the Boost converter design in this video?

The main control variable used in the design is the inductor current, which is critical for controlling the behavior of the Boost converter.

What is the role of Euler's method in the Model Predictive Control (MPC) design?

Euler's method is used to approximate the derivative of the inductor current in the prediction function of the MPC, helping to estimate future inductor current values.

How does the Boost converter model change depending on the switching state?

The Boost converter's behavior differs between two switching states: when the switch is 'ON' (S = 1), the inductor voltage is the difference between the input voltage and the voltage drop across the inductor resistance. When the switch is 'OFF' (S = 0), the inductor voltage follows a different equation, depending on the circuit configuration.

What is the purpose of the cost function in Model Predictive Control (MPC)?

The cost function in MPC minimizes the error between the reference inductor current and the predicted inductor current. It allows the controller to select the optimal switching state that leads to the smallest error.

Why is the error minimized in the MPC design?

Minimizing the error ensures that the predicted inductor current aligns closely with the reference value, which improves the overall accuracy of the Boost converter's performance.

How is the optimal switching state determined in the MPC algorithm?

The optimal switching state is determined by evaluating all possible switching states (S = 1 or S = 0) and selecting the one that results in the smallest error in the cost function. This process is done through a minimization loop.

What challenges are addressed when adjusting the switching frequency in this design?

The design initially encountered high switching frequencies that were not acceptable for real applications. To solve this, a modified cost function was introduced to reduce the switching frequency by keeping the switching state constant when the error is within an acceptable range.

What is the function of the PI controller in output voltage control for the Boost converter?

The PI controller generates a reference inductor current based on the output voltage error. This indirectly controls the output voltage by adjusting the inductor current to match the desired voltage.

How is the dynamic response of the system evaluated in this video?

The dynamic response is evaluated by changing the reference inductor current and observing how quickly the system adjusts. The response is tested by modifying the reference current and checking if the controller can handle the transition smoothly.

Why is manual tuning of the PI controller used in this design, and what does it achieve?

Manual tuning of the PI controller is used to optimize its dynamic response by adjusting the proportional and integral gains (Kp and Ki). This helps reduce overshoot and undershoot in the system, achieving a more stable and accurate response to changes in the output voltage.