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Boost with PID controlled output voltage

A voltage mode boost converter regulates voltage by comparing the output voltage to a reference voltage. It adjusts the duty cycle of its switching signal to keep the output voltage stable. This type of converter efficiently steps up voltage levels, making it useful in various electronic devices such as converting photovoltaic panel voltage.

This example will implement a voltage mode boost converter to control the output.

Hardware setup and requirement

The circuit diagram of the board is shown in the image below.

circuit diagram
Figure 1: circuit diagram

The power flows from V1Low to V_high. The wiring diagram is shown in the figure below.

wiring diagram
Figure 2: wiring diagram

You will need : - 1 TWIST - A dc power supply (max 10V) - A resistor (or a dc electronic load)

Software setup and structure

The example is built using the main.cpp file and the control library.

Main code structure

The main.cpp structure is shown in the image below.

Code structure
Figure 3: Code structure

The code structure is as follows: - On the top of the code some initialization functions take place. - Setup Routine - calls functions that set the hardware and software - Communication Task - Handles the keyboard communication and decides which MODE is activated - Application Task - Handles the MODE, activates the LED and prints data on the serial port - Critical Task - Handles the MODE sets power ON/OFF and track the V_high variable with a PID

The tasks are executed following the diagram below.

Timing diagram
Figure 4: Timing diagram

  • Communication Task - Is waken regularly to verify any keyboard activity
  • Application Task - This task is woken once its suspend is finished
  • Critical Task - This task is driven by the HRTIM count interrupt, where it counts a number of HRTIM switching frequency periods. In this case 100us, or 20 periods of the TWIST board 200kHz switching frequency set by default.

Control scheme

The control library is imported in platformio.ini via the line :

lib_deps=
    control_lib = https://github.com/owntech-foundation/control_library.git

We can use this library to initialize a PID control with the function :

pid.init(pid_params);

The control diagram of the PID is shown in the figure below.

Control diagram
Figure 5: Control diagram

Expected result

This code will control the output voltage to have 15V, you can control the output voltage with the serial monitor :

  • press u to increase the voltage reference by 0.5V
  • press d to decrease the voltage reference by 0.5V

The following plot shows the expected result. Here the voltage reference was modified and V_High can be seen to follow it. Both currents are negative, as the current measurement I_High is in the load convention and the current measurement I1_low is in source convention.

Expected result
Figure 6: Expected result