Good day, I want to develop a multi-input bidirectional non-isolated converter interfacing a battery and a supercapacitor to supply a desired current value and desired voltage

Therefore, how can i develop this system with a simple PID controller to regulate the output voltage and current? In addition, keeping the sources state of charge within the desired limits?

Answer 1

[Sayan]

Hi Mpho Lencwe,

I understand from your query that it is required to integrate a battery and a supercapacitor in parallel to run the load with regulated voltage and current using a bidirectional converter to feed the load while maintaining the state of charge of the source within a certain limit.

You can build the model in many ways according to the design logic you need to maintain. One of the possible design models is demonstrated as follows:

• Use the Battery (available at Simscape / Electrical / Specialized Power Systems / Sources) and Supercapacitor (available at Simscape / Electrical / Specialized Power Systems / Sources) blocks to and configure their parameters according to your design requirements.
• If it is required to use only one bidirectional converter, you can connect both sources in parallel prior to connecting them to the converter; otherwise, two converters can be used for the two sources, after which they can be connected in parallel to feed the load.
• Build the bidirectional converter using two controlled switch blocks, like the Mosfet block (available at Simscape / Electrical / Specialized Power Systems / Sources).
• Build the logic according to which you need to charge and discharge the sources within a certain limit of their state of charge while maintaining the current and voltage that they supply.
• Use the PID Controller block (available at Simulink / Continuous) to reduce the error between the reference voltage or current and the actual voltage and current generated. The output of the PID controller defines the duty cycle of PWM pulses with which the switches will be operated. Provide complementary pulses to the switches to charge or discharge the sources at a time.
• The PWM Generator block (available at Simscape / Electrical / Control / Pulse Width Modulation) can be used after the PID Controller block to generate PWM pulses.
• The logic will be used to generate the PWM pulses for the switches of the bidirectional converter. You can follow this example from File Exchange which implements a battery model with a bidirectional conveter. Here, a battery model with a bidirectional converter is used to charge or discharge the battery. You can extend the logic for the supercapacitor too.

https://www.mathworks.com/matlabcentral/fileexchange/92458-battery-controller-design-bidirectional-dc-dc-converter

You can find more information on the Battery , Supercapacitor, PID Controller and PWM Generator blocks in the following documentation:

• Battery: https://www.mathworks.com/help/sps/powersys/ref/battery.html
• Supercapacitor: https://www.mathworks.com/help/sps/powersys/ref/supercapacitor.html
• PID Controller: https://www.mathworks.com/help/simulink/slref/pidcontroller.html
• PWM Generator: https://www.mathworks.com/help/sps/ref/pwmgenerator.html

Hope this helps in answering the query.

[Mpho Lencwe]

Thank you very much @Sayan