Hello, My topic is the transformation of a DC power supply into AC power by means of a three-phase inverter PWM control. It is then filtered through an LCL filter and finally connected to a three-phase AC grid. The equation of state here is established by the LCL filter, where the control variable u is the voltage on the inverter side obtained by PWM control, so that Uin = (Udc/2)*u, with u taking values of only 1 or -1. How do I achieve this limit?
I look forward to your reply, thank you!
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I don't think that you can model variables with a discrete value set in GRAMPC. I would approach the problem by formulating the control as a continuous variable, which is realized via PWM when applying the MPC solution to the plant. Or is it really necessary to include the switching PWM dynamics in the MPC formulation?
Best regards,
Andreas Völz
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Hello Andreas Völz ,
Thank you very much for your reply. My previous control variable u is as you said, u is the reference voltage obtained by MPC solution and then the input voltage on the inverter side is obtained by PWM. My goal was to achieve power control on the grid side. But my simulation results have less than 10% error with the desired power. I am therefore considering whether it would be more accurate to use the PWM modulated voltage directly as the control variable.
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as I have said, I don't know an approach for handling discrete-valued control variables in GRAMPC. Would it be possible to keep a continuous-valued control, but still include the effects of the PWM in the dynamics or cost function? Besides, are you sure that the "errors" are really caused by the neglected PWM in the MPC formulation?
Best regards,
Andreas Völz
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
Hello, My topic is the transformation of a DC power supply into AC power by means of a three-phase inverter PWM control. It is then filtered through an LCL filter and finally connected to a three-phase AC grid. The equation of state here is established by the LCL filter, where the control variable u is the voltage on the inverter side obtained by PWM control, so that Uin = (Udc/2)*u, with u taking values of only 1 or -1. How do I achieve this limit?
I look forward to your reply, thank you!
Dear Zhidong Guo,
I don't think that you can model variables with a discrete value set in GRAMPC. I would approach the problem by formulating the control as a continuous variable, which is realized via PWM when applying the MPC solution to the plant. Or is it really necessary to include the switching PWM dynamics in the MPC formulation?
Best regards,
Andreas Völz
Hello Andreas Völz ,
Thank you very much for your reply. My previous control variable u is as you said, u is the reference voltage obtained by MPC solution and then the input voltage on the inverter side is obtained by PWM. My goal was to achieve power control on the grid side. But my simulation results have less than 10% error with the desired power. I am therefore considering whether it would be more accurate to use the PWM modulated voltage directly as the control variable.
Dear Zhidong Guo,
as I have said, I don't know an approach for handling discrete-valued control variables in GRAMPC. Would it be possible to keep a continuous-valued control, but still include the effects of the PWM in the dynamics or cost function? Besides, are you sure that the "errors" are really caused by the neglected PWM in the MPC formulation?
Best regards,
Andreas Völz