PID tuning for Inverter Control

Hi, I am trying to simulate a Grid connected PV System. Right now, I am working on optimising the Current Control Inner Loop and am unable to tune the PI values for the system using the PID tuner block.

For this, I have disconnected the DC/DC Converter and replaced it with a 400V DC Voltage Source. The source is connected to the Inverter, then Filter followed by the Grid.

I have used the Matlab block for PLL.

Everytime I try to use the tune function it puts up an error that the plant cannot be linearized. Can someone please help me to understand what I may be doing wrong.

Answer 1

[Yoshi Minagawa]

Hi Rainy,

Normally, for discontinuous systems like those found in power electronics—where the system's behavior switches discontinuously due to semiconductor switching—the PID Controller block cannot be used for automatic tuning. Instead, you can do the frequency response estimation (FRE) to obtain the characteristics of the plant, and then design a PID controller based on that.

Specifically, you can perform FRE to obtain the plant model’s FRD data, and use this data directly in the PID tuner to design your PID controller. Alternatively, you can use commands like tfest to first identify a transfer function and then design the PID controller.

For more information on FRE, please refer to the following site:

https://www.mathworks.com/help/slcontrol/offline-frequency-response-estimation.html

For methods on designing PID controllers using FRD (frequency response) data, the following site will be helpful:

https://www.mathworks.com/help/slcontrol/ug/design-pid-controller-from-plant-frequency-response-data.html