Previously i have worked on Backstepping control for Two Stage Grid connected PV Inverter in which i used PI controller for DC-Link Voltage as can be seen in attached picture. Now I want to implement Fuzzy Control instead of PI control but the dc-link voltage constantly increases no matter what i do. Can any one share experience who has worked on PV inverters or atleast fuzzy logic control.
Keeping in mind that the DC Voltage Controller is used to regulate DC-Link (Cdc) voltage and generate a reference signal which multiplies with grid signal to generate a reference current for grid current controller regulation and synchronization.
Hi Shah,
There are various reasons your fuzzy controller could lead to the undesired outcome. One possibility is that the fuzzy controller is relatively slow to respond to the voltage error.
If the DC-link voltage has been successfully controlled with a PI controller, then the control strategy is to use the PI controller as a baseline for the fuzzy control design. In other words, you should make the PI controller to become a Fuzzy PI controller.
Thank you yew-chung. If you remember any paper having design details of fuzzy-pi for dc_link voltage then plz share it with me.
Another thing is that the input error and output of PI is enough data to design fuzzy membership functions ? What is the best way to find this input output information may be i am mistaken here.
Hi Shah,
Since you are already familiar with PI controller, you should stick with what you are good at and find ways to improve the PI control performance.
If you think your PI controller is not robust enough, then you can design multiple PI controllers and develop the PI gain scheduling using fuzzy logic. You may also implement the adaptive fuzzy PI controller to handle sudden changes of the active power drawn by the Grid connected PV Inverter.
Regarding the fuzzy PI controller for DC-link voltage control, you could try searching that on IEEE Xplore and ScienceDirect. But I doubt that you'll find the detailed design other than the standard membership functions, fuzzy rules, and defuzzification methods. To increase the chances of finding a good paper on fuzzy PI control, you shouldn't limit the search on DC-link voltage control only.
Good luck!
Thank You so much Yew-Chung for such informative replies. Your suggestions are duly noted.
For gain scheduling of PID controller you may refer to the following paper:
http://ieeexplore.ieee.org/document/8279151/
A modified PID control with adaptive fuzzy controller applied to DC motor
The fuzzy logic rule table you used, is it from literature or developed by your self?
Elyazid Amirouche Thank you for your comment. However, I am not working on this project.
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