Comparing proportional-resonant and fuzzy-logic controllers for current controlled single-phase grid-connected PWM DC/AC inverters

Conventional PI controllers are usually used in single-phase grid-connected dc/ac inverters for photovoltaic plants. These PI controllers suffer from two major drawbacks; steady-state errors in case of sinusoidal reference signals besides their limited disturbance rejection capability. To overcome these shortcomings proportional-resonant (PR) and fuzzy-logic controllers are investigated and then compared with the conventional PI controller. The ability of the PR controller through introducing an infinite gain at a resonance frequency is analysed. The design of the PR-controller is investigated and steps for tuning the controller are given in this work. Moreover, a fuzzy-logic PI(FPI-) controller is also designed and its performance is evaluated with respect to the PIand PR-controllers. A simulation-based analysis is used to investigate the novel comparison between the PR-and FPI-controllers where the controllers´ performance is evaluated and compared regarding: transient and steady-state characteristics as well as total harmonic distortion (THD). The analysis showed excellent behaviour of the investigated controllers to overcome the Pi-controller related shortcomings. The FPI-controller showed better transient and disturbance rejection capabilities, while the PR-controller exhibited excellent steady-state characteristics.