Small-Signal Modeling and Voltage PID controller-Synthesis for Cascade Regulation of Renewable Energy Conversion System

Improved P&O-MPPT strategy based on new design of small-signal model used for voltage regulation of solar

“…11), while the second one including the remaining 2500 samples are used to validate the linear small signal model. According to several previous works [13,5,11], the transfer function-based model having three poles and one zero, i.e., 𝛿𝐺(𝑠) = 𝑡𝑓 13 , has been mostly used to describe the actual behavior of the solar system. In general, its determination required applying the small signal principle, using either analytical methods [13,11] or graphical methods [5].…”

“…According to several previous works [13,5,11], the transfer function-based model having three poles and one zero, i.e., 𝛿𝐺(𝑠) = 𝑡𝑓 13 , has been mostly used to describe the actual behavior of the solar system. In general, its determination required applying the small signal principle, using either analytical methods [13,11] or graphical methods [5]. Both types of methods are very promising, especially when the solar system includes a perfect DC-DC boost converter (as the one given in Appendix A) as well as when the I-V characteristics of the PV panels used are slightly nonlinear.…”

“…where 𝑘 𝑑𝑐 is the transfer function gain of the linear small signal model where this last one includes 𝑚 zeros 𝑧 𝑖 and 𝑛 poles 𝑝 𝑖 where 𝑚 ≤ 𝑛. According to several previous works [13,5,11,12], the tuning success of the controller-parameters depends mainly on the model accuracy, given from modeling the actual solar system behavior at STC [14]. Unfortunately, it is quite rare to find a perfect linear model in most real-world applications due several reasons.…”

“…Therefore, Fig. 2 shown the flowchart of the P&O algorithm, used to compute the optimal duty cycle control for the solar system that operated under varying weather conditions [13,5].…”

“…As a result, Fig. 4 shows the closed loop system that interconnects the linear small-signal model, assumed here by 𝛿𝐺(𝑠), by the corresponding voltage PID controller, assumed here by 𝛿𝐾(𝑠) using the modified P&O algorithm [13]. Here, the transfer function of the voltage controller that associates the output of the duty cycle control variation 𝛿𝛼 with the input of the voltage variation error ∆𝑣 is given by…”