Incremental resistance MPPT algorithm with proportional integral compensator for extended DC-DC buck-boost converter in PV systems

Photovoltaic (PV) power output is significantly influenced by environmental and climatic variables, such as the sun's irradiance, air humidity, and ambient temperature. In addition, most PV power sources have relatively small output voltages not suited for direct utilization by common loads. Additionally, PV power output depends also on the PV operating voltage and current. In this sense, a maximum power point tracking (MPPT) algorithm is required to achieve maximum power output and improved efficiency in PV systems. Due to shadowing or fast irradiance changes, MPPT algorithms must operate at high speed and accuracy. Thus, this paper proposes a MPPT control strategy based on incremental resistance (INR) combined with a proportional-integral (PI) compensator (INR-PI). This approach modifies the seldom used INR MPPT algorithm to set the current and combines it with a proportional-integral compensator to regulate the I-V operating point of the PV panel. This reformulates the INR principle as a PV panel voltage regulation problem ensuring closed-loop stability and disturbance rejection. The theoretical analysis considers the dynamics of the input current in a quadratic Buck-Boost converter with an extended duty-cycle range in the Buck voltage region, connected to a DC microgrid. The proposed MPPT technique is designed to ensure fast and efficient operation of PV systems under rapidly changing environmental conditions. To validate this control system, initial simulations were conducted using MATLAB/Simulink, followed by experimental testing with a laboratory prototype setup. Both numerical and experimental results demonstrate the effectiveness of the feedback-based incremental resistance algorithm in tracking the maximum power point (MPP) of PV systems when irradiance fluctuates quickly.