Dynamic maximum power point tracking and robust voltage regulation for photovoltaic systems

Kahani, Rasool (2023) Dynamic maximum power point tracking and robust voltage regulation for photovoltaic systems. Masters thesis, Memorial University of Newfoundland.

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Abstract

This research proposes a Maximum Power Point Tracking (MPPT) and voltage regulation method based on model reference adaptive control (MRAC). The MPPT algorithm which is presented in this work is a modified perturb and observe (P&O) algorithm. The new algorithm prevents oscillation around maximum power point (MPP) by approximating the peak of photovoltaic (PV) array power curve. This goal is achieved by comparing the change in output power during each cycle with change in array terminal power during the previous cycle. When array terminal power decreases following an increase in the previous cycle or the opposite, a decrease in array terminal power is followed by an increase, it means the power curve has reached its peak. Therefore, the duty cycle of the boost converter should remain the same. When irradiance changes, the proposed technique produces an MPPT algorithm's average efficiency ( MPPT  ) of nearly 3.1 percent greater than the conventional P&O and the Incremental conductance (InC) algorithm. In addition, under strong partial shading conditions (PSC) and drift avoidance tests, the proposed technique produces an average MPPT  of nearly 9 percent and 8 percent greater than the conventional algorithms, respectively. To inject the generated PV power into the grid with high quality, this work designs voltage regulation controller based on MRAC to ensure the output voltage of the PV system is at the desired level. To achieve this goal, we propose a DC–DC boost converter that stabilizes output voltage variations by using MIT rule controllers. An output voltage is stabilized using two control loops, PID controllers are capable of regulating output voltage at fixed levels, and for the outer loop, it's intended to implement the direct model reference adaptive controller (DMRAC) MIT rule. In comparison with DC–DC boost converters connected to the micro-grid (MG), the controller presented here, manages disturbances and unknown parameter fluctuations more effectively. The proposed controller and the model are tested in MATLAB/SIMULINK for load disturbances. The load was changed by ~50% of its original value, and the worst-case settling time and maximum overshoot were less than ~0.1 s and 0.5 V (0.3%), respectively. Comparison with the PID methods, the lowest overshoot among three different PID tuning methods, namely the Ziegler–Nichol’s frequency-domain method, damped oscillation method, and Good Gain method, is 34%. Therefore, it is evident from results that the proposed algorithm has better performance in dealing with the maximum overshoot issues. The hardware validation is also carried out to show the performance of the proposed controller.

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