Researchers from China’s Shenyang Agricultural University have developed a novel maximum power point tracking (MPPT) technique for PV systems operating under partial shading.
Their new method is an improvement of the RIME optimization algorithm that imitates the developmental course of hoarfrost in nature. Their improved RIME (IRIME) algorithm was demonstrated and compared against two other algorithms – particle swarm optimization (PSO)-MPPT and RIME-MPPT.
“The study of IRIME-MPPT provides new solutions for the optimal operation of PV systems. The proposed method swiftly adapts to environmental fluctuations and identifies the maximum power point (MPP) in a short time,” the academics said. “It exhibits adaptive regulatory attributes, promptly stabilizing its state and significantly mitigating fluctuations in the vicinity of the MPP within PV systems, thereby enhancing the steadiness of the system. Besides, the algorithm possesses strong global and local search capabilities, which can accurately locate the maximum power in complex environments.”
The original RIME was introduced in 2023 and has been applied in different fields. It uses the analogy of rime frost to balance exploration and exploitation capabilities. That is, by differentiating between soft and hard rime: while the first forms slowly and randomly and therefore is analogous to the exploration capabilities, the second forms quickly and directionally and is therefore analogous to the narrowing down of solutions based on promising regions.
“Our study elaborates on the improvements to the RIME optimization algorithm in three aspects,” explained the scientists. “First, the initial population is generated by using a logical mapping approach, which ensures that individuals are uniformly distributed in the solution domain, thereby effectively enhancing the diversity of the population. Second, by designing piecewise mapping rules, the algorithm’s dependence on parameters is reduced, thereby improving its robustness. Finally, the concept of inertia weight is introduced, where the weight is dynamically adjusted in accordance with the iteration count, to enhance the convergence velocity and stability of the algorithm.”
To test the novel IRIME algorithm, the team simulated five PV panels linked in a sequence, against PSO-MPPT and RIME-MPPT. The testing was done in the simulation software MATLAB. In the first case, of uniform illumination, the temperature was set to 25 C, and all panels received an irradiance of 1,000 W/m². In the shading scenario, the temperature was set to 25 C, and the irradiance per panel was 800 W/m², 800 W/m², 600 W/m², 600 W/m², and 400 W/m².
In a further scenario of sudden changes in illumination, the temperature was also constant at 25 C, but while in the first 0.6 s the irradiance measured 1,000 W/m2, 1,000 W/m2, 800 W/m2, 800 W/m2 and 600 W/m2; in the following stage, it changed to 800 W/m2, 800 W/m2, 600 W/m2, 600 W/m2 and 500 W/m2, respectively. In the final scenario of sudden changes, both in illumination and temperature, the temperature in the first 0.6 s was 35 C, and 25 C in the second stage. The initial irradiance was 1,000 W/m2, 1,000 W/m2, 800 W/m2, 800 W/m2 and 600 W/m2, and was then changed to 800 W/m2, 800 W/m2, 600 W/m2, 600 W/m2 and 400 W/m2.
“Compared to PSO-MPPT and RIME-MPPT, the proposed method reduced the average tracking time by 0.085 seconds and 0.425 seconds, respectively. Additionally, in terms of maximum output power, the proposed method achieved an average improvement of 0.97% and 3.48% over the aforementioned methods, respectively,” the results showed. “Particularly in PV system simulations under varying irradiance and temperature conditions, the proposed method consistently achieves the best results, verifying its efficient, stable, and fast-converging characteristics in MPPT strategies for PV systems.”
The new algorithm was presented in “An improved RIME optimization algorithm based maximum power point tracking method for photovoltaic system under partially shading condition,” published in Scientific Reports.
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