Abstract
The fractional open-circuit voltage (FOCV) method is commonly adopted to track maximal power point of photovoltaic systems due to easy implementation and cost-effectiveness. However, the FOCV method is confronted with unstable output power and limited tracking accuracy. This paper proposes a novel on-site traversal FOCV method with uninterrupted output power and increased tracking accuracy through simulation and experimental verifications. Each solar cell is connected with a bypass diode and switching circuitry, so that specific solar cell can be traced and measured consecutively for determining its maximal power point (MPP). MATLAB/Simulink simulation results show that, in the time-varying irradiance case, the proposed method achieves a low ripple factor of 0.13% in 11–13 h and 0.88% in 9–15 h, under the typical 24 h irradiance curve. In the spatial-varying irradiance case, the accuracy of the proposed method reaches 99.85%. Compared with other FOCV methods, like pilot cell and semi pilot cell methods, the proposed method is of higher accuracy with a limited ripple effect. Experimental results show that this method can effectively trace different output performance of specific solar cell while generating stable output voltage with a low ripple factor of 1.55%, proving its compatibility with distributed sensing and applicability in smart photovoltaic systems.
Highlights
The ever-declining petroleum resources have forced worldwide nations to optimize the energy mix for sustainable development
The problem still exists in that electrical characteristics of the pilot cell may not be representative of all solar cells in the system, and the calculated maximal power point (MPP) might not be accurate for the entire photovoltaic panel
Despite the efficiency loss arising from the fact that the output voltage of one unit is not connected to the load for purpose of measurement, it is expected that the dual advantages of enhanced MPP accuracy and reduced ripple factor outweigh such efficiency loss
Summary
The ever-declining petroleum resources have forced worldwide nations to optimize the energy mix for sustainable development. In the global search for clean, renewable and safe energy sources, solar power is most concerned due to its ubiquitous existence, inexhaustible amount, and high-level safety. The past decade has witnessed tremendous growth in the global photovoltaic market, and this trend is still continuing. At the end of 2019, the world’s total photovoltaic capacity has reached 580. In China, it is expected that the cumulative installed photovoltaic capacity will be rocketed from 130 GW by 2017 [2] to approximately 2.7 TW by 2050 [3]. Despite the fast growth rate, photovoltaic systems are still confronted with the challenge of enhancing efficiency. Solar cells typically exhibit nonlinear power–voltage curves [4], and are very
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