This paper describes a method for maximum power point tracking (MPPT) control while searching for optimal parameters corresponding to weather conditions at that time. The conventional method has problems in that it is impossible to quickly acquire the generation power at the maximum power (MP) point in low solar radiation (irradiation) regions. It is found theoretically and experimentally that the maximum output power and the optimal current, which give this maximum, have a linear relation at a constant temperature. Furthermore, it is also shown that linearity exists between the short-circuit current and the optimal current. MPPT control rules are created based on the findings from solar arrays that can respond at high speeds to variations in irradiation. The proposed MPPT control method sets the output current track on the line that gives the relation between the MP and the optimal current so as to acquire the MP that can be generated at that time by dividing the power and current characteristics into two fields. The method is based on the generated power being a binary function of the output current. Considering the experimental fact that linearity is maintained only at low irradiation below half the maximum irradiation, the proportionality coefficient (voltage coefficient) is compensated for only in regions with more than half the rated optimal current, which correspond to the maximum irradiation. At high irradiation, the voltage coefficient needed to perform the proposed MPPT control is acquired through the hill-climbing method. The effectiveness of the proposed method is verified through experiments under various weather conditions. Index Terms-Current control, irradiation, maximum power point tracking (MPPT), photovoltaic (PV), PV power generation.

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Abstract-A control method is described to charge seriesconnected ultraelectric double-layer capacitors (ultra-EDLCs) suitable for photovoltaic generation systems in combination with a maximum power point tracking (MPPT) control method. The EDLC charge control method allows the maximum power acquired by the MPPT control to be quickly charged into seriesconnected ultra-EDLCs no matter how the weather conditions may change. In the MPPT control, the output current of the solar arrays is controlled so that the output power converges on the maximum power in the prediction line previously determined based on the linearity between the maximum output power and the optimization current. The proportionality coefficient of the prediction line is automatically corrected using the hill-climbing method when the panel temperature of the solar arrays is changed. The EDLC charge control is performed with the three charge modes, i.e., the constant current charge mode, constant power charge mode, and the constant voltage charge mode while supervising the maximum voltage and allowable temperature of each series-connected EDLC. Effectiveness of the methods is verified by simulations and experiments.Index Terms-Maximum power point tracking (MPPT), photovoltaic (PV), power supply, ultraelectric double-layer capacitors (ultra-EDLCs).

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