A modified hill-climbing method for a photovoltaic generation system (PV system), using an adaptive algorithm, is proposed for the maintenance of its output at maximum power levels. The switch duty ratio of the DC-DC converter of the PV system and its output power are selected as the input and output value, respectively, and its characteristics are described by the characteristic curves (the switch duty ratio vs. output power). The characteristics of the PV system are changed due to the changes of external environmental conditions such as atmosphere, loads and so on. The changes of its characteristic curves are detected as the changes of its gradients, which are estimated as parameters of linear functions by adaptive theory. The change of the switch duty ratio is determined based on the detected characteristic changes. That is, the non-linearity of the PV system and its changing characteristics due to the changes of its external environmental conditions are regarded as deviations of the parameters of the linear functions. It is applied in some experiments under various external environmental conditions and its effectiveness confirmed. Therefore, the proposed method is considered to be generally applicable method as a maximum power controller, for which detailed information of the characteristics of the PV system, including its external environmental conditions, is not required.
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