A novel auto-scaling variable step-size maximum-power-point-tracking (MPPT) method is proposed in this paper. The novel method eliminates the problems in the conventional variable step-size method. The proposed tracking method uses the simple judgment criterion and auto-scaling variable step size to enable the solar photovoltaic system to achieve fast dynamic response and stable steady-state output power, even under enormous weather changes. The conventional variable step-size method must use a constant value multiplier to guarantee the convergence of the tracking process. However, this constant value makes the dynamic response of the solar system slow in the enormous irradiation change condition because the system cannot instantaneously respond to the changes in the environmental conditions. The proposed method can automatically adjust the step size of the tracking algorithm to achieve the fast dynamic response that can adapt to weather changes and thereby achieve stable steady-state output power. A digital signal processor (DSP) is used to realize the proposed tracking algorithm. The signals of the solar voltage and current are fed to the ADC module of the DSP, and the PWM signal is subsequently output to drive the switch of the converter to execute the MPPT process. From the simulation and experimental results, the proposed method was validated by a real application. The proposed method enables a solar photovoltaic system to achieve good dynamic response and stable output power. (C) 2014 Elsevier Ltd. All rights reserved.