High system cost and reduced output power due to the changing weather conditions such as the irradiance or temperature are two major concerns for a practical photovoltaic (PV) system design. This paper presents a current sensorless (CS) maximum power point tracking (MPPT) algorithm that uses only one single-input-voltage sensor (SIVS) and totally eliminates the expensive current sensors, which can significantly reduce the system cost and retain the advantages of the widely used MPPT algorithms such as incremental conductance (INC). To further eliminate the drift effect, which is a severe phenomenon due to the incorrect decision in duty cycle for fast irradiation change, drift-free technique is adopted in the presented algorithm by incorporating the information of change in duty cycle (Delta D) and change in input voltage (Delta V). A mathematical expression is given to define the drift-free criterion and the threshold is determined by the Lambert W function with respect to the dynamic EN50530 test standard. Experimental results under different scenarios are presented to validate the advantages of the presented method in terms of the tracking efficiency and drift-free characteristic.