To solve the problem of poor power quality and grid voltage fluctuation caused by the photovoltaic and wind power variation， a method is proposed for smoothing output power vibration in different time frame by utilizing hybrid energy storage technologies. In the process of smoothing output power， variable time constant control is used. It can realize swift control of charging/discharging stored power， optimize the operation of energy storage system， and minimize the storage capacity by adjusting the time constant of low pass filter in real time. Maximum output power limitation is also proposed to ensure the storage system operate in a reasonable range. Simulation results demonstrate the effectiveness of the control method.