Single phase inverters/rectifiers have double-frequency voltage ripple on the DC-link due to the unbalanced instantaneous power between the input and output. In extremely low frequency detection and communication system, the output frequency of the power amplifier is low and variable. The low output frequency limits the cutoff frequency of the filter and thus causes a delay. Meanwhile, variable output frequency limits the application of ripple frequency sensitive methods such as proportional-resonant control. This paper proposes a general power decoupling control method independent of the ripple frequency and supporting plug-in operation. Firstly, this paper analyzes the characteristics of DC-link voltage ripple and the power decoupling control method based on the DC-link capacitor current is proposed. Then, the effects of capacitor equivalent series resistor and DC source output capacitor on the control method are analyzed in detail and corrected. In addition, the stability of control system and parameters designed are described. Finally, a 3 kW experimental prototype are designed to verify the validity and correctness of the analytical control method.