Abstract: A modulation method is proposed for a single-stage high frequency isolated inverter that can realize bidirectional power flow in grid-connected photovoltaic systems. The proposed modulation method and the voltage clamp technique are used to eliminate the secondary-side voltage spikes and oscillations of the transformer of the traditional high frequency isolated photovoltaic grid-connected inverter. The inverter is a two-stage power converter. Its operating process and principle are analyzed in detail, the equivalent circuit model is established, and the mathematical model of the inverter is derived. In order to overcome the shortcomings of traditional multiresonant controller, a phase compensation multi-resonant controller is developed for the single stage high-frequency isolated photovoltaic grid-connected inverter. Maximum power point tracking（MPPT） and accurate control of grid-connected current are achieved in a single stage structure. Finally, the modulation method and control strategy of the single-stage high frequency isolation photovoltaic gridconnected inverter are verified through experiments.