Abstract: In order to further solve the problems of traditional dual closed-loop algorithms of single-phase inverters such as poor load adaptability and large transient voltage fluctuations, a pulse-by-pulse control strategy based on fuzzy PID control in variational domain is proposed in this paper. The proposed algorithm compresses the traditional amplitude feedback to a sufficiently small interval, compared with the traditional method of giving effective value of the whole cycle, the given value is the effective value corresponding to each small interval, that is, the interval effective value, and the feedback value is the discrete RMS of the sampling point. The variable universe fuzzy PID control is utilized to improve the robustness and control precision. Theoretical research shows that it can take into account the advantages of amplitude and instantaneous value feedback and improve the performance of the inverter device, as well as reduce the difficulty of loop parameter design. In order to verify the correctness of the algorithm, a 3 kW test prototype is set up, and the experimental results show the effectiveness of the proposed control method.