Abstract: Different from DC-DC converters, DC-AC converters operate at both switching frequency and grid frequency, which makes its stability analysis more challenging. In this paper, the stability of digitally controlled single-phase grid-connected inverters is studied by Filippov method, and the multi-time scale dynamics and digitization effects are fully considered. The transition matrix and state transition matrix of the digitally controlled single-phase grid-connected inverter are derived, and the closed ex-pression of the single-valued matrix is obtained. Based on the derived single-valued matrix, the influ-ence of different control parameters on the stability of the system is evaluated. Finally, the theoretical analysis is verified by experiments.