Transient stability analysis method and system for photovoltaic grid-connected inverter under weak grid fault

The invention discloses a photovoltaic grid-connected inverter transient stability analysis method and system under a weak grid fault, and belongs to the field of new energy grid-connected power generation. Comprising the following steps: decomposing a transient full-order model of the photovoltaic grid-connected inverter into a slow system model taking a grid-connected current d-axis component as a variable and a fast system model taking grid-connected current d-axis component disturbance, direct-current voltage disturbance and phase-locked loop deviation angle disturbance as variables; obtaining a derivative by analyzing the change rate of the energy function, and constructing a slow system transient stability first criterion by using a positive value energy function and a negative value derivative; constructing a fast system transient stability second criterion based on the principle that the real parts of all feature values are negative; if two criteria are met at the same time, the transient state is sta