Phase sequence self-adaptive grid-connected control method and system of chain type SVG (Static Var Generator) device

The invention discloses a phase sequence adaptive grid-connected control method and system for a chain type SVG device, and the method comprises the steps: 1), obtaining a three-phase line voltage inputted by the SVG device, and obtaining a three-phase phase voltage synchronization signal; 2) taking the three-phase phase voltage as the input of a software phase-locked loop, performing voltage phase sequence judgment by using d-axis and q-axis components of the voltage output by the software phase-locked loop, if the voltage phase sequence is a negative sequence, exchanging any two-phase voltage, and adjusting the three-phase voltage to be a positive sequence; 3) acquiring data of the three-phase current and the three-phase synchronous voltage of the SVG during high-voltage switching on of the SVG; 4) obtaining a corresponding line sequence relation between the three-phase synchronous voltage and the three-phase input voltage according to the data of the SVG three-phase current and the three-phase synchronous