Analysis and suppression of interaction between STATCOM and voltage-source inverter in islanded micro-grid

The interaction between STATCOM and voltage-source inverter (VSI) may cause instability in an islanded micro-grid. Impedance models of storage battery power convert system (PCS) and cascaded multilevel static synchronous compensator (STATCOM) are established based on which the interaction mechanism between PCS and STATCOM is studied. Using Nyquist stability criterion and admittance ratio analysis, it is shown that stabilization of single converter is not sufficient for the whole system. A lead-lag compensator is applied to reshape the STATCOM impedance. Analysis shows that the compensator is effective to suppress system instability. Simulation and experiment are presented to verify the validity of analysis results.