Synchronization Mechanism Between Power-Synchronized VS and PLL-Controlled CS and the Resulting Oscillations

Synchronization is the key of AC power system operation, but its mechanism becomes unclear with the large-scale integration of voltage-source converters (VSCs). As an important feature distinguishing VSCs from synchronous generators (SGs), the current-source characteristics of VSCs have hardly been focused from the perspective of synchronization. In this letter, a synchronization mechanism between power-synchronized voltage-source (VS) and PLL-controlled current-source (CS) is clarified. Based on this mechanism, negative damping oscillations of SGs caused by VSCs are disclosed.