Impedance Modeling and Stability Analysis for the PLL-less and Voltage Sensor-less Grid-tied Converters

The newly developed control methodology, which omits the phase-locked loop (PLL) and voltage sensor, has garnered considerable attention for its rapid dynamic response and reduced hardware expenses. Nonetheless, its stability concerns have not yet been thoroughly scrutinized. In this paper, the impedance modeling of the PLL-less and voltage sensorless control strategy has been established. The impedance model has been contrasted with the traditional PLL-based control scheme. Our findings demonstrate that the PLL-less and voltage sensorless control approach lacks the negative resistance behavior that is frequently observed in the traditional scheme, which results in unstable operations. Moreover, the role of virtual resistance has been examined. To substantiate the aforementioned findings, simulation results are presented.