Frequency behavior and its stability of grid-interface converter in distributed generation systems

Phase-locked loops for grid-tied inverters: comparison and testing

“…[10,11] have demonstrated the correlations between different load types (inductive or capacitive) and the different frequency behaviours of inverters during islanded conditions. [10,11] have also proposed an anti-islanding method utilizing the changes in the output frequencies of PLLs. The proposed relations between load type and frequency behaviours in [10,11] can be further extended to the view of power balance at the point of common coupling (PCC).…”

“…[10,11] have also proposed an anti-islanding method utilizing the changes in the output frequencies of PLLs. The proposed relations between load type and frequency behaviours in [10,11] can be further extended to the view of power balance at the point of common coupling (PCC). The model of the test circuit is shown in Figure 4.…”

“…PLLs must be able to cope in such situations, even if they are only used to detect islanding and respond accordingly. In [10,11] a positive frequency feedback model was proposed to predict the frequency behaviours grid-connected voltage source inverters (VSI). [10,11] have demonstrated the correlations between different load types (inductive or capacitive) and the different frequency behaviours of inverters during islanded conditions.…”

“…In [10,11] a positive frequency feedback model was proposed to predict the frequency behaviours grid-connected voltage source inverters (VSI). [10,11] have demonstrated the correlations between different load types (inductive or capacitive) and the different frequency behaviours of inverters during islanded conditions. [10,11] have also proposed an anti-islanding method utilizing the changes in the output frequencies of PLLs.…”

“…An average model of the VSI is used for ease of identification of the oscillations in the outputs of the PLLs. In order to show how the theory proposed in [10,11] can be extended to the power balance point of view, the VSI is set in constant power mode. The 11 kV grid contains 1% of 2 nd harmonic, 2.5% of 3 rd harmonic, 3% of 5 th harmonic, 2.5% of 7 th harmonic, 1.5% of 13 th harmonic, 0.25% of 15 th harmonic and 0.25% of 24 th harmonic.…”