An islanding detection method and reference current extremum calculation method for AC/DC hybrid power grid
An AC-DC hybrid, reference current technology, applied in AC network circuits, AC/pulse peak measurement, measurement of electricity and other directions, can solve the problems of the system returning to a steady state, the process of restoring the system to a steady state, the AC system fault fluctuation, and the frequency collapse. , to shorten the recovery time, reduce the fluctuation of the AC voltage amplitude, and achieve the effect of fast and accurate detection
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Embodiment 1
[0051] This embodiment is used to detect whether the method can avoid the misjudgment that the AC line is in an island state due to a fault in the AC system.
[0052] A three-phase short-circuit fault is set at the exit bus of the converter station at the receiving end. The fault occurs in 0.6s and disappears after 50ms. to combine Figure 4 , 5 , the output active power of the converter station continued to decrease during the short circuit, reaching the minimum value of -10.6MW at 0.653s, and the power difference was 109.4MW. After that, the active power starts to rise up to the set value. to combine Figure 6 , The maximum value during power recovery is 0.49kA, which has a margin of 69% compared with the setting value of 0.828kA.
Embodiment 2
[0054] This embodiment is used to detect whether the method can quickly detect whether the AC line is in an island state.
[0055] refer to figure 2 , the AC line 1 is cut off at 0.6s, and the AC line 2 is cut off at 0.7s to form an isolated island system at the receiving end. The island detection method proposed by the present invention is adopted for the system and a constant AC voltage control is adopted after switching.
[0056] refer to Figure 7 , the curve in the figure shows the change of the voltage effective value U at the outlet bus of the converter station at the receiving end. to combine Figure 8 , the curve in the figure shows the variation of frequency f of the island system at the receiving end when the system adopts the islanding detection method proposed by the present invention, combined with Figure 9 , when the AC line 1 was cut off at 0.6s, the frequency and voltage of the receiving end system did not fluctuate, the d-axis reference current of the re...
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