Importance

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Abstract

The present invention relates to a system for monitoring the electric network voltage waveform, comprising: switching means (11) connected to the voltage lines (A, B, C) of a three-phase system, comprising two thyristors (T1, T2) connected to two of the voltage lines (A, B, C) and at least two capacitors (C1, C2) connected to said thyristors (T1, T2), said means (11) being configured to open and close said thyristors (T1, T2) in response to a trigger signal; means for measuring (12) the voltages in said voltage lines and at the input of said capacitors; a thyristor trigger circuit (14) for providing a trigger signal to either thyristor (DT1, DT2) when the voltage in the terminals of said thyristor (T1, T2) crosses zero; control means (13, 23) for giving said trigger order (OD) or not. The control means comprise: a PLL (231, 331) configured to obtain an image signal from the voltage signals of said voltage lines (A, B, C), from the phase angle (φ) of the three-phase system and from the temporal variation thereof; an adaptive notch filter (232, 432) for providing filtered voltage signals between the voltage lines (V_{AC_f}, V_{BC_f}); means for filtering the voltages at the input of the capacitors (V_{C1_f}, V_{C2_f}); a zero crossing detector (235, 535) configured to provide said trigger order (OD).

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First Claim