| 摘要 |
A circuit for detecting the phase angle of a three-phase alternating current includes a plurality of low-pass filters installed at each input port for removing noise and high-frequency signals mixed in an alternating current input signal, a plurality of multipliers each for multiplying the signal output from each of the low-pass filter by a feedback signal, a subtracter for receiving the signals output from the plurality of multipliers and calculating an error between two signals, a loop filter for receiving the signal output from the subtracter and filtering the same, an integrator for receiving the signal output from the loop filter, time-integrating the same, and outputting an estimated digital phase angle signal, and a phase delay compensator installed between the subtracter and the loop filter, for compensating for phase delay of the input signal caused by the low-pass filters. Although the phase of the input signal is delayed by the low-pass filters for removing noise and high frequency signals installed at each input port, the delayed phase is automatically compensated for by the phase delay compensator. Thus, an estimating system can accurately estimate the phase angle.
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