Patent ID: 11971437
Assignee: HYOSUNG HEAVY INDUSTRIES CORPORATION
Field: Measurement (Instruments)
Classification: CPC G  H | IPC G  H

Claim 0:
1. A grid voltage phase detector, comprising:
a d-q transformer for receiving a three-phase signal and producing a signal on d axis and a signal on q axis;
a phase signal producer for producing a signal for phase synchronization of grid voltage from the signal on d axis and the signal on q axis; and
a proportional resonant (PR) filter, with a first filter having no change in magnitude and phase at a rated frequency, a second filter introducing 90° phase lead at a rated frequency, a third filter introducing 90° phase lag, and a fourth filter having no change in magnitude and phase at a rated frequency, for removing unbalanced components and harmonic components from the signal on d axis and the signal on q axis produced by the d-q transformer and providing signals to the phase signal producer,
wherein:
the first filter and the fourth filter individually have a steep peak in a coordinate with frequency and magnitude in an exponential scale and have filtering characteristics of having 0 degrees phase at the rated frequency, −90 degrees phase at upper frequencies belonging to filtering cutoff frequencies, and 90 degrees phase at low frequencies belonging thereto in a coordinate with frequency and phase in an exponential scale;
the second filter has a steep peak in a coordinate with frequency and magnitude in an exponential scale and has filtering characteristics of having 90 degrees phase at the rated frequency, 0 degrees phase at upper frequencies belonging to filtering cutoff frequencies, and 180 degrees phase at low frequencies belonging thereto in a coordinate with frequency and phase in an exponential scale; and
the third filter has a steep peak in a coordinate with frequency and magnitude in an exponential scale and has filtering characteristics of having −90 degrees phase at the rated frequency, 0 degrees phase at upper frequencies belonging to filtering cutoff frequencies, and −180 degrees phase at low frequencies belonging thereto in a coordinate with frequency and phase in an exponential scale.