Patent ID: 11953530
Assignee: TOSHIBA MITSUBISHI—ELECTRIC INDUSTRIAL SYSTEMS CORPORATION
Field: Electrical machinery, apparatus, energy (Electrical engineering)
Classification: CPC G  H  Y | IPC G  H

Claim 0:
1. A system frequency detector, comprising:
an orthogonal coordinate signal generator generating an orthogonal two-phase voltage signal from a three-phase voltage signal of three-phase alternating current power of a power system by converting the three-phase voltage signal into a two-phase voltage signal orthogonal to the three-phase voltage signal, converting the two-phase voltage signal into a voltage signal of a rotating coordinate system, calculating a moving average of the voltage signal of the rotating coordinate system, and performing an inverse transformation of the voltage signal of the rotating coordinate system after calculating the moving average; and
frequency calculation circuitry including
an angular frequency calculator calculating an angular frequency of the power system based on the two-phase voltage signal after calculating the moving average generated by the orthogonal coordinate signal generator, and
an arithmetic calculator calculating a system frequency of the power system from the angular frequency by multiplying the angular frequency by ½π,
the frequency calculation circuitry further including a low-pass filter provided in series with the arithmetic calculator, the low-pass filter suppressing a high frequency component of the system frequency.