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 6:
7. The system frequency detector according to claim 3, wherein
the frequency calculation circuitry further includes:
a sample-and-hold circuit provided in parallel with the rate limiter, the sample-and-hold circuit including
a sample mode of causing an output signal to track an input signal, and
a hold mode of holding the output signal to be substantially constant at a value of a prescribed timing; and
a switching circuit selectively switching between a first state in which the rate limiter is used and a second state in which the sample-and-hold circuit is used,
the orthogonal coordinate signal generator generates a voltage signal of an active component of the three-phase alternating current power of the power system by converting the two-phase voltage signal into a voltage signal of a rotating coordinate system, and
the switching circuit selects the first state and causes the sample-and-hold circuit to operate in the sample mode when an absolute value of a differential of the voltage signal of the active component is less than a prescribed value, and selects the second state and switches the sample-and-hold circuit from the sample mode to the hold mode when the absolute value of the differential of the voltage signal of the active component is equal to or greater than the prescribed value.