A system frequency detector includes 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 a frequency calculator including an angular frequency calculator calculating an angular frequency of the power system based on the two-phase voltage signal, and an arithmetic unit calculating a system frequency of the power system from the angular frequency, the frequency calculator further including a low-pass filter provided in series with the arithmetic unit.

A system frequency detector includes 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 a frequency calculator including an angular frequency calculator calculating an angular frequency of the power system based on the two-phase voltage signal, and an arithmetic unit calculating a system frequency of the power system from the angular frequency, the frequency calculator further including a low-pass filter provided in series with the arithmetic unit.

A frequency measurement device includes a sampling unit that outputs a voltage sampling value in accordance with a voltage to be sampled and a sampling frequency; an single-cycle DFT angle shift computation unit that computes and outputs a first angle shift in accordance with the voltage sampling value; an multi-cycle DFT angle shift computation unit that computes and outputs a second angle shift in accordance with the voltage sampling value; a selection unit that selects and outputs one of the first and second angle shifts as a selected angle offset; a sampling frequency computation and outputting unit that computes a sampling frequency in accordance with the selected angle offset and outputs the same to the sampling module unit as a new sampling frequency; and a frequency measurement value computation and outputting unit that computes and outputs a frequency measurement value in accordance with the selected angle offset.

A frequency measurement device includes a sampling unit that outputs a voltage sampling value in accordance with a voltage to be sampled and a sampling frequency; an single-cycle DFT angle shift computation unit that computes and outputs a first angle shift in accordance with the voltage sampling value; an multi-cycle DFT angle shift computation unit that computes and outputs a second angle shift in accordance with the voltage sampling value; a selection unit that selects and outputs one of the first and second angle shifts as a selected angle offset; a sampling frequency computation and outputting unit that computes a sampling frequency in accordance with the selected angle offset and outputs the same to the sampling module unit as a new sampling frequency; and a frequency measurement value computation and outputting unit that computes and outputs a frequency measurement value in accordance with the selected angle offset.

A system includes an orthogonal coordinate signal generator that generates an orthogonal two-phase voltage signal from a three-phase voltage signal of three-phase alternating current power of a power system; and a frequency calculator including an angular frequency calculator calculating an angular frequency of the power system based on the two-phase voltage signal, and an arithmetic unit calculating a system frequency of the power system from the angular frequency. A prediction calculator calculates a predicted value of the angular frequency after a time has elapsed based on the angular frequency and a differential of the angular frequency. In a state in which the phase jump of the power system is not detected, the frequency calculator calculates the system frequency based on the angular frequency. When the phase jump of the power system is detected, the frequency calculator calculates the system frequency based on predicted value for a constant amount of time.

A system includes an orthogonal coordinate signal generator that generates an orthogonal two-phase voltage signal from a three-phase voltage signal of three-phase alternating current power of a power system; and a frequency calculator including an angular frequency calculator calculating an angular frequency of the power system based on the two-phase voltage signal, and an arithmetic unit calculating a system frequency of the power system from the angular frequency. A prediction calculator calculates a predicted value of the angular frequency after a time has elapsed based on the angular frequency and a differential of the angular frequency. In a state in which the phase jump of the power system is not detected, the frequency calculator calculates the system frequency based on the angular frequency. When the phase jump of the power system is detected, the frequency calculator calculates the system frequency based on predicted value for a constant amount of time.

A method for estimating a property of a signal (1) sensed in an electrical system, comprises the steps of sensing the signal (1) and estimating a fundamental period of a fundamental of the signal (1) by comparing the sensed signal (1) with at least one threshold (2) to detect threshold crossings and estimating the fundamental period from the threshold crossings. The signal property is then estimated from the fundamental period and/or from the sensed signal (1) during an interval of a length of the fundamental period.

An electronic device according to the invention comprises a micro controller and/or an analogue circuitry which performs the method for estimating a property of a signal. Preferably, the micro controller and/or analogue circuitry controls other parts of the electronic device depending on the results obtained by the method for estimating a property of a signal.

A method for estimating a property of a signal (1) sensed in an electrical system, comprises the steps of sensing the signal (1) and estimating a fundamental period of a fundamental of the signal (1) by comparing the sensed signal (1) with at least one threshold (2) to detect threshold crossings and estimating the fundamental period from the threshold crossings. The signal property is then estimated from the fundamental period and/or from the sensed signal (1) during an interval of a length of the fundamental period.

An electronic device according to the invention comprises a micro controller and/or an analogue circuitry which performs the method for estimating a property of a signal. Preferably, the micro controller and/or analogue circuitry controls other parts of the electronic device depending on the results obtained by the method for estimating a property of a signal.

The invention relates to a method for detecting high-frequency signals (22), comprising method steps as follows: dividing a high-frequency signal (22) into a raw signal (3) and a reference signal (4), attenuating the raw signal (3) into an attenuated signal (9), wherein the attenuating happens as a function of frequency of the raw signal (3) in accordance with an attenuation characteristic, rectifying the attenuated signal (9), so that a first direct voltage (15) is generated, rectifying the reference signal (4), so that a second direct voltage (16) is generated, ascertaining an attenuation from the ratio of the first and second direct voltages (15, 16), wherein the ratio corresponds to an attenuation factor for the attenuation of the raw signal (3), determining the frequency of the high-frequency signal (22) from the attenuation factor and an attenuation characteristic (17).

The invention relates to a method for detecting high-frequency signals (22), comprising method steps as follows: dividing a high-frequency signal (22) into a raw signal (3) and a reference signal (4), attenuating the raw signal (3) into an attenuated signal (9), wherein the attenuating happens as a function of frequency of the raw signal (3) in accordance with an attenuation characteristic, rectifying the attenuated signal (9), so that a first direct voltage (15) is generated, rectifying the reference signal (4), so that a second direct voltage (16) is generated, ascertaining an attenuation from the ratio of the first and second direct voltages (15, 16), wherein the ratio corresponds to an attenuation factor for the attenuation of the raw signal (3), determining the frequency of the high-frequency signal (22) from the attenuation factor and an attenuation characteristic (17).