Abstract: A frequency-coefficient calculating unit calculates, as a frequency coefficient (fc), a value ((v21+v23)/(2v22)) obtained by normalizing, with a differential voltage instantaneous value (v22) at intermediate time, an average ((v21+v23)/2) of a sum (v21+v23) of differential voltage instantaneous values at time other than the intermediate time among differential voltage instantaneous value data (v21, v22, and v23) at three points representing an inter-distal end distance between voltage instantaneous value data at adjacent two points in voltage instantaneous value data at continuous at least four points extracted, out of voltage instantaneous value data obtained by sampling a measurement target alternating-current voltage at a predetermined data collection sampling frequency, at a gauge sampling frequency lower than the data collection sampling frequency and equal to or higher than a frequency of the alternating-current voltage.

Abstract: An alternating-current electrical quantity measuring apparatus calculates, as a frequency coefficient, a value obtained by normalizing, with a differential voltage instantaneous value at intermediate time, a mean value of a sum of differential voltage instantaneous values at times other than the intermediate time among differential voltage instantaneous value data at three points each representing an inter-point distance between voltage instantaneous value data at adjacent two points in voltage instantaneous value data at continuous at least four points obtained by sampling an alternating voltage set as a measurement target at a sampling frequency twice or more as high as a frequency of the alternating voltage.

Abstract: According to a present alternating-current electric quantity measuring apparatus, a voltage amplitude calculated by a square integral operation of at least three continuous voltage instantaneous values sampled at a sampling frequency twice or higher than a frequency of an alternating-current voltage to be measured is normalized. A voltage chord length calculated by the square integral operation of three voltage chord length instantaneous values representing an end-to-end distance between two adjacent voltage instantaneous values in at least four continuous voltage instantaneous values including the three voltage instantaneous values, which are sampled at the sampling frequency and used in calculating the normalized voltage amplitude, is normalized. A rotation phase angle in one period time of sampling is calculated using the normalized voltage amplitude and the normalized voltage chord length. A frequency of the alternating-current voltage is calculated using the calculated rotation phase angle.

Abstract: Voltage instantaneous value time-series estimation data and a present-time voltage estimation value are calculated by using an actually-measured frequency and voltage instantaneous value time-series data according to a least square method. A present-time voltage effective value is determined by using the calculated voltage instantaneous value time-series estimation data, and a present-time synchrophasor, a voltage distortion degree and an inter-bus-line synchrophasor phase angle difference are determined by using the present-time voltage effective value and the present-time voltage estimation value.

Abstract: The invention relates to a frequency measurement apparatus which is arranged in such a way as to obtain an amplitude, chord length and rotation phase angle of a voltage rotation vector by means of an integration method, and furthermore, obtain a change rate of the rotation phase angle, and a rotational acceleration change rate of the rotation vector, and measure a dynamic frequency by determining a frequency change rate for every step.

Abstract: In the present invention, a measured realtime accurate frequency is used to determine estimated instantaneous voltage/current time-series data for each phase component in accordance with the least-squares method. The estimated instantaneous voltage/current time-series data are used to determine effective voltage, effective current, instantaneous active electric power, instantaneous reactive electric power, effective active electric power, and effective reactive electric power of each phase component and symmetrical component. The measured AC electric quantities are applied to any type of electric power system control/protection apparatus.

Abstract: An active filter that can remove harmonic noises other than the fundamental wave in a system having many unspecified harmonics and can contribute to the stable operation of the system, and improvement in the quality of power is provided. Using the following power equation (1) for a single-phase circuit as a basic expression, an active power effective value P and a reactive power effective value Q are obtained by integration operation with an active power instantaneous value and a reactive power instantaneous value, an instantaneous voltage estimation value is calculated, the system side fundamental wave current is obtained based on these values, and then the system side fundamental wave current is subtracted from the load current to obtain compensation current as the output of the active filter.

Abstract: Voltage instantaneous value time-series estimation data and a present-time voltage estimation value are calculated by using an actually-measured frequency and voltage instantaneous value time-series data according to a least square method. A present-time voltage effective value is determined by using the calculated voltage instantaneous value time-series estimation data, and a present-time synchrophasor, a voltage distortion degree and an inter-bus-line synchrophasor phase angle difference are determined by using the present-time voltage effective value and the present-time voltage estimation value.

Abstract: In the present invention, a measured realtime accurate frequency is used to determine estimated instantaneous voltage/current time-series data for each phase component in accordance with the least-squares method. The estimated instantaneous voltage/current time-series data are used to determine effective voltage, effective current, instantaneous active electric power, instantaneous reactive electric power, effective active electric power, and effective reactive electric power of each phase component and symmetrical component. The measured AC electric quantities are applied to any type of electric power system control/protection apparatus.

Abstract: The invention relates to a frequency measurement apparatus which is arranged in such a way as to obtain an amplitude, chord length and rotation phase angle of a voltage rotation vector by means of an integration method, and furthermore, obtain a change rate of the rotation phase angle, and a rotational acceleration change rate of the rotation vector, and measure a dynamic frequency by determining a frequency change rate for every step.

Abstract: The rotation phase angle measuring device measures a voltage instantaneous value of an electric power system in a period of 1/(4 N) of one period of a reference wave and integrates voltage amplitude of a squared value of the voltage instantaneous value in arbitrary timing for measuring the voltage instantaneous value. The rotation phase angle measuring device calculates chord lengths of the voltage rotation vectors in the above two timings by the integral arithmetic calculation with respect to a difference between two measured adjacent voltage instantaneous values in one pitch period including the above timing. The rotation phase angle measuring device also has a rotation phase angle calculator for calculating a phase angle of the voltage rotation vector in one pitch period including the above timing on the basis of the voltage amplitude value and the chord length value calculated by the above calculations.

Abstract: An active filter that can remove harmonic noises other than the fundamental wave in a system having many unspecified harmonics and can contribute to the stable operation of the system, and improvement in the quality of power is provided. Using the following power equation (1) for a single-phase circuit as a basic expression, an active power effective value P and a reactive power effective value Q are obtained by integration operation with an active power instantaneous value and a reactive power instantaneous value, an instantaneous voltage estimation value is calculated, the system side fundamental wave current is obtained based on these values, and then the system side fundamental wave current is subtracted from the load current to obtain compensation current as the output of the active filter.

Abstract: The rotation phase angle measuring device measures a voltage instantaneous value of an electric power system in a period of 1 4N-th (N is a positive integer) of one period of a reference wave when the voltage instantaneous value of the electric power system is expressed by a voltage rotation vector on a complex plane. The rotation phase angle measuring device calculates a voltage amplitude value by an integral arithmetic calculation of a squared value of the voltage instantaneous value in arbitrary timing for measuring the voltage instantaneous value. The rotation phase angle measuring device calculates chord lengths of the voltage rotation vectors in the above two timings by the integral arithmetic calculation with respect to a difference between two measured adjacent voltage instantaneous values in one pitch period including the above timing.

Abstract: A synchronous vector measuring device can measure an absolute phase angle of a synchronous vector excellent in continuous numerical stability at high speed and with high accuracy in a noisy electric power system. A voltage measuring part measures the voltage of the electric power system at a period equal to 1/4N (N being a positive integer) of one period of a reference wave. A voltage root-mean-square value calculation part calculates, at each voltage measuring timing, a voltage root-mean-square value at a specific timing from the voltages measured at past 4N timings including the specific timing. An absolute phase angle calculation part makes, at each voltage measuring timing, an inverse cosine of a value obtained by dividing the voltage measured at the specific timing by the product of the voltage root-mean-square value and the square root of 2, as the absolute phase angle of the synchronous vector at the specific timing.

Abstract: A frequency measuring device can measure the frequency of a noisy power system at high speed. The system voltage is measured at timings obtained by equally dividing one reference-wave period. Voltage vectors are calculated which have tip ends, each voltage vector consisting of a real part of a first measured voltage and an imaginary part of another voltage measured at timing 90 degrees before the first measured voltage. The length of a chord connecting tip ends of adjacent voltage vectors is calculated. A voltage root-mean-square value is calculated from voltages measured between two timings spaced from each other by the one reference-wave period. Chord lengths obtained between two timings spaced from each other by the one reference-wave period are summed. Based on the total of the chord lengths and the voltage root-mean-square value, there is calculated a phase angle between two adjacent voltage vectors, from which the system frequency is calculated.

Abstract: A synchronous vector measuring device can measure an absolute phase angle of a synchronous vector excellent in continuous numerical stability at high speed and with high accuracy in a noisy electric power system. A voltage measuring part measures the voltage of the electric power system at a period equal to 1/4N (N being a positive integer) of one period of a reference wave. A voltage root-mean-square value calculation part calculates, at each voltage measuring timing, a voltage root-mean-square value at a specific timing from the voltages measured at past 4N timings including the specific timing. An absolute phase angle calculation part makes, at each voltage measuring timing, an inverse cosine of a value obtained by dividing the voltage measured at the specific timing by the product of the voltage root-mean-square value and the square root of 2, as the absolute phase angle of the synchronous vector at the specific timing.

Abstract: A frequency measuring device can measure the frequency of a noisy power system at high speed. The system voltage is measured at timings obtained by equally dividing one reference-wave period. Voltage vectors are calculated which have tip ends, each voltage vector consisting of a real part of a first measured voltage and an imaginary part of another voltage measured at timing 90 degrees before the first measured voltage. The length of a chord connecting tip ends of adjacent voltage vectors is calculated. A voltage root-mean-square value is calculated from voltages measured between two timings spaced from each other by the one reference-wave period. Chord lengths obtained between two timings spaced from each other by the one reference-wave period are summed. Based on the total of the chord lengths and the voltage root-mean-square value, there is calculated a phase angle between two adjacent voltage vectors, from which the system frequency is calculated.