JP2015148478A - Power measurement method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power measurement method capable of sampling with high accuracy without increasing a data volume.SOLUTION: A plurality of sampling periods derived by equally dividing the cycle of an AC power supply 20 by N (N is a natural number) and a plurality of sampling timings with which sampling is performed in a sampling period are set. A first cycle T1 in which power is calculated from the result of sampling in an odd-numbered sampling period among the sampling periods and a second cycle T2 in which power is calculated from the result of sampling in an even-numbered sampling period are alternately repeated, and measurement of power is made by integrating power calculated in the first cycle T1 and second cycle T2.

Description

  The present invention relates to a power measurement method, and more particularly to a power measurement method capable of increasing measurement accuracy.

  Conventionally, in order to measure power in a sampling wattmeter, an analog-digital (hereinafter referred to as AD) converter that converts an analog signal into a digital signal is used to sample an input voltage waveform and an input current waveform. Technologies that require power from the results are widely used.

  In the power measuring device 900 described in Patent Document 1 (conventional example), as shown in FIG. 3, a voltage detection unit 911, a current detection unit 912, a signal switching unit 913, a signal amplifier 914, an AD converter 915, and a power calculation unit. 916, a display 917, a clock generator 918, and a switching control unit 919.

  The power calculation unit 916 and the switching control unit 919 are configured by general-purpose microcomputers, and the variable setting unit 919a is connected to the sampling period m, the number of divisions n, the time width W, and the time width via the input interface in the microcomputer. Y is set.

  The time width (predetermined period) W is set to a natural number multiple of n times or more of the power cycle, and the period during which the power value is integrated (calculated) is a period obtained by adding at least n time widths W.

  FIG. 4 is a diagram for explaining the AD sampling timing with respect to the signal waveform of the power measuring apparatus 900. When the sampling period m = ¼ of the power supply period and the number of divisions n = 3, AD conversion is performed at the first first timing among the three AD sampling timings in the period A shown in FIG. . In the period B, AD conversion is performed at the second timing among the three AD sampling timings. Further, in the period C, AD conversion is performed at the third (nth) third timing among the three AD sampling timings.

  The order of the AD sampling timing is set so that the order of the first timing, the second timing, and the third timing is repeated by the order setting unit 919b.

  As described above, by shifting the n-divided AD sampling timing one by one, power is detected in the same manner as when sampling is performed at an AD sampling frequency of n times.

JP 2012-225767 A

  However, in the above-described conventional example, the period during which the power value is integrated is required at least n times of the time width W, and the time width W is also set to n times or more of the power cycle, so that a long time is required for measurement. The amount of data increases. For this reason, the memory capacity for storing the sampled data during the period in which the power values are integrated increases. Further, since the sampling period m is divided by the division number n during the period in which the power value is integrated and integration is performed for the time width W of n times at different sampling timings, the power period is set in the period in which the power value is integrated. There is a problem that an error occurs when fluctuation occurs.

  The present invention solves the above-described problems, and an object thereof is to provide a power measurement method capable of performing sampling with high accuracy without increasing the amount of data.

  In order to solve this problem, the power measurement method of the present invention is a power measurement method in which instantaneous values such as voltage and current supplied from an AC power source to a load are sampled and power is measured from the sampled results. A plurality of sampling periods obtained by dividing the period of the AC power supply into N equal parts (N is a natural number) and a plurality of sampling timings for performing sampling in the sampling period. The first cycle for calculating the power from the result of sampling in the period and the second cycle for calculating the power from the result of sampling in the even-numbered sampling period are alternately repeated, and the first cycle and the The power is measured by integrating the power calculated in the second period.

  According to this, in the sampling period, the first period in which power is calculated from the result of sampling in the odd-numbered sampling period, and the second period in which power is calculated from the result of sampling in the even-numbered time zone. The cycle is repeated alternately. For this reason, the period for accumulating data obtained by sampling is completed in two power supply cycles, and the amount of data to be accumulated does not increase. Therefore, a memory having a small capacity for storing data obtained by sampling is used. It becomes possible. In addition, since the period for accumulating data obtained by sampling is short, the period that is affected by fluctuations in the power supply cycle is shortened, and the reduction in accuracy can be suppressed. Therefore, it is possible to provide a power measurement method capable of performing sampling with high accuracy without increasing the data amount.

  According to the present invention, it is possible to provide a power measurement method capable of performing sampling with high accuracy without increasing the amount of data.

It is a block which shows the structure of the electric power measurement apparatus with which the measuring method of the electric power which concerns on embodiment of this invention is applied. It is a figure explaining the measuring method of the electric power which concerns on embodiment of this invention. It is a figure which shows the power measuring device of a prior art. It is a figure which shows AD sampling timing with respect to the signal waveform of the power measuring device of a prior art.

[First Embodiment]
The power measurement method in the first embodiment will be described below.

  FIG. 1 is a block diagram illustrating a configuration example of a power measurement apparatus 10 to which a power measurement method according to an embodiment of the present invention is applied.

  As shown in FIG. 1, the power measuring apparatus 10 includes a voltage detection unit 1, a current detection unit 2, a first AD conversion unit 3, a second AD conversion unit 4, a control unit 5, and a reference signal generator. Unit 6 and storage unit 7. The power measuring apparatus 10 is configured to sample instantaneous values such as voltage and current supplied from the AC power supply 20 to the load 21 and measure power from the sampled results.

  The voltage detection unit 1 is connected to the first AD conversion unit 3 as shown in FIG. 1, detects the voltage supplied from the AC power supply 20 to the load 21, and outputs a signal based on the detected voltage value to the first AD Output to the converter 3.

  The current detection unit 2 is connected to the second AD conversion unit 4 as shown in FIG. 1, detects the current supplied from the AC power supply 20 to the load 21, and outputs a signal based on the detected current value to the second AD Output to the converter 4.

  As shown in FIG. 1, the first AD conversion unit 3 is connected to the voltage detection unit 1 and the control unit 5, samples a signal output from the voltage detection unit 1 according to the control of the control unit 5, and the sampled signal The voltage data obtained by converting the value into a digital value is output to the control unit 5.

  As shown in FIG. 1, the second AD conversion unit 4 is connected to the current detection unit 2 and the control unit 5, samples a signal output from the current detection unit 2 according to the control of the control unit 5, and the sampled signal The current data obtained by converting the value into a digital value is output to the control unit 5.

  As shown in FIG. 1, the control unit 5 is connected to the first AD conversion unit 3, the second AD conversion unit 4, the reference signal generation unit 6, and the storage unit 7, and includes an output port 5a. . The control unit 5 has a built-in control program that describes the control procedure, performs control according to the control program, and synchronizes with the reference signal supplied from the reference signal generator 6 and the first AD converter 3 and the first 2 controls the sampling operation of the AD converter 4. Further, the control unit 5 acquires the voltage data output from the first AD conversion unit 3 and the current data output from the second AD conversion unit 4 and stores the acquired voltage data in the storage unit 7, and the voltage data signal The power value is obtained by calculating the current data signal. The control unit 5 stores the power value obtained by the calculation in the storage unit 7, and outputs the calculation result from the output port 5a to an external device (not shown).

  The reference signal generation unit 6 is connected to the control unit 5 as shown in FIG. 1 and supplies the control unit 5 with a reference signal that serves as a reference for timing when the control unit 5 performs control.

  As shown in FIG. 1, the storage unit 7 is connected to the control unit 5, and the control unit 5 acquires the data from the first AD conversion unit 3 and the second AD conversion unit 4 by writing data from the control unit 5. The voltage data and current data, and the power value obtained by the calculation by the control unit 5 are stored.

  Next, the power measurement method of this embodiment will be described with reference to FIG.

  FIG. 2 is a diagram for explaining a power measurement method according to the embodiment of the present invention. The signal waveform of the AC power supply 20 and the timing at which the first AD conversion unit 3 and the second AD conversion unit 4 perform sampling are illustrated. It is a timing chart which shows.

  The control unit 5 includes a plurality of sampling periods obtained by dividing the period of the AC power supply 20 into N equal parts (N is a natural number) and a plurality of sampling periods that are divided into M equal parts (M is a natural number). Sampling timing is preset by a program. Here, a case where the value of N is 4 and the value of M is 3 will be described.

  As shown in FIG. 2, the AC power supply 20 is divided into four equal periods, and four sampling periods of a first period, a second period, a third period, and a fourth period are set. In the fourth period, three sampling timings indicated by a, b, and c in FIG. 2 are set, respectively.

  The control unit 5 controls the first AD conversion unit 3 and the second AD conversion unit 4 in the period of the first cycle T1 shown in FIG. 2, and performs sampling in the first period that is an odd-numbered sampling period. Control to do.

  The control unit 5 acquires the voltage data and current data sampled at the sampling timing a in the first period shown in FIG. 2 from the first AD conversion unit 3 and the second AD conversion unit 4 and stores them. Store in the unit 7.

  The control unit 5 calculates the power value by calculating the acquired voltage data and current data, and causes the storage unit 7 to store the calculated power value.

  Next, the control unit 5 acquires the voltage data and current data sampled at the sampling timing of b in the first period shown in FIG. 2 from the first AD conversion unit 3 and the second AD conversion unit 4 and stores them. Store in the unit 7.

  The control unit 5 calculates the power value by calculating the acquired voltage data and current data, and causes the storage unit 7 to store the calculated power value. In addition, the power value obtained from the voltage data and current data at the sampling timing of a in the first period obtained previously and the power value obtained from the voltage data and current data at the sampling timing of b are integrated and the result is obtained. Store in the storage unit 7.

  Subsequently, the control unit 5 obtains voltage data and current data sampled at the sampling timing of c in the first period shown in FIG. 2 from the first AD conversion unit 3 and the second AD conversion unit 4 and stores them. Store in the unit 7.

  The control unit 5 calculates the power value by calculating the acquired voltage data and current data, and causes the storage unit 7 to store the calculated power value. Also, the power obtained from the value obtained by integrating the power values obtained from the voltage data and current data at the sampling timings a and b in the first period obtained earlier, and the voltage data and current data at the sampling timing of c. The values are integrated and the result is stored in the storage unit 7.

  Next, the control unit 5 controls the first AD conversion unit 3 and the second AD conversion unit 4 so as to perform sampling in a third period that is an odd-numbered sampling period.

  The control unit 5 sequentially acquires voltage data and current data sampled at the sampling timing of the third period and stores them in the storage unit 7. Further, the obtained voltage data and current data are sequentially calculated to obtain a power value, the obtained power value is stored in the storage unit 7, and the obtained power value with respect to the power value accumulated in the first period is obtained. The result of integration is stored in the storage unit 7.

  Next, the control unit 5 controls the first AD conversion unit 3 and the second AD conversion unit 4 in the period of the second period T2 shown in FIG. Control to perform sampling in a period.

  The control unit 5 acquires the voltage data and current data sampled at the sampling timing a in the second period shown in FIG. 2 from the first AD conversion unit 3 and the second AD conversion unit 4 and stores them. Store in the unit 7.

  The control unit 5 calculates the power value by calculating the acquired voltage data and current data, and causes the storage unit 7 to store the calculated power value. Further, the obtained voltage data and current data are calculated to obtain a power value, and the obtained power value is stored in the storage unit 7 and integrated in the first period and the third period of the first period T1. The obtained power value is integrated with respect to the power value, and the result is stored in the storage unit 7.

  The control unit 5 sequentially acquires voltage data and current data sampled at the sampling timing of the second period, and stores them in the storage unit 7. In addition, the obtained voltage data and current data are sequentially calculated to obtain a power value, the obtained power value is stored in the storage unit 7, and the obtained power value is accumulated with respect to the accumulated power value. Store in the storage unit 7.

  Next, the control unit 5 controls the first AD conversion unit 3 and the second AD conversion unit 4 so as to perform sampling in a fourth period which is an even-numbered sampling period.

  The control unit 5 sequentially acquires voltage data and current data sampled at the sampling timing of the fourth period, and stores them in the storage unit 7. In addition, the obtained voltage data and current data are sequentially calculated to obtain a power value, the obtained power value is stored in the storage unit 7, and the obtained power value is accumulated with respect to the accumulated power value. Store in the storage unit 7.

  As described above, by integrating the power calculated in the first cycle T1 and the second cycle T2, it is possible to measure the power for one power cycle.

  Thereafter, the power can be continuously measured by alternately repeating the first period T1 and the second period T2 and measuring.

  Hereinafter, the effect by having set it as this embodiment is demonstrated.

  The power measurement method according to the present embodiment is a power measurement method in which instantaneous values such as voltage and current supplied from the AC power supply 20 to the load 21 are sampled, and the power is measured from the sampled results. A plurality of sampling periods obtained by dividing the period into N and a plurality of sampling timings for performing sampling in the sampling period, and calculating power from a result of sampling in an odd-numbered sampling period in the sampling period. The cycle T1 and the second cycle T2 in which power is calculated from the results of sampling in the even-numbered sampling period are alternately repeated, and the power calculated in the first cycle T1 and the second cycle T2 is integrated. The power was measured.

  Thus, the first period T1 in which power is calculated from the result of sampling in the odd-numbered sampling period in the sampling period, and the second period in which power is calculated from the result of sampling in the even-numbered time zone. T2 and are repeated alternately. For this reason, the period for accumulating data obtained by sampling is completed in two power supply cycles, and the amount of data to be accumulated does not increase. Therefore, a memory having a small capacity for storing data obtained by sampling is used. It becomes possible. In addition, since the period for accumulating data obtained by sampling is short, the period that is affected by fluctuations in the power supply cycle is shortened, and the reduction in accuracy can be suppressed. Therefore, it is possible to provide a power measurement method capable of performing sampling with high accuracy without increasing the data amount.

  As described above, the power measurement method according to the embodiment of the present invention has been specifically described. However, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention. Is possible. For example, the present invention can be modified as follows, and these embodiments also belong to the technical scope of the present invention.

  (1) In this embodiment, a plurality of sampling periods obtained by dividing the period of the AC power supply 20 into N equal parts are divided into four periods from the first period to the fourth period, and the timing when the sampling period is equally divided into M is Although the description has been given by showing an example that is equally divided into three, the values may be changed as appropriate so as to obtain desired accuracy and resolution.

  (2) In this embodiment, the timing for starting measurement is not particularly described. For example, the timing is determined by detecting a zero crossing point that crosses zero when the voltage signal changes from negative to positive or from positive to negative. You may make it adjust.

DESCRIPTION OF SYMBOLS 1 Voltage detection part 2 Current detection part 3 1st AD conversion part 4 2nd AD conversion part 5 Control part 5a Output port 6 Reference signal generation part 7 Memory | storage part 10 Electric power measurement apparatus

Claims (1)

It is a power measurement method that samples instantaneous values such as voltage and current supplied from an AC power source to a load, and measures power from the sampled results.
A plurality of sampling periods obtained by dividing the period of the AC power supply into N equal parts (N is a natural number) and a plurality of sampling timings for performing sampling in the sampling period;
Among the sampling periods, a first cycle in which power is calculated from the result of sampling in the odd-numbered sampling period and a second cycle in which power is calculated from the result of sampling in the even-numbered sampling period alternately Repeat to
A method for measuring power, wherein the power is measured by integrating the power calculated in the first period and the second period.