JP5489331B2 - Power measuring device - Google Patents

Description

  The present invention relates to a power measuring apparatus that measures power by multiplying a detected voltage signal and a current signal.

  Conventionally, as this type of power measurement device, analog waveforms of voltage signals and current signals respectively output from the voltage detection circuit and the current detection circuit are AD (analog-digital) converted into digital values, and these digital values are multiplied. Thus, there is known one that measures electric power (see, for example, Patent Document 1).

  When A / D conversion is performed on analog waveforms of voltage and current signals, phase shifts (time differences) occur between the voltage and current signals due to sensor variations, circuit processing methods (filter constants), circuit constant variations, etc. It is known that the power calculation error increases.

  Conventionally, in order to solve this problem, a phase shift circuit (phase adjustment circuit) that corrects a phase shift (time shift of a signal waveform) is provided by hardware to adjust the phase (time). FIG. 12 is a diagram showing a configuration of a conventional power measuring apparatus. This conventional power measurement apparatus 650 includes a voltage detection circuit 610, a current detection circuit 620, and a power calculation unit 630.

  The voltage detection circuit 610 steps down to a voltage suitable for detection by the voltage step-down circuit 611, performs filtering by the filter 612, and then outputs a voltage signal in which the phase shift is adjusted by the phase adjustment circuit 613. The current detection circuit 620 switches the current sensor CT11 or CT12 connected to the circuit by the circuit switching unit 623, detects the R-phase or T-phase current by the switched current sensor CT11 or CT12, and detects the detected current signal. Is amplified by the gain switching unit 624 and output.

  The power calculation unit 630 performs AD conversion on the analog waveforms of the voltage signal and the current signal output from the voltage detection circuit 610 and the current detection circuit 620, respectively, by the AD conversion units 631 and 632. In addition, the power calculation unit 630 multiplies the digital values of the current signal and the voltage signal subjected to AD conversion by the multiplication unit 634, and outputs the multiplied value as a power value through the transmission circuit unit 635. Further, the power calculation unit 630 is provided with a gain switching control unit 633 that instructs the gain switching unit 624 to switch the gain at the time of current signal amplification. The voltage signal whose phase shift is adjusted by the phase adjustment circuit 613 is input to the AD conversion unit 631 in the power calculation unit 630. Such an operation corrects the phase shift between the detected voltage signal and current signal, and improves the accuracy of the measured power.

  FIG. 13 is a diagram showing a configuration of a power measuring device in the case of measuring the power of a multi-circuit. The current detection circuit 720 in the power measuring device 750 includes a circuit switching unit 723 that switches a plurality of current sensors CT11 to CT18 that detect R-phase or T-phase currents of the circuits 1 to 4, and a current signal with a predetermined gain. A gain switching unit 724 for amplification is provided. Further, the voltage detection circuit 710 is provided with a plurality of phase adjustment circuits 714 and a circuit switching unit 715 corresponding to the plurality of current sensors. When the current sensor is switched, the circuit switching unit 715 switches the phase adjustment circuit 714 corresponding thereto. The power calculation unit 730 is provided with a circuit switching control unit 736 and instructs the circuit switching unit 715 of the voltage detection circuit 710 to switch circuits.

Japanese Patent No. 3045739

  However, in the above-described conventional power measurement device, a phase adjustment circuit must be provided by hardware in the voltage detection circuit, which increases the cost. In particular, when many types of current sensors are used as the current detection unit in the current detection circuit, many phase adjustment circuits must be provided in the voltage detection circuit according to the type of the current sensor. For this reason, since the several phase adjustment circuit and the circuit switching part are required, the subject that cost rose further occurred.

  Further, a current transformer (CT) that is generally used as a current sensor for detecting a current has a large phase shift in a region where the current is small. In a region where the current is small, there is a problem that the accuracy of the measured power is reduced due to a large phase shift (time difference).

  The present invention has been made in view of the above circumstances, and its purpose is to easily correct a phase shift without increasing the cost and improve measurement accuracy even when many types of current sensors are used in a current detection circuit. An object of the present invention is to provide a power measuring device that can be improved. Another object of the present invention is to provide a power measuring device capable of suppressing a decrease in accuracy of power measurement even in a region where the current is small.

The present invention is provided with a voltage conversion unit that converts a voltage signal output from a voltage detection circuit that detects a voltage of a measurement target circuit into a first digital value, and a current detection unit that detects a current of the measurement target circuit. A current converter for converting a current signal output from the current detection circuit into a second digital value; a first digital value converted by the voltage converter; and a second digital value converted by the current converter A power measurement device that obtains a power value in a circuit to be measured from a multiplication result by the multiplication unit, and outputs a voltage signal output from the voltage detection circuit and the current detection circuit A phase shift amount setting unit for setting a phase shift amount relating to a phase shift with respect to a current signal to be generated, and a digital signal of the voltage signal in the voltage conversion unit based on the set phase shift amount A time adjustment unit that performs time adjustment by shifting at least one of a first timing for performing conversion and a second timing for performing digital conversion of the current signal in the current conversion unit; The setting unit sets a phase shift amount according to the type of the current detection unit, and when the current signals of different measurement target circuits are captured in a time division manner by different current detection units, the phase shift amount is set for each current detection unit. The time adjustment unit changes the order of timing for performing digital conversion of the voltage signal and timing for performing digital conversion of the current signal when performing the time adjustment in accordance with the phase shift amount. Provided is a power measuring device.
With the above configuration, a phase shift amount corresponding to the type of the current detection unit is set, and based on this phase shift amount, time adjustment is performed with respect to timing for performing digital conversion of the voltage signal and the current signal, so that accuracy is easily achieved It is possible to correct the phase shift well. Therefore, even when many types of current sensors are used in the current detection circuit, it is possible to correct the phase shift and increase the accuracy of power measurement without increasing the cost.
For example, even when the amount of phase shift is large, changing the order of execution timing of digital conversion may shorten the entire capturing time when capturing current signals of a plurality of measurement target circuits in a time-sharing manner. Can be. Therefore, it is possible to shorten the sampling cycle when measuring power.

The present invention also includes a voltage conversion unit that converts a voltage signal output from a voltage detection circuit that detects the voltage of the measurement target circuit into a first digital value, and a current detection unit that detects the current of the measurement target circuit. A current converter that converts the current signal output from the current detection circuit into a second digital value; a first digital value that is converted by the voltage converter; and a second that is converted by the current converter. A power measuring device that obtains a power value in a circuit to be measured from a multiplication result of the multiplication unit, the voltage signal output from the voltage detection circuit, and the current detection circuit A phase shift amount setting unit for setting a phase shift amount relating to a phase shift with respect to the current signal output from the current signal, and based on the set phase shift amount, the voltage signal in the voltage conversion unit A first timing to perform digital conversion, and a second time adjusting unit that performs time adjustment by shifting at least one of the timing for performing digital conversion of the current signal in the current conversion unit, by the current detecting circuit and a current value determination unit determines a current value detected, the phase shift amount setting unit sets the phase shift amount according to the type of the current detector, the said current value is less than a predetermined value Different phase shift amounts are set in the first region and the second region equal to or greater than the predetermined value, and the time adjustment unit determines that the current value is the predetermined value according to the current value determined by the current value determination unit. If smaller than the value, time adjustment is performed based on the phase shift amount set in the first region. If the current value is equal to or greater than the predetermined value, the phase shift amount set in the second region is set. On the basis of To provide power measuring apparatus which performs between adjustments.
With the above configuration, the measurement power accuracy in the region where the current value is small can be improved by performing time adjustment by setting different phase shift amounts in the region where the current value is small.

The present invention also includes a voltage conversion unit that converts a voltage signal output from a voltage detection circuit that detects the voltage of the measurement target circuit into a first digital value, and a current detection unit that detects the current of the measurement target circuit. A current converter that converts the current signal output from the current detection circuit into a second digital value; a first digital value that is converted by the voltage converter; and a second that is converted by the current converter. A power measuring device that obtains a power value in a circuit to be measured from a multiplication result of the multiplication unit, the voltage signal output from the voltage detection circuit, and the current detection circuit A phase shift amount setting unit for setting a phase shift amount relating to a phase shift with respect to the current signal output from the current signal, and based on the set phase shift amount, the voltage signal in the voltage conversion unit A first timing to perform digital conversion, and a second time adjusting unit that performs time adjustment by shifting at least one of the timing for performing digital conversion of the current signal in the current conversion unit, by the current detecting circuit and a current value determination unit determines a current value detected, the phase shift amount setting unit sets the phase shift amount according to the type of the current detector, a predetermined function corresponding to the current value A power measuring device configured to adjust the time based on the phase shift amount corresponding to the current value according to the current value determined by the current value determination unit. To provide .
With the above configuration, by performing the time adjustment based on the phase shift amount corresponding to the current value, it becomes possible to correct the phase shift more finely and further improve the accuracy of power measurement.

  According to the present invention, even when many types of current sensors are used in the current detection circuit, the phase shift can be easily corrected without increasing the cost, and the measurement accuracy can be improved. In addition, even in a region where the current is small, it is possible to suppress a decrease in the accuracy of power measurement.

The figure which shows the structure of the electric power measurement apparatus in 1st Embodiment. Diagram showing an example of the relationship between the current sensor rating and phase shift Flow chart showing the procedure of power measurement in this embodiment (A)-(D) is a figure explaining the improvement of power calculation accuracy The figure which shows the structure of the electric power measurement apparatus in 2nd Embodiment. The figure which shows the structure of the electric power measurement apparatus in 3rd Embodiment. (A)-(C) is a figure which shows the order of AD conversion of the voltage signal and current signal performed over the R phase of the some circuits 1-4, and T phase. The figure which shows the structure of the electric power measurement apparatus in 4th Embodiment. (A), (B) is a graph which shows the change of the power calculation error rate with respect to an energization current. (A), (B) is a graph which shows the change of the value of adjustment time (DELTA) t with respect to the electric current value of an energization current, and a power calculation error rate. The figure which shows the structure of the electric power measurement apparatus in 5th Embodiment. Diagram showing the configuration of a conventional power measurement device The figure which shows the structure of the electric power measurement device in the case of measuring the electric power of the multi-circuit

  In the following embodiments, as an example of a power measurement device according to the present invention, a configuration of a power measurement device that measures power supplied to a power distribution circuit connected to a commercial AC power supply is shown.

(First embodiment)
FIG. 1 is a diagram illustrating a configuration of a power measuring device according to the first embodiment. The power measurement device 50 includes a voltage detection circuit 10, a current detection circuit 20, and a power calculation unit 30. The voltage detection circuit 10 detects R-phase and T-phase line voltages (voltage RS, voltage TS), which are two-phase voltages of a commercial AC power supply that is a measurement target circuit. The voltage detection circuit 10 includes a voltage step-down circuit 11 that detects a line voltage and steps down the detected line voltage to a voltage signal suitable for detection, and a filter that removes power supply noise from the stepped-down voltage signal. 12 is provided. The voltage signal that has passed through the filter 12 is input to the power calculator 30.

  The current detection circuit 20 detects each phase current flowing in the R-phase and T-phase power lines of the commercial AC power supply that is the measurement target circuit. The current detection circuit 20 is provided with current sensors CT1 and CT2 that are provided in the R-phase and T-phase power supply lines, respectively, and detect each phase current as a current detection unit. The current detection circuit 20 includes a circuit switching unit 23 that switches current sensors CT1 and CT2 according to a selection signal, which will be described later, and a gain switching unit 24 that switches an amplification factor (gain) of the current signal detected by the current sensors CT1 and CT2. doing.

  The gain switching unit 24 increases the amplification factor (gain) according to the level of the detected current signal based on an instruction from the gain switching control unit 33 in the power calculation unit 30 described later in order to increase the resolution of AD conversion described later. ) In stages. The gain switching unit 24 also receives a gain switching signal and selection signals for the current sensors CT1 and CT2 from the gain switching control unit 33 in the power calculation unit 30. The gain switching unit 24 outputs this selection signal to the circuit switching unit 23. Here, as the current sensor, a through-type or split-type current transformer (CT) or the like is generally used.

  The power calculation unit 30 is configured by an information processing device such as a microcomputer, and implements functions of each unit to be described later along with built-in hardware by executing a control program (software) stored in a storage medium. . That is, the power calculation unit 30 includes AD conversion units 31 and 32, a gain switching control unit 33, a multiplication unit 34, a transmission circuit unit 35, a time adjustment unit 36, and a phase shift amount setting unit 37. The AD converter 31 converts the analog waveform of the voltage signal detected by the voltage detection circuit 10 into a digital value (a first digital value indicating a voltage). The AD converter 32 converts the analog waveform of the current signal detected by the current detection circuit 20 into a digital value (second digital value indicating current). Here, the first AD converter 31 realizes the function of the voltage converter, and the second AD converter 32 realizes the function of the current converter.

  As described above, the gain switching control unit 33 outputs a gain switching signal and selection signals for the current sensors CT1 and CT2 to the gain switching unit 24.

  The multiplication unit 34 calculates a power value by multiplying the digital values (first digital value and second digital value) converted by the AD conversion units 31 and 32, respectively, and the power calculated as a result of the multiplication The value is output to the transmission circuit unit 35. The transmission circuit unit 35 outputs the calculated power value to the outside. The output power value can be displayed on a display device, for example, and can be transmitted to an external device via a transmission line such as a network.

  Based on the phase shift amount set in the phase shift amount setting unit 37, the time adjustment unit 36 performs a first timing for performing AD conversion of the voltage signal on each of the AD conversion units 31 and 32, and AD of the current signal. A trigger signal for determining the second timing for executing the conversion is individually output. As the first and second timings for executing AD conversion, for example, timings for taking in voltage signals and current signals in the AD conversion units 31 and 32, that is, AD conversion start timings, and the like are set, for example. Thereby, as will be described later, the phase shift between the voltage signal and the current signal is adjusted.

  In the phase shift amount setting unit 37, a phase shift amount (adjustment time) Δt at which the phase shift unit 36 adjusts the phase shift is set. The time adjustment performed by the time adjustment unit 36 is a first timing for executing AD conversion of the voltage signal (capturing the voltage signal), or executing AD conversion of the current signal (capturing the current signal). It may be performed for one or both of the two timings. Further, as timing for executing AD conversion, the input timing of the voltage signal and current signal in the AD conversion units 31 and 32, or the output of the first digital value after voltage conversion and the second digital value after current conversion, are output. It is also possible to use timing or the like.

  In this embodiment, as will be described later, the case where the current signal is delayed with respect to the voltage signal is shown. However, depending on the circuit, the voltage signal may be delayed with respect to the current signal. Is possible.

  The phase shift amount (adjustment time) Δt for adjusting the phase shift needs a resolution and an adjustment range necessary for adjusting the measurement power accuracy at a power factor of 0.5. For example, when the power calculation error rate is set to an error range of 0.3% or less at a power factor of 0.5, it is necessary to adjust the phase shift amount (adjustment time) Δt to about 5 μsec or less.

  Further, the phase shift amount (adjustment time) Δt varies depending on the type of current detection unit including the type of current sensor (penetrating type, split type, etc.), rated current, individual difference (variation among individual sensors), and the like. The current transformer (CT) used as a current sensor has a rated current indicating a current range that can be detected according to the detected current for each type. If the rated current is different, the shape of the current transformer is different, so the amount of phase shift is also different. Therefore, the phase shift amount setting unit 37 is set with a phase shift amount (adjustment time) Δt corresponding to the type of the current detection unit such as the type of the current sensor, the rated current, and the individual difference. At this time, the phase shift amount (adjustment time) Δt is not only the cause of the current detection circuit including the type of the current detection unit, but also the processing method (circuit difference, etc.) of the circuit such as a filter in the voltage detection circuit, It is preferable to set in consideration of factors of the voltage detection circuit due to variations in constants and the like. Thereby, it is possible to set the phase shift amount (adjustment time) Δt of the entire apparatus including the voltage detection circuit 10 and the current detection circuit 20 for many types of current sensors. Although only one phase shift amount (adjustment time) Δt is described here, the adjustment time is actually set for each phase circuit of the R phase (first circuit) and the T phase (second circuit). Δt1 and Δt2 are set respectively.

  FIG. 2 is a table showing an example of the relationship between the rating of the current sensor and the phase shift. This table is registered in the phase shift amount setting unit 37. Further, in this table, as a phase shift amount corresponding to the rated current of the current sensor, a variation due to the median value of the phase shift for each rated current and individual differences is shown. For example, in the case of a current sensor (CT) for a rated 50 A, it is shown that the median value of the phase shift is + 2 ° and the variation of individual differences is ± 1 °. In addition, in the case of a current sensor (CT) for a rated 100A, the median value of the phase shift is + 1 °, and the variation due to individual differences is ± 1 °. A value obtained by adding variation due to individual differences to the median value of the phase shift for each rating of the current sensor is the phase shift due to the actual current sensor. As described above, the current sensor has the characteristic of the leading phase, and the magnitude of the phase shift differs depending on the current sensor, but it may be adjusted in the range of 0 to 3 °.

  For example, when a current sensor for a rating of 50 A is connected to the R-phase power line of the circuit 1 as a circuit to be measured, a median value of + 2 ° is used as the phase shift. When a current sensor for a rating of 400 A is connected to the T-phase power line of the circuit 1 as a circuit to be measured different from the above, a median value of + 1 ° is used as the phase shift. Then, the phase shift amount (adjustment time) Δt corresponding to these phase shifts is actually set.

  In consideration of variations due to individual differences among current sensors, the phase shift amount (adjustment time) Δt may be set by actually measuring the phase shift when individual current sensors are connected. In this case, the phase shift caused by the current sensor can be corrected more accurately.

  Further, when it is necessary to consider the phase shift caused by changing the constant of the filter 12 in the voltage detection circuit 10, as shown in the equation (1), the adjustment time Δt (fil) due to the phase shift in the filter And the adjustment time Δt (CT) due to the phase shift inherent to the current sensor may be used as the total phase shift amount (adjustment time) Δt to adjust the phase shift.

Δt = Δt (fil) + Δt (CT) (1)
Note that the phase shift amount by the filter is obtained by calculation, but may be obtained by detecting the phase difference between the voltage signal input in the manufacturing process and the voltage signal after passing through the filter.

  FIG. 3 is a flowchart showing the procedure of power measurement in the present embodiment. This power measurement process is repeated every predetermined time (in this embodiment, 1 msec which is a sampling period). When power measurement is started, the time adjustment unit 36 first sends a trigger signal to the AD conversion unit 31 that samples the voltage signal that is always output from the voltage detection circuit 10 and performs AD conversion, and performs AD conversion. (Step S1).

  The time adjustment unit 36 waits for the adjustment time Δt set in the phase shift amount setting unit 37 (step S2), and after the adjustment time Δt has elapsed, samples the current signal that is constantly output from the current detection circuit 20. A trigger signal is sent to the AD conversion unit 32 that performs AD conversion to perform AD conversion (step S3).

  The multiplying unit 34 multiplies the digital value (first digital value) of the voltage signal output from the AD converting unit 31 and the digital value (second digital value) of the current signal output from the AD converting unit 32. Then, the power value is calculated, and the calculated power value is output to the transmission circuit unit 35 (step S4). As a result, the power measurement process ends. And when predetermined time (1 msec which is a sampling period) passes since the last measurement, electric power measurement will be started again.

  The transmission circuit unit 35 accumulates power values every predetermined time (1 msec). The accumulated power value is output to the outside at preset time intervals and used for display, various data processing, and the like.

  FIG. 4 is a diagram for explaining improvement in power calculation accuracy. FIG. 4A is a graph showing the power calculation error rate with respect to the energized current when there is a phase shift. FIG. 4B is a time waveform diagram showing signal waveforms of a voltage signal and a current signal. FIG. 4B shows a signal waveform in which a phase shift caused by at least one of the voltage detection circuit and the current detection circuit occurs.

  FIG. 4C is a graph showing the power calculation error rate with respect to the energized current when the phase shift is adjusted. FIG. 4D is a time waveform diagram showing signal waveforms of the voltage signal and the current signal when the phase shift is adjusted. FIG. 4D shows a signal waveform in which the phase shift caused by at least one of the voltage detection circuit and the current detection circuit is adjusted.

  As shown in FIG. 4A, when there is a phase shift caused by the power measurement device, the power calculation error rate is in the range of 0.6 to 0.8% as shown by the dotted frame g. On the other hand, when the phase shift caused by the power measuring apparatus is adjusted, the power calculation error rate is improved within a range of −0.2 to 0.2% as indicated by a dotted frame h.

  In the power measuring apparatus of the first embodiment, the time adjustment is performed by shifting the timing for taking in the voltage signal and the current signal based on the phase shift amount, and the power calculation accuracy can be adjusted. The phase shift between the current signal and the voltage signal includes a phase shift due to the current sensor of the current detection unit and a phase shift due to another circuit such as a filter in the voltage detection circuit. For this reason, the accuracy of power measurement can be set by setting the amount of phase shift by combining the phase shift due to the type of current sensor in the current detector, the phase shift due to individual differences in the current sensor, the phase shift due to variations in parts in the circuit, etc. Can be improved. In this embodiment, the time lag between the voltage signal and the current signal taken into the AD converter is used as the phase lag amount. At this time, since the time adjustment is realized by adjusting the time difference of AD conversion by software, it can be easily adjusted individually, and the power calculation accuracy can be improved for each device. it can. Further, since the amount of time adjustment is also set by software setting, adjustment in the manufacturing process is easy.

  In the power measuring device, the current detection unit is used by changing the type according to the current range detected by the measurement target circuit. Therefore, the amount of phase shift differs depending on the type of current sensor in the current detection unit or individual differences.Therefore, setting the phase shift amount according to the type of current sensor or the phase shift amount specific to the current sensor Can be adjusted with higher accuracy. Furthermore, the accuracy of power measurement can be improved by calculating the sum of the phase shift amount inherent to the current detection unit and the phase shift amount of other circuits, and using this calculated value as the phase shift amount.

  As described above, according to the first embodiment, the power calculation error rate can be improved by adjusting the timing of AD conversion of the current signal and the voltage signal, and the accuracy of the measured power value can be improved. it can. In particular, since the adjustment time Δt is set for each current sensor, even if different types of current sensors such as types, rated currents, and individual differences are provided in the current detection circuit, no special circuit is required, and parts are added. Therefore, the phase shift can be corrected. Further, the phase shift can be corrected more accurately by taking into account the phase shift caused by the filter of the voltage detection circuit. Therefore, even when many types of current detection units are provided in the current detection circuit, it is possible to easily correct the phase shift without increasing the cost.

  In the present embodiment, as the type of current sensor, a case where a different phase shift amount is mainly set for each rated current has been shown, but the same applies to a phase shift amount that is different for each type of through type or divided type. It is possible to set.

  In this embodiment, when adjusting the phase shift between the voltage signal and the current signal, the AD conversion is performed by shifting the AD conversion start timing (timing for capturing the signal to be converted) as the AD conversion timing. The method is not limited to this. For example, it is possible to adjust by starting AD conversion start timing, accumulating digital values that are sequentially AD converted, and shifting the read timing of the stored digital values.

(Second Embodiment)
In the second embodiment, an example in which the set value of the phase shift amount is switched according to the power supply frequency is shown. FIG. 5 is a diagram illustrating a configuration of a power measuring device according to the second embodiment. In FIG. 5, the same components as those in the first embodiment are denoted by the same reference numerals.

  The power measuring device 150 of the second embodiment includes a power frequency determination unit 141 that determines whether the frequency of the commercial AC power source is 50 Hz or 60 Hz in the power calculation unit 130. The determination result by the power supply frequency determination unit 141 is input to the time adjustment unit 136. The time adjustment unit 136 adjusts the timing for executing AD conversion in the AD conversion units 31 and 32 based on the phase shift amount set in the phase shift amount setting unit 137 and the power frequency determination result by the power frequency determination unit 141, respectively. To do.

  The amount of phase shift in the current sensor becomes different when the power supply frequency is different. Assuming that the adjustment time Δt (fil) by the filter 12 and the adjustment time Δt (CT, Hz) by the current sensor that varies depending on the power supply frequency, the overall adjustment time Δt is obtained by the sum of these as shown in Equation (2). It is done. In the phase shift amount setting unit 137, the entire adjustment time Δt corresponding to the power supply frequency is registered as a table.

Δt = Δt (fil) + Δt (CT, Hz) (2)
As described above, according to the power measurement device of the second embodiment, by setting the phase shift amount according to the power supply frequency, even when the power supply frequency is different, the phase shift can be accurately adjusted and measured. Power accuracy can be improved.

(Third embodiment)
In the first and second embodiments described above, the R-phase and T-phase power measurements in one circuit (circuit 1) are shown. In the third embodiment, a plurality of measurement target circuits (circuits and phases) are provided. As an example, an example of R-phase and T-phase power measurement processing when power is supplied to a plurality of circuits (circuits 1 to 4) will be described.

  FIG. 6 is a diagram illustrating a configuration of a power measuring device according to the third embodiment. In FIG. 6, the same components as those in the first embodiment are denoted by the same reference numerals. In the current measuring circuit 250 according to the third embodiment, in the current detection circuit 220, the circuit switching unit 223 includes the current sensors CT1 and CT2 that detect the R-phase and T-phase currents of the circuit 1 and the R-phase of the circuit 2, respectively. , Current sensors CT3 and CT4 for detecting T-phase currents, current sensors CT5 and CT6 for detecting R-phase and T-phase currents of circuit 3, and R-phase and T-phase currents of circuit 4, respectively. Current sensors CT7 and CT8 are connected. The circuit switching unit 223 switches the plurality of current sensors CT1 to CT8 in order by receiving the selection signal transmitted from the gain switching control unit 233 in the power calculation unit 230 via the gain switching unit 224.

  In accordance with the switching of the current sensors CT1 to CT8, the power calculation unit 230 repeatedly performs power calculation in a time division order of circuit 1 → circuit 2 → circuit 3 → circuit 4 → circuit 1. At this time, the phase shift of the current signal from the current detection circuit 220 differs from circuit to circuit. In the phase shift amount setting unit 237, the adjustment time Δt for each of the R phase and the T phase of the circuits 1 to 4 is registered as a table. The time adjustment unit 236 adjusts the timing of executing AD conversion in the AD conversion units 31 and 32 based on the selection signal from the gain switching control unit 233 and the phase shift amount set in the phase shift amount setting unit 237, respectively. . At this time, when the selection signal from the gain switching control unit 233 is input, the time adjustment unit 236 reads the adjustment time Δt corresponding to the phase of the circuit switched by this selection signal from the phase shift amount setting unit 237. Then, for example, a trigger signal is output to the AD conversion unit 32 at the AD conversion start timing shifted by the adjustment time Δt. In this way, AD conversion of the current signal in each phase of each circuit is performed, and power is calculated.

  Here, when the number of circuits is increased to four circuits 1 to 4, the following examination is required. As described above, in this embodiment, the time for measuring power (sampling period) is set to 1 msec. When the adjustment time Δt of each circuit in the circuits 1 to 4 is long, the time (maximum cycle) required for AD conversion of the current signals of all the circuits is long, and is expected to exceed the set time (sampling cycle). Is done.

  Therefore, in the third embodiment, the AD conversion order of the voltage signal and current signal performed over the R phase and T phase of the plurality of circuits 1 to 4 is changed according to the adjustment time Δt of each circuit. Thus, control is performed to shorten the time required for all AD conversions.

  FIG. 7 is a diagram showing the order of AD conversion of the voltage signal and current signal performed over the R phase and T phase of the plurality of circuits 1 to 4. FIG. 7A shows the timing of AD conversion performed in the order of the R phase and the T phase without considering the conventional phase shift. In FIG. 7A, since the phase shift is not taken into consideration, AD conversion of the R-phase current signal and voltage signal is performed simultaneously, and then AD conversion of the T-phase current signal and voltage signal is performed simultaneously. As described above, the maximum period falls within the sampling period even if the entire circuit is covered because there is no time adjustment.

  FIG. 7B shows the timing of AD conversion performed in the order of the R phase and the T phase in consideration of the phase shift. In FIG. 7B, after the AD conversion of the R-phase current signal is performed, the AD conversion of the R-phase voltage signal is performed after the elapse of the adjustment time Δt1, and the AD conversion of the T-phase current signal is further performed. After the adjustment, AD conversion of the T-phase voltage signal is performed after the lapse of the adjustment time Δt2. When the adjustment times Δt1 and Δt2 are long, the maximum period over the entire circuit may exceed the sampling period, and sampling may not be in time.

  FIG. 7C shows the AD conversion timing of the voltage signal and the current signal, the order of which is changed according to the adjustment time Δt for each circuit in the present embodiment. In order to avoid that the maximum period as shown in FIG. 7B exceeds the sampling period, in the example of FIG. 7C, the order in which the AD conversion of the voltage signal and the current signal is performed in accordance with the adjustment time Δt. Changes are made.

  FIG. 7C shows 20 examples of changing the order. Here, the values n and m represent the adjustment time Δt and have a relationship of n <m. Hereinafter, some examples will be specifically described.

  In the case of No1, both the R-phase side and the T-phase side adjustment time Δt are equal to the value + n. In this case, first, AD conversion of R-phase and T-phase current signals is performed. Then, after the value n has elapsed as the adjustment time Δt, AD conversion of the R-phase and T-phase voltage signals is performed. As described above, since the standby for the adjustment time Δt is simultaneously performed in the R phase and the T phase, the cycle of one circuit is shortened and can be suppressed to 250 μsec or less.

  In the case of No2, the adjustment time Δt1 on the R phase side is a value + n, and the adjustment time Δt2 on the T phase side is a value + m. In this case, first, AD conversion of R-phase and T-phase current signals is performed. Then, after the value n has elapsed as the adjustment time Δt1, AD conversion of the R-phase voltage signal is performed. Further, after the time Δt2−Δt1 has elapsed, AD conversion of the T-phase voltage signal is performed. As described above, since the standby for the adjustment time Δt1 is simultaneously performed, the cycle of one circuit can be suppressed.

  In the case of No4, the adjustment time Δt1 on the R phase side is a value + n, and the adjustment time Δt2 on the T phase side is a value −n. On the T phase side, it is necessary to perform AD conversion of the voltage signal before the current signal. In this case, AD conversion of the R-phase current signal and the T-phase voltage signal is performed. Then, after the value n has elapsed as the adjustment time Δt, AD conversion of the R-phase voltage signal and the T-phase current signal is performed.

  In the case of No7, the adjustment time Δt1 on the R phase side is the value + n, and the adjustment time Δt2 on the T phase side is the value 0. On the T phase side, it is necessary to perform AD conversion of the current signal and the voltage signal substantially simultaneously. In this case, AD conversion of the R-phase current signal is performed, and AD conversion of the T-phase current signal and the T-phase voltage signal is performed. Then, after the value n has elapsed as the adjustment time Δt1, AD conversion of the R-phase voltage signal is performed.

  In the case of No18, the R-phase side adjustment time Δt1 and the T-phase side adjustment time Δt2 are both 0. In this case, since there is no phase shift, AD conversion of the R-phase and T-phase current signals and the R-phase and T-phase voltage signals is performed substantially simultaneously, as in the case where no consideration is given.

  As described above, in the power measuring apparatus according to the third embodiment, the AD conversion order is changed according to the adjustment time Δt, and AD conversion is performed in a short time for all the circuits in the order of No. 1 to No. 20 in FIG. To do. As a result, even when the phase shift amount is large, by changing the order of execution timing of AD conversion, the entire capturing time is shortened when capturing the current signals of a plurality of measurement target circuits in a time-sharing manner. Can be. In this case, since the cycle of each circuit is 250 μsec or less, the maximum cycle over all circuits can be kept within 1 msec, which is the sampling cycle, and the time for measuring power can be shortened.

  Also, when measuring the power of multiple measurement target circuits in time series, set the phase shift amount corresponding to each, and adjust the time by switching the phase shift amount. Accuracy can be improved. In addition, the voltage detection circuit and the current detection circuit corresponding to each measurement target circuit do not require a conventional phase adjustment circuit, so that the cost can be reduced.

  In this embodiment, the case where power is supplied to a plurality of circuits with the same voltage has been described. However, the present invention can be similarly applied to the case where power is supplied to a plurality of circuits with different voltages.

(Fourth embodiment)
In the fourth embodiment, an energization current value at which the accuracy of current detection is deteriorated is a region (first region) smaller than a predetermined value (for example, 12A) and a region (second region) equal to or greater than a predetermined value. The example which switches the setting value of phase shift amount is shown.

  FIG. 8 is a diagram illustrating a configuration of a power measurement device according to the fourth embodiment. In FIG. 8, the same components as those in the first embodiment are denoted by the same reference numerals. The power measurement apparatus 350 of the fourth embodiment includes a current value determination unit 345 that determines whether or not the detected current value is a region where the energization current is small in the power calculation unit 330. The phase shift amount setting unit 337 registers two values, an adjustment time Δts in the first region where the energization current is smaller than a predetermined value and an adjustment time Δtb in the second region where the energization current is greater than or equal to the predetermined value. Yes.

  Based on the digital value of the current signal converted by the AD conversion unit 32, the current value determination unit 345 determines whether the energization current is in a region smaller than a predetermined value, and outputs the determination result to the time adjustment unit 336. To do. The time adjustment unit 336 adjusts the timing for executing AD conversion in the AD conversion units 31 and 32 based on the determination result by the current value determination unit 345, respectively. At this time, the time adjustment unit 336 reads the adjustment time Δt (Δts or Δtb) registered in the phase shift amount setting unit 37. For example, the trigger signal is output to the AD converter 32 at the timing after the adjustment time Δt has elapsed, and AD conversion of the current signal is performed.

  FIG. 9 is a graph showing changes in the power calculation error rate with respect to the energization current. FIG. 9A shows a case where the same phase shift amount is set without dividing the region. That is, in all the regions, the adjustment time Δt is set to the same value Δtb. As a characteristic of the current sensor, in a region where the energization current value is small, the phase shift becomes large, and in the case of a current with a poor power factor (for example, power factor 0.5), the accuracy of the measured power value decreases. In the illustrated example, it can be seen that in the region where the energized current is small (first region), the smaller the energized current, the worse the power calculation error rate, and the value decreases to near -1.0%.

  FIG. 9B shows a case where different phase shift amounts are set in the first region where the energization current is smaller than the predetermined value and the second region where the energization current is larger than the predetermined value. That is, the adjustment time in the first region is set to a value Δts that is larger than the value Δtb in the second region. In this case, in the first region, it can be seen that the power calculation error rate is improved and falls within the range of the value ± 0.6%.

  As described above, according to the power measurement device of the fifth embodiment, by adjusting the time by setting an appropriate phase shift amount (for example, a large adjustment time) different from the large region in the region where the energization current value is small. In addition, it is possible to appropriately correct a phase shift that occurs significantly in a region where the energization current value is small. Thereby, even if it is an area | region where a current value is small, the fall of the precision of electric power measurement can be suppressed, and a measurement electric power precision can be improved in the wide range of an electric current value.

  In the present embodiment, the case where the current region is divided into two is shown, but it is also possible to set the set value (adjustment time) of the phase shift amount by further dividing the current region into two or more. In that case, further improvement in measurement power accuracy is expected.

  Further, the adjustment time Δt may be defined as a predetermined function corresponding to the current value of the energization current. FIG. 10 is a graph showing changes in the adjustment time Δt and the power calculation error rate with respect to the current value of the energization current.

  When the current value of the energization current is a variable i (A), the adjustment time Δt (i) is defined as shown in FIG. In FIG. 10B, the value set as the adjustment time Δt is set in the range of 1.0 to −1.0. The adjustment time Δt (i) is registered in the phase shift amount setting unit 337 as an equation or a table. In this case, the time adjustment unit 336 reads the adjustment time Δt (i) corresponding to the current value (i) from the phase shift amount setting unit 337 based on the current value (i) detected by the current value determination unit 345. Adjust the amount of phase shift.

  As a result, as shown in FIG. 10A, when the adjustment time Δt (i) is used, the power calculation error rate causes a step between the first and second regions as in the example of FIG. Without continuously changing within a range of ± 0.2%. Therefore, finer phase shift adjustment is possible, and the measurement power accuracy can be further improved.

(Fifth embodiment)
The fifth embodiment shows an example in which phase shift information is held in the current sensor unit. FIG. 11 is a diagram illustrating a configuration of a power measurement device according to the fifth embodiment. FIG. 11A shows the overall configuration of the power measuring apparatus, and FIG. 11B shows the configuration of the current sensor unit. In FIG. 11, the same components as those in the first embodiment are denoted by the same reference numerals.

  In the power measurement device 450 of the fourth embodiment, in the current detection circuit 420, the current sensor units 421 and 422 are connected in an exchangeable manner. The current sensor units 421 and 422 are provided with current sensors CT1 and CT2 and phase shift information storage units 421a and 422a, respectively. The phase shift information storage units 421a and 422a are composed of, for example, a nonvolatile memory (EEPROM), and hold information on the phase shift amounts of the current sensors CT1 and CT2.

  The power calculation unit 430 includes a phase shift information input unit 448 that inputs information on each phase shift amount stored in the phase shift information storage units 421a and 422a in the current sensor units 421 and 422. The phase shift amount setting unit 437 receives the phase shift amount of the current sensor CT1 and the phase shift amount of the current sensor CT2 from the phase shift information input unit 448. AD conversion time adjustment by the time adjustment unit 36 is the same as in the above-described embodiment.

  As described above, according to the power measuring apparatus of the fifth embodiment, since the information on the phase shift amount is stored in each current sensor unit, the adjustment time Δt including the variation due to the individual difference for each current sensor is obtained. Setting can be easily performed, and the measurement power accuracy can be improved. Further, when the current sensor unit manufacturer or assembly manufacturer manufactures the current sensor unit, the phase shift amount can be stored for each current sensor.

  The present invention is intended to be variously modified and applied by those skilled in the art based on the description in the specification and well-known techniques without departing from the spirit and scope of the present invention. Included in the scope for protection. Moreover, you may combine each component in the said embodiment arbitrarily in the range which does not deviate from the meaning of invention.

  For example, in each of the above-described embodiments, the case where the power supplied to the circuit connected to the commercial AC power supply of the V connection method is measured, but the power from the three-phase AC power supply of other methods is measured. The present invention is also applicable to the case of measuring power from a single-phase AC power source.

DESCRIPTION OF SYMBOLS 10 Voltage detection circuit 20,220,420 Current detection circuit 23,223 Circuit switching part 24,224 Gain switching part 30,130,230,330,430 Power calculating part 31,32 AD conversion part 33,233 Gain switching control part 34 Multiplier 36, 136, 236, 336 Time adjustment unit 37, 137, 237, 337, 437 Phase shift amount setting unit 50, 150, 250, 350, 450 Power measurement device 141 Power frequency determination unit 345 Current value determination unit 421 422 Current sensor unit 421a, 422a Phase shift information storage unit 448 Phase shift information input unit CT1-CT8 Current sensor

Claims (3)

A voltage conversion unit that converts a voltage signal output from a voltage detection circuit that detects a voltage of a circuit to be measured into a first digital value;
A current conversion unit that converts a current signal output from a current detection circuit provided with a current detection unit that detects a current of a circuit to be measured into a second digital value;
A multiplication unit that multiplies the first digital value converted by the voltage conversion unit and the second digital value converted by the current conversion unit, and the power value in the measurement target circuit from the multiplication result by the multiplication unit A power measuring device for obtaining
A phase shift amount setting unit for setting a phase shift amount related to a phase shift between the voltage signal output from the voltage detection circuit and the current signal output from the current detection circuit;
Based on the set phase shift amount, a first timing for performing digital conversion of the voltage signal in the voltage conversion unit and a second timing for performing digital conversion of the current signal in the current conversion unit. A time adjustment unit that adjusts the time by shifting at least one of them,
The phase shift amount setting unit sets a phase shift amount according to the type of the current detection unit, and when acquiring current signals of different measurement target circuits by different current detection units in time division, the current detection unit Set the phase shift amount,
The time adjustment unit performs power measurement for changing the order of timing for performing digital conversion of the voltage signal and timing for performing digital conversion of the current signal when performing the time adjustment according to the phase shift amount. apparatus. A voltage conversion unit that converts a voltage signal output from a voltage detection circuit that detects a voltage of a circuit to be measured into a first digital value;
A current conversion unit that converts a current signal output from a current detection circuit provided with a current detection unit that detects a current of a circuit to be measured into a second digital value;
A multiplication unit that multiplies the first digital value converted by the voltage conversion unit and the second digital value converted by the current conversion unit, and the power value in the measurement target circuit from the multiplication result by the multiplication unit A power measuring device for obtaining
A phase shift amount setting unit for setting a phase shift amount related to a phase shift between the voltage signal output from the voltage detection circuit and the current signal output from the current detection circuit;
Based on the set phase shift amount, a first timing for performing digital conversion of the voltage signal in the voltage conversion unit and a second timing for performing digital conversion of the current signal in the current conversion unit. A time adjustment unit that adjusts the time by shifting at least one of them;
And a current value determination unit determines a current value detected by the current detection circuit,
The phase shift amount setting unit sets a phase shift amount according to the type of the current detection unit, and the phase of the current value is different between a first region smaller than a predetermined value and a second region greater than the predetermined value. Set the amount of deviation,
The time adjustment unit adjusts the time based on the phase shift amount set in the first region when the current value is smaller than the predetermined value according to the current value determined by the current value determination unit. A power measurement device that performs time adjustment based on the phase shift amount set in the second region when the current value is equal to or greater than the predetermined value. A voltage conversion unit that converts a voltage signal output from a voltage detection circuit that detects a voltage of a circuit to be measured into a first digital value;
A current conversion unit that converts a current signal output from a current detection circuit provided with a current detection unit that detects a current of a circuit to be measured into a second digital value;
A multiplication unit that multiplies the first digital value converted by the voltage conversion unit and the second digital value converted by the current conversion unit, and the power value in the measurement target circuit from the multiplication result by the multiplication unit A power measuring device for obtaining
A phase shift amount setting unit for setting a phase shift amount related to a phase shift between the voltage signal output from the voltage detection circuit and the current signal output from the current detection circuit;
Based on the set phase shift amount, a first timing for performing digital conversion of the voltage signal in the voltage conversion unit and a second timing for performing digital conversion of the current signal in the current conversion unit. A time adjustment unit that adjusts the time by shifting at least one of them;
And a current value determination unit determines a current value detected by the current detection circuit,
The phase shift amount setting unit sets a phase shift amount according to the type of the current detection unit, sets the phase shift amount by a predetermined function corresponding to the current value,
The time adjustment unit is a power measurement device that performs time adjustment based on a phase shift amount corresponding to the current value according to the current value determined by the current value determination unit.

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