JP3544466B2 - Bidirectional energy meter - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a bidirectional watt-hour meter capable of coping with the supply and demand in both the forward and reverse directions. In the bidirectional watt-hour meter, the measurement of the active power and the measurement of the reactive power are performed. A possible bidirectional power metering device .
[0002]
[Prior art]
2. Description of the Related Art In recent years, a power supply / demand mode in which a power consumer having private power generation equipment among power consumers sells surplus power to a power company has begun to be implemented. Conventionally, in a bidirectional watt-hour meter used for buying and selling power, the received and transmitted power of the active power, and the received and transmitted power of the reactive power have been measured and used as a basis for transactions. However, the quality (power factor) of the trading power must be added to the transaction price. Reactive power related to the power factor of power has a lead and a lag, and a conventional bidirectional watt-hour meter uses a power flow relay and multiple watt-hour meters to separately measure the lead and lag of the reactive power. The combination was realized.
[0003]
In addition, in the conventional configuration, the leading and lagging parts of the reactive power could be measured, but in order to further separate and measure this reactive power into the receiving part and the transmitting part, it is necessary to prevent positive and negative reverse rotation. Required a reactive watt-hour meter.
[0004]
[Problems to be solved by the invention]
As described above, conventionally, to measure the active component of the trading power, the power component, the power component, the power component of the delayed reactive power, the power component, the power component of the advanced reactive power, and the power component, A combination of multiple watt-hour meters was required. SUMMARY OF THE INVENTION It is an object of the present invention to provide a weighing device capable of separately measuring each of the above-described electric power amounts with one bidirectional watt-hour meter.
[0005]
[Means for Solving the Problems]
The bidirectional power metering device according to the present invention is configured such that when the received power component is set to the positive direction (positive) and the transmitted component is set to the reverse direction (reverse) according to the power supply direction on the power supply line, the active power amount in each of the forward and reverse directions. And a reactive power / frequency converter that outputs a pulse proportional to the reactive power, and a reactive power that outputs a pulse proportional to the amount of reactive power of each of the leading and lagging phases using a voltage obtained by shifting the voltage of the power supply line by 90 °. Output from the reactive power / frequency converter based on a combination of a positive / negative active power from the active power / frequency converter and a reactive power from the reactive power / frequency converter. Means for determining whether the current direction is forward direction / advance, forward direction / lag, reverse direction / advance, reverse direction / lag, and the output of the control means makes the output of the reactive power / frequency converter positive. Direction / forward, positive direction Switching means for switching between lag, reverse / advance, and reverse / lag; weighing display means for weighing and displaying the separated reactive power; and pulses output from the active power / frequency converter Pulse interval monitoring means for monitoring the intervals of the signals, and the control means reserves the switching of the switching means in accordance with a signal from the pulse interval monitoring means irrespective of the judgment of the reactive power / frequency converter output by the control means. It is like that .
[0006]
Further, when the received power component is set to the forward direction (positive) and the transmitted power component is set to the reverse direction (reverse) according to the power supply direction on the power supply line, active power that outputs a pulse proportional to the active power amount in each of the forward direction and the reverse direction. A frequency converter, a reactive power / frequency converter that outputs a pulse in proportion to the reactive power amount of each of leading and lagging by using a voltage obtained by shifting the voltage of the power supply line by 90 °; The output of the reactive power / frequency converter is forward / advanced and forward / lagged based on a combination of the positive / negative of the active power from the frequency converter and the advance / delay of the reactive power from the reactive power / frequency converter. Control means for determining whether the signal is in the reverse direction, advance, reverse direction or delay, and the output of the control means causes the output of the reactive power / frequency converter to go forward, advance, forward direction, delay, reverse Direction / forward, reverse / late The first pulse interval monitoring means for monitoring the switching means for switching to separation, metering display means for displaying fractionated reactive power were weighed respectively, a pulse interval that is output from the active power / frequency converter And second pulse interval monitoring means for monitoring a pulse interval output from the reactive power / frequency converter, wherein the control means determines the pulse interval time Tw from the active power / frequency converter and the reactive time. A ratio (Tw / Tv) to the pulse interval time Tv from the power / frequency converter is determined, and when the value of the ratio (Tw / Tv) deviates from a predetermined value, the switching of the switching means is reserved. It is.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiment 1 FIG.
FIG. 1 is a block diagram showing the internal configuration of a bidirectional power meter according to the first embodiment of the present invention, which can support both forward and reverse supply and demand modes. In the figure, reference numeral 100 denotes a bidirectional power meter. 1 is a voltage input terminal, 2 is a current input terminal, 3 is a voltage analog / digital converter (V / A / D converter) that converts a voltage reduced to a measurement level by a transformer into a digital value, and 4 is a transformer Is a current analog / digital converter (IA / D converter) for converting a current reduced to a measurement level into a digital value, and 5 is an active power multiplier (W multiplier). The current is multiplied to obtain the power. Reference numeral 6 denotes an active power / frequency converter (W / F converter) that outputs a pulse having a frequency proportional to the active power, and determines whether the power direction is positive or reverse based on the positive or negative sign of the multiplication result of the W multiplier 5. And output them separately. Reference numeral 7 denotes a 90 ° phase shift circuit that delays the phase by 90 ° with respect to the input voltage, 8 denotes a reactive power multiplier (Var multiplier) that multiplies the 90 ° phase shifted voltage by a current to obtain reactive power, and 9 denotes a reactive power multiplier. It is a power / frequency converter (Var / F converter), and determines whether the reactive power is advanced or delayed based on the positive or negative sign of the multiplication result of the Var multiplier 9 and outputs the results separately.
[0008]
Reference numeral 10 denotes a control circuit, which determines the forward, reverse, advance, and delay of the reactive power based on the state of the forward / backward of the active power, the advance of the reactive power, and the delay of the active power as described below. Reference numerals 11 and 12 are changeover switches for selecting a reactive power metering counter in accordance with the judgment result of the control circuit 10. Reference numerals 13 and 14 denote counters that count pulses from the W / F converter 6 and count up the W (positive) weighing display 19 and the W (reverse) weighing display 20 for each predetermined number. The weighing display 19 displays the active power in the forward direction, and the weighing display 20 displays the active power in the reverse direction. 15 to 18 count the pulses from the Var / F converter 9 and count up the weighing indicators 21 to 24 for each predetermined number. The weighing indicator 21 indicates the forward / leading reactive power, the weighing indicator 22 indicates the backward / leading reactive power, the weighing indicator 23 indicates the forward / lagging reactive power, and the weighing indicator 24 indicates the reactive power. The reverse and delay reactive powers are displayed. Reference numeral 25 denotes a pulse output terminal for a measurement test of the bidirectional electric energy meter 100.
[0009]
Next, a method of determining whether the reactive power is normal or reverse in the control circuit 10 will be described with reference to FIGS. FIG. 2 shows a state where the phase of the phase quadrant of the outputs of the W / F converter 6 and the Var / F converter 9 is used to determine whether the reactive power is normal or reverse. When each output is in the shaded phase, a pulse having a frequency proportional to the power amount is output. It is possible to determine whether the reactive power is normal or reverse based on the overlapping combination of the active power output phase (forward and reverse) and the reactive power output phase (lead and lag).
[0010]
FIG. 3 shows a truth table of the above determination. Positive or negative of the reactive power is determined by a logic circuit determining the combination of each of the positive and negative of the active power, the advance of the reactive power, and the output of the reactive power, or by storing the above truth table in a memory and comparing the truth table. Then, the changeover switches 11 and 12 are controlled to the respective counters for measuring the advance and the delay, and the measurement indicators 21 to 24 corresponding to the reactive power are counted up.
[0011]
As described above, the control circuit 10 determines the positive direction and the reverse direction of the reactive power from the combination of the phase quadrants of the outputs of the W / F converter 6 and the Var / F converter 9, and determines the positive / leading reactive power. The amount, the reactive power amount in the backward direction and the advance, the reactive power amount in the forward direction and the delay, and the reactive power amount in the reverse direction and the delay can be measured and displayed on the displays 21 to 24, respectively.
[0012]
Embodiment 2 FIG.
Next, before describing the configuration and operation of the second embodiment, a measurement test of the bidirectional power amount measurement device will be described. FIG. 4 is an arrangement diagram of a device for performing a measurement test on the bidirectional power amount measuring device having the configuration of the first embodiment of the present invention. In the figure, 1, 2, 25, and 100 are the same as those described in the first embodiment. Reference numeral 30 denotes a measurement test power supply device which can arbitrarily set a voltage, a current, and a phase thereof and output the voltage. Reference numeral 40 denotes a reference meter, which uses a highly accurate electronic power meter (active power meter). Reference numeral 50 denotes a QT transformer, which outputs a voltage obtained by delaying the input voltage by 90 °. Reference numeral 60 denotes a switch for switching the input voltage to the reference meter 40 to the output side of the measurement test power supply device 30 or the output side of the QT transformer 50. Reference numeral 70 denotes a rotary counter, which outputs an output pulse from the reference meter 40. The difference between the output pulse from the bidirectional power metering device 100 and the output pulse is measured.
[0013]
With such a measuring test device, the measured value (the number of pulses) of the reference meter 40 and the measured value (the number of pulses) of the bidirectional electric energy meter 100 are compared by the rotary counter 70, and the inside of the bidirectional electric energy meter 100 is compared. Is adjusted so that the metering of the bidirectional energy meter 100 falls within a predetermined error range. At this time, there is no particular problem in the measurement test of the active power W, but in the measurement test of the reactive power Var, the switch 60 that switches the reference meter 40 to measure the reactive power is switched, and the phase of the voltage V is changed by the QT transformer 50. Is delayed by 90 ° and used as a reference meter for reactive power measurement.
[0014]
On the other hand, in the bidirectional electric energy meter 100, the phase of the input voltage is delayed by 90 ° by the 90 ° phase shift circuit 7 for measuring the reactive power. However, this lag is adjusted to 90 ° by the adjusting element, but with a slight error rather than a perfect 90 °. Therefore, as shown in the vector diagram of FIG. 5, at the point where the power supply changes from the forward direction to the reverse direction, that is, near the zero point of the power factor, the 90 ° phase shift circuit 7 sets the reference voltage based on the delayed voltage VR and the QT transformer In the state where the current I exists in the phase between the delayed reference voltage VQ input to the meter 40, the reference meter 40 measures the reactive power in the positive direction and the delay. A state occurs in which the reactive power in the reverse direction and in the forward direction is measured.
[0015]
The pulse output from the bidirectional power metering device 100 to the rotary counter 70 is configured such that the connection is individually switched after the reactive power is positive, reverse, advanced, or delayed. When the current I exists in a phase between the reference voltage VQ and the reference voltage VQ, the weighing pulse from the reference meter 40 is input to the rotary counter 70, but no weighing pulse is input from the bidirectional power metering device 100. For this reason, the measurement test is performed at the point where the power supply changes from the forward direction to the reverse direction and vice versa, that is, at the point where the power supply changes from the reverse direction to the positive direction, that is, near the zero power factor point. Impossible.
[0016]
The two-way power metering device according to the second embodiment allows the metering test to be performed continuously near the zero power factor. FIG. 6 is a block diagram showing the internal configuration of the bidirectional power measurement device according to Embodiment 2 of the present invention. In the figure, 1 to 25 and 100 are the same as those described in the first embodiment. Reference numeral 26 denotes a pulse interval monitoring circuit which monitors a pulse interval (time) of a pulse train proportional to the amount of power output from the W / F converter 6 and sends a signal to the control circuit 10 when the pulse interval is longer than a predetermined time. Output.
[0017]
FIG. 7 is a vector diagram illustrating the operation of the second embodiment, and FIG. 8 is a diagram illustrating output pulses of the W / F converter. In FIG. 7, since the W / F converter 6 outputs a pulse number proportional to the active power, the active power measurement is performed when the current phase moves from the second quadrant to the third quadrant such as I1 → I2 → I0. The value decreases, and the output pulse interval of the W / F converter 6 increases from T1 (a) for the active power W1 shown in FIG. 8 to T2 (b) for the active power W2. If the current exceeds the phase of the retardation voltage VR, the above-described measurement test will fail. Therefore, the output pulse interval is determined by the pulse of the active power W0 of the W / F converter 6 at the phase point immediately before the current overtakes the retardation voltage VR. When the interval is longer than the interval T0 (state B), the control circuit 10 receives the signal from the pulse interval monitoring circuit 26, suspends the switching of the changeover switches 11 and 12, and maintains (holds) the reactive power measurement state currently being measured. I do. When the current moves to the third quadrant and becomes shorter than the pulse interval T0 of the reverse active power W0 (state A), the output signal of the pulse interval monitoring circuit 26 stops, and the control circuit 10 releases the hold. Then, the changeover of the changeover switches 11 and 12 is restarted.
[0018]
Although the output pulse interval from the W / F converter 6 depends not only on the phase of the current but also on the absolute value of the current, the pulse interval corresponding to the active power W0 covering the lag error based on the rated current is used. T0 is set appropriately. According to the results of the experiment, there was no practical problem with the pulse interval T0 corresponding to a phase angle of 3 ° as a standard for setting.
[0019]
In the above description, when the current phase shifts from the second quadrant to the third quadrant, on the contrary, when the current phase shifts from the third quadrant to the second quadrant, the fourth quadrant changes to the first quadrant, and the first quadrant shifts to the first quadrant. Similarly, when shifting to the fourth quadrant, when the interval between the output pulses from the W / F converter 6 is longer than T0, the switching of the changeover switches 11 and 12 is reserved, and when the pulse interval is shorter than T0, the changeover switches 11 and 12 are set. To switch freely.
[0020]
As described above, the pulse interval of the active power is monitored, and when the pulse interval becomes equal to or longer than the predetermined time T0, the switching of the separate measurement of the reactive power is reserved. Therefore, even if the current phase falls within the phase error of the lagging voltage, the power The active power measurement test of the measuring device can be continuously performed.
[0021]
Embodiment 3 FIG.
FIG. 9 is a block diagram showing the internal configuration of the bidirectional energy meter according to Embodiment 3 of the present invention. In the figure, 1 to 26 and 100 are the same as those described in the first embodiment. A pulse interval monitoring circuit 27 monitors the pulse interval (time) of a pulse train proportional to the amount of reactive power output from the Var / F converter 9 and sends a signal to the control circuit 10 when the pulse interval is longer than a predetermined time. Is output. Reference numeral 10a denotes a pulse interval comparing means which compares the pulse interval Tw of the active power with the pulse interval Tv of the reactive power and reserves the switching of the selector switches 11 and 12 by the output from the control circuit 10 when the ratio is a predetermined value or more. Then, the reactive power measurement state currently being measured is maintained (held). When the ratio of Tw and Tv becomes equal to or less than a predetermined value, the hold is released and the changeover of the changeover switches 11 and 12 is restarted.
[0022]
In Embodiment 2 described above, the reservation of the switching of the changeover switches 11 and 12 is determined only by the pulse interval T0 of the active power. Therefore, when the absolute value of the current is small, the current phase is shifted from the second quadrant to the second quadrant. After shifting to the third quadrant, the reference meter 40 is out of the phase error of the lagging voltage, and the reference meter 40 is in the backward / leading reactive power measurement area. The problem is that the power is measured. The third embodiment is an improvement on this point.
[0023]
The operation of the third embodiment will be described with reference to the vector diagram of FIG. When the current phase shifts from the second quadrant to the third quadrant, the phase angle θ immediately before the current overtakes the delayed voltage VR can be obtained from the active power Pw and the reactive power Pva at that time. That is, Sin θ = Pw / Pva. Since the W / F converter 6 outputs a number of pulses proportional to the active power amount, the active power Pw and the active power pulse interval time Tw have a relationship of Tw = 1 / Pw, and similarly, the reactive power Pva and the reactive power Pva The relationship of the power pulse interval time Tv is also Tv = 1 / Pva, and Sin θ = Tv / Tw.
[0024]
Therefore, the ratio (Tw / Tv) of the active power pulse interval time Tw and the reactive power pulse interval time Tv is monitored, and when the ratio (Tw / Tv) exceeds a predetermined value, the changeover switches 11 and 12 are switched. When the ratio (Tw / Tv) is equal to or less than a predetermined value, the control circuit 10 is operated so that the changeover switches 11 and 12 can be switched. The ratio is set to (Tv / Tw) and the switching of the changeover switches 11 and 12 is reserved below a predetermined value, and when the (Tv / Tw) exceeds the predetermined value, the changeover of the changeover switches 11 and 12 is enabled. Is also good.
[0025]
By doing so, when the phase of the current shifts to the third quadrant, the switching of the measurement state of the reactive power is performed at a constant phase angle even if the absolute value of the current changes. , The accuracy of the measurement of the reactive power can be improved.
[0026]
【The invention's effect】
As described above, according to the present invention, from the combination of the phase quadrants of the outputs of the W / F converter and the Var / F converter, the forward / leading reactive power, the backward / leading reactive power, The direction and delay reactive power and the reverse and delay reactive power can be measured and displayed by one bidirectional watt-hour meter.
[0027]
In addition, since the pulse interval of the active power is monitored and the switching of the measurement state of the reactive power is reserved according to the pulse interval, even if the current phase falls within the phase error of the delayed voltage, the active power meter of the power metering device is measured. The test can be performed continuously.
[0028]
In addition, when the phase of the current shifts to the third quadrant, even if the absolute value of the current changes, the measurement state of the reactive power is switched at a constant phase angle, and the reactive power of each measurement state is changed. The weighing accuracy can be improved.
[Brief description of the drawings]
FIG. 1 is a block diagram showing the internal configuration of a bidirectional energy meter according to Embodiment 1 of the present invention.
FIG. 2 is a diagram for describing determination of positive and reverse of the reactive power from the forward and backward of the reactive power according to the first embodiment;
FIG. 3 is a diagram showing a truth table for determining whether the active power is positive or negative, and whether the reactive power is advanced or delayed, and whether the reactive power is positive or reverse based on the delay;
FIG. 4 is a layout diagram of a measurement test of the bidirectional electric energy meter.
FIG. 5 is a vector diagram illustrating reactive power measurement.
FIG. 6 is a block diagram showing an internal configuration of a bidirectional energy meter according to Embodiment 2 of the present invention;
FIG. 7 is a vector diagram illustrating an operation of the second embodiment.
FIG. 8 is a diagram illustrating a pulse state of the W / F converter according to the second embodiment.
FIG. 9 is a block diagram showing the internal configuration of a bidirectional power amount measuring device according to Embodiment 3 of the present invention.
FIG. 10 is a vector diagram illustrating an operation of the third embodiment.
[Explanation of symbols]
1 voltage input terminal, 2 current input terminal, 3 voltage analog / digital converter, 4 current analog / digital converter, 5 active power multiplier, 6 active power / frequency converter, 7 90 ° phase shift circuit, 8 reactive power Multiplier, 9 Reactive power / frequency converter, 10 Control circuit, 11, 12 Changeover switch, 13 to 18 counter, 19, 20 Active power meter display, 21 to 24 Reactive power meter display, 25 Pulse output for weighing test Terminals, 26, 27 Pulse interval monitoring circuit, 100 bidirectional power meter.

Claims (2)

Active power / frequency conversion that outputs a pulse proportional to the active power in each of the forward and reverse directions when the received power component is in the forward direction (positive) and the transmitted component is in the reverse direction (reverse), depending on the power supply direction on the feeder line. Power / frequency converter for outputting a pulse in proportion to the amount of reactive power of each of leading and lagging by using a voltage obtained by shifting the voltage of the power supply line by 90 °, and the active power / frequency conversion The output of the reactive power / frequency converter is forward / leading, forward / lag / reverse from the combination of the forward / reverse of the active power from the converter and the advance / lag of the reactive power from the reactive power / frequency converter. Control means for determining whether the current direction is forward / backward, reverse direction / lag, and the output of this control means causes the output of the reactive power / frequency converter to go forward / forward; forward / lag; Advance, reverse direction and delay Switching means for switching the active power / frequency converter, and a pulse interval monitoring means for monitoring an interval between pulses output from the active power / frequency converter. The bi-directional power metering device according to claim 1, wherein the control means reserves the switching of the switching means irrespective of the determination of the reactive power / frequency converter output by the control means, based on a signal from the pulse interval monitoring means. apparatus. Active power / frequency conversion that outputs a pulse proportional to the active power in each of the forward and reverse directions when the received power component is in the forward direction (positive) and the transmitted component is in the reverse direction (reverse), depending on the power supply direction on the feeder line. Power / frequency converter for outputting a pulse in proportion to the amount of reactive power of each of leading and lagging by using a voltage obtained by shifting the voltage of the power supply line by 90 °, and the active power / frequency conversion The output of the reactive power / frequency converter is forward / leading, forward / lag / reverse from the combination of the forward / reverse of the active power from the converter and the advance / lag of the reactive power from the reactive power / frequency converter. Control means for determining whether the current direction is forward / backward, reverse direction / lag, and the output of this control means causes the output of the reactive power / frequency converter to go forward / forward; forward / lag; Advance, reverse direction and delay And switching means for switching to a metering display means for displaying fractionated reactive power were each weighed, and the first pulse interval monitoring means for monitoring the pulse interval output from the active power / frequency converter, Second pulse interval monitoring means for monitoring a pulse interval outputted from the reactive power / frequency converter, wherein the control means includes a pulse interval time Tw from the active power / frequency converter and a reactive power / A ratio (Tw / Tv) to the pulse interval time Tv from the frequency converter is obtained, and when the value of the ratio (Tw / Tv) deviates from a predetermined value, the switching of the switching means is reserved. And a two-way power meter.

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