JPS6314304B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronic watt-hour meter, and particularly to a watt-hour meter that uses one code converter, such as an A-D converter, in a time-sharing manner to obtain integrated electric energy. Regarding improvements.

FIG. 1 is a basic configuration diagram of an electronic watt-hour meter.

In the figure, ev is a voltage signal proportional to the load voltage of the power system, and ei is a voltage signal proportional to the consumed current. Both signals ev and ei are analog switches selectively switched by sequence logic 1.
It is supplied to the A-D converter 2 through Sa.
This analog switch Sa is usually composed of a semiconductor switch such as an FET, while the A-D converter 2
The signal is converted into a pulse number proportional to the signal ev or ei using an integral type A-D converter or the like.
The sequence logic 1 is also used to start AD conversion in the AD converter 2 and to control switching of logic switches Sb (for example, AND gates) on the succeeding side of the AD converter 2. In other words, both switches Sa and Sb are controlled in conjunction by sequence logic 1 so that when switch Sa is on the v side, switch Sb is also switched to the v side, and when switch Sa is on the i side, switch Sb is also switched to the i side. It's getting old.

Therefore, when both switches Sa and Sb are connected to the v side, the voltage signal ev is converted into a number of pulses by the A-D converter 2, and the number of pulses is counted by the counter 3 on the succeeding side of the logic switch Sb. Ru.
That is, the counter 3 counts the number of pulses Nv proportional to the voltage signal ev for each AD conversion.

On the other hand, when both switches Sa and Sb are connected to the i side, the voltage signal ei is converted into a pulse number by the A-D converter 2, and the pulse number is supplied to the rate multiplier 4 on the subsequent side of the logic switch Sb. Ru. Then, the output of the rate multiplier 4 is input to a subsequent counter 5 for cumulative counting to obtain the amount of power.

In this way, the electricity meter shown in Figure 1 has a simple configuration and can accurately count the number of pulses, but because it uses one A-D converter 2 in a time-division manner, it is capable of relatively high-speed operation. Even when using the A-D converter 2, when measuring AC power (usually 50>60Hz), the time when the voltage signal v is multiplied by the current signal i is A-
A sampling shift occurs due to the conversion time of the D converter 2, and this is a cause of error.

To explain this sampling deviation using Fig. 2, the voltage signal ev proportional to the load voltage is
When converting, an A-D conversion time ts is required, and after this A-D conversion, a voltage signal proportional to the current consumption is generated.
Since ei is A-D converted, a phase shift, that is, a sampling shift occurs between v and i by this A-D conversion time. Such sampling deviation is a problem that will inevitably occur as long as time-division processing is performed even if a high-speed A-D converter is used.

By the way, the above-mentioned disadvantages can be eliminated by adding a few circuits. For example, the phase of the voltage signal ei may be delayed by the A/D conversion time ts (see FIG. 3). As a means of delaying this phase, a capacitor is inserted in parallel into the circuit, but this is not very practical as it leaves problems with phase adjustment.

The present invention has been made in view of the above-mentioned circumstances, and has a simple and inexpensive configuration without using an analog multiplication function, and can eliminate sampling deviation during time division processing without performing phase adjustment. The company provides electricity meters.

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 4, ev and ei are a voltage signal proportional to the load voltage of the power system and a voltage signal proportional to the consumed current, as described above, and these are supplied to input terminals 11 and 12, respectively. This input terminal 11 is connected to one end of the capacitor CHv via a charging control switch sv, and is connected to one end of the capacitor CHv.
The other end of CHv is grounded. Input terminal 12
Similarly, the capacitor CHi is connected to one end of the capacitor CHi via the charging control switch Si, and the other end of the capacitor CHi is grounded. Both these switches Sv,
Si is controlled on and off simultaneously by the sequence logic 13. In addition, the common part between switch Sv and capacitor CHv, and the common part between switch Si and capacitor Siv are respectively signal selection switches.
It is connected to the A-D converter 14 via Sva and Sia. Both of these switches Sva and Sia are A
- During the D conversion, the sequence logic 13 alternately selects and closes the switch Sva or
The signal charged in the capacitor CHv or CHi on the side corresponding to Sia is supplied to the A-D converter 14. Sb is a logic switch, 15 is a counter, 16 is a rate multiplier, and 17 is an integration counter, which have the same configuration as in FIG. Further, R is a reset signal.

Next, the operation of the electricity meter configured as above will be explained. First, a signal is output from the sequence logic 13 to simultaneously close the charging control switches Sv and Si at time _t1 as shown in FIG. 5a and b, and the signal ev supplied to the input terminals 11 and 12 is , ei are sampled and charged to capacitors CHv and CHi.
Therefore, as shown in FIG. 6, the signals ev,
The instantaneous value of ei is stored in capacitors CHv and CHi and held during the A-D conversion period of the A-D converter 14. On the other hand, the signal selection switches Sva and Sia are alternately selected and closed by the sequence logic 13 during the period _T0 . At this time, the logic switch Sb is connected to the v side when the switch Sva is closed, and to the i side when the switch Sia is closed.

Therefore, when the switch Sva is closed, the capacitor
The signal ev charged in CHv is the A-D converter 1
4 (see Figure 5e),
It is counted by the counter 15 via the logic switch Sb. Nv(t ₁ ) in f in the same figure means the counted value of the number of pulses for the voltage signal ev at time t ₁ .
The contents counted by the counter 15 are input and set in parallel to the rate multiplier.

On the other hand, in the latter period T ₀ /2, the signal selection switch Sia is closed, and as a result, the signal ei proportional to the current charged in the capacitor CHi is applied to the switch Sia.
is supplied to the A-D converter 14, where it is converted into a pulse number (see Ni(t ₁ ) in FIG. 5e). This Ni(t ₁ ) is the number of pulses for the voltage signal ei at time t ₁ and is sent in series to the rate multiplier 16 through the logic switch Sb closed on the i side. Then, this rate multiplier 16 outputs the multiplied value of the instantaneous voltage and current values Nv (t ₁ ) and Ni (t ₁ ) at each time t ₁ (t ₂ , t ₃ , ...) (Fig. 5 (see h). Letting this multiplication value be W(t ₁ ), it can be expressed as W(t ₁ )=Nv(t ₁ )·Ni(t ₁ )/K. However, K is counter 15
is the full-scale value of The value thus obtained by the rate multiplier 16 is integrated by the subsequent counter 17 to obtain the so-called power amount at time _t1 . Signals ev and ei at times t ₂ , . . . are also processed in the same order.

Note that the present invention is not limited to the above-mentioned embodiments, and various modifications can be made. For example, in the above embodiment, a single-phase watt-hour meter has been described, but it can also be applied to other multi-phase watt-hour meters based on time-sharing processing.

As described in detail above, according to the electricity meter of the present invention, most of the signals are digitally processed, the entire circuit configuration can be easily realized, and the multiplication part does not have an analog configuration. Therefore, it is possible to realize an extremely high-precision watt-hour meter that does not produce analog errors at all.

In addition, a voltage signal is sent to the first counter 15 and a current signal is sent to the rate multiplexer 16.
By using the output of the first counter 15, which is input via Sb and changes according to the voltage signal, as the input setting of the rate multiplexer 16, the product of the voltage signal and the current signal is obtained at the output of the rate multiplexer 16. Can be done. Therefore, since the input settings of the rate multiplexer conventionally used as a frequency divider circuit are varied by a voltage signal, a digital multiplication circuit for measuring instantaneous power values can be obtained with a reduced number of circuit components. This makes it possible to obtain a circuit that is more resistant to noise than analog configurations.

Further, according to the present invention, A
- Multiple signals at the same time on the input side of the D converter
A circuit that stores ev and ei and a signal selection switch that alternately supplies the stored contents to the A-D converter every certain period are provided, so it is possible to accurately measure the instantaneous value of electric energy at the same time. can. Moreover, using the signals ev and ei at the same time, A-D is applied alternately.
Since conversion is performed, there is no need for phase adjustment, etc., which not only makes it possible to eliminate errors due to phase shifts, but also allows implementation without using a high-speed AD converter.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing the basic configuration of an electronic watt-hour meter, and Figure 2 is an A-D diagram of the watt-hour meter shown in Figure 1.
FIG. 3 is a diagram illustrating the correction of the phase shift accompanying A-D conversion. FIG. 4 is a configuration diagram illustrating an embodiment of the watt-hour meter according to the present invention. , FIG. 5 is a timing chart explaining the operation of the watt-hour meter shown in FIG. 4, and FIG. 6 shows the signals ev,
FIG. 3 is a diagram showing a sampling state of ei. Sv, Si...Charging control switch, CHv, CHi
... Capacitor, Sva, Sia ... Signal selection switch, Sb ... Logic switch, 13 ... Sequence logic, 14 ... A-D converter, 1
5, 17...Counter, 16...Rate multiplier.

Claims (1)

[Claims] 1 In a watt-hour meter that obtains the amount of electricity by converting the signal ev proportional to the load voltage and the signal ei proportional to the consumed current into the number of pulses and then performing arithmetic processing, the signal ev proportional to the load voltage and the signal ei proportional to the consumed current are a plurality of sampling circuits that sample and store the proportional signal ei at the same time every unit time; a first switch that alternately scans both the signals ev and ei stored in these circuits in a time-sharing manner; These signals ev,
An A-D converter that alternately converts ei into a number of pulses, and an A-D converted pulse number of the signal ev,
A second switch that is switched in conjunction with the first switch.
a first counter that counts through a switch;
The number of A-D converted pulses of the signal ev is set in parallel, and when the number of A-D converted pulses of the signal ei is introduced through the second switch, the number of instantaneously multiplied pulses is output. 1. A power meter comprising: a rate multiplier; and a second counter, which counts and integrates output pulses of the rate multiplier.