JP5450500B2 - Oscillator for AC meter test power supply - Google Patents

Description

  The present invention relates to an oscillation device for an AC meter test power source, and more particularly to an oscillation device used as a power source for testing a watt-hour meter.

  For example, a watt-hour meter is obliged to undergo a verification when it is used for a predetermined period, and a predetermined verification is made. Since the number of watt-hour meters to be verified is enormous, it is customary to verify a certain number together, and the verification is performed by an imaginary load test.

  As shown in FIG. 4, the current coil Ci and the voltage coil Cv of the watt hour meter are separated, the current coil Ci is connected in series, energized from the current source of the imaginary load power source, and connected in parallel. The test is performed by applying a voltage from a voltage source to the voltage coil Cv. FIG. 4A is a connection diagram in the case where there is one watt-hour meter, and FIG.

  In order to perform this test, it is necessary to disconnect the current coil Ci connected to the voltage coil Cv in the watt hour meter from the voltage coil Cv, and to connect the current coils Ci directly before energization.

  FIG. 5 is a block diagram showing a configuration of a conventional imaginary load power supply apparatus. The voltage signal v is supplied from the oscillator 12 combined with the arithmetic unit 11 to the voltage amplifier 13 and the current signal i is supplied to the voltage-current conversion amplifier 14, and the outputs of both amplifiers 13 and 14 are supplied to the watt-hour meter X to measure the voltage. A value V and a current measurement value I are obtained. The voltage V and current I are supplied to the wattmeter 16 to extract the power value, and the feedback is returned to the arithmetic unit 11 to control the oscillator 12.

  At this time, the wattmeter 16 integrates and averages the given voltage measurement value V and current measurement value I, and gives the obtained value to the arithmetic unit 11 as a feedback signal. For this reason, the control operation is performed with a certain delay.

Japanese Patent Laid-Open No. 10-285982 JP 2000-278987 A

  As described above, the imaginary load power supply device 10 constitutes a voltage source and a current source that amplify and output the signal of the oscillator 12 by the voltage amplifier 13 and the voltage-current conversion amplifier 14. For this output, the effective value and phase angle are detected by a detector, and the setting accuracy is compensated by feedback control of the amplitude and phase angle of the oscillator 12 to the oscillator 12 via the arithmetic unit 11.

  In order to reliably perform this compensation, it is necessary to use an expensive voltmeter, ammeter, and wattmeter as a detector, which causes a cost problem. Further, the feedback control has an insufficient response speed to compensate for the waveform distortion, and as a result, a waveform with much distortion is output.

  The present invention has been made in consideration of the above-described points, and an object thereof is to provide an oscillation device for a wattmeter test power supply capable of supplying an output with a waveform distortion reduced as much as possible.

In order to achieve the above object, in the present invention,
A reference waveform memory storing amplitude information of the reference waveform;
Waveform detection means for extracting amplitude information for each predetermined electrical angle of the target waveform from the meter to be tested;
A subtractor for detecting a difference signal by comparing the target waveform information extracted from the waveform detection means with the reference waveform information;
A correction waveform memory for storing correction information for correcting the reference waveform information by a difference signal from the subtractor;
An adder that corrects the reference waveform information from the reference waveform memory with the correction information from the correction waveform memory to form output information;
An oscillator for an AC meter test power supply, characterized by forming an output based on the output information,
I will provide a.

  As described above, since the present invention compensates for the difference obtained by extracting the amplitude information for each predetermined electrical angle of the target waveform from the target meter and comparing it with the reference waveform information when the meter is verified, an output is formed. A so-called instantaneously corrected waveform output can be formed.

Explanatory drawing which shows the basic composition of one Example of this invention. The block diagram which shows the component of the Example shown in FIG. 3A and 3B are block diagrams showing two embodiments of the present invention. The block diagram which shows the structure of the conventional imaginary load power supply device. FIGS. 5A and 5B are connection diagrams showing the configuration of an imaginary load power supply device used when validating an AC watt-hour meter.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 shows the basic concept of the present invention. That is, the voltage V and current I applied to the watt-hour meter X to be measured are fed back to the oscillator 100 without passing through some element accompanied by a delayed operation, and the output v of the oscillator 100 is sent to the voltage amplifier 200 and i The voltage / current conversion amplifier 300 is supplied to the watt-hour meter X.

  Therefore, the oscillator 100 receives the voltage V and the current I without delay, forms the outputs v and i, and supplies them to the voltage amplifier 200 and the voltage / current conversion amplifier 300.

  FIG. 2 is an explanatory diagram depicting element groups actually used and lines connecting them in order to show elements constituting the test power source shown in FIG. This apparatus includes an oscillator 100 as a PLD 102 with a waveform memory combined with a switch 101, D / A converters 201 and 301, A / D converters 202 and 302, and clock generation for supplying a sampling clock signal to each part of the apparatus. It is constituted by a device CLK.

  The switch 101 selects the output frequency formed by the oscillator 100 and selects, for example, 50 Hz or 60 Hz. The PLD 102 with a waveform memory forms a sine wave signal of one frequency selected by the switch 101, for example, 50 Hz, and supplies the voltage Vout and current Iout to the watthour meter X via the D / A converters 201 and 301. give.

  The voltage Vin and the current Iin taken out by the watt-hour meter X for each predetermined electrical angle are fed back to the PLD 102 with waveform memory via the A / D converters 202 and 302 and used for waveform control of the sine wave.

  Here, it is desirable to remove unnecessary higher harmonics included in the inputs Vin and Iin from the power meter X to the A / D converters 202 and 302 as distortion components. For this purpose, a high-order harmonic that is a distortion component is included in the input Vin, and this input Vin is given to the PLD 102 with a waveform memory to make necessary corrections to form a sine wave signal.

  This high-order harmonic is generated by a voltage amplifier (not shown) connected to the output side of the D / A converter 201 and an output transformer and output current transformer provided in the voltage-current conversion amplifier (not shown). In addition, it is caused by the magnetizing characteristics of the transformer built in the wattmeter to be tested, so it is limited to those below the 11th harmonic, and even higher harmonics are negligible. It is only done.

  Therefore, it is preferable to insert a low-pass filter (not shown) that passes signals from the fundamental wave component to the 11th harmonic at the same level at the input parts of the A / D converters 202 and 302. The input Vin includes the sampling clock (several hundreds of kHz) included in the output voltage Vout, which is naturally removed by a low-pass filter.

  FIGS. 3A and 3B show two configuration examples as embodiments of the present invention, both of which use a PLD with a waveform memory, but have different internal connections. The clock circuit shown in FIG. 2 is not shown.

[Configuration of Example 1]
FIG. 3A shows the first embodiment. In this embodiment, the output Vs of the processor CPU built in the PLD 102 is supplied to the reference waveform memory 112, and the output of the reference waveform memory 112 is supplied to the adder 114 and the subtractor 116.

  The subtractor 116 forms a deviation signal to be supplied to the correction waveform memory 113, that is, a deviation Δv (= Vs−Vin) between the reference signal Vs and the feedback signal Vin. The correction waveform memory 113 is based on this deviation Δv. A correction signal ΔVout is formed.

  Then, the reference signal Vs is corrected by the correction signal ΔVout to obtain an output voltage Vout, which is converted into digital data by the controller 115, analog-converted by the D / A converter 201, and output.

  On the other hand, the input voltage Vin is a voltage extracted from a power meter to be tested (not shown). In this input voltage Vin, high-order harmonics (for example, 12th and higher harmonics) are removed by the low-pass filter 202A, and only lower-order (11th and lower) harmonics and fundamental waves are A / D. The signal is supplied to the converter 202, converted into a digital signal, and supplied to the controller 115.

[Configuration of Example 2]
FIG. 3B shows a second embodiment. In this embodiment, the feedback signal output Vin of the controller 125 is given to the CPU 121, and the deviation signal Δv is formed by subtracting the feedback signal Vin from the reference voltage Vs inside the CPU 121, and is given to the correction waveform memory 123. That is, the subtracter 116 in FIG. 3A is incorporated in the CPU 121.

[Operation]
Each of the circuits shown in FIGS. 3A and 3B forms an output whose amplitude is controlled for each predetermined electrical angle determined by the frequency of the sampling clock. That is, the controllers 115 and 125 obtain the amplitude data (DATA) from the A / D converter 202 every predetermined electrical angle and output the amplitude output Vin that changes every time.

  As a result, the outputs (DATA) of the controllers 115 and 125 change every predetermined electrical angle, and the output Vout of the D / A converter 201 changes every time the predetermined electrical angle.

  As the predetermined electrical angle is selected to be smaller, the controllability at every moment increases and more precise waveform control can be performed. For example, if the predetermined electrical angle is 1 degree, a 1 Hz waveform is time-divided into 360 pieces / second.

  This is rapid response control in which the amplitude is controlled every 1/360 seconds, and an accurate sine wave can be obtained. Therefore, highly accurate waveform control can be realized by setting the electrical angle to a value necessary for realizing the desired waveform.

10 virtual load power supply device, 11 arithmetic device, 12 oscillator, 13 voltage amplifier,
14 voltage-current conversion amplifier, 15 current transformer, 16 wattmeter, 100 oscillator,
101 switcher, 102 PLD, 111, 121 CPU,
112, 122 reference waveform memory, 113, 123 correction waveform memory,
114, 124 adder, 115, 125 controller, 116 subtractor,
200 voltage amplifier, 201, 301 D / A converter,
202, 302 A / D converter, 300 voltage-current conversion amplifier,
CLK Clock generator.

Vs voltage reference waveform, Vin input voltage, Δv deviation, ΔVout output signal,
Vout output voltage.

Claims (3)

A reference waveform memory storing amplitude information of the reference waveform;
Waveform detection means for extracting amplitude information for each predetermined electrical angle of the target waveform from the meter to be tested;
A subtractor for detecting a difference signal by comparing the target waveform information extracted from the waveform detection means with the reference waveform information;
A correction waveform memory for storing correction information for correcting the reference waveform information by a difference signal from the subtractor;
An adder that corrects the reference waveform information from the reference waveform memory with the correction information from the correction waveform memory to form output information;
An oscillation device for an AC meter test power source that forms an output based on the output information. In the oscillation device for an AC meter test power source according to claim 1,
The reference waveform memory, the subtractor, the correction waveform memory, and the adder are configured by a programmable logic device. In the oscillation device for an AC meter test power source according to claim 1,
The signal from the fundamental wave component to the predetermined harmonic is passed to the input side of the waveform detection means.
An oscillation device for an AC meter test power supply characterized by providing a low-pass filter.

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