WO2020022255A1 - Measuring device, and voltage generating method - Google Patents

Abstract

The present invention provides a measuring device capable of generating, from a measured alternating current waveform, an alternating current voltage waveform corresponding to the alternating current waveform. The measuring device includes an oscillator for generating an alternating current voltage signal, and a phase comparator for detecting a phase difference between the waveform of an input alternating current and the waveform of the alternating current voltage signal generated by the oscillator, and is provided with a phase synchronization circuit which varies an oscillation frequency of the oscillator on the basis of the phase difference, and performs control such that the phase difference satisfies a predetermined condition.

Description

Measuring device and voltage generation method

(Description of related application)
The present invention is based on the priority claim of Japanese Patent Application No. 2018-137655 (filed on Jul. 23, 2018), the entire contents of which are incorporated herein by reference. Shall be.
The present invention relates to a measuring device and a voltage generation method.

技術 A technique is used in which the power consumption and current consumption waveforms are monitored by sensors installed on the distribution board, and the power consumption and operating state of each electric device are estimated based on the characteristic amount and the like. In order to compare and analyze the current waveform in a time series, it is necessary to measure the current waveform based on the phase of the voltage. In measuring the current waveform, it is preferable to accurately grasp the phase delay with respect to the voltage waveform. It is known that, when the phase delay with respect to the voltage waveform is inaccurate, the calculation cost for estimating the current waveform increases, and the estimation accuracy also decreases, which makes it impractical.

Therefore, it is desirable to measure current and voltage simultaneously, as shown in FIG. FIG. 14 schematically shows an example of a power measurement system in a three-phase four-wire connection system. A current waveform and a voltage waveform are monitored by an ammeter 101 and a voltmeter 102 installed on a breaker 105 of a distribution board that supplies power to a load 104 such as an electric device. Generally, a non-contact type sensor such as a CT (Current Transformer) is used for the ammeter 101. In the CT, for example, an alternating current (secondary current) according to the turns ratio flows through the secondary winding so as to cancel a magnetic flux generated in the magnetic core due to the alternating current flowing through the conductor (primary side). The voltage (proportional to the current flowing through the conductor) generated across the resistor due to the secondary current is measured. In addition, the ammeter 101 may be connected to the main trunk of the distribution board instead of the branch wiring. FIG. 15 is a diagram showing an example of three-phase four-wire AC current waveforms I1, I2, I3 and voltage waveforms V1, V2, V3 to the load 104 measured by the ammeter 101 and the voltmeter 102 in FIG. is there.

場合 When measuring the line voltage with the voltmeter 102 as in the example of FIG. 14, it is difficult to accurately measure the line voltage without touching the power supply wiring. In addition, installation of the cable for voltage measurement requires construction by an electrician. In addition, there are often no power outlets on distribution boards. In this case, new construction of a power outlet is required.

To solve the problem of installing a voltmeter in a distribution board (requires construction by a qualified person, etc.), a non-contact type voltage / current sensor using stray capacitance generated between the electric wire and the sensor converts the current waveform to a voltage waveform. There is known a method of acquiring in synchronization with the above (Patent Document 1).

According to Patent Document 1, it is possible to measure the current waveform in synchronization with the voltage waveform, but the stray capacitance varies depending on the thickness and material of the electric wire and the mounting method, and the phase delay after the sensor is installed is reduced. Although the value is constant, it is described that the value differs depending on the installation environment. In addition, there is a problem that it is difficult to know only from a non-contact measurement result because a phase delay between a current waveform and a voltage waveform has an environment dependency. To solve this problem, Patent Document 1 discloses a device and a method for estimating a phase delay between a voltage and a current for estimating a phase delay between a voltage waveform and a current waveform using a non-contact type voltage / current sensor. It has been disclosed. In Patent Literature 1, a power factor between a measured current waveform and a voltage waveform having a phase delay is calculated, and a phase delay at which the power factor is maximized is estimated as a true value.

JP 2016-033488 A

よ う As mentioned above, to measure the voltage at the distribution board, construction by a qualified person (electrician) is required. In Patent Document 1, a voltage waveform and a current waveform are measured using a non-contact type voltage sensor and a current sensor, and a phase delay between them is estimated.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an apparatus and a method capable of generating, from a measured AC current waveform, an AC voltage waveform corresponding to the AC current waveform. Is to do.

According to one embodiment of the present invention, an oscillator that generates an AC voltage signal, a phase comparator that detects a phase difference between a waveform of an input AC current and a waveform of the AC voltage signal generated by the oscillator, There is provided a measuring apparatus including a phase locked loop circuit having a variable oscillation frequency of the oscillator based on the phase difference and controlling the phase difference to satisfy a predetermined condition.

According to one embodiment of the present invention, a phase difference between a waveform of an AC current measured by an ammeter and a waveform of an AC voltage signal generated by an oscillator included in a phase locked loop is detected, and based on the phase difference, A voltage generation method is provided in which the oscillation frequency of the oscillator is varied and the phase difference is controlled so as to satisfy a predetermined condition.

According to the present invention, an AC voltage waveform corresponding to the AC current waveform can be generated from the measured AC current waveform.

FIG. 3 is a diagram illustrating an exemplary embodiment of the present invention. FIG. 3 is a diagram illustrating an exemplary embodiment of the present invention. (A), (B) is a figure explaining a phase comparator. FIG. 3 is a diagram illustrating a phase comparator. FIG. 3 is a diagram illustrating a configuration of a phase comparator. FIG. 3 is a diagram illustrating a configuration of a phase comparator. FIG. 3 is a diagram illustrating a configuration of a VCO. FIG. 4 is a diagram illustrating an operation of the first embodiment. FIG. 2 is a diagram illustrating Embodiment 1. FIG. 2 is a diagram illustrating Embodiment 1. FIG. 6 is a diagram illustrating a configuration of a second embodiment. FIG. 6 is a diagram illustrating a configuration of a second embodiment. FIG. 6 is a diagram illustrating a configuration of a second embodiment. It is a figure explaining an example of a power measuring system. FIG. 4 is a diagram illustrating current and voltage waveforms measured by the power measurement system.

An exemplary embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating an embodiment of the present invention. FIG. 1 shows an example of a single-phase two-wire connection simply for simplicity of description. A non-contact type ammeter 101 such as a CT (Current Transformer) detects, for example, an AC current flowing through a power supply line 106 from an AC power supply 103 and supplies the AC current to the measuring device 110 as, for example, a voltage between terminals of a resistor. I do. In FIG. 1, the ammeter 101 detects the current flowing through the power supply line 106 of the breaker 105 of the distribution board in a non-contact manner.

The measuring device 110 detects a phase difference between a voltage waveform corresponding to the AC current waveform measured by the ammeter 101 and an AC voltage waveform generated by the oscillator, and adjusts the phase difference to a predetermined value (for example, zero). The frequency of the AC voltage generated by the oscillator is variably controlled. The measuring device 110 separates an AC current waveform (a voltage waveform corresponding to the AC current waveform) I measured by the ammeter 101 and an AC voltage waveform V synchronized in phase with the AC current waveform measured by the ammeter 101. Output as an AC current waveform and AC voltage waveform in the panel.

Based on the AC voltage waveform V output from the measuring device 110 and the AC current waveform I on the distribution board measured by the ammeter 101, power calculation, power separation technology (disaggregation) and the like for each device may be performed. Good. Note that the ammeter 101 may be connected to the main breaker 105-1 in FIG. According to the present embodiment, an AC voltage waveform corresponding to the measured AC current waveform can be generated without measuring the voltage. In FIG. 1, the breaker 105 of the distribution board may be a branch breaker or a main breaker.

FIG. 2 is a diagram illustrating the configuration of an embodiment of the present invention. The ammeter 101 supplies an alternating current (secondary current) corresponding to the turns ratio to the secondary winding so as to cancel the magnetic flux generated in the magnetic core 1011 due to the alternating current flowing through the power supply line 106 (primary side). Then, a voltage (AC voltage) generated across the resistor RL due to the secondary current is output as the detected AC current. In the measuring device 110, the amplifier 111 amplifies the voltage between terminals (AC voltage) of the resistor RL. A low-pass filter (Low-Pass-Filter: LPF) 112 blocks (attenuates) frequency components of the output voltage of the amplifier 111 that are equal to or higher than a predetermined frequency (cut-off frequency), and passes frequency components equal to or lower than the cut-off frequency.

The Phase Locked Loop (PLL) 120 includes a phase comparator 121, a loop filter (Loop Filter) 122 including a low-pass filter, and a voltage controlled oscillator (Voltage Controlled Oscillator: VCO) 123.

The phase comparator 121 detects the phase difference between the AC voltage signal waveform output from the LPF 112 and the AC voltage signal waveform (sine wave) output from the VCO 123, and outputs a voltage corresponding to the phase difference.

The loop filter 122 smoothes the output voltage from the phase comparator 121. The loop filter 122 supplies the smoothed voltage to the VCO 123 as a control voltage. The VCO 123 varies the oscillation frequency within a predetermined frequency range ± Δf according to the control voltage supplied from the loop filter 122, with the commercial power supply frequency as the center frequency fc. Although not particularly limited, the VCO 123 may include, for example, a sine wave oscillator, and vary the oscillation frequency according to a control voltage from the loop filter 122.

FIG. 3A is a diagram illustrating an example of the configuration of the zero-cross detection circuit 1211 of the AC voltage waveform in the phase comparator 121. FIG. 3B is a diagram illustrating the operation of the zero-crossing detection circuit 1211 in FIG.

In FIG. 3A, when the voltage of the non-inverting input terminal (+) is equal to or lower than the reference voltage (0 V) of the inverting terminal (−), the comparator 1212 outputs (comparisons) as shown in FIG. A low potential is output to Vout, and when the voltage at the non-inverting input terminal (+) exceeds the reference voltage (0), a high potential is output to the output Vout. Then, when the voltage of the non-inverting input terminal (+) becomes equal to or lower than the voltage obtained by dividing the High potential by the resistors R1 and R2, a Low potential is output to the output Vout.

Note that FIG. 3A illustrates an example of the configuration of an analog circuit as the zero-cross detection circuit 1211; however, the zero-cross detection circuit 1211 is not limited to the analog circuit configuration. And the zero cross point may be detected based on the digital signal waveform.

FIG. 4 is a diagram illustrating an example of the configuration of the phase comparator 121 in FIG. The voltage inputs Vin1 and Vin2 of the phase difference detection circuit 1214 are the output voltage of the VCO 123 and the output voltage of the LPF 112 (either may be used). The zero-cross detection circuits 1211A and 1211B detect zero-crosses when the voltage inputs Vin1 and Vin2 input to each change from negative to positive. The digital phase comparison circuit 1213 receives the output signals from the zero cross detection circuits 1211A and 1211B, detects the phase difference between the zero cross points at the voltage inputs Vin1 and Vin2, and when the phase of the voltage input Vin1 lags behind the voltage input Vin2. , UP signal, and if the phase is advanced, a DOWN signal is output.

(4) When the UP signal from the phase difference detection circuit 1214 is activated, the charge pump circuit 1215 turns on the switch SW1 and charges the capacitor C with the discharge current (source @ current) from the constant current source 1. When the DOWN signal from the phase difference detection circuit 1214 is activated, the switch SW2 is turned on, and the capacitor C is discharged by the sink current (sink current) from the constant current source 2. The terminal voltage of the capacitor C is smoothed by the loop filter 122 and supplied to the VCO 123 as a control voltage.

FIG. 5 is a diagram for explaining the operation of the digital phase comparison circuit 1213 in FIG. In FIG. 5, Vout1 and Vout2 are zero-cross detection results (digital signals) of the voltage inputs Vin1 and Vin2. The digital phase comparison circuit 1213 detects rising edges of the zero-cross detection results (digital signals) Vout1 and Vout2 from Low to High. If the rising edge of Vout1 is ahead of Vout2, the rising edge of Vout2 rises at the rising edge of Vout1. An active DOWN signal is output for a time corresponding to the phase difference with respect to the edge. If the rising edge of Vout2 is ahead of Vout1, the UP signal that is active is output for a time corresponding to the phase difference between the rising edge of Vout2 and the rising edge of Vout1.

FIG. 6 is a diagram illustrating an example in which the phase comparator 121 of FIG. 2 is configured by an analog multiplier 1216. By multiplying the sine waves of Vin1 and Vin2 (same frequency: f ₁ ) in FIG.

Becomes

The analog multiplier 1216 is configured by, for example, a Gilbert multiplier. The output signal from the analog multiplier 1216 is input to the loop filter 122 is a low-pass filter cuts off a frequency component of 2 × f _1. As a result, a DC (direct current) component [cos (θ ₁ −θ ₂ )] / 2 (a frequency component equal to or lower than the cutoff frequency) of the output signal from the analog multiplier 1216 is extracted. When the frequencies of the sine waves of Vin1 and Vin2 are different from f ₁ and f ₂ ,

Cuts off the frequency component of (f ₁ + f ₂ ) from

Is output by a low-pass filter (loop filter 122).

FIG. 7 is a diagram schematically illustrating an example of the VCO 123 in FIG. In the example of FIG. 7, the VCO 123 includes a Wien bridge oscillation circuit configured with an operational amplifier (Operational Amplifier) 1231. The oscillation frequency is given below.

For example a resistor R ₂ constituted by CdS (cadmium sulfide) cells, etc., by varying the resistance value of the resistor R ₂ in the light from the photodiode D ₁ which current is varied in a control voltage (output voltage of the LPFs 122), the control voltage May be generated. When the control voltage is increased, the current flowing through the photodiode D ₁ is increased (light emission amount increases), the resistance value of the resistor R ₂ is decreased, the oscillation frequency f is increased. When the control voltage is lowered, the photodiode D ₁ in the flowing current decreases (light emission amount decreases), the resistance R the resistance value of ₂ is increased, the oscillation frequency f is lowered.

The VCO 123 is, of course, not limited to the configuration shown in FIG. For example, the VCO 123 is composed of a ring oscillator that varies the oscillation frequency with the power supply voltage by feeding back the output of the last stage of the odd-numbered inverter to the input of the first stage, and inputs a square wave from the ring oscillator to, for example, a band-pass filter. , And may be converted to a sine wave and output. Alternatively, a signal obtained by dividing the output signal of the VCO 123 by a frequency divider (not shown) may be fed back to the phase comparator 121 and output as an AC voltage V.

FIG. 8 is a diagram illustrating the operation of the first embodiment. A waveform 141 in FIG. 8A is a current waveform (output voltage of the amplifier 111 in FIG. 2) flowing through the power supply line 106 measured by the ammeter 101.

波形 A waveform 142 in FIG. 8B is a voltage waveform obtained by cutting a high frequency of the waveform 141 in FIG. 8A by the LPF 112 in FIG. FIG. 8C is a diagram showing an AC voltage waveform 143 (output voltage waveform V of PLL 120 in FIG. 2) that is phase-synchronized with waveform 142 in FIG. 8B in PLL 120 in FIG.

FIG. 9 is a diagram illustrating an example in which the embodiment of FIG. 2 is applied to a three-phase four-wire power supply. Non-contact type ammeters 101-1 to 101-3 are arranged on power lines L1, L2, and L3 of the three-phase power supply, and current waveforms Ii (i = 1 to 3) are supplied from measuring devices 110-1 to 110-3. ) And a voltage waveform Vi (i = 1 to 3) synchronized with the current waveform Ii.

FIG. 10 is a diagram illustrating a three-phase current waveform Ii (i = 1 to 3) output from the measuring devices 110-1 to 110-3 and a three-phase voltage waveform Vi (i = 1 to 3). is there.

FIG. 11 is a diagram for explaining a second exemplary embodiment of the present invention. Referring to FIG. 11, the configuration of a phase locked loop (PLL) 130 is different from that of the phase locked loop (PLL) 120 of FIG.

参照 Referring to FIG. 11, the PLL 130 includes a PF (Power Factor) maximizing control circuit 131, a phase control circuit 132, a loop filter 122, and a VCO 123.

The PF maximization control circuit 131 obtains a phase Δθ _PFMAX of an AC voltage waveform having a maximum power factor with respect to (a voltage waveform corresponding to) the AC current waveform input via the ammeter 101, the amplifier 111, and the LPF 112. .

The phase control circuit 132 calculates the phase difference Δθ between the AC voltage waveform (sine wave) output from the VCO 123 and the AC current waveform (corresponding to) from the LPF 112, and the phase output from the PF maximization control circuit 131. Compare Δθ _PFMAX . When Δθ _PFMAX is larger than the phase difference Δθ, control is performed so as to increase the oscillation frequency of VCO 123 (the phase difference between the AC voltage waveform from VCO 123 and the AC current waveform from LPF 112 (corresponding to the AC current waveform from LPF 112) is increased. Do). When Δθ _PFMAX is smaller than the phase difference Δθ, control is performed so as to lower the oscillation frequency of the VCO 123 (the phase difference between the AC voltage waveform from the VCO 123 and the voltage waveform corresponding to the AC current waveform from the LPF 112) is reduced. Do).

FIG. 12 is a diagram illustrating an example of the configuration of the PF maximization control circuit 131 and the phase control circuit 132 of FIG. In FIG. 12, an alternating current waveform (a voltage waveform corresponding to) from the LPF 112 is input to Vin1, and an alternating current waveform from the VCO 123 is input to Vin2. The PF maximization control circuit 131 includes analog to digital converters (Analog to Digital Converters) 1311A and 1311B for converting analog voltages of the voltage inputs Vin1 and Vin2 into digital signals, and an AC current waveform obtained by converting the analog signals to digital signals. PF maximizing phase calculation circuit 1312 for calculating the phase Δθ _PFMAX of the AC voltage waveform for maximizing the power factor. The PF maximizing phase calculation circuit 1312 calculates the phase difference Δθ between Vin1 and Vin2 based on the zero crossing point when Vin1 and Vin2 change from negative to positive.

In the PF maximizing phase calculation circuit 1312, for example, an AC current waveform obtained by converting an analog signal into a digital signal is represented by i (j), an AC voltage waveform obtained by converting the analog signal into a digital signal is represented by v (j), and the phase difference is represented by: When τ and the number of samples are N,

Τ (phase delay) that maximizes is obtained, and this may be _set as Δθ _PFMAX .

The number of samples N depends on the conversion speed (sampling frequency) of the ADCs 1311A and 1311B, but may be the number of samples for a plurality of AC power supply cycles.

The phase control circuit 132 includes a phase comparison circuit 1321 and a charge pump circuit 1322. The phase comparison circuit 1321 compares the phase difference Δθ with Δθ _PFMAX . FIG. 13A shows the positions of the voltage waveform 152 (sine wave) output from the VCO 123 and the voltage waveform 151 output from the LPF 112 (a waveform obtained by converting the current detected by the ammeter 101 in FIG. 11 into a voltage). An example of the phase difference Δθ is shown. FIG. _13B shows an example of the phase difference Δθ _PFMAX of the voltage waveform with the maximum power factor for the voltage waveform 152 and the current waveform 151 from the _{VCO 123} .

When Δθ _PFMAX is larger than phase difference Δθ (see FIGS. 13A and 13B), phase comparison circuit 1321 outputs an UP signal so as to increase the oscillation frequency of VCO 123.

On the other hand, when Δθ _PFMAX is smaller than the phase difference Δθ, the phase comparison circuit 1321 outputs a DOWN signal so as to lower the oscillation frequency of the VCO 123.

When the UP signal from the phase comparison circuit 1321 is activated, the charge pump circuit 1322 turns on the switch SW1 and charges the capacitor C with the discharge current (source $ current) from the constant current source 1.

When the DOWN signal from the phase comparison circuit 1321 is activated, the charge pump circuit 1322 turns on the switch SW2 and discharges the capacitor C with a sink current (sink current) from the constant current source 2. The terminal voltage of the capacitor C is smoothed by the loop filter 122 in FIG. 11 and supplied to the VCO 123 as a control voltage. According to the present embodiment, an AC voltage waveform corresponding to the AC current waveform measured by the distribution board can be generated without measuring the AC voltage at the distribution board. Note that, in FIGS. 2 and 11, the ammeter 101 and the measuring device 110 may be integrally formed. 2 and 11, the AC voltage waveform V and the AC current waveform I output from the measuring device 110 are not limited to analog signal waveforms, but may be digital signal waveforms (in this case, measurement The device 110 may be configured to communicate and output a digital signal waveform).

The disclosure of Patent Document 1 is incorporated herein by reference. Modifications and adjustments of the embodiments or examples are possible within the framework of the entire disclosure (including the claims) of the present invention and based on the basic technical concept thereof. Further, various combinations or selections of various disclosed elements (including each element of each claim, each element of each embodiment, each element of each drawing, and the like) are possible within the scope of the claims of the present invention. . That is, the present invention naturally includes various variations and modifications that can be made by those skilled in the art according to the entire disclosure including the claims and the technical idea.

101, 101-1 to 101-3 Ammeter 102 101-2 to 103-3 Voltmeter 103 Power supply 104 Load 105 Breaker 105-1 Main breaker 105-2 Branch breaker 106 Power supply line 110, 110-1 to 110-3 Measurement Device 111 Amplifier 112 LPF
120, 130 PLL
121 Phase comparator 122 Loop filter 123 VCO
131 PF maximization control circuit 132 Phase control circuits 141, 142, 151 Current waveforms 143, 152 Voltage waveforms 1011 Magnetic cores 1211, 1211A, 1211B Zero cross detection circuit 1212 Comparator 1213 Digital phase comparison circuit 1214 Phase difference detection circuit 1215 Charge pump circuit
1216 Analog multiplier 1231 Operational amplifiers 1311A, 1311B ADC
1312 PF maximization phase calculation circuit 1321 phase comparison circuit 1322 charge pump circuit

Claims (8)

1. An oscillator for generating an AC voltage signal;
   A phase comparator that detects a phase difference between a waveform of the input AC current and a waveform of the AC voltage signal generated by the oscillator,
   And a phase synchronization circuit that varies an oscillation frequency of the oscillator based on the phase difference and controls the phase difference so as to satisfy a predetermined condition.
2. 2. The measuring apparatus according to claim 1, wherein the phase synchronization circuit controls the waveform of the AC current and the phase of the waveform of the AC voltage signal generated by the oscillator so as to coincide with each other. 3.
3. The phase-locked loop circuit further includes a circuit that detects a first phase difference that is an AC voltage signal waveform that maximizes a power factor for the AC current waveform,
   The phase difference between the waveform of the AC current and the waveform of the AC voltage signal generated by the oscillator is controlled so as to be the first phase difference that maximizes the power factor. The measuring device according to claim 1.
4. A waveform of the AC current measured by an ammeter is input, and the AC voltage signal whose phase is synchronized with the waveform of the AC current by the phase synchronization circuit is output as an output signal of the measuring device. The measuring device according to any one of claims 1 to 3,
5. The measurement device according to claim 4, wherein the ammeter detects a current of a power supply line of the distribution board in a non-contact manner.
6. The phase difference between the waveform of the AC current measured by the ammeter and the waveform of the AC voltage signal generated by the oscillator included in the phase locked loop is detected, and the oscillation frequency of the oscillator is varied based on the phase difference. A voltage generation method, wherein the phase difference is controlled so as to satisfy a predetermined condition.
7. 7. The voltage generation method according to claim 6, wherein the control is performed such that the waveform of the AC current and the waveform of the AC voltage signal generated by the oscillator match in phase.
8. Detecting a first phase difference that becomes an AC voltage signal waveform that maximizes a power factor with respect to the waveform of the AC current,
   The phase difference between the waveform of the AC current and the waveform of the AC voltage signal generated by the oscillator is controlled so as to be the first phase difference that maximizes the power factor. The voltage generation method according to claim 6.

Images