JPH07146717A - Correction method for phase difference detection circuit and the phase difference detection circuit - Google Patents

Abstract

PURPOSE:To provide a method for correcting the dispersion of phase lags provided in a phase difference detection circuit at the time of matching the phases of an inverter and a commercial power supply and a circuit therefor. CONSTITUTION:This method is constituted of a subtracting circuit 20 for subtracting inverter output voltage waveforms Vi from commercial voltage waveforms Vc, a comparator 11 for converting the output to rectangular waves and an amplifier 20 and the comparator 12 similarly for the inverter output voltage waveforms Vi. Further, the output of the comparator 11 and the comparator 12 is compared in one comparator 13 ana the delay amount or a delay circuit to is corrected by the output in a delay correction circuit 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to, for example, an uninterruptible power supply device using an inverter, in which the output voltage waveform of the inverter and the voltage waveform of the commercial power supply are preliminarily set when the inverter fails and power is supplied to the load from the commercial power supply. The present invention relates to a phase difference detection circuit including a correction method and a correction circuit for correcting variations in phase delay included in a phase difference detector that detects a phase difference between the two when performing phase matching, that is, when performing so-called synchronization control. .

[0002]

2. Description of the Related Art A conventional phase difference detection circuit and a correction method will be described with reference to FIG. In FIG.
Is the output voltage of the inverter obtained from the detector not shown in the inverter output, Vc is the commercial power supply voltage obtained from the detector not shown in the figure, 1 is an RC filter for shaping the output voltage Vi of the inverter, 2 Is a comparator that converts the output of the RC filter 1 into a square wave, 3 is a delay circuit that delays the output of the comparator 2, similarly, 4 is an RC filter that shapes the voltage Vc of the commercial power supply, and 5 is RC
A comparator for converting the output of the filter 4 into a square wave, 6
Is a delay circuit that delays the output of the comparator 5, 7 is a comparator that compares the output of the delay circuit 3 and the output of the delay circuit 6, and 8 is an oscilloscope that observes the waveforms of the output voltage Vi of the inverter and the voltage Vc of the commercial power supply. is there.

By comparing the outputs of the comparators 2 and 5, the output voltage Vi of the inverter and the voltage Vc of the commercial power source are compared.
However, since the RC filters 1 and 4 have variations in the characteristics of the phase delay between the input and the output, this variation causes the output of the comparator 7 to be inaccurate, resulting in an incorrect output. Phase difference cannot be obtained. Therefore, the waveforms of the output voltage Vi of the inverter and the voltage Vc of the commercial power supply before the input of the RC filters 1 and 4 are measured by the oscilloscope 8
And the variation in the characteristics of the RC filter 1 and the RC filter 4 is corrected by adjusting the delay amount of the delay circuit 3 or the delay circuit 6 so that the phase difference between these two waveforms disappears.

[0004]

SUMMARY OF THE INVENTION In the above conventional method,
The correction of the phase delay variation of the phase difference detection circuit is performed manually while looking at the oscilloscope. For example, even if the screen of the oscilloscope is enlarged, the accuracy of the correction is limited. An object of the present invention is to provide a correction method of a phase difference detection circuit and a phase difference detection circuit that improve the correction accuracy of the phase delay variation of the phase difference detection circuit and automate the correction work.

[0005]

In order to solve the above problems, according to the present invention, the output voltage of the inverter and the voltage of the commercial power source are converted into square waves by a filter and a comparator, respectively, and the two square waves are converted. By inputting each to the delay circuit and adjusting the delay amount of the delay circuit, the variation of the phase delay of the square wave by the filter is corrected, and the outputs of the two delay circuits are compared and calculated to output the output voltage of the inverter. In the correction method of the phase difference detection circuit for detecting the phase difference between the voltage of the commercial power source and the voltage of the commercial power source, the output voltage of the inverter and the voltage of the commercial power source are subtracted and the amplitude of the output voltage of the inverter is changed to the commercial power source. Of the delay circuit based on the phase difference amount obtained by comparing the output voltage of the inverter with the subtraction operation after adjusting the value to a value larger than the amplitude of the voltage And adjusts the amount of delay.

Further, in the phase difference detection circuit, a first RC filter and a first comparator for converting the output voltage of the inverter into a square wave, a first delay circuit for delaying the output of the first comparator, and a commercial circuit A second RC filter and a second comparator for converting the voltage of the power supply into a square wave, a second delay circuit for delaying the output of the second comparator, and the outputs of the first and second delay circuits are compared. A phase difference detection circuit configured to include a third comparator and detecting a phase difference between the output voltage of the inverter and the voltage of the commercial power supply by a comparison operation of the third comparator, and outputs of the first and second RC filters. Is provided with a correction circuit that corrects the variation in the phase delay by adjusting at least one of the delay amounts of the first and second delay circuits. Of the output voltage of the commercial power source and a subtraction circuit for performing a subtraction operation between the output voltage of the commercial power supply and a fourth comparator for converting the output of the subtraction circuit into a square wave, and an input / output phase delay characteristic equivalent to that of the subtraction circuit. An amplifier for amplifying the output voltage of the inverter; a fifth comparator for converting the output of the amplifier into a square wave; a sixth comparator for comparing the outputs of the fourth and fifth comparators; And a delay correction circuit for correcting the delay amount of the first delay circuit by the output of the six comparators.

[0007]

According to the above method and configuration, the square wave converted from the subtraction result obtained by subtracting the output voltage Vi of the inverter from the voltage Vc of the commercial power source is compared with the square wave converted from the output voltage Vi of the inverter. The phase difference between these two square waves is obtained, and the delay amount of the delay circuit is calculated from this phase difference.

Here, with respect to the basic principle of the present invention, that is, the basic principle in which the amount to be corrected is calculated by the subtraction operation as described above, 2 having a slight phase difference φ ₁
Consider two voltages V _{A and} V _B as an example. V _A, V _B are shown below, respectively (1), it is represented by equation (2).

[0009]

## EQU1 ## V _A = A · sin ωt (1)

[0010]

V _B = B · sin (ωt−φ ₁ ) (2) where A is the amplitude of V _A , ω is the angular frequency of the voltages V _{A and} V _B , B is the amplitude of V _B , and φ ₁ is It is the phase difference between the voltage V _A and the voltage V _B. Next, when the difference between the above equations (1) and (2) is obtained, equation (3) is obtained.

[0011]

Equation 3] _{V A -V B = A · sinωt} -B · sin (ωt-φ 1) = - (A 2 + B 2 -2ABcosφ 1) 1/2 × sin (ωt-φ 2) (3) where, φ ₂ = tan ⁻¹ [Bsinφ ₁ / (Bcosφ ₁
-A)] For example, when A = 0.8, B = 1.0 and φ ₁ = 2 ° are calculated, the amplitude of the subtraction result is 0.2 and the phase difference φ ₂ ≈10.
The phase difference of only 2 ° can be obtained as a value of about 10 °.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a block diagram of an embodiment of the present invention. In FIG. 1, those having the same functions as those in FIG. In FIG. 1, a comparator for converting the output of the subtraction circuit 20 for subtracting the output voltage Vi of the inverter, which is also shown in the figure, from the voltage Vc of the commercial power source obtained by the detector, not shown, into a square wave. 11 and the output voltage Vi of the inverter
The amplifier 30 that amplifies is made similar to the phase delay characteristic of the subtraction circuit 20 by making the circuit configuration similar to that of the subtraction circuit 20, and the output of the amplifier 30 is input to the comparator 12 that converts it into a square wave. When the output of the comparator 13 has a phase difference between the voltage Vc of the commercial power supply and the output voltage Vi of the inverter, the subtraction and comparison are performed by comparing the output of the comparator 13 with the output of the comparator 12 as described above. Thus, the phase difference appears enlarged. By the output of this comparator 13,
By correcting the delay amount of the delay circuit 10 with the delay correction circuit 14, the variation in the phase delay between the input and output of the RC filter 1 and the RC filter 4 can be corrected more accurately than the conventional method.

In the subtraction circuit 20, in order to make the amplitude of the output voltage of the inverter at the time of the subtraction operation larger than the amplitude of the voltage of the commercial power source at the time of the subtraction operation, FIG.
This is possible by setting the circuit constants of the subtraction circuit 20 shown in the circuit example of FIG. 5A, and the circuit configuration and the circuit constants may be different depending on the operational amplifier element (op amp) used.

Further, when the function of the delay correction circuit 14 is realized by a microprocessor or the like, the voltage V of the commercial power source is used.
In the subtraction operation of c and the output voltage Vi of the inverter, the correction amount which is the output of the delay correction circuit 14 can be calculated by a combination other than the subtraction operation method shown in FIG. Although the variation of the RC filters 1 and 4 is corrected by adjusting the delay amount of the delay circuit 10 on the inverter side in the present embodiment, similarly, the delay amount of the delay circuit 6 on the commercial power source side is adjusted. It is possible to correct the variations of the RC filters 1 and 4 due to this, and also by adjusting the delay amounts of the delay circuits 6 and 10 together.
Can be corrected.

[0015]

According to the present invention, the phase difference amount obtained by comparing the value obtained by subtracting the output voltage Vi of the inverter and the voltage Vc of the commercial power source with the output voltage Vi of the inverter is obtained. By adjusting the delay amount of the delay circuit based on this, it is possible to accurately correct the variation in the characteristics of the phase difference detection circuit, and it is possible to automate the correction work.

Further, when the subtraction operation of the output voltage of the inverter and the voltage of the commercial power source is performed, the amplitude of the output voltage of the inverter is adjusted to a value larger than the amplitude of the voltage of the commercial power source, so that there is no phase difference between them. Even in such a case, the subtraction result does not become zero and an output having the same phase as the output voltage of the inverter can be obtained. Therefore, it is possible to detect "the correction of the delay amount is unnecessary" and operate as a suitable phase difference detection circuit.

Further, since the accuracy of the phase difference detected by the phase difference detection circuit is improved, the performance and accuracy of synchronization control, for example, are also improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a configuration diagram showing a conventional example.

[Explanation of symbols]

1, 4 ... RC filter, 2, 5 ... Comparator, 3, 6
... delay circuit, 7 ... comparator, 8 ... oscilloscope,
10 ... Delay circuit, 11, 12 ... Comparator, 13 ... Comparator, 14 ... Delay correction circuit, 20 ... Subtraction circuit, 3
0 ... Amplifier, Vc ... Commercial power supply voltage, Vi ... Inverter output voltage.

Claims (4)

[Claims] 1. An inverter output voltage and a commercial power supply voltage are converted into a square wave by a filter and a comparator, respectively.
By inputting each of the two square waves into a delay circuit and adjusting the delay amount of the delay circuit, the variation in the phase delay of the square wave due to the filter is corrected, and the outputs of the two delay circuits are compared and calculated. In the correction method of the phase difference detection circuit for detecting the phase difference between the output voltage of the inverter and the voltage of the commercial power supply, the value obtained by subtracting the output voltage of the inverter and the voltage of the commercial power supply, and the inverter The method for correcting a phase difference detection circuit is characterized in that the delay amount of the delay circuit is adjusted based on the phase difference amount obtained by comparing the output voltage with the output voltage. 2. The correction method for a phase difference detection circuit according to claim 1, wherein the amplitude of the output voltage of the inverter is amplified to a value larger than the amplitude of the voltage of the commercial power source, and then the subtraction operation is performed. And a method of correcting the phase difference detection circuit. 3. A first RC filter and a first comparator for converting an output voltage of the inverter into a square wave, and the first RC filter.
A first delay circuit for delaying the output of the comparator, a second RC filter and a second comparator for converting the voltage of the commercial power source into a square wave, and a second delay circuit for delaying the output of the second comparator.
A delay circuit and a third comparator for comparing the outputs of the first and second delay circuits are provided, and the phase difference between the output voltage of the inverter and the voltage of the commercial power source is calculated by the comparison operation of the third comparator. In the phase difference detection circuit for detecting, by adjusting the variation of the phase delay of the output of the first and second RC filters, at least one of the delay amounts of the first and second delay circuits is adjusted. A correction circuit is provided for correcting, the correction circuit includes a subtraction circuit that performs a subtraction operation between the output voltage of the inverter and the voltage of the commercial power supply, and a fourth comparator that converts the output of the subtraction circuit into a square wave. An amplifier having an input / output phase delay characteristic equivalent to that of the subtraction circuit, which amplifies the output voltage of the inverter,
A fifth comparator for converting the output of the amplifier into a square wave, a sixth comparator for comparing the outputs of the fourth and fifth comparators, and a delay of the first delay circuit by the output of the sixth comparator. A phase difference detection circuit comprising a delay correction circuit for correcting the amount. 4. The phase difference detection circuit according to claim 3, wherein the subtraction circuit adjusts the amplitude of the output voltage of the inverter to a value larger than the amplitude of the voltage of the commercial power supply to perform subtraction operation. Phase difference detection circuit.