JP2964673B2 - Power system failure detection circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power system fault detection circuit for detecting a system fault such as a ground fault or short circuit between power lines.

[0002]

2. Description of the Related Art In a self-excited power converter connected to a power system (a grid-connected inverter for fuel cell power generation, a grid-connected inverter for cogeneration (cogeneration), a self-excited reactive power converter, an active filter, and the like). When a system fault occurs, a sudden change of the system voltage and a phase shift may cause an overcurrent for the converter. FIG. 5 shows a conventional power system failure detection circuit for preventing occurrence of this overcurrent. In the figure, three-phase system voltages (phase voltages) e _sa , e _sb , and e _sc are rectified by a three-phase full-wave rectifier circuit 9c, and after being removed by a filter 10c, are input to a comparator 6c. The comparator 6c compares the system voltage with the set value, and detects a system failure when the system voltage falls below the set value. Then, although not shown, the operation of the power converter is stopped by performing processing such as pulse-off on the power converter based on the failure detection signal.

[0003]

According to the above-described conventional fault detection circuit, in the case of a system fault in which the three-phase system voltage is uniformly reduced, this can be accurately detected. However, there is a problem in that when the voltage level differs depending on the phase and an unbalanced state occurs with a phase shift, detection is delayed. That is, the rectifier circuit 9c cuts out a waveform near the peak value of the three-phase system voltage to obtain an output. The voltage change does not appear in the rectified output, and is detected only when the phase is near the voltage peak value. The present invention has been made in order to solve the above problems, and an object of the present invention is to provide a power system failure detection circuit that can quickly and accurately detect a system failure regardless of the type of failure. is there.

[0004]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a fault (one-wire ground fault, two-wire ground fault, three-wire ground fault, Short circuit)
In the event of occurrence, the positive-sequence voltage (balance component) decreases, and unbalance fault (fault other than three-wire ground fault, three-phase short-circuit, or three-wire disconnection)
When the occurrence of the negative phase voltage (unbalanced component) increases (occurs), the positive phase voltage and the negative phase voltage are calculated from the three-phase system voltage by symmetric coordinate conversion, and these are calculated. The gist is to detect a system failure based on the change.

That is, in the first invention, the real part and the imaginary part of the positive-phase voltage and the negative-phase voltage are respectively converted by symmetrical coordinate conversion using a three-phase system voltage and voltages having a phase difference of 90 ° with respect to the three-phase system voltages. Positive and negative phase voltage calculating means for calculating;
A positive phase that converts a positive-phase voltage and a negative-phase voltage into a DC amount based on the sum of squares of a real part and an imaginary part of the positive-phase voltage, and each square sum of a real part and an imaginary part of the negative-phase voltage, respectively. A negative-phase voltage converter and a system failure by detecting that the DC amount of the positive-phase voltage has become smaller than a set value or that the DC amount of the negative-phase voltage has become larger than a set value; And a failure detecting means.

According to a second aspect of the present invention, there is provided the positive-phase / negative-phase voltage calculating means, an amount obtained by multiplying each imaginary part by a reference sine wave synchronized with a one-phase system voltage, and a one-phase system voltage. The reference phase cosine wave synchronized with the above is added to each real number part with an amount obtained by multiplying each of the positive phase voltage and the negative phase voltage to convert the positive phase voltage and the negative phase voltage into a DC quantity, respectively. A phase voltage converter; and the failure detector.

The third invention uses a one-phase voltage of a three-phase system voltage and a voltage having a phase difference of 90.degree. With respect to the other two-phase voltages, respectively, by performing symmetrical coordinate conversion to obtain a positive phase voltage and a reverse phase voltage. Positive-phase / negative-phase voltage calculating means for respectively calculating the imaginary part of the phase voltage, and positive-phase for rectifying the imaginary part of the positive-phase voltage and the negative-phase voltage and converting the positive-phase voltage and the negative-phase voltage into DC quantities, respectively -It is provided with a reverse phase voltage conversion means and the failure detection means.

According to a fourth aspect of the present invention, a two-phase voltage of a three-phase system voltage and a voltage having a phase difference of 90 ° with respect to the other one-phase voltage are subjected to symmetric coordinate conversion by positive-phase voltage and negative-phase voltage. Positive-phase / negative-phase voltage calculation means for calculating the real part of the voltage, and positive-phase / negative-phase voltage for rectifying the real part of the positive-phase voltage and the negative-phase voltage to convert the positive-phase voltage and the negative-phase voltage into DC values, respectively. A negative-phase voltage converting means; and the failure detecting means.

[0009]

According to the first aspect, the positive-phase / negative-phase voltage calculating means calculates the real part and the imaginary part of the positive-phase voltage and the negative-phase voltage, respectively, and based on the real part and the imaginary part thereof, Negative-phase voltage conversion means converts the positive-phase voltage and the negative-phase voltage into DC values. Further, the failure detection means detects a system failure by separately detecting a decrease in the positive-phase voltage or an increase in the negative-phase voltage based on the DC amount.

According to the second aspect of the invention, the real and imaginary parts of the positive and negative phase voltages calculated by the positive and negative phase voltage calculation means, the reference sine wave synchronized with the one-phase system voltage, and On the basis of the reference cosine wave, the positive-phase / negative-phase voltage conversion means converts the positive-phase voltage and the negative-phase voltage into DC values. Then, similarly to the first invention, the failure detecting means detects a system failure.

According to the third or fourth aspect, the positive-phase / negative-phase voltage calculating means calculates the imaginary part of the positive-phase voltage and the negative-phase voltage or the real part of the positive-phase voltage and the negative-phase voltage. The imaginary part or the real part is rectified by the positive-phase / negative-phase voltage conversion means and converted into a DC amount, and the failure detection means detects a system failure as in the first and second inventions.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. First, FIG. 1 is a functional block diagram showing an embodiment of the first invention.
Reference numeral 0 denotes a positive-phase / negative-phase voltage converter, and 300 denotes a failure detector. The positive-phase / negative-phase voltage calculating means 10
At 0, e _sab , e _sbc , and e _sca are three-phase system voltages (line voltages), and 1a, 1b, and 1c are voltages e _cab , e _cbc , and e _cca whose phases are respectively advanced by 90 ° from these voltages. Is a phase shifter. Where three-phase system voltage (line voltage)
e _ab , e _bc , and e _ca are represented by the following Equation 1.

[0013]

(Equation 1)

From the definition of the symmetric coordinate transformation, the zero-phase voltage e ₀ , the positive-phase voltage e ₁ , and the negative-phase voltage e ₂ are represented by the following equation (2). In Equation 2, a and a ² are the values shown in Equations 3 and 4.

[0015]

(Equation 2)

[0016]

(Equation 3)

[0017]

(Equation 4)

Here, since e _ab , e _bc , and e _ca are line voltages, the zero-phase voltage is zero, so that the following equation 5 holds.

[0019]

(Equation 5)

Accordingly, the following equations (6) and (7) are obtained.

[0021]

(Equation 6)

[0022]

(Equation 7)

By substituting equation (1) into equation (2) and obtaining the positive-phase voltage e ₁ , equation (8) is obtained.

[0024]

(Equation 8)

Expression 9 is obtained from Expression 6, and Expression 10 is obtained from Expression 7.

[0026]

(Equation 9)

[0027]

(Equation 10)

By substituting Equations 9 and 10 into Equation 8, the following Equations 11, 12 and 13 are obtained.

[0029]

[Equation 11]

[0030]

(Equation 12)

[0031]

(Equation 13)

The above equations (11), (12) and (13)
In, e _1R is the real part of e _1, e _1I shows the imaginary part of e _1. Similarly, substituting Equation 1 into Equation ₂ to determine the negative-phase voltage e ₂ yields Equation 14.

[0033]

[Equation 14]

By substituting Equations 9 and 10 into Equation 14, the following Equations 15, 16 and 17 are obtained.

[0035]

(Equation 15)

[0036]

(Equation 16)

[0037]

[Equation 17]

The above equations (15), (16) and (17)
In, e _2R is the real part of e _2, e _2I shows the imaginary part of e _2.

Thus, the three-phase system voltages e _sab , e
_{From sbc} and e _sca , a positive-phase voltage e ₁ as an equilibrium component and a negative-phase voltage e ₂ as an unbalanced component can be obtained by symmetric coordinate conversion. By separating and detecting a decrease or increase in the reverse-phase voltage e ₂ of the positive-phase voltage e _1, it is possible to detect the line fault at a high speed.

That is, in FIG. 1, the phase shifter 1
The adders / subtractors 2a to 2f after a, 1b, and 1c and the gain adjusters 3a to 3d with the illustrated gains are set to e _1R and e _1I by the calculations of the above formulas 11 to 13 and formulas 15 to 17. , E _2R , e _2I , and e _1I , e _2I , e _1R , e from the _{adders /} subtractors 2c, 2d, 2e, 2f.
_2R is output respectively. Here, since e _1R and e _1I , and e _2R and e _2I are sine waves having a phase difference of 90 °, respectively, the DC amounts of the positive-phase voltage and the negative-phase voltage | e ₁ | , | E ₂ |.

[0041]

(Equation 18)

[0042]

[Equation 19]

Equations (18) and (19) are calculated by a circuit including the multipliers 4a to 4d, the adders / subtractors 2g and 2h and the square root calculators 5a and 5b in FIG. 1, and | e ₁ | Also, from the square root calculator 5b |
e ₂ | is output. Then, the comparator 6 at the subsequent stage
Reference numerals a and 6b denote comparators for detecting that the DC amount | e ₁ | of the positive-phase voltage has decreased below the set value or that the DC amount | e ₂ | of the negative-phase voltage has increased above the set value. . The output signals of these comparators 6a and 6b are ORed.
Is input to the gate 7 and | e ₁ | decreases or | e ₂
When | increases, a failure detection signal is output from the OR gate 7 instantaneously.

As described above, according to the present embodiment, a failure (1 line ground fault, 2 line ground fault, 2
When a line ground fault, three-wire ground fault, short-circuit between lines occurs, the positive-phase voltage decreases. When an unbalance fault occurs (fault other than three-wire ground fault, three-phase short-circuit, or three-wire break), the reverse occurs. Because the phase voltage increases,
By detecting these phenomena by the comparators 6a and 6b, a system failure can be detected at high speed. In addition,
The square root calculators 5a and 5b can be omitted. In this case, the values of | e ₁ | ² and | e ₂ | ² are input to the comparators 6a and 6b and are compared with set values to detect a failure. become. Although not shown, the three-phase system voltage e _sab ,
Voltages each having a phase delayed by 90 ° from e _sbc and e _sca are generated by a phase shifter, and a positive voltage is obtained using the voltages obtained by inverting the polarities of these voltages and the three-phase system voltages e _sab , e _sbc and e _sca. The real part and the imaginary part of the phase voltage and the negative phase voltage may be generated.

Next, FIG. 2 is a functional block diagram showing an embodiment of the second invention. The structure of the positive-phase / negative-phase voltage conversion means 200A for calculating | e ₁ | and | e ₂ | But Figure 1
Circuit is different. The same components as those in FIG. 1 are denoted by the same reference numerals. In FIG. 2, reference _numeral 8 denotes a function generator for generating a reference sine wave sinωt and a reference cosine wave cosωt synchronized with the system voltage e _sab for one phase. e ₁
|, | E ₂ | are calculated.

[0046]

| E ₁ | = e _1R · cos ωt + e _1I · sin ωt

[0047]

| E ₂ | = e _2R · cos ωt + e _2I · sin ωt

That is, the reference sine wave sinωt and the reference cosine wave cosωt are input to multipliers 4a to 4d together with e _1I , e _2I , e _1R and e _2R , and the outputs thereof are added / subtracted by 2g and 2h.
| E ₁ | from the adder / subtractor 2g and | e ₂ | from the adder / subtractor 2h. And
By comparing with the set value by the comparators 6a and 6b in the same manner as described above, the DC amount | e ₁ |
Or OR by detecting an increase in the DC amount | e ₂ |
The gate 7 outputs a failure detection signal. The input of the function generator 8 may take in the system voltage of another phase.

FIG. 3 is a functional block diagram showing an embodiment of the third invention, in which the same components as those in FIG. 1 or 2 are denoted by the same reference numerals. This embodiment is the reduced, it detects a system fault from increased converts the imaginary part of the positive phase voltage e ₁ and negative phase voltage e ₂ into a DC of positive-phase voltage e ₁ and negative phase voltage e ₂ is there. That is, the operations of Equations 13 and 17 are performed by the phase shifters 1b, 1c, the adders / subtractors 2b, 2c, 2d, and the gain adjusters 3a, 3d in the positive-phase / negative-phase voltage calculating means 100A, and e _1I , e. _{Find 2I} ,
Rectifier circuits 9a and 9 in positive-phase / negative-phase voltage conversion means 200B
b and smoothed by the filters 10a and 10b, and then the comparators 6a and 6b in the failure detecting means 300.
Detects a decrease in | e ₁ | or an increase in | e ₂ | to obtain a failure detection signal from the OR gate 7.

FIG. 4 is a functional block diagram showing an embodiment of the fourth invention, and the same components as those in FIGS. 1 to 3 are denoted by the same reference numerals. This embodiment is the reduced, it detects a system fault from increased converts the real part of the positive phase voltage e ₁ and negative phase voltage e ₂ into a DC of positive-phase voltage e ₁ and negative phase voltage e ₂ is there. That is, the operations of Equations 12 and 16 are performed by the phase shifter 1a, the adders / subtractors 2a, 2e, 2f, and the gain adjusters 3b, 3c in the positive-phase / negative-phase voltage calculation means 100B, and e _1R and e _2R are calculated. Then, after rectification and smoothing by the rectifier circuits 9a and 9b and the filters 10a and 10b in the positive-phase / negative-phase voltage conversion means 200B, they are input to the failure detection means 300 in the same manner as described above to obtain a failure detection signal.

Although not shown, Equations 13 and 1
6 calculated by e _1I of seeking e _2R, or e _1R by calculation of Equation 12 and Equation 17, Figure 3 seeking e _2I, the process of the positive and negative phase voltage converter 200B after the same manner as FIG. 4 By doing so, it is possible to detect a failure.

[0052]

As described above, according to the first to fourth aspects of the present invention, the three-phase system voltage is input and converted into a positive-phase voltage and a negative-phase voltage by symmetrical coordinate conversion, and these are separated to set values. The system fault is detected by comparing with, so that the system fault can be detected quickly and accurately without delay in detection, including the unbalance fault in all modes such as ground fault and short circuit between lines. .

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing an embodiment of the first invention.

FIG. 2 is a functional block diagram showing an embodiment of the second invention.

FIG. 3 is a functional block diagram showing an embodiment of the third invention.

FIG. 4 is a functional block diagram showing an embodiment of the fourth invention.

FIG. 5 is a functional block diagram showing a conventional technique.

[Explanation of symbols]

 1a, 1b, 1c Phase shifter 2a, 2b, 2c, 2d, 2e, 2f Adder / subtractor 3a, 3b, 3c, 3d Gain adjuster 4a, 4b, 4c, 4d Multiplier 5a, 5b Square root calculator 6a, 6b Comparator 7 OR gate 8 Function generator 9a, 9b Rectifier circuit 10a, 10b Filter 100, 100A, 100B Positive / negative phase voltage calculating means 200, 200A, 200B Positive / negative phase voltage converting means 300 Failure detecting means

Claims (4)

(57) [Claims] 1. Three-phase system voltages and 90% each for these
Positive and negative phase voltage calculation means for calculating the real and imaginary parts of the positive and negative phase voltages by symmetric coordinate conversion using a voltage having a phase difference of °, and the real and imaginary parts of the positive phase voltage A positive-phase / negative-sequence voltage conversion means for converting a positive-phase voltage and a negative-phase voltage into a DC amount based on each of the square sums of the real part and the imaginary part of the negative-phase voltage, respectively, Failure detection means for detecting that the DC amount of the positive-phase voltage has become smaller than the set value, or detecting that the DC amount of the negative-phase voltage has become larger than the set value, thereby detecting a system failure. A power system failure detection circuit characterized by the above-mentioned. 2. The three-phase system voltage and for each of them 90
Positive-phase / negative-phase voltage calculating means for calculating the real part and the imaginary part of the positive-phase voltage and the negative-phase voltage by symmetric coordinate conversion using a voltage having a phase difference of °, and a reference synchronized with the one-phase system voltage. The amount obtained by multiplying each of the imaginary parts by the sine wave and the amount obtained by multiplying each of the real parts by the reference cosine wave synchronized with the one-phase system voltage are represented by a positive-phase voltage and a negative-phase voltage, respectively. Positive-phase / negative-phase voltage conversion means for adding and converting the positive-phase voltage and the negative-phase voltage into DC amounts, respectively, and that the DC amount of the positive-phase voltage is smaller than a set value, or A power system failure detection circuit, comprising: a failure detection unit that detects that a DC amount has become larger than a set value and detects a system failure. 3. An imaginary number of a positive-phase voltage and a negative-phase voltage by symmetric coordinate conversion using a one-phase voltage of a three-phase system voltage and voltages having a phase difference of 90 ° with respect to the other two-phase voltages. And negative-phase voltage calculating means for calculating the positive-phase and negative-phase voltages, respectively, and rectifying the imaginary part of the positive-phase and negative-phase voltages to convert the positive-phase and negative-phase voltages into DC quantities, respectively. Conversion means, and fault detection means for detecting that the DC amount of the positive-sequence voltage has become smaller than the set value, or detecting that the DC amount of the negative-sequence voltage has become larger than the set value, thereby detecting a system fault. And a power system fault detection circuit. 4. A real part of a positive-phase voltage and a negative-phase voltage by symmetric coordinate conversion using a two-phase voltage of a three-phase system voltage and a voltage having a phase difference of 90 ° with respect to another one-phase voltage. And a positive-phase / negative-phase voltage conversion means for rectifying the real parts of the positive-phase voltage and the negative-phase voltage to convert the positive-phase voltage and the negative-phase voltage into DC values, respectively. Means,
Failure detection means for detecting that the DC amount of the positive-phase voltage has become smaller than the set value, or detecting that the DC amount of the negative-phase voltage has become larger than the set value, thereby detecting a system failure. A power system failure detection circuit characterized by the above-mentioned.