A method for judging the demagnetization impedance circle of a generator

Abstract

The invention discloses a method for determining a demagnetization impedance circle criterion of a generator, comprising: obtaining impedance parameters and different static stability limit angles of a salient pole generator, inputting a static stability limit equation of the generator, and calculating a machine-end measurement impedance on a static stability boundary; calculating a static stability boundary impedance modulus at a current impedance angle at set interval angles according to the machine-end measurement impedance on the static stability boundary, and storing the static stability boundary impedance modulus as a fixed value in a preset storage chip; obtaining current voltage and current data of the machine end, and calculating a current measurement impedance modulus and an impedance angle; comparing the current measurement impedance modulus with the static stability boundary impedance modulus corresponding to its impedance angle, and entering an impedance action zone if the current measurement impedance modulus is less than the static stability boundary impedance modulus corresponding to its impedance angle; the invention can determine the static stability impedance circle criterion of a salient pole machine, and only when the fixed value is modified, the static stability boundary impedance fixed value is calculated once and the fixed value is solidified, so that the criterion is simple and reliable during protection operation.

Description

Technical Field

[0001] The invention relates to a generator demagnetization impedance circle criterion determination method, belonging to the technical field of generator protection. Background Art

[0002] The static stability low impedance boundary simulation of the current hydro-generator demagnetization protection is generally replaced by the offset circular impedance boundary simulation that is the same as that of the thermal generator, which inevitably brings some actual deviations. The electrical structure of the hydro-generator is different from that of the thermal generator, and their static stability equations are also different (X d ≠X q ), which determines that the static low impedance boundary of the hydro-generator demagnetization protection is not a regular circle, and therefore the conventional method cannot be used to determine whether the measured impedance at the machine end enters the static impedance circle. Therefore, a method is needed to determine the demagnetization impedance circle criterion of the salient pole generator. Summary of the invention

[0003] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a method for determining a generator demagnetization impedance circle, which can determine whether the measured impedance at the end of a salient pole generator enters a static impedance circle.

[0004] To achieve the above object, the present invention is implemented by adopting the following technical solutions:

[0005] The present invention provides a generator demagnetization impedance circle criterion determination method, which is applied to a protection device and includes:

[0006] Obtain the impedance parameters and different static stability limit angles of the salient pole generator, input the static stability limit equation of the generator, and calculate the measured impedance of the generator end on the static stability boundary;

[0007] Based on the measured impedance of the machine end on the static boundary, the static boundary impedance modulus under the current impedance angle is calculated at every set interval angle according to the impedance angle, and the static boundary impedance modulus is stored as a fixed value in a preset storage chip;

[0008] Obtain the current voltage and current data of the machine end, and calculate the current measured impedance modulus and impedance angle;

[0009] The current measured impedance modulus is compared with the static boundary impedance modulus corresponding to its impedance angle. If the current measured impedance modulus is smaller than the static boundary impedance modulus corresponding to its impedance angle, the impedance protection action area is entered.

[0010] Furthermore, the machine-side measurement impedance Z on the static boundary is C Represented as a point Z on the impedance plane C (R C ,X C ), where R C and XC The impedance Z C The resistance and reactance of the C for:

[0011] When Z C When in quadrants 1 and 4,

[0012] When Z C When in quadrants 2 and 3,

[0013] in:

[0014]

[0015] Intermediate parameters X qΣ =X q +X s , X dΣ =X d +X s , X q is the generator quadrature-axis synchronous reactance, X d is the direct-axis synchronous reactance of the generator, X s is the connecting reactance of the generator system, θ j is the limit power angle of the generator under any state of 0% to 100% load, arctg() is the inverse tangent function, sin() is the sine function, and cos() is the cosine function.

[0016] Furthermore, the limit power angle θ j The value range of θ is 0°~179°, j Taking values ​​every 1°, a series of different static boundary impedances Z are generated C0 (R C0 ,X C0 ), Z C1 (R C1 ,X C1 )…Z C179 (R C179 ,X C179 ), the corresponding impedance angle is β C0 , β C1 …β C179 .

[0017] Furthermore, according to the measured impedance on the static boundary, the impedance modulus constant Z with the impedance angle as the index number is calculated. gx (R gx ,X gx ), the impedance angle is α gx , x=0~359.

[0018] Furthermore, the static boundary impedance modulus Z at the current impedance angle is calculated every 1° of the impedance angle. g (R g ,X g ), the static boundary impedance modulus is stored as a constant in a preset storage chip, wherein R g and X g The impedance Z g The specific methods include:

[0019] Determine the 0th constant Z g0 (R g0 ,X g0 )=Z C0 (R C0 ,X C0 ), impedance angle α g0 =0-90=-90(°);

[0020] Determine the 180th constant Z g180 (R g180 ,X g180 )=Z C90 (R C90 ,X C90 ), impedance angle α g180 =180-90=90(°);

[0021] Determine the nth constant Z gn (R gn ,X gn ), impedance angle α gn =n-90(°), n=1~359(n≠180), the known measured impedance Z on the static boundary C Find Z Cn1 (R Cn1 ,X Cn1 ) and Z Cn2 (R Cn2 ,X Cn2 ), 0<n1≤179, 0<n2≤179, its impedance angle β Cn1 and β Cn2 Satisfy β Cn1 ≤α gn ≤β Cn2 ,but:

[0022] When α gn =β Cn1 , Z gn (R gn ,X gn )=Z Cn1 (R Cn1 ,X Cn1 )

[0023] When αgn =β Cn2 , Z gn (R gn ,X gn )=Z Cn2 (R Cn2 ,X Cn2 )

[0024] When β Cn1 <α gn <β Cn2 ,

[0025]

[0026] Where, tg() is the tangent function;

[0027] From the above steps, we can get all Z gIndex (R gIndex ,X gIndex ), impedance angle α gIndex = Index-90(°), Index = 0~359, calculate And stored in a preset storage chip.

[0028] Further, the obtaining of current voltage and current data of the machine end, calculating the current measured impedance modulus and impedance angle; and comparing the current measured impedance modulus with the static boundary impedance modulus corresponding to the impedance angle include:

[0029] Calculate the current measured impedance modulus |Z op |, the formula is as follows:

[0030]

[0031]

[0032] Where U φφ Phase-to-phase voltage at the machine end, I φφ Machine-end phase-to-phase current;

[0033] Calculate the impedance angle α op , the formula is as follows:

[0034] When Z op When in quadrants 1 and 4,

[0035] When Z op When in quadrants 2 and 3,

[0036] When α op When the value is not an integer, it can be rounded off to get the index of the current required constant from the impedance angle.op )+90, where INT() means rounding to the nearest integer, and then the modulus value of the current required static stability boundary |Z is obtained. gIndex |, when |Z op |<|Z gIndex |, it enters the impedance circle action area.

[0037] In a second aspect, the present invention provides a generator demagnetization impedance circle criterion determination device, comprising:

[0038] The first calculation unit is used to obtain the impedance parameters and different static stability limit angles of the salient pole generator, input the static stability limit equation of the generator, and calculate the machine-end measurement impedance on the static stability boundary;

[0039] A second calculation unit is used to calculate the impedance modulus of the static boundary impedance at the current impedance angle according to the impedance angle at every set interval angle measured by the machine end on the static boundary, and store the static boundary impedance modulus as a fixed value in a preset storage chip;

[0040] The third calculation unit is used to obtain the current voltage and current data of the machine end and calculate the current measured impedance modulus and impedance angle;

[0041] The comparison and judgment unit is used to compare the current measured impedance modulus with the static boundary impedance modulus corresponding to its impedance angle. If the current measured impedance modulus is smaller than the static boundary impedance modulus corresponding to its impedance angle, the impedance action area is entered.

[0042] In a third aspect, the present invention provides a generator demagnetization impedance circle criterion determination device, including a processor and a storage medium;

[0043] The storage medium is used to store instructions;

[0044] The processor is configured to operate according to the instructions to execute the steps of any of the aforementioned methods.

[0045] In a fourth aspect, the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of any of the aforementioned methods.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] The present invention provides a method for determining a generator demagnetization impedance circle criterion. The static low impedance boundary of the demagnetization protection of a hydro-turbine generator is not a regular circle, and thus the conventional implementation method cannot be used to determine whether the impedance measured at the machine end enters the static impedance circle. The method for determining a generator demagnetization impedance circle criterion provided by the present invention can determine the static impedance circle criterion of a salient pole machine. Only when the fixed value is modified, the static boundary impedance fixed value is calculated once and the fixed value is solidified. The criterion is simple and reliable during protection operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 is a flowchart of the implementation method;

[0049] Figure 2 The measured impedance Z at the machine end is obtained based on the static stability equation of the salient pole machine. C Trajectory diagram;

[0050] Figure 3 Based on the known impedance Z C Z calculated every 1° g Distribution diagram. DETAILED DESCRIPTION

[0051] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0052] Example 1

[0053] This embodiment introduces a generator demagnetization impedance circle determination method, which is applied to a protection device and includes:

[0054] Obtain the impedance parameters and different static stability limit angles of the salient pole generator, input the static stability limit equation of the generator, and calculate the measured impedance of the generator end on the static stability boundary;

[0055] Based on the measured impedance of the machine end on the static boundary, the static boundary impedance modulus under the current impedance angle is calculated at every set interval angle according to the impedance angle, and the static boundary impedance modulus is stored as a fixed value in a preset storage chip;

[0056] Obtain the current voltage and current data of the machine end, and calculate the current measured impedance modulus and impedance angle;

[0057] The current measured impedance modulus is compared with the static boundary impedance modulus corresponding to its impedance angle. If the current measured impedance modulus is smaller than the static boundary impedance modulus corresponding to its impedance angle, the impedance protection action area is entered.

[0058] The application process of the generator demagnetization impedance circle determination method provided in this embodiment specifically involves the following steps:

[0059] Step 1: Calculate the measured impedance Z on the static boundary of the generator according to the static limit equation of the salient pole generator C ;

[0060] Step 2: Based on the known measured impedance Z on the static boundary C (R C ,X C ), calculate the static boundary impedance Z at every 1° impedance angleg (R g ,X g ), and its modulus value is stored as a fixed value in a preset storage chip. C and X C The impedance Z C Resistance and reactance; R g and X g The impedance Z g resistance and reactance;

[0061] Step 3: The protection device obtains the voltage and current samples at the machine end and calculates the current measured impedance modulus value |Z op | and impedance angle α op , if the current measured impedance modulus is less than the static limit impedance modulus corresponding to its impedance angle |Z g |, then it enters the impedance circle action area.

[0062] Furthermore, the measured impedance of the machine end on the static boundary can be expressed as a point Z on the impedance plane: C (R C ,X C ), its impedance angle is:

[0063] When Z C When in quadrants 1 and 4,

[0064] When Z C When in quadrants 2 and 3,

[0065] in:

[0066]

[0067] X qΣ =X q +X s , X dΣ =X d +X s , X q is the generator quadrature-axis synchronous reactance, X d is the direct-axis synchronous reactance of the generator, X s is the connecting reactance of the generator system, θ j is the limit power angle of the generator under any state of 0% to 100% load, arctg() is the inverse tangent function, sin() is the sine function, and cos() is the cosine function.

[0068] Furthermore, the limit power angle θ j Due to the different load conditions of the generator, its value range is 0°~179°, θj Every 1°, there is a series of different static boundary impedances Z C0 (R C0 ,X C0 ), Z C1 (R C1 ,X C1 )…Z C179 (R C179 ,X C179 ), the corresponding impedance angle is β C0 , β C1 …β C179 .

[0069] Furthermore, the impedance modulus constant Z with the impedance angle as the index number can be calculated based on the measured impedance on the static boundary. gx (R gx ,X gx ), the impedance angle is α gx , x=0~359.

[0070] The steps of calculating the static boundary impedance modulus table at impedance angles every 1° are as follows:

[0071] The first step is to determine the 0th constant Z g0 (R g0 ,X g0 )=Z C0 (R C0 ,X C0 ), impedance angle α g0 =0-90=-90(°);

[0072] The second step is to determine the 180th fixed value Z g180 (R g180 ,X g180 )=Z C90 (R C90 ,X C90 ), impedance angle α g180 =180-90=90(°);

[0073] The third step is to determine the nth constant Z gn (R gn ,X gn ), impedance angle α gn =n-90(°), n=1~359(n≠180), the known measured impedance Z on the static boundary C Find Z Cn1 (R Cn1 ,X Cn1 ) and Z Cn2 (R Cn2 ,X Cn2 ), 0<n1≤179, 0<n2≤179, its impedance angle βCn1 and β Cn2 Satisfy β Cn1 ≤α gn ≤β Cn2 ,but:

[0074] When α gn =β Cn1 , Z gn (R gn ,X gn )=Z Cn1 (R Cn1 ,X Cn1 )

[0075] When α gn =β Cn2 , Z gn (R gn ,X gn )=Z Cn2 (R Cn2 ,X Cn2 )

[0076] When β Cn1 <α gn <β Cn2 ,

[0077]

[0078] Where, tg() is the tangent function;

[0079] The fourth step is to obtain all Z from the above three steps gIndex (R gIndex ,X gIndex ), impedance angle α gIndex = Index-90(°), Index = 0~359, calculate And stored in a preset storage chip.

[0080] The current measured impedance and modulus are calculated by sampling the voltage and current at the machine end:

[0081]

[0082]

[0083] Where U φφ Phase-to-phase voltage at the machine end, I φφ Machine end phase current.

[0084] Impedance angle:

[0085] When Z op When in quadrants 1 and 4,

[0086] When Z op When in quadrants 2 and 3,

[0087] When α op When the value is not an integer, it can be rounded off. op )+90 (INT() means rounding to the nearest integer), and then get the modulus value of the current required static stability boundary | Z gIndex |, when |Z op |<|Z gIndex |, it enters the impedance circle action area.

[0088] Example 2

[0089] In some specific implementation examples, taking a 700MW hydro-turbine generator as an example, its reactance parameters are as follows:

[0090] X d =74.8Ω, X q =57.1Ω, X s =17.0Ω

[0091] Then X qΣ =X q +X s =57.1,X dΣ =X d +X s =91.8, Limit power angle θ j =0°~179°.

[0092] (I) Calculation of static boundary impedance Z based on the static equation of salient pole generator C

[0093] Substituting the above parameters into the static stability equation of the salient pole generator, some data are calculated as shown in the following table:

[0094] Table 1 Static boundary impedance Z C

[0095]

[0096] Static boundary impedance Z C The trajectory diagram is as follows Figure 2 As shown in the figure, since the impedance points calculated near the impedance angle of -90° are denser, while the impedance points in other areas are fewer, it is impossible to distinguish when the impedance measured at the machine end enters the impedance circle from other areas.

[0097] (ii) According to the static boundary impedance Z C , calculate Z every 1° g

[0098] (1) From Table 1, R g0 =R C0 =0.0(Ω),X g0 =X C0 =-57.1(Ω), |Z g0 |=57.1,impedance angle α g0 =0-90=-90(°);

[0099] (2)R g180 =R C90 =0.0(Ω),X g180 =X C90 =17.0(Ω), |Z g180 |=17.0,impedance angle α g180 =180-90=90(°);

[0100] (3) Determine the first constant Z g1 (R g1 ,X g1 ), impedance angle α g1 =-89(°), from Table 1, find Z C23 (R C23 ,X C23 ) and Z C24 (R C24 ,X C24 ), its impedance angle β C23 = -89.05112° and β C24 =-88.91958°, satisfying β C23 ≤α g1 ≤β C24 ,

[0101]

[0102]

[0103]

[0104] (4) Similarly, we can obtain

[0105]

[0106] …

[0107]

[0108] After the calculation is completed, it is stored in the preset storage chip. The static impedance boundary constant Z calculated every 1° g Distribution diagram Figure 3As shown, when the impedance measured at the machine end enters the impedance circle from any area, the static impedance modulus value corresponding to its impedance angle is used as the criterion condition for its entry into the impedance circle.

[0109] (III) Impedance circle criterion action conditions

[0110] Assume that the current measured impedance and modulus are calculated by sampling the voltage and current at the machine end:

[0111] Z op1 =40.56+j32.13Ω

[0112]

[0113]

[0114] Index = INT (38.38) + 90 = 128

[0115] Find the static boundary impedance constant |Z g128 |=21.93968, due to |Z op1 |>|Z g128 |, the current measured impedance has not entered the static impedance circle.

[0116] If the current measured impedance is:

[0117] Z op2 =3.72+j5.34Ω

[0118]

[0119]

[0120] Index = INT (55.14) + 90 = 145

[0121] Find the static boundary impedance constant |Z g145 |=19.012, due to |Z op2 |<|Z g145 |, the current measured impedance enters the static impedance circle, and the impedance circle criterion is activated.

[0122] Example 3

[0123] This embodiment provides a generator demagnetization impedance circle criterion determination device, which is applied to a protection device, including:

[0124] The first calculation unit is used to obtain the impedance parameters and different static stability limit angles of the salient pole generator, input the static stability limit equation of the generator, and calculate the machine-end measurement impedance on the static stability boundary;

[0125] A second calculation unit is used to calculate the impedance modulus of the static boundary impedance at the current impedance angle according to the impedance angle at every set interval angle measured by the machine end on the static boundary, and store the static boundary impedance modulus as a fixed value in a preset storage chip;

[0126] The third calculation unit is used to obtain the current voltage and current data of the machine end and calculate the current measured impedance modulus and impedance angle;

[0127] The comparison and judgment unit is used to compare the current measured impedance modulus with the static boundary impedance modulus corresponding to its impedance angle. If the current measured impedance modulus is smaller than the static boundary impedance modulus corresponding to its impedance angle, the impedance action area is entered.

[0128] Example 4

[0129] This embodiment provides a generator demagnetization impedance circle determination criterion determination device, including a processor and a storage medium;

[0130] The storage medium is used to store instructions;

[0131] The processor is used to operate according to the instruction to execute the steps of the method according to any one of Embodiment 1 or Embodiment 2.

[0132] Example 5

[0133] This embodiment provides a computer-readable storage medium on which a computer program is stored. When the program is executed by a processor, the steps of the method described in any one of Embodiment 1 or Embodiment 2 are implemented.

[0134] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for determining the demagnetization impedance circle of a generator, characterized in that: Used in protective devices, including: Obtain the impedance parameters and different static stability limit angles of the salient pole generator, input the static stability limit equation of the generator, and calculate the measured impedance of the generator end on the static stability boundary; Based on the measured impedance of the machine end on the static boundary, the static boundary impedance modulus under the current impedance angle is calculated at every set interval angle according to the impedance angle, and the static boundary impedance modulus is stored as a fixed value in a preset storage chip; Obtain the current voltage and current data of the machine end, and calculate the current measured impedance modulus and impedance angle; Compare the current measured impedance modulus with the static boundary impedance modulus corresponding to its impedance angle. If the current measured impedance modulus is smaller than the static boundary impedance modulus corresponding to its impedance angle, the impedance protection action area is entered. The machine-side measured impedance Z on the static boundary C Represented as a point Z on the impedance plane C (R C ,X C ), where R C and X C The impedance Z C The resistance and reactance of the resistor are given by: When Z C When in quadrants 1 and 4, When Z C When in quadrants 2 and 3, in: Intermediate parameters X qΣ =X q +X s , X dΣ =X d +X s , X q is the generator quadrature-axis synchronous reactance, X d is the direct-axis synchronous reactance of the generator, X s is the connecting reactance of the generator system, θ j is the limit power angle of the generator under any state of 0% to 100% load, arctg() is the inverse tangent function, sin() is the sine function, and cos() is the cosine function; The limit power angle θ j The value range of θ is 0°~179°, j Taking values ​​every 1°, a series of different static boundary impedances Z are generated C0 (R C0 ,X C0 ), Z C1 (R C1 ,X C1 )…Z C179 (R C179 ,X C179 ), the corresponding impedance angle is β C0 , β C1 …β C179 ; According to the measured impedance on the static boundary, calculate the impedance modulus constant Z with the impedance angle as the index number gx (R gx ,X gx ), the impedance angle is α gx , x = 0 to 359; Calculate the static boundary impedance modulus Z at the current impedance angle every 1° g (R g ,X g ), the static boundary impedance modulus is stored as a constant in a preset storage chip, wherein R g and X g The impedance Z g The specific methods include: Determine the 0th constant Z g0 (R g0 ,X g0 )=Z C0 (R C0 ,X C0 ), impedance angle α g0 =0-90=-90(°); Determine the 180th constant Z g180 (R g180 ,X g180 )=Z C90 (R C90 ,X C90 ), impedance angle α g180 =180-90=90(°); Determine the nth constant Z gn (R gn ,X gn ), impedance angle α gn =n-90(°), n=1~359(n≠180), the known measured impedance Z on the static boundary C In the search box, find Z Cn1 (R Cn1 ,X Cn1 ) and Z Cn2 (R Cn2 ,X Cn2 ), 0<n1≤179, 0<n2≤179, its impedance angle β Cn1 and β Cn2 Satisfy β Cn1 ≤α gn ≤β Cn2 ,but: When α gn = β Cn1 , Z gn (R gn , X gn ) = Z Cn1 (R Cn1 , X Cn1 ) When α gn = β Cn2 , Z gn (R gn , X gn ) = Z Cn2 (R Cn2 , X Cn2 ) When Cn1 <a gn <b Cn2 , Where, tg() is the tangent function; From the above steps, we can get all Z gIndex (R gIndex ,X gIndex ), impedance angle α gIndex = Index-90(°), Index = 0~359, calculate And stored in a preset storage chip.

2. A method for determining a generator demagnetization impedance circle according to claim 1, characterized in that: The method of obtaining the current voltage and current data of the machine end, calculating the current measured impedance modulus and impedance angle, and comparing the current measured impedance modulus with the static boundary impedance modulus corresponding to the impedance angle includes: Calculate the current measured impedance modulus |Z op |, the formula is as follows: Where U φφ Machine-end phase-to-phase voltage, I φφ Machine-end phase-to-phase current; Calculate the impedance angle α op , the formula is as follows: When Z op When in quadrants 1 and 4, When Z op When in quadrants 2 and 3, When α op When the value is not an integer, it can be rounded off to get the index of the current required constant from the impedance angle. op )+90, where INT() means rounding to the nearest integer, and then the modulus value of the current required static stability boundary |Z is obtained. gIndex |, when |Z op |<|Z gIndex |, it enters the impedance circle action area.

3. A generator demagnetization impedance circle judgment device, using the generator demagnetization impedance circle judgment method according to claim 1, characterized in that: include: The first calculation unit is used to obtain the impedance parameters and different static stability limit angles of the salient pole generator, input the static stability limit equation of the generator, and calculate the machine-end measurement impedance on the static stability boundary; A second calculation unit is used to calculate the impedance modulus of the static boundary impedance at the current impedance angle according to the impedance angle at every set interval angle measured by the machine end on the static boundary, and store the static boundary impedance modulus as a fixed value in a preset storage chip; The third calculation unit is used to obtain the current voltage and current data of the machine end and calculate the current measured impedance modulus and impedance angle; The comparison and judgment unit is used to compare the current measured impedance modulus with the static boundary impedance modulus corresponding to its impedance angle. If the current measured impedance modulus is smaller than the static boundary impedance modulus corresponding to its impedance angle, the impedance action area is entered.

4. A generator demagnetization impedance circle judgment device, characterized in that: including processor and storage medium; The storage medium is used to store instructions; The processor is used to operate according to the instructions to execute the steps of the method according to any one of claims 1 to 2.

5. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps of the method according to any one of claims 1 to 2 are implemented.

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