A method for analyzing and setting the unit regulation coefficient of a complex and expanded unit connection

Abstract

The application discloses a kind of complex expansion unit wiring unit group regulating coefficient analysis and setting method, by analyzing the characteristics of complex expansion unit wiring unit;According to the characteristics of unit, the equivalent circuit diagram of complex expansion unit wiring unit is obtained by processing, the virtual parallel point of unit is determined;The additional regulating coefficient of the excitation system of No.1 unit calculated to the high voltage side of three-winding transformer, the total regulating coefficient of No.1 unit is calculated, the preliminary setting method of the additional regulating coefficient of the excitation system of No.1 unit is deduced;The short-circuit voltage of double-winding transformer calculated to the high voltage side of three-winding transformer and the additional regulating coefficient of the excitation system of No.2 unit, the total regulating coefficient of No.2 unit is calculated, the preliminary setting method of the additional regulating coefficient of the excitation system of No.2 unit is deduced;According to the preliminary setting method, the final excitation system additional regulating coefficient of No.1 unit and No.2 unit is set out. Thus, the technical problem of related art without complex expansion unit wiring analysis and setting is solved.

Description

Technical Field

[0001] This invention relates to the field of power system operation and control technology, specifically to a method for analyzing and setting the droop coefficient of a generator unit with complex extended unit wiring. Background Technology

[0002] The voltage droop factor of a generator is typically defined as the rate of change of its reactive current from zero to the rated stator current when the generator's power factor is zero. Correctly setting the generator's voltage droop factor is crucial for the stable operation of parallel generating units and the rational distribution of reactive power among them.

[0003] Common generator paralleling methods include generator-end parallel connection, generator-transformer high-voltage side parallel connection, and expansion unit wiring. The analysis and setting of the voltage droop coefficient differ significantly depending on the generator paralleling method.

[0004] The parallel connection of the high-voltage side of the generator-transformer unit and the connection of the expansion unit both belong to the parallel connection method via the transformer. The voltage droop coefficient of the generator is equal to the sum of the natural droop coefficient, the additional droop coefficient of the excitation system, and the short-circuit voltage of the transformer. In order to maintain the stable operation of the unit, the droop coefficient of each unit at the parallel point is required to be positive. The natural droop coefficient of modern excitation automatic control system is very small and can usually be ignored. Since the short-circuit voltage of the transformer is generally large, when the reactive load of the generator increases, it will cause the voltage drop of the high-voltage bus to be too large, which is not conducive to stable operation. Therefore, it is necessary to reasonably and effectively adjust the additional droop coefficient of the excitation system to compensate for the short-circuit voltage of the transformer and prevent the total droop coefficient at the parallel point from being too large. Existing literature primarily discusses a complex extended-unit wiring configuration in power generation sites. This configuration features two generator sets operating in parallel via a three-winding transformer, which includes high, medium, and low voltage levels. The three-winding transformer can be either a conventional three-winding transformer or a three-winding autotransformer. One generator set is connected to the low-voltage side of the three-winding transformer, while the other is first stepped up by a two-winding transformer before being connected to the medium-voltage side of the three-winding transformer. Due to the complexity of this wiring configuration, analyzing and accurately setting the generator droop coefficient is difficult, and currently, no literature addresses this issue. Therefore, a method for analyzing and setting the droop coefficient of generator sets with complex extended-unit wiring is needed. Summary of the Invention

[0005] This invention provides a method for analyzing and setting the droop coefficient of a generator unit with complex extended unit wiring, thereby at least solving the technical problem that there is no analysis and setting method for complex extended unit wiring in related technologies.

[0006] According to one aspect of the present invention, a method for analyzing and setting the droop coefficient of a generator unit with complex extended unit wiring is provided, comprising:

[0007] The characteristics of the complex extended unit wiring are analyzed. The unit includes two generator sets operating in parallel through a three-winding transformer. Generator No. 1 is connected to the low-voltage side of the three-winding transformer. Generator No. 2 is connected to the medium-voltage side of the three-winding transformer after being stepped up by a two-winding transformer.

[0008] Based on the characteristics of the unit, the equivalent circuit diagram of the unit with complex extended unit wiring is obtained, and the virtual parallel points of the unit are determined;

[0009] Calculate the additional droop coefficient of the excitation system of Unit 1, which is referred to the high voltage side of the three-winding transformer, calculate the total droop coefficient of Unit 1, and derive the preliminary setting method of the additional droop coefficient of the excitation system of Unit 1 based on the calculation results of Unit 1.

[0010] Calculate the short-circuit voltage of the double-winding transformer referred to the high-voltage side of the three-winding transformer and the additional droop coefficient of the excitation system of Unit 2. Calculate the total droop coefficient of Unit 2. Based on the calculation results of Unit 2, derive the preliminary setting method of the additional droop coefficient of the excitation system of Unit 2.

[0011] Based on the calculation results and preliminary tuning method of Unit 1 and Unit 2, the final additional droop coefficient of the excitation system of Unit 1 and Unit 2 is determined.

[0012] Optionally, based on the characteristics of the unit, an equivalent circuit diagram of the unit with complex expanded unit wiring is obtained, specifically including:

[0013] Calculate the short-circuit voltage and reactance of each winding of a three-winding transformer;

[0014] Calculate the reactance of the two-winding transformer and transfer it to the high-voltage side of the three-winding transformer;

[0015] The equivalent circuit diagram of the unit with complex expanded unit wiring is constructed based on the reactance of the calculated three-winding transformer and the reactance of the two-winding transformer after being referred to the high-voltage side of the three-winding transformer.

[0016] Optionally, based on the calculation results of Unit 1, a preliminary setting method for the additional droop coefficient of the excitation system of Unit 1 is derived, specifically including:

[0017] Calculate the additional droop coefficient of the excitation system of Unit 1, which is attributed to the high-voltage side of the three-winding transformer;

[0018] The total droop coefficient of Unit 1 is calculated based on the additional droop coefficient of the excitation system of Unit 1, which is referred to the high-voltage side of the three-winding transformer, and the short-circuit voltage from the terminal of Unit 1 to the virtual parallel point.

[0019] Based on the expression for the total droop coefficient of Unit 1, the setting expression for the additional droop coefficient of the excitation system of Unit 1 is derived, and the additional droop coefficient of the excitation system of Unit 1 is set according to the setting expression.

[0020] Optionally, based on the calculation results of Unit 2, a preliminary setting method for the additional droop coefficient of the excitation system of Unit 2 is derived, specifically including:

[0021] The additional droop coefficient of the excitation system of Unit 2 is attributed to the high-voltage side of the three-winding transformer;

[0022] The total droop coefficient of Unit 2 is calculated by referring the additional droop coefficient of the excitation system of Unit 2 to the high-voltage side of the three-winding transformer and the total short-circuit voltage from the terminal of Unit 2 to the virtual parallel point.

[0023] Based on the expression for the total droop coefficient of Unit 2, the setting expression for the additional droop coefficient of the excitation system of Unit 2 is derived, and the additional droop coefficient of the excitation system of Unit 2 is set according to the setting expression.

[0024] Optionally, the additional droop coefficient of the excitation system of Unit 1 and Unit 2 also needs to meet the following condition: when the generator reactive current increases from zero to the rated reactive current, the generator voltage change is not greater than 0.05 times the rated voltage.

[0025] Optionally, the setting principles for the additional droop coefficient of the final excitation system of Unit 1 and Unit 2 include:

[0026] For virtual parallel points, the per-unit total voltage droop coefficient of each unit should be set according to positive droop, and a smaller value should be taken when the reactive power distribution among the parallel units is stable.

[0027] For virtual parallel points, the per-unit total voltage droop coefficient of Unit 1 is equal to that of Unit 2;

[0028] When the additional droop coefficient of the excitation system is set to a negative value, it is used to compensate for the transformer voltage.

[0029] Optionally, based on the calculation results and preliminary tuning method of Unit 1 and Unit 2, the final additional droop coefficients of the excitation system for Unit 1 and Unit 2 are determined, specifically including:

[0030] Step S51: Set the total droop coefficient δ of Unit 1. G1∑ =0.05. Based on the preliminary setting method for the additional droop coefficient of the excitation system of Unit 1, the additional droop coefficient δ of the excitation system of Unit 1 is calculated. G1 ;

[0031] Step S52: Set the total droop coefficient δ for Unit 2. G2∑ Equal to the total droop coefficient of Unit 1, i.e., δG2∑ =δ G1∑ =0.05, the additional droop coefficient δ of the excitation system of Unit 2 is calculated according to the preliminary setting method of the additional droop coefficient of the excitation system of Unit 2. G2 ;

[0032] Step S53: Check δ based on the additional droop coefficient of the excitation system of Unit 1 and Unit 2, and the conditions that still need to be met. G1 and δ G2 ;

[0033] Step S54: If the verification in step S53 passes, the calculation result is valid, and the calculated δ is used as the reference. G1 and δ G2 The results are used as the additional droop coefficient settings for the excitation systems of Unit 1 and Unit 2, respectively; otherwise, in δ G1∑ ,δ G1∑ Within the range [0.05, 0.1], increase δ in steps of 0.01. G1∑ δ G2∑ If the value is increased by δ, repeat steps S51 and S52. G1∑ δ G2∑ The value of δ up to 0.1 has not yet met the verification requirements. G1 and δ G2 Then δ G1∑ =δ G2∑ δ calculated when = 0.1 G2∑ δ G1 and δ G2 These are the tuning results for the additional droop coefficients of the excitation systems of Unit 1 and Unit 2, respectively.

[0034] Optionally, an additional droop coefficient δ is added to the excitation system of Unit 1. G1∑ The tuning expression is:

[0035]

[0036] In the above formula, δ G1∑ U is the total droop coefficient for Unit 1. T1k3 The short-circuit voltage from the terminal of Unit 1 to the virtual parallel point is δ′. G1 To calculate the per-unit droop factor for Unit 1 on the high-voltage side of the three-winding transformer T1, δ G1 To add a droop factor to the excitation system based on the capacity of Unit 1, S T1N For the rated capacity of T1, S GN1 This is the rated capacity of Unit 1.

[0037] Optionally, the excitation system of Unit 2 may be supplemented with a droop coefficient δ. G2 The tuning expression is:

[0038]

[0039] In the above formula, δ G2∑ To calculate the total droop factor of Unit 2, which is attributed to the high-voltage side of the three-winding transformer, U T1k2 S is the total short-circuit voltage from the terminal of Unit 2 to the virtual parallel point. GN2 For the rated capacity of Unit 2, U T2k The short-circuit voltage provided by the manufacturer of the two-winding transformer T2, S T2N This is the rated capacity of T2.

[0040] Compared with existing technologies, the present invention has the following advantages:

[0041] 1. The present invention provides a method for analyzing and setting the droop coefficient of a generator unit with complex expanded unit wiring. By analyzing the characteristics of the generator unit with complex expanded unit wiring, the method identifies two generator units operating in parallel via a three-winding transformer. Generator unit 1 is connected to the low-voltage side of the three-winding transformer; generator unit 2 is connected to the medium-voltage side of the three-winding transformer after being stepped up by a two-winding transformer. Based on the characteristics of the generator unit, the equivalent circuit diagram of the generator unit with complex expanded unit wiring is obtained, and the virtual parallel connection point of the generator unit is determined. The circuit is then calculated and reduced to the high-voltage side of the three-winding transformer. The additional droop coefficient of the excitation system of Unit 1 was calculated, and the total droop coefficient of Unit 1 was calculated. Based on the calculation results of Unit 1, a preliminary setting method for the additional droop coefficient of the excitation system of Unit 1 was derived. The short-circuit voltage of the double-winding transformer referred to the high-voltage side of the three-winding transformer and the additional droop coefficient of the excitation system of Unit 2 were calculated, and the total droop coefficient of Unit 2 was calculated. Based on the calculation results of Unit 2, a preliminary setting method for the additional droop coefficient of the excitation system of Unit 2 was derived. Based on the calculation results and preliminary setting methods of Units 1 and 2, the final additional droop coefficients of the excitation systems of Units 1 and 2 were set. This solved the technical problem of the lack of analysis and setting for the wiring of complex expansion units in related technologies.

[0042] 2. The present invention provides a method for analyzing and setting the droop coefficient of a complex extended unit wiring unit, and provides a method for calculating the total droop coefficient of two units, analyzing the factors affecting the total droop coefficient of the units. Specifically, the total droop coefficient of Unit 1 is equal to the sum of the short-circuit voltage of the low-voltage winding of the three-winding transformer referred to the high-voltage side and the per-unit droop coefficient of the excitation system of Unit 1; the total droop coefficient of Unit 2 is equal to the sum of the short-circuit voltage of the medium-voltage winding of the three-winding transformer referred to the high-voltage side, the short-circuit voltage of the two-winding transformer, and the per-unit droop coefficient of the excitation system of Unit 2.

[0043] 3. The present invention provides a method for analyzing and setting the droop coefficient of a complex extended unit connection unit. It gives an expression for calculating the additional droop coefficient of the excitation system of Unit 1 and Unit 2 based on the target droop coefficient of the parallel point. According to the expression, it can be seen that only the short-circuit voltage of the transformer, the rated capacity of the unit, and the rated capacity of the transformer are needed to calculate the additional droop coefficient of the excitation system of the two units. Attached Figure Description

[0044] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only one embodiment of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0045] Figure 1 This is a flowchart of a method for analyzing and setting the droop coefficient of a generator unit with complex expanded unit wiring according to an embodiment of the present invention;

[0046] Figure 2 This is a schematic diagram of the structure of a unit with complex expansion unit wiring according to an embodiment of the present invention;

[0047] Figure 3 This is an equivalent circuit diagram of a unit with complex expansion unit wiring according to an embodiment of the present invention. Detailed Implementation

[0048] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0049] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0050] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0051] Example 1

[0052] According to an embodiment of the present invention, an embodiment of a method for analyzing and setting the droop coefficient of a unit with complex extended unit wiring is provided. It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. Furthermore, although a logical order is shown in the flowchart, in some cases, the steps shown or described may be executed in a different order than that shown here.

[0053] like Figure 1 This is a flowchart of a method for analyzing and setting the droop coefficient of a generator unit with complex extended unit wiring according to an embodiment of the present invention, as shown below. Figure 1 As shown, the method includes the following steps:

[0054] Step S1: Analyze the characteristics of the complex extended unit wiring. The unit includes two generator sets operating in parallel through a three-winding transformer. Generator No. 1 of the two generators is connected to the low-voltage side of the three-winding transformer. Generator No. 2 of the two generators is connected to the medium-voltage side of the three-winding transformer after being stepped up by a two-winding transformer.

[0055] Specifically, Figure 2 This is a schematic diagram of the structure of a unit with complex expansion unit wiring according to an embodiment of the present invention. Figure 2 As shown, the characteristics of the complex extended unit wiring include: two generator sets operate in parallel through a three-winding transformer, which has three voltage levels: high, medium, and low; the three-winding transformer can be either a three-winding ordinary transformer or a three-winding autotransformer; Unit 1 is connected to the low-voltage side of the three-winding transformer; Unit 2 is connected to the medium-voltage side of the three-winding transformer after being stepped up by a two-winding transformer.

[0056] Step S2: Based on the characteristics of the unit, obtain the equivalent circuit diagram of the unit with complex expansion unit wiring, and determine the virtual parallel point of the unit.

[0057] Specifically, step S2 includes the following steps:

[0058] Step S21: Calculate the short-circuit voltage and reactance of each winding of the three-winding transformer;

[0059] Specifically, calculating the short-circuit voltage of each winding of a three-winding transformer includes:

[0060] According to the short-circuit voltage U between each pair of windings provided by the manufacturer of the three-winding transformer T1 T1k(1-2) U T1k(1-3) and U T1k(2-3) Find the short-circuit voltage U of each winding. T1k1 U T1k2 and U T1k3 They are respectively:

[0061]

[0062] Due to U T1k(1-2) U T1k(1-3) and U T1k(2-3) All values ​​have already been attributed to the high-voltage side of the transformer. Therefore, U calculated using the above formula is used. T1k1 U T1k2 and U T1k3 The value is already attributed to the high-voltage side of the transformer and does not need to be recalculated.

[0063] The calculation of the reactance of each winding of a three-winding transformer includes:

[0064] Based on the short-circuit voltage U of each winding of the three-winding transformer T1 T1k1 U T1k2 and U T1k3 The nominal reactance of each winding of the three-winding transformer referred to the high-voltage side is obtained as follows:

[0065]

[0066] In the above formula, S T1N For the rated capacity of T1, U T1k1 U T1k2 U T1k3 These are the short-circuit voltages of the high, medium, and low windings of the three-winding transformer T1, respectively, U T1HN This is the rated voltage on the high-voltage side of T1.

[0067] Step S22: Calculate the reactance of the two-winding transformer and transfer it to the high-voltage side of the three-winding transformer.

[0068] As an optional embodiment, step S22 specifically includes:

[0069] According to the short-circuit voltage U provided by the manufacturer of the double-winding transformer T2 T2k The nominal reactance X was calculated.T2 for:

[0070]

[0071] In the above formula, S T2N For the rated capacity of T2, U T2HN This is the rated voltage on the high-voltage side of T2;

[0072] The turns ratio between the high-voltage side and the medium-voltage side of the three-winding transformer T1 is expressed as k. 1-2 The calculation formula is as follows:

[0073]

[0074] In the above formula, U T1HN U is the rated voltage on the high-voltage side of T1. T1MN This refers to the rated voltage on the medium-voltage side of T1;

[0075] The reactance X of the double-winding transformer T2 After being referred to the high-voltage side of the three-winding transformer, it can be expressed as:

[0076]

[0077] Since the high-voltage side of the two-winding transformer T2 is connected to the medium-voltage side of the three-winding transformer T1, i.e., U T2HN =U T1MN Therefore, the above formula can be simplified to:

[0078]

[0079] Step S23: Based on the calculated reactance of the three-winding transformer and the reactance of the two-winding transformer, and the reactance after being transferred to the high-voltage side of the three-winding transformer, construct the equivalent circuit diagram of the unit with complex expanded unit wiring.

[0080] Specifically, ignoring the influence of resistance, the equivalent circuit diagram of the unit with complex expanded unit wiring is obtained as follows: Figure 3 As shown, according to Figure 3 It can be seen that the parallel connection point of the two units in the complex extended unit wiring configuration is not on the high-voltage side of the three-winding transformer, but rather at... Figure 3 Point N in the diagram refers to the virtual parallel point of the two generator units.

[0081] Step S3: Calculate the additional droop coefficient of the excitation system of Unit 1, which is referred to the high-voltage side of the three-winding transformer. Calculate the total droop coefficient of Unit 1. Based on the calculation results of Unit 1, derive the preliminary setting method of the additional droop coefficient of the excitation system of Unit 1.

[0082] Specifically, step S3 includes the following steps:

[0083] Step S31: Calculate the additional droop coefficient of the excitation system of Unit 1, which is referred to the high-voltage side of the three-winding transformer; specifically:

[0084] The additional droop coefficient of the excitation system, based on the capacity of Unit 1 itself, is expressed as δ. G1 The corresponding nominal value additional adjustment coefficient δ can be calculated using the following formula. G1n :

[0085]

[0086] In the above formula, U G1N S is the rated voltage of Unit 1. G1N This is the rated capacity of Unit 1;

[0087] The turns ratio between the high-voltage and low-voltage sides of the three-winding transformer T1 is expressed as k. 1-3 The calculation formula is as follows:

[0088]

[0089] In the above formula, U T1LN This is the rated voltage on the low-voltage side of T1;

[0090] Add the adjustment coefficient δ to the named value of Unit 1. G1n When referred to the high-voltage side of a three-winding transformer, it is expressed as follows:

[0091]

[0092] In the above formula, δ′ G1n An adjustment factor is added to the nominal value of Unit 1 after it is attributed to the T1 high-voltage side;

[0093] Since Unit 1 is connected to the low-voltage side of the three-winding transformer T1, i.e., U G1N =U T1LN Therefore, the above equation simplifies to:

[0094]

[0095] The high-voltage side impedance base value Z of the three-winding transformer T1 T1HB for:

[0096]

[0097] In the above formula, S T1N This is the rated capacity of T1;

[0098] Divide both sides of equation (11) by Z. T1HB The per-unit droop coefficient δ′ of Unit 1, which is attributed to the high-voltage side of the three-winding transformer T1, is obtained. G1 for:

[0099]

[0100] In the above formula, S GN1 This is the rated capacity of Unit 1.

[0101] Step S32: Calculate the total droop coefficient of Unit 1 based on the additional droop coefficient of the excitation system of Unit 1, which is referred to the high-voltage side of the three-winding transformer, and the short-circuit voltage from the terminal of Unit 1 to the virtual parallel point.

[0102] Specifically, step S32 includes:

[0103] The short-circuit voltage (i.e., voltage drop per unit) from terminal 1 to point N is U. T1k3 Ignoring the natural droop coefficient, the total droop coefficient of Unit 1, attributed to the high-voltage side of the three-winding transformer, is:

[0104]

[0105] As can be seen from the above formula, the total droop coefficient of Unit 1 is equal to the sum of the short-circuit voltage of the low-voltage winding of the three-winding transformer referred to the high-voltage side and the per-unit droop coefficient of the excitation system of Unit 1.

[0106] Step S33: Derive the setting expression for the additional droop coefficient of the excitation system of Unit 1 based on the expression for the total droop coefficient of Unit 1, and set the additional droop coefficient of the excitation system of Unit 1 according to the setting expression.

[0107] Specifically, based on equation (13), the setting expression for the additional droop coefficient of the excitation system of Unit 1 can be derived as follows:

[0108]

[0109] In order to maintain the terminal voltage within the allowable range, the additional droop coefficient of the excitation system of Unit 1 also needs to meet the following conditions:

[0110] When the generator reactive current increases from zero to the rated reactive current, the generator voltage change should not exceed 0.05 times the rated voltage.

[0111]

[0112] Step S4: Calculate the short-circuit voltage of the double-winding transformer referred to the high-voltage side of the three-winding transformer and the additional droop coefficient of the excitation system of Unit 2. Calculate the total droop coefficient of Unit 2. Based on the calculation results of Unit 2, derive the preliminary setting method of the additional droop coefficient of the excitation system of Unit 2.

[0113] Specifically, step S4 includes the following steps:

[0114] Step S41: The additional droop coefficient of the excitation system of Unit 2 is transferred to the high-voltage side of the three-winding transformer.

[0115] Specifically, divide both sides of equation (6) by Z simultaneously. T1HB The short-circuit voltage U of the two-winding transformer T2, which is referred to the high-voltage side of the three-winding transformer T1, is obtained. T ′ 2k for:

[0116]

[0117] In the above formula, Z T1HB This is the reference value for the reactance on the high-voltage side of T1.

[0118] Step S42: Calculate the additional droop coefficient of the excitation system of Unit 2 and transfer it to the high-voltage side of the three-winding transformer.

[0119] Specifically, the additional droop coefficient of the excitation system, based on the capacity of Unit 2 itself, is expressed as δ. G2 (per unit value), then the corresponding nominal value additional adjustment coefficient δ can be calculated using the following formula. G2n .

[0120]

[0121] In the above formula, U GN2 The rated voltage of Unit 2, S GN2 This is the rated capacity of Unit 2;

[0122] Let the turns ratio between the high-voltage and low-voltage sides of the two-winding transformer T2 be expressed as k2, and its calculation formula is as follows:

[0123]

[0124] In the above formula, U T2LN This is the rated voltage of the low-voltage side of T2;

[0125] First, add the adjustment coefficient δ to the named value of Unit 2. G2n Referred to the high-voltage side of the two-winding transformer T2, we get:

[0126]

[0127] Because Unit 2 is connected to the low-voltage side of the double-winding transformer T2, i.e., U GN2 =U T2LN Therefore, equation (19) can be simplified to:

[0128]

[0129] Further δ′ G ′ 2nAfter being referred to the high-voltage side of the three-winding transformer T1, it can be expressed as:

[0130]

[0131] Since the high-voltage side of the two-winding transformer T2 is connected to the medium-voltage side of the three-winding transformer T1, i.e., U T2HN =U T1MN Therefore, equation (21) can be simplified to:

[0132]

[0133] Divide both sides of the above equation by Z. T1HB The per-unit value of the excitation system of Unit 2, attributed to the high-voltage side of the three-winding transformer T1, with the additional droop factor is obtained as follows:

[0134]

[0135] Step S43: Combining step S42 and the total short-circuit voltage from the terminal of Unit 2 to the virtual parallel point (i.e., point N), calculate the total droop coefficient of Unit 2.

[0136] Specifically, the total short-circuit voltage U from the terminal of Unit 2 to point N. ∑Tk2 For U k2 with U k ′, that is:

[0137]

[0138] Ignoring the natural droop factor, the total droop factor of Unit 2, referred to the high-voltage side of the three-winding transformer, is U. ∑Tk2 With δ′ G2 The sum is:

[0139]

[0140] As can be seen from the above formula, the total droop coefficient of Unit 2 is equal to the sum of the short-circuit voltage of the medium-voltage winding of the three-winding transformer, the short-circuit voltage of the two-winding transformer, and the per-unit droop coefficient of the excitation system of Unit 2, which are referred to the high-voltage side.

[0141] Step S44: Derive the setting expression for the additional droop coefficient of the excitation system of Unit 2 based on the expression for the total droop coefficient of Unit 2, and set the additional droop coefficient of the excitation system of Unit 2 according to the setting expression.

[0142] Specifically, the excitation system of Unit 2 has an additional droop coefficient δ. G2 The tuning expression is:

[0143]

[0144] In the above formula, δG2∑ To calculate the total droop factor of Unit 2, which is attributed to the high-voltage side of the three-winding transformer, U T1k2 S is the total short-circuit voltage from the terminal of Unit 2 to the virtual parallel point. GN2 S is the rated capacity of Unit 2. T1N For the rated capacity of T1, U T2k S is the short-circuit voltage of T2. T2N This is the rated capacity of T2.

[0145] To maintain the generator terminal voltage within the allowable range, the additional droop factor of the No. 2 excitation system must also meet the following condition: when the generator reactive current increases from zero to the rated reactive current, the generator voltage change should not exceed 0.05 times the rated voltage, that is:

[0146]

[0147] Step S5: Based on the calculation results and preliminary setting method of Unit 1 and Unit 2, determine the final additional droop coefficient of the excitation system of Unit 1 and Unit 2.

[0148] To ensure proper allocation of reactive power, the additional droop factor setting principle for the excitation systems of Unit 1 and Unit 2 is as follows:

[0149] ① For virtual parallel points, the per-unit total voltage droop coefficient of each unit should be set according to positive droop (0.05~0.1), and a smaller value should be taken when the reactive power distribution among the parallel units is stable;

[0150] ② For virtual parallel points, the per-unit total voltage droop coefficient of Unit 1 is equal to that of Unit 2, i.e., δ G1 =δ G2 ;

[0151] ③ When the additional droop coefficient of the excitation system is set to a negative value, it is used to compensate for the transformer voltage.

[0152] Therefore, based on the calculation results and preliminary tuning method of Unit 1 and Unit 2, the final additional droop coefficient of the excitation system of Unit 1 and Unit 2 is determined, specifically including the following steps:

[0153] Step S51: Set the total droop coefficient δ of Unit 1. G1∑ =0.05. Based on the preliminary setting method for the additional droop coefficient of the excitation system of Unit 1 (Equation (14)), the additional droop coefficient δ of the excitation system of Unit 1 is calculated. G1 ;

[0154] Step S52: Set the total droop coefficient δ for Unit 2. G2∑ Equal to the total droop coefficient of Unit 1, i.e., δ G2∑ =δ G1∑=0.05, and the additional droop coefficient δ of the excitation system of Unit 2 is calculated according to the preliminary setting method of the additional droop coefficient of the excitation system of Unit 2 (Equation (26)). G2 ;

[0155] Step S53: Check δ based on the additional droop coefficient of the excitation system of Unit 1 and Unit 2, which also needs to meet the conditions (Equations (15) and (27)). G1 and δ G2 .

[0156] Step S54: If the verification in step S53 passes, the calculation result is valid, and the calculated δ is used as the reference. G1 and δ G2 The results are used as the additional droop coefficient settings for the excitation systems of Unit 1 and Unit 2, respectively; otherwise, in δ G1∑ ,δ G1∑ Within the range [0.05, 0.1], increase δ in steps of 0.01. G1∑ δ G2∑ If the value is increased by δ, repeat steps S51 and S52. G1∑ δ G2∑ The value of δ up to 0.1 has not yet met the verification requirements. G1 and δ G2 Then δ G1∑ =δ G2∑ δ calculated when = 0.1 G2∑ δ G1 and δ G2 These are the tuning results for the additional droop coefficients of the excitation systems of Unit 1 and Unit 2, respectively.

[0157] Next, one embodiment of the unit droop coefficient analysis and setting method for a complex expanded unit wiring in this embodiment will be described in detail to enable those skilled in the art to better understand the present invention:

[0158] A hydropower plant has two generating units connected to the auxiliary power plant. Figure 1 The wiring configuration shown indicates parallel operation. The parameters of the generating units and transformers are shown in Tables 1 and 2, respectively.

[0159] Table 1 Unit Parameters

[0160]

[0161] Table 2 Transformer Parameters

[0162]

[0163] Based on the above-mentioned principles for setting the additional droop coefficient of the excitation system for Unit 1 and Unit 2, the specific setting steps are as follows:

[0164] Step S51, take δ G1∑ =0.05, and the additional droop coefficient δ of the excitation system of Unit 1 is calculated according to formula (14). G1 for:

[0165]

[0166] Step S52, take δ G2∑ =δ G1∑ =0.05, and the additional droop coefficient δ of the excitation system of Unit 2 is calculated according to formula (26). G2 for:

[0167]

[0168] Step S53: Verify δ using equations (15) and (27). G1 and δ G2 .

[0169] According to equations (15) and (27), the tuned δ G1 and δ G2 The following criteria must be met respectively:

[0170]

[0171]

[0172] Therefore, the additional droop coefficient δ of the excitation system calculated in sub-steps S51 and S52 G1 and δ G2 All meet the verification requirements.

[0173] Step S54 and sub-step 3 have passed the verification, and the calculation results are valid. Therefore, the calculated δ is used. G1 and δ G2 The results are used as the adjustment results of the additional droop coefficients for the excitation systems of Unit 1 and Unit 2, respectively.

[0174] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for analyzing and setting the droop coefficient of a generator unit with complex extended unit wiring, characterized in that, include: The characteristics of the complex extended unit wiring are analyzed. The unit includes two generator sets operating in parallel through a three-winding transformer. Generator No. 1 is connected to the low-voltage side of the three-winding transformer. Generator No. 2 is connected to the medium-voltage side of the three-winding transformer after being stepped up by a two-winding transformer. Based on the characteristics of the unit, the equivalent circuit diagram of the unit with complex expanded unit wiring is obtained, and the virtual parallel points of the unit are determined; Calculate the additional droop coefficient of the excitation system of Unit 1, which is referred to the high voltage side of the three-winding transformer, calculate the total droop coefficient of Unit 1, and derive the preliminary setting method of the additional droop coefficient of the excitation system of Unit 1 based on the calculation results of Unit 1. Calculate the short-circuit voltage of the double-winding transformer referred to the high-voltage side of the three-winding transformer and the additional droop coefficient of the excitation system of Unit 2. Calculate the total droop coefficient of Unit 2. Based on the calculation results of Unit 2, derive the preliminary setting method of the additional droop coefficient of the excitation system of Unit 2. Based on the calculation results and preliminary tuning method of Unit 1 and Unit 2, the final additional droop coefficient of the excitation system of Unit 1 and Unit 2 is determined.

2. The method for analyzing and setting the droop coefficient of a generator unit with complex expanded unit wiring as described in claim 1, characterized in that, Based on the characteristics of the unit, the equivalent circuit diagram of the unit with complex expanded unit wiring is obtained, specifically including: Calculate the short-circuit voltage and reactance of each winding of a three-winding transformer; Calculate the reactance of the two-winding transformer and transfer it to the high-voltage side of the three-winding transformer; The equivalent circuit diagram of the unit with complex expanded unit wiring is constructed based on the reactance of the calculated three-winding transformer and the reactance of the two-winding transformer after being referred to the high-voltage side of the three-winding transformer.

3. The method for analyzing and setting the droop coefficient of a generator unit with complex expanded unit wiring as described in claim 1, characterized in that, Based on the calculation results of Unit 1, a preliminary tuning method for the additional droop coefficient of the excitation system of Unit 1 is derived, specifically including: Calculate the additional droop coefficient of the excitation system of Unit 1, which is attributed to the high-voltage side of the three-winding transformer; The total droop coefficient of Unit 1 is calculated based on the additional droop coefficient of the excitation system of Unit 1, which is referred to the high-voltage side of the three-winding transformer, and the short-circuit voltage from the terminal of Unit 1 to the virtual parallel point. Based on the expression for the total droop coefficient of Unit 1, the setting expression for the additional droop coefficient of the excitation system of Unit 1 is derived, and the additional droop coefficient of the excitation system of Unit 1 is set according to the setting expression.

4. The method for analyzing and setting the droop coefficient of a generator unit with complex expanded unit wiring as described in claim 1, characterized in that, Based on the calculation results of Unit 2, a preliminary tuning method for the additional droop coefficient of the excitation system of Unit 2 is derived, specifically including: The additional droop coefficient of the excitation system of Unit 2 is attributed to the high-voltage side of the three-winding transformer; The total droop coefficient of Unit 2 is calculated by referring the additional droop coefficient of the excitation system of Unit 2 to the high-voltage side of the three-winding transformer and the total short-circuit voltage from the terminal of Unit 2 to the virtual parallel point. Based on the expression for the total droop coefficient of Unit 2, the setting expression for the additional droop coefficient of the excitation system of Unit 2 is derived, and the additional droop coefficient of the excitation system of Unit 2 is set according to the setting expression.

5. The method for analyzing and setting the droop coefficient of a generator unit with complex expanded unit wiring according to claim 3 or 4, characterized in that, The additional droop coefficient of the excitation system of Unit 1 and Unit 2 also needs to meet the following condition: when the generator reactive current increases from zero to the rated reactive current, the generator voltage change is not greater than 0.05 times the rated voltage.

6. The method for analyzing and setting the droop coefficient of a generator unit with complex expanded unit wiring as described in claim 1, characterized in that, The setting principles for the additional droop coefficient of the final excitation system of Unit 1 and Unit 2 include: For virtual parallel points, the per-unit total voltage droop coefficient of each unit should be set according to positive droop, and a smaller value should be taken when the reactive power distribution among the parallel units is stable. For virtual parallel points, the per-unit total voltage droop coefficient of Unit 1 is equal to that of Unit 2; When the additional droop coefficient of the excitation system is set to a negative value, it is used to compensate for the transformer voltage.

7. The method for analyzing and setting the droop coefficient of a generator unit with complex expanded unit wiring as described in claim 1, characterized in that, Based on the calculation results and preliminary tuning method of Unit 1 and Unit 2, the final additional droop coefficients of the excitation system for Units 1 and 2 are determined, specifically including: Step S51: Set the total droop coefficient for Unit 1. Based on the preliminary setting method for the additional droop coefficient of the excitation system of Unit 1, the additional droop coefficient of the excitation system of Unit 1 was calculated. ; Step S52: Set the total droop coefficient for Unit 2. Equal to the total droop coefficient of Unit 1, i.e. The additional droop coefficient of the excitation system of Unit 2 was calculated based on the preliminary setting method of the additional droop coefficient of the excitation system of Unit 2. ; Step S53: Verify the additional droop coefficients of the excitation systems of Unit 1 and Unit 2 according to the conditions that still need to be met. and ; Step S54: If the verification in step S53 passes, the calculation result is valid. and The results are used as the setting results for the additional droop coefficient of the excitation system of Unit 1 and Unit 2, respectively; otherwise, in Within the range, increase in steps of 0.

01. , If the value is increased, repeat steps S51 and S52. , The value up to 0.1 has not yet met the verification requirements. and Then Time calculation of and These are the tuning results for the additional droop coefficients of the excitation systems of Unit 1 and Unit 2, respectively.

8. The method for analyzing and setting the droop coefficient of a generator unit with complex expanded unit wiring as described in claim 3, characterized in that, Total droop coefficient of Unit 1 The tuning expression is: In the above formula, This is the total droop coefficient for Unit 1. This refers to the short-circuit voltage from the terminal of Unit 1 to the virtual parallel point. To be attributed to a three-winding transformer The per-unit droop coefficient of Unit 1 on the high-voltage side. An additional droop coefficient is added to the excitation system based on the capacity of Unit 1 itself. for Rated capacity, This is the rated capacity of Unit 1.

9. The method for analyzing and setting the droop coefficient of a generator unit with complex extended unit wiring as described in claim 4, characterized in that, Additional droop coefficient for excitation system of Unit 2 The tuning expression is: In the above formula, To calculate the total droop factor of Unit 2, which is attributed to the high-voltage side of the three-winding transformer, This is the total short-circuit voltage from the terminal of Unit 2 to the virtual parallel point. This is the rated capacity of Unit 2. for Rated capacity, A two-winding transformer The short-circuit voltage provided by the manufacturer. for Rated capacity.

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