CN111342717A - Method for obtaining low excitation limit curve of steam turbine generator - Google Patents

Method for obtaining low excitation limit curve of steam turbine generator Download PDF

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CN111342717A
CN111342717A CN202010229839.8A CN202010229839A CN111342717A CN 111342717 A CN111342717 A CN 111342717A CN 202010229839 A CN202010229839 A CN 202010229839A CN 111342717 A CN111342717 A CN 111342717A
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turbine generator
regular hexagon
circle
static stability
stability margin
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CN111342717B (en
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张明江
祖光鑫
武国良
陈晓光
穆兴华
崔佳鹏
关万琳
董一凡
师广志
荣爽
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State Grid Heilongjiang Electric Power Co Ltd Electric Power Research Institute
State Grid Corp of China SGCC
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State Grid Heilongjiang Electric Power Co Ltd Electric Power Research Institute
State Grid Corp of China SGCC
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    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02PCONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P9/00Arrangements for controlling electric generators for the purpose of obtaining a desired output
    • H02P9/14Arrangements for controlling electric generators for the purpose of obtaining a desired output by variation of field
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02PCONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P2101/00Special adaptation of control arrangements for generators
    • H02P2101/20Special adaptation of control arrangements for generators for steam-driven turbines

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  • Power Engineering (AREA)
  • Control Of Eletrric Generators (AREA)

Abstract

A method for obtaining a low excitation limit curve of a steam turbine generator belongs to the field of setting of the low excitation limit curve of an excitation regulator of the steam turbine generator. The problem that the existing low excitation limit setting curve cannot realize stable operation of a unit and a system and can exert the unit phase-in operation capability to a greater extent is solved. Firstly, according to the circle center coordinates (0, a), the radius r and the K of the turbine generator static stable impedance circlekAnd under an impedance coordinate system, obtaining a static stability margin impedance circle of the steam turbine generator, drawing double circumscribed regular hexagons of the static stability margin impedance circle of the steam turbine generator, and obtaining a low excitation limit curve of the steam turbine generator according to a tangent point between the static stability margin impedance circle of the steam turbine generator and the double circumscribed regular hexagons and an intersection point between the double circumscribed regular hexagons. The method is mainly used for ensuring the case stable operation of the unit and the system and exerting the unit phase advance operation capability to a greater extent.

Description

Method for obtaining low excitation limit curve of steam turbine generator
Technical Field
The invention belongs to the field of setting of a low excitation limit curve of an excitation regulator of a steam turbine generator, and particularly relates to a method for obtaining the low excitation limit curve of the steam turbine generator based on a statically stable impedance circle double circumscribed regular hexagon.
Background
The low excitation limiting characteristic of the excitation system is determined by the system static stability limit and the heating limiting condition of the end part of the generator, and the change of the end voltage of the generator is taken into account. The low excitation limit, also known as the underexcitation limit or the P/Q limit, is a curve of the minimum reactive power allowed by the generator set in the low excitation limiter versus the active power.
The protection of the generator is provided with a field loss protection which reflects the disappearance or reduction of the exciting current in an excitation system.
When the generator is subjected to a phase-entering test, low excitation limit and loss-of-excitation protection actions can be caused in the process of manual demagnetization. Whether the matching relation between the low excitation limit of the excitation regulator and the loss-of-excitation protection of the generator is correct or not is particularly important, and the method is also an important content of network source coordination.
According to the relevant standard, the action relation between the low excitation limit and the loss excitation protection of the generator is to ensure that the low excitation limit protection acts firstly and then the loss excitation protection acts, and the mutual matching of the low excitation limit protection and the loss excitation protection on a fixed value is a precondition for meeting the action sequence.
The existing low excitation limit setting method starts from the perspective of ensuring the safe and stable operation of a unit, but the method does not give full play to the phase advance operation capability of the unit far away, and cannot simultaneously ensure the stable operation of the unit and a system and give full play to the phase advance operation capability of the unit to a greater extent, so that the difficulties are urgently needed to be solved.
Disclosure of Invention
The invention provides a method for obtaining a low excitation limit curve of a steam turbine generator, aiming at solving the problem that the existing low excitation limit setting curve can not realize stable operation of a unit and a system, and can also play the unit phase-in operation capability to a greater extent.
A method for obtaining a low excitation limit curve of a steam turbine generator comprises the following steps:
acquiring the center coordinates (0, a) and the radius r of a statically stable impedance circle of the turbonator in an impedance coordinate system according to data information of the turbonator in a statically stable state; wherein the abscissa of the impedance coordinate system represents resistance and the ordinate represents reactance; a is the longitudinal coordinate of the circle center of the static stable impedance circle of the turbonator;
step two, according to the coordinates (0, a) of the circle center, the radius r and the radius KkDrawing a turbine generator static stability margin impedance circle under an impedance coordinate system, wherein the turbine generator static stability impedance circle and the turbine generator static stability margin impedance circle are concentric circles;
Kkrepresenting the coefficients;
drawing a No. 1 externally tangent regular hexagon of the turbine generator static stability margin impedance circle according to the turbine generator static stability margin impedance circle, wherein two opposite vertexes of the No. 1 externally tangent regular hexagon are positioned on a longitudinal axis of an impedance coordinate system, and obtaining a No. 1 externally tangent regular hexagon curve equation according to the relation between the turbine generator static stability margin impedance circle and the No. 1 externally tangent regular hexagon;
step four, clockwise rotating the No. 1 externally tangent regular hexagon by 30 degrees so as to obtain the No. 2 externally tangent regular hexagon of the static stability margin impedance circle of the turbonator, and obtaining a No. 2 externally tangent regular hexagon curve equation according to the relationship among the static stability margin impedance circle of the turbonator, the No. 1 externally tangent regular hexagon and the No. 2 externally tangent regular hexagon;
step five, according to the coordinates (0, a) of the circle center, the radius r and the radius KkObtaining a curve equation of the static stability margin impedance circle of the steam turbine generator, and obtaining all tangent point coordinates of the static stability margin impedance circle of the steam turbine generator and the No. 1 circumscribed regular hexagon according to the static stability margin impedance circle equation of the steam turbine generator and the No. 1 circumscribed regular hexagon curve equation; obtaining all intersection point coordinates of the No. 1 externally tangent regular hexagon and the No. 2 externally tangent regular hexagon according to the No. 1 externally tangent regular hexagon curve equation and the No. 2 externally tangent regular hexagon curve equation; obtaining all tangent point coordinates of the static stability margin impedance circle of the steam turbine generator and the number 2 external tangent regular hexagon according to the static stability margin impedance circle equation of the steam turbine generator and the number 2 external tangent regular hexagon curve equation;
and step six, sequentially connecting all tangent points of the turbine generator static stability margin impedance circle and the No. 1 circumscribed regular hexagon, all intersection points of the No. 1 circumscribed regular hexagon and the No. 2 circumscribed regular hexagon, and all tangent points of the turbine generator static stability margin impedance circle and the No. 2 circumscribed regular hexagon, so as to obtain a dodecagon which is circumscribed on the turbine generator static stability margin impedance circle under an impedance coordinate system, wherein the dodecagon is a turbine generator low excitation limit curve, and thus, the acquisition of the turbine generator low excitation limit curve is completed.
Preferably, in the step one, the specific process of obtaining the circle center coordinates (0, a) and the radius r of the turbine generator statically stable impedance circle in the impedance coordinate system according to the data information of the turbine generator statically stable state is as follows:
the method comprises the steps of acquiring data information of the turbonator in a static stable state, wherein the data information comprises Xcon、Xd、UN、SN、naAnd nv(ii) a Wherein the content of the first and second substances,
Xconthe equivalent reactance between the generator and the system;
Xdis a generator synchronous reactance;
UNrated voltage for the generator;
SNrated apparent power for the generator;
nathe transformation ratio of a current transformer at the generator terminal is set;
nvthe transformation ratio of a generator terminal voltage transformer is obtained;
step two, under an impedance coordinate system, according to Xcon、Xd、UN、SN、naAnd nvObtaining a and a radius r, thereby obtaining the circle center coordinates (0, a) and the radius r of the turbine generator steady impedance circle; wherein the content of the first and second substances,
Figure BDA0002428954260000031
Figure BDA0002428954260000032
preferably, in step two, the radius r and the radius K are determined according to the coordinates (0, a) of the center of the circlekUnder an impedance coordinate system, the specific process of drawing the turbine generator static stability margin impedance circle is as follows:
step two, a, because the turbine generator static stability impedance circle and the turbine generator static stability margin impedance circle are concentric circlesYuA, so as to obtain the center coordinates (0, a) of the turbine generator static margin impedance circleYu);
Wherein, aYuThe vertical coordinate of the circle center of the turbine generator static stability margin impedance circle;
step two, enabling the radius r of the turbine generator static stability margin impedance circleYu=KkR, from the center coordinates (0, a)Yu) And radius rYuAnd drawing the turbine generator static stability margin impedance circle under the impedance coordinate system, thereby completing the drawing of the turbine generator static stability margin impedance circle.
Preferably, 1.05. ltoreq. Kk≤1.2。
Preferably, in the fifth step, the number of the turbine generator static stability margin impedance circles and all the tangent points of the No. 1 circumscribed regular hexagon are 6, and the tangent points are respectively tangent points O3、O7、O11、O15、O19And O23And the coordinates of each tangent point are respectively O3(Kk·r·sin30°,Kk·r·cos30°+a)、O7(Kk·r,a)、O11(Kk·r·sin30°,-Kk·r·cos30°+a)、O15(-Kk·r·sin30°,-Kk·r·cos30°+a)、O19(-KkR, a) and O23(-Kk·r·sin30°,Kk·r·cos30°+a);
The number of the tangent points of the static stability margin impedance circle of the turbonator and the No. 2 circumscribed regular hexagon is 6, and the tangent points are respectively tangent points O1、O5、O9、O13、O17And O21And the coordinate of each tangent point is O1(0,Kk·r-r+Xc)、O5(Kk·r·cos30°,Kk·r·sin30°+a)、O9(Kk·r·cos30°,-Kk·r·sin30°+a)、O13(0,-(Kk·r-r)+Xb)、O17(-Kk·r·cos30°,-KkR sin30 ° + a) and O21(-Kk·r·cos30°,Kk·r·sin30°+a);
The number of the intersection points of the No. 1 externally tangent regular hexagon and the No. 2 externally tangent regular hexagon is 12, and the number is O2、O4、O6、O8、O10、O12、O14、、O16、O18、O20、O22And O24And the coordinates of each tangent point are respectively
Figure BDA0002428954260000041
Figure BDA0002428954260000042
O6(Kk·r,Kk·r·tan15°+a)、O8(Kk·r,-Kk·r·tan15°+a)、
Figure BDA0002428954260000043
Figure BDA0002428954260000044
-(Kk·r-r)+Xb)、
Figure BDA0002428954260000045
Figure BDA0002428954260000046
O18(-Kk·r,-Kk·r·tan15°+a)、O20(-Kk·r,Kk·r·tan15°+a)、
Figure BDA0002428954260000047
And
Figure BDA0002428954260000048
wherein, XcAnd XbAre all intermediate variables, and
Figure BDA0002428954260000049
Figure BDA00024289542600000410
Xconthe equivalent reactance between the generator and the system;
Xdis a generator synchronous reactance;
UNrated voltage for the generator;
SNrated apparent power for the generator;
nathe transformation ratio of a current transformer at the generator terminal is set;
nvthe transformation ratio of the generator terminal voltage transformer is obtained.
The method has the advantages that the low excitation limiting curve of the steam turbine generator is obtained based on the statically stable impedance circle double-circumscribed regular hexagon, and the obtained method for setting the low excitation limiting curve of the steam turbine generator can ensure the case stable operation of a unit and a system and can also give play to the unit phase-advancing operation capability to the maximum extent.
The low excitation limiting curve determined by the method is more accurate, the method is visual and clear, the setting is simple, and the loss of excitation protection can be effectively prevented from being prior to the low excitation limiting action.
Drawings
FIG. 1 is a graph of a turbine generator quiet stable impedance circle in an impedance coordinate system;
FIG. 2 is a diagram of a relative relationship between a turbine generator static stability impedance circle, a turbine generator static stability margin impedance circle, a number 1 circumscribed regular hexagon, a number 2 circumscribed regular hexagon and a turbine generator low excitation limit curve in an impedance coordinate system.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.
The invention is further described with reference to the following drawings and specific examples, which are not intended to be limiting.
Referring to fig. 1 and fig. 2, the embodiment is described, and a method for obtaining a low excitation limit curve of a steam turbine generator according to the embodiment includes the following steps:
acquiring the center coordinates (0, a) and the radius r of a statically stable impedance circle of the turbonator in an impedance coordinate system according to data information of the turbonator in a statically stable state; wherein the abscissa of the impedance coordinate system represents resistance and the ordinate represents reactance; a is the longitudinal coordinate of the circle center of the static stable impedance circle of the turbonator;
step two, according to the center coordinates (0, a), the radius r andKkdrawing a turbine generator static stability margin impedance circle under an impedance coordinate system, wherein the turbine generator static stability impedance circle and the turbine generator static stability margin impedance circle are concentric circles;
Kkrepresenting the coefficients;
drawing a No. 1 externally tangent regular hexagon of the turbine generator static stability margin impedance circle according to the turbine generator static stability margin impedance circle, wherein two opposite vertexes of the No. 1 externally tangent regular hexagon are positioned on a longitudinal axis of an impedance coordinate system, and obtaining a No. 1 externally tangent regular hexagon curve equation according to the relation between the turbine generator static stability margin impedance circle and the No. 1 externally tangent regular hexagon;
step four, clockwise rotating the No. 1 externally tangent regular hexagon by 30 degrees so as to obtain the No. 2 externally tangent regular hexagon of the static stability margin impedance circle of the turbonator, and obtaining a No. 2 externally tangent regular hexagon curve equation according to the relationship among the static stability margin impedance circle of the turbonator, the No. 1 externally tangent regular hexagon and the No. 2 externally tangent regular hexagon;
step five, according to the coordinates (0, a) of the circle center, the radius r and the radius KkObtaining a curve equation of the static stability margin impedance circle of the steam turbine generator, and obtaining all tangent point coordinates of the static stability margin impedance circle of the steam turbine generator and the No. 1 circumscribed regular hexagon according to the static stability margin impedance circle equation of the steam turbine generator and the No. 1 circumscribed regular hexagon curve equation; obtaining all intersection point coordinates of the No. 1 externally tangent regular hexagon and the No. 2 externally tangent regular hexagon according to the No. 1 externally tangent regular hexagon curve equation and the No. 2 externally tangent regular hexagon curve equation; obtaining all tangent point coordinates of the static stability margin impedance circle of the steam turbine generator and the number 2 external tangent regular hexagon according to the static stability margin impedance circle equation of the steam turbine generator and the number 2 external tangent regular hexagon curve equation;
and step six, sequentially connecting all tangent points of the turbine generator static stability margin impedance circle and the No. 1 circumscribed regular hexagon, all intersection points of the No. 1 circumscribed regular hexagon and the No. 2 circumscribed regular hexagon, and all tangent points of the turbine generator static stability margin impedance circle and the No. 2 circumscribed regular hexagon, so as to obtain a dodecagon which is circumscribed on the turbine generator static stability margin impedance circle under an impedance coordinate system, wherein the dodecagon is a turbine generator low excitation limit curve, and thus, the acquisition of the turbine generator low excitation limit curve is completed.
In this embodiment, the turbine generator steady impedance circle, the turbine generator steady margin impedance circle, the number 1 and 2 circumscribed regular hexagons of the turbine generator steady margin impedance circle and the turbine generator low excitation limit curve are concentric, the turbine generator low excitation limit curve wraps the turbine generator steady impedance circle and the turbine generator steady margin impedance circle on the outermost layer, and the distance between the steady impedance circle and the circumscribed regular hexagons of the steady margin impedance circle passes through KkAnd (5) controlling.
The invention obtains the low excitation limit curve of the turbonator based on the statically stable impedance circle double circumscribed regular hexagon, and the obtained method for setting the low excitation limit curve of the turbonator can not only ensure the case stable operation of a unit and a system, but also play the unit phase-in operation capability to a greater extent.
The low excitation limiting curve determined by the method is more accurate, the method is visual and clear, the setting is simple, and the loss of excitation protection can be effectively prevented from being prior to the low excitation limiting action.
The method has the advantages of simple process for obtaining the low excitation limiting curve of the turbonator, intuition and clarity, and capability of effectively preventing the loss of excitation protection from being prior to the low excitation limiting action. In the specific application process, the terminal measured impedance is calculated by detecting the terminal voltage and current of the steam turbine generator, whether the terminal measured impedance enters the circumscribed regular hexagon of the static stability margin impedance circle of the steam turbine generator is used as a judgment basis, when the terminal measured impedance enters the circumscribed regular hexagon, the low excitation limiting action is performed, the increase of the phase advance depth is prevented, and the problem of mismatching of the demagnetization protection and the low excitation limiting curve is avoided, so that the demagnetization is caused and the machine is stopped.
Further, in the first step, according to the data information of the steam turbine generator in the static stable state, in the impedance coordinate system, the specific process of obtaining the circle center coordinates (0, a) and the radius r of the static stable impedance circle of the steam turbine generator is as follows:
the method comprises the steps of acquiring data information of the turbonator in a static stable state, wherein the data information comprises Xcon、Xd、UN、SN、naAnd nv(ii) a Wherein the content of the first and second substances,
Xconthe equivalent reactance between the generator and the system;
Xdis a generator synchronous reactance;
UNrated voltage for the generator;
SNrated apparent power for the generator;
nathe transformation ratio of a current transformer at the generator terminal is set;
nvthe transformation ratio of a generator terminal voltage transformer is obtained;
step two, under an impedance coordinate system, according to Xcon、Xd、UN、SN、naAnd nvObtaining a and a radius r, thereby obtaining the circle center coordinates (0, a) and the radius r of the turbine generator steady impedance circle; wherein the content of the first and second substances,
Figure BDA0002428954260000071
Figure BDA0002428954260000072
furthermore, in the second step, according to the coordinates (0, a) of the circle center, the radius r and the radius KkUnder an impedance coordinate system, the specific process of drawing the turbine generator static stability margin impedance circle is as follows:
step two, a, because the turbine generator static stability impedance circle and the turbine generator static stability margin impedance circle are concentric circlesYuA, so as to obtain the center coordinates (0, a) of the turbine generator static margin impedance circleYu);
Wherein, aYuThe vertical coordinate of the circle center of the turbine generator static stability margin impedance circle;
step two, enabling the radius r of the turbine generator static stability margin impedance circleYu=KkR, from the center coordinates (0, a)Yu) And radius rYuAnd drawing the turbine generator static stability margin impedance circle under the impedance coordinate system, thereby completing the drawing of the turbine generator static stability margin impedance circle.
Further, 1.05. ltoreq.Kk≤1.2。
Furthermore, in the fifth step, the number of all the tangent points of the static stability margin impedance circle of the steam turbine generator and the No. 1 circumscribed regular hexagon is 6, and the tangent points are respectively the tangent point O3、O7、O11、O15、O19And O23And the coordinates of each tangent point are respectively O3(Kk·r·sin30°,Kk·r·cos30°+a)、O7(Kk·r,a)、O11(Kk·r·sin30°,-Kk·r·cos30°+a)、O15(-Kk·r·sin30°,-Kk·r·cos30°+a)、O19(-KkR, a) and O23(-Kk·r·sin30°,Kk·r·cos30°+a);
The number of the tangent points of the static stability margin impedance circle of the turbonator and the No. 2 circumscribed regular hexagon is 6, and the tangent points are respectively tangent points O1、O5、O9、O13、O17And O21And the coordinate of each tangent point is O1(0,Kk·r-r+Xc)、O5(Kk·r·cos30°,Kk·r·sin30°+a)、O9(Kk·r·cos30°,-Kk·r·sin30°+a)、O13(0,-(Kk·r-r)+Xb)、O17(-Kk·r·cos30°,-KkR sin30 ° + a) and O21(-Kk·r·cos30°,Kk·r·sin30°+a);
The number of the intersection points of the No. 1 externally tangent regular hexagon and the No. 2 externally tangent regular hexagon is 12, and the number is O2、O4、O6、O8、O10、O12、O14、、O16、O18、O20、O22And O24And the coordinates of each tangent point are respectively
Figure BDA0002428954260000081
Figure BDA0002428954260000082
O6(Kk·r,Kk·r·tan15°+a)、O8(Kk·r,-Kk·r·tan15°+a)、
Figure BDA0002428954260000083
Figure BDA0002428954260000084
-(Kk·r-r)+Xb)、
Figure BDA0002428954260000085
Figure BDA0002428954260000086
O18(-Kk·r,-Kk·r·tan15°+a)、O20(-Kk·r,Kk·r·tan15°+a)、
Figure BDA0002428954260000087
And
Figure BDA0002428954260000088
wherein, XcAnd XbAre all intermediate variables, and
Figure BDA0002428954260000089
Figure BDA00024289542600000810
Xconthe equivalent reactance between the generator and the system;
Xdis a generator synchronous reactance;
UNrated voltage for the generator;
SNrated apparent power for the generator;
nathe transformation ratio of a current transformer at the generator terminal is set;
nvthe transformation ratio of the generator terminal voltage transformer is obtained.
Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that features described in different dependent claims and herein may be combined in ways different from those described in the original claims. It is also to be understood that features described in connection with individual embodiments may be used in other described embodiments.

Claims (5)

1. A method for obtaining a low excitation limit curve of a steam turbine generator is characterized by comprising the following steps:
acquiring the center coordinates (0, a) and the radius r of a statically stable impedance circle of the turbonator in an impedance coordinate system according to data information of the turbonator in a statically stable state; wherein the abscissa of the impedance coordinate system represents resistance and the ordinate represents reactance; a is the longitudinal coordinate of the circle center of the static stable impedance circle of the turbonator;
step two, according to the coordinates (0, a) of the circle center, the radius r and the radius KkDrawing a turbine generator static stability margin impedance circle under an impedance coordinate system, wherein the turbine generator static stability impedance circle and the turbine generator static stability margin impedance circle are concentric circles;
Kkrepresenting the coefficients;
drawing a No. 1 externally tangent regular hexagon of the turbine generator static stability margin impedance circle according to the turbine generator static stability margin impedance circle, wherein two opposite vertexes of the No. 1 externally tangent regular hexagon are positioned on a longitudinal axis of an impedance coordinate system, and obtaining a No. 1 externally tangent regular hexagon curve equation according to the relation between the turbine generator static stability margin impedance circle and the No. 1 externally tangent regular hexagon;
step four, clockwise rotating the No. 1 externally tangent regular hexagon by 30 degrees so as to obtain the No. 2 externally tangent regular hexagon of the static stability margin impedance circle of the turbonator, and obtaining a No. 2 externally tangent regular hexagon curve equation according to the relationship among the static stability margin impedance circle of the turbonator, the No. 1 externally tangent regular hexagon and the No. 2 externally tangent regular hexagon;
step five, according to the coordinates (0, a) of the circle center, the radius r and the radius KkObtaining a curve equation of the static stability margin impedance circle of the steam turbine generator, and obtaining all tangent point coordinates of the static stability margin impedance circle of the steam turbine generator and the No. 1 circumscribed regular hexagon according to the static stability margin impedance circle equation of the steam turbine generator and the No. 1 circumscribed regular hexagon curve equation; obtaining all intersection point coordinates of the No. 1 externally tangent regular hexagon and the No. 2 externally tangent regular hexagon according to the No. 1 externally tangent regular hexagon curve equation and the No. 2 externally tangent regular hexagon curve equation; obtaining all tangent point coordinates of the static stability margin impedance circle of the steam turbine generator and the number 2 external tangent regular hexagon according to the static stability margin impedance circle equation of the steam turbine generator and the number 2 external tangent regular hexagon curve equation;
and step six, sequentially connecting all tangent points of the turbine generator static stability margin impedance circle and the No. 1 circumscribed regular hexagon, all intersection points of the No. 1 circumscribed regular hexagon and the No. 2 circumscribed regular hexagon, and all tangent points of the turbine generator static stability margin impedance circle and the No. 2 circumscribed regular hexagon, so as to obtain a dodecagon which is circumscribed on the turbine generator static stability margin impedance circle under an impedance coordinate system, wherein the dodecagon is a turbine generator low excitation limit curve, and thus, the acquisition of the turbine generator low excitation limit curve is completed.
2. The method for obtaining the low excitation limit curve of the steam turbine generator as claimed in claim 1, wherein in the step one, according to the data information of the steam turbine generator in the static stable state, the specific process of obtaining the center coordinates (0, a) and the radius r of the static stable impedance circle of the steam turbine generator in the impedance coordinate system is as follows:
the method comprises the steps of acquiring data information of the turbonator in a static stable state, wherein the data information comprises Xcon、Xd、UN、SN、naAnd nv(ii) a Wherein the content of the first and second substances,
Xconthe equivalent reactance between the generator and the system;
Xdis a generator synchronous reactance;
UNrated voltage for the generator;
SNrated apparent power for the generator;
nathe transformation ratio of a current transformer at the generator terminal is set;
nvthe transformation ratio of a generator terminal voltage transformer is obtained;
step two, under an impedance coordinate system, according to Xcon、Xd、UN、SN、naAnd nvObtaining a and a radius r, thereby obtaining the circle center coordinates (0, a) and the radius r of the turbine generator steady impedance circle; wherein the content of the first and second substances,
Figure FDA0002428954250000021
Figure FDA0002428954250000022
3. the method for obtaining the low excitation limit curve of the steam turbine generator as claimed in claim 1, wherein in the second step, the center coordinates (0, a), the radius r and the radius K are used as the basiskUnder an impedance coordinate system, the specific process of drawing the turbine generator static stability margin impedance circle is as follows:
step two, a, because the turbine generator static stability impedance circle and the turbine generator static stability margin impedance circle are concentric circlesYuA, so as to obtain the center coordinates (0, a) of the turbine generator static margin impedance circleYu);
Wherein, aYuThe vertical coordinate of the circle center of the turbine generator static stability margin impedance circle;
step two, enabling the radius r of the turbine generator static stability margin impedance circleYu=KkR, from the center coordinates (0, a)Yu) And radius rYuAnd drawing the turbine generator static stability margin impedance circle under the impedance coordinate system, thereby completing the drawing of the turbine generator static stability margin impedance circle.
4. The method for obtaining the low excitation limit curve of the steam turbine generator as claimed in claim 3, wherein K is greater than or equal to 1.05 ≦ Kk≤1.2。
5. The method for obtaining the low excitation limit curve of the steam turbine generator as claimed in claim 1, wherein in the fifth step, the number of the turbine generator static stability margin impedance circle and all the tangent points of the No. 1 circumscribed regular hexagon are 6, and the number of the tangent points is respectively the tangent point O3、O7、O11、O15、O19And O23And the coordinates of each tangent point are respectively O3(Kk·r·sin30°,Kk·r·cos30°+a)、O7(Kk·r,a)、O11(Kk·r·sin30°,-Kk·r·cos30°+a)、O15(-Kk·r·sin30°,-Kk·r·cos30°+a)、O19(-KkR, a) and O23(-Kk·r·sin30°,Kk·r·cos30°+a);
The number of the tangent points of the static stability margin impedance circle of the turbonator and the No. 2 circumscribed regular hexagon is 6, and the tangent points are respectively tangent points O1、O5、O9、O13、O17And O21And the coordinate of each tangent point is O1(0,Kk·r-r+Xc)、O5(Kk·r·cos30°,Kk·r·sin30°+a)、O9(Kk·r·cos30°,-Kk·r·sin30°+a)、O13(0,-(Kk·r-r)+Xb)、O17(-Kk·r·cos30°,-KkR sin30 ° + a) and O21(-Kk·r·cos30°,Kk·r·sin30°+a);
The number of the intersection points of the No. 1 externally tangent regular hexagon and the No. 2 externally tangent regular hexagon is 12, and the number is O2、O4、O6、O8、O10、O12、O14、、O16、O18、O20、O22And O24And the coordinates of each tangent point are respectively
Figure FDA0002428954250000031
Figure FDA0002428954250000032
O6(Kk·r,Kk·r·tan15°+a)、O8(Kk·r,-Kk·r·tan15°+a)、
Figure FDA0002428954250000033
Figure FDA0002428954250000034
-(Kk·r-r)+Xb)、
Figure FDA0002428954250000035
Figure FDA0002428954250000036
O18(-Kk·r,-Kk·r·tan15°+a)、O20(-Kk·r,Kk·r·tan15°+a)、
Figure FDA0002428954250000037
Figure FDA0002428954250000038
And
Figure FDA0002428954250000039
wherein, XcAnd XbAre all intermediate variables, and
Figure FDA00024289542500000310
Figure FDA00024289542500000311
Xconthe equivalent reactance between the generator and the system;
Xdis a generator synchronous reactance;
UNrated voltage for the generator;
SNrated apparent power for the generator;
nathe transformation ratio of a current transformer at the generator terminal is set;
nvthe transformation ratio of the generator terminal voltage transformer is obtained.
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