CN113992082B - Combined de-excitation resistor circuit - Google Patents
Combined de-excitation resistor circuit Download PDFInfo
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- CN113992082B CN113992082B CN202111183496.7A CN202111183496A CN113992082B CN 113992082 B CN113992082 B CN 113992082B CN 202111183496 A CN202111183496 A CN 202111183496A CN 113992082 B CN113992082 B CN 113992082B
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- 230000005284 excitation Effects 0.000 claims abstract description 40
- 230000002441 reversible effect Effects 0.000 claims abstract description 28
- 238000004804 winding Methods 0.000 claims abstract description 24
- 238000000034 method Methods 0.000 claims description 41
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical group [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 claims description 39
- 230000008569 process Effects 0.000 claims description 32
- 239000011787 zinc oxide Substances 0.000 claims description 17
- FFBHFFJDDLITSX-UHFFFAOYSA-N benzyl N-[2-hydroxy-4-(3-oxomorpholin-4-yl)phenyl]carbamate Chemical compound OC1=C(NC(=O)OCC2=CC=CC=C2)C=CC(=C1)N1CCOCC1=O FFBHFFJDDLITSX-UHFFFAOYSA-N 0.000 claims description 3
- 238000010891 electric arc Methods 0.000 claims 1
- 238000009413 insulation Methods 0.000 abstract description 5
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 21
- 229910010271 silicon carbide Inorganic materials 0.000 description 19
- 230000005347 demagnetization Effects 0.000 description 8
- 238000012360 testing method Methods 0.000 description 6
- 238000010586 diagram Methods 0.000 description 5
- 238000001075 voltammogram Methods 0.000 description 5
- 230000002829 reductive effect Effects 0.000 description 4
- 230000009471 action Effects 0.000 description 3
- 230000008859 change Effects 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 230000001960 triggered effect Effects 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 230000008033 biological extinction Effects 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- 230000002349 favourable effect Effects 0.000 description 2
- 230000000670 limiting effect Effects 0.000 description 2
- 230000002035 prolonged effect Effects 0.000 description 2
- 230000002238 attenuated effect Effects 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000007123 defense Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000010494 dissociation reaction Methods 0.000 description 1
- 230000005593 dissociations Effects 0.000 description 1
- 238000004870 electrical engineering Methods 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 230000020169 heat generation Effects 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
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- 230000003068 static effect Effects 0.000 description 1
- 230000002123 temporal effect Effects 0.000 description 1
Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P9/00—Arrangements for controlling electric generators for the purpose of obtaining a desired output
- H02P9/10—Control effected upon generator excitation circuit to reduce harmful effects of overloads or transients, e.g. sudden application of load, sudden removal of load, sudden change of load
- H02P9/12—Control effected upon generator excitation circuit to reduce harmful effects of overloads or transients, e.g. sudden application of load, sudden removal of load, sudden change of load for demagnetising; for reducing effects of remanence; for preventing pole reversal
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/06—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for dynamo-electric generators; for synchronous capacitors
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- Control Of Eletrric Generators (AREA)
Abstract
The application aims to provide a combined de-excitation resistor circuit. The combined de-excitation resistor circuit comprises a first branch circuit and a second branch circuit which are connected in parallel: the first branch circuit comprises a linear resistor and an inverse thyristor which are connected in series, a second terminal of the linear resistor is electrically connected with a cathode end of the inverse thyristor, and an anode end of the inverse thyristor is electrically connected with a cathode end of the generator exciting winding; the second branch circuit comprises a nonlinear resistor and a unidirectional switch which are connected in series, a second terminal of the nonlinear resistor is electrically connected with a cathode end of the unidirectional switch, and an anode end of the unidirectional switch is electrically connected with a cathode end of an excitation winding of the generator; the first terminal of the linear resistor is connected in parallel with the first terminal of the nonlinear resistor and is electrically connected with the positive terminal of the generator exciting winding. The de-excitation resistor can effectively control the de-excitation reverse overvoltage level when de-excitation is performed by heavy current under the worst working condition, ensure the insulation safety of the rotor and give consideration to the rapidity of de-excitation.
Description
Technical Field
The application relates to the technical field of electrical engineering, in particular to a combined de-excitation resistor circuit.
Background
The de-excitation device in the generator excitation system is the last defense line for ensuring the safe shutdown of the generator set after an accident. When the generator and the excitation system thereof have faults inside or outside, after tripping and disconnecting the relay protection action of the generator-transformer group, a magnetic-killing switch in a field-killing device of the excitation system is quickly tripped, and an excitation loop interrupts an excitation power unit to output excitation power to an excitation winding of the generator; and meanwhile, the de-excitation resistor is triggered to be conducted, and the energy stored in the exciting winding inductor is transferred to the de-excitation resistor to be completely consumed.
The safety of the main equipment can be ensured only by quick and reliable de-excitation in the fault process of the generator-transformer set and other related system equipment, and the visible de-excitation resistor plays an important role in the safe operation of the generator set.
The current widely used de-excitation resistors in the static excitation system of the large and medium-sized generator set comprise three types, namely a linear resistor, a zinc oxide (ZnO) nonlinear resistor and a silicon carbide (SiC) nonlinear resistor, and the selection of different de-excitation resistors can obviously influence the speed of the de-excitation process and the reverse overvoltage level of de-excitation. The typical volt-ampere characteristics of the three types of de-excitation resistors are shown in figure 1.
The linear resistor has high reliability, convenient maintenance and test, is easy to trigger and conduct, is beneficial to reducing the load of the arc contact of the magnetic extinction switch, and can prolong the service life of the switch. Therefore, the linear resistor is generally used in the occasions with low requirement on the de-excitation speed or weak influence of the de-excitation speed of the exciting winding current on the de-excitation time in the generator magnetic field. The volt-ampere characteristic of the linear resistor is a linear straight line (as shown by a curve c in fig. 1), the voltage at two ends of the linear resistor is in a complete linear relation with the flowing current, and the resistance value R is almost unchanged in the process of de-excitation. Under the worst working condition (such as short circuit at the generator end, no-load false forced excitation and the like), the reverse de-excitation voltage is highest when the maximum de-excitation current flows. Therefore, the highest de-excitation voltage must be ensured to be within a safe range (preventing the rotor insulation from being damaged), thereby greatly limiting the value range of the linear resistor; when the resistor is smaller, the de-excitation time is obviously prolonged, and the rapid de-excitation during faults is not facilitated; meanwhile, in the de-excitation process, along with the reduction of de-excitation current, the voltage at two ends of the resistor is reduced, so that the current attenuation speed is further reduced, and the tailing phenomenon in the de-excitation process is obvious.
The volt-ampere characteristic of the zinc oxide (ZnO) de-excitation resistor is a nonlinear curve (as shown by curve b in fig. 1), and the volt-ampere characteristic expression is u=ci β Wherein, C is the whole group of nonlinear resistance coefficient, beta is the nonlinear coefficient, the nonlinear coefficient is quite strong, and the nonlinear coefficient beta is generally 0.046, so that the voltage change at two ends of the nonlinear coefficient is quite small in a quite wide through-current range, namely, the voltage change at two ends of the de-excitation resistor is quite small in the de-excitation process, the current is attenuated almost according to a linear rule, and the rapid de-excitation under the fault is facilitated. The maximum de-excitation flow under the worst working condition has a low de-excitation counter-pressure rise amplitude, is suitable for controlling the reverse de-excitation voltage in a safety range, and is favorable for rotor insulation safety in the de-excitation process. However, when the exciting current is demagnetized (such as no-load or load rated working condition), the arc voltage requirement for the breaking of the magnetic-killing switch is not reduced, and the contact burden is heavy when the magnetic-killing switch is broken.
The voltammetric characteristic of the silicon carbide (SiC) de-excitation resistor is also a nonlinear curve (as shown by curve a in fig. 1), and can be expressed as u=ci as well β The nonlinear characteristic is weak, the nonlinear coefficient beta is generally 0.3-0.4, and the voltage change at two ends of the nonlinear coefficient beta is also obvious in a wide through-flow range. The maximum de-excitation current under the worst working condition has obvious de-excitation back pressure rise (the rise degree is lower than the linear resistance but higher than the ZnO resistance) when flowing, and the reverse de-excitation voltage is required to be ensured not to exceed the safety range; after the level of the de-excitation voltage at high current is considered, the de-excitation time is increased due to the low de-excitation voltage at the time of de-excitation at smaller exciting current. But the silicon carbide resistor is also easier to trigger and conduct, which is beneficial to reducing the load of the arc contact of the magnetic extinction switch. Meanwhile, the silicon carbide resistor is in an open circuit state after failure, the safety of the device is higher, the power density is higher, the size is smaller, the arrangement is compact, and the silicon carbide resistor is widely applied to the excitation systems of imported manufacturers of power generating sets in many domestic power plants.
Therefore, the linear resistor is used as the de-excitation resistor, the problem that the reverse de-excitation voltage is possibly higher when the high-current de-excitation is performed under the serious working condition, the de-excitation time is longer when the low-current de-excitation is performed, and the tailing phenomenon is obvious in the de-excitation process along with the current drop is solved.
In order to avoid the defects of the single resistor devices in the de-excitation process and fully exert the respective excellent characteristics of the single resistor devices, the effective combination of the existing de-excitation resistors is needed, so that the de-excitation reverse overvoltage level can be effectively controlled during the de-excitation of large current under the worst working condition, the insulation safety of a rotor is ensured, meanwhile, the switch-on is easy to trigger during the de-excitation under the small current working condition, the current conversion burden of a de-excitation switch is reduced, and the service life of the switch is prolonged.
According to the combined de-excitation resistor volt-ampere characteristic is changed by adjusting the linear resistance value and the non-linear resistance value coefficient C, and the de-excitation voltage level and the de-excitation speed are adjusted, optimized and changed according to requirements.
The above information disclosed in the background section is only for enhancement of understanding of the background of the application and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art.
Disclosure of Invention
The application aims at providing a combined de-excitation resistor circuit, which changes the volt-ampere characteristic of the combined de-excitation resistor by adjusting the linear resistance value and the non-linear resistance value coefficient C, and adjusts, optimizes and changes the de-excitation voltage and de-excitation speed according to the requirement.
According to an aspect of the present application, a combined de-magnetoresistance circuit includes a first branch circuit and a second branch circuit connected in parallel, wherein:
the first branch circuit comprises a linear resistor and an inverse thyristor which are connected in series, a second terminal of the linear resistor is electrically connected with the cathode end of the inverse thyristor, and the anode end of the inverse thyristor is electrically connected with the cathode end of the generator excitation winding;
the second branch circuit comprises a nonlinear resistor and a unidirectional switch which are connected in series, a second terminal of the nonlinear resistor is electrically connected with a cathode end of the unidirectional switch, and an anode end of the unidirectional switch is electrically connected with a cathode end of the generator excitation winding;
the first terminal of the linear resistor is connected with the first terminal of the nonlinear resistor in parallel and is electrically connected with the positive electrode end of the generator exciting winding.
According to some embodiments, the relationship between the initial total current through the de-excitation resistor and the initial voltage across the de-excitation resistor satisfies:
r is the total resistance of the linear resistor, C is the integral resistance coefficient of the nonlinear resistor, beta is the nonlinear coefficient of the nonlinear resistor, I m1 U is the initial total current flowing through the de-excitation resistor under the first de-excitation condition m1 Is the initial voltage at the two ends of the de-excitation resistor under the first de-excitation working condition, I m2 U is the initial total current flowing through the de-excitation resistor under the second de-excitation condition m2 And the initial voltage at two ends of the de-excitation resistor under the second de-excitation working condition.
According to some embodiments, the initial total current flowing through the de-excitation resistor is the generator excitation current flowing through the de-excitation resistor completely when the de-excitation switch trips to trigger the de-excitation resistor to be turned on and the arc flowing through the de-excitation switch is extinguished;
the initial voltages at the two ends of the de-excitation resistor are voltages at the two ends of the de-excitation resistor corresponding to the initial total current when the de-excitation resistor passes through the initial total current.
According to some embodiments, the nominal configuration capacity of the linear resistor is determined as:
u m for the instantaneous value, i of the voltage at two ends of the de-excitation resistor in the de-excitation process 1 T is the de-excitation current flowing through the first branch circuit 0 In order to turn on the de-excitation resistor at the beginning of the de-excitation process,t e and K is a margin coefficient for the end time of the de-excitation process.
According to some embodiments, the end time of the de-excitation process is de-excitation total current i m Less than 1% of the initial total current of the de-magnetoresistance.
According to some embodiments, the nominal configuration capacity of the nonlinear resistor is determined as:
i 2 is a de-excitation current flowing through the second branch circuit.
According to some embodiments, further comprising: and the jumper is electrically connected with the reverse thyristor and controls the reverse thyristor to be started.
According to some embodiments, the unidirectional switch is a diode or a second reverse thyristor.
According to some embodiments, the jumper is electrically connected with the second reverse thyristor, controlling the second reverse thyristor to turn on.
According to some embodiments, the linear resistor comprises a single linear resistor or a series-parallel combination of multiple linear resistors.
According to some embodiments, the nonlinear resistor comprises a single nonlinear resistor or a series-parallel combination of multiple nonlinear resistors.
According to some embodiments, the nonlinear resistor is a zinc oxide resistor.
According to an aspect of the present application, an excitation system is provided, comprising a combined de-excitation resistor circuit as described in any of the preceding claims.
According to an aspect of the present application, a generator set is presented, comprising an excitation system as described above.
Technical solutions according to some embodiments of the present application may have one or more of the following benefits:
(1) The voltage-current characteristic difference of the linear resistor and the nonlinear resistor in different current sections is utilized to carry out parameter selection on the linear resistor and the nonlinear resistor, and the obtained de-excitation resistor is subjected to parallel combination, so that the de-excitation reverse overvoltage level can be effectively controlled during de-excitation of large current under severe fault working conditions, the insulation safety of a rotor in the de-excitation process is ensured, and meanwhile, the back voltage level of the de-excitation resistor in the de-excitation process is maintained to ensure the rapidity of the de-excitation process.
(2) When the magnetic switch is demagnetized under a small current working condition (no-load or load rated working condition), the linear resistance consumes energy as the main material, is easy to trigger and conduct, is favorable for quenching arcs of contacts of the magnetic switch, reduces the current conversion burden of the switch and prolongs the service life of the switch.
(3) The SiC resistance characteristics are well fitted through the combination of the two, the defects of the SiC resistance are overcome, the SiC de-excitation resistance is effectively replaced in the original occasion of using the imported SiC de-excitation resistance, and the problem of the supply risk of imported SiC devices can be effectively solved.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the application.
Drawings
The above and other objects, features and advantages of the present application will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings. The drawings described below are only some of the embodiments of the present application and are not intended to limit the present application.
FIG. 1 shows typical voltammograms of three resistors ZnO, siC and R;
fig. 2 shows a combined de-magnetoresistance circuit diagram of an exemplary embodiment;
FIG. 3 illustrates yet another embodiment of an exemplary combined de-magnetoresistance circuit diagram;
fig. 4 shows a combined de-excitation resistive voltammetric profile versus SiC resistive voltammetric profile for an exemplary embodiment.
Detailed Description
Example embodiments will now be described more fully with reference to the accompanying drawings. However, the exemplary embodiments can be embodied in many forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the example embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar parts, and thus a repetitive description thereof will be omitted.
The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of embodiments of the disclosure. One skilled in the relevant art will recognize, however, that the disclosed aspects may be practiced without one or more of the specific details, or with other methods, components, materials, devices, or the like. In these instances, well-known structures, methods, devices, implementations, materials, or operations are not shown or described in detail.
The flow diagrams depicted in the figures are exemplary only, and do not necessarily include all of the elements and operations/steps, nor must they be performed in the order described. For example, some operations/steps may be decomposed, and some operations/steps may be combined or partially combined, so that the order of actual execution may be changed according to actual situations.
The terms first, second and the like in the description and in the claims of the present application and in the above-described figures, are used for distinguishing between different objects and not for describing a particular sequential order. Furthermore, the terms "comprise" and "have," as well as any variations thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, system, article, or apparatus that comprises a list of steps or elements is not limited to only those listed steps or elements but may include other steps or elements not listed or inherent to such process, method, article, or apparatus.
Those skilled in the art will appreciate that the drawings are schematic representations of example embodiments, and that the modules or flows in the drawings are not necessarily required to practice the present application, and therefore, should not be taken to limit the scope of the present application.
Apparatus embodiments of the present application are described below, which may be used to perform method embodiments of the present application. For details not disclosed in the device embodiments of the present application, reference may be made to the method embodiments of the present application.
Fig. 2 shows a circuit diagram of a combined de-magnetoresistance of an exemplary embodiment.
As shown in fig. 2, the combined de-excitation resistor circuit comprises two branch circuits connected in parallel; the first branch comprises a linear resistor element R and an inverse thyristor element S1 which are connected in series, wherein the 2 end of the linear resistor R is connected with the cathode of the thyristor element S1, and the anode of the thyristor element S1 is connected with the cathode end of the generator excitation winding; the second branch comprises a nonlinear resistor such as a zinc oxide (ZnO) element FR and a reverse diode element D1 which are connected in series, wherein the 2 end of the nonlinear resistor FR is connected with the cathode of the diode element D1, and the anode of the diode element D1 is also connected with the negative end of the generator excitation winding; the 1 end of the first branch linear resistor R is directly connected with the 1 end of the second branch zinc oxide resistor FR and is connected with the positive end of the generator exciting winding in parallel.
According to an exemplary embodiment, the jumper connects the trigger terminal of the thyristor element S1. The jumper detects the voltage across the loop. When the voltage reaches or exceeds the set voltage threshold Uth, a trigger pulse is sent out to trigger the thyristor element S1 to conduct, so that the linear resistor R and the nonlinear de-excitation resistor FR are communicated with the generator rotor on an electrical loop to form a loop, and the energy storage of the rotor is absorbed.
According to an exemplary embodiment, the thyristor element S1 is not conductive before the jumper is triggered, so that the loop in which the linear de-reluctance R is located is not in communication with the generator rotor (corresponding to an open circuit).
According to some embodiments, when the magnetic-killing switch is tripped, an arc voltage generated by tripping the magnetic-killing switch is overlapped with the output voltage of the rectifier bridge to form a reverse voltage um, after the jumper detects that the voltage is larger than a set threshold value Uth, the thyristor element S1 is triggered, so that the thyristor element S1 is conducted, a linear resistor R is connected in a loop and is connected with a rotor in parallel, and then rotor current is transferred to the linear resistor R and a nonlinear resistor FR to absorb rotor energy. After the thyristor element S1 is turned on, it is turned on until the current flowing through the linear resistor R reaches 0A.
According to some embodiments, two typical de-excitation are determined according to related industry specificationsThe initial total current flowing through the de-excitation resistor under the working condition and the initial voltage at two ends of the de-excitation resistor comprise the initial total current I flowing through the de-excitation resistor under the first de-excitation working condition m1 Initial voltage U across de-excitation resistor m1 And an initial total current I flowing through the de-excitation resistor under a second de-excitation condition m2 Initial voltage U across de-excitation resistor m2 The method comprises the steps of carrying out a first treatment on the surface of the The initial total current flowing through the de-excitation resistor is the generator excitation current which is completely flowing through the de-excitation resistor at the moment when the de-excitation switch trips to trigger the de-excitation resistor to be conducted and the arc flowing through the de-excitation switch is extinguished; the initial voltage at two ends of the de-excitation resistor refers to the voltage at two ends of the de-excitation resistor corresponding to the total initial current.
According to some embodiments, the relationship between the initial total current flowing through the de-excitation resistor and the initial voltage across the de-excitation resistor is obtained according to the relationship between the total current of the de-excitation resistor and the branch current, as follows:
and solving by the simultaneous calculation of the formula to obtain an R value and a C value. Wherein R is the total resistance of the linear resistor element; c is the overall resistance coefficient of the zinc oxide nonlinear resistor, beta is the nonlinear coefficient of the nonlinear resistor, and the zinc oxide resistor is generally 0.046.
According to some embodiments, the energy capacities of the linear resistor R and the nonlinear resistor FR are determined. And simulating various typical de-excitation working conditions, including no-load false excitation of the generator, short circuit of the generator end, disconnection and tripping of rated load working conditions and the like. And according to the maximum energy values respectively absorbed by the linear resistance element R and the nonlinear resistance element FR in different de-excitation working conditions, multiplying the maximum energy values by a margin coefficient K and then using the maximum energy values as nominal capacity configuration. The nominal arrangement capacity Sr of the linear resistive element R, the nominal arrangement capacity Sfr of the zinc oxide nonlinear resistive element FR is calculated as follows:
wherein u is m I is the instantaneous value of the voltage at two ends of the de-excitation resistor in the de-excitation process 1 For the demagnetizing current flowing through the first branch, i 2 For the demagnetizing current flowing through the second branch; t is t 0 T is the time t of the conduction of the de-excitation resistor at the beginning of the de-excitation process e To obtain the total de-excitation current i at the end of de-excitation process m The moment less than 1% of the initial total current of the de-excitation resistor considers that the de-excitation process is finished; k is a margin coefficient, and 1.2-1.4 is taken.
According to some embodiments, the linear resistor element R may employ a single linear resistor or a series-parallel combination of multiple linear resistors, the total resistance value R satisfies the above formula, and the total capacity Sr satisfies the above formula; the zinc oxide nonlinear resistor element FR may adopt a series-parallel combination of a plurality of zinc oxide nonlinear resistors, the overall resistance coefficient C satisfies the above equation, and the total capacity Sfr satisfies the above equation.
The application is further described by taking a certain type of 300MW thermal power generating unit excitation system as an example. In the embodiment, the generator set adopts a self-shunt excitation mode, and main parameters of the generator set are shown in the following table:
| sequence number | Name of the name | Numerical value |
| 1. | Rated power | 300MW |
| 2. | Rated power factorNumber of digits | 0.85 |
| 3. | Rated stator voltage | 20kV |
| 4. | Rated stator current | 10.190kA |
| 5. | No-load rated exciting current | 750A |
| 6. | No-load rated exciting voltage | 150V |
| 7. | Load rated exciting current Ifn | 2203A |
| 8. | Load rated field voltage Ufn | 463V |
According to an exemplary embodiment, the structure of the combined de-reluctance circuit is determined, and the combined de-reluctance circuit is formed by connecting two branch circuits in parallel: the first branch consists of a linear resistor element R and an inverse thyristor element S1 which are connected in series, wherein the 2 end of the linear resistor R is connected with the cathode of the thyristor element S1, and the anode of the thyristor element S1 is connected with the cathode of the generator excitation winding; the second branch consists of a nonlinear resistor zinc oxide (ZnO) element FR and a reverse diode element D2 which are connected in series, wherein the 2 end of the nonlinear resistor FR is connected with the cathode of the diode element D2, and the anode of the diode element D2 is also connected with the negative end of the generator excitation winding; the 1 end of the first branch linear resistor R is directly connected with the 1 end of the second branch zinc oxide resistor FR and is connected with the positive pole of the generator exciting winding in parallel.
According to the example embodiment, the rotor overvoltage should not exceed 60% of the rotor factory frequency withstand voltage test voltage amplitude (i.e. 6 times of the rotor rated voltage according to the unit parameters) and should be lower than the rotor overvoltage protection action voltage when in de-excitation according to the requirement of DL/T843. When the three phases of the machine end are suddenly short-circuited under the rated load, the maximum initial current for de-excitation can reach 3-4 times of rated exciting current, so that the initial total current flowing through the de-excitation resistor under the first de-excitation working condition is considered according to 4 times of Ifn, and the initial voltage Um1 at the two ends of the de-excitation resistor is determined to be not more than 5Ufn (less than 6 times of rated rotor voltage). When the dissociation and the demagnetization of the thermal power generating unit under the rated load working condition are considered, the maximum initial current for the demagnetization is the rated exciting current Ifn, and the thermal power generating unit does not need to pursue the extremely fast demagnetization speed, so that the initial total current flowing through the demagnetization resistor under the second demagnetization working condition is considered according to 1 time of Ifn, and meanwhile, the initial voltage Um2 at the two ends of the demagnetization resistor is determined to be 2Ufn.
According to an example embodiment, the relationship between the initial total current of the de-excitation resistor and the initial voltage across the de-excitation resistor obtained from the de-excitation initial current voltage values of the two de-excitation operating points is shown in the following formula (7), and the r= 0.420336 and c= 1594.67 are obtained by the simultaneous calculation of the formulas. I.e., the total resistance of the linear resistive element is 0.420336 ohms, approximately 2 times the rotor thermal resistance; and the voltage across the zinc oxide nonlinear resistor when the whole zinc oxide nonlinear resistor flows through 1A current is 1594.67V.
Under the parameter configuration, if the machine set is demagnetized by the tripping demagnetizing switch under the no-load rated working condition or the tripping demagnetizing switch under the load rated working condition, the linear resistor R is mainly used for bearing the task of demagnetizing and energy consumption, and the current flowing in the nonlinear resistor FR is very small; meanwhile, the linear resistor is easy to trigger and conduct, and the de-excitation voltages at the two ends of the resistor are not high, so that the purposes of reducing the current-converting burden of the de-excitation switch and prolonging the service life of the switch are achieved. And when the initial current of de-excitation reaches 4Ifn under the most serious fault working condition, the shunt effect of the FR nonlinear resistor effectively controls the maximum reverse overvoltage value of de-excitation not to exceed 5Ufn, and meanwhile, the conduction of the FR nonlinear resistor maintains the de-excitation back voltage level in the de-excitation process so as to ensure the rapidity of the de-excitation process.
According to an example embodiment, various typical de-excitation conditions are simulated, including no-load false excitation of a generator, sudden short circuit of a machine end under rated load of the generator, disconnection and tripping of the rated load conditions, and the like, and relay protection action time and de-excitation switch tripping time are considered. According to the maximum energy values respectively absorbed by the linear resistor element R and the nonlinear resistor element FR in the whole process of different demagnetizing working conditions, and then multiplying the maximum energy values by a margin coefficient K to be used as a capacity configuration value, wherein the margin coefficient K is generally 1.2-1.4.
The invention is further described by taking a certain type of excitation system of a 300MW hydroelectric generating set as an example. In the embodiment, the generator set still adopts a self-shunt excitation mode, and main parameters of the generator set are shown in the following table:
according to an exemplary embodiment, the structure of the combined de-reluctance circuit is determined, and the combined de-reluctance circuit is formed by connecting two branch circuits in parallel: the first branch consists of a linear resistor element R and an inverse thyristor element S1 which are connected in series, wherein the 2 end of the linear resistor R is connected with the cathode of the thyristor element S1, and the anode of the thyristor element S1 is connected with the cathode of the generator excitation winding; the second branch consists of a nonlinear resistor zinc oxide (ZnO) element FR and a reverse diode element D2 which are connected in series, wherein the 2 end of the nonlinear resistor FR is connected with the cathode of the diode element D2, and the anode of the diode element D2 is also connected with the negative end of the generator excitation winding; the 1 end of the first branch linear resistor R is directly connected with the 1 end of the second branch zinc oxide resistor FR and is connected with the positive pole of the generator exciting winding in parallel.
According to an exemplary embodiment, the reverse voltage of the exciting winding during de-excitation is preferably controlled to be not lower than 30% of the withstand voltage test voltage of the winding to the ground during the factory test (i.e., 3 times of the rated voltage of the rotor according to the set parameter) and not higher than 50% of the withstand voltage test voltage of the winding to the ground during the factory test (i.e., 5 times of the rated voltage of the rotor according to the set parameter) according to the requirement of DL/T583. In addition, the excitation system adopts an inlet SiC de-excitation resistor, and the combination de-excitation resistor characteristic is considered to be matched with the original SiC resistor characteristic as much as possible when the de-excitation resistor is modified. The nonlinear volt-ampere characteristic of the original SiC demagnetizing resistor is shown in the following formula. The nonlinear index of SiC is 0.4.
U＝42.27×I 0.4
According to the calculation of the formula, under the severe fault working condition of the short circuit at the machine end, the calculated initial de-excitation current is 3 times of rated excitation current, the initial de-excitation voltage at the two ends of the SiC resistor is about 1500V, and the technical requirement of DL/T583 is met. When the rated load of the unit is split and demagnetized, the initial voltage of the demagnetization at the two ends of the SiC resistor is 966.5V and 3.22 times of the rated exciting voltage, which is calculated according to the initial current of the demagnetization being 1 time of the rated exciting current, so that the technical requirement of DL/T583 is met. In order to match the characteristics of the combined de-excitation resistor with the original SiC resistance as much as possible, considering that the initial total current flowing through the de-excitation resistor under the first de-excitation working condition point is 3 times Ifn, and determining that the initial voltage Um1 at two ends of the de-excitation resistor is 1500V at the moment; and determining that the initial total current flowing through the de-excitation resistor under the second de-excitation condition is 1 times Ifn, and determining that the initial voltage Um2 at the two ends of the de-excitation resistor at the moment is 966.5V.
Solving by the following simultaneous calculation yields r= 0.38664 and c= 1028.93. I.e., the total resistance of the linear resistive element is 0.38664 ohms, approximately 3.22 times the rotor thermal resistance; and the voltage across the zinc oxide nonlinear resistor when the whole zinc oxide nonlinear resistor flows through 1A current is 1028.93V.
According to an example embodiment, under the parameter configuration, if the tripping demagnetizing switch demagnetizes under the no-load rated condition of the unit or the tripping demagnetizing switch demagnetizes under the load rated condition, the linear resistor R still bears the task of demagnetizing and energy consumption, and the current flowing in the nonlinear resistor FR is small; meanwhile, the linear resistor is easy to trigger and conduct, and the de-excitation voltages at the two ends of the resistor are not high, so that the purposes of reducing the current-converting burden of the de-excitation switch and prolonging the service life of the switch are achieved. And when the initial current of de-excitation reaches 3Ifn under the most serious fault working condition, the shunt effect of the FR nonlinear resistor effectively controls the maximum reverse overvoltage value of de-excitation not to exceed 5Ufn, and meanwhile, the conduction of the FR nonlinear resistor maintains the de-excitation back voltage level in the de-excitation process so as to ensure the rapidity of the de-excitation process.
Fig. 3 shows yet another embodiment of an exemplary combined de-magnetoresistance circuit diagram.
Referring to fig. 3, fig. 3 differs from fig. 2 in that: in fig. 2, a diode D1 is connected in series with the nonlinear resistor FR, and in fig. 3, a thyristor element S2 is connected in series with the nonlinear resistor FR. And the jumper is connected to both the trigger terminals of the thyristor element S1 and the thyristor element S2.
According to an exemplary embodiment, since the nonlinear resistor FR is a ZnO nonlinear resistor. The voltammetric characteristic is a distinct nonlinear curve, and the current flowing when the voltage across it is low is small, e.g. less than 1mA, this current being called leakage current. When the system works normally, the nonlinear resistor FR can flow through small leakage current, and has little influence on the characteristics and power consumption heating. However, if the system works normally, the leakage current flowing through the nonlinear resistor FR is relatively obvious (for example, greater than 10 mA), the nonlinear characteristic of the nonlinear resistor FR can be influenced for a long time, and meanwhile, the power consumption and the heat generation of the resistor are increased.
According to some embodiments, in the design of the excitation system, if the system works normally (the excitation system outputs normal sawtooth wave rectification voltage), the reverse value of the rectification voltage is smaller, the leakage current at two ends of the nonlinear resistor FR is smaller, and a diode can be used for being connected in series with the nonlinear resistor FR to ensure unidirectional conduction of the current during de-excitation; if the system works normally (the exciting system outputs normal rectification voltage), the reverse value of the rectification voltage is larger, the leakage current at the two ends of the nonlinear resistor FR is larger (approaching or being larger than 10 mA), then a thyristor is needed to be connected in series with the nonlinear resistor FR, the FR loop is completely blocked when the system is normally conducted, and the nonlinear resistor FR loop is conducted through a jumper when the system is de-magnetized.
Fig. 4 shows a combined de-excitation resistive voltammetric profile versus SiC resistive voltammetric profile for an exemplary embodiment.
As shown in FIG. 4, the combined de-excitation resistor voltammetric characteristic curve and the SiC resistor voltammetric characteristic curve are shown, and the combined de-excitation resistor circuit provided by the application is better matched with the original SiC resistor characteristic in the de-excitation full current range.
It should be clearly understood that this application describes how to make and use particular examples, but is not limited to any details of these examples. Rather, these principles can be applied to many other embodiments based on the teachings of the present disclosure.
Furthermore, it should be noted that the above-described figures are merely illustrative of the processes involved in the method according to the exemplary embodiments of the present application, and are not intended to be limiting. It will be readily appreciated that the processes shown in the above figures do not indicate or limit the temporal order of these processes. In addition, it is also readily understood that these processes may be performed synchronously or asynchronously, for example, among a plurality of modules.
Exemplary embodiments of the present application are specifically illustrated and described above. It is to be understood that this application is not limited to the details of construction, arrangement or method of implementation described herein; on the contrary, the application is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
Claims (8)
1. The utility model provides a combination formula de-excitation resistance circuit, its characterized in that, combination formula de-excitation resistance circuit includes jumper, parallelly connected first branch circuit and second branch circuit, wherein:
the first branch circuit comprises a linear resistor and an inverse thyristor which are connected in series, a second terminal of the linear resistor is electrically connected with the cathode end of the inverse thyristor, and the anode end of the inverse thyristor is electrically connected with the cathode end of the generator excitation winding;
the second branch circuit comprises a nonlinear resistor and a unidirectional switch which are connected in series, a second terminal of the nonlinear resistor is electrically connected with a cathode end of the unidirectional switch, and an anode end of the unidirectional switch is electrically connected with a cathode end of the generator excitation winding;
the jumper is electrically connected with the reverse thyristor and is used for controlling the reverse thyristor to be started;
the first terminal of the linear resistor is connected with the first terminal of the nonlinear resistor in parallel and is electrically connected with the positive electrode end of the generator excitation winding;
the jumper is used for detecting the voltages at two ends of the loop, and sending out trigger pulses to trigger the reverse thyristors to be conducted under the condition that the voltages reach or exceed a set voltage threshold, so that the linear resistor and the nonlinear resistor are communicated with a generator rotor on an electrical loop to form a loop, and the rotor is absorbed to store energy;
the relation between the initial total current flowing through the de-excitation resistor and the initial voltage at the two ends of the de-excitation resistor is as follows:
r is the total resistance of the linear resistor, C is the integral resistance coefficient of the nonlinear resistor, beta is the nonlinear coefficient of the nonlinear resistor, I m1 U is the initial total current flowing through the de-excitation resistor under the first de-excitation condition m1 Is the initial voltage at the two ends of the de-excitation resistor under the first de-excitation working condition, I m2 U is the initial total current flowing through the de-excitation resistor under the second de-excitation condition m2 The initial voltage at two ends of the de-excitation resistor under the second de-excitation working condition;
the initial total current flowing through the de-excitation resistor is the generator excitation current which is generated by tripping of the de-excitation switch to trigger the de-excitation resistor to be conducted, the electric arc flowing through the de-excitation switch is extinguished, and the generator excitation current completely flows through the de-excitation resistor;
the initial voltages at the two ends of the de-excitation resistor are voltages at the two ends of the de-excitation resistor corresponding to the de-excitation resistor when the de-excitation resistor passes through the initial total current;
the nominal configuration capacity of the linear resistor is determined as:
u m for the instantaneous value, i of the voltage at two ends of the de-excitation resistor in the de-excitation process 1 T is the de-excitation current flowing through the first branch circuit 0 T is the time t of the conduction of the de-excitation resistor at the beginning of the de-excitation process e K is a margin coefficient for the end time of the de-excitation process;
the end time of the de-excitation process is de-excitation total current i m A time less than 1% of the initial total current of the de-magnetoresistance;
the nominal configuration capacity of the nonlinear resistor is determined as:
i 2 is a de-excitation current flowing through the second branch circuit.
2. The combined de-reluctance circuit of claim 1 wherein the unidirectional switch is a diode or a second reverse thyristor.
3. The combined de-reluctance circuit of claim 2 wherein the jumper is electrically connected to the second reverse thyristor to control the second reverse thyristor to turn on.
4. The combined de-reluctance circuit of claim 1 wherein the linear resistor comprises a single linear resistor or a series-parallel combination of multiple linear resistors.
5. The combined de-reluctance circuit of claim 1 wherein the non-linear resistor comprises a single non-linear resistor or a series-parallel combination of a plurality of non-linear resistors.
6. The combined de-reluctance circuit of claim 1 wherein the non-linear resistor is a zinc oxide resistor.
7. An excitation system comprising a combined de-excitation resistor circuit according to any one of claims 1-6.
8. A generator set comprising the excitation system of claim 7.
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