Generator excitation system and current sharing coefficient improving method

Abstract

The invention provides a generator excitation system and a current sharing coefficient increasing method, and the system comprises an excitation transformer, a first bus, a second bus, and a plurality of rectification modules. The primary side of the exciting transformer is connected with the power output end of the generator, and the secondary side of the exciting transformer is connected with the first end of the first bus; the second bus is respectively connected with the alternating current input ends of the plurality of rectifier modules, and the direct current output ends of the plurality of rectifier modules are respectively connected with the excitation input end of the generator; aC input ends of the plurality of rectification modules are uniformly distributed along the direction from the first end to the second end of the second bus, and the second end of the first bus is connected with the middle part of the second bus. According to the generator excitation system and the current sharing coefficient increasing method disclosed by the invention, the impedance difference between the alternating current input ends of the plurality of rectification modules is reduced, and the natural current sharing coefficient of the excitation system is increased.

Description

Technical Field

[0001] This disclosure relates to the field of current sharing coefficient technology for excitation systems, and more particularly to a generator excitation system and a method for improving the current sharing coefficient. Background Technology

[0002] The current sharing performance among parallel rectifier branches in an excitation system reflects the degree of matching of the electrical parameters of each rectifier branch. Under the premise of consistent output voltage, the current sharing effect of each rectifier branch mainly depends on three key factors: the balance of the internal resistance of the parallel voltage sources, the consistency of the thyristor conduction characteristics, and the synchronization accuracy of the pulse triggering. As a core indicator for evaluating the health status of the rectifier system, the current sharing coefficient is directly related to the safe and economical operation and long-term stability of the generator set. However, currently, some excitation systems exhibit a naturally low current sharing coefficient due to differences in the incoming line structure during commissioning. Summary of the Invention

[0003] This disclosure aims to at least partially address one of the technical problems in the related art.

[0004] Therefore, the purpose of this disclosure is to provide a generator excitation system and a method for improving the current sharing coefficient.

[0005] To achieve the above objectives, the first aspect of this disclosure provides a generator excitation system, comprising: an excitation transformer, a first bus, a second bus, and a plurality of rectifier modules; wherein, the primary side of the excitation transformer is connected to the power output terminal of the generator, and the secondary side of the excitation transformer is connected to the first end of the first bus; the second bus is connected to the AC input terminals of the plurality of rectifier modules respectively, and the DC output terminals of the plurality of rectifier modules are connected to the excitation input terminal of the generator respectively; the AC input terminals of the plurality of rectifier modules are evenly distributed along the direction from the first end to the second end of the second bus, and the second end of the first bus is connected to the middle of the second bus, for reducing the impedance difference between the AC input terminals of the plurality of rectifier modules and ensuring that the natural current sharing coefficient of the excitation system is not less than a preset value.

[0006] Optionally, the plurality of rectifier modules include: a first rectifier module, a second rectifier module, and a third rectifier module; wherein, the AC input terminal of the first rectifier module is connected to the first end of the second bus, and the DC output terminal of the first rectifier module is connected to the excitation input terminal of the generator; the AC input terminal of the second rectifier module is connected to the middle part of the second bus, and the DC output terminal of the second rectifier module is connected to the excitation input terminal of the generator; the AC input terminal of the third rectifier module is connected to the second end of the second bus, and the DC output terminal of the third rectifier module is connected to the excitation input terminal of the generator.

[0007] Optionally, the system further includes: multiple cabinets arranged sequentially, with multiple rectifier modules respectively disposed within the multiple cabinets; at least one first insulating support, disposed within the cabinets, with the first busbar passing through the first insulating support.

[0008] Optionally, the system further includes: at least one second insulating support, the second insulating support being disposed within the cabinet, and the second busbar passing through the second insulating support.

[0009] Optionally, the system further includes: an AC input module, wherein the AC input module and a plurality of the rectifier modules are arranged in sequence, and the AC input module is connected in series between the secondary side of the excitation transformer and the first end of the first busbar, the AC input terminal of the AC input module is connected to the secondary side of the excitation transformer, and the AC output terminal of the AC input module is connected to the first end of the first busbar.

[0010] Optionally, the system further includes: an excitation regulation module, wherein the signal input terminal of the excitation regulation module is connected to the signal output terminal of the generator, and the control output terminal of the excitation regulation module is connected to the signal input terminals of the plurality of rectifier modules respectively.

[0011] Optionally, the system further includes: a demagnetizing switch module, which is disposed between the DC output terminals of the plurality of rectifier modules and the excitation input terminal of the generator, wherein the input terminal of the demagnetizing switch module is connected to the DC output terminals of the plurality of rectifier modules respectively, the output terminal of the demagnetizing switch module is connected to the excitation input terminal of the generator, and the signal input terminal of the demagnetizing switch module is connected to the control output terminal of the excitation regulating module.

[0012] Optionally, the system further includes: a third bus, which is connected in series between the DC output terminals of the plurality of rectifier modules and the input terminal of the demagnetizing switch module, and the third bus is connected to the DC output terminals of the plurality of rectifier modules respectively. The DC output terminals of the plurality of rectifier modules are distributed at intervals along the direction from the first end to the second end of the third bus, and the second end of the third bus is connected to the input terminal of the demagnetizing switch module.

[0013] A second aspect of this disclosure provides a method for improving the current sharing coefficient. The excitation system includes: an excitation transformer, a second bus, and multiple rectifier modules. The primary side of the excitation transformer is connected to the power output terminal of a generator, and the secondary side of the excitation transformer is connected to the first end of the second bus. The second bus is connected to the AC input terminals of the multiple rectifier modules, which are uniformly distributed along the direction from the first end to the second end of the second bus. The DC output terminals of the multiple rectifier modules are connected to the excitation input terminal of the generator. The method includes: acquiring the DC output current of the multiple rectifier modules and obtaining the natural current sharing coefficient of the excitation system based on the multiple output currents; when the natural current sharing coefficient of the excitation system is less than a preset value, disconnecting the connection between the secondary side of the excitation transformer and the first end of the second bus; and arranging a first bus between the secondary side of the excitation transformer and the middle of the second bus to reduce the impedance difference between the AC input terminals of the multiple rectifier modules and ensure that the natural current sharing coefficient of the excitation system is not less than the preset value.

[0014] Optionally, the method further includes: when the natural current sharing coefficient of the excitation system is less than a preset value, obtaining an equivalent circuit based on the generator, the excitation transformer, and the plurality of rectifier modules; determining the impedance difference between the AC input terminals of the plurality of rectifier modules based on the equivalent circuit and the same AC side input voltage and the same thyristor on-state voltage drop between the plurality of rectifier modules; and disconnecting the connection between the secondary side of the excitation transformer and the first terminal of the second bus based on the impedance difference between the AC input terminals of the plurality of rectifier modules, and arranging the first bus between the secondary side of the excitation transformer and the middle of the second bus.

[0015] The technical solution provided in this disclosure may include the following beneficial effects:

[0016] Since the AC input terminals of multiple rectifier modules are evenly distributed along the direction from the first end to the second end of the second busbar, and the second end of the first busbar is connected to the middle of the second busbar, the current path length between the secondary side of the excitation transformer and the AC input terminals of each rectifier module is more balanced. This reduces the impedance difference between the AC input terminals of multiple rectifier modules, improves the natural current sharing coefficient of the excitation system, and thus ensures the safe and economical operation and long-term stability of the generator.

[0017] Additional aspects and advantages of this disclosure will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this disclosure. Attached Figure Description

[0018] The above and / or additional aspects and advantages of this disclosure will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, in which:

[0019] Figure 1 This is a circuit diagram of a generator excitation system according to an embodiment of the present disclosure (without the first busbar).

[0020] Figure 2 This is a schematic diagram of the structure at the first busbar in a generator excitation system according to an embodiment of this disclosure;

[0021] Figure 3 This is an equivalent circuit diagram proposed in one embodiment of the present disclosure;

[0022] As shown in the figure: 1. First busbar, 2. Second busbar, 3. First rectifier module, 4. Second rectifier module, 5. Third rectifier module, 6. Cabinet, 7. First insulating support base, 8. AC incoming line module, 9. Excitation regulation module, 10. Demagnetizing switch module, 11. Third busbar. Detailed Implementation

[0023] Embodiments of this disclosure are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are used only to explain this disclosure, and should not be construed as limiting this disclosure. Rather, embodiments of this disclosure include all variations, modifications, and equivalents falling within the spirit and scope of the appended claims.

[0024] like Figure 1 and Figure 2 As shown in the figure, this disclosure proposes a generator excitation system, including: an excitation transformer (not shown), a first bus 1, a second bus 2, and multiple rectifier modules. The primary side of the excitation transformer is connected to the power output terminal of the generator, and the secondary side of the excitation transformer is connected to the first end of the first bus 1. The second bus 2 is connected to the AC input terminals of the multiple rectifier modules, and the DC output terminals of the multiple rectifier modules are connected to the excitation input terminal of the generator. The AC input terminals of the multiple rectifier modules are evenly distributed along the direction from the first end to the second end of the second bus 2, and the second end of the first bus 1 is connected to the middle of the second bus 2. This arrangement is used to reduce the impedance difference between the AC input terminals of the multiple rectifier modules and to ensure that the natural current sharing coefficient of the excitation system is not less than a preset value.

[0025] Understandably, since the excitation transformer, the first busbar 1, the second busbar 2, multiple rectifier modules, and the generator are connected in sequence, the electrical energy provided by the generator can pass through the excitation transformer and multiple rectifier modules in sequence. This allows the excitation current to be provided to the generator by utilizing the voltage transformation of the excitation transformer and the rectification of the multiple rectifier modules, thereby achieving self-excitation control and ensuring the stable operation of the generator. At the same time, since the AC input terminals of the multiple rectifier modules are evenly distributed along the direction from the first end to the second end of the second busbar 2, and the second end of the first busbar 1 is connected to the middle of the second busbar 2, the current path length between the secondary side of the excitation transformer and the AC input terminals of each rectifier module is more balanced. This reduces the impedance difference between the AC input terminals of the multiple rectifier modules, improves the natural current sharing coefficient of the excitation system, and thus ensures the safe and economical operation and long-term stability of the generator.

[0026] It should be noted that the excitation system is based on excitation control, which controls the generator output voltage, reactive power and power system stability by adjusting the rotor excitation current. It is the core component for the stable operation of synchronous generators.

[0027] The excitation transformer utilizes the stator current of the generator, in conjunction with the rectifier module, to provide excitation current to the rotor of the generator. The specific type of excitation transformer can be set according to actual needs, and there are no restrictions on it.

[0028] The rectifier module is used to rectify the AC power transformed by the excitation transformer into DC power to provide excitation current to the generator rotor. The specific type of rectifier module can be set according to actual needs and is not limited thereto. The rectifier module is an integrated rectifier circuit based on devices such as thyristors and IGBTs.

[0029] The first busbar 1 and the second busbar 2 are used to realize the current transmission between the secondary side of the excitation transformer and multiple rectifier modules. In the relevant embodiments, the secondary side of the excitation transformer and the first end of the second busbar 2 are directly connected. As a result, the rectifier module closer to the first end of the second busbar 2 has a smaller AC impedance and a larger output current, while the rectifier module closer to the second end of the second busbar 2 has a larger AC impedance and a smaller output current, resulting in a lower natural current sharing coefficient.

[0030] For example, during the operation of the three rectifier modules, the natural current sharing coefficient is approximately 0.85 under no-load rated excitation current and approximately 0.867 under 80% load conditions. The industry standard DL / T 583—2018 "Technical Conditions for Static Rectifier Excitation Systems of Large and Medium-Sized Hydropower Generators" stipulates that "under the rated operating conditions of the generator, the current sharing coefficient of the parallel rectifier bridge should not be lower than 0.9; under no-load rated conditions, the current sharing coefficient of the parallel rectifier bridge should not be lower than 0.85."

[0031] By utilizing the arrangement of the first busbar 1, the current path of the AC input terminal of the rectifier module is adjusted, making the current path length between the secondary side of the excitation transformer and the AC input terminal of each rectifier module more balanced, thereby effectively improving the natural current sharing coefficient of the excitation system.

[0032] Since the first busbar 1 and the second busbar 2 need to transmit AC power, each of the first busbar 1 and the second busbar 2 is provided with three mutually insulated and isolated paths. The specific types of the first busbar 1 and the second busbar 2 can be set according to actual needs and there are no restrictions on this. For example, the second busbar 2 is a straight-line structure, and the first busbar 1 needs to cross a part of the rectifier module and connect to the middle of the second busbar 2, which can be arranged as a U-shaped structure.

[0033] The second end of the first busbar 1 is connected to the middle of the second busbar 2. When the number of rectifier modules is odd, the middle of the second busbar 2 is the middle rectifier module among the multiple rectifier modules placed side by side. When the number of rectifier modules is even, the middle of the second busbar 2 is between the two middle rectifier modules among the multiple rectifier modules placed side by side.

[0034] like Figure 1 As shown, in some embodiments, the plurality of rectifier modules include: a first rectifier module 3, a second rectifier module 4, and a third rectifier module 5. The AC input terminal of the first rectifier module 3 is connected to the first terminal of the second bus 2, and the DC output terminal of the first rectifier module 3 is connected to the excitation input terminal of the generator. The AC input terminal of the second rectifier module 4 is connected to the middle portion of the second bus 2, and the DC output terminal of the second rectifier module 4 is connected to the excitation input terminal of the generator. The AC input terminal of the third rectifier module 5 is connected to the second terminal of the second bus 2, and the DC output terminal of the third rectifier module 5 is connected to the excitation input terminal of the generator.

[0035] It is understandable that by utilizing the first rectifier module 3, the second rectifier module 4, and the third rectifier module 5, the AC current on the secondary side of the excitation transformer is rectified, thereby providing a stable excitation current for the generator. Furthermore, since the AC input terminal of the first rectifier module 3 is connected to the first end of the second bus 2, the AC input terminal of the second rectifier module 4 is connected to the middle of the second bus 2, and the AC input terminal of the third rectifier module 5 is connected to the second end of the second bus 2, the current path lengths between the secondary side of the excitation transformer and the AC input terminals of the first rectifier module 3, the second rectifier module 4, and the third rectifier module 5 are more balanced. This reduces the impedance difference between the AC input terminals of the first rectifier module 3, the second rectifier module 4, and the third rectifier module 5, improves the natural current sharing coefficient of the excitation system, and thus ensures the safe and economical operation and long-term stability of the generator.

[0036] It should be noted that the first rectifier module 3, the second rectifier module 4 and the third rectifier module 5 are all rectifier modules, which are arranged side by side in the cabinet 6. The first rectifier module 3 and the third rectifier module 5 are located at the two ends of the second bus 2, and the second rectifier module 4 is located in the middle of the second bus 2.

[0037] like Figure 2 As shown, in some embodiments, the system further includes: multiple cabinets 6 and at least one first insulating support 7, the multiple cabinets 6 are arranged in sequence, and multiple rectifier modules are respectively disposed in the multiple cabinets 6, the first insulating support 7 is disposed in the cabinets 6, and the first busbar 1 passes through the first insulating support 7.

[0038] It is understandable that the rectifier modules are arranged in the cabinet 6 to form a rectifier cabinet, which facilitates the overall layout and protection. Furthermore, by using at least one first insulating support 7, the first busbar 1 can be effectively supported, thereby ensuring the stable operation of multiple rectifier modules.

[0039] It should be noted that cabinet 6 is used for the integration and protection of rectifier modules. The specific type of cabinet 6 can be set according to actual needs and there are no restrictions. For example, cabinet 6 is a cabinet structure with cabinet doors, and the interior is equipped with crossbeams, longitudinal beams, back panels, etc. for rectifier modules.

[0040] The first insulating support 7 is used to support the first busbar 1. The specific type of the first insulating support 7 can be set according to actual needs and is not limited thereto. For example, the first insulating support 7 is made of insulating material and is provided with through holes for the first busbar 1 to pass through. Since the first busbar 1 has three cablings, the first insulating support 7 is also provided with three corresponding through holes.

[0041] The number of first insulating support seats 7 can be set according to actual needs and there is no limit to it. For example, when there are three rectifier modules, the overall length of the first busbar 1 is relatively short, so two first insulating support seats 7 can be set to support the two ends of the first busbar 1 respectively.

[0042] In some embodiments, the system further includes at least one second insulating support, the second insulating support being disposed within the cabinet 6, and the second busbar 2 passing through the second insulating support.

[0043] It is understandable that by using at least one second insulating support, the second busbar 2 can be effectively supported, thereby ensuring the stable operation of multiple rectifier modules.

[0044] It should be noted that the second insulating support is used to support the second busbar 2. The specific type of the second insulating support can be set according to actual needs and is not limited thereto. For example, the second insulating support is made of insulating material and is provided with through holes or slots for the second busbar 2 to pass through. Since the second busbar 2 has three cablings, the second insulating support is also provided with three corresponding through holes or slots.

[0045] like Figure 1 As shown, in some embodiments, the system further includes: an AC input module 8, the AC input module 8 and a plurality of rectifier modules are arranged in sequence, and the AC input module 8 is connected in series between the secondary side of the excitation transformer and the first end of the first bus 1. The AC input terminal of the AC input module 8 is connected to the secondary side of the excitation transformer, and the AC output terminal of the AC input module 8 is connected to the first end of the first bus 1.

[0046] It is understandable that, since the AC input terminal of the AC input module 8 is connected to the secondary side of the excitation transformer, and the AC output terminal of the AC input module 8 is connected to the first end of the first bus 1, the AC input module 8 can be used to switch between the secondary side of the excitation transformer and the first end of the first bus 1. Furthermore, the AC input module 8 and multiple rectifier modules are arranged in sequence, which not only saves space and facilitates the layout, but also achieves a high natural current sharing coefficient by utilizing the wiring structure of the first bus 1.

[0047] It should be noted that the AC incoming module 8 is used for current transfer between the secondary side of the excitation transformer and the first terminal of the first busbar 1. The specific type of the AC incoming module 8 can be set according to actual needs and is not limited thereto. The AC incoming module 8, together with the cabinet 6, forms an AC incoming cabinet.

[0048] like Figure 1 As shown, in some embodiments, the system further includes an excitation regulation module 9, the signal input terminal of which is connected to the signal output terminal of the generator, and the control output terminal of the excitation regulation module 9 is connected to the signal input terminals of multiple rectifier modules respectively.

[0049] Understandably, since the signal input terminal of the excitation regulation module 9 is connected to the signal output terminal of the generator, and the control output terminal of the excitation regulation module 9 is connected to the signal input terminals of multiple rectifier modules respectively, the excitation regulation module 9 can use the generator's output signal to control multiple rectifier modules to regulate the excitation current, thereby achieving excitation control and ensuring the stable operation of the generator.

[0050] It should be noted that the excitation regulation module 9 is the core control unit of the excitation system, responsible for maintaining the stability of the generator terminal voltage, regulating reactive power, and participating in the stability control of the power system. The specific type of the excitation regulation module 9 can be set according to actual needs, and there are no restrictions on it.

[0051] The excitation regulation module 9 can be arranged on the side of the AC input module 8 away from the rectifier module.

[0052] like Figure 1 As shown, in some embodiments, the system further includes: a demagnetizing switch module 10, which is disposed between the DC output terminals of multiple rectifier modules and the excitation input terminal of the generator, and the input terminal of the demagnetizing switch module 10 is connected to the DC output terminals of the multiple rectifier modules respectively, the output terminal of the demagnetizing switch module 10 is connected to the excitation input terminal of the generator, and the signal input terminal of the demagnetizing switch module 10 is connected to the control output terminal of the excitation regulating module 9.

[0053] Understandably, since the input terminal of the demagnetizing switch module 10 is connected to the DC output terminal of multiple rectifier modules, the output terminal of the demagnetizing switch module 10 is connected to the excitation input terminal of the generator, and the signal input terminal of the demagnetizing switch module 10 is connected to the control output terminal of the excitation regulating module 9, the demagnetizing switch module 10 can effectively protect the excitation system under the control of the excitation regulating module 9.

[0054] It should be noted that the demagnetizing switch module 10 is the "safety gate" of the excitation system, and its reliability and response speed are directly related to the safety of the generator and the power grid. The specific type of the demagnetizing switch module 10 can be set according to actual needs and is not limited thereto. The demagnetizing switch module 10 may include: a demagnetizing switch, a demagnetizing resistor, an overvoltage protector, etc.

[0055] like Figure 1 As shown, in some embodiments, the system further includes a third bus 11, which is connected in series between the DC output terminals of multiple rectifier modules and the input terminal of the demagnetizing switch module 10. The third bus 11 is connected to the DC output terminals of multiple rectifier modules respectively. The DC output terminals of the multiple rectifier modules are distributed at intervals along the direction from the first end to the second end of the third bus 11. The second end of the third bus 11 is connected to the input terminal of the demagnetizing switch module 10.

[0056] It is understandable that since the third bus 11 is connected to the DC output terminals of multiple rectifier modules respectively, and the second end of the third bus 11 is connected to the input terminal of the demagnetizing switch module 10, current can be transmitted between the DC output terminals of multiple rectifier modules and the input terminal of the demagnetizing switch module 10 through the third bus 11, thereby ensuring the stable operation of the excitation system.

[0057] It should be noted that the third bus 11 is used for current transmission between the DC output terminals of multiple rectifier modules and the input terminal of the demagnetizing switch module 10. Since the third bus 11 needs to transmit DC power, it is arranged with two mutually insulated and isolated paths. The specific type of the third bus 11 can be set according to actual needs and there are no restrictions on it.

[0058] The secondary side of the excitation transformer uses 18 185mm rods. 2 The cable connects to the AC incoming module 8, and the output of the demagnetizing switch module 10 uses 12 185mm² cables. 2 The cable is connected to the generator, with 6 cables in each row.

[0059] In the relevant embodiments, the excitation system includes: an excitation transformer, a second bus 2, and multiple rectifier modules. The primary side of the excitation transformer is connected to the power output terminal of the generator, and the secondary side of the excitation transformer is connected to the first end of the second bus 2. The second bus 2 is connected to the AC input terminals of the multiple rectifier modules, which are evenly distributed along the direction from the first end to the second end of the second bus 2. The DC output terminals of the multiple rectifier modules are connected to the excitation input terminal of the generator.

[0060] This disclosure also proposes a method for improving the flow equalization coefficient, including:

[0061] S1: Collect the DC output current of multiple rectifier modules and obtain the natural current sharing coefficient of the excitation system based on the multiple output currents;

[0062] S2: When the natural current sharing coefficient of the excitation system is less than the preset value, disconnect the connection between the secondary side of the excitation transformer and the first end of the second bus 2.

[0063] S3: Arrange the first busbar 1 between the secondary side of the excitation transformer and the middle of the second busbar 2 to reduce the impedance difference between the AC input terminals of multiple rectifier modules and to ensure that the natural current sharing coefficient of the excitation system is not less than the preset value.

[0064] It is understandable that by disconnecting the connection between the secondary side of the excitation transformer and the first end of the second busbar 2, and arranging the first busbar 1 between the secondary side of the excitation transformer and the middle of the second busbar 2, the current path length between the secondary side of the excitation transformer and the AC input terminals of each rectifier module is more balanced. This reduces the impedance difference between the AC input terminals of multiple rectifier modules, improves the natural current sharing coefficient of the excitation system, and thus ensures the safe and economical operation and long-term stability of the generator.

[0065] In some embodiments, the method further includes:

[0066] When the natural current sharing coefficient of the excitation system is less than the preset value, an equivalent circuit is obtained based on the generator, excitation transformer and multiple rectifier modules;

[0067] Based on the equivalent circuit and the same AC side input voltage and the same thyristor on-state voltage drop among multiple rectifier modules, the impedance difference between the AC input terminals of multiple rectifier modules is determined.

[0068] Based on the impedance difference between the AC input terminals of multiple rectifier modules, the connection between the secondary side of the excitation transformer and the first terminal of the second busbar 2 is cut off, and the first busbar 1 is arranged between the secondary side of the excitation transformer and the middle part of the second busbar 2.

[0069] Specifically, the generator, excitation transformer, and three parallel-operating rectifier modules form three parallel voltage sources. The output of the rectifier modules and the generator rotor form the load, and the output current of the rectifier modules is inversely proportional to the impedance of each parallel branch.

[0070] Equivalent circuit such as Figure 3 As shown, where the voltage source US1i represents the magnitude of the output voltage of the i-th rectifier module, US2i represents the average on-state voltage drop of the thyristor in the i-th rectifier module, Ri represents the equivalent resistance of the AC / DC circuit of the i-th rectifier module, Li represents the equivalent inductance (including self-inductance and mutual inductance) of the AC / DC circuit of the i-th rectifier module, R represents the resistance of the generator rotor circuit, and L represents the inductance of the generator rotor circuit.

[0071] The consistency of thyristor triggering ensures that the value of US1i in the equivalent circuit of different thyristor rectifier modules is equal. The on-state voltage drop of the thyristor determines the value of US2i, while the diode Di indicates that the current in the thyristor circuit has directionality.

[0072] Since the rectifier modules share a single excitation transformer, their AC input voltages are equal. Simultaneously, the on-state voltage drop of the thyristors in each phase of the three rectifier modules is almost identical. Therefore, the difference in the equivalent impedance of the AC circuit becomes the primary factor in current sharing among the rectifier modules, thus determining the effectiveness of current sharing among them.

[0073] Therefore, the connection between the secondary side of the excitation transformer and the first end of the second busbar 2 is cut off, and the first busbar 1 is arranged between the secondary side of the excitation transformer and the middle of the second busbar 2. Thus, by modifying the incoming line structure, the current sharing coefficient is improved.

[0074] During the renovation process, the existing second busbar 2 needs to be drilled to connect the newly added first busbar 1. The side door panels of the three rectifier cabinets need to be removed in front of the cabinets in order to install the newly added first busbar 1. The horizontal cable strips inside the cabinets need to be cut in order to install the newly added first busbar 1.

[0075] In addition, it is important to note that the ends of dismantled cables must be wrapped with insulating tape and must not be exposed; fireproof blankets should be laid around the cabinet and industrial vacuum cleaners should be provided to prevent the spread of metal shavings; bolts and washers should be managed using transparent tool bags and counted daily to prevent them from being left inside the cabinet; equipment inside the cabinet should be covered with dust covers in advance to prevent metal shavings from entering; bolt connection torque must meet the standard (78.5-98.1 (N·m)).

[0076] Preventive measures: The equipment inside the cabinet is wrapped with dust covers in advance, fireproof blankets are laid around the cabinet, and industrial vacuum cleaners are provided to prevent the spread of metal shavings.

[0077] After improving natural flow equalization by adding busbars, the flow equalization coefficient increased from 0.84 to 0.97.

[0078] It should be noted that in the description of this disclosure, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, in the description of this disclosure, unless otherwise stated, "a plurality of" means two or more.

[0079] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process, and the scope of preferred embodiments of this disclosure includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the function involved, as will be understood by those skilled in the art to which embodiments of this disclosure pertain.

[0080] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this disclosure. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0081] Although embodiments of the present disclosure have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present disclosure. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present disclosure.

Claims

1. A generator excitation system, characterized in that, include: Excitation transformer, first busbar, second busbar, and multiple rectifier modules; The primary side of the excitation transformer is connected to the power output terminal of the generator, and the secondary side of the excitation transformer is connected to the first end of the first busbar. The second busbar is connected to the AC input terminals of the plurality of rectifier modules respectively, and the DC output terminals of the plurality of rectifier modules are connected to the excitation input terminal of the generator respectively. The AC input terminals of the plurality of rectifier modules are evenly distributed along the direction from the first end to the second end of the second bus, and the second end of the first bus and the middle part of the second bus are connected to reduce the impedance difference between the AC input terminals of the plurality of rectifier modules and ensure that the natural current sharing coefficient of the excitation system is not less than a preset value.

2. The generator excitation system according to claim 1, characterized in that, The plurality of rectifier modules include: The first rectifier module, the second rectifier module, and the third rectifier module; The AC input terminal of the first rectifier module is connected to the first terminal of the second bus, and the DC output terminal of the first rectifier module is connected to the excitation input terminal of the generator. The AC input terminal of the second rectifier module is connected to the middle of the second bus, and the DC output terminal of the second rectifier module is connected to the excitation input terminal of the generator. The AC input terminal of the third rectifier module is connected to the second terminal of the second bus, and the DC output terminal of the third rectifier module is connected to the excitation input terminal of the generator.

3. The generator excitation system according to claim 1, characterized in that, The system also includes: Multiple server racks are arranged sequentially, and multiple rectifier modules are respectively installed in multiple server racks; At least one first insulating support is provided inside the cabinet, and the first busbar passes through the first insulating support.

4. The generator excitation system according to claim 3, characterized in that, The system also includes: At least one second insulating support is provided inside the cabinet, and the second busbar passes through the second insulating support.

5. The generator excitation system according to claim 1, characterized in that, The system also includes: An AC input module and multiple rectifier modules are arranged in sequence. The AC input module is connected in series between the secondary side of the excitation transformer and the first end of the first busbar. The AC input terminal of the AC input module is connected to the secondary side of the excitation transformer, and the AC output terminal of the AC input module is connected to the first end of the first busbar.

6. The generator excitation system according to claim 1, characterized in that, The system also includes: The excitation regulation module has its signal input terminal connected to the signal output terminal of the generator, and its control output terminal is connected to the signal input terminals of the plurality of rectifier modules respectively.

7. The generator excitation system according to claim 6, characterized in that, The system also includes: A demagnetizing switch module is provided, wherein the demagnetizing switch module is disposed between the DC output terminals of the plurality of rectifier modules and the excitation input terminal of the generator, and the input terminal of the demagnetizing switch module is connected to the DC output terminals of the plurality of rectifier modules respectively, the output terminal of the demagnetizing switch module is connected to the excitation input terminal of the generator, and the signal input terminal of the demagnetizing switch module is connected to the control output terminal of the excitation regulating module.

8. The generator excitation system according to claim 7, characterized in that, The system also includes: The third busbar is connected in series between the DC output terminals of the plurality of rectifier modules and the input terminal of the demagnetizing switch module. The third busbar is connected to the DC output terminals of the plurality of rectifier modules respectively. The DC output terminals of the plurality of rectifier modules are distributed at intervals along the direction from the first end to the second end of the third busbar. The second end of the third busbar is connected to the input terminal of the demagnetizing switch module.

9. A method for improving the flow equalization coefficient, characterized in that, The excitation system includes: an excitation transformer, a second busbar, and multiple rectifier modules. The primary side of the excitation transformer is connected to the power output terminal of the generator, and the secondary side of the excitation transformer is connected to the first end of the second busbar. The second busbar is connected to the AC input terminals of the multiple rectifier modules, which are evenly distributed along the direction from the first end to the second end of the second busbar. The DC output terminals of the multiple rectifier modules are connected to the excitation input terminal of the generator. The method includes: The DC output current of multiple rectifier modules is collected, and the natural current sharing coefficient of the excitation system is obtained based on the multiple output currents; When the natural current-equalizing coefficient of the excitation system is less than a preset value, the connection between the secondary side of the excitation transformer and the first end of the second busbar is cut off. A first busbar is arranged between the secondary side of the excitation transformer and the middle of the second busbar to reduce the impedance difference between the AC input terminals of the multiple rectifier modules and to ensure that the natural current sharing coefficient of the excitation system is not less than the preset value.

10. The method for improving the flow equalization coefficient according to claim 9, characterized in that, The method further includes: When the natural current sharing coefficient of the excitation system is less than a preset value, an equivalent circuit is obtained based on the generator, the excitation transformer and the multiple rectifier modules; Based on the equivalent circuit and the same AC side input voltage and the same silicon controlled rectifier on-state voltage drop among the multiple rectifier modules, the impedance difference between the AC input terminals of the multiple rectifier modules is determined; Based on the impedance difference between the AC input terminals of the multiple rectifier modules, the connection between the secondary side of the excitation transformer and the first terminal of the second bus is cut off, and the first bus is arranged between the secondary side of the excitation transformer and the middle of the second bus.

Images