Hybrid excitation device, control device and control method thereof, and power generation system

Abstract

The invention discloses a hybrid excitation device, a control device and a control method thereof, and a power generation system, the hybrid excitation device comprises a first three-phase rectification circuit and a second three-phase rectification circuit, the direct current side of the first three-phase rectification circuit and the direct current side of the second three-phase rectification circuit are connected with an excitation winding of a power generator to form a first channel; under the control of the second switching signal, reactive power is indirectly absorbed or injected into the power grid through the generator; the alternating current end of the second three-phase rectifying circuit is connected with the generator end to form a second channel, and reactive power is directly absorbed or injected into the power grid under the control of the first switching signal. According to the technical scheme, the excitation current control capability of the power generation system and the capability of providing reactive power support for a power grid can be improved, so that the influences of short-circuit faults, open-circuit faults, voltage fluctuation and the like of an alternating-current system are greatly reduced, and the reliability of the power generation system is improved.

Description

Technical Field

[0001] The present invention belongs to the field of electric power systems, and in particular relates to a hybrid excitation device and a control device and a control method thereof, and a power generation system based on the hybrid excitation device. Background Art

[0002] With the expansion of the scale of power systems, the emergence of long-distance heavy-load transmission lines, and the widespread use of fast excitation systems for large generators, while achieving optimal allocation of power resources and improving the economy and reliability of system generation and transmission, a series of new problems have also been brought about. The most prominent manifestation is the power oscillation between large areas due to insufficient damping of the interconnected system. At the same time, there is also a decline in the dynamic reactive power compensation capacity in some areas, and insufficient system damping, which poses a serious threat to the safe and stable operation of the power grid. The excitation system of the generator has an important impact on improving stability. Among the many measures to improve stability (such as fast valve closing, resistor braking, series-parallel compensation, etc.), the excitation system control has the highest benefit-to-investment ratio and is the preferred measure.

[0003] The traditional self-parallel excitation system may cause the voltage drop at the machine end or even cause the generator to lose magnetism when a fault occurs. In response to the problem of grid voltage sag, the traditional excitation system affects the grid voltage by injecting or absorbing reactive current. This method of controlling voltage is lacking in accuracy and speed and cannot meet the requirements of sensitive power loads for power quality. In response to the problem of system reactive power and insufficient damping, it is objectively required to increase the capacity of grid reactive compensation. SVC (static varcompensator) and STATCOM (static synchronous compensator) and synchronous condensers are all commonly used reactive compensation devices. Among them, synchronous condensers have more superior performance, especially their short-term overload capacity has a strong supporting effect on the system voltage under fault conditions. Due to the large workload of operation and maintenance and high power loss, the annual operating cost of synchronous condensers is relatively high. In addition, the traditional self-shunt excitation system adopts thyristor rectification, and the thyristor phase change method will generate a large amount of harmonics. Harmonics will not only affect the normal operation of electrical equipment, but also cause harmonic interference to adjacent equipment. At the same time, phase shift control causes the current to lag behind the voltage phase, resulting in a decrease in power factor and deterioration of power quality. Summary of the invention

[0004] The purpose of the present invention is to provide a hybrid excitation device and its control device, control method, and power generation system, which can improve the excitation current control capability of the power generation system and the ability to provide reactive power support to the power grid, so as to significantly reduce the impact of short-circuit faults, open-circuit faults, and voltage fluctuations in the AC system, and improve the reliability of the power generation system.

[0005] In order to achieve the above object, the solution of the present invention is:

[0006] A hybrid excitation device comprises a first three-phase rectifier circuit and a second three-phase rectifier circuit, wherein the DC side output end of the first three-phase rectifier circuit is connected to the first end of the generator excitation winding, and the AC side of the first three-phase rectifier circuit is connected to the generator end through a first excitation transformer; the DC side output end of the second three-phase rectifier circuit is connected to the second end of the generator excitation winding, and the AC side of the second three-phase rectifier circuit is connected to the generator end through a second excitation transformer; the DC side negative and positive poles of the first three-phase rectifier circuit are connected in series with the DC side positive and negative poles of the second three-phase rectifier circuit; based on this, the DC sides of the first and second three-phase rectifier circuits are connected to the excitation winding of the generator to form a first channel, and reactive power is indirectly absorbed or injected into the power grid through the generator under the control of a second switch signal; at the same time, the AC end of the second three-phase rectifier circuit is connected to the generator end to form a second channel, and reactive power is directly absorbed or injected into the power grid under the control of the first switch signal.

[0007] The above-mentioned first three-phase rectifier circuit adopts a three-phase bridge arm structure based on thyristors, and each phase bridge arm includes two thyristors, which are recorded as a first thyristor and a second thyristor; the cathode of the first thyristor serves as the first end of the bridge arm, the anode of the first thyristor is connected to the cathode of the second thyristor as the midpoint of the bridge arm, and the anode of the second thyristor serves as the second end of the bridge arm; in the first three-phase rectifier circuit, the first end of the three-phase bridge arm is connected as the negative electrode of the three-phase rectifier circuit, the second end of the three-phase bridge arm is connected as the positive electrode of the three-phase rectifier circuit, the midpoint of the three-phase bridge arm serves as the output end, and the gate of each thyristor is used to receive the second switching signal.

[0008] The above-mentioned second three-phase rectifier circuit adopts a three-phase bridge arm structure, and each phase bridge arm includes an IGBT with two parallel diodes, which are denoted as the first IGBT and the second IGBT; the emitter and collector of each IGBT are respectively connected to the positive and negative electrodes of the diodes connected in parallel; the collector of the first IGBT serves as the first end of the bridge arm, the emitter of the first IGBT is connected to the collector of the second IGBT as the midpoint of the bridge arm, and the emitter of the second IGBT serves as the second end of the bridge arm; in the second three-phase rectifier circuit, the first end of the three-phase bridge arm is connected as the positive electrode of the three-phase rectifier circuit, the second end of the three-phase bridge arm is connected as the negative electrode of the three-phase rectifier circuit, the midpoint of the three-phase bridge arm serves as the output end, and the gate of each IGBT is used to receive the first and second switching signals.

[0009] The second three-phase rectifier circuit and the first three-phase rectifier circuit are also connected via a switch array as a transition, that is, the second three-phase rectifier circuit is directly connected to the switch array, and the positive and negative poles of the switch array are respectively connected to the negative and positive poles of the first three-phase rectifier circuit.

[0010] The control device of the hybrid excitation device as mentioned above comprises a direct reactive power control module and an indirect reactive power control module;

[0011] The direct reactive power control module is used to provide a first switch signal to the second three-phase rectifier circuit to control the opening and closing of the fully controlled components in the second three-phase rectifier circuit, so that the reactive power directly absorbed or injected into the power grid by the hybrid excitation device through the second channel is equal to the direct reactive power command value;

[0012] The indirect reactive power control module is used to provide a second switching signal to the first three-phase rectifier circuit and the second three-phase rectifier circuit, control the opening and closing of each controllable device in the first three-phase rectifier circuit and the second three-phase rectifier circuit, so that the reactive power indirectly absorbed or injected into the power grid by the hybrid excitation device through the first channel is equal to the indirect reactive power command value.

[0013] The direct reactive power control module obtains a first switch signal according to the reactive power feedback value directly absorbed or injected into the power grid by the hybrid excitation device through the second channel and the direct reactive power command value, so as to control the disconnection of the fully controlled device in the second three-phase rectifier circuit, so that the reactive power directly absorbed or injected into the power grid by the hybrid excitation device through the second channel is equal to the direct reactive power command value;

[0014] The indirect reactive power control module obtains a second switching signal based on the reactive power feedback value and the indirect reactive power command value indirectly absorbed or injected into the power grid by the hybrid excitation device through the first channel to control the opening and closing of each controllable device in the first three-phase rectifier circuit and the second three-phase rectifier circuit, so that the reactive power indirectly absorbed or injected into the power grid by the hybrid excitation device through the first channel is equal to the indirect reactive power command value.

[0015] The control method of the hybrid excitation device as mentioned above includes:

[0016] The first switch signal is used to control the opening and closing of the fully controlled devices in the second three-phase rectifier circuit, so that the reactive power directly absorbed or injected into the power grid by the hybrid excitation device through the second channel is equal to the direct reactive power command value;

[0017] The second switch signal is used to control the opening and closing of each controllable device in the first three-phase rectifier circuit and the second three-phase rectifier circuit, so that the reactive power indirectly absorbed or injected into the power grid by the hybrid excitation device through the first channel is equal to the indirect reactive power command value.

[0018] The method for obtaining the first switch signal is to obtain, from the generator end, a reactive power feedback value directly absorbed or injected into the power grid by the hybrid excitation device through the second channel, and obtain the first switch signal according to the reactive power feedback value and the direct reactive power command value;

[0019] The method for obtaining the second switching signal is to obtain from the generator end a reactive power feedback value indirectly absorbed or injected into the power grid by the hybrid excitation device through the first channel, and obtain the second switching signal based on the reactive power feedback value and the indirect reactive power command value.

[0020] The direct reactive power command value and the indirect reactive power command value are obtained by dividing the reactive power command value according to a preset ratio, and the direct reactive power command value is smaller than the indirect reactive power command value.

[0021] A power generation system comprises a generator and a main transformer, wherein the generator end is connected to a power grid via the main transformer; and further comprises the hybrid excitation device as described above.

[0022] After adopting the above scheme, the present invention can achieve the following beneficial effects:

[0023] (1) In the present invention, the hybrid excitation device included in the power generation system has two channels, one of which can quickly provide reactive power support to the power grid, and the other channel can provide greater and more stable reactive power support to the power grid. The two channels work together to improve the ability to provide reactive power support to the power grid, reduce the use of synchronous phase regulators in the power grid, and reduce the operating costs of the power grid.

[0024] (2) In the present invention, the hybrid excitation device included in the power generation system has two channels, one of which can provide excitation current for the generator, thereby improving the excitation current control capability of the power generation system and preventing the excitation current from decreasing and causing the excitation capability of the generator to decrease when a power grid fault occurs, thereby preventing the terminal voltage from decreasing and improving the reliability of the power generation system.

[0025] (3) In the present invention, the first three-phase rectifier circuit and the second three-phase rectifier circuit are connected in series on the DC side to jointly bear the excitation voltage. The addition of the second three-phase rectifier circuit improves the operating environment of the first three-phase rectifier circuit, improves the excitation capacity of the system, and enables the system to operate more safely and reliably.

[0026] (4) In the present invention, the first three-phase rectifier circuit and the second three-phase rectifier circuit are connected in series on the AC side. The addition of the second three-phase rectifier can provide reactive power support for the system more quickly, maintain voltage stability, and provide harmonic current compensation, thereby improving system stability while improving power quality, which is of great benefit to improving the stability of the excitation and power generation systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of a power generation system based on a hybrid excitation device provided by the present invention;

[0028] Figure 2 is a schematic diagram of a hybrid excitation device provided by an embodiment of the present invention;

[0029] Figure 3 This is the preferred rectifier bridge structure provided by the embodiment of the present invention;

[0030] Among them, (a) is the structure of the first three-phase rectifier circuit, (b) is the structure of the second three-phase rectifier circuit, and (c) is the structure in which the first and second three-phase rectifier circuits are connected through a switch array. DETAILED DESCRIPTION

[0031] The technical solutions and beneficial effects of the present invention will be described in detail below with reference to the accompanying drawings.

[0032] In order to further improve the excitation current control capability of the power generation system and the ability to provide reactive support to the power grid, the present invention provides a hybrid excitation device and a control method thereof. The overall idea is: on the basis of the traditional excitation device, a new channel is added to directly absorb or inject reactive power into the power grid and provide excitation current to the generator through voltage compensation. Finally, the two channels in the hybrid excitation device operate in coordination to effectively improve the excitation current control capability of the power generation system and the ability to provide reactive support to the power grid.

[0033] like Figure 2 As shown, an embodiment of the present invention provides a hybrid excitation device, including a first three-phase rectifier circuit and a second three-phase rectifier circuit, wherein the DC side output end of the first three-phase rectifier circuit is connected to the first end of the generator excitation winding, and the AC side of the first three-phase rectifier circuit is connected to the generator end through the first excitation transformer; the DC side output end of the second three-phase rectifier circuit is connected to the second end of the generator excitation winding, and the AC side of the second three-phase rectifier circuit is connected to the generator end through the second excitation transformer; the DC side negative and positive poles of the first three-phase rectifier circuit are connected in series with the DC side positive and negative poles of the second three-phase rectifier circuit; based on this, the improvement of the present invention is that the first and second three-phase rectifier circuits form a connection mode of AC side parallel connection and DC side series connection, and the DC side is connected to the excitation winding of the generator to form an excitation current control circuit, forming a first channel, and by adjusting the excitation current of the generator, the reactive power is indirectly absorbed or injected into the power grid through the generator; at the same time, the present invention adds a second three-phase rectifier circuit, whose AC end is connected to the generator end, forming a second channel, which can directly absorb or inject reactive power into the power grid.

[0034] like Figure 3As shown in (a), in this embodiment, the first three-phase rectifier circuit adopts a three-phase bridge structure based on thyristors (semi-controlled devices), and each phase bridge arm includes two thyristors, which are recorded as the first thyristor and the second thyristor; the cathode of the first thyristor serves as the first end of the bridge arm, the anode of the first thyristor is connected to the cathode of the second thyristor as the midpoint of the bridge arm, and the anode of the second thyristor serves as the second end of the bridge arm; in the first three-phase rectifier circuit, the first end of the three-phase bridge arm is connected as the negative electrode of the three-phase rectifier circuit, the second end of the three-phase bridge arm is connected as the positive electrode of the three-phase rectifier circuit, the midpoint of the three-phase bridge arm serves as the output end, and the gate of each thyristor is connected to the control device; as shown in Figure 3 As shown in (a), the first three-phase rectifier circuit includes six thyristors, which are S1 to S6 in sequence. The cathodes of S1, S3, and S5 are respectively used as the first ends of the bridge arms, and the anodes of S2, S4, and S6 are respectively used as the second ends of the bridge arms. The anodes of S1, S3, and S5 are respectively connected to the cathodes of S2, S4, and S6;

[0035] like Figure 3 As shown in (b), in this embodiment, the second three-phase rectifier circuit adopts a three-phase bridge arm structure, and each phase bridge arm includes an IGBT with two parallel diodes, which are denoted as the first IGBT and the second IGBT; the emitter and collector of each IGBT are respectively connected to the positive and negative electrodes of the diodes connected in parallel; the collector of the first IGBT serves as the first end of the bridge arm, the emitter of the first IGBT is connected to the collector of the second IGBT as the midpoint of the bridge arm, and the emitter of the second IGBT serves as the second end of the bridge arm; in the second three-phase rectifier circuit, the first end of the three-phase bridge arm is connected as the positive electrode of the three-phase rectifier circuit, the second end of the three-phase bridge arm is connected as the negative electrode of the three-phase rectifier circuit, the midpoint of the three-phase bridge arm serves as the output end, and the gate of each IGBT is connected to the control device; Figure 3 As shown in (b), the second three-phase rectifier circuit includes 6 IGBTs, which are S7 to S12 in sequence. The collectors of S7, S9 and S11 are respectively used as the first ends of the bridge arms, the emitters of S8, S10 and S12 are respectively used as the second ends of the bridge arms, and the emitters of S7, S9 and S11 are respectively connected to the collectors of S8, S10 and S12;

[0036] The negative and positive electrodes of the first three-phase rectifier circuit are connected to the positive and negative electrodes of the second three-phase rectifier circuit respectively;

[0037] like Figure 3 As shown in (c), in this embodiment, the second three-phase rectifier circuit and the first three-phase rectifier circuit can also be connected through a switch array as a transition, that is, the second three-phase rectifier circuit is directly connected to the switch array, and the positive and negative electrodes of the switch array are respectively connected to the negative and positive electrodes of the first three-phase rectifier circuit. This structure can make the excitation voltage control more flexible by controlling the switch array; Figure 3As shown in (c), the switch array includes four IGBTs, namely S13 to S16, and the emitters of S13 and S14 are connected to the collectors of S16 and S15 respectively.

[0038] In summary, in this embodiment, the first three-phase rectifier circuit and the second three-phase rectifier circuit are connected in series on the DC side, and jointly assume the function of providing excitation current: in normal operation, the first three-phase rectifier circuit mainly bears the excitation voltage, and the second three-phase rectifier circuit assists in providing the excitation voltage; in the strong excitation state, the excitation voltage provided by the second three-phase rectifier circuit increases, and the excitation voltage required to be provided by the first three-phase rectifier circuit is correspondingly reduced compared with the conventional excitation method.

[0039] The second three-phase rectifier circuit provides excitation voltage for the system, so that the commutation voltage borne by the devices in the first three-phase rectifier circuit in each working state is reduced, the voltage waveform distortion and peak overvoltage are improved, and the safety of the entire system is improved; the second three-phase rectifier circuit can also be used to compensate for the current harmonics generated by the first three-phase rectifier on the AC side, thereby reducing the impact of power electronic equipment on power quality.

[0040] The embodiment of the present invention further provides a control device of the aforementioned hybrid excitation device, which is used to generate a switch signal according to the reactive power feedback value absorbed or injected into the power grid by the hybrid excitation device and the corresponding command value, so as to control the disconnection of the controllable components in the first and second three-phase rectifier circuits in the hybrid excitation device, so that the reactive power absorbed or injected into the power grid by the hybrid excitation device is equal to the command value; the control device includes a direct reactive power control module and an indirect reactive power control module;

[0041] The direct reactive power control module is respectively connected to each fully-controlled device in the second three-phase rectifier circuit, and is used to obtain a first switch signal according to the reactive power feedback value and the direct reactive power command value directly absorbed or injected into the power grid by the hybrid excitation device through the second channel, so as to control the opening and closing of the fully-controlled devices in the second three-phase rectifier circuit, so that the reactive power directly absorbed or injected into the power grid by the hybrid excitation device through the second channel is equal to the direct reactive power command value;

[0042] The indirect reactive power control module is connected to the half-controlled device in the first three-phase rectifier circuit and the fully-controlled device in the second three-phase rectifier circuit respectively, and is used to obtain a second switch signal according to the reactive power feedback value and the indirect reactive power command value indirectly absorbed or injected into the power grid by the hybrid excitation device through the first channel, so as to control the opening and closing of each controllable device in the first three-phase rectifier circuit and the second three-phase rectifier circuit, so that the reactive power indirectly absorbed or injected into the power grid by the hybrid excitation device through the first channel is equal to the indirect reactive power command value;

[0043] Among them, the direct reactive power command value and the indirect reactive power command value are obtained by dividing the reactive power command value according to a preset ratio, and the direct reactive power command value is smaller than the indirect reactive power command value. In practical applications, the division ratio of the direct reactive power command value and the indirect reactive power command value can be adjusted according to the actual operating conditions, with the aim of ensuring that the power grid operates in the optimal state; the reactive power command value can be optimized and solved based on the power grid structure, parameters, current operating conditions and feedback signals from each module, with the goal of minimizing power grid losses and maximizing voltage quality.

[0044] The embodiment of the present invention further provides a control method of the aforementioned hybrid excitation device, comprising:

[0045] The reactive power command value is divided into a direct reactive power command value and an indirect reactive power command value according to a preset ratio; the direct reactive power command value is smaller than the indirect reactive power command value;

[0046] Obtaining a reactive power feedback value directly absorbed or injected into the power grid by the hybrid excitation device through the second channel from the generator end, and obtaining a first switch signal according to the reactive power feedback value and the direct reactive power command value to control the disconnection of the fully controlled device in the second three-phase rectifier circuit, so that the reactive power directly absorbed or injected into the power grid by the hybrid excitation device through the second channel is equal to the direct reactive power command value;

[0047] A reactive power feedback value indirectly absorbed or injected into the power grid by the hybrid excitation device through the first channel is obtained from the generator end, and a second switching signal is obtained according to the reactive power feedback value and the indirect reactive power command value to control the opening and closing of controllable devices in the first three-phase rectifier circuit and the second three-phase rectifier circuit, so that the reactive power indirectly absorbed or injected into the power grid by the hybrid excitation device through the first channel is equal to the indirect reactive power command value.

[0048] Similarly, in this embodiment, the reactive power command value can be optimized and solved according to the grid structure, parameters, current operating conditions and feedback signals of each module, with the goal of minimizing grid losses and maximizing voltage quality.

[0049] Specifically, under rated operating conditions, the opening and closing of controllable devices of the first three-phase rectifier circuit is mainly determined by the set corresponding excitation voltage value, and the opening and closing of fully controlled devices of the second three-phase rectifier circuit is mainly determined by the set corresponding excitation voltage value and the reactive power demand and harmonic current compensation demand set by the second channel.

[0050] The embodiment of the present invention also provides a power generation system, such as Figure 1As shown, it includes a generator and a main transformer, and the generator end is connected to the power grid through the main transformer; the power generation system also includes the aforementioned hybrid excitation device, specifically, the DC side output end of the first three-phase rectifier circuit in the hybrid excitation device is connected to the first end of the generator excitation winding, and the AC side of the first three-phase rectifier circuit is connected to the generator end through the first excitation transformer; the DC side output end of the second three-phase rectifier circuit in the hybrid excitation device is connected to the second end of the generator excitation winding, and the AC side of the second three-phase rectifier circuit is connected to the generator end through the second excitation transformer; the DC side negative and positive poles of the first three-phase rectifier circuit are connected in series with the DC side positive and negative poles of the second three-phase rectifier circuit.

[0051] The power generation system has two channels, namely, a first channel in which the hybrid excitation device is connected to the generator excitation winding, and a second channel in parallel with the generator terminal. Both channels can be used to provide reactive support to the power grid, wherein the first channel can be used to provide excitation current to the generator; when the power system operates normally, the first channel provides excitation current to the generator, and the second channel provides a small amount of reactive support to the power grid; when a short circuit or open circuit fault occurs in the power system, the first channel reduces the excitation current provided to the generator. In order to prevent the excitation current from being reduced and causing the excitation capacity of the generator to decrease, resulting in system instability, the reactive power provided to the power grid by the second channel can be greatly increased to reduce the impact of short circuit faults and open circuit faults in the AC system and improve the stability of the power generation system.

[0052] Specifically, the first channel can be used to indirectly absorb or inject reactive power into the power grid, and the second channel can be used to directly absorb or inject reactive power into the power grid. Due to the fast response speed of the fully controlled device, reactive power can be quickly absorbed or injected into the power grid through the second channel, and reactive support can be quickly provided to the power grid. A large amount of stable reactive power can be absorbed or injected into the power grid through the first channel. The two channels work together to effectively improve the ability to provide reactive support to the power grid. The second channel can also be used to provide reactive current to the power grid under fault conditions. When a fault occurs, the reactive power provided to the power grid can be appropriately increased through the second channel to maintain system stability. The second channel can also be used to compensate for current harmonics on the AC side of the first three-phase rectifier to reduce the impact of power electronic equipment on power quality.

[0053] In general, the present invention can improve the excitation current control capability of the power generation system and the ability to provide reactive power support to the power grid, can significantly reduce the impact of short-circuit faults and open-circuit faults in the AC system, and improve the reliability of the power generation system.

[0054] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes. The schemes in the embodiments of the present invention may be implemented in various computer languages, for example, object-oriented programming language Java and literal scripting language JavaScript, etc.

[0055] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0056] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0057] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0058] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0059] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A hybrid excitation device, characterized in that: It comprises a first three-phase rectifier circuit and a second three-phase rectifier circuit, wherein the DC side output end of the first three-phase rectifier circuit is connected to the first end of the generator excitation winding, and the AC side of the first three-phase rectifier circuit is connected to the generator end through a first excitation transformer; the DC side output end of the second three-phase rectifier circuit is connected to the second end of the generator excitation winding, and the AC side of the second three-phase rectifier circuit is connected to the generator end through a second excitation transformer; the DC side negative and positive poles of the first three-phase rectifier circuit are connected in series with the DC side positive and negative poles of the second three-phase rectifier circuit; based on this, the DC sides of the first and second three-phase rectifier circuits are connected to the excitation winding of the generator to form a first channel, and reactive power is indirectly absorbed or injected into the power grid through the generator under the control of a second switch signal; at the same time, the AC end of the second three-phase rectifier circuit is connected to the generator end to form a second channel, and reactive power is directly absorbed or injected into the power grid under the control of the first switch signal.

2. The hybrid excitation device according to claim 1, characterized in that: The first three-phase rectifier circuit adopts a three-phase bridge arm structure based on thyristors, and each phase bridge arm includes two thyristors, which are recorded as a first thyristor and a second thyristor; the cathode of the first thyristor serves as the first end of the bridge arm, the anode of the first thyristor is connected to the cathode of the second thyristor as the midpoint of the bridge arm, and the anode of the second thyristor serves as the second end of the bridge arm; in the first three-phase rectifier circuit, the first end of the three-phase bridge arm is connected as the negative electrode of the three-phase rectifier circuit, the second end of the three-phase bridge arm is connected as the positive electrode of the three-phase rectifier circuit, the midpoint of the three-phase bridge arm serves as the output end, and the gate of each thyristor is used to receive the second switching signal.

3. The hybrid excitation device according to claim 1, characterized in that: The second three-phase rectifier circuit adopts a three-phase bridge arm structure, and each phase bridge arm includes an IGBT with two parallel diodes, which are denoted as the first IGBT and the second IGBT; the emitter and collector of each IGBT are respectively connected to the positive and negative electrodes of the diodes connected in parallel; the collector of the first IGBT serves as the first end of the bridge arm, the emitter of the first IGBT is connected to the collector of the second IGBT as the midpoint of the bridge arm, and the emitter of the second IGBT serves as the second end of the bridge arm; in the second three-phase rectifier circuit, the first end of the three-phase bridge arm is connected as the positive electrode of the three-phase rectifier circuit, the second end of the three-phase bridge arm is connected as the negative electrode of the three-phase rectifier circuit, the midpoint of the three-phase bridge arm serves as the output end, and the gate of each IGBT is used to receive the first and second switching signals.

4. The hybrid excitation device according to claim 1, characterized in that: The second three-phase rectifier circuit and the first three-phase rectifier circuit are also connected via a switch array as a transition, that is, the second three-phase rectifier circuit is directly connected to the switch array, and the positive and negative poles of the switch array are respectively connected to the negative and positive poles of the first three-phase rectifier circuit.

5. The control device of the hybrid excitation device according to claim 1, characterized in that: Including direct reactive power control module and indirect reactive power control module; The direct reactive power control module is used to provide a first switch signal to the second three-phase rectifier circuit to control the opening and closing of the fully controlled components in the second three-phase rectifier circuit, so that the reactive power directly absorbed or injected into the power grid by the hybrid excitation device through the second channel is equal to the direct reactive power command value; The indirect reactive power control module is used to provide a second switching signal to the first three-phase rectifier circuit and the second three-phase rectifier circuit, control the opening and closing of each controllable device in the first three-phase rectifier circuit and the second three-phase rectifier circuit, so that the reactive power indirectly absorbed or injected into the power grid by the hybrid excitation device through the first channel is equal to the indirect reactive power command value.

6. The control device according to claim 5, characterized in that: The direct reactive power control module obtains a first switch signal according to the reactive power feedback value directly absorbed or injected into the power grid by the hybrid excitation device through the second channel and the direct reactive power command value, so as to control the disconnection of the fully controlled device in the second three-phase rectifier circuit, so that the reactive power directly absorbed or injected into the power grid by the hybrid excitation device through the second channel is equal to the direct reactive power command value; The indirect reactive power control module obtains a second switching signal based on the reactive power feedback value and the indirect reactive power command value indirectly absorbed or injected into the power grid by the hybrid excitation device through the first channel to control the opening and closing of each controllable device in the first three-phase rectifier circuit and the second three-phase rectifier circuit, so that the reactive power indirectly absorbed or injected into the power grid by the hybrid excitation device through the first channel is equal to the indirect reactive power command value.

7. The control method of the hybrid excitation device according to claim 1, characterized in that: include, The first switch signal is used to control the opening and closing of the fully controlled devices in the second three-phase rectifier circuit, so that the reactive power directly absorbed or injected into the power grid by the hybrid excitation device through the second channel is equal to the direct reactive power command value; The second switch signal is used to control the opening and closing of each controllable device in the first three-phase rectifier circuit and the second three-phase rectifier circuit, so that the reactive power indirectly absorbed or injected into the power grid by the hybrid excitation device through the first channel is equal to the indirect reactive power command value.

8. The control method according to claim 7, characterized in that: The method for obtaining the first switch signal is to obtain, from the generator end, a reactive power feedback value directly absorbed or injected into the power grid by the hybrid excitation device through the second channel, and obtain the first switch signal according to the reactive power feedback value and the direct reactive power command value; The method for obtaining the second switching signal is to obtain from the generator end a reactive power feedback value indirectly absorbed or injected into the power grid by the hybrid excitation device through the first channel, and obtain the second switching signal based on the reactive power feedback value and the indirect reactive power command value.

9. The control method according to claim 7, characterized in that: The direct reactive power command value and the indirect reactive power command value are obtained by dividing the reactive power command value according to a preset ratio, and the direct reactive power command value is smaller than the indirect reactive power command value.

10. A power generation system, comprising a generator and a main transformer, wherein the generator end is connected to a power grid via the main transformer; characterized in that: It also includes a hybrid excitation device as claimed in any one of claims 1 to 4.

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