A full-controlled device excitation system based on a two-axis excitation phase modifier and a control method thereof

Abstract

The application discloses a full-control device excitation system and a control method based on a double-shaft excitation phase modifier, belongs to the field of excitation control of power systems, and comprises a double-shaft excitation synchronous phase modifier, a three-channel full-control device excitation device and a controller. The double-shaft excitation synchronous phase modifier is connected with a power grid. The three-channel full-control device excitation device comprises three circuits connected in parallel, two DC / DC chopping circuits, an AC / DC rectifier circuit and a controller. The two DC / DC chopping circuits are connected with a d-shaft excitation winding and a q-shaft excitation winding in series respectively, and form a first reactive power channel and a second reactive power channel respectively. The AC / DC rectifier circuit is connected with the double-shaft excitation synchronous phase modifier in series at a grid side, and forms a third reactive power channel. The controller is connected with the three-channel full-control device excitation device, and is used for generating driving signals of each switching device, so that the three-channel full-control device excitation device injects or absorbs reactive power equal to a reactive power instruction value into the power grid. The application can improve the voltage quality of the power system and the stability of system operation while improving the degree of leading-phase operation of the synchronous phase modifier.

Description

Technical Field

[0001] This invention belongs to the field of power system excitation control, and more specifically, relates to an excitation system and control method based on a dual-axis excitation synchronous condenser. Background Technology

[0002] Accelerating the construction of a new power system adapted to the gradually increasing proportion of new energy sources is one of the main measures for my country to achieve its "dual carbon" goals. In this new power system, the "dual high" characteristics of high-proportion new energy power generation and high-proportion power electronic equipment will become more pronounced, leading to a continuous weakening of dynamic reactive power compensation and voltage support capabilities, insufficient system damping, and severe challenges to the safe and stable operation of the system. To enhance the power system's regulation capacity and flexibility, and to improve the distribution network's ability to accommodate distributed new energy sources, it is urgently necessary to develop supporting voltage and reactive power support equipment.

[0003] Synchronous condensers are a flexible, reliable, and fast phase-adjusting resource that can effectively address the issues of renewable energy consumption and improving grid voltage stability. Currently, most synchronous condensers use static single-axis self-excited excitation based on semi-controlled thyristor phase-controlled rectifiers, which presents the following problems: They can only control the unit through a single channel by adjusting the excitation current, and their adjustment capability is limited by the generator terminal voltage level; due to the slow response speed of the thyristors and the fact that they can only achieve semi-control, they cannot achieve rapid reactive power injection or absorption when the grid voltage fluctuates significantly; furthermore, traditional excitation condensers generally use a single-axis excitation structure, and their leading-phase operation capability is limited by the minimum excitation current, with the maximum leading-phase operation capability mainly depending on its own parameters, making it difficult to further suppress overvoltage phenomena; and as the leading-phase depth increases, the stator end leakage magnetic field weakens, the magnetic flux increases, and the iron loss increases, leading to excessively high local temperatures.

[0004] Studies have shown that fully controlled device excitation systems can independently control the exchange of reactive power on the grid side and maintain DC-side voltage through converter control, thus exhibiting better excitation stability and effectively improving the insufficient excitation capability of self-excited excitation systems during system short circuits. Because fully controlled devices respond rapidly and are completely controllable, they can quickly inject or absorb reactive power into the system when significant voltage drops or reactive power redundancy occur, providing timely voltage support and overcoming the slow response of traditional synchronous condensers. Furthermore, existing research has theoretically derived the impact of injecting reactive power at the generator terminal (i.e., the grid side) on the equivalent damping of the generator system, demonstrating that fully controlled device excitation systems can provide dual-channel damping, effectively improving power system damping and enhancing power system stability.

[0005] Furthermore, to further improve the phase-leading capability of synchronous condensers, researchers have proposed a dual-axis excitation synchronous condenser based on traditional synchronous condensers. Its rotor has two mutually perpendicular excitation windings: a d-axis excitation winding and a q-axis excitation winding. Based on the dual-axis excitation synchronous condenser, the phase-leading capability can be effectively improved. For example, in the patent document titled "An Excitation Control Device for a Dual-Axis Excitation Synchronous Condenser" with authorization announcement number "CN216959336U", the provided dual-axis excitation synchronous condenser excitation system normally employs dual-axis excitation with identical excitation currents in both phase windings. This not only reduces uneven rotor heating but also overcomes the limitation of zero minimum combined excitation current, greatly improving the phase-leading capability of the condenser and suppressing system transient overvoltages. When one axis of the excitation winding fails, it switches to single-axis excitation, significantly improving the reliability of the condenser's operation. However, this scheme unifies the control of the d-axis and q-axis, making it inflexible in controlling the excitation magnetomotive force (EMF). Furthermore, its ability to inject / absorb reactive power in a short time is insufficient, failing to achieve rapid reactive power and voltage support. In other excitation systems based on dual-axis excitation synchronous condensers, the combined MMF of the two excitation windings is controlled solely by controlling the q-axis excitation winding. This type of scheme also suffers from the aforementioned problems: inflexible control of the excitation MMF and inability to achieve rapid reactive power and voltage support. Summary of the Invention

[0006] In view of the shortcomings of the existing technology and the need for improvement, the present invention provides an excitation system and control method based on a dual-axis excitation synchronous condenser with fully controllable devices. Its purpose is to improve the voltage quality of the power system and enhance the stability of the system operation while improving the phase advance operation capability of the synchronous condenser.

[0007] To achieve the above objectives, according to one aspect of the present invention, a fully controlled device excitation system based on a dual-axis excitation phase shifter is provided, comprising:

[0008] A dual-axis excitation synchronous condenser, whose terminals are connected to the power grid;

[0009] The three-channel fully controlled device excitation system comprises three circuits: a first DC / DC chopper circuit, a second DC / DC chopper circuit, and an AC / DC rectifier circuit. The input terminals of the three circuits are connected in parallel, and the switching devices in all three circuits are fully controlled switching devices. The output terminal of the first DC / DC chopper circuit is connected in series with the d-axis excitation winding of the dual-axis excitation synchronous condenser to form a first reactive power channel, used to regulate the excitation voltage output by the d-axis excitation winding. The output terminal of the second DC / DC chopper circuit is connected in series with the q-axis excitation winding of the dual-axis excitation synchronous condenser to form a second reactive power channel, used to regulate the excitation voltage output by the q-axis excitation winding. The AC / DC rectifier circuit is connected to the generator terminal of the dual-axis excitation synchronous condenser on the grid side through an excitation transformer to form a third reactive power channel, used to inject or absorb reactive power into the grid.

[0010] And a controller, which is connected to each fully controlled switching device in the three-channel fully controlled device excitation device, is used to generate drive signals for each fully controlled switching device to control the opening and closing of each fully controlled switching device in the three-channel fully controlled device excitation device, so that the reactive power injected into or absorbed by the three-channel fully controlled device excitation device is equal to the reactive power command value.

[0011] Furthermore, the controller includes: a control module, a d-axis excitation voltage control module, a q-axis excitation voltage control module, and a direct reactive power control module;

[0012] The control module is used to divide the reactive power command value into direct reactive power command value and indirect reactive power command value according to a preset ratio; the direct reactive power command value is less than the indirect reactive power command value.

[0013] The control module is also used to calculate the rotor position command value of the dual-axis excitation synchronous condenser based on the indirect reactive power command value, and to calculate the corresponding d-axis excitation voltage command value and q-axis excitation voltage command value based on the rotor position command value and the measured value of the rotor position.

[0014] The d-axis excitation voltage control module has its input terminal connected to the control module and its output terminal connected to each fully controlled switching device in the first DC / DC chopper circuit. It is used to generate switching signals for driving each fully controlled switching device in the first DC / DC chopper circuit based on the d-axis excitation voltage command value and the voltage feedback value across the d-axis excitation winding, so that the excitation voltage output by the d-axis excitation winding is equal to the d-axis excitation voltage command value.

[0015] The q-axis excitation voltage control module has its input terminal connected to the control module and its output terminal connected to each fully controlled switching device in the second DC / DC chopper circuit. It is used to generate switching signals for driving each fully controlled switching device in the second DC / DC chopper circuit based on the q-axis excitation voltage command value and the voltage feedback value across the q-axis excitation winding, so that the excitation voltage output by the q-axis excitation winding is equal to the q-axis excitation voltage command value.

[0016] The direct reactive power control module, whose input is connected to the control module, is used to generate switching signals for controlling each fully controlled switching device of the AC / DC rectifier circuit based on the direct reactive power command value and the reactive power value injected or absorbed by the synchronous condenser into the grid, so that the reactive power absorbed or injected into the grid by the AC / DC rectifier circuit is equal to the direct reactive power command value.

[0017] Furthermore, the d-axis excitation voltage control module includes a first voltage regulator and a first power system stabilizer, and the q-axis excitation voltage control module includes a second voltage regulator and a second power system stabilizer.

[0018] Furthermore, the direct reactive power control module is a reactive power damping controller.

[0019] Furthermore, the first DC / DC chopper circuit and the second DC / DC chopper circuit have the same structure;

[0020] Each DC / DC chopper circuit includes two bridge arms. The upper and lower ends of the two bridge arms are connected and led out to form the input terminal of the DC / DC chopper circuit.

[0021] The upper and lower arms of each bridge arm are fully controlled switching devices, and the midpoint of the two bridge arms is led out to form the output terminal of the DC / DC chopper circuit.

[0022] Furthermore, the AC / DC rectifier circuit includes three bridge arms, and the upper and lower ends of the three bridge arms are connected and led out to form the input terminal of the AC / DC rectifier circuit.

[0023] The upper and lower arms of each bridge arm are fully controlled switching devices, and the midpoint of the three bridge arms is led out to form the grid side of the AC / DC rectifier circuit.

[0024] Furthermore, an inductor and a resistor are connected in series between the midpoint of each arm of the AC / DC rectifier circuit and the excitation transformer.

[0025] Furthermore, the excitation device for the three-channel fully controlled device also includes a voltage stabilizing capacitor connected in parallel with the input terminals of the first DC / DC chopper circuit, the second DC / DC chopper circuit, and the AC / DC rectifier circuit.

[0026] According to another aspect of the present invention, a control method based on the above-described fully controlled device excitation system is provided, comprising the following steps:

[0027] Command value calculation steps: Divide the reactive power command value into direct reactive power command value and indirect reactive power command value according to a preset ratio; calculate the rotor position command value of the dual-axis excitation synchronous condenser based on the indirect reactive power command value, and calculate the corresponding d-axis excitation voltage command value and q-axis excitation voltage command value based on the rotor position command value and the measured value of the rotor position; the direct reactive power command value is less than the indirect reactive power command value;

[0028] Direct reactive power control steps: Based on the direct reactive power command value and the reactive power value injected or absorbed by the synchronous condenser into the grid, a switching signal is generated to control each fully controlled switching device of the AC / DC rectifier circuit, so that the reactive power absorbed or injected into the grid by the AC / DC rectifier circuit is equal to the direct reactive power command value.

[0029] Indirect reactive power control steps; indirect reactive power control steps include:

[0030] The d-axis excitation voltage control steps are as follows: Based on the d-axis excitation voltage command value and the voltage feedback value across the d-axis excitation winding, a switching signal is generated to drive each fully controlled switching device in the first DC / DC chopper circuit, so that the excitation voltage output by the d-axis excitation winding is equal to the d-axis excitation voltage command value.

[0031] Q-axis excitation voltage control steps: Based on the q-axis excitation voltage command value and the voltage feedback value across the q-axis excitation winding, generate switching signals to drive each fully controlled switching device in the second DC / DC chopper circuit, so that the excitation voltage output by the q-axis excitation winding is equal to the q-axis excitation voltage command value.

[0032] In summary, the technical solutions conceived in this invention achieve the following technical effects compared to existing technologies:

[0033] (1) Based on the dual-axis excitation synchronous condenser, this invention proposes a three-channel fully controlled device excitation device. The first and second reactive power channels are used to independently control the excitation voltage output by the d-axis and q-axis excitation windings of the dual-axis excitation synchronous condenser, respectively. This allows for the indirect injection or absorption of reactive power into the power grid through the dual-axis excitation synchronous condenser, effectively improving the condenser's phase-leading capability and achieving large-capacity reactive power absorption and injection capability. The third reactive power channel is used to directly and rapidly inject or absorb reactive power into the power grid, achieving instantaneous voltage support. The coordinated operation of the three reactive power channels can effectively improve the voltage quality of the power system and enhance the stability of system operation. Furthermore, with the cooperation of the third channel, this invention can independently control the d-axis and q-axis excitation windings through the other two reactive power channels, achieving flexible control of the excitation magnetomotive force and further improving the reactive power support capability of the system.

[0034] (2) In this invention, the three-channel fully controlled device excitation device increases the system damping while injecting reactive power, thereby realizing the suppression of system oscillation by the three damping channels and improving the stability of the power system operation.

[0035] (3) In this invention, the switching devices in the three-channel fully controlled device excitation device are all fully controlled switching devices. Since the fully controlled devices react quickly and are completely controllable, they can quickly inject or absorb reactive power into the system when the system experiences a large voltage drop or reactive power redundancy, and provide voltage support in a timely manner. Therefore, this invention can have better excitation stability and effectively improve the problem of insufficient excitation capability of the self-excited excitation system during system short circuit. Attached Figure Description

[0036] Figure 1 A schematic diagram of a fully controlled device excitation system based on a dual-axis excitation phase shifter provided in an embodiment of the present invention;

[0037] Figure 2 This is a schematic diagram of the circuit structure of the fully controlled device excitation system based on a dual-axis excitation phase shifter provided in an embodiment of the present invention. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0039] In this invention, the terms "first," "second," etc. (if present) in the invention and the accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0040] To address the technical problems of existing excitation systems that cannot flexibly control the excitation magnetomotive force and achieve rapid reactive power and voltage support when using dual-axis synchronous condensers to increase phase-leading capability, this invention provides a fully controllable device excitation system and control method based on a dual-axis synchronous condenser. The overall concept is as follows: Based on a dual-axis synchronous condenser, a specific three-channel fully controllable device excitation device is set up. The three reactive power channels coordinate with each other, allowing two of the reactive power channels to independently control the excitation voltage output from the d-axis and q-axis excitation windings in the dual-axis synchronous condenser, flexibly controlling the rotor position angle and thus flexibly controlling the excitation magnetomotive force. Ultimately, with the coordinated operation of the three reactive power channels, the voltage quality of the power system can be effectively improved, and the stability of system operation can be enhanced.

[0041] The following is an example.

[0042] Example 1:

[0043] A fully controlled device excitation system based on a dual-axis excitation phase shifter, such as... Figure 1 and Figure 2 As shown, it includes:

[0044] A dual-axis excitation synchronous condenser, whose terminals are connected to the power grid;

[0045] The three-channel fully controlled device excitation system comprises three circuits: a first DC / DC chopper circuit, a second DC / DC chopper circuit, and an AC / DC rectifier circuit. The input terminals of the three circuits are connected in parallel, and the switching devices in all three circuits are fully controlled switching devices. The output terminal of the first DC / DC chopper circuit is connected in series with the d-axis excitation winding of the dual-axis excitation synchronous condenser to form a first reactive power channel, used to regulate the excitation voltage output by the d-axis excitation winding. The output terminal of the second DC / DC chopper circuit is connected in series with the q-axis excitation winding of the dual-axis excitation synchronous condenser to form a second reactive power channel, used to regulate the excitation voltage output by the q-axis excitation winding. The AC / DC rectifier circuit is connected to the generator terminal of the dual-axis excitation synchronous condenser on the grid side through an excitation transformer to form a third reactive power channel, used to inject or absorb reactive power into the grid.

[0046] And a controller, which is connected to each fully controlled switching device in the three-channel fully controlled device excitation device, is used to generate drive signals for each fully controlled switching device to control the opening and closing of each fully controlled switching device in the three-channel fully controlled device excitation device, so that the reactive power injected into or absorbed by the three-channel fully controlled device excitation device is equal to the reactive power command value.

[0047] In this embodiment, the three-channel fully controlled device excitation device includes three reactive power channels, such as... Figure 1 and Figure 2In this embodiment, the first and second reactive power channels independently control the d-axis and q-axis excitation windings, respectively. Therefore, the first and second reactive power channels can indirectly inject or absorb reactive power into the grid through a dual-axis excitation synchronous condenser. The third reactive power channel is connected to the dual-axis excitation synchronous condenser and can directly inject or absorb reactive power into the grid. Furthermore, in this embodiment, all switching devices in the three-channel fully controlled device excitation system are fully controlled switching devices with fast response speed and complete controllability. Therefore, based on the third reactive power channel, this embodiment can quickly inject or absorb reactive power into the grid, achieving instantaneous voltage support. Based on the first and second channels, this embodiment can increase the phase-leading capability of the synchronous condenser and improve its large-capacity reactive power absorption and injection capability. The coordinated operation of the three reactive power channels can effectively improve the voltage quality of the power system and enhance the stability of system operation. Meanwhile, thanks to the coordination of the third reactive power channel, the first and second reactive power channels independently control the d-axis and q-axis excitation windings, respectively, achieving independent control of the dual axes. This allows for control of the rotor position angle and, consequently, flexible control of the excitation magnetomotive force. Compared to existing systems that control both d-axis and q-axis uniformly or only the q-axis, this embodiment increases the phase advance depth of the synchronous condenser and improves operational stability margin.

[0048] In addition, the three reactive power channels not only inject reactive power but also increase the system's damping, thus achieving the three-damping channel to suppress system oscillations and improve the stability of power system operation.

[0049] like Figure 2 As shown, in this embodiment, the controller further includes: a control module, a d-axis excitation voltage control module, a q-axis excitation voltage control module, and a direct reactive power control module;

[0050] The control module is used to divide the reactive power command value into direct reactive power command value and indirect reactive power command value according to a preset ratio; the direct reactive power command value is less than the indirect reactive power command value.

[0051] The control module is also used to calculate the rotor position command value of the dual-axis excitation synchronous condenser based on the indirect reactive power command value, and to calculate the corresponding d-axis excitation voltage command value and q-axis excitation voltage command value based on the rotor position command value and the measured value of the rotor position.

[0052] The d-axis excitation voltage control module has its input terminal connected to the control module and its output terminal connected to each fully controlled switching device in the first DC / DC chopper circuit. It is used to generate switching signals for driving each fully controlled switching device in the first DC / DC chopper circuit based on the d-axis excitation voltage command value and the voltage feedback value across the d-axis excitation winding, so that the excitation voltage output by the d-axis excitation winding is equal to the d-axis excitation voltage command value.

[0053] The q-axis excitation voltage control module has its input terminal connected to the control module and its output terminal connected to each fully controlled switching device in the second DC / DC chopper circuit. It is used to generate switching signals for driving each fully controlled switching device in the second DC / DC chopper circuit based on the q-axis excitation voltage command value and the voltage feedback value across the q-axis excitation winding, so that the excitation voltage output by the q-axis excitation winding is equal to the q-axis excitation voltage command value.

[0054] The direct reactive power control module, whose input is connected to the control module, is used to generate switching signals for controlling each fully controlled switching device of the AC / DC rectifier circuit based on the direct reactive power command value and the reactive power value injected or absorbed by the synchronous condenser into the grid, so that the reactive power absorbed or injected into the grid by the AC / DC rectifier circuit is equal to the direct reactive power command value.

[0055] In this embodiment, the controller's control logic is as follows: when it is necessary to inject or absorb reactive power into the grid, a small portion of reactive power is first injected or absorbed into the grid through the third reactive power channel to quickly provide voltage support to the grid; at the same time, since this embodiment can achieve decoupling control of the d-axis and q-axis excitation windings through two control modules, this embodiment can accurately inject or absorb the remaining reactive power into the grid through the first and second reactive power channels to ensure the stability of system operation.

[0056] It is easy to understand that the reactive power injected into or absorbed by the grid through the third reactive power channel needs to be determined according to the actual control requirements and the reactive power support capacity of the third reactive power channel.

[0057] Optionally, such as Figure 2 As shown, the d-axis excitation voltage control module includes a first voltage regulator and a first power system stabilizer, and the q-axis excitation voltage control module includes a second voltage regulator and a second power system stabilizer.

[0058] The required switching signal can be quickly determined by the voltage regulator (AVR); with the cooperation of the power system stabilizer (PSS), active power vibration can be suppressed and the excitation can be ensured to work normally.

[0059] Optionally, in this embodiment, the direct reactive power control module is a reactive power damping controller (RPDC).

[0060] like Figure 2 As shown, in this embodiment, the first DC / DC chopper circuit and the second DC / DC chopper circuit have the same structure;

[0061] Each DC / DC chopper circuit includes two bridge arms. The upper and lower ends of the two bridge arms are connected and led out to form the input terminal of the DC / DC chopper circuit.

[0062] The upper and lower arms of each bridge arm are fully controlled switching devices, and the midpoint of the two bridge arms is led out to form the output terminal of the DC / DC chopper circuit.

[0063] In this embodiment, the fully controlled switching device on each bridge arm of the DC / DC chopper circuit is specifically an IGBT. The example is a DC / DC chopper circuit connected to the q-axis excitation winding. The two bridge arms are designated as Bridge Arm 1 and Bridge Arm 2. Bridge Arm 1 has two IGBTs: designated as the first IGBT and the second IGBT. Bridge Arm 2 has two IGBTs: designated as the third IGBT and the fourth IGBT. The midpoint of Bridge Arm 1 connects the emitter of the first IGBT and the collector of the second IGBT, serving as the positive output of the DC / DC chopper circuit. The midpoint of Bridge Arm 2 connects the emitter of the third IGBT and the collector of the fourth IGBT, serving as the negative output of the DC / DC chopper circuit. The midpoints of Bridge Arm 1 and Bridge Arm 2 serve as the two input ports of the q-axis excitation winding, providing DC power to the q-axis excitation winding.

[0064] The structure of the DC / DC chopper circuit connected to the d-axis excitation winding is similar and will not be repeated here.

[0065] like Figure 2 As shown, in this embodiment, the AC / DC rectifier circuit includes three bridge arms. The upper and lower ends of the three bridge arms are connected and led out to form the input terminal of the AC / DC rectifier circuit.

[0066] The upper and lower arms of each bridge arm are fully controlled switching devices, and the midpoint of the three bridge arms is led out to form the grid side of the AC / DC rectifier circuit.

[0067] In this embodiment, each of the three-phase bridge arms of the AC / DC rectifier circuit includes, but is not limited to, a two-level structure, a three-level structure, and a five-level structure. Taking the two-level structure as an example: each phase bridge arm contains two IGBTs. Taking phase A as an example: the two IGBTs in phase A are denoted as the first IGBT and the second IGBT. The two ends of the bridge arm are the collector of the first IGBT and the emitter of the second IGBT, respectively, serving as the positive and negative terminals of the three-phase rectifier circuit; the positive and negative terminals of each phase bridge arm are connected in parallel, serving as the positive and negative terminals of the AC / DC rectifier circuit, providing DC power to the DC / DC chopper circuit.

[0068] like Figure 2 As shown, an inductor L and a resistor R are connected in series between the midpoint of each bridge arm of the AC / DC rectifier circuit and the excitation transformer to serve as a filter.

[0069] like Figure 2As shown, in this embodiment, the three-channel fully controlled device excitation device also includes a voltage stabilizing capacitor C connected in parallel with the input terminals of the first DC / DC chopper circuit, the second DC / DC chopper circuit, and the AC / DC rectifier circuit. This capacitor is used to ensure the stability of the DC side voltage of the AC / DC rectifier circuit, provide a stable DC power supply for the DC / DC chopper circuit, thereby obtaining a stable excitation current; and at the same time, it provides a stable voltage source for reactive power injection into the grid side of the reactive power channel.

[0070] Example 2:

[0071] The control method for the fully controlled device excitation system provided in Embodiment 1 above includes the following steps:

[0072] Command value calculation steps: Divide the reactive power command value into direct reactive power command value and indirect reactive power command value according to a preset ratio; calculate the rotor position command value of the dual-axis excitation synchronous condenser based on the indirect reactive power command value, and calculate the corresponding d-axis excitation voltage command value and q-axis excitation voltage command value based on the rotor position command value and the measured value of the rotor position; the direct reactive power command value is less than the indirect reactive power command value;

[0073] Direct reactive power control steps: Based on the direct reactive power command value and the reactive power value injected or absorbed by the synchronous condenser into the grid, a switching signal is generated to control each fully controlled switching device of the AC / DC rectifier circuit, so that the reactive power absorbed or injected into the grid by the AC / DC rectifier circuit is equal to the direct reactive power command value.

[0074] Indirect reactive power control steps; indirect reactive power control steps include:

[0075] The d-axis excitation voltage control steps are as follows: Based on the d-axis excitation voltage command value and the voltage feedback value across the d-axis excitation winding, a switching signal is generated to drive each fully controlled switching device in the first DC / DC chopper circuit, so that the excitation voltage output by the d-axis excitation winding is equal to the d-axis excitation voltage command value.

[0076] Q-axis excitation voltage control steps: Based on the q-axis excitation voltage command value and the voltage feedback value across the q-axis excitation winding, generate switching signals to drive each fully controlled switching device in the second DC / DC chopper circuit, so that the excitation voltage output by the q-axis excitation winding is equal to the q-axis excitation voltage command value.

[0077] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A fully controlled device excitation system based on a dual-axis excitation phase-shifting camera, characterized in that, include: A dual-axis excitation synchronous condenser, whose terminals are connected to the power grid; The three-channel fully controlled device excitation system comprises three circuits: a first DC / DC chopper circuit, a second DC / DC chopper circuit, and an AC / DC rectifier circuit. The input terminals of the three circuits are connected in parallel, and the switching devices in all three circuits are fully controlled switching devices. The output terminal of the first DC / DC chopper circuit is connected in series with the d-axis excitation winding of the dual-axis excitation synchronous condenser to form a first reactive power channel, used to regulate the excitation voltage output by the d-axis excitation winding. The output terminal of the second DC / DC chopper circuit is connected in series with the q-axis excitation winding of the dual-axis excitation synchronous condenser to form a second reactive power channel, used to regulate the excitation voltage output by the q-axis excitation winding. The AC / DC rectifier circuit is connected to the generator terminal of the dual-axis excitation synchronous condenser via an excitation transformer on the grid side, forming a third reactive power channel, used to inject or absorb reactive power into the grid. And a controller, which is connected to each fully controlled switch device in the three-channel fully controlled device excitation device, is used to generate drive signals for each fully controlled switch device to control the opening and closing of each fully controlled switch device in the three-channel fully controlled device excitation device, so that the reactive power injected into or absorbed by the three-channel fully controlled device excitation device is equal to the reactive power command value. The controller includes: a control module, a d-axis excitation voltage control module, a q-axis excitation voltage control module, and a direct reactive power control module; The control module is used to divide the reactive power command value 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 less than the indirect reactive power command value. The control module is also used to calculate the rotor position command value of the dual-axis excitation synchronous condenser based on the indirect reactive power command value, and to calculate the corresponding d-axis excitation voltage command value and q-axis excitation voltage command value based on the rotor position command value and the measured value of the rotor position. The d-axis excitation voltage control module has its input terminal connected to the control module and its output terminal connected to each fully controlled switching device in the first DC / DC chopper circuit. It is used to generate switching signals for driving each fully controlled switching device in the first DC / DC chopper circuit based on the d-axis excitation voltage command value and the voltage feedback value across the d-axis excitation winding, so that the excitation voltage output by the d-axis excitation winding is equal to the d-axis excitation voltage command value. The q-axis excitation voltage control module has its input terminal connected to the control module and its output terminal connected to each fully controlled switching device in the second DC / DC chopper circuit. It is used to generate switching signals for driving each fully controlled switching device in the second DC / DC chopper circuit based on the q-axis excitation voltage command value and the voltage feedback value across the q-axis excitation winding, so that the excitation voltage output by the q-axis excitation winding is equal to the q-axis excitation voltage command value. The direct reactive power control module has its input terminal connected to the control module. It is used to generate switching signals for controlling each fully controlled switching device of the AC / DC rectifier circuit based on the direct reactive power command value and the reactive power value injected or absorbed by the synchronous condenser into the power grid, so that the reactive power absorbed or injected by the AC / DC rectifier circuit into the power grid is equal to the direct reactive power command value.

2. The fully controlled device excitation system based on a dual-axis excitation phase shifter as described in claim 1, characterized in that, The d-axis excitation voltage control module includes a first voltage regulator and a first power system stabilizer, and the q-axis excitation voltage control module includes a second voltage regulator and a second power system stabilizer.

3. The fully controlled device excitation system based on a dual-axis excitation phase shifter as described in claim 1, characterized in that, The direct reactive power control module is a reactive power damping controller.

4. The fully controlled device excitation system based on a dual-axis excitation phase-shifting camera as described in any one of claims 1 to 3, characterized in that, The first DC / DC chopper circuit and the second DC / DC chopper circuit have the same structure; Each DC / DC chopper circuit includes two bridge arms. The upper and lower ends of the two bridge arms are connected and led out to form the input terminal of the DC / DC chopper circuit. The upper and lower arms of each bridge arm are fully controlled switching devices, and the midpoint of the two bridge arms is led out to form the output terminal of the DC / DC chopper circuit.

5. The fully controlled device excitation system based on a dual-axis excitation phase shifter as described in any one of claims 1 to 3, characterized in that, The AC / DC rectifier circuit includes three bridge arms, and the upper and lower ends of the three bridge arms are connected and led out to form the input terminal of the AC / DC rectifier circuit. The upper and lower arms of each bridge arm are fully controlled switching devices, and the midpoint of the three bridge arms is led out to form the grid side of the AC / DC rectifier circuit.

6. The fully controlled device excitation system based on a dual-axis excitation phase shifter as described in claim 5, characterized in that, An inductor and a resistor are connected in series between the midpoint of each arm of the AC / DC rectifier circuit and the excitation transformer.

7. The fully controlled device excitation system based on a dual-axis excitation phase shifter as described in any one of claims 1 to 3, characterized in that, The excitation device of the three-channel fully controlled device also includes a voltage stabilizing capacitor connected in parallel with the input terminals of the first DC / DC chopper circuit, the second DC / DC chopper circuit and the AC / DC rectifier circuit.

8. A control method for a fully controlled device excitation system according to any one of claims 1 to 7, characterized in that, The steps include the following: Command value calculation steps: Divide the reactive power command value into direct reactive power command value and indirect reactive power command value according to a preset ratio; calculate the rotor position command value of the dual-axis excitation synchronous condenser based on the indirect reactive power command value, and calculate the corresponding d-axis excitation voltage command value and q-axis excitation voltage command value based on the rotor position command value and the measured value of the rotor position; the direct reactive power command value is less than the indirect reactive power command value; Direct reactive power control steps: Based on the direct reactive power command value and the reactive power value injected or absorbed by the synchronous condenser into the power grid, a switching signal is generated to control each fully controlled switching device of the AC / DC rectifier circuit, so that the reactive power absorbed or injected into the power grid by the AC / DC rectifier circuit is equal to the direct reactive power command value. Indirect reactive power control steps; The indirect reactive power control steps include: d-axis excitation voltage control steps: Generate switching signals for driving each fully controlled switching device in the first DC / DC chopper circuit based on the d-axis excitation voltage command value and the voltage feedback value across the d-axis excitation winding, so that the excitation voltage output by the d-axis excitation winding is equal to the d-axis excitation voltage command value. Q-axis excitation voltage control steps: Based on the q-axis excitation voltage command value and the voltage feedback value across the q-axis excitation winding, generate switching signals to drive each fully controlled switching device in the second DC / DC chopper circuit, so that the excitation voltage output by the q-axis excitation winding is equal to the q-axis excitation voltage command value.

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