A method and system for output impedance configuration for a circular current limiter

Abstract

The application relates to the field of networked converters, in particular to an output impedance configuration method and system for a circular current limiter; the output current, the output voltage and the voltage reference signal of a networked GFM converter are acquired; an original voltage control signal is calculated through proportional-integral control; an enabling signal is calculated; an output impedance configuration signal is calculated; the voltage control signal is calculated according to the output impedance configuration signal and the original voltage control signal; the voltage control signal is subjected to amplitude normalization processing; an original current reference signal is calculated and generated; the original current reference signal is input into the circular current limiter for amplitude limitation, and an amplitude-limited current reference signal for limiting the output current of the networked GFM converter is output; the application solves the problem that the output impedance of the existing circular current limiter cannot be freely configured, and significantly improves the ability of the networked GFM converter with the circular current limiter to meet the power grid protection demand.

Description

Technical Field

[0001] This invention relates to the field of grid-type converters, and more specifically to a method and system for configuring the output impedance of a circular current limiter. Background Technology

[0002] Grid-Forming (GFM) control technology enables renewable energy sources using converter equipment as the grid connection interface to exhibit voltage source characteristics during normal operation, providing a safe and reliable application foundation for large-scale renewable energy integration. However, converter equipment itself is composed of semiconductor devices, and when a grid fault occurs, the converter equipment needs to limit its output current to prevent hardware damage. Therefore, in practical systems, a stable and reliable current limiter needs to be integrated into the grid-forming GFM control to ensure the safe operation of the converter equipment.

[0003] See Figure 1 This is a schematic diagram of an existing grid-connected GFM control system that includes a current limiter. Power control is used to connect the synchronous converter to the grid, while voltage and current control are used to control the output voltage and current of the converter, respectively. The current limiter directly modifies the current reference signal provided by the voltage control and uses precise current control to ensure the output current accurately tracks the current reference signal, thereby limiting the converter's output current and effectively providing overcurrent protection for the equipment.

[0004] Existing current limiters mainly include three types: instantaneous current limiters, priority current limiters, and circular current limiters. Instantaneous current limiters have the advantages of simple structure and ease of implementation; however, they are prone to causing distortion of the output current waveform, adversely affecting the system's power quality. Priority current limiters switch the converter from grid-connected GFM control to grid-following control and fix the phase angle of the current reference signal, enabling it to effectively support the grid during faults. However, once the grid fault is cleared, the converter cannot automatically revert from grid-following control to grid-connected GFM control, leading to problems such as increased output voltage or even converter disconnection from the grid. In contrast, circular current limiters ensure that the output current waveform always remains sinusoidal and can maintain grid-connected GFM control even during grid faults, ensuring that the converter can automatically return to its original operating state after the grid fault is cleared. Therefore, they have received widespread research and application in industry and academia.

[0005] However, existing circular current limiters exhibit resistive characteristics in their equivalent output impedance during grid faults, thus losing the converter's ability to regulate the output current phase angle during such faults. Furthermore, according to the relay protection requirements of existing power systems, the impedance angle of the converter's equivalent output impedance should closely match the impedance angle of the grid line to maintain the effectiveness of existing relay protection strategies. Considering that actual grid lines primarily exhibit inductive characteristics, existing circular current limiters with resistive characteristics clearly cannot meet the power system's requirements. Summary of the Invention

[0006] To address the problems mentioned in the prior art, this invention proposes a method, system, device, and storage medium for configuring the output impedance of a circular current limiter. This method enables free adjustment of the equivalent output impedance angle of the converter device while ensuring its safe operation, thereby ensuring that the converter device meets the protection requirements of the power system and providing a solution for the safe operation of the system.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides an output impedance configuration method for circular current limiters, applicable to grid-type GFM converters, comprising the following steps: S1. Obtain the output current, output voltage, and voltage reference signal of the grid-type GFM converter; S2. Based on the output voltage and the voltage reference signal, the original voltage control signal is calculated using proportional-integral control. S3. Calculate the enable signal based on the original voltage control signal and the output current; when the current amplitude required by the original voltage control signal exceeds the maximum allowable output current amplitude, generate a valid enable signal; S4. When the enable signal is valid, calculate the output impedance configuration signal based on the preset reactance-resistance ratio coefficient and the original voltage control signal. S5. Calculate the voltage control signal based on the output impedance configuration signal and the original voltage control signal; perform amplitude normalization processing on the voltage control signal to obtain the normalized voltage control signal. S6. Calculate and generate the original current reference signal based on the normalized voltage control signal and output current; S7. Input the original current reference signal to the circular current limiter for amplitude limitation, and output the limited current reference signal used to limit the output current of the grid-type GFM converter.

[0008] As a further improvement of the present invention, the output voltage in S1 includes the direct-axis voltage and the quadrature-axis voltage in the rotating coordinate system; Voltage reference signals include direct-axis voltage references and quadrature-axis voltage references in a rotating coordinate system; The output current includes the direct-axis output current and the quadrature-axis output current in the rotating coordinate system.

[0009] As a further improvement of the present invention, the calculation formula for obtaining the original voltage control signal through proportional-integral control in step S2 is as follows:

[0010] In the formula: and These are the direct-axis original voltage control signal and the quadrature-axis original voltage control signal, respectively. The proportional gain is for proportional-integral control; The integral gain for proportional-integral control; and These are the direct-axis voltage and the quadrature-axis voltage, respectively. and These are the direct-axis voltage reference and the quadrature-axis voltage reference, respectively.

[0011] As a further improvement of the present invention, the calculation formula for the enable signal in S3 is as follows:

[0012] In the formula: To enable the signal, when When it is 1, it is a valid enable signal. When the value is 0, it is an invalid enable signal; This is the maximum allowable output current amplitude; and These are the direct-axis original voltage control signal and the quadrature-axis original voltage control signal, respectively. and These are the direct-axis output current and the quadrature-axis output current, respectively.

[0013] As a further improvement of the present invention, the calculation of the output impedance configuration signal in S4 includes: Output impedance configuration signals include direct-axis output impedance configuration signals. and quadrature axis output impedance configuration signal The calculation formula is as follows:

[0014] In the formula: This is the preset reactance-resistance ratio coefficient; The proportional gain is for proportional-integral control; For enable signal; and These are the direct-axis output impedance configuration signal and the quadrature-axis output impedance configuration signal, respectively. and These are the direct-axis voltage and the quadrature-axis voltage, respectively. and These are the direct-axis voltage reference and the quadrature-axis voltage reference, respectively.

[0015] As a further improvement of the present invention, step S5 calculates a voltage control signal based on the output impedance configuration signal and the original voltage control signal; and performs amplitude normalization processing on the voltage control signal to obtain a normalized voltage control signal, including: The voltage control signal includes a direct-axis voltage control signal. and quadrature axis voltage control signal The calculation formula is as follows:

[0016] In the formula: and These are the direct-axis voltage control signal and the quadrature-axis voltage control signal, respectively. and These are the direct-axis original voltage control signal and the quadrature-axis original voltage control signal, respectively. and These are the direct-axis output impedance configuration signal and the quadrature-axis output impedance configuration signal, respectively. The voltage control signal is normalized to its amplitude, and the normalized voltage control signal is calculated as follows:

[0017] In the formula: and These are the normalized direct-axis voltage control signal and the normalized quadrature-axis voltage control signal, respectively. This is the preset reactance-resistance ratio coefficient; This is an enable signal.

[0018] As a further improvement of the present invention, the calculation and generation of the original current reference signal in step S6 includes: The normalized voltage control signal is summed with the output current to generate the original current reference signal, as shown in the following formula:

[0019] In the formula: and These are the direct-axis original current reference and the quadrature-axis original current reference, respectively. and These are the normalized direct-axis voltage control signal and the normalized quadrature-axis voltage control signal, respectively. and These are the direct-axis output current and the quadrature-axis output current, respectively.

[0020] As a further improvement of the present invention, the calculation formula for the current reference signal after limiting in S7 is as follows:

[0021] In the formula: and These are the current references after direct-axis limiting and the current references after quadrature-axis limiting, respectively. and These are the direct-axis original current reference and the quadrature-axis original current reference, respectively. This is an enable signal.

[0022] As a further improvement of the present invention, when the enable signal is valid, the integral control in the proportional-integral control is set to zero or frozen to prevent integral control saturation.

[0023] This invention proposes an output impedance configuration system for circular current limiters, comprising: The acquisition module is used to acquire the output current, output voltage, and voltage reference signal of the grid-type GFM converter. A proportional-integral control module is used to calculate the original voltage control signal based on the output voltage and the voltage reference signal through proportional-integral control. The enable signal calculation module is used to calculate the enable signal based on the original voltage control signal and the output current; when the current amplitude required by the original voltage control signal exceeds the maximum allowable output current amplitude, a valid enable signal is generated. The output impedance configuration calculation module is used to calculate the output impedance configuration signal based on the preset reactance-resistance ratio coefficient and the original voltage control signal when the enable signal is valid. The normalization processing module is used to calculate the voltage control signal based on the output impedance configuration signal and the original voltage control signal; and to perform amplitude normalization processing on the voltage control signal to obtain the normalized voltage control signal. The original current reference calculation module is used to calculate and generate the original current reference signal based on the normalized voltage control signal and the output current. A circular current limiter is used to input the original current reference signal to the circular current limiter for amplitude limitation, and outputs a limited current reference signal to limit the output current of the grid-type GFM converter.

[0024] Compared with the prior art, the present invention achieves the following technical effects: This invention introduces output impedance configuration, enabling the converter to actively exhibit a pre-set impedance characteristic after current limiting is triggered by grid disturbances. This significantly improves the ability of the circular current limiter to cope with different fault scenarios and ensures the converter's continuous grid-connected operation under harsh grid conditions. In addition, this method enables the converter's output impedance characteristics to actively meet the basic requirements of grid relay protection devices for power generation equipment, enhancing the grid's compatibility and support capabilities, and providing a foundation for the safe and stable operation of the power system. Furthermore, this invention achieves overcurrent protection for the converter under grid disturbances by adjusting the original current reference and utilizing the fast response characteristics of current control. Attached Figure Description

[0025] Figure 1 A schematic diagram of a network-type GFM control system with a current limiter in existing technology; Figure 2 This is a flowchart of the output impedance configuration method for a circular current limiter proposed in this invention. Figure 3 This is a schematic diagram of the enable signal calculation module in the output impedance configuration method proposed in this invention; Figure 4 The output impedance configuration method proposed in this invention is in A schematic diagram of a simulation example; Figure 5 The output impedance configuration method proposed in this invention is in A schematic diagram of a simulation example; Figure 6 The output impedance configuration method proposed in this invention is in A schematic diagram of a simulation example; Figure 7 This is a schematic diagram of the overall process of the present invention. Detailed Implementation

[0026] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0027] See Figure 2 and Figure 7 This embodiment proposes an output impedance configuration method for circular current limiters, applied to a grid-type GFM converter, including the following steps: S1. Obtain the output current, output voltage, and voltage reference signal of the grid-type GFM converter; S2. Based on the output voltage and the voltage reference signal, the original voltage control signal is calculated using proportional-integral control. S3. Calculate the enable signal based on the original voltage control signal and the output current; when the current amplitude required by the original voltage control signal exceeds the maximum allowable output current amplitude, generate a valid enable signal; S4. When the enable signal is valid, calculate the output impedance configuration signal based on the preset reactance-resistance ratio coefficient and the original voltage control signal. S5. Calculate the voltage control signal based on the output impedance configuration signal and the original voltage control signal; perform amplitude normalization processing on the voltage control signal to obtain the normalized voltage control signal. S6. Calculate and generate the original current reference signal based on the normalized voltage control signal and output current; S7. Input the original current reference signal to the circular current limiter for amplitude limitation, and output the limited current reference signal used to limit the output current of the grid-type GFM converter.

[0028] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments: The specific implementation method of this embodiment is as follows: This embodiment first acquires the output current, output voltage, and voltage reference signal; the output current is obtained by measuring the current sensor, including... and ,in This represents the direct-axis output current in a rotating coordinate system. This represents the quadrature-axis output current in a rotating coordinate system; the output voltage is obtained by measuring a voltage sensor, including... and ,in Represents the direct-axis voltage in a rotating coordinate system. Represents the quadrature-axis voltage in a rotating coordinate system; a voltage reference is obtained through a power controller, including... and ,in This represents the direct-axis voltage reference in a rotating coordinate system. This represents the quadrature-axis voltage reference in a rotating coordinate system.

[0029] In this embodiment, the deviation between the voltage reference signal and the output voltage is subjected to proportional-integral control to obtain the original voltage control signal. The specific calculation is as follows:

[0030] In the formula: and These are the direct-axis original voltage control signal and the quadrature-axis original voltage control signal, respectively. The proportional gain is for proportional-integral control; The integral gain for proportional-integral control; and These are the direct-axis voltage and the quadrature-axis voltage, respectively. and These are the direct-axis voltage reference and the quadrature-axis voltage reference, respectively.

[0031] See Figure 3 Based on the obtained original voltage control signal , With the measured output current and The enable signal is calculated to determine whether to enable the output impedance configuration method and current limiter proposed in this invention. The specific calculation is as follows:

[0032] In the formula: To enable the signal, when When it is 1, it is a valid enable signal. When the value is 0, it is an invalid enable signal; This is the maximum allowable output current amplitude; and These are the direct-axis original voltage control signal and the quadrature-axis original voltage control signal, respectively. and These are the direct-axis output current and the quadrature-axis output current, respectively.

[0033] It should be noted that, compared to the existing technology that directly calculates whether to enable the circular current limiter based on the output current, the enable signal calculation method proposed in this embodiment further introduces the original voltage control signal. and This changes the criterion for whether to enable the circular current limiter from being based on the actual output current. and It was changed to be based on the output current required to achieve the original voltage control signal. and This avoids the phenomenon that the enable signal oscillates due to current control errors, which in turn causes oscillations in the output voltage and output current.

[0034] This embodiment calculates the output impedance configuration signal based on the preset reactance-resistance ratio coefficient and the original voltage control signal. This signal is used to adjust the output impedance reactance-resistance ratio of the converter equipment during a fault. The specific calculation is as follows:

[0035] In the formula: This is the preset reactance-resistance ratio coefficient; The proportional gain is for proportional-integral control; For enable signal; and These are the direct-axis output impedance configuration signal and the quadrature-axis output impedance configuration signal, respectively. and These are the direct-axis voltage and the quadrature-axis voltage, respectively. and These are the direct-axis voltage reference and the quadrature-axis voltage reference, respectively.

[0036] In the embodiment, when the enable signal When it is 0, the impedance configuration signal and All values ​​are 0, meaning the output impedance configuration method given in this embodiment is not enabled.

[0037] In this embodiment, the voltage control signal is calculated based on the output impedance configuration signal and the original voltage control signal. The calculation formula is as follows:

[0038] In the formula: and These are the direct-axis voltage control signal and the quadrature-axis voltage control signal, respectively. and These are the direct-axis original voltage control signal and the quadrature-axis original voltage control signal, respectively. and These are the direct-axis output impedance configuration signal and the quadrature-axis output impedance configuration signal, respectively.

[0039] It should be noted that when the enable signal... When it is 0, due to the impedance configuration signal and If both are 0, then the voltage control signal , With the original voltage control signal , equal.

[0040] The voltage control signal is normalized to obtain the normalized voltage control signal. The specific calculation is as follows:

[0041] In the formula: and These are the normalized direct-axis voltage control signal and the normalized quadrature-axis voltage control signal, respectively. This is the preset reactance-resistance ratio coefficient; This is an enable signal.

[0042] It should be noted that when the enable signal... When it is 0, the normalized voltage control signal , With the original voltage control signal , equal.

[0043] The normalized voltage control signal is summed with the output current to generate the original current reference signal, as calculated below:

[0044] In the formula: and These are the direct-axis original current reference and the quadrature-axis original current reference, respectively. and These are the normalized direct-axis voltage control signal and the normalized quadrature-axis voltage control signal, respectively. and These are the direct-axis output current and the quadrature-axis output current, respectively.

[0045] The original current reference signal is input into the circular current limiter to generate the limited current reference signal, calculated as follows:

[0046] In the formula: and The current reference signal after direct-axis limiting and the current reference signal after quadrature-axis limiting are respectively rotated in the coordinate system; This is the preset reactance-resistance ratio coefficient; This is an enable signal.

[0047] See Figure 4 , Figure 4 In one embodiment of the proposed output impedance configuration method, the maximum allowable output current amplitude of the converter device is 1.2 times the per-unit value, and the reactance-resistance ratio of the output impedance is... The grid fault is set to 0, and the grid voltage drops from 1 per-unit value to 0.5 per-unit value in 0.1 seconds. As shown in the diagram, before the grid voltage drops, the voltage difference between the potential within phase a and the voltage at the phase a terminal is 0, meaning the converter's output impedance is 0. After the grid voltage drops in 0.1 seconds, the potential difference in phase a and the output current in phase a are in phase, meaning the converter's output impedance is purely resistive, and its reactance-resistance ratio is 0, consistent with the output impedance reactance-resistance ratio. Presets.

[0048] See Figure 5 , Figure 5In one embodiment of the proposed output impedance configuration method, the maximum allowable output current amplitude of the converter device is 1.2 times the per-unit value, and the reactance-resistance ratio of the output impedance is... The setting is 1, meaning the grid voltage drops from 1 per-unit value to 0.5 per-unit value in 0.1 seconds due to a grid fault. As shown in the diagram, before the grid voltage drop, the voltage difference between the potential within phase a (lagging by 45 degrees) and the voltage at the phase a terminal is 0, meaning the converter's output impedance is 0. However, after the grid voltage drops in 0.1 seconds, the potential difference in phase a (lagging by 45 degrees) is in phase with the phase a output current, meaning the converter's output impedance has equal reactance and resistance values, with a reactance-resistance ratio of 1, consistent with the output impedance reactance-resistance ratio. Presets.

[0049] See Figure 6 , Figure 6 In one embodiment of the proposed output impedance configuration method, the maximum allowable output current amplitude of the converter device is 1.2 times the per-unit value, and the reactance-resistance ratio of the output impedance is... The setting is 10. When the grid fault occurs in 0.1 seconds, the grid voltage drops from 1 per-unit value to 0.5 per-unit value. As shown in the graph, before the grid voltage drops, the voltage difference between the potential within phase a (lagging by 84.29 degrees) and the voltage at the phase a terminal is 0, meaning the converter's output impedance is 0. However, after the grid voltage drops in 0.1 seconds, the potential difference in phase a (lagging by 84.29 degrees) is in phase with the phase a output current, meaning the reactance-resistance ratio of the converter's output impedance is... It conforms to the output impedance reactance-resistance ratio Presets.

[0050] In addition, from Figure 4 , Figure 5 , Figure 6 As can be seen from the embodiments, after the grid voltage drops, the output current amplitude can be well maintained within 1.2 times the per-unit value, ensuring the safe operation of the converter equipment.

[0051] It should be particularly noted in this embodiment that: (1) When external interference causes the converter equipment to enter the current limit, the integral control in the voltage control should be set to zero or frozen to prevent integral control saturation.

[0052] (2) The output impedance configuration method proposed in this embodiment requires high-bandwidth current control to ensure the accurate realization of the current reference after the impedance is configured.

[0053] Based on the same inventive concept, this invention also provides an output impedance configuration system for a circular current limiter. Since the principle of this output impedance configuration system for a circular current limiter is similar to the aforementioned output impedance configuration method for a circular current limiter, the implementation of this output impedance configuration system for a circular current limiter can refer to the implementation of the output impedance configuration method for a circular current limiter, and the repeated parts will not be described again.

[0054] In specific implementation, the output impedance configuration system for circular current limiters provided in this embodiment of the invention specifically includes: The acquisition module is used to acquire the output current, output voltage, and voltage reference signal of the grid-type GFM converter. A proportional-integral control module is used to calculate the original voltage control signal based on the output voltage and the voltage reference signal through proportional-integral control. The enable signal calculation module is used to calculate the enable signal based on the original voltage control signal and the output current; when the current amplitude required by the original voltage control signal exceeds the maximum allowable output current amplitude, a valid enable signal is generated. The output impedance configuration calculation module is used to calculate the output impedance configuration signal based on the preset reactance-resistance ratio coefficient and the original voltage control signal when the enable signal is valid. The normalization processing module is used to calculate the voltage control signal based on the output impedance configuration signal and the original voltage control signal; and to perform amplitude normalization processing on the voltage control signal to obtain the normalized voltage control signal. The original current reference calculation module is used to calculate and generate the original current reference signal based on the normalized voltage control signal and the output current. A circular current limiter is used to input the original current reference signal to the circular current limiter for amplitude limitation, and outputs a limited current reference signal to limit the output current of the grid-type GFM converter.

[0055] Accordingly, embodiments of the present invention also provide an output impedance configuration device for a circular current limiter, including a processor and a memory, wherein the processor executes a computer program stored in the memory to implement the output impedance configuration method for a circular current limiter as provided in embodiments of the present invention.

[0056] For more detailed information on the above methods, please refer to the relevant content disclosed in the foregoing embodiments, which will not be repeated here.

[0057] Accordingly, embodiments of the present invention also provide a computer-readable storage medium for storing a computer program, wherein the computer program, when executed by a processor, implements the output impedance configuration method for a circular current limiter as described above in embodiments of the present invention.

[0058] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems, devices, and storage media disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple; relevant parts can be referred to the method section.

[0059] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0060] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein can be implemented directly by hardware, a software module executed by a processor, or a combination of both. The software module can be located in random access memory (RAM), main memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art.

[0061] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0062] The above provides a detailed description of the output impedance configuration method, system, device, and storage medium for circular current limiters provided by this invention. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this invention. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A method for configuring the output impedance of a circular current limiter, applied to a grid-type GFM converter, characterized in that, Includes the following steps: S1. Obtain the output current, output voltage, and voltage reference signal of the grid-type GFM converter; S2. Based on the output voltage and the voltage reference signal, the original voltage control signal is calculated using proportional-integral control. S3. Calculate the enable signal based on the original voltage control signal and the output current; when the current amplitude required by the original voltage control signal exceeds the maximum allowable output current amplitude, generate a valid enable signal; S4. When the enable signal is valid, calculate the output impedance configuration signal based on the preset reactance-resistance ratio coefficient and the original voltage control signal. S5. Calculate the voltage control signal based on the output impedance configuration signal and the original voltage control signal; The voltage control signal is normalized to obtain a normalized voltage control signal. S6. Calculate and generate the original current reference signal based on the normalized voltage control signal and output current; S7. Input the original current reference signal to the circular current limiter for amplitude limitation, and output the limited current reference signal used to limit the output current of the grid-type GFM converter.

2. The output impedance configuration method for a circular current limiter according to claim 1, characterized in that, The output voltage in S1 includes the direct-axis voltage and the quadrature-axis voltage in the rotating coordinate system; Voltage reference signals include direct-axis voltage references and quadrature-axis voltage references in a rotating coordinate system; The output current includes the direct-axis output current and the quadrature-axis output current in the rotating coordinate system.

3. The output impedance configuration method for a circular current limiter according to claim 1, characterized in that, The formula for calculating the original voltage control signal in S2 using proportional-integral control is as follows: In the formula: and These are the direct-axis original voltage control signal and the quadrature-axis original voltage control signal, respectively. The proportional gain is for proportional-integral control; The integral gain for proportional-integral control; and These are the direct-axis voltage and the quadrature-axis voltage, respectively. and These are the direct-axis voltage reference and the quadrature-axis voltage reference, respectively.

4. The output impedance configuration method for a circular current limiter according to claim 1, characterized in that, The formula for calculating the enable signal in S3 is as follows: In the formula: To enable the signal, when When it is 1, it is a valid enable signal. When the value is 0, it is an invalid enable signal; This is the maximum allowable output current amplitude; and These are the direct-axis original voltage control signal and the quadrature-axis original voltage control signal, respectively. and These are the direct-axis output current and the quadrature-axis output current, respectively.

5. The output impedance configuration method for a circular current limiter according to claim 1, characterized in that, The calculation of the output impedance configuration signal in S4 includes: Output impedance configuration signals include direct-axis output impedance configuration signals. and quadrature axis output impedance configuration signal The calculation formula is as follows: In the formula: This is the preset reactance-resistance ratio coefficient; The proportional gain is for proportional-integral control; For enable signal; and These are the direct-axis output impedance configuration signal and the quadrature-axis output impedance configuration signal, respectively. and These are the direct-axis voltage and the quadrature-axis voltage, respectively. and These are the direct-axis voltage reference and the quadrature-axis voltage reference, respectively.

6. The output impedance configuration method for a circular current limiter according to claim 1, characterized in that, S5 calculates the voltage control signal based on the output impedance configuration signal and the original voltage control signal; The voltage control signal is normalized to obtain a normalized voltage control signal, including: The voltage control signal includes a direct-axis voltage control signal. and quadrature axis voltage control signal The calculation formula is as follows: In the formula: and These are the direct-axis voltage control signal and the quadrature-axis voltage control signal, respectively. and These are the direct-axis original voltage control signal and the quadrature-axis original voltage control signal, respectively. and These are the direct-axis output impedance configuration signal and the quadrature-axis output impedance configuration signal, respectively. The voltage control signal is normalized to its amplitude, and the normalized voltage control signal is calculated as follows: In the formula: and These are the normalized direct-axis voltage control signal and the normalized quadrature-axis voltage control signal, respectively. This is the preset reactance-resistance ratio coefficient; This is an enable signal.

7. The output impedance configuration method for a circular current limiter according to claim 1, characterized in that, The calculation and generation of the original current reference signal in S6 includes: The normalized voltage control signal is summed with the output current to generate the original current reference signal, as shown in the following formula: In the formula: and These are the direct-axis original current reference and the quadrature-axis original current reference, respectively. and These are the normalized direct-axis voltage control signal and the normalized quadrature-axis voltage control signal, respectively. and These are the direct-axis output current and the quadrature-axis output current, respectively.

8. The output impedance configuration method for a circular current limiter according to claim 1, characterized in that, The formula for calculating the current reference signal after limiting in S7 is as follows: In the formula: and These are the current references after direct-axis limiting and the current references after quadrature-axis limiting, respectively. and These are the direct-axis original current reference and the quadrature-axis original current reference, respectively. This is an enable signal.

9. The output impedance configuration method for a circular current limiter according to claim 1, characterized in that, When the enable signal is valid, the integral control in the proportional-integral control is set to zero or frozen to prevent integral control saturation.

10. An output impedance configuration system for a circular current limiter, characterized in that, include: The acquisition module is used to acquire the output current, output voltage, and voltage reference signal of the grid-type GFM converter. A proportional-integral control module is used to calculate the original voltage control signal based on the output voltage and the voltage reference signal through proportional-integral control. The enable signal calculation module is used to calculate the enable signal based on the original voltage control signal and the output current; when the current amplitude required by the original voltage control signal exceeds the maximum allowable output current amplitude, a valid enable signal is generated. The output impedance configuration calculation module is used to calculate the output impedance configuration signal based on the preset reactance-resistance ratio coefficient and the original voltage control signal when the enable signal is valid. The normalization processing module is used to calculate the voltage control signal based on the output impedance configuration signal and the original voltage control signal; The voltage control signal is normalized to obtain a normalized voltage control signal. The original current reference calculation module is used to calculate and generate the original current reference signal based on the normalized voltage control signal and the output current. A circular current limiter is used to input the original current reference signal to the circular current limiter for amplitude limitation, and outputs a limited current reference signal to limit the output current of the grid-type GFM converter.

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