Method and device for suppressing dc current bias component of a load reactor

Abstract

The application provides a method and device for suppressing a DC current bias component of a load reactor. The DC current bias component can be extracted from an actual value of a first AC current of the load reactor, and then a modulation voltage of a bridge arm is calculated according to the DC current bias component, and the DC current bias component is suppressed according to the modulation voltage of the bridge arm. The application takes the actual value of the first AC current of the load reactor itself as a feedback source, eliminates compensation deviations caused by intermediate links such as internal voltage drops of a converter, line impedance, sensor gain error and the like, realizes closed-loop negative feedback control, effectively suppresses the DC current bias component, and improves suppression precision.

Description

Technical Field

[0001] This application relates to the technical field, specifically to a method and apparatus for suppressing the DC current bias component of a load reactor. Background Technology

[0002] With the rapid development of new energy technologies, pilot-scale platforms for flexible DC transmission systems have been extensively studied. The converter is the core equipment of a flexible DC transmission system. The converter (which can be a modular multilevel converter, etc.) can have an H-bridge topology and may include multiple arms and load reactors. The parameters of the upper and lower arms are not entirely consistent; for example, differences exist in reactance, resistance, capacitance, and the number of submodules. This results in a DC current bias component in the actual AC current of the load reactor, easily leading to unidirectional deep saturation of the core, which in turn triggers a series of cascading faults, and in severe cases, burns out the converter.

[0003] However, due to the complex and variable operating conditions of flexible DC transmission systems, such as changes in power transmission direction and rapid load changes, high demands are placed on the suppression of DC current bias components. Therefore, there is an urgent need for a technical solution that can effectively and accurately suppress the DC current bias components of the load reactor. Summary of the Invention

[0004] This application provides a method and apparatus for suppressing the DC current bias component of a load reactor.

[0005] In a first aspect, this application provides a method for suppressing the DC current bias component of a load reactor, which may include: Extract the DC current bias component from the actual value of the first AC current of the load reactor.

[0006] The modulation voltage of the bridge arm is calculated based on the DC current bias component.

[0007] The DC current bias component is suppressed based on the modulation voltage of the bridge arm.

[0008] In some possible implementations, the DC current bias component is extracted from the actual AC current value of the load reactor, including: Collect the actual value of the first AC current of the load reactor.

[0009] The actual value of the first AC current of the load reactor is filtered to obtain the actual value of the second AC current of the load reactor.

[0010] Extract the DC current bias component from the actual value of the second AC current of the load reactor.

[0011] In some other possible implementations, the modulation voltage of the bridge arm is calculated based on the DC current bias component, including: The difference between the preset component of the DC current and the bias component of the DC current is subjected to proportional-integral control to obtain the modulation voltage of the bridge arm.

[0012] In some other possible implementations, the DC current bias component is suppressed based on the modulation voltage of the bridge arm, including: Calculate the bridge arm reference voltage for phase A or phase B based on the modulation voltage of the bridge arm.

[0013] The bridge arm is controlled based on the bridge arm reference voltage of phase A or phase B.

[0014] Optionally, the bridge arm reference voltage of phase A satisfies:

[0015]

[0016] in, This represents the reference voltage of the first upper arm in phase A. This represents the reference voltage of the first lower arm in phase A. This represents the voltage between the poles of the converter and ground. This represents the voltage reference value for phase A. This represents the DC current bias component.

[0017] For example, the reference voltage of the bridge arm of phase B satisfies:

[0018]

[0019] in, This represents the reference voltage of the first upper arm of bridge B. This represents the reference voltage of the first lower arm of bridge B. This represents the voltage between the poles of the converter and ground. This represents the voltage reference value of B. This represents the DC current bias component.

[0020] Secondly, this application provides a device for suppressing the DC current bias component of a load reactor, which may include: The extraction module is used to extract the DC current bias component from the actual value of the first AC current of the load reactor.

[0021] The calculation module is used to calculate the modulation voltage of the bridge arm based on the DC current bias component.

[0022] The suppression module is used to suppress the DC current bias component based on the modulation voltage of the bridge arm.

[0023] In some possible implementations, the extraction module is specifically used for: Collect the actual value of the first AC current of the load reactor.

[0024] The actual value of the first AC current of the load reactor is filtered to obtain the actual value of the second AC current of the load reactor.

[0025] Extract the DC current bias component from the actual value of the second AC current of the load reactor.

[0026] In some other possible implementations, the computation module is specifically used for: The difference between the preset component of the DC current and the bias component of the DC current is subjected to proportional-integral control to obtain the modulation voltage of the bridge arm.

[0027] In some other possible implementations, the suppression module is specifically used for: Calculate the bridge arm reference voltage for phase A or phase B based on the modulation voltage of the bridge arm.

[0028] The bridge arm is controlled based on the bridge arm reference voltage of phase A or phase B.

[0029] Optionally, the suppression module calculates the bridge arm reference voltage of phase A using the following formula:

[0030]

[0031] in, This represents the reference voltage of the first upper arm in phase A. This represents the reference voltage of the first lower arm in phase A. This represents the voltage between the poles of the converter and ground. This represents the voltage reference value for phase A. This represents the DC current bias component.

[0032] For example, the suppression module calculates the bridge arm reference voltage of phase B using the following formula:

[0033]

[0034] in, This represents the reference voltage of the first upper arm of bridge B. This represents the reference voltage of the first lower arm of bridge B. This represents the voltage between the poles of the converter and ground. This represents the voltage reference value of B. This represents the DC current bias component.

[0035] In another aspect, this application also provides a computer device, including: one or more processors.

[0036] A processor is used to execute one or more programs.

[0037] When one or more programs are executed by one or more processors, the suppression method described above is implemented.

[0038] Furthermore, this application also provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed, it implements the suppression method described above.

[0039] Compared with the prior art, the beneficial effects of this application are as follows: The method for suppressing the DC current bias component of a load reactor provided in this application first extracts the DC current bias component from the actual value of the first AC current of the load reactor. Then, the modulation voltage of the bridge arm is calculated based on the DC current bias component, and the DC current bias component is suppressed based on the modulation voltage of the bridge arm. This application uses the actual value of the first AC current of the load reactor itself as the feedback source, eliminating compensation deviations caused by intermediate links such as voltage drop inside the converter, line impedance, and sensor gain error, realizing closed-loop negative feedback control, achieving effective suppression of the DC current bias component, and improving the suppression accuracy.

[0040] This application eliminates the need for the charging and discharging process of the DC blocking capacitor (the time constant is typically tens of milliseconds to several seconds), and also eliminates the need for mechanical operations such as adjusting the air gap of the load reactor. The response speed is limited only by the control cycle, meaning that the dynamic response speed is fast, thus improving the suppression efficiency.

[0041] This application can effectively suppress DC current bias components generated during dynamic processes such as load changes, grid voltage drops / asymmetry, and converter switching, and has strong transient suppression capability.

[0042] This application uses the modulation voltage of the bridge arm as a compensation quantity, combined with the voltage reference value, which will not generate additional switching harmonics or low-order harmonics and will not have a negative impact on the power quality of the power grid. In addition, this application maintains the original inductance, filtering characteristics and reactive power compensation capability of the load reactor, and will not affect the harmonic suppression effect and dynamic response performance of the converter.

[0043] This application can adjust the modulation voltage of the bridge arm according to the actual value of the first AC current of the load reactor, exhibiting strong adaptability. Furthermore, it can adapt to various operating conditions such as grid voltage fluctuations, load changes, and temperature variations, and the compensation effect is unaffected by converter parameter drift, demonstrating strong adaptability to operating conditions.

[0044] This application can use methods such as the moving average method and the generalized integrator method to extract the DC current bias component, which can effectively suppress the influence of harmonics and noise on the detection accuracy and further improve the suppression accuracy. Attached Figure Description

[0045] To more clearly illustrate the technical solutions in this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0046] Figure 1 This is a schematic structural diagram of a converter in one embodiment of this application; Figure 2 This is a schematic flowchart of a method for suppressing the DC current bias component of a load reactor in an embodiment of this application; Figure 3 This is a schematic flowchart illustrating the extraction of DC current bias component from the actual AC current value of the load reactor in an embodiment of this application. Figure 4 This is a schematic flowchart illustrating the calculation of the modulation voltage of the bridge arm based on the DC current bias component in an embodiment of this application. Figure 5 This is a schematic structural diagram of a device for suppressing the DC current bias component of a load reactor in an embodiment of this application. Detailed Implementation

[0047] The technical solutions in this application will now be described with reference to the accompanying drawings.

[0048] The terms "first," "second," etc., used in the specification, embodiments, claims, and drawings of this application are for distinguishing purposes only and should not be construed as indicating or implying relative importance or order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion, such as including a series of steps or units. A method, system, product, or apparatus is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products, or apparatuses.

[0049] It should be understood that in this application, "at least one (item)" means one or more, and "more than" means two or more. "And / or" is used to describe the relationship between related objects, indicating that three relationships can exist. For example, "A and / or B" can represent three cases: only A exists, only B exists, and both A and B exist simultaneously, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one (item) of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one (item) of a, b, or c can represent: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, and c can be single or multiple.

[0050] Example 1: This application provides a method for suppressing the DC current bias component of a load reactor. The load reactor is a converter. For example... Figure 1 As shown, the converter 100 may include a first upper bridge arm 11, a first lower bridge arm 12, a second upper bridge arm 13, a second lower bridge arm 14, and a load reactor L1.

[0051] The first end of each of the first upper bridge arm 11 and the second upper bridge arm 13 is connected to the positive DC bus DC+. The second end of the first upper bridge arm 11 and the first end of the first lower bridge arm 12 are connected to the first end of the load reactor L1. The second end of the second upper bridge arm 13 and the first end of the second lower bridge arm 14 are connected to the second end of the load reactor L1. The first end of each of the first lower bridge arm 12 and the second lower bridge arm 14 is connected to the negative DC bus DC-. The converter 100 can be connected to the converter 200 through the positive DC bus DC+ and the negative DC bus DC-. The converter 200 can be connected to the AC power grid S through the transformer T.

[0052] like Figure 2 As shown, the suppression method 300 includes the following steps: Step S1: Extract the DC current bias component from the actual value of the first AC current of the load reactor.

[0053] Step S2: Calculate the modulation voltage of the bridge arm based on the DC current bias component.

[0054] Step S3: Suppress the DC current bias component based on the modulation voltage of the bridge arm.

[0055] In some possible implementations, step S1 extracts the DC current bias component from the actual AC current value of the load reactor, such as... Figure 3 As shown, it includes: Step S11: Acquire the actual value of the first AC current of the load reactor. In this embodiment, a current transformer can be installed on the load reactor to acquire the actual value of the first AC current.

[0056] Step S12: Filter the actual value of the first AC current of the load reactor (it can be a low-pass filter with a cutoff frequency of 5Hz) to obtain the actual value of the second AC current of the load reactor.

[0057] Step S13: Extract the DC current bias component from the actual value of the second AC current of the load reactor.

[0058] In some other possible implementations, step S2 involves calculating the modulation voltage of the bridge arm based on the DC current bias component, including: like Figure 4 As shown, the preset component of DC current With DC current bias component The difference Proportional-integral control (PI control) is performed to obtain the modulation voltage of the bridge arm. .

[0059] In some other possible implementations, the DC current bias component is suppressed based on the modulation voltage of the bridge arm, including: According to the modulation voltage of the bridge arm Calculate the bridge arm reference voltage for phase A or phase B.

[0060] The bridge arm is controlled based on the bridge arm reference voltage of phase A or phase B.

[0061] Optionally, the bridge arm reference voltage of phase A satisfies:

[0062]

[0063] in, This represents the reference voltage of the first upper arm in phase A. This represents the reference voltage of the first lower arm in phase A. This represents the voltage between the poles of the converter and ground. This represents the voltage reference value for phase A. This represents the DC current bias component.

[0064] For example, the reference voltage of the bridge arm of phase B satisfies:

[0065]

[0066] in, This represents the reference voltage of the first upper arm of bridge B. This represents the reference voltage of the first lower arm of bridge B. This represents the voltage between the poles of the converter and ground. This represents the voltage reference value of B. This represents the DC current bias component.

[0067] Example 2: Based on the same inventive concept, this application also provides a method for suppressing the DC current bias component of a load reactor. The load reactor is a converter. For an introduction to converters, please refer to the above and... Figure 1 The embodiments in this application will not be described in detail.

[0068] like Figure 5 As shown, the suppression device 400 may include: Extraction module 401 is used to extract the DC current bias component from the actual value of the first AC current of the load reactor.

[0069] The calculation module 402 is used to calculate the modulation voltage of the bridge arm based on the DC current bias component.

[0070] Suppression module 403 is used to suppress the DC current bias component based on the modulation voltage of the bridge arm.

[0071] In some possible implementations, the extraction module 401 is specifically used for: Collect the actual value of the first AC current of the load reactor.

[0072] The actual value of the first AC current of the load reactor is filtered to obtain the actual value of the second AC current of the load reactor.

[0073] Extract the DC current bias component from the actual value of the second AC current of the load reactor.

[0074] In some other possible implementations, the computing module 302 is specifically used for: like Figure 4 As shown, the preset component of DC current With DC current bias component The difference Proportional-integral control (PI control) is performed to obtain the modulation voltage of the bridge arm. .

[0075] In some other possible implementations, the suppression module 303 is specifically used for: Calculate the bridge arm reference voltage for phase A or phase B based on the modulation voltage of the bridge arm.

[0076] The bridge arm is controlled based on the bridge arm reference voltage of phase A or phase B.

[0077] Optionally, the suppression module calculates the bridge arm reference voltage of phase A using the following formula:

[0078]

[0079] in, This represents the reference voltage of the first upper arm in phase A. This represents the reference voltage of the first lower arm in phase A. This represents the voltage between the poles of the converter and ground. This represents the voltage reference value for phase A. This represents the DC current bias component.

[0080] For example, the suppression module calculates the bridge arm reference voltage of phase B using the following formula:

[0081]

[0082] in, This represents the reference voltage of the first upper arm of bridge B. This represents the reference voltage of the first lower arm of bridge B. This represents the voltage between the poles of the converter and ground. This represents the voltage reference value of B. This represents the DC current bias component.

[0083] Example 3: Based on the same inventive concept, this application also provides a computer device, which includes a processor and a memory. The memory stores a computer program, which includes program instructions. The processor executes the program instructions stored in the computer storage medium. The processor may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing and control core of the terminal, and is suitable for implementing one or more instructions. Specifically, it is suitable for loading and executing one or more instructions in the computer storage medium to implement the corresponding method flow or corresponding function, so as to implement the steps of the suppression method provided in the above embodiments.

[0084] Example 4: Based on the same inventive concept, this application also provides a computer-readable storage medium, specifically a computer-readable storage medium (Memory). A computer-readable storage medium is a memory device in a computer device used to store programs and data. It is understood that the computer-readable storage medium here can include both the built-in storage medium in the computer device and extended storage media supported by the computer device. The computer-readable storage medium provides storage space that stores the terminal's operating system. Furthermore, the storage space also stores one or more instructions suitable for loading and execution by a processor. These instructions can be one or more computer programs (including program code). It should be noted that the computer-readable storage medium here can be high-speed RAM or non-volatile memory, such as at least one disk storage device. The processor can load and execute one or more instructions stored in the computer-readable storage medium to implement the steps of the suppression method provided in the above embodiments.

[0085] Those skilled in the art will understand that the embodiments of the application can be provided as a method, system, or computer program product. Therefore, the application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the application can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0086] The application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0087] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0088] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0089] The above are merely examples of the application and are not intended to limit the application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the application shall be included within the scope of the claims of the pending application.

Claims

1. A method for suppressing the DC current bias component of a load reactor, characterized in that, include: Extract the DC current bias component from the actual value of the first AC current of the load reactor; The modulation voltage of the bridge arm is calculated based on the DC current bias component. The DC current bias component is suppressed based on the modulation voltage of the bridge arm.

2. The suppression method according to claim 1, characterized in that, The extraction of the DC current bias component from the actual AC current value of the load reactor includes: Collect the actual value of the first AC current of the load reactor; The actual value of the first AC current of the load reactor is filtered to obtain the actual value of the second AC current of the load reactor. The DC current bias component is extracted from the actual value of the second AC current of the load reactor.

3. The suppression method according to claim 1, characterized in that, The step of calculating the modulation voltage of the bridge arm based on the DC current bias component includes: The difference between the preset component of the DC current and the bias component of the DC current is subjected to proportional-integral control to obtain the modulation voltage of the bridge arm.

4. The suppression method according to claim 1, characterized in that, The suppression of the DC current bias component based on the modulation voltage of the bridge arm includes: Calculate the bridge arm reference voltage of phase A or the bridge arm reference voltage of phase B based on the modulation voltage of the bridge arm. The bridge arm is controlled based on the bridge arm reference voltage of phase A or the bridge arm reference voltage of phase B.

5. The suppression method according to claim 4, characterized in that, The bridge arm reference voltage of phase A satisfies: in, This represents the reference voltage of the first upper arm in phase A. This represents the reference voltage of the first lower bridge arm in phase A. This represents the voltage between the poles of the converter and ground. This represents the voltage reference value for phase A. This represents the DC current bias component.

6. The suppression method according to claim 4, characterized in that, The bridge arm reference voltage of phase B satisfies: in, This represents the reference voltage of the first upper bridge arm in section B. This represents the reference voltage of the first lower bridge arm in section B. This represents the voltage between the poles of the converter and ground. This represents the voltage reference value of B. This represents the DC current bias component.

7. A device for suppressing the DC bias component of an AC load current, characterized in that, include: The extraction module is used to extract the DC current bias component from the actual value of the first AC current of the load reactor; The calculation module is used to calculate the modulation voltage of the bridge arm based on the DC current bias component; The suppression module is used to suppress the DC current bias component based on the modulation voltage of the bridge arm.

8. The suppression device according to claim 7, characterized in that, The extraction module is specifically used for: Collect the actual value of the first AC current of the load reactor; The actual value of the first AC current of the load reactor is filtered to obtain the actual value of the second AC current of the load reactor. The DC current bias component is extracted from the actual value of the second AC current of the load reactor.

9. The suppression device according to claim 7, characterized in that, The calculation module is specifically used for: The difference between the preset component of the DC current and the bias component of the DC current is subjected to proportional-integral control to obtain the modulation voltage of the bridge arm.

10. The suppression device according to claim 7, characterized in that, The suppression module is specifically used for: Calculate the bridge arm reference voltage of phase A or the bridge arm reference voltage of phase B based on the modulation voltage of the bridge arm. The bridge arm is controlled based on the bridge arm reference voltage of phase A or the bridge arm reference voltage of phase B.

11. The suppression device according to claim 10, characterized in that, The suppression module calculates the bridge arm reference voltage of phase A using the following formula: in, This represents the reference voltage of the first upper arm in phase A. This represents the reference voltage of the first lower bridge arm in phase A. This represents the voltage between the poles of the converter and ground. This represents the voltage reference value for phase A. This represents the DC current bias component.

12. The suppression device according to claim 10, characterized in that, The suppression module calculates the bridge arm reference voltage of phase B using the following formula: in, This represents the reference voltage of the first upper bridge arm in section B. This represents the reference voltage of the first lower bridge arm in section B. This represents the voltage between the poles of the converter and ground. This represents the voltage reference value of B. This represents the DC current bias component.

13. A computer device, characterized in that, include: One or more processors; The processor is used to store one or more programs; When the one or more programs are executed by the one or more processors, the suppression method as described in any one of claims 1 to 7 is implemented.

14. A computer-readable storage medium, characterized in that, It contains a computer program, which, when executed, implements the suppression method as described in any one of claims 1 to 7.

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