A method and apparatus for suppressing a second harmonic current component

Abstract

This application provides a method and apparatus for suppressing second-harmonic current components. The method extracts the second-harmonic current components from the actual current values ​​of each bridge arm of the converter, then calculates the first modulation voltage of the converter based on the second-harmonic current components, and subsequently suppresses the second-harmonic current components based on the first modulation voltage of the converter. This application directly extracts the second-harmonic current components from the actual current values ​​of each bridge arm, resulting in a small adjustment delay and fast dynamic response. Furthermore, it is adaptable to various operating conditions across the entire power range, adaptively adjusts to frequency shifts, and provides stable suppression performance.

Description

Technical Field

[0001] This application relates to the field of flexible DC transmission technology, specifically to a method and apparatus for suppressing second harmonic current components. Background Technology

[0002] In flexible DC transmission systems, the second harmonic component of the arm current (or simply the second harmonic current component) is an inherent characteristic of converters (such as modular multilevel converters) during operation. This can lead to voltage fluctuations in submodule capacitors, increased electrical stress on semiconductor power devices, reduced converter efficiency and reliability, and even malfunctions in protection devices. Therefore, suppressing the second harmonic current component is crucial for verifying the feasibility of control strategies, optimizing dynamic performance, extending equipment lifespan, and ensuring the safe and stable operation of future practical projects. It is an important research area for promoting the maturity and large-scale application of flexible DC transmission technology.

[0003] Related technologies employ feedforward decoupling control or proportional resonant control to achieve closed-loop suppression of the second harmonic current component. Feedforward decoupling control extracts and calculates the second harmonic negative-sequence current component, generating a corresponding compensation voltage feedforward injection control to counteract its influence. Proportional resonant control utilizes the high-gain characteristic of proportional resonance at a specific frequency (e.g., 100Hz) to track and suppress current errors at that frequency without steady-state error. However, the suppression effect is highly dependent on the accuracy of system parameters (e.g., bridge arm inductance, submodule capacitance, etc.), and in real-world scenarios, these parameters drift due to temperature changes, aging, and other factors, leading to a mismatch between the controller's design and actual values. This significantly weakens the suppression effect and may even cause instability in flexible DC transmission systems. The second harmonic current component is strongly coupled with the fundamental power and DC component, presenting a complex, multivariable, and nonlinear control problem. Simple linearization control or single-frequency control cannot adapt to full-power conditions, cannot effectively suppress the second harmonic current, and exhibits slow dynamic response and poor adaptability. Summary of the Invention

[0004] To address the problems of slow dynamic response and poor adaptability in existing technologies, this application provides a method and apparatus for suppressing second harmonic current components.

[0005] In a first aspect, this application provides a method for suppressing second harmonic current components, which may include: Extract the second harmonic current component from the actual current values ​​of each bridge arm of the converter.

[0006] The first modulation voltage of the converter is calculated based on the second harmonic current component.

[0007] The second harmonic current component is suppressed based on the first modulation voltage of the converter.

[0008] In some possible implementations, the second harmonic current component is extracted from the actual current values ​​of each arm of the converter, including: Obtain the actual current values ​​of the first upper bridge arm, the first lower bridge arm, the second upper bridge arm, and the second lower bridge arm in the converter.

[0009] Calculate the second harmonic component of phase A based on the actual current values ​​of the first upper bridge arm, the first lower bridge arm, the second upper bridge arm, and the second lower bridge arm.

[0010] Phase shifting of the second harmonic component of phase A yields the second harmonic components of phase B and phase C.

[0011] In some other possible implementations, the first modulation voltage of the converter is calculated based on the second harmonic current component, including: By performing Parker transformation on the second harmonic components of phase A, phase B, and phase C, the first current components of the converter along the d-axis and q-axis in the dq coordinate system are obtained.

[0012] The first current component on the d-axis and the first current component on the q-axis are filtered to obtain the second current component on the d-axis and the second current component on the q-axis.

[0013] By performing proportional-integral control and decoupling control on the second current component of the d-axis and the second current component of the q-axis, the second modulation voltage of the converter in the dq coordinate system is obtained.

[0014] By applying amplitude limiting control to the second modulation voltage on the d-axis and the second modulation voltage on the q-axis, the first modulation voltage on the d-axis and the first modulation voltage on the q-axis of the converter in the dq coordinate system are obtained.

[0015] In some other possible implementations, the second harmonic current component is suppressed based on the first modulation voltage of the converter, including: The first modulation voltage of the converter is subjected to an inverse Park transform to obtain the first second harmonic compensation voltage of the converter in the abc coordinate system.

[0016] The second harmonic compensation voltage of the converter is calculated based on the first harmonic compensation voltage.

[0017] The fundamental voltage of the first phase in the converter is added to the second harmonic compensation voltage to obtain the modulation voltage of the first phase.

[0018] The modulation voltage of the second phase is obtained by subtracting the fundamental voltage of the second phase from the second harmonic compensation voltage.

[0019] The first phase submodule is controlled based on the modulation voltage of the first phase, and the second phase submodule is controlled based on the modulation voltage of the second phase.

[0020] Optionally, the second harmonic compensation voltage satisfies: .in, This represents the second harmonic compensation voltage. This represents the first and second harmonic compensation voltage.

[0021] For example, the second modulation voltage along the d-axis and the second modulation voltage along the q-axis satisfy: .

[0022] in, This represents the second modulation voltage along the d-axis. This represents the second modulation voltage along the q-axis. Indicates the modulation ratio of the converter. This represents the DC voltage of the converter.

[0023] Optionally, the second modulation voltage along the d-axis and the second modulation voltage along the q-axis satisfy:

[0024]

[0025] in, This represents the second modulation voltage along the d-axis. This represents the second modulation voltage along the q-axis. This represents the second current component along the d-axis. This represents the second current component along the q-axis. This represents the reference value for the d-axis current component. This represents the reference value for the q-axis current component. This represents the first proportionality coefficient. This represents the first integral coefficient. This represents the second proportionality coefficient. Let denote the second integral coefficient. s denotes the Laplace operator. This indicates the inductance value of the bridge arm inductance. This indicates the inductance value of the adjustable inductor in the load branch of the converter. This represents the angular frequency of the AC power grid.

[0026] The second harmonic component of phase A satisfies: .

[0027] in, This represents the second harmonic component of phase A. This represents the actual current value of the first upper bridge arm. This indicates the actual current value of the first lower bridge arm. This indicates the actual current value of the second upper bridge arm. This indicates the actual current value of the second lower bridge arm.

[0028] Secondly, this application provides a device for suppressing second harmonic current components, which may include: The extraction module is used to extract the second harmonic current component from the actual current values ​​of each bridge arm of the converter.

[0029] The calculation module is used to calculate the first modulation voltage of the converter based on the second harmonic current component.

[0030] The suppression module is used to suppress the second harmonic current component based on the first modulation voltage of the converter.

[0031] In some possible implementations, the extraction module is specifically used for: Obtain the actual current values ​​of the first upper bridge arm, the first lower bridge arm, the second upper bridge arm, and the second lower bridge arm in the converter.

[0032] Calculate the second harmonic component of phase A based on the actual current values ​​of the first upper bridge arm, the first lower bridge arm, the second upper bridge arm, and the second lower bridge arm.

[0033] Phase shifting of the second harmonic component of phase A yields the second harmonic components of phase B and phase C.

[0034] In some other possible implementations, the computation module is used for: By performing Parker transformation on the second harmonic components of phase A, phase B, and phase C, the first current components of the converter along the d-axis and q-axis in the dq coordinate system are obtained.

[0035] The first current component on the d-axis and the first current component on the q-axis are filtered to obtain the second current component on the d-axis and the second current component on the q-axis.

[0036] By performing proportional-integral control and decoupling control on the second current component of the d-axis and the second current component of the q-axis, the second modulation voltage of the converter in the dq coordinate system is obtained.

[0037] By applying amplitude limiting control to the second modulation voltage on the d-axis and the second modulation voltage on the q-axis, the first modulation voltage on the d-axis and the first modulation voltage on the q-axis of the converter in the dq coordinate system are obtained.

[0038] In some other possible implementations, the suppression module is specifically used for: The first modulation voltage of the converter is subjected to an inverse Park transform to obtain the first second harmonic compensation voltage of the converter in the abc coordinate system.

[0039] The second harmonic compensation voltage of the converter is calculated based on the first harmonic compensation voltage.

[0040] The fundamental voltage of the first phase in the converter is added to the second harmonic compensation voltage to obtain the modulation voltage of the first phase.

[0041] The modulation voltage of the second phase is obtained by subtracting the fundamental voltage of the second phase from the second harmonic compensation voltage.

[0042] The first phase submodule is controlled based on the modulation voltage of the first phase, and the second phase submodule is controlled based on the modulation voltage of the second phase.

[0043] Optionally, the second harmonic compensation voltage satisfies: .in, This represents the second harmonic compensation voltage. This represents the first and second harmonic compensation voltage.

[0044] For example, the second modulation voltage along the d-axis and the second modulation voltage along the q-axis satisfy: .

[0045] in, This represents the second modulation voltage along the d-axis. This represents the second modulation voltage along the q-axis. Indicates the modulation ratio of the converter. This represents the DC voltage of the converter.

[0046] Optionally, the second modulation voltage along the d-axis and the second modulation voltage along the q-axis satisfy:

[0047]

[0048] in, This represents the second modulation voltage along the d-axis. This represents the second modulation voltage along the q-axis. This represents the second current component along the d-axis. This represents the second current component along the q-axis. This represents the reference value for the d-axis current component. This represents the reference value for the q-axis current component. This represents the first proportionality coefficient. This represents the first integral coefficient. This represents the second proportionality coefficient. Let denote the second integral coefficient. s denotes the Laplace operator. This indicates the inductance value of the bridge arm inductance. This indicates the inductance value of the adjustable inductor in the load branch of the converter. This represents the angular frequency of the AC power grid.

[0049] The second harmonic component of phase A satisfies: .

[0050] in, This represents the second harmonic component of phase A. This represents the actual current value of the first upper bridge arm. This indicates the actual current value of the first lower bridge arm. This indicates the actual current value of the second upper bridge arm. This indicates the actual current value of the second lower bridge arm.

[0051] In another aspect, this application also provides a computer device, including: one or more processors.

[0052] A processor is used to execute one or more programs.

[0053] When one or more programs are executed by one or more processors, the suppression method described above is implemented.

[0054] 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.

[0055] Compared with the prior art, the beneficial effects of this application are as follows: The method for suppressing the second harmonic current component provided in this application extracts the second harmonic current component from the actual current value of each bridge arm of the converter, then calculates the first modulation voltage of the converter based on the second harmonic current component, and subsequently suppresses the second harmonic current component based on the first modulation voltage of the converter. This application directly extracts the second harmonic current component from the actual current value of each bridge arm, resulting in a small adjustment delay and fast dynamic response speed; in addition, it can adapt to various operating conditions across the entire power range, adaptively adjusts frequency offset, and provides stable suppression effect.

[0056] This application eliminates the need for complex coordinate transformations and low-pass filtering delays, extracts and calculates the first modulation voltage of the converter on-site and in real time, and can quickly track and suppress the abrupt second harmonic current component, further improving the dynamic response speed.

[0057] This application directly uses closed-loop correction based on the actual current value of the bridge arm, which is unaffected by parameter drift, operating condition fluctuations, and changes in line impedance. It does not rely on a precise mathematical model and has strong anti-disturbance capability.

[0058] It directly extracts the true second harmonic component for closed-loop regulation, adapting to various operating conditions such as full power range, light and heavy load, and transient power step. It does not require fixed-point frequency locking, can adapt to small frequency offsets of the second harmonic, and can stably suppress the second harmonic current under all operating conditions, further improving the suppression adaptability.

[0059] This application performs Parker transformation on the three-phase second harmonic components to achieve zero steady-state error extraction of the second harmonic current components, thereby improving the suppression accuracy and providing strong real-time suppression performance.

[0060] This application employs independent proportional-integral control and limiting of the dq axes to avoid overmodulation and suppress the second harmonic current component without affecting the stability of the fundamental wave control and the flexible DC transmission system.

[0061] This application adopts a modular design, which has strong engineering adaptability, low computational load, and high modularity. It can be directly implemented in the control and protection system of the test station and is suitable for simulating the bridge arm current harmonic conditions of flexible DC transmission projects. Attached Figure Description

[0062] 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.

[0063] 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 second harmonic current component in an embodiment of this application; Figure 3 This is a schematic flowchart illustrating the calculation of the first modulation voltage of the converter in an embodiment of this application; Figure 4 This is a schematic structural diagram of a second harmonic current component suppression device in an embodiment of this application. Detailed Implementation

[0064] The technical solutions in this application will now be described with reference to the accompanying drawings.

[0065] 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.

[0066] 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.

[0067] Example 1: Flexible DC transmission systems can include converters (such as modular multilevel converters), which comprise multiple arms. 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.

[0068] 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.

[0069] To suppress the second harmonic component of the bridge arm current, embodiments of this application provide a method for suppressing the second harmonic current component. For example... Figure 2 As shown, the suppression method 300 includes the following steps: Step S1: Extract the second harmonic current component from the actual current values ​​of each bridge arm of the converter.

[0070] Step S2: Calculate the first modulation voltage of the converter based on the second harmonic current component.

[0071] Step S3: Suppress the second harmonic current component based on the first modulation voltage of the converter.

[0072] In this embodiment, the converter can be a modular multilevel converter, can be an H-bridge topology, and can include four bridge arms, namely a first upper bridge arm, a first lower bridge arm, a second upper bridge arm, and a second lower bridge arm.

[0073] In some possible implementations, step S1 above, extracting the second harmonic current component from the actual current values ​​of each bridge arm of the converter, includes: The actual current values ​​of the first upper bridge arm, the first lower bridge arm, the second upper bridge arm, and the second lower bridge arm in the converter are obtained. In this embodiment, current sensors can be installed on the bridge arms to collect the actual current values ​​of each bridge arm.

[0074] Calculate the second harmonic component of phase A based on the actual current values ​​of the first upper bridge arm, the first lower bridge arm, the second upper bridge arm, and the second lower bridge arm.

[0075] like Figure 3 As shown, phase shifting of the second harmonic component of phase A yields the second harmonic components of phase B and phase C.

[0076] Optionally, in a modular level converter, each bridge arm may include an upper bridge arm and a lower bridge arm. The bridge arm current of the upper and lower bridge arms includes a DC component, an AC component, and a second harmonic component. The only difference is that the AC component of the upper bridge arm is opposite to that of the lower bridge arm. Therefore, the second harmonic component of phase A satisfies: .

[0077] in, This represents the second harmonic component of phase A. This represents the actual current value of the first upper bridge arm. This indicates the actual current value of the first lower bridge arm. This indicates the actual current value of the second upper bridge arm. This represents the actual current value of the second lower bridge arm. It can be seen that the actual current values ​​of each bridge arm can eliminate the AC component, thus retaining only the second harmonic component.

[0078] Phase shifting of the second harmonic component of phase A (can be 120°) yields the second harmonic component of phase B. Phase shifting of the second harmonic component of phase A (which can be 240°) yields the second harmonic component of phase C. .

[0079] In some other possible implementations, step S2 above, calculating the first modulation voltage of the converter based on the second harmonic current component, includes: like Figure 3 As shown, the second harmonic components of phase A, phase B, and phase C are subjected to Parker transformation (i.e., abc / dq transformation) to obtain the first current component of the converter along the d-axis in the dq coordinate system. and the first current component along the q-axis .

[0080] The first current component along the d-axis and the first current component along the q-axis Filter the current (using a low-pass filter) to obtain the second current component along the d-axis. and the second current component along the q-axis .

[0081] like Figure 3 As shown, the second current component along the d-axis and the second current component along the q-axis By performing proportional-integral (PI) control and decoupling control, the second modulation voltage of the converter along the d-axis in the dq coordinate system is obtained. and q-axis second modulation voltage .

[0082] The second modulation voltage of the d-axis and q-axis second modulation voltage Amplitude limiting control is performed to obtain the first modulation voltage of the converter along the d-axis in the dq coordinate system. and q-axis first modulation voltage .

[0083] Optionally, the second modulation voltage along the d-axis and the second modulation voltage along the q-axis satisfy:

[0084]

[0085] in, This represents the second modulation voltage along the d-axis. This represents the second modulation voltage along the q-axis. This represents the second current component along the d-axis. This represents the second current component along the q-axis. This represents the reference value for the d-axis current component (which can be set to 0). This represents the reference value for the q-axis current component (which can be 0). This represents the first proportionality coefficient. This represents the first integral coefficient. This represents the second proportionality coefficient. Let denote the second integral coefficient. s denotes the Laplace operator. This indicates the inductance value of the bridge arm inductance. This indicates the inductance value of the adjustable inductor in the load branch of the converter. This represents the angular frequency of the AC power grid.

[0086] For example, the second modulation voltage along the d-axis and the second modulation voltage along the q-axis satisfy: .

[0087] in, This represents the second modulation voltage along the d-axis. This represents the second modulation voltage along the q-axis. Indicates the modulation ratio of the converter. This represents the DC voltage of the converter.

[0088] In some other possible implementations, step S3 above, which involves suppressing the second harmonic current component based on the first modulation voltage of the converter, includes: The first modulation voltage of the converter is subjected to an inverse Park transform (i.e., dq / abc transform) to obtain the first second harmonic compensation voltage of the converter in the abc coordinate system.

[0089] The second harmonic compensation voltage of the converter is calculated based on the first harmonic compensation voltage. The second harmonic compensation voltage satisfies: .in, This represents the second harmonic compensation voltage. This represents the first and second harmonic compensation voltage.

[0090] The fundamental voltage of the first phase in the converter is added to the second harmonic compensation voltage to obtain the modulation voltage of the first phase.

[0091] The modulation voltage of the second phase is obtained by subtracting the fundamental voltage of the second phase from the second harmonic compensation voltage.

[0092] The first phase submodule is controlled based on the modulation voltage of the first phase, and the second phase submodule is controlled based on the modulation voltage of the second phase.

[0093] Example 2: Based on the same inventive concept, embodiments of this application also provide a device for suppressing second harmonic current components. For example... Figure 4 As shown, the suppression device 400 may include: Extraction module 401 is used to extract the second harmonic current component from the actual current value of each bridge arm of the converter.

[0094] The calculation module 402 is used to calculate the first modulation voltage of the converter based on the second harmonic current component.

[0095] Suppression module 403 is used to suppress the second harmonic current component based on the first modulation voltage of the converter.

[0096] In some possible implementations, the extraction module 401 is specifically used for: Obtain the actual current values ​​of the first upper bridge arm, the first lower bridge arm, the second upper bridge arm, and the second lower bridge arm in the converter.

[0097] Calculate the second harmonic component of phase A based on the actual current values ​​of the first upper bridge arm, the first lower bridge arm, the second upper bridge arm, and the second lower bridge arm.

[0098] like Figure 3 As shown, phase shifting of the second harmonic component of phase A yields the second harmonic components of phase B and phase C.

[0099] The second harmonic component of phase A satisfies: .

[0100] in, This represents the second harmonic component of phase A. This represents the actual current value of the first upper bridge arm. This indicates the actual current value of the first lower bridge arm. This indicates the actual current value of the second upper bridge arm. This indicates the actual current value of the second lower bridge arm.

[0101] Phase shifting of the second harmonic component of phase A (can be 120°) yields the second harmonic component of phase B. Phase shifting of the second harmonic component of phase A (which can be 240°) yields the second harmonic component of phase C. .

[0102] In some other possible implementations, the computing module 402 is used for: like Figure 3 As shown, the second harmonic components of phase A, phase B, and phase C are subjected to Parker transformation (i.e., abc / dq transformation) to obtain the first current component of the converter along the d-axis in the dq coordinate system. and the first current component along the q-axis .

[0103] The first current component along the d-axis and the first current component along the q-axis Filter the current (using a low-pass filter) to obtain the second current component along the d-axis. and the second current component along the q-axis .

[0104] like Figure 3 As shown, the second current component along the d-axis and the second current component along the q-axis By performing proportional-integral (PI) control and decoupling control, the second modulation voltage of the converter along the d-axis in the dq coordinate system is obtained. and q-axis second modulation voltage .

[0105] The second modulation voltage of the d-axis and q-axis second modulation voltage Amplitude limiting control is performed to obtain the first modulation voltage of the converter along the d-axis in the dq coordinate system. and q-axis first modulation voltage .

[0106] Optionally, the second modulation voltage along the d-axis and the second modulation voltage along the q-axis satisfy:

[0107]

[0108] in, This represents the second modulation voltage along the d-axis. This represents the second modulation voltage along the q-axis. This represents the second current component along the d-axis. This represents the second current component along the q-axis. This represents the reference value for the d-axis current component (which can be set to 0). This represents the reference value for the q-axis current component (which can be 0). This represents the first proportionality coefficient. This represents the first integral coefficient. This represents the second proportionality coefficient. Let denote the second integral coefficient. s denotes the Laplace operator. This indicates the inductance value of the bridge arm inductance. This indicates the inductance value of the adjustable inductor in the load branch of the converter. This represents the angular frequency of the AC power grid.

[0109] For example, the second modulation voltage along the d-axis and the second modulation voltage along the q-axis satisfy: .

[0110] in, This represents the second modulation voltage along the d-axis. This represents the second modulation voltage along the q-axis. Indicates the modulation ratio of the converter. This represents the DC voltage of the converter.

[0111] In some other possible implementations, the suppression module 403 is specifically used for: The first modulation voltage of the converter is subjected to an inverse Park transform (i.e., dq / abc transform) to obtain the first second harmonic compensation voltage of the converter in the abc coordinate system.

[0112] The second harmonic compensation voltage of the converter is calculated based on the first harmonic compensation voltage. The second harmonic compensation voltage satisfies: .in, This represents the second harmonic compensation voltage. This represents the first and second harmonic compensation voltage.

[0113] The fundamental voltage of the first phase in the converter is added to the second harmonic compensation voltage to obtain the modulation voltage of the first phase.

[0114] The modulation voltage of the second phase is obtained by subtracting the fundamental voltage of the second phase from the second harmonic compensation voltage.

[0115] The first phase submodule is controlled based on the modulation voltage of the first phase, and the second phase submodule is controlled based on the modulation voltage of the second phase.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] 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.

[0120] 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.

[0121] 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.

[0122] 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 second harmonic current components, characterized in that, include: Extract the second harmonic current component from the actual current value of each bridge arm of the converter; The first modulation voltage of the converter is calculated based on the second harmonic current component; The second harmonic current component is suppressed according to the first modulation voltage of the converter; The extraction of the second harmonic current component from the actual current values ​​of each bridge arm of the converter includes: Obtain the actual current values ​​of the first upper bridge arm, the first lower bridge arm, the second upper bridge arm, and the second lower bridge arm in the converter; Calculate the second harmonic component of phase A based on the actual current values ​​of the first upper bridge arm, the first lower bridge arm, the second upper bridge arm, and the second lower bridge arm; Phase shifting of the second harmonic component of phase A yields the second harmonic component of phase B and the second harmonic component of phase C; The step of calculating the first modulation voltage of the converter based on the second harmonic current component includes: The second harmonic component of phase A, the second harmonic component of phase B, and the second harmonic component of phase C are subjected to Parker transformation to obtain the first current component of the d-axis and the first current component of the q-axis of the converter in the dq coordinate system. The first current component of the d-axis and the first current component of the q-axis are filtered to obtain the second current component of the d-axis and the second current component of the q-axis. By performing proportional-integral control and decoupling control on the d-axis second current component and the q-axis second current component, the d-axis second modulation voltage and the q-axis second modulation voltage of the converter in the dq coordinate system are obtained. By performing amplitude limiting control on the second modulation voltage of the d-axis and the second modulation voltage of the q-axis, the first modulation voltage of the converter on the d-axis and the first modulation voltage of the q-axis in the dq coordinate system are obtained; The second harmonic component of phase A satisfies: ; in, This represents the second harmonic component of phase A. This indicates the actual current value of the first upper bridge arm. This indicates the actual current value of the first lower bridge arm. This indicates the actual current value of the second upper bridge arm. This indicates the actual current value of the second lower bridge arm.

2. The suppression method according to claim 1, characterized in that, The step of suppressing the second harmonic current component based on the first modulation voltage of the converter includes: Perform an inverse Park transform on the first modulation voltage of the converter to obtain the first second harmonic compensation voltage of the converter in the abc coordinate system; The second second harmonic compensation voltage of the converter is calculated based on the first second harmonic compensation voltage. The fundamental voltage of the first phase in the converter is added to the second second harmonic compensation voltage to obtain the modulation voltage of the first phase; The modulation voltage of the second phase is obtained by subtracting the fundamental voltage of the second phase in the converter from the second second harmonic compensation voltage. The submodule of the first phase is controlled according to the modulation voltage of the first phase, and the submodule of the second phase is controlled according to the modulation voltage of the second phase.

3. The suppression method according to claim 2, characterized in that, The second frequency harmonic compensation voltage satisfies: ;in, This represents the second harmonic compensation voltage. This represents the first and second harmonic compensation voltage.

4. The suppression method according to claim 1, characterized in that, The second modulation voltage along the d-axis and the second modulation voltage along the q-axis satisfy the following: ; in, This represents the second modulation voltage along the d-axis. This represents the second modulation voltage along the q-axis. This indicates the modulation ratio of the converter. This represents the DC voltage of the converter.

5. The suppression method according to claim 1, characterized in that, The second modulation voltage along the d-axis and the second modulation voltage along the q-axis satisfy the following: in, This represents the second modulation voltage along the d-axis. This represents the second modulation voltage along the q-axis; This represents the second current component along the d-axis. This represents the second current component along the q-axis; This represents the reference value for the d-axis current component. Indicates the reference value of the q-axis current component; This represents the first proportionality coefficient. Indicates the first integral coefficient; This represents the second proportionality coefficient. The second integral coefficient is represented by s; s represents the Laplace operator. This indicates the inductance value of the bridge arm inductance. This represents the inductance value of the adjustable inductor in the load branch of the converter. This represents the angular frequency of the AC power grid.

6. A device for suppressing second harmonic current components, characterized in that, include: The extraction module is used to extract the second harmonic current component from the actual current value of each arm of the converter. The calculation module is used to calculate the first modulation voltage of the converter based on the second harmonic current component; Suppression module, used to suppress the second harmonic current component according to the first modulation voltage of the converter; The extraction module is specifically used for: Obtain the actual current values ​​of the first upper bridge arm, the first lower bridge arm, the second upper bridge arm, and the second lower bridge arm in the converter; Calculate the second harmonic component of phase A based on the actual current values ​​of the first upper bridge arm, the first lower bridge arm, the second upper bridge arm, and the second lower bridge arm; Phase shifting of the second harmonic component of phase A yields the second harmonic component of phase B and the second harmonic component of phase C; The calculation module is used for: The second harmonic component of phase A, the second harmonic component of phase B, and the second harmonic component of phase C are subjected to Parker transformation to obtain the first current component of the d-axis and the first current component of the q-axis of the converter in the dq coordinate system. The first current component of the d-axis and the first current component of the q-axis are filtered to obtain the second current component of the d-axis and the second current component of the q-axis. By performing proportional-integral control and decoupling control on the d-axis second current component and the q-axis second current component, the d-axis second modulation voltage and the q-axis second modulation voltage of the converter in the dq coordinate system are obtained. By performing amplitude limiting control on the second modulation voltage of the d-axis and the second modulation voltage of the q-axis, the first modulation voltage of the converter on the d-axis and the first modulation voltage of the q-axis in the dq coordinate system are obtained; The second harmonic component of phase A satisfies: ; in, This represents the second harmonic component of phase A. This indicates the actual current value of the first upper bridge arm. This indicates the actual current value of the first lower bridge arm. This indicates the actual current value of the second upper bridge arm. This indicates the actual current value of the second lower bridge arm.

7. The suppression device according to claim 6, characterized in that, The suppression module is specifically used for: Perform an inverse Park transform on the first modulation voltage of the converter to obtain the first second harmonic compensation voltage of the converter in the abc coordinate system; The second second harmonic compensation voltage of the converter is calculated based on the first second harmonic compensation voltage. The fundamental voltage of the first phase in the converter is added to the second second harmonic compensation voltage to obtain the modulation voltage of the first phase; The modulation voltage of the second phase is obtained by subtracting the fundamental voltage of the second phase in the converter from the second second harmonic compensation voltage. The submodule of the first phase is controlled according to the modulation voltage of the first phase, and the submodule of the second phase is controlled according to the modulation voltage of the second phase.

8. The suppression device according to claim 7, characterized in that, The second frequency harmonic compensation voltage satisfies: ;in, This represents the second harmonic compensation voltage. This represents the first and second harmonic compensation voltage.

9. The suppression device according to claim 6, characterized in that, The second modulation voltage along the d-axis and the second modulation voltage along the q-axis satisfy the following: ; in, This represents the second modulation voltage along the d-axis. This represents the second modulation voltage along the q-axis. This indicates the modulation ratio of the converter. This represents the DC voltage of the converter.

10. The suppression device according to claim 6, characterized in that, The second modulation voltage along the d-axis and the second modulation voltage along the q-axis satisfy the following: in, This represents the second modulation voltage along the d-axis. This represents the second modulation voltage along the q-axis; This represents the second current component along the d-axis. This represents the second current component along the q-axis; This represents the reference value for the d-axis current component. Indicates the reference value of the q-axis current component; This represents the first proportionality coefficient. Indicates the first integral coefficient; This represents the second proportionality coefficient. The second integral coefficient is represented by s; s represents the Laplace operator. This indicates the inductance value of the bridge arm inductance. This represents the inductance value of the adjustable inductor in the load branch of the converter. This represents the angular frequency of the AC power grid.

11. 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 5 is implemented.

12. 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 5.

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