Control method and control device of voltage source type converter

Abstract

The invention provides a control method and a control device of a voltage source type converter. According to the alternating current port current of the VSC and the first alternating current side flux linkage, the alternating current port flux linkage of the VSC can be obtained, and then control over the VSC is achieved, namely control over the alternating current port voltage of the VSC is achieved. The flux linkage of the alternating current port is uniquely determined, so that the voltage of the alternating current port is uniquely determined, the flux linkage of the alternating current port is not influenced by the initial value of the flux linkage, asymmetry or overcurrent of the current of the alternating current port of the VSC is avoided, the VSC is not unstable in the transient fault process, and the operation reliability of the VSC is improved. Differential protection of the transformer can be realized, namely, the transformer can be prevented from entering deep magnetic saturation. The first alternating current side current and the second alternating current side current can be measured only through measurement equipment such as a sensor, calculation of the alternating current port flux linkage is achieved, and the hardware cost of the VSC cannot be remarkably increased due to the fact that the measurement equipment is additionally arranged.

Description

Technical Field

[0001] The present application relates to the field of power systems, and in particular to a control method and a control device for a voltage source converter. Background Art

[0002] With the rapid development of new energy technology, new energy power stations represented by photovoltaic power generation have been widely used. New energy power stations can generally be connected to the AC power grid through voltage source converters (VSC).

[0003] In order to control the VSC, the relevant technology generally adopts the voltage-frequency control method. Since the AC port flux Ψ(t) of the VSC at time t satisfies Where Ψ0 is the initial value of flux linkage at time zero, u is the AC port voltage of VSC, and t represents the time. Since Ψ(t) will be affected by Ψ0, and Ψ0 is not 0 during the transient fault of VSC, the AC port current of VSC will be asymmetric or overcurrent. VSC consumes asymmetric current or overcurrent through the resistance of the filter unit, which makes the dynamic response time of VSC long and easily causes VSC to become unstable during transient fault. Summary of the invention

[0004] In order to solve the problem of VSC instability during transient faults in the prior art, the present application provides a control method for a voltage source converter, which may include:

[0005] The AC port current of the voltage source converter, the first AC side current and the second AC side current of the transformer connected to the voltage source converter are collected.

[0006] The first AC side flux of the transformer is calculated according to the first AC side current and the second AC side current, and the AC port flux of the voltage source converter is calculated according to the AC port current and the first AC side flux.

[0007] The voltage source converter is controlled according to the AC port flux.

[0008] In some possible implementations, calculating the first AC side flux of the transformer according to the first AC side current and the second AC side current includes:

[0009] The first AC side flux is calculated according to the first AC side current, the second AC side current and the mutual inductance matrix of the transformer in combination with a multiplication operation.

[0010] Optionally, the first AC side flux satisfies:

[0011]

[0012] Where Ψ1 represents the first AC side flux, Ψ2 represents the second AC side flux of the transformer, and L tf represents the mutual inductance matrix of the transformer, i abc1 represents the first AC side current, i abc2 Indicates the second AC side current.

[0013] Exemplarily, the AC port flux satisfies:

[0014] Ψ3=L·i abc +Ψ1

[0015] Where, Ψ3 represents the AC port flux, L represents the inductance of the filter inductor connected to the voltage source converter, i abc represents the AC port current, and Ψ1 represents the first AC side flux.

[0016] In some other possible implementations, the voltage source converter is controlled according to the AC port flux, including:

[0017] The difference between the AC port flux and a preset reference flux is differentially controlled to obtain a control voltage.

[0018] The control voltage is modulated to obtain a driving signal.

[0019] The power tube in the voltage source converter is driven according to the driving signal.

[0020] On the other hand, the present application also provides a control device for a voltage source converter, which may include

[0021] The acquisition module is used to acquire the AC port current of the voltage source converter, the first AC side current and the second AC side current of the transformer connected to the voltage source converter.

[0022] The calculation module is used to calculate the first AC side flux of the transformer according to the first AC side current and the second AC side current, and calculate the AC port flux of the voltage source converter according to the AC port current and the first AC side flux.

[0023] The control module is used to control the voltage source converter according to the AC port flux.

[0024] In some possible implementations, the computing module is specifically used to:

[0025] The first AC side flux is calculated according to the first AC side current, the second AC side current and the mutual inductance matrix of the transformer in combination with a multiplication operation.

[0026] Optionally, the calculation module calculates the first AC side flux according to the following formula:

[0027]

[0028] Where Ψ1 represents the first AC side flux, Ψ2 represents the second AC side flux of the transformer, and L tf represents the mutual inductance matrix of the transformer, i abc1 represents the first AC side current, i abc2 Indicates the second AC side current.

[0029] Exemplarily, the calculation module calculates the AC port flux according to the following formula:

[0030] Ψ3=L·i abc +Ψ1

[0031] Where, Ψ3 represents the AC port flux, L represents the inductance of the filter inductor connected to the voltage source converter, i abc represents the AC port current, and Ψ1 represents the first AC side flux.

[0032] In some other possible implementations, the control module is specifically used to:

[0033] The difference between the AC port flux and a preset reference flux is differentially controlled to obtain a control voltage.

[0034] The control voltage is modulated to obtain a driving signal.

[0035] The power tube in the voltage source converter is driven according to the driving signal.

[0036] In another aspect, the present application further provides a computing device, comprising: one or more processors;

[0037] a processor for executing one or more programs;

[0038] When the one or more programs are executed by the one or more processors, the control method described above is implemented.

[0039] On the other hand, the present application also provides a computer-readable storage medium having a computer program stored thereon, and when the computer program is executed, the control method as described above is implemented.

[0040] Compared with the prior art, the beneficial effects of this application are:

[0041] The control method of the voltage source converter provided in the present application calculates the first AC side flux of the transformer according to the first AC side current and the second AC side current, and the AC port flux of the VSC can be obtained according to the AC port current of the VSC and the first AC side flux, and the control of the VSC can be achieved through the AC port flux, that is, the control of the AC port voltage of the VSC is achieved. Since the AC port flux is uniquely determined, the AC port voltage is also uniquely determined, so that the AC port flux will not be affected by the initial value of the flux, avoiding the asymmetry or overcurrent of the AC port current of the VSC, and thus the VSC will not be unstable during a transient fault, that is, the operating reliability of the VSC is improved.

[0042] The present application realizes the calculation of the AC port flux linkage of the VSC through the first AC side current and the second AC side current of the transformer, thereby realizing the differential protection of the transformer, that is, preventing the transformer from entering deep magnetic saturation. It can be seen that the calculation of the AC port flux linkage can be finally realized only by measuring the first AC side current and the second AC side current through sensors, etc., and the hardware cost of the VSC will not be significantly increased due to the addition of measuring equipment such as sensors. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 A schematic topological diagram of a VSC connected to an AC power grid through a filter unit and a transformer in an embodiment of the present application;

[0044] Figure 2 A schematic flow chart of a control method in an embodiment of the present application;

[0045] Figure 3 Another schematic flow chart of the control method in the embodiment of the present application;

[0046] Figure 4 This is a schematic structural diagram of a control device in an embodiment of the present application. DETAILED DESCRIPTION

[0047] The technical solution in this application will be described below in conjunction with the accompanying drawings.

[0048] The terms "first", "second", etc. in the specification embodiments, claims, and drawings of the present application are only used for the purpose of distinguishing descriptions, and cannot be understood as indicating or implying relative importance, nor can they be understood as indicating or implying order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, including a series of steps or units. The method, system, product, or device is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products, or devices.

[0049] It should be understood that in the present application, "at least one (item)" means one or more, and "plurality" means two or more. "And / or" is used to describe the association relationship of associated objects, indicating that three relationships may exist. For example, "A and / or B" can mean: only A exists, only B exists, and A and B exist at the same time, where A and B can be singular or plural. The character " / " generally indicates that the objects associated before and after are in an "or" relationship. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, at least one of a, b or c can mean: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, c can be single or multiple.

[0050] like Figure 1 As shown, the voltage source converter (VSC) can be connected to the AC grid S through the filter unit LC and the transformer T1. The filter unit LC may include a filter inductor L and a filter capacitor C. The first end of the filter inductor L is connected to the AC port of the VSC through node ③. Therefore, the AC port current i abc The second end of the filter inductor L is connected to the first end of the filter capacitor C, and is connected to the first AC side of the transformer T1 through node ①. The second end of the filter capacitor C is connected to the ground terminal, and the second AC side of the transformer T1 can be connected to the grid S. The first AC side current i of the transformer T1 is abc1 That is, the current at node ①, the second AC side current i of transformer T1 abc2 This is the current at node ②.

[0051] VSC includes power transistors such as insulated gate bipolar transistors (IGBTs). Figure 1 , the power tube can be driven by the driving signal DS, that is, the control of the VSC can be realized.

[0052] The present application proposes a control method for a voltage source converter, such as Figure 2 The control method 100 may include the following steps:

[0053] Step S1: Collect the AC port current i of the VSC abc , the first AC side current i of the transformer T1 connected to the VSC abc1 and the second AC side current i abc2 .

[0054] Step S2: According to the first AC side current i abc1 and the second AC side current i abc2 Calculate the first AC side flux Ψ1 of transformer T1 and calculate the AC port current i abc The AC port flux Ψ3 of the VSC is calculated using the first AC side flux Ψ1.

[0055] Step S3: Control the VSC according to the AC port flux Ψ3.

[0056] In some possible implementations, in the above step S2, according to the first AC side current i abc1 and the second AC side current i abc2 Calculate the first AC side flux Ψ1 of the transformer T1, which can be specifically calculated based on the first AC side current i abc1 , the second AC side current i abc2 and the mutual inductance matrix L of transformer T1 tf , and combined with the multiplication operation to calculate the first AC side flux Ψ1, such as Figure 3 shown.

[0057] Optionally, the first AC side flux Ψ1 satisfies:

[0058]

[0059] Where Ψ1 represents the first AC side flux, Ψ2 represents the second AC side flux of transformer T1, L tf represents the mutual inductance matrix of the transformer, i abc1 represents the first AC side current, i abc2 Indicates the second AC side current.

[0060] Exemplarily, the AC port flux Ψ3 satisfies:

[0061] Ψ3=L·i abc +Ψ1

[0062] Where Ψ3 represents the AC port flux. abc represents the AC port current. Ψ1 represents the first AC side flux. L represents the inductance of the filter inductor L connected to the VSC. L can be a 6-row 6-column mutual inductance matrix, whose parameters are determined by the structure of the transformer T1 and can be obtained by using finite element analysis and other software according to the structural design of the transformer T1.

[0063] In some other possible implementations, in the above step S3, controlling the VSC according to the AC port flux Ψ3 includes:

[0064] like Figure 3 As shown, the AC port flux Ψ3 and the preset reference flux (with Ψ 3ref The difference between Figure 3 T represents the modulation period of pulse width modulation, which is equal to the period of the triangle wave in pulse width modulation), and the control voltage is obtained (which can be expressed as u abcref For control voltage u abcref Modulate (such as pulse width modulation, etc.) to obtain Figure 1 The drive signal DS in the VSC is used to drive the IGBT and other power tubes in the VSC.

[0065] Optional, preset reference flux Ψ 3ref It can be a three-phase alternating sinusoidal flux. 3ref satisfy:

[0066]

[0067] Ψ a_ref represents the reference flux of phase A, Ψ b_ref represents the reference flux of phase B, Ψ c_ref Represents the reference flux of phase C. θ represents the phase angle of the reference flux of phase A, satisfying θ=ωt+θ0, ω represents the angular velocity, and θ0 represents the initial phase angle. Ψ f Indicates the rated flux of the synchronous motor.

[0068] Embodiment 2:

[0069] Based on the same inventive concept, the present invention also provides a control device for a voltage source converter, such as Figure 4 The control device 200 includes:

[0070] The acquisition module 21 is used to acquire the AC port current i of the VSC. abc , the first AC side current i of the transformer T1 connected to the VSC abc1 and the second AC side current i abc2 .

[0071] The calculation module 22 is used to calculate the current i abc1 and the second AC side current i abc2 Calculate the first AC side flux Ψ1 of transformer T1 and calculate the AC port current i abc The AC port flux Ψ3 of the VSC is calculated using the first AC side flux Ψ1.

[0072] The control module 23 is used to control the VSC according to the AC port flux Ψ3.

[0073] In some possible implementations, the calculation module 22 is specifically configured to:

[0074] According to the first AC side current i abc1 , the second AC side current i abc2and the mutual inductance matrix L of transformer T1 tf , and combined with the multiplication operation to calculate the first AC side flux Ψ1, such as Figure 3 shown.

[0075] Optionally, the calculation module 22 calculates the first AC side flux according to the following formula:

[0076]

[0077] Where Ψ1 represents the first AC side flux, Ψ2 represents the second AC side flux of the transformer, and L tf represents the mutual inductance matrix of the transformer, i abc1 represents the first AC side current, i abc2 Indicates the second AC side current.

[0078] Exemplarily, the calculation module 22 calculates the AC port flux according to the following formula:

[0079] Ψ3=L·i abc +Ψ1

[0080] Wherein, Ψ3 represents the flux linkage of the AC port. L represents the inductance of the filter inductor connected to the voltage source converter. L can be a 6-row 6-column mutual inductance matrix, whose parameters are determined by the structure of the transformer T1 and can be obtained by using finite element analysis software according to the structural design of the transformer T1. abc represents the AC port current, and Ψ1 represents the first AC side flux.

[0081] In some other possible implementations, the control module 23 is specifically used to:

[0082] like Figure 3 As shown, the AC port flux Ψ3 and the preset reference flux (with Ψ 3ref The difference between Figure 3 Where T represents the modulation period of pulse width modulation), the control voltage is obtained (which can be abcref For control voltage u abcref Modulate (such as pulse width modulation, etc.) to obtain Figure 1 The drive signal DS in the VSC is used to drive the IGBT and other power tubes in the VSC.

[0083] Optional, preset reference flux Ψ 3ref It can be a three-phase alternating sinusoidal flux. 3ref satisfy:

[0084]

[0085] Ψ a_ref represents the reference flux of phase A, Ψ b_refrepresents the reference flux of phase B, Ψ c_ref represents the reference flux of phase C. θ represents the phase angle of the reference flux of phase A, satisfying θ=ωt+θ0, ω represents the angular velocity, and θ0 represents the initial phase angle.

[0086] Embodiment 3:

[0087] Based on the same inventive concept, the present invention also provides a computer device, which includes a processor and a memory, wherein the memory is used to store a computer program, the computer program includes program instructions, and the processor is used to execute 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 (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, which is suitable for implementing one or more instructions, and is specifically suitable for loading and executing one or more instructions in the computer storage medium to implement the corresponding method flow or corresponding functions, so as to implement the steps of the control method provided in the above embodiment.

[0088] Embodiment 4:

[0089] Based on the same inventive concept, the present invention also provides a storage medium, specifically a computer-readable storage medium (Memory), which is a memory device in a computer device for storing programs and data. It is understandable that the computer-readable storage medium here can include both built-in storage media in a computer device and, of course, an extended storage medium supported by the computer device. The computer-readable storage medium provides a storage space, which stores the operating system of the terminal. In addition, one or more instructions suitable for being loaded and executed by a processor are also stored in the storage space, and these instructions can be one or more computer programs (including program codes). It should be noted that the computer-readable storage medium here can be a high-speed RAM memory or a non-volatile memory, such as at least one disk memory. The processor can load and execute one or more instructions stored in the computer-readable storage medium to implement the steps of the control method provided in the above embodiment.

[0090] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0091] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0092] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0093] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0094] The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are included in the scope of the claims of the present invention to be approved.

Claims

1. A control method for a voltage source converter, characterized in that: include: Collecting an AC port current of a voltage source converter, a first AC side current and a second AC side current of a transformer connected to the voltage source converter; Calculate the first AC side flux of the transformer according to the first AC side current and the second AC side current, and calculate the AC port flux of the voltage source converter according to the AC port current and the first AC side flux; The voltage source converter is controlled according to the AC port flux.

2. The control method according to claim 1, characterized in that: The calculating the first AC side flux of the transformer according to the first AC side current and the second AC side current comprises: The first AC side flux is calculated according to the first AC side current, the second AC side current and the mutual inductance matrix of the transformer in combination with a multiplication operation.

3. The control method according to claim 1, characterized in that: The first AC side flux satisfies: Wherein, Ψ1 represents the first AC side flux, Ψ2 represents the second AC side flux of the transformer, L tf represents the mutual inductance matrix of the transformer, i abc1 represents the first AC side current, i abc2 represents the second AC side current.

4. The control method according to claim 1, characterized in that: The AC port flux satisfies: Ψ3=L i abc +Ψ1 Wherein, Ψ3 represents the flux linkage of the AC port, L represents the inductance of the filter inductor connected to the voltage source converter, i abc represents the AC port current, and Ψ1 represents the first AC side flux.

5. The control method according to claim 1, characterized in that: The controlling the voltage source converter according to the AC port flux linkage comprises: Performing differential control on the difference between the AC port flux and a preset reference flux to obtain a control voltage; Modulating the control voltage to obtain a driving signal; The power tube in the voltage source converter is driven according to the driving signal.

6. A control device for a voltage source converter, characterized in that: include: A collection module, used for collecting the AC port current of the voltage source converter, the first AC side current and the second AC side current of the transformer connected to the voltage source converter; a calculation module, configured to calculate a first AC side flux of the transformer according to the first AC side current and the second AC side current, and calculate an AC port flux of the voltage source converter according to the AC port current and the first AC side flux; A control module is used to control the voltage source converter according to the AC port flux.

7. The control device according to claim 6, characterized in that: The calculation module is used for: The first AC side flux is calculated according to the first AC side current, the second AC side current and the mutual inductance matrix of the transformer in combination with a multiplication operation.

8. The control device according to claim 6, characterized in that: The calculation module specifically calculates the first AC side flux according to the following formula: Wherein, Ψ1 represents the first AC side flux, Ψ2 represents the second AC side flux of the transformer, L tf represents the mutual inductance matrix of the transformer, i abc1 represents the first AC side current, i abc2 represents the second AC side current.

9. The control device according to claim 6, characterized in that: The calculation module specifically calculates the AC port flux according to the following formula: Ψ3=L i abc +Ψ1 Wherein, Ψ3 represents the flux linkage of the AC port, L represents the inductance of the filter inductor connected to the voltage source converter, i abc represents the AC port current, and Ψ1 represents the first AC side flux.

10. The control device according to claim 6, characterized in that: The control module is specifically used for: Performing differential control on the difference between the AC port flux and a preset reference flux to obtain a control voltage; Modulating the control voltage to obtain a driving signal; The power tube in the voltage source converter is driven according to the driving signal.

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 control method according to any one of claims 1 to 5 is implemented.

12. A computer-readable storage medium, characterized in that: A computer program is stored thereon, and when the computer program is executed, the control method according to any one of claims 1 to 5 is implemented.

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