Bipolar converter cascade control method and device and electronic equipment

Abstract

The invention provides a bipolar converter cascade control method and device and electronic equipment, and the method comprises the steps: determining a first control signal based on a first DC voltage and a corresponding reference voltage of a receiving-end converter, a first reactive power and a corresponding first reference power, and controlling the receiving-end converter through employing the first control signal; determining a second control signal based on the active power and the corresponding active reference value of the first transmitting-end converter, the second reactive power and the corresponding second reference power, and controlling the first transmitting-end converter by using the second control signal; and determining a third control signal based on the second DC voltage of the second transmitting-end converter, the first DC voltage of the first transmitting-end converter, a third reactive power and a corresponding third reference power, and controlling the second transmitting-end converter by using the third control signal. Therefore, the stability of the grid-connected system is improved.

Description

Technical Field

[0001] The present disclosure relates to the technical field of wind power grid-connected systems, and in particular to a bipolar converter cascade control method, device and electronic equipment. Background Art

[0002] As the scale of clean energy power plants expands, the number of sending-end converter stations in the flexible DC transmission grid-connected system also increases. In related technologies, multi-end converters are usually cascaded in series or parallel. Among them, if the grid-connected system is connected to multiple clean energy power generation (for example, wind farms and photovoltaic farms) at the same time, and the converters at the sending end of the wind farm and photovoltaic farm are connected in series, the DC current flowing through each converter is equal. Since the power generation of the wind farm and the photovoltaic farm may be different, it will cause the voltage at both ends of the converter to be mismatched, which may cause the grid-connected system to become unstable. Summary of the invention

[0003] The present disclosure proposes a bipolar converter cascade control method, device and electronic equipment, aiming to solve one of the technical problems in the related art at least to a certain extent.

[0004] The first aspect of the present disclosure discloses a method for cascading control of a bipolar converter, wherein the grid-connected system comprises a first sending-end converter connected to a wind farm, a second sending-end converter connected to a photovoltaic farm, and a receiving-end converter, wherein the first sending-end converter and the second sending-end converter are connected in series, and the method comprises: determining a first control signal based on a first DC voltage and a corresponding reference voltage, a first reactive power and a corresponding first reference power of the receiving-end converter, and controlling the receiving-end converter using the first control signal; determining a second control signal based on an active power and a corresponding active reference value, a second reactive power and a corresponding second reference power of the first sending-end converter, and controlling the first sending-end converter using the second control signal; and determining a third control signal based on a second DC voltage of the second sending-end converter and a first DC voltage, a third reactive power and a corresponding third reference power of the first sending-end converter, and controlling the second sending-end converter using the third control signal.

[0005] The second aspect of the present disclosure proposes a bipolar converter cascade control device, wherein the grid-connected system includes a first sending-end converter connected to a wind farm, a second sending-end converter connected to a photovoltaic field, and a receiving-end converter, wherein the first sending-end converter and the second sending-end converter are connected in series, and the device includes: a first control module, used to determine a first control signal based on a first DC voltage and a corresponding reference voltage, a first reactive power and a corresponding first reference power of the receiving-end converter, and use the first control signal to control the receiving-end converter; a second control module, used to determine a second control signal based on an active power and a corresponding active reference value, a second reactive power and a corresponding second reference power of the first sending-end converter, and use the second control signal to control the first sending-end converter; and a third control module, used to determine a third control signal based on the second DC voltage of the second sending-end converter and the first DC voltage, a third reactive power and a corresponding third reference power of the first sending-end converter, and use the third control signal to control the second sending-end converter.

[0006] An embodiment of the third aspect of the present disclosure proposes an electronic device, comprising: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the bipolar converter cascade control method of the embodiment of the present disclosure.

[0007] The fourth aspect of the present disclosure provides a non-transitory computer-readable storage medium storing computer instructions, wherein the computer instructions are used to enable the computer to execute the bipolar converter cascade control method disclosed in the embodiment of the present disclosure.

[0008] In this embodiment, a first control signal is determined based on the first DC voltage and the corresponding reference voltage, the first reactive power and the corresponding first reference power of the receiving-end converter, and the first control signal is used to control the receiving-end converter; a second control signal is determined based on the active power and the corresponding active reference value, the second reactive power and the corresponding second reference power of the first sending-end converter, and the second control signal is used to control the first sending-end converter; and a third control signal is determined based on the second DC voltage of the second sending-end converter and the first DC voltage, the third reactive power and the corresponding third reference power of the first sending-end converter, and the third control signal is used to control the second sending-end converter. This allows the receiving-end converter to be controlled with a fixed DC voltage to ensure that the DC terminal voltages of the series converters are equal, thereby improving the stability of the grid-connected system.

[0009] Additional aspects and advantages of the present disclosure will be given in part in the following description and in part will be obvious from the following description or learned through practice of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The above and / or additional aspects and advantages of the present disclosure will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0011] Figure 1 is a flow chart of a bipolar converter cascade control method provided according to an embodiment of the present disclosure;

[0012] Figure 2 is a schematic diagram of the structure of a grid-connected system provided according to an embodiment of the present disclosure;

[0013] Figure 3 is a schematic diagram of a receiving-end converter control strategy provided according to an embodiment of the present disclosure;

[0014] Figure 4 is a schematic diagram of a first sending-end converter control strategy provided according to an embodiment of the present disclosure;

[0015] Figure 5 is a schematic diagram of a second sending-end converter control strategy provided according to an embodiment of the present disclosure;

[0016] Figure 6 is a schematic diagram of a bipolar converter cascade control device provided according to an embodiment of the present disclosure;

[0017] Figure 7 A block diagram of an exemplary electronic device suitable for implementing embodiments of the present disclosure is shown. DETAILED DESCRIPTION

[0018] In order to more clearly understand the above-mentioned objectives, features and advantages of the present disclosure, the scheme of the present disclosure will be further described below. It should be noted that the embodiments of the present disclosure and the features in the embodiments can be combined with each other without conflict.

[0019] In the following description, many specific details are set forth to facilitate a full understanding of the present disclosure, but the present disclosure may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present disclosure, rather than all of the embodiments.

[0020] It should be noted that the executor of the bipolar converter cascade control method of this embodiment may be a bipolar converter cascade control device, which may be implemented by software and / or hardware, and which may be configured in an electronic device, which may include but is not limited to a terminal, a server, etc.

[0021] Figure 1 is a flow chart of a bipolar converter cascade control method according to an embodiment of the present disclosure, such as Figure 1 As shown, the method includes:

[0022] S101: Determine a first control signal based on a first DC voltage and a corresponding reference voltage, a first reactive power and a corresponding first reference power of a receiving-end converter, and use the first control signal to control the receiving-end converter.

[0023] Figure 2 Schematic diagram of the grid-connected system structure provided according to an embodiment of the present disclosure, such as Figure 2 As shown, the grid-connected system of this embodiment includes a receiving-end converter (GSMMC), a first sending-end converter (WFMMC), and a second sending-end converter (PVMMC), wherein the AC side of the first sending-end converter (WFMMC) is connected to the wind farm side, the AC side of the second sending-end converter (PVMMC) is connected to the photovoltaic farm side, and the first sending-end converter (WFMMC) and the second sending-end converter (PVMMC) are connected in series, and the two ends of the series DC side are connected to the DC side of the receiving-end converter (GSMMC), and the receiving-end converter (GSMMC) is connected to the onshore power grid to achieve grid connection. The bipolar converter cascade control method of this embodiment can be executed by a bipolar converter cascade control device, that is, the bipolar converter cascade control device controls the receiving-end converter, the first sending-end converter, and the second sending-end converter respectively.

[0024] Among them, the task of the receiving end converter (GSMMC) is to maintain the constant voltage on the DC side of the system and provide a certain amount of reactive power support according to the needs of the onshore power grid. GSMMC adopts constant DC voltage and constant reactive power control (abbreviated as E dc / Q control) to achieve the control of DC voltage stability and reactive power balance at this level respectively, and its control target is to make DC voltage and reactive power reach reference values.

[0025] The actual DC voltage of the receiving end converter (GSMMC) is called the first DC voltage, which can be expressed by E dc The reference value corresponding to the actual DC voltage is called the reference voltage, which can be expressed by E dcref express.

[0026] The actual reactive power of the receiving end converter (GSMMC) is called the first reactive power, which can be expressed as Q g Indicates that the first reactive power Q g The corresponding reference value is called the first reference power, which can be expressed as Q gref express.

[0027] The control device of this embodiment can be based on the first DC voltage E of the receiving end converter (GSMMC) dc And reference voltage E dcref , the first reactive power Q g and the first reference power Q grefDetermine the first control signal (control voltage), which can be expressed as u cref_g express.

[0028] Some embodiments, Figure 3 is a schematic diagram of a receiving-end converter control strategy provided according to an embodiment of the present disclosure, such as Figure 3 As shown, the receiving-end converter (GSMMC) of this embodiment includes control strategies such as outer loop control, positive sequence current inner loop control, and negative sequence current inner loop control. Figure 3 As shown, when determining the first control signal u cre f _g In the process, firstly, based on the first DC voltage E dc And reference voltage E dcref , the first reactive power Q g and the first reference power Q gref The outer loop control is performed to obtain the first d-axis positive sequence current and the first q-axis positive sequence current, respectively. and Indicates that the outer loop control expression is:

[0029]

[0030] in, It is the PI parameters of d and q axes of the positive sequence outer loop control of the receiving-end converter.

[0031] Furthermore, the first d-axis positive sequence current and the first q-axis positive sequence current As the reference value of the d-axis and q-axis components of the positive sequence current inner loop control of the receiving-end converter, the positive sequence current inner loop control is performed to obtain the first positive sequence voltage, which can be used Among them, the positive sequence current inner loop control expression is as follows:

[0032]

[0033] in, is the reference value of the d-axis and q-axis components of the positive sequence voltage on the valve side of the receiving converter, The first positive sequence voltage is obtained by abc-dq phase coordinate transformation are the d-axis and q-axis PI parameters in the positive sequence inner loop control of the receiving-end converter; are the d-axis and q-axis components of the positive sequence current of the receiving-end converter; are the d-axis and q-axis components of the positive sequence voltage on the grid side of the receiving converter; is the d-axis and q-axis components of the positive sequence voltage on the valve side of the receiving converter; L eq is the equivalent inductance; ω is the angular frequency of the synchronous coordinate system.

[0034] And, the first d-axis negative sequence current (with ) and the first q-axis negative sequence current (expressed by As the reference value of the negative sequence current inner loop control d, q axis components to perform negative sequence current inner loop control, to obtain the first negative sequence voltage, which can be used In order to suppress the negative sequence current, the first d-axis negative sequence current and the first q-axis negative sequence current Set to 0, the expression of negative sequence current inner loop control is as follows:

[0035]

[0036] in, is the reference value of the d-axis and q-axis components of the negative sequence voltage on the valve side of the receiving converter, The first negative sequence voltage is obtained by abc-dq phase coordinate transformation are the d-axis and q-axis PI parameters in the negative sequence inner loop control of the receiving-end converter; are the d-axis and q-axis components of the negative sequence voltage on the grid side of the receiving converter; are the d-axis and q-axis components of the negative sequence voltage on the valve side of the receiving converter; It is the d-axis and q-axis components of the negative-sequence current of the receiving-end converter.

[0037] Further, based on the first positive sequence voltage and the first negative sequence voltage Determine the first control signal u cre f _g , and using the first control signal u cref_g The receiving-end converter (GSMMC) is controlled so that the DC voltage and reactive power of the receiving-end converter (GSMMC) reach reference values ​​respectively.

[0038] S102: Determine a second control signal based on the active power of the first sending-end converter and the corresponding active reference value, the second reactive power and the corresponding second reference power, and use the second control signal to control the first sending-end converter.

[0039] The first sending-end converter (WFMMC) of this embodiment is responsible for controlling the system power, and adopts fixed active power and fixed reactive power control (referred to as fixed P / Q control) to control the active power and reactive power of the local end to reach the rated reference values ​​respectively.

[0040] Among them, the actual active power of the first sending-end converter (WFMMC) can be expressed as P w Indicates that the active power corresponds to a rated reference value, which is called the active reference value, which can be expressed as P wref express.

[0041] The actual reactive power of the first sending-end converter (WFMMC) is called the second reactive power, which can be expressed as Q w Indicates that the second reactive power Q w The corresponding reference value is called the second reference power, which can be expressed as Q wref express.

[0042] The control device of this embodiment can be based on the active power P of the first sending-end converter (WFMMC) w And active reference value P wref , the second reactive power Q w and the second reference power Q wref Determine a second control signal, which can be expressed as u cref_w express.

[0043] Some embodiments, Figure 4 is a schematic diagram of a first sending-end converter control strategy provided according to an embodiment of the present disclosure, such as Figure 4 As shown, the first sending-end converter (WFMMC) of this embodiment includes control strategies such as outer loop control, positive sequence current inner loop control, and negative sequence current inner loop control. Figure 4 As shown, when determining the second control signal u cref_w In the process, firstly, based on the active power P w And active reference value P wref , the second reactive power Q w and the second reference power Q wref The outer loop control is performed to obtain the second d-axis positive sequence current and the second q-axis positive sequence current, respectively. and Indicates that the outer loop control expression is:

[0044]

[0045]

[0046] in, It is the PI parameters of d and q axes of the positive sequence outer loop control of the receiving-end converter.

[0047] Furthermore, the second d-axis positive sequence current and the second q-axis positive sequence current As the reference value of the d and q axis components of the positive sequence current inner loop control of the first sending-end converter, the positive sequence current inner loop control is performed to obtain the second positive sequence voltage, which can be used Among them, the positive sequence current inner loop control expression is as follows:

[0048]

[0049] in, is the reference value of the d-axis and q-axis components of the positive sequence voltage on the valve side of the first sending-end converter, The second positive sequence voltage is obtained by abc-dq phase coordinate transformation are the d-axis and q-axis PI parameters in the positive sequence inner loop control of the first sending-end converter; are the d-axis and q-axis components of the positive sequence current of the first sending-end converter; are the d-axis and q-axis components of the grid-side positive sequence voltage of the first sending-end converter; is the d-axis and q-axis components of the positive sequence voltage on the valve side of the first sending-end converter; L eq is the equivalent inductance; ω is the angular frequency of the synchronous coordinate system.

[0050] And, the second d-axis negative sequence current (with ) and the second q-axis negative sequence current (expressed by denoted) as the reference value of the d and q axis components in the negative sequence current inner loop control of the first sending-end converter to perform negative sequence current inner loop control to obtain the second negative sequence voltage, which can be used In order to suppress the negative sequence current, the second d-axis negative sequence current and the second q-axis negative sequence current Set to 0, the expression of negative sequence current inner loop control is as follows:

[0051]

[0052] in, is the reference value of the d-axis and q-axis components of the negative sequence voltage on the valve side of the first sending-end converter, The second negative sequence voltage is obtained by abc-dq phase coordinate transformation are the d-axis and q-axis PI parameters in the negative sequence inner loop control of the first sending-end converter; are the d-axis and q-axis components of the negative sequence voltage on the grid side of the first sending-end converter; are the d-axis and q-axis components of the negative sequence voltage on the valve side of the first sending-end converter; It is the d-axis and q-axis components of the negative-sequence current of the first sending-end converter.

[0053] Further, based on the second positive sequence voltage and the second negative sequence voltage Determine the second control signal u cqref_w , and using the second control signal u cre f _w The first sending-end converter (WFMMC) is controlled so that the active power and the reactive power of the first sending-end converter (WFMMC) reach reference values ​​respectively.

[0054] S103: Determine a third control signal based on the second DC voltage of the second sending-end converter, the first DC voltage of the first sending-end converter, the third reactive power and the corresponding third reference power, and use the third control signal to control the second sending-end converter.

[0055] In the embodiment of the present disclosure, the second sending-end converter (PVMMC) of the photovoltaic field is responsible for balancing the DC voltages at both poles to ensure that the DC voltages at the DC ends of the series converters are equal. dc =E dc1 -E dc2 ), fixed reactive power control, to achieve a DC voltage difference of 0 at both ends, where E dc2 represents the DC terminal voltage of the second sending-end converter (PVMMC), which can be called the second DC voltage; E dc1 represents the DC terminal voltage of the first sending-end converter (WFMMC), which can be called the first DC voltage, and serves as a reference value for controlling the second sending-end converter (PVMMC).

[0056] The actual reactive power of the second converter (PVMMC) is called the third reactive power, which can be expressed as Q p Indicates that the third reactive power Q p The corresponding reference value is called the third reference power, which can be expressed as Q pref express.

[0057] The control device of this embodiment can be based on the second DC voltage E of the second converter (PVMMC). dc2 and the first DC voltage E dc1 , the third reactive power Q p and the third reference power Q pref Determine the third control signal (control voltage), which can be expressed as u cref_p express.

[0058] Some embodiments, Figure 5 is a schematic diagram of a second sending-end converter control strategy provided according to an embodiment of the present disclosure, such as Figure 5 As shown, each second sending-end converter (PVMMC) of this embodiment includes control strategies such as outer loop control, positive sequence current inner loop control, and negative sequence current inner loop control. Figure 3 As shown, when determining the third control signal u cref_p In the process, firstly, based on the second DC voltage E dc2 and the first DC voltage E dc1 , the third reactive power Q p and the third reference power Q pref The outer loop control is performed to obtain the third d-axis positive sequence current and the third q-axis positive sequence current, respectively. and Indicates that the outer loop control expression is:

[0059]

[0060] in, It is the d-axis and q-axis PI parameters in the positive-sequence outer loop control of the second receiving-end converter.

[0061] Furthermore, the third d-axis positive sequence current and the third q-axis positive sequence current As the reference value of the d and q axis components of the positive sequence current inner loop control of the second sending-end converter, the positive sequence current inner loop control is performed to obtain the third positive sequence voltage, which can be used Among them, the positive sequence current inner loop control expression is as follows:

[0062]

[0063] in, is the reference value of the d-axis and q-axis components of the positive sequence voltage on the valve side of the second sending-end converter, The third positive sequence voltage is obtained by abc-dq phase coordinate transformation are the d-axis and q-axis PI parameters in the positive sequence inner loop control of the second sending-end converter; are the d-axis and q-axis components of the positive sequence current of the second sending-end converter; are the d-axis and q-axis components of the grid-side positive sequence voltage of the second sending-end converter; is the d-axis and q-axis components of the positive sequence voltage on the valve side of the second sending-end converter; L eq is the equivalent inductance; ω is the angular frequency of the synchronous coordinate system.

[0064] And, the third d-axis negative sequence current (with ) and the third q-axis negative sequence current (expressed by As the reference value of the negative sequence current inner loop control d, q axis components to perform negative sequence current inner loop control, to obtain the third negative sequence voltage, which can be used In order to suppress the negative sequence current, the third d-axis negative sequence current and the third q-axis negative sequence current Set to 0, the expression of negative sequence current inner loop control is as follows:

[0065]

[0066] in, is the reference value of the d-axis and q-axis components of the negative sequence voltage on the valve side of the second sending-end converter, The third negative sequence voltage is obtained by abc-dq phase coordinate transformation are the d-axis and q-axis PI parameters in the negative sequence inner loop control of the second sending-end converter; are the d-axis and q-axis components of the negative sequence voltage on the grid side of the second sending-end converter; are the d-axis and q-axis components of the negative sequence voltage on the valve side of the second sending-end converter; It is the d-axis and q-axis components of the negative-sequence current of the second sending-end converter.

[0067] Furthermore, based on the third positive sequence voltage and the third negative sequence voltage Determine the third control signal u cref_p , and using the third control signal u cref_p The second sending-end converter (PVMMC) is controlled so that the DC voltages across the second sending-end converter (PVMMC) and the first sending-end converter are equal.

[0068] In this embodiment, a first control signal is determined based on the first DC voltage and the corresponding reference voltage, the first reactive power and the corresponding first reference power of the receiving-end converter, and the first control signal is used to control the receiving-end converter; a second control signal is determined based on the active power and the corresponding active reference value, the second reactive power and the corresponding second reference power of the first sending-end converter, and the second control signal is used to control the first sending-end converter; and a third control signal is determined based on the second DC voltage of the second sending-end converter and the first DC voltage, the third reactive power and the corresponding third reference power of the first sending-end converter, and the third control signal is used to control the second sending-end converter. This allows the receiving-end converter to be controlled with a fixed DC voltage to ensure that the DC terminal voltages of the series converters are equal, thereby improving the stability of the grid-connected system.

[0069] In order to implement the above embodiments, the present disclosure also proposes a bipolar converter cascade control device.

[0070] Figure 6 is a schematic diagram of a bipolar converter cascade control device provided according to another embodiment of the present disclosure.

[0071] like Figure 6 As shown, the bipolar converter cascade control device 60 comprises:

[0072] A first control module 601 is used to determine a first control signal based on a first DC voltage and a corresponding reference voltage, a first reactive power and a corresponding first reference power of a receiving-end converter, and control the receiving-end converter using the first control signal;

[0073] A second control module 602, configured to determine a second control signal based on the active power of the first sending-end converter and the corresponding active reference value, the second reactive power and the corresponding second reference power, and control the first sending-end converter using the second control signal; and

[0074] The third control module 603 is used to determine a third control signal based on the second DC voltage of the second sending-end converter and the first DC voltage of the first sending-end converter, the third reactive power and the corresponding third reference power, and use the third control signal to control the second sending-end converter.

[0075] In some embodiments, the first control module 601 is specifically used to: perform outer-loop control based on the first DC voltage and the reference voltage, the first reactive power and the first reference power, respectively, to obtain a first d-axis positive-sequence current and a first q-axis positive-sequence current; perform inner-loop control of the positive-sequence current based on the first d-axis positive-sequence current and the first q-axis positive-sequence current to obtain a first positive-sequence voltage, and perform inner-loop control of the negative-sequence current based on the first d-axis negative-sequence current and the first q-axis negative-sequence current to obtain a first negative-sequence voltage; and determine a first control signal based on the first positive-sequence voltage and the first negative-sequence voltage.

[0076] In some embodiments, the first d-axis negative-sequence current and the first q-axis negative-sequence current are zero.

[0077] In some embodiments, the second control module 602 is specifically used to: perform outer-loop control based on active power and an active reference value, a second reactive power and a second reference power, respectively, to obtain a second d-axis positive-sequence current and a second q-axis positive-sequence current; perform inner-loop control of a positive-sequence current based on the second d-axis positive-sequence current and the second q-axis positive-sequence current to obtain a second positive-sequence voltage, and perform inner-loop control of a negative-sequence current based on the second d-axis negative-sequence current and the second q-axis negative-sequence current to obtain a second negative-sequence voltage; and determine a second control signal based on the second positive-sequence voltage and the second negative-sequence voltage.

[0078] In some embodiments, the third control module 603 is specifically used to: perform outer-loop control based on the second DC voltage and the first DC voltage, the third reactive power and the third reference power to obtain a third d-axis positive-sequence current and a third q-axis positive-sequence current; perform inner-loop control of the positive-sequence current based on the third d-axis positive-sequence current and the third q-axis positive-sequence current to obtain a third positive-sequence voltage, and perform inner-loop control of the negative-sequence current based on the third d-axis negative-sequence current and the third q-axis negative-sequence current to obtain a third negative-sequence voltage; and determine a third control signal based on the third positive-sequence voltage and the third negative-sequence voltage.

[0079] In this embodiment, a first control signal is determined based on the first DC voltage and the corresponding reference voltage, the first reactive power and the corresponding first reference power of the receiving-end converter, and the first control signal is used to control the receiving-end converter; a second control signal is determined based on the active power and the corresponding active reference value, the second reactive power and the corresponding second reference power of the first sending-end converter, and the second control signal is used to control the first sending-end converter; and a third control signal is determined based on the second DC voltage of the second sending-end converter and the first DC voltage, the third reactive power and the corresponding third reference power of the first sending-end converter, and the third control signal is used to control the second sending-end converter. This allows the receiving-end converter to be controlled with a fixed DC voltage to ensure that the DC terminal voltages of the series converters are equal, thereby improving the stability of the grid-connected system.

[0080] According to an embodiment of the present disclosure, the present disclosure also provides an electronic device, a readable storage medium and a computer program product.

[0081] In order to implement the above embodiments, the present disclosure further proposes a computer program product. When the instruction processor in the computer program product executes, the bipolar converter cascade control method proposed in the above embodiments of the present disclosure is executed.

[0082] Figure 7 A block diagram of an exemplary electronic device suitable for implementing embodiments of the present disclosure is shown. Figure 7 The electronic device 12 shown is only an example and should not bring any limitation to the functions and scope of use of the embodiments of the present disclosure.

[0083] like Figure 7 As shown, the electronic device 12 is in the form of a general purpose computing device. The components of the electronic device 12 may include, but are not limited to: one or more processors or processing units 16, a system memory 28, and a bus 18 that connects various system components (including the system memory 28 and the processing unit 16).

[0084] The bus 18 represents one or more of several types of bus structures, including a memory bus or memory controller, a peripheral bus, a graphics acceleration port, a processor or a local bus using any of a variety of bus structures. For example, these architectures include but are not limited to Industry Standard Architecture (ISA) bus, Micro Channel Architecture (MAC) bus, Enhanced ISA bus, Video Electronics Standards Association (VESA) local bus and Peripheral Component Interconnection (PCI) bus.

[0085] The electronic device 12 typically includes a variety of computer system readable media. These media can be any available media that can be accessed by the electronic device 12, including volatile and non-volatile media, removable and non-removable media.

[0086] The memory 28 may include computer system readable media in the form of volatile memory, such as random access memory (RAM) 30 and / or cache memory 32. The electronic device 12 may further include other removable / non-removable, volatile / non-volatile computer system storage media. By way of example only, the storage system 34 may be used to read and write non-removable, non-volatile magnetic media ( Figure 7 Not shown, often called a "hard drive").

[0087] although Figure 7 Not shown in the figure, a disk drive for reading and writing a removable non-volatile disk (e.g., a "floppy disk"), and an optical disk drive for reading and writing a removable non-volatile optical disk (e.g., a compact disc read only memory (CD-ROM), a digital versatile disc read only memory (DVD-ROM), or other optical media) may be provided. In these cases, each drive may be connected to the bus 18 via one or more data medium interfaces. The memory 28 may include at least one program product having a set (e.g., at least one) of program modules configured to perform the functions of the various embodiments of the present disclosure.

[0088] A program / utility 40 having a set (at least one) of program modules 42 may be stored, for example, in the memory 28, such program modules 42 including but not limited to an operating system, one or more application programs, other program modules, and program data, each of which or some combination may include an implementation of a network environment. The program modules 42 generally perform the functions and / or methods of the embodiments described in the present disclosure.

[0089] The electronic device 12 may also communicate with one or more external devices 14 (e.g., keyboards, pointing devices, displays 24, etc.), may also communicate with one or more devices that enable a user to interact with the electronic device 12, and / or may communicate with any device that enables the electronic device 12 to communicate with one or more other computing devices (e.g., network cards, modems, etc.). Such communication may be performed via an input / output (I / O) interface 22. Furthermore, the electronic device 12 may also communicate with one or more networks (e.g., a local area network (LAN), a wide area network (WAN), and / or a public network, such as the Internet) via a network adapter 20. As shown, the network adapter 20 communicates with other modules of the electronic device 12 via a bus 18. It should be understood that, although not shown in the figure, other hardware and / or software modules may be used in conjunction with the electronic device 12, including but not limited to: microcode, device drivers, redundant processing units, external disk drive arrays, RAID systems, tape drives, and data backup storage systems.

[0090] The processing unit 16 executes various functional applications by running the programs stored in the system memory 28, such as implementing the bipolar converter cascade control method mentioned in the above embodiment.

[0091] Those skilled in the art will readily appreciate other embodiments of the present disclosure after considering the specification and practicing the invention disclosed herein. The present disclosure is intended to cover any variations, uses or adaptations of the present disclosure that follow the general principles of the present disclosure and include common knowledge or customary techniques in the art that are not disclosed in the present disclosure. The description and examples are to be considered exemplary only, and the true scope and spirit of the present disclosure are indicated by the following claims.

[0092] It should be understood that the present disclosure is not limited to the exact structures that have been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present disclosure is limited only by the appended claims.

[0093] It should be noted that, in the description of the present disclosure, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. In addition, in the description of the present disclosure, unless otherwise specified, the meaning of "plurality" is two or more.

[0094] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code that includes one or more executable instructions for implementing the steps of a specific logical function or process, and the scope of the preferred embodiments of the present disclosure includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by those skilled in the art to which the embodiments of the present disclosure belong.

[0095] It should be understood that the various parts of the present disclosure can be implemented in hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, multiple steps or methods can be implemented in software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0096] A person skilled in the art may understand that all or part of the steps in the method for implementing the above-mentioned embodiment may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one or a combination of the steps of the method embodiment.

[0097] In addition, each functional unit in each embodiment of the present disclosure may be integrated into a processing module, or each unit may exist physically separately, or two or more units may be integrated into one module. The above-mentioned integrated module may be implemented in the form of hardware or in the form of a software functional module. If the integrated module is implemented in the form of a software functional module and sold or used as an independent product, it may also be stored in a computer-readable storage medium.

[0098] The storage medium mentioned above can be a read-only memory, a magnetic disk or an optical disk, etc.

[0099] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present disclosure. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0100] Although the embodiments of the present disclosure have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present disclosure. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present disclosure.

Claims

1. A bipolar converter cascade control method, characterized in that: The grid-connected system comprises a first sending-end converter connected to a wind farm, a second sending-end converter connected to a photovoltaic field, and a receiving-end converter, wherein the first sending-end converter and the second sending-end converter are connected in series, and the method comprises: Determine a first control signal based on a first DC voltage and a corresponding reference voltage, a first reactive power and a corresponding first reference power of the receiving-end converter, and control the receiving-end converter using the first control signal; determining a second control signal based on the active power and the corresponding active reference value of the first sending-end converter, the second reactive power and the corresponding second reference power, and controlling the first sending-end converter using the second control signal; and A third control signal is determined based on the second DC voltage of the second sending-end converter, the first DC voltage of the first sending-end converter, the third reactive power and the corresponding third reference power, and the second sending-end converter is controlled using the third control signal.

2. The method according to claim 1, characterized in that The determining of the first control signal based on the first DC voltage and the corresponding reference voltage, the first reactive power and the corresponding first reference power of the receiving-end converter comprises: Performing outer loop control based on the first DC voltage and the reference voltage, the first reactive power and the first reference power respectively to obtain a first d-axis positive-sequence current and a first q-axis positive-sequence current; performing a positive-sequence current inner loop control based on the first d-axis positive-sequence current and the first q-axis positive-sequence current to obtain a first positive-sequence voltage, and performing a negative-sequence current inner loop control based on the first d-axis negative-sequence current and the first q-axis negative-sequence current to obtain a first negative-sequence voltage; and The first control signal is determined based on the first positive-sequence voltage and the first negative-sequence voltage.

3. The method according to claim 2, characterized in that in, The first d-axis negative-sequence current and the first q-axis negative-sequence current are zero.

4. The method according to claim 1, characterized in that The determining of the second control signal based on the active power and the corresponding active reference value of the first sending-end converter, the second reactive power and the corresponding second reference power includes: Performing outer loop control based on the active power and the active reference value, the second reactive power and the second reference power respectively to obtain a second d-axis positive-sequence current and a second q-axis positive-sequence current; Performing positive-sequence current inner loop control based on the second d-axis positive-sequence current and the second q-axis positive-sequence current to obtain a second positive-sequence voltage, and performing negative-sequence current inner loop control based on the second d-axis negative-sequence current and the second q-axis negative-sequence current to obtain a second negative-sequence voltage; and The second control signal is determined based on the second positive-sequence voltage and the second negative-sequence voltage.

5. The method according to claim 1, characterized in that Determining a third control signal based on the second DC voltage of the second sending-end converter, the first DC voltage of the first sending-end converter, the third reactive power and the corresponding third reference power includes: performing outer loop control based on the second DC voltage and the first DC voltage, the third reactive power and the third reference power to obtain a third d-axis positive-sequence current and a third q-axis positive-sequence current; performing a positive-sequence current inner loop control based on the third d-axis positive-sequence current and the third q-axis positive-sequence current to obtain a third positive-sequence voltage, and performing a negative-sequence current inner loop control based on the third d-axis negative-sequence current and the third q-axis negative-sequence current to obtain a third negative-sequence voltage; and The third control signal is determined based on the third positive-sequence voltage and the third negative-sequence voltage.

6. A bipolar converter cascade control device, characterized in that: The grid-connected system comprises a first sending-end converter connected to a wind farm, a second sending-end converter connected to a photovoltaic field, and a receiving-end converter, wherein the first sending-end converter and the second sending-end converter are connected in series, and the device comprises: A first control module, configured to determine a first control signal based on a first DC voltage and a corresponding reference voltage, a first reactive power and a corresponding first reference power of the receiving-end converter, and control the receiving-end converter using the first control signal; a second control module, configured to determine a second control signal based on the active power and the corresponding active reference value of the first sending-end converter, the second reactive power and the corresponding second reference power, and control the first sending-end converter using the second control signal; and The third control module is used to determine a third control signal based on the second DC voltage of the second sending-end converter and the first DC voltage of the first sending-end converter, the third reactive power and the corresponding third reference power, and use the third control signal to control the second sending-end converter.

7. The device according to claim 6, characterized in that The first control module is specifically used to: Performing outer loop control based on the first DC voltage and the reference voltage, the first reactive power and the first reference power respectively to obtain a first d-axis positive-sequence current and a first q-axis positive-sequence current; Performing a positive-sequence current inner loop control based on the first d-axis positive-sequence current and the first q-axis positive-sequence current to obtain a first positive-sequence voltage, and performing a negative-sequence current inner loop control based on the first d-axis negative-sequence current and the first q-axis negative-sequence current to obtain a first negative-sequence voltage; as well as The first control signal is determined based on the first positive-sequence voltage and the first negative-sequence voltage.

8. The device according to claim 6, characterized in that The second control module is specifically used for: Performing outer loop control based on the active power and the work reference value, the second reactive power and the second reference power respectively to obtain a second d-axis positive sequence current and a second q-axis positive sequence current; Performing a positive-sequence current inner loop control based on the second d-axis positive-sequence current and the second q-axis positive-sequence current to obtain a second positive-sequence voltage, and performing a negative-sequence current inner loop control based on the second d-axis negative-sequence current and the second q-axis negative-sequence current to obtain a second negative-sequence voltage; as well as The second control signal is determined based on the second positive-sequence voltage and the second negative-sequence voltage.

9. The device according to claim 6, characterized in that The third control module is specifically used for: performing outer loop control based on the second DC voltage and the first DC voltage, the third reactive power and the third reference power to obtain a third d-axis positive-sequence current and a third q-axis positive-sequence current; performing a positive-sequence current inner loop control based on the third d-axis positive-sequence current and the third q-axis positive-sequence current to obtain a third positive-sequence voltage, and performing a negative-sequence current inner loop control based on the third d-axis negative-sequence current and the third q-axis negative-sequence current to obtain a third negative-sequence voltage; and The third control signal is determined based on the third positive-sequence voltage and the third negative-sequence voltage.

10. A non-transitory computer-readable storage medium storing computer instructions, wherein: The computer instructions are used to cause the computer to execute the method according to any one of claims 1-5.

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