Flexible direct-current fault ride-through control method and apparatus, storage medium and device

Abstract

A flexible direct-current fault ride-through control method and apparatus, a storage medium, and a device, which relate to the technical field of power system control. The method comprises: acquiring an alternating-current side terminal voltage of a converter valve and an externally transmitted power of a flexible direct-current converter station; if the alternating-current side terminal voltage is lower than a low-voltage ride-through threshold, triggering low-voltage ride-through, and acquiring an active power instruction value during a fault period; determining a second integrator coefficient during the fault period according to the difference between the active power instruction value and the externally transmitted power; switching an integrator coefficient of a voltage outer-loop controller from a pre-fault first integrator coefficient to the second integrator coefficient; the difference between the active power instruction value during the fault period and the externally transmitted power having a negative correlation relationship with the second integrator coefficient; acquiring an alternating-current side terminal voltage in real time; and if the real-time value of the alternating-current side terminal voltage is higher than the low-voltage ride-through threshold, executing fault recovery, and switching the integrator coefficient of the voltage outer-loop controller to the first integrator coefficient. The present application can improve the stability of an isolated island system that transmits new energy by means of flexible direct current.

Description

Flexible DC fault ride-through control method, device, storage medium and equipment

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on June 29, 2023, with application number 202310789851.8 and invention name “Flexible DC fault ride-through control method, device, storage medium and equipment”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of power system control technology, and in particular to a flexible direct current fault ride-through control method, device, storage medium and computer equipment. Background Art

[0003] Accelerating the construction of large-scale wind and photovoltaic power bases, primarily in desert, Gobi, and other uninhabited areas, is a major strategic imperative for China's current power system development. These large-scale, purely renewable energy bases, with their large installed capacity and widespread distribution, often utilize a flexible DC island transmission mode. Existing fault ride-through strategies for the flexible DC VF control (constant AC voltage / constant frequency control) mode are primarily targeted at offshore wind power transmission systems. Transmission systems at large, purely renewable energy bases have a higher probability of failure and place even higher demands on the stability of the transmission-end system after a failure.

[0004] To ensure transient stability at the sending end of large-scale renewable energy bases, the sending-end renewable energy system must proactively reduce power during faults and slow the rate of power recovery. However, existing flexible DC systems freeze the outer loop controller during faults to prevent integral control saturation. For the sending-end system of large-scale renewable energy bases, this results in a lack of a power source capable of regulating voltage during transients. This can easily lead to voltage stability issues after a fault in the sending-end system of a large renewable energy base. If a normal control outer loop controller is used, excessive outer loop deviation and rapid action can cause transient stability issues in the event of a deep fault.

[0005] Summary of the Invention

[0006] The embodiments of the present application provide a flexible direct current fault ride-through control method, apparatus, storage medium, and device, which can improve the stability of a system in which pure new energy is transmitted via a flexible direct current island.

[0007] In a first aspect, the present application provides a flexible DC fault ride-through control method, which is applied to a flexible DC converter station in a system for transmitting pure renewable energy via a flexible DC island. The method comprises:

[0008] Obtaining the AC side terminal voltage of the converter valve and the external power transmission of the flexible DC converter station;

[0009] If the AC side terminal voltage is less than the low voltage ride-through threshold, low voltage ride-through is triggered to obtain the active power command value during the fault period;

[0010] determining a second integral coefficient during a fault period according to a difference between the active power command value and the external power;

[0011] Switching the integral coefficient of the voltage outer loop controller from the first integral coefficient before the fault to the second integral coefficient; wherein the first integral coefficient is greater than the second integral coefficient, and the difference between the active power command value and the external power during the fault period is negatively correlated with the second integral coefficient;

[0012] Get AC side terminal voltage in real time;

[0013] If the real-time value of the AC side terminal voltage is higher than the low voltage ride-through threshold, fault recovery is performed and the integral coefficient of the voltage outer loop controller is switched to the first integral coefficient.

[0014] In one embodiment, obtaining the active power command value during the fault period includes:

[0015] Obtain the external power delivered by the flexible DC converter station within a preset time period before triggering low voltage ride-through;

[0016] Calculating an average value of the external power transmitted by the flexible DC converter station within the preset time period;

[0017] The average value is determined as the active power command value during the fault period.

[0018] In one embodiment, the preset duration is greater than or equal to 60 seconds.

[0019] In one embodiment, during the low voltage ride-through period, the method further includes:

[0020] regularly obtaining the external power transmission of the flexible DC converter station;

[0021] The second integral coefficient is dynamically adjusted according to the real-time value of the external power transmitted by the flexible DC converter station.

[0022] In one embodiment, during the low voltage ride-through period, after determining the first integral coefficient according to the difference between the active power command value and the external power, the method further includes:

[0023] Calculating a second proportional coefficient during a fault period according to the first integral coefficient, the second integral coefficient, and a first proportional coefficient of a voltage outer loop controller before a fault;

[0024] The proportional coefficient of the voltage outer loop controller is switched from the first proportional coefficient to the second proportional coefficient until it is switched back to the first proportional coefficient when fault recovery is performed.

[0025] In a second aspect, the present application provides a flexible DC fault ride-through control device, which is applied to a flexible DC converter station in a system for transmitting pure renewable energy via a flexible DC island. The device comprises:

[0026] A first acquisition module is configured to acquire the AC side terminal voltage of the converter valve and the external power transmission of the flexible DC converter station;

[0027] A low voltage ride-through module, configured to initiate a low voltage ride-through when the AC side terminal voltage is lower than a low voltage ride-through threshold, and obtain an active power command value during the fault period;

[0028] A first determining module, configured to determine a second integral coefficient during a fault period according to a difference between the active power command value and the external power;

[0029] a first switching module, configured to switch an integral coefficient of a voltage outer loop controller from a first integral coefficient before a fault to a second integral coefficient; wherein the first integral coefficient is greater than the second integral coefficient, and a difference between an active power command value and the external power during the fault period is negatively correlated with the second integral coefficient;

[0030] The second acquisition module is used to obtain the AC side terminal voltage in real time;

[0031] A fault recovery module is used to perform fault recovery and switch the integral coefficient of the voltage outer loop controller to the first integral coefficient when the real-time value of the AC side terminal voltage is higher than the low voltage crossing threshold.

[0032] In one embodiment, the low voltage ride-through module includes:

[0033] A power acquisition unit, configured to acquire the external power delivered by the flexible DC converter station within a preset time period before triggering low voltage ride-through;

[0034] a calculation unit, configured to calculate an average value of the external power transmitted by the flexible DC converter station within the preset time period;

[0035] The command value configuration unit is used to determine the average value as the active power command value during the fault period.

[0036] In one embodiment, the apparatus further comprises:

[0037] A power monitoring module, configured to periodically obtain the external power delivered by the flexible DC converter station during low voltage ride-through;

[0038] A dynamic adjustment module is used to dynamically adjust the second integral coefficient according to the real-time value of the external power transmitted by the flexible DC converter station during low voltage ride-through.

[0039] In a third aspect, the present application provides a storage medium storing computer-readable instructions. When the computer-readable instructions are executed by one or more processors, the one or more processors execute the steps of the flexible DC fault ride-through control method as described in any of the above embodiments.

[0040] In a fourth aspect, the present application provides a computer device, comprising: one or more processors, and a memory;

[0041] The memory stores computer-readable instructions, and when the one or more processors execute the computer-readable instructions, the steps of the flexible DC fault ride-through control method as described in any one of the above embodiments are performed.

[0042] It can be seen from the above technical solutions that the embodiments of the present application have the following advantages:

[0043] The flexible DC fault ride-through control method, device, storage medium and computer equipment provided in the present application monitor the AC side terminal voltage of the converter valve and the external power transmission of the flexible DC converter station, trigger the low voltage ride-through process when the AC side terminal voltage is less than the low voltage ride-through threshold, determine the second integral coefficient of the voltage outer loop controller during the fault period according to the difference between the active power command value and the external power transmission during the fault period, and switch it, reduce the integral coefficient of the voltage outer loop controller, and end the low voltage ride-through and enter the fault recovery process when the real-time value of the AC side terminal voltage is higher than the low voltage ride-through threshold. The integral coefficient of the voltage outer loop controller is switched back to the first integral coefficient before the fault, so that the outer loop of the flexible DC converter station maintains a certain integral capacity during the fault while avoiding the current command value from changing rapidly due to the voltage deviation and deviating too much from the steady-state value, thereby improving the transient stability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0045] FIG1 is a schematic diagram of an application scenario of a flexible DC fault ride-through control method in one embodiment;

[0046] FIG2 is a schematic flow chart of a flexible DC fault ride-through control method in one embodiment;

[0047] FIG3 is a schematic diagram showing the correlation between the difference between the active power command value and the external power and the second integral coefficient in one embodiment;

[0048] FIG4 is a schematic diagram of fault ride-through control logic in one embodiment;

[0049] FIG5 is a flow chart of the steps for obtaining an active power command value during a fault period in one embodiment;

[0050] FIG6 is a structural block diagram of a flexible DC fault ride-through control device in one embodiment;

[0051] FIG7 is a diagram showing the internal structure of a computer device in one embodiment. DETAILED DESCRIPTION

[0052] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0053] For island transmission systems, existing flexible DC systems mostly use a VF control method, where a given frequency generates a control phase, with the d-axis and q-axis control branches divided into outer and inner loop control. In existing flexible DC fault ride-through control methods, during fault ride-through, upon detecting a low voltage ride-through signal, the outer loop controller freezes, limiting the output current amplitude based on the voltage drop. The output current is then proportionally distributed based on the magnitude of the outer loop output d-axis and q-axis current command values, resulting in the limited d-axis and q-axis current command values. However, freezing the outer loop controller results in a lack of a power source capable of regulating voltage during transients, which can easily lead to voltage stability issues after a fault occurs in the sending-end system. In the case of a deep fault, excessive outer loop deviation and rapid operation can cause transient stability issues.

[0054] Based on the above problems, an embodiment of the present application provides a flexible DC fault ride-through control method, which is applied to a flexible DC converter station in a pure new energy transmission system via a flexible DC island. Pure new energy refers to only new energy generator sets, such as only photovoltaic power generation, or photovoltaic power generation and wind power discharge, etc. The embodiment of the present application is illustrated by taking the scenario shown in Figure 1 as an example. The photovoltaic power generation base transmits power through a long line impedance and realizes power transmission through a flexible DC converter. A three-phase grounding fault occurs at the busbar port of the flexible DC converter. The photovoltaic power generation base adopts a power reduction control strategy to perform fault ride-through control.

[0055] As shown in FIG2 , an embodiment of the present application provides a flexible DC fault ride-through control method, the method comprising:

[0056] Step S201: Acquire the AC side terminal voltage of the converter valve and the external power transmission of the flexible DC converter station.

[0057] The converter valve is the core equipment of a flexible DC transmission project. It primarily consists of an IGBT, a control drive unit, a cooling system, a saturable reactor, capacitors, and resistors. Unlike the semi-controlled thyristors used in conventional DC transmission projects, the converter valves in flexible DC projects mostly use fully controlled IGBTs, which convert AC to DC by controlling their on and off states. The AC-side terminal voltage of the converter valve and the output power of the flexible DC converter station are measured in real time using testing equipment.

[0058] Step S202: If the AC side voltage is less than the low voltage ride-through threshold, the low voltage ride-through is triggered and the active power command value during the fault period is obtained.

[0059] The low voltage ride-through threshold is a preset voltage threshold used to determine whether the flexible DC terminal needs to enter the low voltage ride-through process. When the AC side voltage is lower than the low voltage ride-through threshold, the low voltage ride-through process is not initiated and the active power command value during the fault period is obtained.

[0060] Step S203: According to the active power command value and the external power P e The difference ΔP e Determine the second integral coefficient k during the fault period iac2 .

[0061] Referring to Figure 3, the active power command value during the fault period is The difference between the external power P and the external power P is ΔP e , and the second integral coefficient k iac2 There is a negative correlation, that is, ΔP e The larger the second integral coefficient k is, the iac2 The smaller it is.

[0062] Step S204: the integral coefficient of the voltage outer loop controller is changed from the first integral coefficient k before the fault to iac1 Switch to the second integral coefficient k iac2 .

[0063] Among them, the first integral coefficient is greater than the second integral coefficient, and the integral coefficient is switched to the second integral coefficient k iac2 That is, to reduce the integral coefficient of the voltage outer loop controller to reduce the speed at which the current command value is affected by the voltage deviation during the fault period.

[0064] Step S205: Acquire the AC side terminal voltage in real time.

[0065] During the low voltage ride-through period, it is also necessary to obtain the AC side terminal voltage in real time to determine whether to end the low voltage ride-through and perform fault recovery.

[0066] Step S206: If the real-time value of the AC side terminal voltage is higher than the low voltage ride-through threshold, the fault recovery is performed and the integral coefficient of the voltage outer loop controller is switched to the first integral coefficient k iac1 .

[0067] When entering the fault recovery process, the integral coefficient of the voltage outer loop controller is switched back to the first integral coefficient k before the fault. iac1 .

[0068] 4 shows the fault ride-through control logic in this embodiment. Under normal circumstances, lvrt=0, and the integral coefficient of the flexible DC voltage outer loop controller adopts the first integral coefficient k iac1 When a fault occurs, lvrt=1, and the integral coefficient of the flexible DC voltage outer loop controller adopts the second integral coefficient k iac2 The outer loop voltage deviation is controlled by proportional integral to generate the current command. and Then the final current instruction is generated through proportional limiting value. and

[0069] In this embodiment, by monitoring the AC side terminal voltage of the converter valve and the external power transmission of the flexible DC converter station, the low voltage ride-through process is triggered when the AC side terminal voltage is lower than the low voltage ride-through threshold. The second integral coefficient k of the voltage outer loop controller during the fault period is determined according to the difference between the active power command value and the external power transmission during the fault period. iac2 And switch, reduce the integral coefficient of the voltage outer loop controller until the real-time value of the AC side voltage is higher than the low voltage ride-through threshold, end the low voltage ride-through and enter the fault recovery process, and switch the integral coefficient of the voltage outer loop controller back to the first integral coefficient k before the fault. iac1 , so that the outer loop of the flexible DC converter station maintains a certain integration capability during the fault period, while preventing the current command value from changing too rapidly due to the influence of voltage deviation and deviating too much from the steady-state value, thereby improving the transient stability of the system.

[0070] As shown in FIG5 , in one embodiment, obtaining the active power command value during the fault period includes:

[0071] Step S501, obtaining the external power delivered by the flexible DC converter station within a preset time period before triggering low voltage ride-through;

[0072] Step S502, calculating the average value of the external power transmitted by the flexible DC converter station within a preset time period;

[0073] Step S503: determine the average value as the active power command value during the fault period.

[0074] In this embodiment, the average value of the external power delivered during a preset time interval between triggering LVRT is used as the active power command value during the fault period. This means that the steady-state value before the fault is used as the reference value. By taking the average value, measurement errors during operation and errors caused by normal fluctuations are reduced, thereby improving system stability during LVRT. In one embodiment, the preset time interval is greater than or equal to 60 seconds.

[0075] In one embodiment, during the low voltage ride-through period, the flexible DC fault ride-through control method further includes:

[0076] Regularly obtain the external power transmission of the flexible DC converter station;

[0077] The second integral coefficient is dynamically adjusted according to the real-time value of the transmitted power of the flexible DC converter station.

[0078] In this embodiment, if the external power changes during the low voltage ride-through period, the first integral coefficient is dynamically adjusted, that is, the first integral coefficient is dynamically adjusted according to the difference between the active power command value and the real-time external power value.

[0079] In one embodiment, during the low voltage ride-through period, after determining the first integral coefficient based on the difference between the active power command value and the external power, the flexible DC fault ride-through control method further includes:

[0080] According to the first integral coefficient k iac1 , the second integral coefficient k iac2 And the first proportional coefficient k of the voltage outer loop controller before the fault p1 , calculate the second proportional coefficient k during the fault period p2 ;

[0081] The proportional coefficient of the voltage outer loop controller is changed from the first proportional coefficient k p1 Switch to the second proportional coefficient k p2 , until the fault recovery is performed and the first proportional coefficient k is switched back p1 .

[0082] The second proportional coefficient is calculated according to the following formula:

[0083] In this embodiment, during low voltage ride-through, the integral coefficient and proportional coefficient of the voltage outer loop controller are adjusted at the same time. The proportional coefficient will affect the degree of change of the current command value with the deviation of the voltage command value, which can help limit the current command value from deviating too much from the steady-state value, and the fault recovery process switches back to the first proportional coefficient before the fault.

[0084] It should be understood that, although the various steps in the flowcharts involved in the various embodiments described above are displayed in sequence according to the instructions of the arrows, these steps are not necessarily executed in sequence in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order restriction on the execution of these steps, and these steps can be executed in other orders. Moreover, at least a portion of the steps in the flowcharts involved in the various embodiments described above can include multiple steps or multiple stages, and these steps or stages are not necessarily executed and completed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a portion of steps or stages in other steps.

[0085] The flexible DC fault ride-through control device provided in an embodiment of the present application is described below. The flexible DC fault ride-through control device described below and the flexible DC fault ride-through control method described above can be referenced to each other.

[0086] As shown in FIG6 , an embodiment of the present application provides a flexible DC fault ride-through control device 600 , which is applied to a flexible DC converter station in a system for transmitting pure renewable energy via a flexible DC island. The device includes:

[0087] A first acquisition module 601 is configured to acquire the AC side terminal voltage of the converter valve and the external power transmitted by the flexible DC converter station;

[0088] A low voltage ride-through module 602 is configured to initiate a low voltage ride-through when the AC side terminal voltage is less than a low voltage ride-through threshold, and obtain an active power command value during the fault period;

[0089] A first determining module 603 is configured to determine a second integral coefficient during a fault period according to a difference between the active power command value and the external power;

[0090] a first switching module 604 configured to switch the integral coefficient of the voltage outer loop controller from the first integral coefficient before the fault to the second integral coefficient; wherein the first integral coefficient is greater than the second integral coefficient, and a difference between the active power command value and the external power during the fault period is negatively correlated with the second integral coefficient;

[0091] The second acquisition module 605 is used to obtain the AC side terminal voltage in real time;

[0092] The fault recovery module 606 is configured to perform fault recovery and switch the integral coefficient of the voltage outer loop controller to the first integral coefficient when the real-time value of the AC side terminal voltage is higher than the low voltage ride-through threshold.

[0093] In one embodiment, the low voltage ride-through module includes:

[0094] A power acquisition unit, configured to acquire the external power delivered by the flexible DC converter station within a preset time period before triggering low voltage ride-through;

[0095] a calculation unit, configured to calculate an average value of the external power transmitted by the flexible DC converter station within the preset time period;

[0096] The command value configuration unit is used to determine the average value as the active power command value during the fault period.

[0097] In one embodiment, the apparatus further comprises:

[0098] A power monitoring module, configured to periodically obtain the external power delivered by the flexible DC converter station during low voltage ride-through;

[0099] A dynamic adjustment module is used to dynamically adjust the second integral coefficient according to the real-time value of the external power transmitted by the flexible DC converter station during low voltage ride-through.

[0100] In one embodiment, the apparatus further comprises:

[0101] A second calculation module is configured to calculate, during the low voltage ride-through period, a second proportional coefficient during the fault period based on the first integral coefficient, the second integral coefficient, and the first proportional coefficient of the voltage outer loop controller before the fault;

[0102] The second switching module is used to switch the proportional coefficient of the voltage outer loop controller from the first proportional coefficient to the second proportional coefficient until it is switched back to the first proportional coefficient when fault recovery is performed.

[0103] The division of the various modules in the flexible DC fault ride-through control device described above is for illustrative purposes only. In other embodiments, the flexible DC fault ride-through control device can be divided into different modules as needed to perform all or part of the functions of the flexible DC fault ride-through control device described above. The various modules in the flexible DC fault ride-through control device described above can be implemented in whole or in part through software, hardware, or a combination thereof. The modules can be embedded in or independent of a processor in a computer device in hardware form, or stored in a memory in the computer device in software form, so that the processor can call and execute the corresponding operations of each module.

[0104] In one embodiment, the present application further provides a storage medium having computer-readable instructions stored therein. When the computer-readable instructions are executed by one or more processors, the one or more processors are caused to perform the following steps:

[0105] Obtaining the AC side terminal voltage of the converter valve and the external power transmission of the flexible DC converter station;

[0106] If the AC side terminal voltage is less than the low voltage ride-through threshold, low voltage ride-through is triggered to obtain the active power command value during the fault period;

[0107] determining a second integral coefficient during a fault period according to a difference between the active power command value and the external power;

[0108] Switching the integral coefficient of the voltage outer loop controller from the first integral coefficient before the fault to the second integral coefficient; wherein the first integral coefficient is greater than the second integral coefficient, and the difference between the active power command value and the external power during the fault period is negatively correlated with the second integral coefficient;

[0109] Get AC side terminal voltage in real time;

[0110] If the real-time value of the AC side terminal voltage is higher than the low voltage ride-through threshold, fault recovery is performed, and the integral coefficient of the voltage outer loop controller is switched to the first integral coefficient.

[0111] In one embodiment, the computer readable instructions, when executed by a processor, further implement the following steps:

[0112] Obtain the external power delivered by the flexible DC converter station within a preset time period before triggering low voltage ride-through;

[0113] Calculating an average value of the external power transmitted by the flexible DC converter station within the preset time period;

[0114] The average value is determined as the active power command value during the fault period.

[0115] In one embodiment, the computer readable instructions, when executed by a processor, further implement the following steps:

[0116] regularly obtaining the external power transmission of the flexible DC converter station;

[0117] The second integral coefficient is dynamically adjusted according to the real-time value of the external power transmitted by the flexible DC converter station.

[0118] In one embodiment, the computer readable instructions, when executed by a processor, further implement the following steps:

[0119] Calculating a second proportional coefficient during a fault period according to the first integral coefficient, the second integral coefficient, and a first proportional coefficient of a voltage outer loop controller before a fault;

[0120] The proportional coefficient of the voltage outer loop controller is switched from the first proportional coefficient to the second proportional coefficient until it is switched back to the first proportional coefficient when fault recovery is performed.

[0121] In one embodiment, the present application further provides a computer device having computer-readable instructions stored therein, wherein when the one or more processors execute the computer-readable instructions, the following steps are performed:

[0122] Obtaining the AC side terminal voltage of the converter valve and the external power transmission of the flexible DC converter station;

[0123] If the AC side terminal voltage is less than the low voltage ride-through threshold, low voltage ride-through is triggered to obtain the active power command value during the fault period;

[0124] determining a second integral coefficient during a fault period according to a difference between the active power command value and the external power;

[0125] Switching the integral coefficient of the voltage outer loop controller from the first integral coefficient before the fault to the second integral coefficient; wherein the first integral coefficient is greater than the second integral coefficient, and the difference between the active power command value and the external power during the fault period is negatively correlated with the second integral coefficient;

[0126] Get AC side terminal voltage in real time;

[0127] If the real-time value of the AC side terminal voltage is higher than the low voltage ride-through threshold, fault recovery is performed, and the integral coefficient of the voltage outer loop controller is switched to the first integral coefficient.

[0128] In one embodiment, when the processor executes the computer readable instructions, it further performs the following steps:

[0129] Obtain the external power delivered by the flexible DC converter station within a preset time period before triggering low voltage ride-through;

[0130] Calculating an average value of the external power transmitted by the flexible DC converter station within the preset time period;

[0131] The average value is determined as the active power command value during the fault period.

[0132] In one embodiment, when the processor executes the computer readable instructions, it further performs the following steps:

[0133] regularly obtaining the external power transmission of the flexible DC converter station;

[0134] The second integral coefficient is dynamically adjusted according to the real-time value of the external power transmitted by the flexible DC converter station.

[0135] In one embodiment, when the processor executes the computer readable instructions, it further performs the following steps:

[0136] Calculating a second proportional coefficient during a fault period according to the first integral coefficient, the second integral coefficient, and a first proportional coefficient of a voltage outer loop controller before a fault;

[0137] The proportional coefficient of the voltage outer loop controller is switched from the first proportional coefficient to the second proportional coefficient until it is switched back to the first proportional coefficient when fault recovery is performed.

[0138] In one embodiment, a computer device is provided. The computer device may be a terminal, and its internal structure diagram may be as shown in FIG7 . The computer device includes a processor, memory, a communication interface, a display screen, and an input device connected via a system bus. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of the operating system and computer program in the non-volatile storage medium. The communication interface of the computer device is used to communicate with an external terminal via wired or wireless communication. The wireless communication may be achieved via Wi-Fi, a mobile cellular network, NFC (near-field communication), or other technologies. When executed by the processor, the computer program implements a flexible DC fault ride-through control method. The display screen of the computer device may be a liquid crystal display or an electronic ink display. The input device of the computer device may be a touch screen covering the display screen, or may be buttons, a trackball, or a touchpad provided on the computer device housing, or may be an external keyboard, touchpad, or mouse.

[0139] Those skilled in the art will understand that the structure shown in FIG7 is merely a block diagram of a portion of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than shown in the figure, or combine certain components, or have a different arrangement of components.

[0140] Those skilled in the art will appreciate that all or part of the processes in the above-mentioned embodiment methods can be implemented by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, database or other media used in the embodiments provided in this application may include at least one of non-volatile and volatile memory. Non-volatile memory may include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory may include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM). The database involved in the various embodiments provided herein may include at least one of a relational database and a non-relational database. Non-relational databases may include, but are not limited to, distributed databases based on blockchains. The processor involved in the various embodiments provided herein may be, but are not limited to, a general-purpose processor, a central processing unit, a graphics processing unit, a digital signal processor, a programmable logic unit, a data processing logic unit based on quantum computing, and the like.

[0141] Finally, it should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article, or device comprising the element.

[0142] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of such features. Throughout the description of this application, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0143] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The various embodiments can be combined as needed, and the same or similar parts can be referenced to each other.

[0144] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present application. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A flexible DC fault ride-through control method, characterized in that: Applied to a flexible DC converter station in a pure new energy transmission system via a flexible DC island, the method comprises: Acquiring the AC side terminal voltage of the converter valve and the external power transmission of the flexible DC converter station; If the AC side terminal voltage is less than the low voltage ride-through threshold, the low voltage ride-through is triggered to obtain the active power command value during the fault period; Determining a second integral coefficient during a fault period according to a difference between the active power command value and the external power; Switching the integral coefficient of the voltage outer loop controller from the first integral coefficient before the fault to the second integral coefficient; wherein the first integral coefficient is greater than the second integral coefficient, and the difference between the active power command value during the fault and the external power is negatively correlated with the second integral coefficient; Obtain AC side terminal voltage in real time; If the real-time value of the AC side terminal voltage is higher than the low voltage ride-through threshold, fault recovery is performed and the integral coefficient of the voltage outer loop controller is switched to the first integral coefficient.

2. The flexible DC fault ride-through control method according to claim 1, characterized in that: The obtaining of the active power command value during the fault period includes: Obtain the external power delivered by the flexible DC converter station within a preset time period before triggering low voltage ride-through; Calculating an average value of the external power transmitted by the flexible DC converter station within the preset time period; The average value is determined as the active power command value during the fault period.

3. The flexible DC fault ride-through control method according to claim 2, characterized in that: The preset duration is greater than or equal to 60 seconds.

4. The flexible DC fault ride-through control method according to claim 1, characterized in that: During the low voltage ride-through, the method further comprises: Regularly obtaining the external power transmission of the flexible DC converter station; The second integral coefficient is dynamically adjusted according to the real-time value of the external power transmitted by the flexible DC converter station.

5. The flexible DC fault ride-through control method according to any one of claims 1 to 4, characterized in that: During the low voltage ride-through period, after determining the second integral coefficient according to the difference between the active power command value and the external power, the method further includes: Calculating a second proportional coefficient during a fault period according to the first integral coefficient, the second integral coefficient, and a first proportional coefficient of a voltage outer loop controller before a fault; The proportional coefficient of the voltage outer loop controller is switched from the first proportional coefficient to the second proportional coefficient, and then switched back to the first proportional coefficient when fault recovery is performed.

6. A flexible DC fault ride-through control device, characterized in that: The device is applied to a flexible DC converter station in a pure new energy transmission system via a flexible DC island, and comprises: A first acquisition module is used to acquire the AC side terminal voltage of the converter valve and the external power transmission of the flexible DC converter station; A low voltage ride-through module, used to initiate a low voltage ride-through when the voltage at the AC side terminal is less than a low voltage ride-through threshold, and obtain an active power command value during the fault period; A first determination module, configured to determine a second integral coefficient during a fault period according to a difference between the active power command value and the external power; The first switching module is used to change the integral coefficient of the voltage outer loop controller from the first integral coefficient before the fault to the The integral coefficient is switched to the second integral coefficient; wherein the first integral coefficient is greater than the second integral coefficient, and the difference between the active power command value during the fault period and the external power is negatively correlated with the second integral coefficient; The second acquisition module is used to obtain the AC side terminal voltage in real time; A fault recovery module is used to perform fault recovery and switch the integral coefficient of the voltage outer loop controller to the first integral coefficient when the real-time value of the AC side terminal voltage is higher than the low voltage crossing threshold.

7. The flexible DC fault ride-through control device according to claim 6, characterized in that: The low voltage ride-through module comprises: A power acquisition unit, used for acquiring the external power of the flexible DC converter station within a preset time period before triggering low voltage ride-through; A calculation unit, used to calculate an average value of the external power transmitted by the flexible DC converter station within the preset time period; The command value configuration unit is used to determine the average value as the active power command value during the fault period.

8. The flexible DC fault ride-through control device according to claim 6, characterized in that: The device also includes: A power monitoring module, used for periodically acquiring the external power transmitted by the flexible DC converter station during low voltage ride-through; A dynamic adjustment module is used to dynamically adjust the second integral coefficient according to the real-time value of the external power transmitted by the flexible DC converter station during low voltage ride-through.

9. A storage medium, characterized in that: The storage medium stores computer-readable instructions, and when the computer-readable instructions are executed by one or more processors, the one or more processors execute the steps of the flexible DC fault ride-through control method as described in any one of claims 1 to 5.

10. A computer device, characterized in that: include: one or more processors, and memory; The memory stores computer-readable instructions, and when the one or more processors execute the computer-readable instructions, the steps of the flexible DC fault ride-through control method according to any one of claims 1 to 5 are performed.

Images