A black start control method of a flexible direct current power transmission system and related device

Abstract

The application discloses a black-start control method and related device of a flexible direct-current power transmission system. The method comprises the following steps: before the flexible direct-current power transmission system is unlocked in a black-start operation mode, adjusting a tapping switch gear of a preset converter transformer from 0 gear to n gear, wherein n>0, and the preset converter transformer is a converter transformer connected to a converter of a passive system side of the flexible direct-current power transmission system; determining the voltage and current of the passive system on dq axes; generating a current reference value according to the voltage; and generating a pulse trigger signal in a black-start process by comprehensively considering the voltage, the current and the current reference value. The risk of tripping caused by the overloading protection of the neutral point resistance due to the saturation of the converter transformer is reduced.

Description

Technical Field

[0001] This application relates to the field of flexible DC transmission, and in particular to a black start control method and related apparatus for a flexible DC transmission system. Background Technology

[0002] The converter transformer is one of the key pieces of equipment in a high-voltage direct current (HVDC) transmission system. Located at the core of the AC-DC conversion process, it is a crucial link connecting the power grid and the converter valves. The operating characteristics of the converter transformer, particularly its saturation characteristics, affect the operation of the HVDC transmission system and even the power grid.

[0003] Black start is an important recovery measure for power grids after major disasters and large-scale power outages. Flexible DC can quickly and independently control active and reactive power without relying on grid commutation. In the application of black start in power grids, it has incomparable advantages over traditional high-voltage DC based on thyristors. It can realize the supply of power to remote passive islanded power grids and help the power grid recover quickly.

[0004] For example Figure 1 In the flexible DC transmission system shown, during the black start-up process, magnetic flux is generated when the AC voltage on the converter transformer valve side rises. When the voltage rises to a certain level, according to the saturation characteristics of the converter transformer, distorted excitation current and harmonic components may be generated. As the voltage further increases, the saturation of the converter transformer will be aggravated. Especially for converter transformers with star connection and neutral point grounded through a resistor, excessive harmonics will cause the neutral point resistor overload protection to activate, thereby causing DC tripping and blocking. Summary of the Invention

[0005] In view of this, this application provides a black start control method and related device for a flexible DC transmission system, which takes into account the saturation characteristics of the converter transformer and reduces the risk of neutral point resistance overload protection tripping caused by converter transformer saturation.

[0006] The first aspect of this application provides a black-start control method for a flexible DC transmission system, comprising:

[0007] Before unlocking the black start operation mode of the flexible DC transmission system, the tap position of the preset converter transformer is adjusted from 0 to n, where n > 0. The preset converter transformer is the converter transformer connected to the converter on the passive system side of the flexible DC transmission system.

[0008] Determine the voltage and current of the passive system along the dq axis;

[0009] A current reference value is generated based on the voltage;

[0010] By combining the voltage, the current, and the current reference value, a pulse trigger signal is generated during the black start process.

[0011] Optionally, determining the voltage and current of the passive system on the dq axis specifically includes:

[0012] Collect the three-phase voltage and three-phase current on the passive system side;

[0013] The three-phase voltages are subjected to Parker transformation to obtain the passive system voltages Ud and Uq on the dq axis;

[0014] The three-phase currents are subjected to Parker transformation to obtain the currents Id and Iq of the passive system on the dq axis.

[0015] Optionally, a current reference value is generated based on the voltage, specifically including:

[0016] Based on the outer loop fixed frequency controller, the voltage Uq is subjected to proportional and integral control to obtain the current reference value iqref;

[0017] Based on the outer loop constant AC voltage amplitude controller, the voltage Ud is proportionally controlled to obtain the current reference value idref.

[0018] Optionally, by combining the voltage, the current, and the current reference value, a pulse trigger signal is generated during the black start process, specifically including:

[0019] Using the inner loop controller, the voltages Ud and Uq, the currents Id and Iq, and the current reference values ​​idref and iqref are combined to generate the voltage reference values ​​Udref and Uqref for the dq axis;

[0020] The voltage reference values ​​Udref and Uqref are subjected to inverse Park transform to generate the modulation wave reference value of the control valve side voltage and the pulse trigger signal during the black start process.

[0021] Optionally, based on the outer-loop constant AC voltage amplitude controller, the voltage Ud is proportionally controlled to obtain the current reference value idref, specifically including:

[0022] The voltage reference value Udref is converted into the actual voltage reference value through the n-position tap switch.

[0023] The actual voltage reference value is input to the outer loop constant AC voltage amplitude controller;

[0024] Using the outer-loop constant AC voltage amplitude controller, the voltage Ud is proportionally controlled to obtain the current reference value idref.

[0025] Optionally, based on the outer-loop constant AC voltage amplitude controller, the voltage Ud is proportionally controlled to obtain the current reference value idref, and the method further includes:

[0026] The output terminal of the climb rate limiter is connected to the outer loop constant AC voltage amplitude controller, wherein the input terminal of the climb rate limiter is used to input the three-phase voltage of the passive system side.

[0027] A second aspect of this application provides a black-start control device for a flexible DC transmission system, comprising:

[0028] The adjustment unit is used to adjust the tap position of the preset converter transformer from 0 to n before the black start operation mode of the flexible DC transmission system is unlocked, where n>0. The preset converter transformer is the converter transformer connected to the converter on the passive system side of the flexible DC transmission system.

[0029] A determining unit is used to determine the voltage and current of the passive system on the dq axis;

[0030] The first generating unit is used to generate a current reference value based on the voltage;

[0031] The second generation unit is used to combine the voltage, the current and the current reference value to generate a pulse trigger signal during the black start process.

[0032] Optionally, the determining unit specifically includes:

[0033] The acquisition subunit is used to acquire the three-phase voltage and three-phase current of the passive system.

[0034] The first transformation subunit is used to perform Park transformation on the three-phase voltages to obtain the voltages Ud and Uq of the passive system on the dq axis;

[0035] The second transformation subunit is used to perform Park transformation on the three-phase currents to obtain the currents Id and Iq of the passive system on the dq axis.

[0036] Optionally, the first generation unit specifically includes:

[0037] The first generation subunit is used to obtain the current reference value iqref by proportional and integral control of the voltage Uq based on the outer loop fixed frequency controller;

[0038] The second generation subunit is used to obtain the current reference value idref by proportionally controlling the voltage Ud based on the outer loop constant AC voltage amplitude controller.

[0039] Optionally, the second generation unit specifically includes:

[0040] The third generation subunit is used to generate voltage reference values ​​Udref and Uqref on the dq axis by combining the voltages Ud and Uq, the currents Id and Iq, and the current reference values ​​idref and iqref using the inner loop controller.

[0041] The fourth generation subunit is used to perform an inverse Parker transformation on the voltage reference values ​​Udref and Uqref to generate a modulation wave reference value for the control valve side voltage and a pulse trigger signal during the black start process.

[0042] A third aspect of this application provides a black-start control device for a flexible DC transmission system, including a processor and a memory;

[0043] The memory is used to store program code and transmit the program code to the processor;

[0044] The processor is used to execute any of the black-start control methods for the flexible DC transmission system described in the first aspect according to the instructions in the program code.

[0045] A fourth aspect of this application provides a storage medium for storing program code for executing any of the black-start control methods for the flexible DC transmission system described in the first aspect.

[0046] As can be seen from the above technical solutions, this application has the following advantages:

[0047] The black-start control method for the flexible DC transmission system in this application includes: before unlocking the black-start operation mode of the flexible DC transmission system, adjusting the tap position of the preset converter transformer from 0 to n, where n > 0, and the preset converter transformer is the converter transformer connected to the converter on the passive system side of the flexible DC transmission system; determining the voltage and current of the passive system on the dq axis; generating a current reference value based on the voltage; and generating a pulse trigger signal during the black-start process by combining the voltage, current, and current reference value.

[0048] After studying the existing technology, the applicant found that the default tap position of the converter transformer in the existing DC transmission system is 0. When the tap position is 0, the valve side voltage is high, which can easily cause the converter transformer to saturate. Therefore, this application takes into account the tripping risk caused by the saturation characteristics of the converter transformer. Before unlocking the black start operation mode of the flexible DC transmission system, the tap position of the converter transformer is fixed to a position greater than 0. The higher the tap position, the lower the valve side voltage, and the smaller the risk of converter transformer saturation. This reduces the risk of the neutral point resistance overload protection tripping due to converter transformer saturation. Attached Figure Description

[0049] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0050] Figure 1 This is a schematic diagram of the structure of a flexible DC transmission system;

[0051] Figure 2 This is a flowchart illustrating a first embodiment of a black-start control method for a flexible DC transmission system according to this application.

[0052] Figure 3 This is a flowchart illustrating a second embodiment of a black-start control method for a flexible DC transmission system according to this application.

[0053] Figure 4 This is a schematic diagram of the voltage calculation of the passive system on the dq axis in the flexible DC transmission system of this application embodiment;

[0054] Figure 5 This is a schematic diagram of the current calculation of the passive system on the dq axis in the flexible DC transmission system of this application embodiment;

[0055] Figure 6 This is a schematic diagram of the outer loop constant frequency control of the DC transmission system in the embodiments of this application;

[0056] Figure 7 This is a schematic diagram of the control of the outer loop constant AC voltage amplitude of the DC transmission system in the embodiments of this application;

[0057] Figure 8 This is a schematic diagram of the inner loop controller in an embodiment of this application;

[0058] Figure 9 This is a schematic diagram of the black start control device of a flexible DC transmission system according to an embodiment of this application. Detailed Implementation

[0059] This application provides a black start control method and related device for a flexible DC transmission system, which takes into account the saturation characteristics of the converter transformer and reduces the risk of neutral point resistance overload protection tripping caused by converter transformer saturation.

[0060] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0061] The first aspect of this application provides an embodiment of a black-start control method for a flexible DC transmission system.

[0062] Please see Figure 2 The following is a flowchart illustrating an embodiment of a black-start control method for a flexible DC transmission system in this application.

[0063] The black-start control method for the flexible DC transmission system in this embodiment includes:

[0064] Step 201: Before unlocking the black start operation mode of the flexible DC transmission system, adjust the tap position of the preset converter transformer from 0 to n, where n > 0. The preset converter transformer is the converter transformer connected to the converter on the passive system side of the flexible DC transmission system.

[0065] After studying the existing technology, the applicant found that the default tap position of the converter transformer in the existing DC transmission system is 0. When the tap position is 0, the valve side voltage is high, which can easily cause the converter transformer to saturate. Therefore, this application takes into account the tripping risk caused by the saturation characteristics of the converter transformer. Before unlocking the black start operation mode of the flexible DC transmission system, the tap position of the converter transformer is fixed to a position greater than 0. The higher the tap position, the lower the valve side voltage, and the smaller the risk of converter transformer saturation. This reduces the risk of the neutral point resistance overload protection tripping due to converter transformer saturation.

[0066] Understandably, before adjusting the tap position of the preset converter transformer, the flexible DC transmission system needs to be adjusted to the ready-to-unlock state through operations such as opening and closing interlocks.

[0067] Step 202: Determine the voltage and current of the passive system on the dq axis.

[0068] Understandably, before unlocking the black start operation mode of the flexible DC transmission system, the tap position of the preset converter transformer is adjusted from 0 to n to determine the voltage and current of the passive system on the dq axis.

[0069] Step 203: Generate a current reference value based on the voltage.

[0070] Understandably, after determining the voltage and current of the passive system along the dq axis, the current reference value is generated based on the voltage determined in step 202.

[0071] Step 204: Combine voltage, current and current reference values ​​to generate a pulse trigger signal during the black start process.

[0072] In this embodiment, before unlocking the black-start operation mode of the flexible DC transmission system, the tap position of the preset converter transformer is adjusted from 0 to n, where n > 0. The preset converter transformer is the converter transformer connected to the converter on the passive system side of the flexible DC transmission system. Next, the voltage and current of the passive system on the dq axis are determined. Then, a current reference value is generated based on the voltage. Finally, the voltage, current, and current reference value are combined to generate a pulse trigger signal during the black-start process. That is, this embodiment considers the tripping risk caused by the converter transformer's saturation characteristics. Before unlocking the black-start operation mode of the flexible DC transmission system, the tap position of the converter transformer is fixed to a position greater than 0. The higher the position, the lower the valve-side voltage, and the smaller the risk of converter transformer saturation, thus reducing the risk of neutral point resistance overload protection tripping due to converter transformer saturation.

[0073] The above is Embodiment 1 of a black-start control method for a flexible DC transmission system provided in this application. The following is Embodiment 2 of a black-start control method for a flexible DC transmission system provided in this application.

[0074] The first aspect of this application provides an embodiment of a black-start control method for a flexible DC transmission system.

[0075] Please see Figure 3 The following is a flowchart illustrating an embodiment of a black-start control method for a flexible DC transmission system in this application.

[0076] The black-start control method for the flexible DC transmission system in this embodiment includes:

[0077] Step 301: Before unlocking the black start operation mode of the flexible DC transmission system, adjust the tap position of the preset converter transformer from 0 to n, where n > 0. The preset converter transformer is the converter transformer connected to the converter on the passive system side of the flexible DC transmission system.

[0078] It is understood that the descriptions of steps 301 and 201 are the same, and the details can be found in the description of step 201, which will not be repeated here.

[0079] Step 302: Collect the three-phase voltage and three-phase current on the passive system side.

[0080] Since black starters connect to unloaded converter transformers, lines, or loads of a certain capacity, and there is no additional synchronous power supply to provide a synchronous rotation angle, the given frequency and phase-locked angle θ can be used as the phase-locked angle for the Parker transformation. That is, by acquiring the three-phase voltage Ug and three-phase current Ig of the passive system, a Parker transformation is performed to obtain the dq-axis voltages Ud and Uq, and the currents Id and Iq, respectively.

[0081] Step 303: Perform Parker transformation on the three-phase voltages to obtain the passive system voltages Ud and Uq on the dq axis.

[0082] Specifically, such as Figure 4 The diagram shows the voltage calculation process of the passive system on the dq axis in the flexible DC transmission system of this embodiment. At a given frequency and phase-locked angle θ, the collected three-phase voltages Ug (including Uga, Ugb and Ugc) are transformed by Parker transformation to produce voltages Ud and Uq.

[0083] Step 304: Perform Parker transformation on the three-phase currents to obtain the passive system currents Id and Iq on the dq axis.

[0084] Specifically, such as Figure 5 The diagram shows the current calculation process of the passive system on the dq axis in the flexible DC transmission system in this embodiment. At a given frequency and phase-locked angle θ, the collected three-phase currents Ig (including Iga, Igb and Igc) are subjected to Park transformation to obtain the currents Id and Iq.

[0085] Step 305: Based on the outer loop fixed frequency controller, the voltage Uq is processed by proportional and integral control to obtain the current reference value iqref.

[0086] Specifically, such as Figure 6 The diagram shows the structure of the outer loop fixed frequency controller. Given a q-axis control reference value of 0, the voltage Uq is passed through a proportional and integral control loop to generate a q-axis current reference value iqref.

[0087] Step 306: Based on the outer loop constant AC voltage amplitude controller, the voltage Ud is proportionally controlled to obtain the current reference value idref.

[0088] Specifically, such as Figure 7 The diagram shows the structure of the outer loop constant AC voltage amplitude controller, which obtains the current reference value idref by proportionally controlling the voltage Ud.

[0089] Understandable, Figure 7 The outer loop constant AC voltage amplitude controller in the middle considers raising the tap changer position. Based on the traditional constant AC voltage amplitude control, the voltage reference value is converted into the actual controlled voltage reference value (i.e., the actual voltage reference value) through the set tap changer position.

[0090] When the tap position of the converter transformer is set to n, and the adjustable voltage percentage for each position is x, then the actual relationship between the valve-side AC voltage and the grid-side voltage is as follows:

[0091] Uv = Ug / (1+nx);

[0092] In the formula, Uv is the actual voltage reference value.

[0093] In addition, to prevent the voltage reference value from rising too quickly, causing rapid changes in magnetic flux and slow decay of residual magnetism and DC bias, which could lead to excessive inrush current, a ramp rate limiter was added to the three-phase voltage input on the passive system side to achieve slow AC voltage rise control.

[0094] Therefore, step 306 specifically includes:

[0095] The voltage reference value Udref is converted into the actual voltage reference value through the n-position tap changer;

[0096] Input the actual voltage reference value to the outer loop constant AC voltage amplitude controller;

[0097] Connect the output of the climb rate limiter to the outer loop constant AC voltage amplitude controller, wherein the input of the climb rate limiter is used to input the three-phase voltage on the passive system side;

[0098] Using an outer-loop fixed AC voltage amplitude controller, the voltage Ud is proportionally controlled to obtain the current reference value idref.

[0099] Step 307: Using the inner loop controller, combine the voltages Ud and Uq, the currents Id and Iq, and the current reference values ​​idref and iqref to generate the voltage reference values ​​Udref and Uqref for the dq axis.

[0100] Step 308: Perform an inverse Parker transformation on the voltage reference values ​​Udref and Uqref to generate the modulation wave reference value of the control valve side voltage and the pulse trigger signal during the black start process.

[0101] The dq-axis current reference values ​​Idref and Iqref obtained from the outer loop controller above are processed as follows: Figure 8 The inner loop controller shown generates voltage reference values ​​Udref and Uqref for the dq axis. Finally, after passing through the dq axis Parker inverse transformation stage, it generates a modulated wave reference value for the control valve side voltage and provides it to the next stage converter valve control to generate a pulse trigger signal.

[0102] In this embodiment, before unlocking the black-start operation mode of the flexible DC transmission system, the tap position of the preset converter transformer is adjusted from 0 to n, where n > 0. The preset converter transformer is the converter transformer connected to the converter on the passive system side of the flexible DC transmission system. Next, the voltage and current of the passive system on the dq axis are determined. Then, a current reference value is generated based on the voltage. Finally, the voltage, current, and current reference value are combined to generate a pulse trigger signal during the black-start process. That is, this embodiment considers the tripping risk caused by the converter transformer's saturation characteristics. Before unlocking the black-start operation mode of the flexible DC transmission system, the tap position of the converter transformer is fixed to a position greater than 0. The higher the position, the lower the valve-side voltage, and the smaller the risk of converter transformer saturation, thus reducing the risk of neutral point resistance overload protection tripping due to converter transformer saturation.

[0103] The second aspect of this application provides an embodiment of a black-start control device for a flexible DC transmission system.

[0104] Please see Figure 9 This application provides a schematic diagram of the structure of a black start control device for a flexible DC transmission system.

[0105] A black-start control device for a flexible DC transmission system in this embodiment includes:

[0106] The adjustment unit is used to adjust the tap position of the preset converter transformer from 0 to n before the black start operation mode of the flexible DC transmission system is unlocked, where n>0, and the preset converter transformer is the converter transformer connected to the converter on the passive system side of the flexible DC transmission system.

[0107] A determination unit is used to determine the voltage and current of the passive system along the dq axis;

[0108] The first generation unit is used to generate a current reference value based on the voltage;

[0109] The second generation unit is used to synthesize voltage, current, and current reference values ​​to generate a pulse trigger signal during the black start process.

[0110] Optionally, determining the unit specifically includes:

[0111] The acquisition subunit is used to acquire the three-phase voltage and three-phase current on the passive system side;

[0112] The first transformation subunit is used to perform Park transformation on the three-phase voltages to obtain the passive system voltages Ud and Uq on the dq axis;

[0113] The second transformation subunit is used to perform Park transformation on the three-phase currents to obtain the passive system currents Id and Iq on the dq axis.

[0114] Optionally, the first generating unit specifically includes:

[0115] The first generation subunit is used to obtain the current reference value iqref by proportional and integral control of the voltage Uq based on the outer loop fixed frequency controller;

[0116] The second generation subunit is used to obtain the current reference value idref by proportionally controlling the voltage Ud based on the outer loop constant AC voltage amplitude controller.

[0117] Optionally, the second generation unit specifically includes:

[0118] The third generation subunit is used to generate the voltage reference values ​​Udref and Uqref of the dq axis by combining the voltages Ud and Uq, the currents Id and Iq, and the current reference values ​​idref and iqref using the inner loop controller.

[0119] The fourth generation subunit is used to perform an inverse Parker transformation on the voltage reference values ​​Udref and Uqref to generate the modulation wave reference value of the control valve side voltage and the pulse trigger signal during the black start process.

[0120] Optionally, based on the outer-loop fixed AC voltage amplitude controller, the voltage Ud is proportionally controlled to obtain the current reference value idref, specifically including:

[0121] The voltage reference value Udref is converted into the actual voltage reference value through the n-position tap changer;

[0122] Input the actual voltage reference value to the outer loop constant AC voltage amplitude controller;

[0123] Using an outer-loop fixed AC voltage amplitude controller, the voltage Ud is proportionally controlled to obtain the current reference value idref.

[0124] Optionally, based on the outer-loop fixed AC voltage amplitude controller, the voltage Ud is proportionally controlled to obtain the current reference value idref, and the system further includes:

[0125] Connect the output of the climb rate limiter to the outer loop constant AC voltage amplitude controller, wherein the input of the climb rate limiter is used to input the three-phase voltage on the passive system side.

[0126] In this embodiment, before unlocking the black-start operation mode of the flexible DC transmission system, the tap position of the preset converter transformer is adjusted from 0 to n, where n > 0. The preset converter transformer is the converter transformer connected to the converter on the passive system side of the flexible DC transmission system. Next, the voltage and current of the passive system on the dq axis are determined. Then, a current reference value is generated based on the voltage. Finally, the voltage, current, and current reference value are combined to generate a pulse trigger signal during the black-start process. That is, this embodiment considers the tripping risk caused by the converter transformer's saturation characteristics. Before unlocking the black-start operation mode of the flexible DC transmission system, the tap position of the converter transformer is fixed to a position greater than 0. The higher the position, the lower the valve-side voltage, and the smaller the risk of converter transformer saturation, thus reducing the risk of neutral point resistance overload protection tripping due to converter transformer saturation.

[0127] The third aspect of this application provides an embodiment of a black start control device for a flexible DC transmission system.

[0128] A black-start control device for a flexible DC transmission system includes a processor and a memory; the memory is used to store program code and transmit the program code to the processor; the processor is used to execute the black-start control method for the flexible DC transmission system according to the instructions in the program code.

[0129] The fourth aspect of this application provides an embodiment of a storage medium.

[0130] A storage medium for storing program code for executing a black-start control method for a flexible DC transmission system, as described in the first aspect.

[0131] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the above-described apparatus and unit can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0132] In the several embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another power grid network to be installed, or some features may be ignored or not executed. Furthermore, the mutual coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0133] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0134] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0135] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0136] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A black-start control method of a flexible direct current power transmission system, characterized by, The application relates to a method for controlling a black start operation mode of a flexible direct-current power transmission system. Before the black start operation mode of the flexible direct-current power transmission system is unlocked, the tap switch gear of a preset converter transformer is adjusted from 0 to n, wherein n>0, and the preset converter transformer is a converter transformer connected to a converter of a passive system side of the flexible direct-current power transmission system; The voltage and current of the passive system on the dq axis are determined, and the voltage and current of the passive system on the dq axis include voltage Ud, voltage Uq, current Id and current Iq; The voltage Uq is subjected to proportional and integral control based on an outer ring fixed-frequency controller to obtain a current reference value iqref; The output end of a climb rate limiter is connected to an outer ring fixed AC voltage amplitude controller, wherein the input end of the climb rate limiter is used for inputting three-phase voltage of the passive system side; The three-phase voltage of the passive system side is converted into an actual voltage reference value through the n-gear tap switch gear, and the conversion formula is as follows: Uv=Ug / (1+nx); In the formula, Uv is the actual voltage reference value, x is the percentage of adjustable voltage of each gear, and Ug is the three-phase voltage of the passive system; The actual voltage reference value is input to the outer ring fixed AC voltage amplitude controller; The voltage Ud is subjected to proportional control by the outer ring fixed AC voltage amplitude controller to obtain a current reference value idref; An inner ring controller is used to comprehensively generate voltage reference values Udref and Uqref of the dq axis by comprehensively considering the voltage Ud, the voltage Uq, the current Id, the current Iq, the current reference value idref and the current reference value iqref; The voltage reference values Udref and Uqref are subjected to inverse Park transformation to generate a modulation wave reference value for controlling the valve side voltage and a pulse trigger signal in the black start process.

2. The black-start control method of a flexible DC power transmission system according to claim 1, characterized by, The voltage and current of the passive system on the dq axis are determined, and the voltage and current of the passive system on the dq axis include voltage Ud, voltage Uq, current Id and current Iq. The three-phase voltage and three-phase current of the passive system side are collected; The three-phase voltage is subjected to Park transformation to obtain the voltage Ud and Uq of the passive system on the dq axis; The three-phase current is subjected to Park transformation to obtain the current Id and Iq of the passive system on the dq axis.

3. A black start control device for a flexible HVDC power transmission system, characterized in that The application relates to a method for controlling a black start operation mode of a flexible direct-current power transmission system. Before the black start operation mode of the flexible direct-current power transmission system is unlocked, the tap switch gear of a preset converter transformer is adjusted from 0 to n, wherein n>0, and the preset converter transformer is a converter transformer connected to a converter of a passive system side of the flexible direct-current power transmission system; The voltage and current of the passive system on the dq axis are determined, and the voltage and current of the passive system on the dq axis include voltage Ud, voltage Uq, current Id and current Iq; A first generation unit is used for obtaining a current reference value iqref by subjecting the voltage Uq to proportional and integral control based on an outer ring fixed-frequency controller, and is used for connecting the output end of a climb rate limiter to an outer ring fixed AC voltage amplitude controller, wherein the input end of the climb rate limiter is used for inputting three-phase voltage of the passive system side; and is used for converting the three-phase voltage of the passive system side into an actual voltage reference value through the n-gear tap switch gear, and the conversion formula is as follows: ​ In the formula, Uv is an actual voltage reference value, x is a percentage of adjustable voltage amount of each gear, Ug is a three-phase voltage of a passive system side; and used for inputting the actual voltage reference value to the outer ring AC voltage amplitude controller; and used for using the outer ring AC voltage amplitude controller to perform proportional control on the voltage Ud to obtain a current reference value idref; A second generation unit is configured to use an inner ring controller to synthesize the voltage Ud, the voltage Uq, the current Id and the current Iq, the current reference value idref and the current reference value iqref to generate voltage reference values Udref and Uqref of dq axes; and to perform inverse Park transformation on the voltage reference values Udref and Uqref to generate a modulation wave reference value of a control valve side voltage and a pulse trigger signal in a black start process.

4. The black-start control device of a flexible HVDC power transmission system according to claim 3, characterized by, The determination unit specifically comprises: A collection subunit is configured to collect three-phase voltages and three-phase currents of the passive system side; A first transformation subunit is configured to perform Park transformation on the three-phase voltages to obtain the voltage Ud and the voltage Uq of the passive system in dq axes; A second transformation subunit is configured to perform Park transformation on the three-phase currents to obtain the current Id and the current Iq of the passive system in dq axes.

5. A black start control device for a flexible HVDC power transmission system, characterized in that The processor and the memory are included; The memory is configured to store program code and transmit the program code to the processor; The processor is configured to execute the black start control method of the flexible HVDC power transmission system according to instructions in the program code.

6. A storage medium, characterized by The storage medium is configured to store program code, and the program code is configured to execute the black start control method of the flexible HVDC power transmission system. The storage medium is configured to store program code, and the program code is configured to execute the black start control method of the flexible HVDC power transmission system.

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