A DC voltage synchronization control method for ultra-high voltage flexible DC multi-valve groups

Abstract

This application discloses a DC voltage synchronization control method for an ultra-high voltage flexible DC multi-valve group. The method identifies each valve group within the ultra-high voltage flexible DC multi-valve group; each valve group is controlled independently, including an AC voltage modulation coefficient generation stage (generating AC voltage modulation coefficients based on reactive power control targets); a phase angle generation stage (generating phase angles based on submodule energy synchronization control); a DC voltage modulation coefficient generation stage (generating DC voltage modulation coefficients based on DC voltage control targets); and a modulation reference voltage calculation stage (calculating the modulation reference voltage for each arm of the valve group based on AC voltage modulation coefficients, DC voltage modulation coefficients, and phase angles). The method determines the number of modules connected in series within the ultra-high voltage flexible DC multi-valve group, multiplies this number by the modulation reference voltage, and obtains the number of submodules in operation, thereby achieving synchronization control based on the number of submodules in operation. This application enables coordinated operation of the same AC bus voltage on the AC side controlled by multiple valve groups, eliminating the need for real-time communication between valve groups and significantly improving the stability of the ultra-high voltage flexible DC multi-valve group system.

Description

Technical Field

[0001] This application relates to the field of DC voltage synchronization control technology, specifically to a DC voltage synchronization control method for an ultra-high voltage flexible DC multi-valve group. Background Technology

[0002] Under the construction of new power systems, ultra-high voltage flexible direct current (UHVDC) transmission is an important carrier for feeding clean energy power to load centers over long distances. A typical structure involves the sending-end flexible direct current converter station connecting to the receiving-end flexible direct current converter station via a long-distance overhead line. In current engineering designs, the receiving-end converter station uses grid-following control based on phase-locked loops (PLLs), which lacks inertia and active voltage support capabilities, resulting in poor adaptability to weak grids. With the increasing electronic sophistication and hollowing out of power sources in the receiving-end grid, flexible direct current receiving-end systems need to adopt a grid-based control method based on DC voltage. However, to achieve a multi-valve group grid-based control architecture based on DC voltage, it is necessary to solve the voltage coordination problem of multiple valve groups controlling the same AC bus grid on the AC side, and to possess single-valve group DC voltage control capabilities during valve group activation and deactivation.

[0003] Existing control methods mainly adopt master-slave control to achieve multi-valve group coordination. The master control valve group is responsible for building AC voltage, and the slave control valve group follows. This method relies on rapid communication between valve groups and requires that the valve group operating conditions are basically consistent. The coordination process is complicated during valve group activation and deactivation. Summary of the Invention

[0004] In view of this, this application provides a DC voltage synchronous control method for ultra-high voltage flexible DC multi-valve groups, which solves the problems of existing control methods relying on rapid communication between valve groups, requiring valve group operating conditions to be basically consistent, and having complex coordination processes during valve group activation and deactivation.

[0005] To achieve the above objectives, the following solution is proposed:

[0006] In a first aspect, a method for synchronous control of DC voltage in an ultra-high voltage flexible DC multi-valve group includes:

[0007] Identify the individual valve groups in the UHV flexible DC multi-valve group;

[0008] For each valve group, the phase angle, AC voltage modulation coefficient, and DC side modulation coefficient of the valve group are independently controlled.

[0009] The modulation reference voltage for each arm of the valve group is calculated based on the phase angle, AC voltage modulation coefficient, and DC side modulation coefficient.

[0010] The number of modules connected in series in the UHV flexible DC multi-valve group is determined, and the number of modules connected in series is multiplied by the modulation reference voltage to obtain the number of sub-modules to be engaged, so as to achieve synchronous control according to the number of sub-modules engaged.

[0011] Preferably, the formula for calculating the phase angle is:

[0012] ;

[0013] in, Indicates the phase angle. This represents the actual energy value of the submodule. Indicates the energy reference value of the submodule. This represents the phase angle control proportional coefficient. This represents the phase angle control integral coefficient. As the reference frequency, This represents the Laplace transform operator.

[0014] Preferably, the process of independently controlling the valve group to generate the AC voltage modulation coefficient includes: including:

[0015] For the AC side of the valve group, reactive power proportional and integral closed-loop control is used to generate AC voltage reference values;

[0016] A virtual impedance is added between the valve group and the same grid connection point to calculate the AC voltage modulation coefficient based on the AC voltage reference value.

[0017] Preferably, the method of generating AC voltage reference values ​​using reactive power ratio and integral closed-loop control includes:

[0018] AC voltage reference value The calculation formula is:

[0019] ;

[0020] in, This represents the reference value for reactive power. This represents the actual value of reactive power. This represents the reactive power control proportional coefficient. This represents the integral coefficient for reactive power control. Indicates the reference voltage. This represents the Laplace transform operator.

[0021] Preferably, the step of adding a virtual impedance between the valve group and the same grid connection point to calculate the AC voltage modulation coefficient based on the AC voltage reference value includes:

[0022] Obtain the actual AC voltage value and the AC voltage reference value;

[0023] The AC current reference value is calculated based on the actual AC voltage value and the AC voltage reference value, using the following formula:

[0024] ;

[0025] in, Indicates the reference value of alternating current. This is the AC voltage reference value. Actual value of AC voltage This represents the virtual resistance in the virtual impedance. This represents the virtual inductance in the virtual impedance;

[0026] Obtain the actual value of the AC current, and calculate the AC voltage modulation coefficient based on the actual value of the AC current and the AC current reference value. The calculation formula is as follows:

[0027] ;

[0028] in, Indicates the AC voltage modulation coefficient. This represents the proportional coefficient for AC current control. This represents the integral coefficient for AC current control.

[0029] Preferably, the process of independently controlling the valve group to generate the DC-side modulation coefficient includes:

[0030] Obtain the actual value of the DC side voltage;

[0031] Based on the actual DC-side voltage value and the preset DC-side voltage reference value, the valve group is subjected to DC voltage proportional-integral control to obtain the DC-side modulation coefficient. The calculation formula is:

[0032] ;

[0033] in, Indicates the DC-side voltage reference value. This represents the actual value of the DC-side voltage. This represents the proportional coefficient for DC voltage control. This represents the integral coefficient for DC voltage control. This represents the Laplace transform operator.

[0034] Preferably, the step of calculating the modulation reference voltage of each arm of the valve group based on the phase angle, AC voltage modulation coefficient, and DC-side modulation coefficient includes:

[0035] The phase angle is used as the phase angle reference in the modulation reference voltage calculation process. The formula for calculating the modulation reference voltage is:

[0036] The calculation formula is:

[0037] ;

[0038] in, Indicates the DC-side modulation coefficient. Indicates the AC voltage modulation coefficient. Indicates the modulation reference voltage. and All are weighting coefficients.

[0039] Secondly, a DC voltage synchronization control device for an ultra-high voltage flexible DC multi-valve group includes:

[0040] Valve group determination module, used to determine each valve group in the UHV flexible DC multi-valve group;

[0041] An independent control module is used to independently control the generation of phase angle, AC voltage modulation coefficient, and DC side modulation coefficient for each valve group.

[0042] The modulation reference voltage calculation module is used to calculate the modulation reference voltage of each arm of the valve group based on the phase angle, AC voltage modulation coefficient and DC side modulation coefficient.

[0043] The synchronization control implementation module is used to determine the number of modules connected in series in the UHV flexible DC multi-valve group, multiply the number of modules connected in series with the modulation reference voltage to obtain the number of sub-modules to be engaged, so as to realize synchronization control according to the number of sub-modules to be engaged.

[0044] Thirdly, a DC voltage synchronous control device for an ultra-high voltage flexible DC multi-valve group includes a memory and a processor;

[0045] The memory is used to store programs;

[0046] The processor is configured to execute the program to implement the various steps of the DC voltage synchronization control method for ultra-high voltage flexible DC multi-valve groups as described in any of the first aspects.

[0047] Fourthly, a storage medium storing a computer program thereon, which, when executed by a processor, implements the various steps of the DC voltage synchronization control method for an ultra-high voltage flexible DC multi-valve group as described in any of the first aspects.

[0048] As can be seen from the above technical solution, this application defines each valve group in the UHV flexible DC multi-valve group; for each valve group, it independently controls the generation of phase angle, AC voltage modulation coefficient, and DC-side modulation coefficient; it calculates the modulation reference voltage of each bridge arm of the valve group based on the phase angle, AC voltage modulation coefficient, and DC-side modulation coefficient; it determines the number of modules connected in series in the UHV flexible DC multi-valve group, multiplies the number of modules connected in series with the modulation reference voltage to obtain the number of sub-modules to be engaged, so as to achieve synchronous control based on the number of sub-modules engaged. This application achieves multi-level independent control, including independent control of AC voltage modulation coefficient generation and independent control of DC-side modulation coefficient generation. This is no longer the case of one valve group commanding another valve group in the prior art, but rather allows all valve groups to follow the same goal and independently calculate the waveform to be output. This enables the multi-valve group to coordinate the operation of the same AC bus voltage on the AC side, and does not require real-time communication between valve groups, which can greatly improve the stability of the UHV flexible DC multi-valve group system. Attached Figure Description

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

[0050] Figure 1 A typical wiring diagram of an ultra-high voltage flexible DC converter station is provided for embodiments of this application;

[0051] Figure 2 An optional flowchart of a DC voltage synchronization control method for an ultra-high voltage flexible DC multi-valve group provided in an embodiment of this application;

[0052] Figure 3 A flowchart illustrating a DC voltage synchronization control method for an ultra-high voltage flexible DC multi-valve group provided in this application embodiment;

[0053] Figure 4 A schematic diagram of the structure of a DC voltage synchronization control device for an ultra-high voltage flexible DC multi-valve group provided in this application embodiment;

[0054] Figure 5 This is a schematic diagram of the structure of a DC voltage synchronization control device for an ultra-high voltage flexible DC multi-valve group provided in an embodiment of this application. Detailed Implementation

[0055] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0056] This invention can be used in a wide variety of general-purpose or special-purpose computing environments or configurations. For example: personal computers, server computers, handheld or portable devices, tablet devices, multiprocessor devices, distributed computing environments including any of the above devices, etc.

[0057] Under the construction of new power systems, ultra-high voltage flexible direct current (UHVDC) transmission is an important carrier for feeding clean energy power into load centers over long distances. A typical structure involves a sending-end flexible direct current converter station connected to a receiving-end flexible direct current converter station via a long-distance overhead line. For a two-end flexible direct current transmission system, the sending-end converter station typically uses active and reactive power as control targets, matching the active power command of the flexible direct current with the active power output characteristics of the clean energy source. The receiving-end converter station uses DC voltage and reactive power as control targets to maintain the DC voltage stability of the entire flexible direct current transmission system. In current engineering designs, the receiving-end converter station uses grid-following control based on phase-locked loops, which lacks inertia and active voltage support capabilities, resulting in poor adaptability to weak grids. With the increasing electronicization of the receiving-end grid and the trend of hollowing out power sources, the receiving end of the flexible direct current system needs to adopt a grid-based control method based on DC voltage. A typical wiring diagram of a ±800kV UHVDC converter station at the receiving end is shown below. Figure 1 As shown, a bipolar four-valve group is connected to the same AC bus grid connection point, including pole 1 (high valve, low valve) and pole 2 (high valve, low valve). Each pole has two valve groups connected in series. In order to realize the multi-valve group grid-type control architecture based on DC voltage, it is necessary to solve the voltage coordination problem of the multi-valve group control of the same AC bus grid on the AC side, and to have the DC voltage control capability of a single valve group during valve group commissioning and decommissioning.

[0058] Existing control methods mainly adopt master-slave control to achieve multi-valve group coordination. The master control valve group is responsible for building AC voltage, and the slave control valve group follows. This method relies on rapid communication between valve groups and requires that the valve group operating conditions are basically consistent. The coordination process is complicated during valve group activation and deactivation.

[0059] To address the shortcomings of the existing technology, this invention provides a DC voltage synchronization control method for ultra-high voltage flexible DC multi-valve groups, specifically for controlled DC voltage converter stations. This method can be applied to various computer terminals or smart terminals, and its execution entity can be the processor or server of the computer terminal or smart terminal.

[0060] The flowchart of the method is as follows: Figure 1 As shown, it specifically includes:

[0061] S1: Determine each valve group in the UHV flexible DC multi-valve group.

[0062] This application first identifies each valve group in the UHV flexible DC multi-valve group, so that each valve group can be controlled individually in the subsequent process, the control range can be defined, and modularization can be achieved.

[0063] S2: For each valve group, independently control the generation of phase angle, AC voltage modulation coefficient, and DC side modulation coefficient.

[0064] This application adopts an independent control method for each valve group, including an AC voltage modulation coefficient generation stage on the AC side, a DC modulation coefficient generation stage, a modulation wave (modulation reference voltage) calculation stage, and a phase angle generation stage.

[0065] The AC voltage modulation coefficient generation process on the AC side includes reactive power and integral control, AC voltage virtual admittance control, and AC current closed-loop control.

[0066] Introducing a DC-side modulation coefficient is equivalent to providing each valve group with a DC voltage adapter. This allows each valve group to fine-tune its voltage output proportion in the DC link based on its own capacitor voltage, losses, and other factors. Furthermore, although each valve group generates its own DC modulation coefficient independently, the reference standard for this coefficient is common. Regardless of the valve group, the final generated modulation reference voltage tends to be proportional to the total DC voltage of the system in terms of its DC component.

[0067] If a valve group is in poor operating condition, such as low capacitor voltage, it can automatically reduce its DC-side modulation coefficient and output less voltage, allowing other valve groups in better operating condition to bear more of the load. This kind of self-adaptation is something that the master-slave control method in the current technology cannot achieve.

[0068] In addition, phase angle calculation is the core of achieving synchronous control in this application.

[0069] S3: Calculate the modulation reference voltage for each arm of the valve group based on the phase angle, AC voltage modulation coefficient, and DC side modulation coefficient.

[0070] This step enables the physical coupling calculation of AC and DC. This step synthesizes the AC target and DC target at the modulation wave level, which ensures that the AC waveform and DC waveform output by the valve group correspond and will not cause contradictions due to separate independent control.

[0071] S4: Determine the number of modules connected in series in the UHV flexible DC multi-valve group, multiply the number of modules connected in series with the modulation reference voltage to obtain the number of sub-modules to be engaged, so as to achieve synchronous control according to the number of sub-modules to be engaged.

[0072] This application converts the modulated wave into a specific switching action command through a simple multiplication operation. When all valve groups perform this multiplication based on the same physical quantity, the actions of all valve groups appear to be synchronized macroscopically. Finally, the newly engaged valve group determines its current state after the control calculation in step S2. Since the calculation in step S3 is based on the current DC voltage and independent modulation coefficient, the modulation reference voltage calculated by the new valve group is naturally what the current system needs. This makes the engagement process smooth and shock-free, solving the problem of complex engagement and de-engagement processes in the prior art.

[0073] In other words, the UHV flexible DC multi-valve group adopts a sub-module series structure. For example, if there are N modules in series, the number of modules put into operation is N * the modulation reference voltage.

[0074] It is important to note that the sum of the DC-side modulation coefficients of each valve group must be 1 (or the coefficient corresponding to the total voltage). Since each valve group adjusts its own coefficients independently, as long as the final coefficient distribution is reasonable and all valve groups are calculated based on the same total voltage, their output voltages will naturally be synchronously superimposed.

[0075] As can be seen from the above technical solution, this application defines each valve group in the UHV flexible DC multi-valve group; for each valve group, it independently controls the generation of phase angle, AC voltage modulation coefficient, and DC-side modulation coefficient; it calculates the modulation reference voltage of each bridge arm of the valve group based on the phase angle, AC voltage modulation coefficient, and DC-side modulation coefficient; it determines the number of modules connected in series in the UHV flexible DC multi-valve group, multiplies the number of modules connected in series with the modulation reference voltage to obtain the number of sub-modules to be engaged, so as to achieve synchronous control based on the number of sub-modules engaged. This application achieves multi-level independent control, including independent control of AC voltage modulation coefficient generation and independent control of DC-side modulation coefficient generation. This is no longer the case of one valve group commanding another valve group in the prior art, but rather allows all valve groups to follow the same goal and independently calculate the waveform to be output. This enables the multi-valve group to coordinate the operation of the same AC bus voltage on the AC side, and does not require real-time communication between valve groups, which can greatly improve the stability of the UHV flexible DC multi-valve group system.

[0076] In the method provided by this embodiment of the invention, the formula for calculating the phase angle is:

[0077] ;

[0078] in, Indicates the phase angle. This represents the actual energy value of the submodule. Indicates the energy reference value of the submodule. This represents the phase angle control proportional coefficient. This represents the phase angle control integral coefficient. As the reference frequency, This represents the Laplace transform operator.

[0079] Specifically, the phase angle is the benchmark for calculating AC power. With it, the valve group can correctly convert the static three-phase voltage into a rotating coordinate system component that can be independently controlled for active and non-active power. Therefore, the additional phase angle generation step in this application ensures that the phase of the AC voltage of each valve group can be kept consistent with the power grid or other valve groups when operating independently, thereby avoiding power crosstalk or circulating current problems caused by phase asynchrony.

[0080] The method provided in this embodiment of the invention, which independently controls the valve group to generate the AC voltage modulation coefficient, is described in detail below:

[0081] For the AC side of the valve group, reactive power proportional and integral closed-loop control is used to generate AC voltage reference values;

[0082] A virtual impedance is added between the valve group and the same grid connection point to calculate the AC voltage modulation coefficient based on the AC voltage reference value.

[0083] Specifically, each valve group uses reactive power proportional and integral closed-loop control on the AC side to generate an AC voltage reference value. This avoids the long-term adjustment process of multiple valve groups caused by simultaneous control of AC voltage and can suppress reactive power links between valve groups. A control architecture based on AC voltage virtual admittance + AC current closed loop can be adopted, which can effectively add a virtual impedance between the valve group and the same grid connection point, thereby reducing the coupling between controllers of multiple valve groups.

[0084] The step of generating an AC voltage reference value using reactive power proportional and integral closed-loop control in the above process may include:

[0085] AC voltage reference value The calculation formula is:

[0086] ;

[0087] in, This represents the reference value for reactive power. This represents the actual value of reactive power. This represents the reactive power control proportional coefficient. This represents the integral coefficient for reactive power control. Indicates the reference voltage. This represents the Laplace transform operator.

[0088] Specifically, whether it is a reactive power command issued by the power grid dispatch or a reactive power target set to stabilize the local AC bus voltage, proportional-integral (PI) closed-loop control can ensure that the actual reactive power output by the valve group is exactly equal to the target value. Even if the power grid voltage fluctuates and causes reactive power deviation, the integral link will continue to work until the deviation is completely eliminated. This is crucial for maintaining the voltage stability of the AC system and avoids the risk of overvoltage or undervoltage due to insufficient control accuracy.

[0089] The adoption of local reactive power closed-loop control means that each valve group only cares about the electrical status of its own AC port. If a valve group detects a voltage drop on the AC bus it is connected to, it will automatically increase the reactive power output (by adjusting the AC voltage modulation coefficient) to support the voltage at that point, so that multiple valve groups can achieve decoupling and autonomy on the AC side.

[0090] Specifically, the step of adding a virtual impedance between the valve group and the same grid connection point in the above process to calculate the AC voltage modulation coefficient based on the AC voltage reference value may include:

[0091] Obtain the actual AC voltage value and the AC voltage reference value;

[0092] The AC current reference value is calculated based on the actual AC voltage value and the AC voltage reference value, using the following formula:

[0093] ;

[0094] in, Indicates the reference value of alternating current. This is the AC voltage reference value. Actual value of AC voltage This represents the virtual resistance in the virtual impedance. This represents the virtual inductance in the virtual impedance;

[0095] Obtain the actual value of the AC current, and calculate the AC voltage modulation coefficient based on the actual value of the AC current and the AC current reference value. The calculation formula is as follows:

[0096] ;

[0097] in, Indicates the AC voltage modulation coefficient. This represents the proportional coefficient for AC current control. This represents the integral coefficient for AC current control.

[0098] Specifically, this control method achieves active limitation and protection of AC current, solves the overcurrent risk of converter, and realizes software current limiting in addition to physical hard limiting. It also allows active and reactive power to be controlled independently without interference. By introducing AC current as an intermediate variable, we can use mathematical transformation to decompose AC current into active current component (d-axis current) and reactive current component (q-axis current). Then the valve group can control the AC system as easily as controlling a DC motor.

[0099] The process of independently controlling the valve group to generate the DC-side modulation coefficient in this application is described in detail below.

[0100] Obtain the actual value of the DC side voltage;

[0101] Based on the actual DC-side voltage value and the preset DC-side voltage reference value, the valve group is subjected to DC voltage proportional-integral control to obtain the DC-side modulation coefficient. The calculation formula is:

[0102] ;

[0103] in, Indicates the DC-side voltage reference value. This represents the actual value of the DC-side voltage. This represents the proportional coefficient for DC voltage control. This represents the integral coefficient for DC voltage control. This represents the Laplace transform operator.

[0104] Specifically, in ultra-high voltage direct current (UHVDC) transmission, multiple valve groups are connected in series on the DC side. According to Kirchhoff's voltage law, the total voltage is equal to the sum of the voltages of each valve group. If the capacitance, loss, or control delay of a valve group is slightly different, the voltage it bears may deviate from the ideal value. Therefore, this application introduces PI closed-loop control between the actual DC voltage value and the reference value to ensure that the actual DC voltage value of each valve group is equal to the voltage reference value. Furthermore, at the instant the valve group bypass switch is closed, due to the pre-adjustment effect of the PI controller, the valve group port voltage is already basically equal to the bus voltage, thus avoiding a huge inrush current and achieving smooth connection.

[0105] The following embodiments provide a detailed explanation of the steps in this application for calculating the modulation reference voltage of each arm of the valve group based on the phase angle, AC voltage modulation coefficient, and DC side modulation coefficient.

[0106] The phase angle is used as the phase angle reference in the modulation reference voltage calculation process. The formula for calculating the modulation reference voltage is:

[0107] ;

[0108] in, Indicates the DC-side modulation coefficient. Indicates the AC voltage modulation coefficient. Indicates the modulation reference voltage. and All are weighting coefficients.

[0109] Specifically, the above method solves the contradiction that a single bridge arm must handle both AC current and DC voltage. By using a weighted summation method, the two objectives are combined into a specific, time-varying waveform command, which can meet the AC power grid's requirements for the valve group, such as voltage support and reactive power regulation, as well as the DC system's requirements for the valve group, such as voltage balance and power transmission.

[0110] The overall flowchart of this application is as follows: Figure 3 As shown.

[0111] In one exemplary embodiment, such as Figure 4 As shown, a virtual and real registration device for an equipment is provided, comprising: a valve group determination module 10, an AC voltage modulation coefficient generation module 20, a DC side modulation coefficient generation module 30, a modulation reference voltage calculation module 40, and a synchronization control implementation module 50, wherein:

[0112] Valve group determination module 10 is used to determine each valve group in the UHV flexible DC multi-valve group;

[0113] The AC voltage modulation coefficient generation module 20 is used to independently control the generation of AC voltage modulation coefficients for each valve group.

[0114] DC-side modulation coefficient generation module 30 is used to independently control the valve group to generate DC-side modulation coefficients;

[0115] The modulation reference voltage calculation module 40 is used to calculate the modulation reference voltage of each bridge arm of the valve group based on the AC voltage modulation coefficient and the DC side modulation coefficient.

[0116] Synchronous control implementation module 50 is used to determine the number of modules connected in series in the UHV flexible DC multi-valve group, multiply the number of modules connected in series with the modulation reference voltage to obtain the number of sub-modules to be engaged, so as to realize synchronous control according to the number of sub-modules to be engaged.

[0117] As can be seen from the above technical solution, this application defines each valve group in the UHV flexible DC multi-valve group; for each valve group, it independently controls the generation of phase angle, AC voltage modulation coefficient, and DC-side modulation coefficient; it calculates the modulation reference voltage of each bridge arm of the valve group based on the phase angle, AC voltage modulation coefficient, and DC-side modulation coefficient; it determines the number of modules connected in series in the UHV flexible DC multi-valve group, multiplies the number of modules connected in series with the modulation reference voltage to obtain the number of sub-modules to be engaged, so as to achieve synchronous control based on the number of sub-modules engaged. This application achieves multi-level independent control, including independent control of AC voltage modulation coefficient generation and independent control of DC-side modulation coefficient generation. This is no longer the case of one valve group commanding another valve group in the prior art, but rather allows all valve groups to follow the same goal and independently calculate the waveform to be output. This enables the multi-valve group to coordinate the operation of the same AC bus voltage on the AC side, and does not require real-time communication between valve groups, which can greatly improve the stability of the UHV flexible DC multi-valve group system.

[0118] In one embodiment, the independent control module 20 is used to independently control the generation of the phase angle, including: the phase angle is calculated using the following formula:

[0119] ;

[0120] in, Indicates the phase angle. This represents the actual energy value of the submodule. Indicates the energy reference value of the submodule. This represents the phase angle control proportional coefficient. This represents the phase angle control integral coefficient. As the reference frequency, This represents the Laplace transform operator.

[0121] In one embodiment, the independent control module 20 is used to independently control the process of generating AC voltage modulation coefficients for the valve group, including:

[0122] For the AC side of the valve group, reactive power proportional and integral closed-loop control is used to generate AC voltage reference values;

[0123] A virtual impedance is added between the valve group and the same grid connection point to calculate the AC voltage modulation coefficient based on the AC voltage reference value.

[0124] In one embodiment, the independent control module 20 is used to generate an AC voltage reference value by employing reactive power proportional and integral closed-loop control, including:

[0125] AC voltage reference value The calculation formula is:

[0126] ;

[0127] in, This represents the reference value for reactive power. This represents the actual value of reactive power. This represents the reactive power control proportional coefficient. This represents the integral coefficient for reactive power control. Indicates the reference voltage. This represents the Laplace transform operator.

[0128] In one embodiment, the independent control module 20 is used to add a virtual impedance between the valve group and the same grid connection point to calculate the AC voltage modulation coefficient based on the AC voltage reference value, including:

[0129] Obtain the actual AC voltage value and the AC voltage reference value;

[0130] The AC current reference value is calculated based on the actual AC voltage value and the AC voltage reference value, using the following formula:

[0131] ;

[0132] in, Indicates the reference value of alternating current. This is the AC voltage reference value. Actual value of AC voltage This represents the virtual resistance in the virtual impedance. This represents the virtual inductance in the virtual impedance;

[0133] Obtain the actual value of the AC current, and calculate the AC voltage modulation coefficient based on the actual value of the AC current and the AC current reference value. The calculation formula is as follows:

[0134] ;

[0135] in, Indicates the AC voltage modulation coefficient. This represents the proportional coefficient for AC current control. This represents the integral coefficient for AC current control.

[0136] In one embodiment, the independent control module 20 is used to independently control the process of generating the DC-side modulation coefficient of the valve group, including:

[0137] Obtain the actual value of the DC side voltage;

[0138] Based on the actual DC-side voltage value and the preset DC-side voltage reference value, the valve group is subjected to DC voltage proportional-integral control to obtain the DC-side modulation coefficient. The calculation formula is:

[0139] ;

[0140] in, Indicates the DC-side voltage reference value. This represents the actual value of the DC-side voltage. This represents the proportional coefficient for DC voltage control. This represents the integral coefficient for DC voltage control. This represents the Laplace transform operator.

[0141] In one embodiment, the process by which the modulation reference voltage calculation module 40 calculates the modulation reference voltage for each arm of the valve group based on the AC voltage modulation coefficient and the DC-side modulation coefficient includes:

[0142] The calculation formula is:

[0143] ;

[0144] in, Indicates the DC-side modulation coefficient. Indicates the AC voltage modulation coefficient. Indicates the modulation reference voltage. and All are weighting coefficients.

[0145] Furthermore, embodiments of this application provide a DC voltage synchronization control device for an ultra-high voltage flexible DC multi-valve group. Optionally, Figure 5 The hardware structure block diagram of the DC voltage synchronization control device for the UHV flexible DC multi-valve group is shown. (Refer to...) Figure 5 The hardware structure of the DC voltage synchronization control device for the UHV flexible DC multi-valve group may include: at least one processor 01, at least one communication interface 02, at least one memory 03, and at least one communication bus 04.

[0146] In this embodiment, the number of processor 01, communication interface 02, memory 03 and communication bus 04 is at least one, and processor 01, communication interface 02 and memory 03 communicate with each other through communication bus 04.

[0147] Processor 01 may be a central processing unit (CPU), an application-specific integrated circuit (ASIC), or one or more integrated circuits configured to implement embodiments of the present invention.

[0148] Memory 03 may include high-speed RAM, and may also include non-volatile memory, such as at least one disk storage device.

[0149] The memory stores a program that the processor can call. The program is used to execute the following DC voltage synchronization control method for ultra-high voltage flexible DC multi-valve groups, including:

[0150] Identify the individual valve groups in the UHV flexible DC multi-valve group;

[0151] For each valve group, the AC voltage modulation coefficient is generated independently by controlling the valve group.

[0152] The valve group can be independently controlled to generate DC-side modulation coefficients.

[0153] The modulation reference voltage for each arm of the valve group is calculated based on the AC voltage modulation coefficient and the DC side modulation coefficient.

[0154] The number of modules connected in series in the UHV flexible DC multi-valve group is determined, and the number of modules connected in series is multiplied by the modulation reference voltage to obtain the number of sub-modules to be engaged, so as to achieve synchronous control according to the number of sub-modules engaged.

[0155] Optionally, the refined and extended functions of the program can be found in the description of the DC voltage synchronization control method for ultra-high voltage flexible DC multi-valve groups in the method embodiments.

[0156] This application embodiment also provides a storage medium that can store a program suitable for execution by a processor. When the program runs, it controls the device containing the storage medium to perform the following UHV flexible DC multi-valve group DC voltage synchronization control method, including:

[0157] Identify the individual valve groups in the UHV flexible DC multi-valve group;

[0158] For each valve group, the AC voltage modulation coefficient is generated independently by controlling the valve group.

[0159] The valve group can be independently controlled to generate DC-side modulation coefficients.

[0160] The modulation reference voltage for each arm of the valve group is calculated based on the AC voltage modulation coefficient and the DC side modulation coefficient.

[0161] The number of modules connected in series in the UHV flexible DC multi-valve group is determined, and the number of modules connected in series is multiplied by the modulation reference voltage to obtain the number of sub-modules to be engaged, so as to achieve synchronous control according to the number of sub-modules engaged.

[0162] Specifically, the storage medium can be a computer-readable storage medium, which can be an electronic storage device such as flash memory, EEPROM (Electrically Erasable Programmable Read-Only Memory), EPROM, hard disk, or ROM.

[0163] Optionally, the refined and extended functions of the program can be found in the description of the DC voltage synchronization control method for ultra-high voltage flexible DC multi-valve groups in the method embodiments.

[0164] Furthermore, the functional modules in the various embodiments of this disclosure can be integrated together to form an independent part, or each module can exist independently, or two or more modules can be integrated to form an independent part. If the function is implemented as a software functional module 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 disclosure, in essence, or the part that contributes to the prior art, or a 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, a live streaming device, or a network device, etc.) to execute all or part of the steps of the methods in the various embodiments of this disclosure.

[0165] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0166] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0167] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for synchronous control of DC voltage in an ultra-high voltage flexible DC multi-valve group, characterized in that, include: Identify the individual valve groups in the UHV flexible DC multi-valve group; For each valve group, the phase angle, AC voltage modulation coefficient, and DC side modulation coefficient of the valve group are independently controlled. The modulation reference voltage for each arm of the valve group is calculated based on the phase angle, AC voltage modulation coefficient, and DC side modulation coefficient. The number of modules connected in series in the UHV flexible DC multi-valve group is determined, and the number of modules connected in series is multiplied by the modulation reference voltage to obtain the number of sub-modules to be engaged, so as to achieve synchronous control according to the number of sub-modules engaged.

2. The method according to claim 1, characterized in that, The formula for calculating the phase angle is: ； in, Indicates the phase angle. This represents the actual energy value of the submodule. Indicates the energy reference value of the submodule. This represents the phase angle control proportional coefficient. This represents the phase angle control integral coefficient. As the reference frequency, This represents the Laplace transform operator.

3. The method according to claim 1, characterized in that, The process of independently controlling the valve group to generate the AC voltage modulation coefficient includes: For the AC side of the valve group, reactive power proportional and integral closed-loop control is used to generate AC voltage reference values; A virtual impedance is added between the valve group and the same grid connection point to calculate the AC voltage modulation coefficient based on the AC voltage reference value.

4. The method according to claim 3, characterized in that, The method of generating AC voltage reference values ​​using reactive power proportional and integral closed-loop control includes: AC voltage reference value The calculation formula is: ； in, This represents the reference value for reactive power. This represents the actual value of reactive power. This represents the reactive power control proportional coefficient. This represents the integral coefficient for reactive power control. Indicates the reference voltage. This represents the Laplace transform operator.

5. The method according to claim 3, characterized in that, The step of adding a virtual impedance between the valve group and the same grid connection point to calculate the AC voltage modulation coefficient based on the AC voltage reference value includes: Obtain the actual AC voltage value and the AC voltage reference value; The AC current reference value is calculated based on the actual AC voltage value and the AC voltage reference value, using the following formula: ； in, Indicates the reference value of alternating current. This is the AC voltage reference value. Actual value of AC voltage This represents the virtual resistance in the virtual impedance. This represents the virtual inductance in the virtual impedance; Obtain the actual value of the AC current, and calculate the AC voltage modulation coefficient based on the actual value of the AC current and the AC current reference value. The calculation formula is as follows: ； in, Indicates the AC voltage modulation coefficient. This represents the proportional coefficient for AC current control. This represents the integral coefficient for AC current control.

6. The method according to claim 1, characterized in that, The process of independently controlling the valve group to generate the DC-side modulation coefficient includes: Obtain the actual value of the DC side voltage; Based on the actual DC-side voltage value and the preset DC-side voltage reference value, the valve group is subjected to DC voltage proportional-integral control to obtain the DC-side modulation coefficient. The calculation formula is: ； in, Indicates the DC-side voltage reference value. This represents the actual value of the DC-side voltage. This represents the proportional coefficient for DC voltage control. This represents the integral coefficient for DC voltage control. This represents the Laplace transform operator.

7. The method according to claim 1, characterized in that, The calculation of the modulation reference voltage for each arm of the valve group based on the phase angle, AC voltage modulation coefficient, and DC-side modulation coefficient includes: The phase angle is used as the phase angle reference in the modulation reference voltage calculation process. The formula for calculating the modulation reference voltage is: ； in, Indicates the DC-side modulation coefficient. Indicates the AC voltage modulation coefficient. Indicates the modulation reference voltage. and All are weighting coefficients.

8. A DC voltage synchronous control device for an ultra-high voltage flexible DC multi-valve group, characterized in that, include: Valve group determination module, used to determine each valve group in the UHV flexible DC multi-valve group; An independent control module is used to independently control the generation of phase angle, AC voltage modulation coefficient, and DC side modulation coefficient for each valve group. The modulation reference voltage calculation module is used to calculate the modulation reference voltage of each arm of the valve group based on the phase angle, AC voltage modulation coefficient and DC side modulation coefficient. The synchronization control implementation module is used to determine the number of modules connected in series in the UHV flexible DC multi-valve group, multiply the number of modules connected in series with the modulation reference voltage to obtain the number of sub-modules to be engaged, so as to realize synchronization control according to the number of sub-modules to be engaged.

9. A DC voltage synchronous control device for an ultra-high voltage flexible DC multi-valve group, characterized in that, Including memory and processor; The memory is used to store programs; The processor is used to execute the program to implement the various steps of the DC voltage synchronization control method for ultra-high voltage flexible DC multi-valve groups as described in any one of claims 1-7.

10. A storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements each step of the DC voltage synchronization control method for ultra-high voltage flexible DC multi-valve groups as described in any one of claims 1-7.

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