Non-communication voltage balance control method for sending-end addressing extra-high voltage direct current series valve group

Abstract

The invention provides a non-communication voltage balance control method for a sending-end addressing extra-high-voltage direct-current series valve group, and belongs to the technical field of extra-high-voltage direct-current power transmission system control. In a sending end converter station address division construction scene, voltage balance control of an original high and low voltage valve group depends on inter-station communication to carry out real-time adjustment, and when a communication line breaks down, system control failure is easily caused. On the basis of communication decoupling of high and low voltage valve banks at the sending end, a control strategy without inter-station communication at the sending end is designed, specifically, the high-voltage valve bank adopts constant current control, and the low-voltage valve bank adopts constant voltage control. According to the scheme, through the current-voltage series coupling characteristic, the voltage balance control of the high-voltage valve group and the low-voltage valve group can be realized without inter-station communication, so that the influence of communication faults on the system is avoided, and the voltage balance of the series valve group is ensured. The method solves the communication dependence problem of addressing direct current system sending end control, maintains the voltage balance of high and low voltage valve groups, is simple in principle, is easy to realize, and is suitable for engineering practical application.

Description

Technical Field

[0001] This invention relates to the field of ultra-high voltage direct current (UHVDC) transmission system control technology, and in particular to a communication-free voltage balance control method for UHVDC series valve groups with different addresses at the sending end. Background Technology

[0002] Sending-end site-separated ultra-high voltage direct current (UHVDC) transmission systems can reduce AC line construction costs by transmitting power in series on the DC side. However, the site-separated construction of the sending-end converter stations poses challenges to communication between the series valve group controls. This paper proposes a communication-free voltage balance control method for the sending-end site-separated UHVDC series valve groups in the Jinshang-Hubei ±800kV cascaded UHVDC transmission system. Current research on sending-end site-separated UHVDC transmission systems employs a composite control of constant current and DC voltage balance control for the sending-end series valve groups. By adjusting the DC voltage deviation between the high and low voltage valve groups, a DC current compensation is established to maintain the valve group voltage balance in real time.

[0003] However, the unique topology of the sending-end addressing system transforms the communication for voltage balance control of high- and low-voltage valve groups from inter-station communication within the same location to inter-station communication across different locations, threatening the safe and stable operation of the power system. Therefore, it is urgently needed to propose a communication-free voltage balance control method for sending-end addressing UHVDC series valve groups that is simple in structure, easy to implement, and readily engineering-ready. Summary of the Invention

[0004] The purpose of this invention is to propose a communication-free voltage balance control method for ultra-high voltage DC series valve groups with separate addresses at the sending end, so as to solve the problems of inter-station communication and DC voltage balance of high and low voltage valve groups at the sending end in the prior art.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A voltage balance control method for UHVDC series valve groups with separate sending-end addresses includes: The DC voltage measurement value, DC current measurement value, and DC line resistance of the high-pressure valve group are obtained. Combined with the DC power transmitted by the system, the DC current setting value and current reference value of the high-pressure valve group are calculated. The firing angle of the high-pressure valve group is obtained based on the DC current setting value and current reference value of the high-pressure valve group. The constant current control of the high-pressure valve group converter station is completed based on the firing angle of the high-pressure valve group. The system acquires the measured DC voltage value, reference DC voltage value, measured DC current value, and set DC current value of the low-pressure valve group. It then calculates the voltage difference in the outer loop and the current difference in the inner loop of the constant voltage control. Based on these values, the system obtains the firing angle of the low-pressure valve group and completes the constant voltage control of the converter station using the firing angle.

[0006] Preferably, the DC current setting value and current reference value of the high-voltage valve group are calculated based on the DC power transmitted by the system. The firing angle of the high-voltage valve group is then obtained based on the DC current setting value and current reference value, including: The midpoint voltage of the DC line is calculated based on the measured DC voltage, measured DC current, and DC line resistance. The DC current command value of the high-voltage valve group is obtained based on the midpoint voltage of the DC line. Obtain the DC power transmitted by the system; The DC current setting value of the high-voltage valve group is obtained based on the DC power and the DC line midpoint voltage. The reference value of DC current for the high-pressure valve group is obtained by taking the smaller value between the DC current command value and the DC current setting value. Based on the measured DC current value and the reference DC current value, the input current difference of the constant current control PI loop is obtained; The current difference is passed through a PI circuit to obtain the high-voltage valve group's advance triggering angle, and the difference from π is used to obtain the high-voltage valve group's triggering angle.

[0007] Preferably, the midpoint voltage of the DC line is obtained by measuring the voltage at the outlet of the high-voltage valve group and combining it with the DC line resistance, through voltage and current calculation. The specific calculation method is as follows: I dc = I dcH U dc = U dcH - I dc × R dcline in, I dc This refers to the DC line current. I dcH This is the measured DC current value at the outlet of the high-pressure valve assembly. U dc This is the voltage at the midpoint of the DC line. U dcH This is the measured DC voltage value at the outlet of the high-pressure valve assembly. R dcline This is the resistor in a DC circuit.

[0008] Preferably, the DC current setting value is calculated using the DC power transmitted by the system and the midpoint voltage of the DC line. The specific calculation method is as follows:

[0009] in, Iset This is the DC current setting value; P dc The DC power transmitted by the system; U dc This is the voltage at the midpoint of the DC line.

[0010] Preferably, the DC line midpoint voltage, after passing through the low-voltage current limiting link VDCOL, yields the high-voltage valve group DC current command value, which is the smaller of the DC current setting value and the command value, to obtain the high-voltage valve group DC current reference value; wherein the low-voltage current limiting link specifically comprises:

[0011] in, U dc This is the voltage at the midpoint of the DC line. I H Indicates the voltage at the midpoint of a DC line. U dc The current value obtained after passing through the low-voltage current limiting circuit VDCOL; By comparing with the DC current setting value I set After taking the smaller value, the reference value of the DC current of the high-pressure valve group is obtained. I dcrH Its expression is: .

[0012] Preferably, the expression for the input difference of the constant current control PI loop of the high-pressure valve group is:

[0013] in, The input difference is used for constant current control PI loop. I dcrH This is the reference value for the DC voltage of the high-pressure valve group; I dcH This is the measured DC current value at the outlet of the high-pressure valve assembly. The firing angle of the high-pressure valve group is obtained by subtracting the leading firing angle of the high-pressure valve group from π, and its expression is as follows:

[0014] in, α H This refers to the firing angle of the high-pressure valve assembly. k pi The proportional coefficient for constant current control; k ii The integral coefficient for constant current control; This indicates the integration process.

[0015] Preferably, the calculation of the voltage difference in the outer loop of the constant voltage control and the current difference in the inner loop of the constant voltage control, and the determination of the low-pressure valve group firing angle based on the voltage difference in the outer loop of the constant voltage control and the current difference in the inner loop of the constant voltage control, includes: The difference between the measured DC voltage value and the reference DC voltage value is used to obtain the voltage difference value of the PI input of the constant voltage control outer loop; The constant voltage control outer loop PI obtains the low-pressure valve group DC current command value based on the voltage difference, and the smaller value of the low-pressure valve group DC current setting value is used to obtain the low-pressure valve group DC current reference value. The difference between the measured DC current value of the low-pressure valve group and the DC current reference value is used to obtain the current difference value of the PI input in the constant voltage control inner loop. The current difference is passed through a PI circuit to obtain the low-pressure valve group's advance trigger angle, and the difference from π is used to obtain the low-pressure valve group's trigger angle.

[0016] Preferably, the expression for the voltage difference of the PI input to the outer loop of the low-pressure valve group constant voltage control is:

[0017] in, The voltage difference input to the outer loop PI controller for the low-pressure valve group; U dcrL This is the reference value for the DC voltage of the low-pressure valve group; U dcL This is the measured DC voltage value of the low-pressure valve group; The reference value of the low-pressure valve group DC current is obtained by taking the smaller of the low-pressure valve group current command value output by the constant voltage outer loop PI and the DC current setting value. Its expression is:

[0018] in, I dcrL This is a reference value for the DC current of the low-pressure valve group; I set This is the DC current setting value; I L This is the current command value for the low-pressure valve group.

[0019] Preferably, the expression for the current difference value of the PI input in the inner loop of the low-pressure valve group constant voltage control is:

[0020] in, The current difference input to the PI controller in the constant voltage control inner loop; I dcrL This is a reference value for the DC current of the low-pressure valve group; I dcL This is the measured DC current value of the low-pressure valve group; The low-pressure valve group firing angle is obtained by subtracting the low-pressure valve group leading firing angle from π, and its expression is as follows:

[0021]

[0022] in, k pv The proportional coefficient for constant voltage control; k iv The integral coefficient for constant voltage control; Indicates the integration process; α L This refers to the firing angle of the low-pressure valve group converter. The UHVDC series valve group with separate addressing at the sending end has no communication voltage balance control device, including: High-voltage valve group converter station constant current control module: used to acquire the measured DC voltage, DC current and DC line resistance of the high-voltage valve group, and calculate the DC current setting value and current reference value of the high-voltage valve group in combination with the DC power transmitted by the system. Based on the DC current setting value and current reference value of the high-voltage valve group, the high-voltage valve group firing angle is obtained, and the constant current control of the high-voltage valve group converter station is completed based on the firing angle of the high-voltage valve group. The constant voltage control module for the low-pressure valve group converter station is used to acquire the measured DC voltage value, DC voltage reference value, measured DC current value, and DC current setting value of the low-pressure valve group; calculate the constant voltage control outer loop voltage difference and constant voltage control inner loop current difference; obtain the low-pressure valve group firing angle based on the constant voltage control outer loop voltage difference and constant voltage control inner loop current difference; and complete the constant voltage control of the low-pressure valve group converter station based on the low-pressure valve group firing angle.

[0023] This invention further protects a computer device, which includes a processor and a memory. The memory stores at least one instruction, at least one program, a code set, or an instruction set. The instruction, program, code set, or instruction set is loaded and executed by the processor to implement the above-mentioned communication-free voltage balance control method for ultra-high voltage DC series valve groups with separate addressing at the sending end.

[0024] The present invention further protects a computer-readable storage medium storing at least one instruction, at least one program, code set, or instruction set, wherein the instruction, program, code set, or instruction set is loaded and executed by a processor to implement the above-described method for communication-free voltage balance control of UHVDC series valve groups with separate addressing at the sending end.

[0025] The advantages of this invention compared to the prior art are: (1) This invention proposes a voltage balance control method for UHVDC series valve groups with different addresses at the sending end. By adopting a constant current control strategy for the high-voltage valve group at the sending end and a constant voltage control strategy for the low-voltage valve group, the voltage balance link is removed in the control, thereby achieving the effect of no inter-station communication for the series valve groups.

[0026] (2) By adopting a constant current control strategy for the high-pressure valve group at the sending end and a constant voltage control strategy for the low-pressure valve group, the present invention can achieve the balance of DC voltage of the high-pressure and low-pressure valve groups without inter-station communication.

[0027] (3) In the low-pressure valve group constant voltage control, the present invention adds current inner loop control, thereby achieving the purpose of limiting transient DC current together with the high-pressure valve group constant current control.

[0028] (4) The method proposed in this invention is simple to operate and easy to apply in engineering practice. It also has a good suppression effect on the rise of transient DC voltage and current when a transient fault occurs in the system. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in this invention, the accompanying drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is the system topology diagram of the high and low pressure valve group converter station proposed in Embodiment 1 of the present invention; Figure 2 This is a flowchart of the communication-free voltage balance control method for ultra-high voltage DC series valve groups with separate addressing at the sending end, as proposed in Embodiment 1 of the present invention. Figure 3 This is the control block diagram of the receiving-end converter station of the sending-end high and low pressure valve group converter station proposed in Embodiment 1 of the present invention; Figure 4 This is the system steady-state response diagram proposed in Embodiment 1 of the present invention, wherein, Figure 4 (a) Figure 4 (b) Figure 4 (c) The dynamic response diagrams of DC voltage, DC current and firing angle of the high and low pressure valve group at the sending end from startup to the system entering steady state are respectively. Figure 5 This is the system transient response diagram proposed in Embodiment 1 of the present invention, wherein, Figure 5 (a) Figure 5 (b) Figure 5(c) are transient characteristic response diagrams of various electrical quantities of the system after a three-phase ground fault occurs on the AC bus at the receiving end, representing the DC voltage, DC current and firing angle of the high and low voltage valve group at the sending end. Detailed Implementation

[0031] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the invention. However, those skilled in the art will understand that the invention can be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of the invention with unnecessary detail.

[0032] The following will describe in detail, with reference to the accompanying drawings, the method for voltage balance control of UHVDC series valve groups without communication at the sending end of the present invention.

[0033] Example 1: Figure 1 This is a system topology diagram of the communication-free voltage balance control method for ultra-high voltage DC series valve groups with separate sending-end addresses proposed in this embodiment of the invention. like Figure 1 As shown, the sending-end high- and low-voltage valve group converter stations are constructed at separate sites, with a rated transmission capacity of 8000 MW. The two converter stations are connected on the DC side via a ±400 kV DC overhead line, and then transmit power to the receiving-end converter station via approximately 1780 km of ±800 kV DC overhead line. Both the sending-end and receiving-end converter stations adopt a symmetrical bipolar connection. Each pole of the sending end consists of a 12-pulse LCC high-voltage converter valve group and a 12-pulse LCC low-voltage converter valve group connected in series, while the receiving-end bipolar system uses four 12-pulse LCC converter valve groups constructed at the same site.

[0034] Therefore, it can be seen that during the rated operation of the UHVDC transmission system with distributed sending-end locations, maintaining the midpoint voltage of the positive DC line at 800kV and the DC current setting value at 5kA, both per-unit values ​​are... U dc , I set All are 1.0 pu.

[0035] Figure 2 This is a flowchart of the communication-free voltage balance control method for ultra-high voltage DC series valve groups with separate addressing at the sending end, as proposed in an embodiment of the present invention. Figure 2 As shown, it specifically includes: S1, High-pressure valve group constant current control S1.1 Obtain the measured DC voltage value at the outlet of the high-pressure valve group. U dcH and DC current measurement value I dcHand DC line resistance R dcline DC line midpoint voltage U dc DC current command value of high-pressure valve group I H ; Among them, DC line resistance R dcline The system parameters are known, and the DC voltage at the outlet of the high-pressure valve group is... U dcH DC current measurement value of high pressure valve group I dcH The voltage at the midpoint of a DC line is obtained through measurement. U dc By measuring the DC voltage at the outlet of the high-pressure valve group U dcH Then, it is obtained through voltage and current calculations. The specific calculation method is as follows: U dc = U dcH - I dc × R dcline in, I dc This refers to the DC line current. I dcH This is the measured DC current value of the high-pressure valve group; U dc This is the voltage at the midpoint of the DC line; U dcH This refers to the voltage at the outlet of the high-pressure valve assembly. R dcline This is the resistor in a DC circuit.

[0036] S1.2 Obtain the DC power transmitted by the system. P dc DC current setting value I set ; Among them, the DC power transmitted by the system P dc The DC current setting value is given by the upper layer. I set DC power transmitted through the system P dc With DC line midpoint voltage U dc The calculation method is as follows:

[0037] S1.3 Obtain the reference value of DC voltage for the high-pressure valve group. I dcrH ; In S1.3, the midpoint voltage of the DC line U dc After passing through the low-voltage current limiting circuit VDCOL, it is compared with the DC current setting value. I set Take the smaller value to obtain the reference value of the DC voltage of the high-pressure valve group. I dcrH The low-voltage current limiting component is as follows:

[0038] in, I H Indicates the voltage at the midpoint of a DC line. U dc The high-pressure valve group current command value obtained after passing through the low-pressure current limiting circuit VDCOL. Then, by comparing with the DC current setting value... I set After taking the smaller value, the reference value of the DC current of the high-pressure valve group is obtained. I dcrH Its expression is: ; S1.4 Obtain the input current difference of the constant current control PI loop; The expression for the input difference of the constant current control PI loop is as follows:

[0039] S1.5. The high-pressure valve group advance angle is obtained through the PI circuit, and the difference between this and π is used to obtain the high-pressure valve group converter firing angle. α H ; Among them, the high-pressure valve group's advance firing angle is obtained through a PI control loop; the high-pressure valve group converter firing angle... α H It is obtained by subtracting π from the lead-out firing angle, and the control expression is as follows:

[0040] in, α H This refers to the firing angle of the high-pressure valve group converter. k pi The proportional coefficient for constant current control; k ii The integral coefficient for constant current control; This indicates the integration process.

[0041] S2, Low-pressure valve group converter station constant voltage control S2.1 Obtain the measured DC voltage value of the low-pressure valve group. U dcL DC voltage reference value U dcrL DC current measurement value I dcL DC current setting value I setr ; S2.2 Obtain the voltage difference of the PI input to the outer loop of the low-pressure valve group's set voltage control. The expression for the voltage difference of the PI input in the outer loop of the low-pressure valve group constant voltage control is as follows:

[0042] S2.3 Obtain the reference value of DC current for the low-pressure valve group. I dcrL Among them, the DC current reference value of the low-pressure valve group I dcrL The low-pressure valve group current command value output by the constant voltage outer loop PI I L With DC current setting value I set After taking the smaller value, its expression is: I dcrL =Min ( I set , I L ) S2.4 Obtain the current difference value of the PI input in the inner loop of the low-pressure valve group constant voltage control; The expression for the current difference of the PI input in the inner loop of the low-pressure valve group constant voltage control is as follows:

[0043] S2.5. The low-pressure valve group advance angle is obtained through the PI circuit, and the difference between this and π is used to obtain the low-pressure valve group converter firing angle. α L ; The low-pressure valve group's advance firing angle is obtained through a PI control loop; the high-pressure valve group's converter firing angle... α L It is obtained by subtracting π from the lead-out firing angle, and the control expression is as follows:

[0044]

[0045] in, k pvThe proportional coefficient for constant voltage control; k iv The integral coefficient for constant voltage control; Indicates the integration process; α L This refers to the firing angle of the low-pressure valve group converter.

[0046] Figure 3 This is the control block diagram of the receiving-end converter station of the sending-end high and low pressure valve group converter station proposed in Embodiment 1 of the present invention.

[0047] Figure 4 This is the steady-state response diagram of the system after implementing the method proposed in this invention; Figure 5 This is a transient response diagram of the electrical quantities of the system after a three-phase ground fault occurs in the AC system at the receiving end of the system following the implementation of the method proposed in this invention; wherein, Figure 4 (a) Figure 4 (b) Figure 4 (c) The dynamic response diagrams of the DC voltage, DC current and firing angle of the high and low pressure valve groups at the sending end from startup to the system entering steady state are shown respectively. Figure 5 (a) Figure 5 (b) Figure 5 (c) represents the transient characteristics of various electrical quantities in the system after a three-phase ground fault occurs on the AC busbar at the receiving end, including the DC voltage, DC current, and firing angle of the high and low voltage valve group at the sending end.

[0048] This invention employs the proposed communication-free voltage balance control method for ultra-high voltage DC series valve groups with distributed sending-end addresses. Figure 4 , Figure 5 The following conclusions can be drawn: Figure 4 During system startup, the trigger angle of the high and low pressure valve groups is adjusted to approximately 90°. Then, trigger signals are injected according to the 12-pulse converter startup sequence. At this point, the DC voltage of the valve groups is close to zero, and the system begins operation. Afterward, the turn-off angle Γ of the receiving-end converter station is gradually reduced, causing the DC voltage to rise from zero. Simultaneously, in conjunction with the constant current control of the high-pressure valve groups, the DC current is gradually increased until the target value is reached. Figure 4 (a) Figure 4 (b) Figure 4 (c) It can be seen that the proposed strategy enables the sent-end addressable DC transmission system to reach steady-state operation from "cold start".

[0049] Figure 5 In the process, after a three-phase ground fault occurs on the AC bus at the receiving end, the high-voltage valve group at the sending end increases the firing angle to 120°~150° through the rapid phase shifting function, so that the high-voltage valve group of the converter station at the sending end enters the "inverter" state, turns the DC voltage from a positive value to a negative value, and quickly transfers the power on the DC line, thereby suppressing the rise of DC current.

[0050] The method employed in this invention, by altering the traditional constant current control of the high and low pressure valve groups at the sending end, adopts constant current control for the high-pressure valve group and constant voltage control for the low-pressure valve group. This enables the sending-end converter station to maintain voltage balance between the high and low pressure valve groups even under conditions of no inter-station communication or communication failure, ensuring stable system operation. The method proposed in this invention has a simple structure, is easy to apply in practical engineering, and exhibits good control performance in the event of system failure.

[0051] All of the above-mentioned optional technical solutions can be combined in any way to form the optional embodiments of this application, and will not be described in detail here.

[0052] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0053] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of this application can be implemented in various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0054] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0055] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0056] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0057] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0058] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A method for voltage balance control of a sending-end addressable UHVDC series valve group without communication voltage, characterized in that, include: The DC voltage measurement value, DC current measurement value, and DC line resistance of the high-pressure valve group are obtained. Combined with the DC power transmitted by the system, the DC current setting value and current reference value of the high-pressure valve group are calculated. The firing angle of the high-pressure valve group is obtained based on the DC current setting value and current reference value of the high-pressure valve group. The constant current control of the high-pressure valve group converter station is completed based on the firing angle of the high-pressure valve group. The system acquires the measured DC voltage value, reference DC voltage value, measured DC current value, and set DC current value of the low-pressure valve group. It then calculates the voltage difference in the outer loop and the current difference in the inner loop of the constant voltage control. Based on these values, the system obtains the firing angle of the low-pressure valve group and completes the constant voltage control of the converter station using the firing angle.

2. The sending-end addressable UHVDC series valve group non-communication voltage balance control method according to claim 1, characterized in that, Based on the DC power transmitted by the system, the DC current setting value and current reference value of the high-pressure valve group are calculated. The firing angle of the high-pressure valve group is then obtained based on these values, including: The midpoint voltage of the DC line is calculated based on the measured DC voltage, measured DC current, and DC line resistance. The DC current command value of the high-voltage valve group is obtained based on the midpoint voltage of the DC line. Obtain the DC power transmitted by the system; The DC current setting value of the high-voltage valve group is obtained based on the DC power and the DC line midpoint voltage. The reference value of DC current for the high-pressure valve group is obtained by taking the smaller value between the DC current command value and the DC current setting value. Based on the measured DC current value and the reference DC current value, the input current difference of the constant current control PI loop is obtained; The current difference is passed through a PI circuit to obtain the high-voltage valve group's advance triggering angle, and the difference from π is used to obtain the high-voltage valve group's triggering angle.

3. The sending-end address-specific UHVDC series valve group non-communication voltage balance control method according to claim 2, characterized in that, The voltage at the midpoint of the DC line is obtained by measuring the voltage at the outlet of the high-voltage valve group and combining it with the resistance of the DC line, through voltage and current calculation. The specific calculation method is as follows: I dc = I dcH U dc = U dcH - I dc × R dcline wherein, I dc is the DC line current; I dcH is the DC line current measurement at the high voltage valve group outlet; U dc is the DC line midpoint voltage; U dcH is the DC voltage measurement at the high voltage valve group outlet; R dcline is the DC circuit resistance.

4. The sending-end address-specific UHVDC series valve group non-communication voltage balance control method of claim 3, characterized in that, The DC current setting value is calculated using the DC power transmitted by the system and the DC line midpoint voltage. The specific calculation method is as follows: wherein, I set is a direct current setpoint; P dc is a direct current power transmitted by the system; U dc is a direct current line midpoint voltage.

5. The sending-end address-specific UHVDC series valve group non-communication voltage balance control method according to claim 4, characterized in that, The DC line midpoint voltage, after passing through the low-voltage current limiting circuit VDCOL, yields the high-voltage valve group DC current command value. The smaller of this command value and the DC current setting value is used to obtain the high-voltage valve group DC current reference value. Specifically, the low-voltage current limiting circuit is as follows: wherein, U dc is the DC link midpoint voltage; I H is the DC link midpoint voltage U dc is the current value after the low voltage current limiting element VDCOL. The direct current setting value is set by the direct current setting value I set The high pressure valve group direct current reference value is obtained by taking the minimum value I dcrH The expression is: 。 6. The sending-end address-specific UHVDC series valve group non-communication voltage balancing control method according to claim 5, characterized in that, The expression for the input difference of the constant current control PI loop of the high-pressure valve group is: Wherein, is the difference value for the constant current control PI loop input; I dcrH is the high-pressure valve group DC voltage reference value; I dcH is the high-pressure valve group outlet DC current measurement value; The firing angle of the high-pressure valve group is obtained by subtracting the leading firing angle of the high-pressure valve group from π, and its expression is as follows: wherein, α H is the high pressure valve group trigger angle; k pi is the proportional coefficient of the constant current control; k ii is the integral coefficient of the constant current control; denotes the integral element.

7. The method of claim 1, wherein the voltage balance control method is performed without communication voltage in the sending-end addressed UHVDC series valve group. Calculate the voltage difference in the outer loop of the constant voltage control and the current difference in the inner loop of the constant voltage control. Based on the voltage difference in the outer loop of the constant voltage control and the current difference in the inner loop of the constant voltage control, obtain the firing angle of the low-pressure valve group, including: The difference between the measured DC voltage value and the reference DC voltage value is used to obtain the voltage difference value of the PI input of the constant voltage control outer loop; The constant voltage control outer loop PI obtains the low-pressure valve group DC current command value based on the voltage difference, and the smaller value of the low-pressure valve group DC current setting value is used to obtain the low-pressure valve group DC current reference value. The difference between the measured DC current value of the low-pressure valve group and the DC current reference value is used to obtain the current difference value of the PI input in the constant voltage control inner loop. The current difference value is subjected to a PI link to obtain a low-voltage valve group leading trigger angle, and the low-voltage valve group trigger angle is obtained by subtracting π from the low-voltage valve group leading trigger angle.

8. The sending-end address-specific UHVDC series valve group non-communication voltage balance control method according to claim 7, characterized in that, The expression of the voltage difference value inputted by the low-voltage valve group constant voltage control outer loop PI is: Wherein, The voltage difference of the voltage control outer ring PI input is set for the low-pressure valve group; U dcrL The DC voltage reference value is set for the low-pressure valve group; U dcL The DC voltage measurement value is set for the low-pressure valve group; The low-voltage valve group DC current reference value is obtained by taking the minimum value of the low-voltage valve group current command value outputted by the low-voltage valve group constant voltage outer loop PI and the DC current setting value, and the expression is: wherein, I dcrL is a low pressure valve group direct current reference value; I set is a direct current setting value; I L is a low pressure valve group current command value.

9. The sending-end address-specific UHVDC series valve group non-communication voltage balance control method according to claim 8, characterized in that, The expression of the current difference value inputted by the low-voltage valve group constant voltage control inner loop PI is: Wherein, is the current difference value of the inner ring PI input of the constant voltage control; I dcrL is the low-pressure valve group DC current reference value; I dcL is the low-pressure valve group DC current measurement value; The low-voltage valve group trigger angle is obtained by subtracting π from the low-voltage valve group leading trigger angle, and the expression is as follows: wherein, k pv is a proportional coefficient for constant voltage control; k iv is an integral coefficient for constant voltage control; denotes an integral element; α L is a low voltage valve group inverter firing angle.

10. A sending end address-specific extra-high voltage DC series valve group non-communication voltage balancing control device, characterized in that, The high-voltage valve group converter station constant current control module is used to obtain the high-voltage valve group DC voltage measurement value, DC current measurement value and DC line resistance, calculate the high-voltage valve group DC current setting value and current reference value in combination with the transmitted DC power of the system, obtain the high-voltage valve group trigger angle according to the high-voltage valve group DC current setting value and current reference value, and complete the high-voltage valve group converter station constant current control according to the high-voltage valve group trigger angle; The low-voltage valve group converter station constant voltage control module is used to obtain the low-voltage valve group DC voltage measurement value, DC voltage reference value, low-voltage valve group DC current measurement value and low-voltage valve group DC current setting value, calculate the constant voltage control outer loop voltage difference value and constant voltage control inner loop current difference value, obtain the low-voltage valve group trigger angle according to the constant voltage control outer loop voltage difference value and constant voltage control inner loop current difference value, and complete the low-voltage valve group converter station constant voltage control according to the low-voltage valve group trigger angle. The computer device includes a processor and a memory, and the memory stores at least one instruction, at least one program, a code set or an instruction set, which are loaded and executed by the processor to realize the sending-end address-specific UHV DC series valve group non-communication voltage balance control method of any one of claims 1-9.

11. A computer device, comprising: The computer readable storage medium stores at least one instruction, at least one program, a code set or an instruction set, which are loaded and executed by the processor to realize the sending-end address-specific UHV DC series valve group non-communication voltage balance control method of any one of claims 1-9.

12. A computer-readable storage medium, characterized in that, ​

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