Control method and system for a sink tap

Abstract

The application discloses a control method and system of a receiving-end tap changer, and the method comprises the following steps: determining an over-polarity gear of the receiving-end tap changer based on a positive gear and a negative gear of a converter transformer of the receiving-end tap changer in a high-voltage direct-current power transmission system; acquiring power transmission system information corresponding to the high-voltage direct-current power transmission system; determining a lowest direct-current voltage of a sending end of the high-voltage direct-current power transmission system in the over-polarity gear based on the over-polarity gear, the power transmission system information and information corresponding to the receiving-end tap changer; determining a direct-current voltage control range based on the lowest direct-current voltage of the sending end; after the gear of the receiving-end tap changer reaches the over-polarity gear, determining a gear adjustment trend of the receiving-end tap changer, if the gear adjustment trend meets a first condition, acquiring a current direct-current voltage of the sending end of the high-voltage direct-current power transmission system in real time, and when the current direct-current voltage of the sending end is within the direct-current voltage control range, controlling the receiving-end tap changer to maintain in the over-polarity gear, so that the number of over-polarities of the receiving-end tap changer can be reduced.

Description

Technical Field

[0001] This application relates to the field of power technology, and in particular to a control method and system for a receiving-end tap changer. Background Technology

[0002] High-voltage direct current (HVDC) transmission projects are a core means of optimizing energy resource allocation. In recent years, HVDC transmission technology has developed rapidly, and numerous HVDC converter stations have been built across various regions. However, as the scale of HVDC transmission projects continues to expand, operational issues with tap changers have gradually emerged. Tap changers are crucial components of transformers in HVDC transmission systems. The tap positions refer to the preset tap locations on the transformer windings. By switching these different positions, the transformer's turns ratio can be adjusted, thereby changing the output voltage. Typically, each tap corresponds to a different voltage regulation range, enabling the transformer to adapt to different grid conditions and load demands.

[0003] In related technologies, ultra-high voltage direct current transmission projects typically adopt a layered access mode. In this case, the tap changer will frequently switch positions, which will cause the tap changer to frequently experience over-polarity phenomena. This not only affects the stable operation of the equipment, but also increases maintenance costs. Summary of the Invention

[0004] To address the aforementioned technical problems, this application proposes a control method and system for a receiving-end tap changer, which can reduce the number of times the receiving-end tap changer changes polarity.

[0005] In a first aspect, embodiments of this application provide a control method for a receiving-end tap changer, including: Based on the positive and negative positions of the converter transformer of the receiving-end tap changer in the high-voltage direct current transmission system, the polarity position of the receiving-end tap changer is determined. Obtain the transmission system information corresponding to the high-voltage direct current transmission system; Based on the polarity switch, the power transmission system information, and the information corresponding to the receiving end tap changer, the minimum DC voltage at the sending end of the high-voltage direct current transmission system under the polarity switch is determined. The DC voltage control range is determined based on the lowest DC voltage at the sending end; After the tap position of the receiving end tap changer reaches the over-polarity position, the adjustment trend of the receiving end tap changer is determined. If the adjustment trend meets the first condition, the current DC voltage of the sending end of the high voltage DC transmission system is obtained in real time. When the current DC voltage of the sending end is within the DC voltage control range, the receiving end tap changer is controlled to maintain the over-polarity position.

[0006] Optionally, the power transmission system information includes the first configuration information and actual operating current of the high-voltage direct current transmission system, and also includes the second configuration information and receiving-end AC voltage of the receiving-end AC system in the high-voltage direct current transmission system; the information corresponding to the receiving-end tap changer includes the rated turns ratio of the converter transformer corresponding to the receiving-end tap changer; The determination of the minimum DC voltage at the sending end of the high-voltage direct current transmission system under the over-polarity position, based on the over-polarity position, the transmission system information, and the information corresponding to the receiving-end tap changer, includes: Based on the AC voltage at the receiving end, the rated transformer ratio, and the polarity setting, determine the ideal no-load DC voltage at the receiving end; Based on the second configuration information, the first configuration information and actual operating current of the high-voltage direct current transmission system, and the ideal no-load DC voltage of the receiving end, the ideal DC voltage of the high-voltage direct current transmission system is determined. Based on the ideal DC voltage of the high-voltage direct current transmission system, the first configuration information, and the actual operating current, the minimum DC voltage at the sending end is determined.

[0007] Optionally, the first configuration information includes the pulse number, rated DC current and forward conduction voltage drop of the converter valve of the high voltage DC transmission system, and the second configuration information includes the turn-off angle, per-unit value of inductor voltage drop, per-unit value of resistor voltage drop and rated ideal no-load DC voltage of the receiving-end AC system. The step of determining the ideal DC voltage of the high-voltage direct current transmission system based on the second configuration information, the first configuration information and actual operating current of the high-voltage direct current transmission system, and the ideal no-load DC voltage at the receiving end includes: Based on the pulse number, actual operating current, rated DC current, and forward conduction voltage drop of the converter valve of the high-voltage direct current transmission system, the shut-off angle, per-unit value of inductor voltage drop, per-unit value of resistor voltage drop, and rated ideal no-load DC voltage of the receiving-end AC system, and the ideal no-load DC voltage of the receiving end, the ideal DC voltage of the high-voltage direct current transmission system is determined.

[0008] Optionally, the first configuration information includes the DC resistance of the high-voltage direct current transmission system; The determination of the minimum DC voltage at the sending end based on the ideal DC voltage of the high-voltage direct current transmission system, the first configuration information, and the actual operating current includes: Based on the ideal DC voltage, DC resistance, and actual operating current of the high-voltage direct current transmission system, the minimum DC voltage at the sending end is determined.

[0009] Optionally, the power transmission system information includes the rated DC voltage and real-time DC power of the high-voltage direct current transmission system, and the information corresponding to the receiving-end tap changer includes the original tap position control strategy of the receiving-end tap changer, wherein the original tap position control strategy refers to the tap position of the receiving-end tap changer being determined by the real-time DC power. The determination of the minimum DC voltage at the sending end of the high-voltage direct current transmission system under the over-polarity position, based on the over-polarity position, the transmission system information, and the information corresponding to the receiving-end tap changer, includes: Based on the original gear control strategy and the real-time DC power, the original strategy gear of the receiving end tap changer is determined; based on the original strategy gear, the polarity gear, and the rated DC voltage, the minimum DC voltage of the sending end is determined.

[0010] Optionally, the method further includes at least one of the following: Before the tap position of the receiving end tap switch reaches the over-polarity position, the receiving end tap switch is controlled according to the original position control strategy of the receiving end tap switch. After the tap changer reaches the over-polarity position, if the position adjustment trend meets the second condition, the tap changer is controlled according to the original position control strategy of the tap changer.

[0011] Secondly, embodiments of this application provide a control system for a receiving-end tap changer, comprising: The tap position determination module is used to determine the polarity position of the receiving-end tap switch based on the positive and negative tap positions of the converter transformer of the receiving-end tap switch in the high-voltage direct current transmission system. The power transmission system information acquisition module is used to acquire the power transmission system information corresponding to the high voltage direct current transmission system; The sending-end minimum DC voltage determination module is used to determine the sending-end minimum DC voltage of the high-voltage DC transmission system under the polarity crossing position based on the polarity crossing position, the transmission system information, and the information corresponding to the receiving-end tap changer; the voltage range determination module is used to determine the DC voltage control range based on the sending-end minimum DC voltage. The first switch control module is used to determine the adjustment trend of the tap position of the receiving end tap switch after the receiving end tap position reaches the over-polarity position. If the adjustment trend of the tap position meets the first condition, the current DC voltage of the sending end of the high voltage DC transmission system is obtained in real time. When the current DC voltage of the sending end is within the DC voltage control range, the receiving end tap switch is controlled to maintain the over-polarity position.

[0012] Optionally, the power transmission system information includes the first configuration information and actual operating current of the high-voltage direct current transmission system, and also includes the second configuration information and receiving-end AC voltage of the receiving-end AC system in the high-voltage direct current transmission system; the information corresponding to the receiving-end tap changer includes the rated turns ratio of the converter transformer corresponding to the receiving-end tap changer; The determination of the minimum DC voltage at the sending end of the high-voltage direct current transmission system under the over-polarity position, based on the over-polarity position, the transmission system information, and the information corresponding to the receiving-end tap changer, includes: Based on the AC voltage at the receiving end, the rated transformer ratio, and the polarity setting, determine the ideal no-load DC voltage at the receiving end; Based on the second configuration information, the first configuration information and actual operating current of the high-voltage direct current transmission system, and the ideal no-load DC voltage of the receiving end, the ideal DC voltage of the high-voltage direct current transmission system is determined. Based on the ideal DC voltage of the high-voltage direct current transmission system, the first configuration information, and the actual operating current, the minimum DC voltage at the sending end is determined.

[0013] Optionally, the power transmission system information includes the rated DC voltage and real-time DC power of the high-voltage direct current transmission system, and the information corresponding to the receiving-end tap changer includes the original tap position control strategy of the receiving-end tap changer, wherein the original tap position control strategy refers to the tap position of the receiving-end tap changer being determined by the real-time DC power. The determination of the minimum DC voltage at the sending end of the high-voltage direct current transmission system under the over-polarity position, based on the over-polarity position, the transmission system information, and the information corresponding to the receiving-end tap changer, includes: Based on the original gear control strategy and the real-time DC voltage at the sending end of the high-voltage DC transmission system, the original strategy gear of the receiving end tap changer is determined. Based on the original strategy level, the over-polarity level, and the rated DC voltage of the high-voltage direct current transmission system, the minimum DC voltage at the sending end is determined.

[0014] Optionally, the control system further includes at least one of the following: The second switch control module is used to control the receiving tap switch according to the original position control strategy of the receiving tap switch before the receiving tap switch reaches the over-polarity position. The third switch control module is used to control the receiving-end tap switch according to the original tap position control strategy of the receiving-end tap switch if the tap position adjustment trend meets the second condition after the receiving-end tap switch reaches the over-polarity tap position.

[0015] In summary, the embodiments of this application have at least the following beneficial effects: Using the embodiments of this application, the polarity-crossing position of the receiving-end tap changer is determined based on the positive and negative positions of the converter transformer of the receiving-end tap changer in the high-voltage direct current (HVDC) transmission system; transmission system information corresponding to the HVDC transmission system is obtained; based on the polarity-crossing position, the transmission system information, and the information corresponding to the receiving-end tap changer, the minimum DC voltage at the sending end of the HVDC transmission system under the polarity-crossing position is determined; based on the minimum DC voltage at the sending end, the DC voltage control range is determined; after the receiving-end tap changer reaches the polarity-crossing position, the adjustment trend of the receiving-end tap changer is determined; if the adjustment trend satisfies a first condition, the current DC voltage at the sending end of the HVDC transmission system is obtained in real time; when the current DC voltage at the sending end is within the DC voltage control range, the receiving-end tap changer is controlled to remain at the polarity-crossing position, thereby reducing the number of times the receiving-end tap changer crosses polarity. Attached Figure Description

[0016] Figure 1 This is a flowchart illustrating the control method for the receiving-end tap changer provided in an embodiment of this application; Figure 2 This is a schematic diagram illustrating the approximate relationship between different receiving-end AC voltages and the lowest sending-end DC voltage provided in the embodiments of this application; Figure 3 This is a schematic diagram of the control system of the receiving-end tap changer provided in an embodiment of this application; Figure 4 This is a schematic diagram of the structure of the computer device provided in the embodiments of this application. Detailed Implementation

[0017] 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 of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0018] In the description of this application, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first," "second," "third," etc., may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more. In the description of this application, the term "comprising" and its variations are open-ended, meaning "including but not limited to." The term "based on" means "at least partially based on." The term "according to" means "at least partially according to." The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments."

[0019] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0020] In the description of this application, it should be noted that, unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this application is for the purpose of describing specific embodiments only and is not intended to limit the application. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0021] In some related technologies, it is assumed that the receiving-end tap changer has an original tap position control strategy, which means that the tap position of the receiving-end tap changer is determined by the real-time DC power of the high-voltage direct current transmission system (of course, it can also be determined by other parameters of the high-voltage direct current transmission system, which is not specifically limited here).

[0022] Taking a ±800kV, 6250A, 10000MW high-capacity DC transmission project that has already been put into operation as an example, this type of project generally adopts a design of hierarchical access to the 500kV / 1000kV AC grid. Among them, DC projects connected to the 1000kV grid face a typical problem in actual operation: when the DC power fluctuates within the range of 0.1 to 1.0 pu (pu represents per unit value), the tap changer will frequently switch back and forth within the polarity voltage range. This phenomenon directly affects the equipment life and system stability.

[0023] The following is a detailed analysis of the reasons for this phenomenon. The operating characteristics under the bipolar polarity operation mode with 1050kV at the receiving end, rated DC resistance, are shown in Table 1 (the original gear control strategy can be understood through Table 1 below).

[0024] Table 1 As shown in Table 1 above, the total range of taps for UHVDC converter transformers currently used in engineering projects is 31, and the polarity-crossing taps can be set to 16. Therefore, according to Table 1, the DC power of 0.5 pu is exactly at the polarity-crossing tap. If the actual power operates in this range for a long time, and the AC system voltage fluctuates near the rated AC voltage, it may cause frequent polarity-crossing problems.

[0025] Based on the above, the original gear control strategy can be further explained as follows: the original gear control strategy can be specifically defined as a fixed DC current control strategy at the sending end and a fixed turn-off angle control strategy at the receiving end. The condition for the sending end tap changer to operate is that the trigger angle exceeds the dead zone range of [12.5, 17.5] degrees, and the condition for the receiving end tap changer to operate is that the DC voltage exceeds [+1%U]. dN -1%U dN The range of ], U dN This is the rated DC voltage.

[0026] Furthermore, to reduce the number of tap changer operations, the DC voltage dead zone range can be expanded. Since the upper limit of the DC voltage dead zone should not exceed the equipment's allowable safe voltage (DC long-term continuous operating voltage), its adjustment space is limited. Lowering the lower limit of the DC voltage dead zone does not pose a equipment stress problem. This method allows the tap changer to remain stationary throughout the entire AC voltage fluctuation range, but its drawback is the limitation on DC transmission power. The DC voltage limits for a 10GW UHVDC transmission project using this strategy are shown in Table 2.

[0027] Table 2 After adopting this strategy, although the DC power can be limited to 0.84pu-0.86pu, the DC voltage drops at the same DC power point, the DC current will increase, and the corresponding reactive power consumption will increase. When the overvoltage problem at the sending end is considered when a fault occurs, the DC power will be further compressed. When the DC power is compressed to around 0.5pu, this strategy has the problem of repeated switching on and off, causing the tap changer to frequently change polarity.

[0028] Firstly, see [the following] Figure 1 The diagram shows a flowchart of a control method for a receiving-end tap changer provided in an embodiment of this application. The method includes steps S101-S105, as detailed below.

[0029] S101, Based on the positive and negative commutator positions of the receiving-end tap changer in the high-voltage direct current transmission system, determine the polarity position of the receiving-end tap changer.

[0030] In some examples, it is assumed that the tap position range of the receiving end tap changer is [-A, B], where B is the positive commutation tap and -A is the negative commutation tap. Then, the polarity tap N = (B+A) / 2+1.

[0031] S102, Obtain the power transmission system information corresponding to the high voltage direct current transmission system.

[0032] S103, based on the over-polarity setting, the power transmission system information, and the information corresponding to the receiving end tap changer, determine the minimum DC voltage at the sending end of the high-voltage direct current transmission system under the over-polarity setting.

[0033] S104, Based on the lowest DC voltage at the sending end, determine the DC voltage control range.

[0034] In some examples, the lower limit of the DC voltage control range can be the lowest DC voltage at the sending end, and the upper limit can be the maximum DC voltage at the sending end corresponding to a preset high-voltage DC transmission system.

[0035] S105, after the tap position of the receiving end tap changer reaches the over-polarity position, the adjustment trend of the receiving end tap changer is determined. If the adjustment trend of the tap position meets the first condition, the current DC voltage of the sending end of the high voltage DC transmission system is obtained in real time. When the current DC voltage of the sending end is within the DC voltage control range, the receiving end tap changer is controlled to maintain the over-polarity position.

[0036] In some examples, the corresponding tap position can be determined from the existing tap position control strategy based on the current parameters of the HVDC transmission system. This tap position is then compared with the over-polarity tap position to determine the tap position adjustment trend described in this embodiment. Here, an increasing trend indicates that the tap position determined from the existing tap position control strategy is greater than the over-polarity tap position. In this case, this embodiment will not directly increase the current tap position of the receiving-end tap changer. Instead, after confirming that the relevant conditions are met, the current tap position of the receiving-end tap changer will be maintained at the over-polarity tap position, thereby preventing frequent over-polarity phenomena from occurring in the receiving-end tap changer.

[0037] It is understood that the first condition described in this embodiment may vary depending on the specific definition of the over-polarity gear. For example: (1) If the over-polarity gear is defined as being in the same polarity as a gear smaller than itself, then the first condition means that the gear adjustment trend is characterized by an increasing trend. Therefore, if the gear is increased by one level from the over-polarity gear, the polarity will be crossed and the over-polarity phenomenon will occur. (2) If the over-polarity gear is defined as being in the same polarity as a gear larger than itself, then the first condition means that the gear adjustment trend is characterized by a decreasing trend. Because if the gear is decreased by one level from the over-polarity gear, the polarity will be crossed and the over-polarity phenomenon will occur.

[0038] As can be seen, this embodiment maintains the current position of the receiving-end tap changer at the over-polarity position when the relevant conditions are met. This ensures that the receiving-end tap changer always maintains the same polarity and does not cross polarity, thereby avoiding frequent over-polarity phenomena in the receiving-end tap changer and ensuring the safety and normal operation of the high-voltage direct current transmission system.

[0039] In the following sections of this application, examples will be given exemplified by the case where the polarity of the gear is defined as being in the same polarity as a gear with a lower polarity.

[0040] In practical applications, when the voltage of the AC system at the receiving end changes, the control power range can be divided into a risky over-polarity segment and a stable operation segment.

[0041] Over-polarity risk zone (power ≤ Ppol): Use the original gear control strategy to avoid over-polarity operation of the tap changer.

[0042] Stable operation segment (Pmax≥Power>Ppol): Execute segmented voltage control logic, that is, allow DC voltage to fluctuate within a wide range (DC voltage control range), and control the tap changer at the receiving end to remain in the over-polarity position.

[0043] Here, Ppol represents the over-polarity power point, that is, the real-time DC power corresponding to when the tap changer at the receiving end is exactly in the over-polarity position according to the original tap control strategy. Ppol can be determined based on the real-time voltage level of the AC system at the receiving end (e.g., ±5% fluctuation range of rated voltage) combined with the over-polarity position. Pmax represents the power corresponding to the full-power position.

[0044] Thus, by determining the DC voltage control range by the lowest DC voltage at the sending end, it can be ensured that the lower limit of the DC voltage control range can meet the dual constraints: that is, to prevent the tap changer from frequently crossing the polarity critical point in the low power range, and to ensure that the DC system maintains a stable voltage margin in the high power range.

[0045] Once the polarity setting is reached, a fixed setting is used to cover subsequent scenarios with higher DC power. The AC system voltage is also set to 1050kV, rated DC resistance, and bipolar polarity operation.

[0046] In one optional implementation, the power transmission system information includes first configuration information and actual operating current of the high-voltage direct current transmission system, and also includes second configuration information and receiving-end AC voltage of the receiving-end AC system in the high-voltage direct current transmission system. The information corresponding to the receiving-end tap changer includes the rated turns ratio of the converter transformer corresponding to the receiving-end tap changer; The determination of the minimum DC voltage at the sending end of the high-voltage direct current transmission system under the over-polarity position, based on the over-polarity position, the transmission system information, and the information corresponding to the receiving-end tap changer, includes: Based on the AC voltage at the receiving end, the rated transformer ratio, and the polarity setting, determine the ideal no-load DC voltage at the receiving end; Based on the second configuration information, the first configuration information and actual operating current of the high-voltage direct current transmission system, and the ideal no-load DC voltage of the receiving end, the ideal DC voltage of the high-voltage direct current transmission system is determined. Based on the ideal DC voltage of the high-voltage direct current transmission system, the first configuration information, and the actual operating current, the minimum DC voltage at the sending end is determined.

[0047] In some examples, the formula for calculating the ideal no-load DC voltage at the receiving end may include: Among them, U s n is the AC voltage at the receiving end. nom For the rated ratio, U di0I The ideal open-circuit DC voltage is denoted by N, which is the polarity setting.

[0048] in, U sN and U vN The values ​​are, in order, the actual effective values ​​of AC voltage on the grid side and valve side of the receiving-end AC system.

[0049] In some examples, typical values ​​for the receiving-end AC voltage and its corresponding current rating of the receiving-end AC system can be found in Table 3 below.

[0050] Table 3 Current rating / A 5000 6250 In one optional implementation, the first configuration information includes the pulse number, rated DC current, and forward conduction voltage drop of the converter valve of the high voltage direct current transmission system, and the second configuration information includes the turn-off angle, per-unit value of inductor voltage drop, per-unit value of resistor voltage drop, and rated ideal no-load DC voltage of the receiving-end AC system. The step of determining the ideal DC voltage of the high-voltage direct current transmission system based on the second configuration information, the first configuration information and actual operating current of the high-voltage direct current transmission system, and the ideal no-load DC voltage at the receiving end includes: Based on the pulse number, actual operating current, rated DC current, and forward conduction voltage drop of the converter valve of the high-voltage direct current transmission system, the shut-off angle, per-unit value of inductor voltage drop, per-unit value of resistor voltage drop, and rated ideal no-load DC voltage of the receiving-end AC system, and the ideal no-load DC voltage of the receiving end, the ideal DC voltage of the high-voltage direct current transmission system is determined.

[0051] In some examples, the formula for calculating the ideal DC voltage of the aforementioned high-voltage direct current transmission system may include: Among them, U dI U is the ideal DC voltage of the high-voltage direct current transmission system, n is the pulsation number, and U is the voltage of the high-voltage direct current transmission system. di0I Let γ be the ideal open-circuit DC voltage at the receiving end, d be the turn-off angle, and d be the voltage at the receiving end. xI d is the per-unit value of the inductor voltage drop. rI I is the per-unit value of the resistor voltage drop. d I represents the actual operating current of the high-voltage direct current transmission system. dN For the rated DC current, U dioNI U is the rated ideal no-load DC voltage. T This refers to the forward conduction pressure drop of the converter valve.

[0052] In one optional implementation, the first configuration information includes the DC resistance of the high-voltage direct current transmission system; determining the minimum DC voltage at the sending end based on the ideal DC voltage of the high-voltage direct current transmission system, the first configuration information, and the actual operating current includes: Based on the ideal DC voltage, DC resistance, and actual operating current of the high-voltage direct current transmission system, the minimum DC voltage at the sending end is determined.

[0053] In some examples, the formula for calculating the minimum DC voltage at the sending end mentioned above may include: U dR =U dI +I d ·R d Among them, U dR U is the minimum DC voltage at the sending end. dIFor the ideal DC voltage of a high-voltage direct current transmission system, I d R represents the actual operating current of the high-voltage direct current transmission system. d The DC resistance of the high-voltage direct current transmission system can be pre-configured and is not specifically limited here.

[0054] in, Among them, P dR This indicates the DC power at the sending end.

[0055] In some examples, combining the calculation formulas of the above-mentioned related embodiments, different receiving-end AC voltages U s With the lowest DC voltage U at the sending end dR For a general understanding of their relationship, please refer to [link / reference]. Figure 2 .

[0056] In one optional implementation, the power transmission system information includes the rated DC voltage and real-time DC power of the high-voltage direct current (HVDC) transmission system, and the information corresponding to the receiving-end tap changer includes the original tap position control strategy of the receiving-end tap changer, wherein the original tap position control strategy refers to the tap position of the receiving-end tap changer being determined by the real-time DC power; determining the minimum sending-end DC voltage of the HVDC transmission system at the over-polarity tap position, based on the over-polarity tap position, the power transmission system information, and the information corresponding to the receiving-end tap changer, includes: Based on the original gear control strategy and the real-time DC power, the original strategy gear of the receiving end tap changer is determined; based on the original strategy gear, the polarity gear, and the rated DC voltage, the minimum DC voltage of the sending end is determined.

[0057] In some examples, the formula for calculating the minimum DC voltage at the sending end mentioned above may include: Among them, U dN K is the rated DC voltage, and K is the tap changer position difference between the original strategy position and the over-polarity position.

[0058] In one alternative implementation, the method further includes at least one of the following: Before the tap position of the receiving end tap switch reaches the over-polarity position, the receiving end tap switch is controlled according to the original position control strategy of the receiving end tap switch. After the tap changer reaches the over-polarity position, if the position adjustment trend meets the second condition, the tap changer is controlled according to the original position control strategy of the tap changer.

[0059] In some examples, the original tap position control strategy means that the tap position of the receiving-end tap changer is determined by the real-time DC power.

[0060] In some examples, the second condition corresponds to the first condition mentioned above. For example, if the first condition refers to a gear adjustment trend that is characterized as an increasing trend, then the second condition refers to a gear adjustment trend that is characterized as a decreasing trend; if the first condition refers to a gear adjustment trend that is characterized as a decreasing trend, then the second condition refers to a gear adjustment trend that is characterized as an increasing trend.

[0061] In conjunction with the relevant embodiments provided in the first aspect above, some specific examples are further given to illustrate this application, so as to better understand the relevant technical effects of this application. The parameter settings of this specific example can be referred to Table 4 below. Wherein, the AC system voltage corresponding to the data shown in Table 4 is 1050kV.

[0062] Table 4 As shown in Table 4 above, the voltage level does not increase after reaching 16. In this embodiment, if the maximum DC power is 7000MW, the minimum DC voltage control range is 787.77kV, i.e., 98%U. dN If the maximum DC power is 10000MW, then the minimum DC voltage control range is 766.14kV, or 95% u. dN .

[0063] Furthermore, taking a 10GW UHVDC project as an example, a segmented tap changer control strategy is formulated based on different AC voltages. That is, after the tap changer reaches the polarity over-range position, it is always kept at that position without change, so that the tap changer position is on one side of the range of AC system voltage and DC power, which greatly reduces the number of times the tap changer goes through polarity.

[0064] The following table shows the cases where the AC system voltage is 1000kV-1085kV.

[0065] Table 5 By employing the relevant embodiments of this application, one or more of the following beneficial effects can be achieved.

[0066] 1. It can make full use of the polarity characteristics of the converter transformer tap changer, and concentrate the tap adjustment on one side according to the relationship between DC power and tap position in DC system, thereby reducing the number of times the polarity is changed.

[0067] 2. It can determine the range of tap change based on the AC system voltage and DC power requirements, and set segmented tap control to meet the tap changer operation optimization requirements under precise voltage and power conditions in engineering projects.

[0068] 3. By reducing the number of times the tap changer changes polarity, the safe and reliable operation of the converter transformer can be ensured, and the operational safety and reliability of the converter station can be further improved.

[0069] Secondly, correspondingly, the embodiments of this application also provide a control system for a receiving-end tap changer, which can implement all the processes of the control method for the receiving-end tap changer provided in the above embodiments.

[0070] See Figure 3 This diagram illustrates the structure of a control system for a receiving-end tap changer provided in an embodiment of this application. The control system for the receiving-end tap changer includes: The position determination module 301 is used to determine the polarity position of the receiving-end tap changer based on the positive and negative positions of the converter transformer of the receiving-end tap changer in the high-voltage direct current transmission system. The power transmission system information acquisition module 302 is used to acquire the power transmission system information corresponding to the high voltage direct current power transmission system; The sending-end minimum DC voltage determination module 303 is used to determine the sending-end minimum DC voltage of the high-voltage DC transmission system under the polarity crossing position based on the polarity crossing position, the transmission system information, and the information corresponding to the receiving-end tap changer; the voltage range determination module 304 is used to determine the DC voltage control range based on the sending-end minimum DC voltage. The first switch control module 305 is used to determine the adjustment trend of the tap position of the receiving end tap switch after the receiving end tap position reaches the over-polarity position. If the adjustment trend of the tap position meets the first condition, the current DC voltage of the sending end of the high voltage DC transmission system is obtained in real time. When the current DC voltage of the sending end is within the DC voltage control range, the receiving end tap switch is controlled to maintain the over-polarity position.

[0071] In one optional implementation, the power transmission system information includes first configuration information and actual operating current of the high-voltage direct current transmission system, and also includes second configuration information and receiving-end AC voltage of the receiving-end AC system in the high-voltage direct current transmission system. The information corresponding to the receiving-end tap changer includes the rated turns ratio of the converter transformer corresponding to the receiving-end tap changer; The determination of the minimum DC voltage at the sending end of the high-voltage direct current transmission system under the over-polarity position, based on the over-polarity position, the transmission system information, and the information corresponding to the receiving-end tap changer, includes: Based on the AC voltage at the receiving end, the rated transformer ratio, and the polarity setting, determine the ideal no-load DC voltage at the receiving end; Based on the second configuration information, the first configuration information and actual operating current of the high-voltage direct current transmission system, and the ideal no-load DC voltage of the receiving end, the ideal DC voltage of the high-voltage direct current transmission system is determined. Based on the ideal DC voltage of the high-voltage direct current transmission system, the first configuration information, and the actual operating current, the minimum DC voltage at the sending end is determined.

[0072] In one optional implementation, the first configuration information includes the pulse number, rated DC current, and forward conduction voltage drop of the converter valve of the high voltage direct current transmission system, and the second configuration information includes the turn-off angle, per-unit value of inductor voltage drop, per-unit value of resistor voltage drop, and rated ideal no-load DC voltage of the receiving-end AC system. The step of determining the ideal DC voltage of the high-voltage direct current transmission system based on the second configuration information, the first configuration information and actual operating current of the high-voltage direct current transmission system, and the ideal no-load DC voltage at the receiving end includes: Based on the pulse number, actual operating current, rated DC current, and forward conduction voltage drop of the converter valve of the high-voltage direct current transmission system, the shut-off angle, per-unit value of inductor voltage drop, per-unit value of resistor voltage drop, and rated ideal no-load DC voltage of the receiving-end AC system, and the ideal no-load DC voltage of the receiving end, the ideal DC voltage of the high-voltage direct current transmission system is determined.

[0073] In one optional implementation, the first configuration information includes the DC resistance of the high-voltage direct current transmission system; determining the minimum DC voltage at the sending end based on the ideal DC voltage of the high-voltage direct current transmission system, the first configuration information, and the actual operating current includes: Based on the ideal DC voltage, DC resistance, and actual operating current of the high-voltage direct current transmission system, the minimum DC voltage at the sending end is determined.

[0074] In one optional implementation, the power transmission system information includes the rated DC voltage and real-time DC power of the high-voltage direct current (HVDC) transmission system, and the information corresponding to the receiving-end tap changer includes the original tap position control strategy of the receiving-end tap changer, wherein the original tap position control strategy refers to the tap position of the receiving-end tap changer being determined by the real-time DC power; determining the minimum sending-end DC voltage of the HVDC transmission system at the over-polarity tap position, based on the over-polarity tap position, the power transmission system information, and the information corresponding to the receiving-end tap changer, includes: Based on the original gear control strategy and the real-time DC power, the original strategy gear of the receiving end tap changer is determined; based on the original strategy gear, the polarity gear, and the rated DC voltage, the minimum DC voltage of the sending end is determined.

[0075] In one alternative implementation, the control system further includes at least one of the following: The second switch control module is used to control the receiving tap switch according to the original position control strategy of the receiving tap switch before the receiving tap switch reaches the over-polarity position. The third switch control module is used to control the receiving-end tap switch according to the original tap position control strategy of the receiving-end tap switch if the tap position adjustment trend meets the second condition after the receiving-end tap switch reaches the over-polarity tap position.

[0076] Thirdly, embodiments of this application provide a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of any of the control methods described above.

[0077] Fourthly, embodiments of this application provide a computer program product, including computer instructions that, when executed by a processor, implement the steps of the control method described in any of the preceding claims.

[0078] Fifthly, embodiments of this application provide a computer device including a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein the processor executes the computer program to implement the steps of the control method described in any of the preceding claims.

[0079] See Figure 4 The computer device in this embodiment includes a processor 401, a memory 402, and a computer program, such as a control program, stored in the memory 402 and executable on the processor 401. When the processor 401 executes the computer program, it implements the steps in the various control method embodiments described above, for example... Figure 1 The steps S101-S105 are shown.

[0080] For example, the computer program may be divided into one or more modules / units, which are stored in the memory 402 and executed by the processor 401 to complete this application. The one or more modules / units may be a series of computer program instruction segments capable of performing a specific function, which describe the execution process of the computer program in the computer device.

[0081] The computer device may be a desktop computer, laptop, handheld computer, or cloud server, etc. The computer device may include, but is not limited to, a processor 401 and a memory 402. Those skilled in the art will understand that the schematic diagram is merely an example of a computer device and does not constitute a limitation on the computer device. It may include more or fewer components than shown, or combine certain components, or different components. For example, the computer device may also include input / output devices, network access devices, buses, etc.

[0082] The processor 401 can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor, or processor 401 can be any conventional processor. The processor 401 is the control center of the computer device, connecting various parts of the entire computer device through various interfaces and lines.

[0083] The memory 402 can be used to store the computer programs and / or modules. The processor 401 implements various functions of the computer device by running or executing the computer programs and / or modules stored in the memory 402 and calling the data stored in the memory 402. The memory 402 may mainly include a program storage area and a data storage area. The program storage area may store the operating system, at least one application program required for a function (such as sound playback function, image playback function, etc.), etc.; the data storage area may store data created according to the use of the mobile phone (such as audio data, phonebook, etc.). In addition, the memory 402 may include high-speed random access memory, and may also include non-volatile memory, such as hard disk, memory, plug-in hard disk, smart media card (SMC), secure digital card (SD) card, flash card, at least one disk storage device, flash memory device, or other volatile solid-state storage device.

[0084] Wherein, if the modules / units integrated into the computer device are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by the processor 401, it can implement the steps of the various method embodiments described above. Wherein, the computer program includes computer program code, which can be in the form of source code, object code, executable file, or some intermediate form, etc. The computer-readable medium can include: any entity or device capable of carrying the computer program code, recording medium, USB flash drive, portable hard drive, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signal, telecommunication signal, and software distribution medium, etc.

[0085] In summary, the embodiments of this application have at least the following beneficial effects: Using the embodiments of this application, the polarity-crossing position of the receiving-end tap changer is determined based on the positive and negative positions of the converter transformer of the receiving-end tap changer in the high-voltage direct current (HVDC) transmission system; transmission system information corresponding to the HVDC transmission system is obtained; based on the polarity-crossing position, the transmission system information, and the information corresponding to the receiving-end tap changer, the minimum DC voltage at the sending end of the HVDC transmission system under the polarity-crossing position is determined; based on the minimum DC voltage at the sending end, the DC voltage control range is determined; after the receiving-end tap changer reaches the polarity-crossing position, the adjustment trend of the receiving-end tap changer is determined; if the adjustment trend satisfies a first condition, the current DC voltage at the sending end of the HVDC transmission system is obtained in real time; when the current DC voltage at the sending end is within the DC voltage control range, the receiving-end tap changer is controlled to remain at the polarity-crossing position, thereby reducing the number of times the receiving-end tap changer crosses polarity.

[0086] Through the above description of the embodiments, those skilled in the art can clearly understand that this application can be implemented by means of software plus necessary hardware platforms, or it can be implemented entirely by hardware. Based on this understanding, all or part of the technical solutions of this application that contribute to the background technology can be embodied in the form of a software product. This computer software product can be stored in a storage medium, such as ROM (Read-Only Memory) / RAM (Random Access Memory), magnetic disk, optical disk, etc., including several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in various embodiments or some parts of the embodiments of this application.

[0087] The above description is the preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications are also considered to be within the scope of protection of this application.

Claims

1. A control method for a receiving-end tap changer, characterized in that, include: Based on the positive and negative commutator positions of the receiving-end tap changer in the high-voltage direct current transmission system, the polarity-crossing position of the receiving-end tap changer is determined. The range of the receiving-end tap changer is [-A, B], where B is the positive commutator position and -A is the negative commutator position. Then, the polarity-crossing position N = (B+A) / 2+1. Obtain the power transmission system information corresponding to the high-voltage direct current transmission system; Based on the polarity switch, the power transmission system information, and the information corresponding to the receiving end tap changer, the minimum DC voltage at the sending end of the high voltage DC transmission system under the polarity switch is determined. The DC voltage control range is determined based on the lowest DC voltage at the sending end; After the tap position of the receiving end tap changer reaches the over-polarity position, the adjustment trend of the receiving end tap changer is determined. If the adjustment trend of the tap changer meets the first condition, the current DC voltage of the sending end of the high voltage DC transmission system is obtained in real time. When the current DC voltage of the sending end is within the DC voltage control range, the receiving end tap changer is controlled to maintain the over-polarity position. Wherein, if the over-polarity gear is defined as being in the same polarity as a gear of lesser polarity, then the first condition means that the gear adjustment trend is characterized as an increasing trend; if the over-polarity gear is defined as being in the same polarity as a gear of greater polarity, then the first condition means that the gear adjustment trend is characterized as a decreasing trend.

2. The method according to claim 1, characterized in that, The power transmission system information includes the first configuration information and actual operating current of the high-voltage direct current transmission system, as well as the second configuration information and receiving-end AC voltage of the receiving-end AC system in the high-voltage direct current transmission system; The information corresponding to the receiving-end tap changer includes the rated turns ratio of the converter transformer corresponding to the receiving-end tap changer; The determination of the minimum DC voltage at the sending end of the high-voltage direct current transmission system under the polarity-crossing position, based on the polarity-crossing position, the transmission system information, and the information corresponding to the receiving-end tap changer, includes: Based on the AC voltage at the receiving end, the rated transformer ratio, and the polarity setting, determine the ideal no-load DC voltage at the receiving end; Based on the second configuration information, the first configuration information and actual operating current of the high-voltage direct current transmission system, and the ideal no-load DC voltage at the receiving end, the ideal DC voltage of the high-voltage direct current transmission system is determined. Based on the ideal DC voltage of the high-voltage direct current transmission system, the first configuration information, and the actual operating current, the minimum DC voltage at the sending end is determined.

3. The method according to claim 2, characterized in that, The first configuration information includes the pulse number, rated DC current and forward conduction voltage drop of the converter valve of the high voltage DC transmission system; the second configuration information includes the turn-off angle, per-unit value of inductor voltage drop, per-unit value of resistor voltage drop and rated ideal no-load DC voltage of the receiving-end AC system. The step of determining the ideal DC voltage of the high-voltage direct current transmission system based on the second configuration information, the first configuration information and actual operating current of the high-voltage direct current transmission system, and the ideal no-load DC voltage at the receiving end includes: Based on the pulse number, actual operating current, rated DC current, and forward conduction voltage drop of the converter valve of the high-voltage direct current transmission system, the shut-off angle, per-unit value of inductor voltage drop, per-unit value of resistor voltage drop, and rated ideal no-load DC voltage of the receiving-end AC system, and the ideal no-load DC voltage of the receiving end, the ideal DC voltage of the high-voltage direct current transmission system is determined.

4. The method according to claim 2, characterized in that, The first configuration information includes the DC resistance of the high-voltage direct current transmission system; The determination of the minimum DC voltage at the sending end based on the ideal DC voltage of the high-voltage direct current transmission system, the first configuration information, and the actual operating current includes: Based on the ideal DC voltage, DC resistance, and actual operating current of the high-voltage direct current transmission system, the minimum DC voltage at the sending end is determined.

5. The method according to claim 1, characterized in that, The power transmission system information includes the rated DC voltage and real-time DC power of the high-voltage direct current transmission system. The information corresponding to the receiving-end tap changer includes the original tap position control strategy of the receiving-end tap changer. The original tap position control strategy means that the tap position of the receiving-end tap changer is determined by the real-time DC power. The determination of the minimum DC voltage at the sending end of the high-voltage direct current transmission system under the polarity-crossing position, based on the polarity-crossing position, the transmission system information, and the information corresponding to the receiving-end tap changer, includes: Based on the original gear control strategy and the real-time DC power, the original strategy gear of the receiving end tap changer is determined. Based on the original strategy level, the polarity level, and the rated DC voltage, the minimum DC voltage at the sending end is determined.

6. The method according to any one of claims 1-5, characterized in that, The method further includes at least one of the following: Before the tap position of the receiving end tap switch reaches the over-polarity position, the receiving end tap switch is controlled according to the original position control strategy of the receiving end tap switch. After the tap position of the receiving end tap switch reaches the over-polarity position, if the position adjustment trend meets the second condition, the receiving end tap switch is controlled according to the original position control strategy of the receiving end tap switch. Wherein, if the first condition refers to the gear adjustment trend being characterized as an increasing trend, then the second condition refers to the gear adjustment trend being characterized as a decreasing trend; if the first condition refers to the gear adjustment trend being characterized as a decreasing trend, then the second condition refers to the gear adjustment trend being characterized as an increasing trend.

7. A control system for a receiving-end tap changer, characterized in that, include: The tap position determination module is used to determine the polarity tap position of the receiving-end tap switch based on the positive and negative tap positions of the converter transformer in the receiving-end tap switch of the high-voltage direct current transmission system. The tap position range of the receiving-end tap switch is [-A, B], where B is the positive tap position of the converter transformer and -A is the negative tap position of the converter transformer. Then the polarity tap position N = (B+A) / 2+1. The power transmission system information acquisition module is used to acquire the power transmission system information corresponding to the high voltage direct current transmission system; The sending-end minimum DC voltage determination module is used to determine the sending-end minimum DC voltage of the high-voltage DC transmission system under the over-polarity position based on the over-polarity position, the transmission system information, and the information corresponding to the receiving-end tap changer. The voltage range determination module is used to determine the DC voltage control range based on the lowest DC voltage at the sending end; The first switch control module is used to determine the adjustment trend of the tap position of the receiving end tap switch after the receiving end tap position reaches the over-polarity position. If the adjustment trend of the tap position meets the first condition, the current DC voltage of the sending end of the high voltage DC transmission system is obtained in real time. When the current DC voltage of the sending end is within the DC voltage control range, the receiving end tap switch is controlled to maintain the over-polarity position. Wherein, if the over-polarity gear is defined as being in the same polarity as a gear of lesser polarity, then the first condition means that the gear adjustment trend is characterized as an increasing trend; if the over-polarity gear is defined as being in the same polarity as a gear of greater polarity, then the first condition means that the gear adjustment trend is characterized as a decreasing trend.

8. The control system according to claim 7, characterized in that, The power transmission system information includes the first configuration information and actual operating current of the high-voltage direct current transmission system, as well as the second configuration information and receiving-end AC voltage of the receiving-end AC system in the high-voltage direct current transmission system; The information corresponding to the receiving-end tap changer includes the rated turns ratio of the converter transformer corresponding to the receiving-end tap changer; The determination of the minimum DC voltage at the sending end of the high-voltage direct current transmission system under the polarity-crossing position, based on the polarity-crossing position, the transmission system information, and the information corresponding to the receiving-end tap changer, includes: Based on the AC voltage at the receiving end, the rated transformer ratio, and the polarity setting, determine the ideal no-load DC voltage at the receiving end; Based on the second configuration information, the first configuration information and actual operating current of the high-voltage direct current transmission system, and the ideal no-load DC voltage at the receiving end, the ideal DC voltage of the high-voltage direct current transmission system is determined. Based on the ideal DC voltage of the high-voltage direct current transmission system, the first configuration information, and the actual operating current, the minimum DC voltage at the sending end is determined.

9. The control system according to claim 7, characterized in that, The power transmission system information includes the rated DC voltage and real-time DC power of the high-voltage direct current transmission system. The information corresponding to the receiving-end tap changer includes the original tap position control strategy of the receiving-end tap changer. The original tap position control strategy means that the tap position of the receiving-end tap changer is determined by the real-time DC power. The determination of the minimum DC voltage at the sending end of the high-voltage direct current transmission system under the polarity-crossing position, based on the polarity-crossing position, the transmission system information, and the information corresponding to the receiving-end tap changer, includes: Based on the original gear control strategy and the real-time DC power, the original strategy gear of the receiving end tap changer is determined. Based on the original strategy level, the polarity level, and the rated DC voltage, the minimum DC voltage at the sending end is determined.

10. The control system according to any one of claims 7-9, characterized in that, The control system further includes at least one of the following: The second switch control module is used to control the receiving tap switch according to the original position control strategy of the receiving tap switch before the receiving tap switch reaches the over-polarity position. The third switch control module is used to control the receiving tap switch according to the original position control strategy of the receiving tap switch after the receiving tap switch reaches the over-polarity position, if the position adjustment trend meets the second condition. Wherein, if the first condition refers to the gear adjustment trend being characterized as an increasing trend, then the second condition refers to the gear adjustment trend being characterized as a decreasing trend; if the first condition refers to the gear adjustment trend being characterized as a decreasing trend, then the second condition refers to the gear adjustment trend being characterized as an increasing trend.

Images