Control method and device of flexible direct current system, computer storage medium, electronic equipment and computer program product

Abstract

The invention provides a control method and device of a flexible direct current system, a computer storage medium, electronic equipment and a computer program product. The control method of the flexible direct current system comprises the following steps: monitoring the valve side voltage of the flexible direct current system; determining a valve side voltage difference according to the valve side voltage and a valve side voltage preset value; determining the correction amount of reactive power according to the valve side voltage difference under the condition that the valve side voltage difference is determined to meet the preset range; generating a control instruction according to the correction amount; and according to the control instruction, reactive power is emitted or absorbed, so that the valve side voltage meets the target value of the valve side voltage.

Description

Control methods, devices, computer storage media, electronic equipment, and computer program products for flexible DC systems Technical Field

[0001] This application relates to the field of power control technology, and more specifically, to a control method, device, computer storage medium, electronic equipment, and computer program product for a flexible DC system. Background Technology

[0002] In a flexible DC system (Voltage Source Converter High Voltage Direct Current, VSC-HVDC), a converter transformer typically connects the DC line converter to the AC line. The converter transformer provides electrical isolation between the AC and DC lines, matches the AC voltage to the DC voltage, and optimizes the modulation ratio. By adjusting the on-load tap changer, the valve-side voltage can be matched to the DC voltage. As the operating conditions of the DC lines in the DC grid change, or as the DC or AC voltage fluctuates, the valve-side voltage needs to be adjusted to the designed normal operating state. Therefore, adjusting the on-load tap changer is necessary to regulate the valve-side voltage value.

[0003] However, the inventors of this application have discovered that under normal operating conditions, flexible DC systems require frequent adjustments of the on-load tap changer to meet the converter modulation ratio. This necessitates that the on-load tap changer maintain low maintenance or high energy efficiency even after numerous operations. For example, the insulation medium of the on-load tap changer should be able to quickly recover its insulation strength and rapidly extinguish the arc to prevent reignition.

[0004] Existing on-load tap changers for converter transformers generally employ a combination of tap selector and switching switch, which presents challenges in manufacturing and results in a large number of components. Furthermore, a single malfunction of the on-load tap changer can easily lead to the escalation of the fault, ultimately damaging the converter transformer. Summary of the Invention

[0005] According to one aspect of this application, a control method for a flexible DC system is provided. The control method includes: monitoring the valve-side voltage of the flexible DC system; determining the valve-side voltage difference based on the valve-side voltage and a preset valve-side voltage value; determining a reactive power correction amount based on the valve-side voltage difference if the valve-side voltage difference meets a preset range; generating a control command based on the correction amount; and issuing or absorbing reactive power according to the control command to ensure that the valve-side voltage meets a target value.

[0006] According to some embodiments of this application, the correction amount is proportional to the voltage difference on the valve side.

[0007] According to some embodiments of this application, the correction amount is integrally related to the valve-side voltage difference.

[0008] According to some embodiments of this application, the correction amount is proportional to the valve-side voltage difference.

[0009] According to some embodiments of this application, when it is determined that the valve-side voltage difference meets a preset range, the step of determining the correction amount of reactive power based on the valve-side voltage difference may include: when it is determined that the valve-side voltage difference meets a first preset range, determining a first correction amount of the valve-side voltage based on the valve-side voltage difference; or when it is determined that the valve-side voltage difference meets a second preset range, determining a second correction amount of the valve-side voltage based on the valve-side voltage difference. The step of generating a control command based on the correction amount may include: generating a first control command based on the first correction amount; or generating a second control command based on the second correction amount. The step of issuing or absorbing reactive power based on the control command to make the valve-side voltage meet the target value of the valve-side voltage may include: issuing reactive power based on the first control command to make the valve-side voltage meet the target value of the valve-side voltage; or absorbing reactive power based on the second control command to make the valve-side voltage meet the target value of the valve-side voltage.

[0010] According to some embodiments of this application, after determining the correction amount of reactive power based on the valve-side voltage difference when the valve-side voltage difference meets the preset range, the control method may further include: when the correction amount of reactive power meets the preset correction range, generating a control command and a third control command based on the correction amount; issuing or absorbing reactive power based on the control command; and sending the third control command to adjust the on-load tap changer to make the valve-side voltage meet the target value of the valve-side voltage.

[0011] According to another aspect of this application, a control device for a flexible DC system is also provided, comprising a converter and a control unit. The converter monitors the valve-side voltage of the flexible DC system; the control unit determines the valve-side voltage difference based on the valve-side voltage and a preset valve-side voltage value; if the valve-side voltage difference meets a preset range, the control unit determines a reactive power correction amount based on the valve-side voltage difference; the control unit generates and transmits control commands based on the correction amount; the converter, according to the control commands, generates or absorbs reactive power to ensure that the valve-side voltage meets the target value.

[0012] According to some embodiments of this application, the control unit further determines that if the correction amount meets the preset correction range, it generates a control command and a third control command based on the correction amount; the converter further issues or absorbs reactive power according to the control command; the control unit further sends a third control command to cause the on-load tap changer to adjust its position, thereby causing the valve-side voltage to meet the target value of the valve-side voltage.

[0013] According to one aspect of this application, this application also provides a non-volatile computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, can implement a control method for a flexible DC system as described above.

[0014] According to one aspect of this application, this application also provides an electronic device, including: one or more processors; and a storage device for storing one or more programs, which, when executed by one or more processors, enable the one or more processors to implement a control method for a flexible DC system as described above.

[0015] According to one aspect of this application, this application also provides a computer program product, comprising: a computer program stored on a computer-readable storage medium; the computer program includes program instructions that, when executed by a computer, cause the computer to perform a control method for a flexible DC system as described above.

[0016] Through the above embodiments, this application utilizes the flexible adjustment capability of the converter's reactive power to regulate the valve-side voltage of the converter transformer to meet the target value of the valve-side voltage. Thus, the regulation of the converter replaces the regulation of the on-load tap changer.

[0017] This application can reduce the operational risks of converter transformers by avoiding the mechanical operation of the on-load tap changer when repeated on-load adjustments are required. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 shows a flowchart of a control method 1000 for a flexible DC system according to an embodiment of this application;

[0020] Figure 2 shows a schematic diagram of the structure of a flexible DC system of a bipolar converter according to an embodiment of this application;

[0021] Figure 3 shows a flowchart of step S130 according to an embodiment of the present application;

[0022] Figure 4 shows a flowchart of step S140 according to an embodiment of this application;

[0023] Figure 5 shows a flowchart of step S150 according to an embodiment of this application;

[0024] Figure 6 shows a flowchart of a control method 2000 for a flexible DC system according to an embodiment of this application;

[0025] Figure 7 shows a schematic diagram of the structure of a control device 300 for a flexible DC system according to an embodiment of this application.

[0026] Explanation of reference numerals in the attached figures:

[0027] The flexible DC system includes a control device 300, a converter 301, and a control unit 302. Detailed Implementation

[0028] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, they are provided so that this application will be thorough and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions of them will be omitted.

[0029] The described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a full understanding of embodiments of this disclosure. However, those skilled in the art will recognize that the technical solutions of this disclosure can be practiced without one or more of these specific details, or other methods, components, materials, devices, etc. In these cases, well-known structures, methods, devices, implementations, materials, or operations will not be shown or described in detail.

[0030] Furthermore, the terms “comprising” and “having”, and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the steps or units listed, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to such process, method, product, or apparatus.

[0031] The terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish different objects, not to describe a specific order.

[0032] The technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0033] According to one aspect of this application, a control method 1000 for a flexible DC system is provided. Referring to FIG1, the control method 1000 includes steps S110-S150. Exemplarily, the control method 1000 can be executed by a control device for a flexible DC system.

[0034] In step S110, the valve-side voltage of the flexible DC system is monitored.

[0035] According to the example embodiments, the flexible DC system can be a single-pole connection structure, a double-pole connection structure, or a high-low valve group multi-converter structure.

[0036] For example, referring to Figure 2, the flexible DC system has a bipolar connection structure, including a connection structure for pole 1 and a connection structure for pole 2.

[0037] Each connection structure of a flexible DC system includes an AC line, a converter transformer, a converter, and a DC line. Switches can be installed on both the AC and DC lines to control the connection status of the lines.

[0038] For example, referring to Figure 2, the wiring structure of pole 1 includes AC line 1, pole 1 converter transformer T1, pole 1 converter, and pole 1 DC line; the wiring structure of pole 2 includes AC line 2, pole 2 converter transformer T2, pole 2 converter, and pole 2 DC line. Each converter transformer in each wiring structure can transform the grid-side voltage US into the valve-side voltage UV according to a preset turns ratio. The converter converts the valve-side voltage into DC voltage.

[0039] According to the example embodiment, the grid-side voltage can be the AC voltage at the bus connection point of the converter transformer to the AC line. The valve-side voltage can be the voltage between the converter transformer and the converter, which is the AC voltage converted from the grid-side voltage by the converter transformer according to a certain turns ratio. The converter can be a flexible high-voltage direct current (HVDC) converter.

[0040] For example, referring to Figure 2, in step S110, the control device can monitor the valve-side voltage of the flexible DC system through the flexible DC converter.

[0041] According to the example embodiment, the control device can monitor the valve-side voltage of the flexible DC system in real time, or the control system can monitor the valve-side voltage of the flexible DC system at a certain frequency.

[0042] In step S120, the valve side voltage difference is determined based on the valve side voltage and the preset valve side voltage value.

[0043] According to the example embodiment, the preset value of the valve-side voltage can be preset according to user requirements. For example, the preset value of the valve-side voltage can be the voltage value within the normal adjustment range of the valve-side voltage. The preset value of the valve-side voltage can be set according to the parameters of the primary equipment of the flexible DC system so that the modulation ratio of the converter meets the operating requirements of the converter, and so that the valve-side voltage and the DC voltage output by the converter meet the operating requirements of the converter.

[0044] In step S120, the control device can determine the valve-side voltage difference according to the following formula:

[0045] △UV = UV - UV_REF;

[0046] Where △UV is the valve-side voltage difference, UV is the valve-side voltage, and UV_REF is the preset value of the valve-side voltage.

[0047] In step S130, if it is determined that the valve-side voltage difference meets the preset range, the correction amount of reactive power is determined based on the valve-side voltage difference.

[0048] According to the example embodiment, the preset range can be the deviation range of the valve-side voltage difference when the actual value of the valve-side voltage is not in normal operating condition. When the actual value of the valve-side voltage is in normal operating condition, the flexible DC converter can be in reactive power control mode or AC voltage control mode. The reactive power absorbed or generated by the flexible DC converter is not affected by the valve-side voltage.

[0049] For example, referring to Figure 2, when the actual voltage value of the valve side voltage is under normal operating conditions, the range of the valve side voltage difference can be △UV_set1≤△UV≤△UV_set2. Here, △UV_set1 is the lower limit of the valve side voltage difference, and UV_set2 is the upper limit of the valve side voltage difference.

[0050] According to the example embodiment, the preset range can be △UV < △UV_set1, or the preset range can be △UV > UV_set2.

[0051] For example, in step S130, if the control device determines that the valve-side voltage difference does not meet the preset range, that is, the converter is in normal operation, then the converter continues to remain in reactive power state.

[0052] If the control device determines that the valve-side voltage difference meets the preset range, meaning the converter is not in normal operation, then the converter will activate reactive power regulation. The control device determines the reactive power correction amount based on the valve-side voltage difference.

[0053] According to the example embodiment, the reactive power correction amount can be a reactive power correction value that ensures the valve-side voltage meets the normal operating range.

[0054] Optionally, the correction amount can be proportional to the voltage difference on the valve side.

[0055] For example, the control device can calculate the reactive power correction amount according to the following formula:

[0056] △Q=k×△UV;

[0057] Where △UV is the valve-side voltage difference, △Q is the reactive power correction, and k is the proportional coefficient. k is related to the impedance of the AC line or the leakage reactance of the converter transformer.

[0058] For example, the correction amount and the valve-side voltage difference can also be an integral relationship.

[0059] For example, the correction amount and the valve-side voltage difference can also be a proportional-integral relationship.

[0060] In step S140, a control command is generated based on the correction amount.

[0061] According to an example embodiment, the control command can be instruction information that ensures the valve-side voltage meets the reactive power requirements of the converter under normal operating conditions. The control command may include a target value for the reactive power of the converter.

[0062] For example, in step S140, when the converter is in reactive power control mode, the reactive power of the converter before adjustment is Q_set1. Then, the control device can generate control commands using the following formula:

[0063] Qset_2 = Qset_1 + △Q;

[0064] Where Qset_1 is the reactive power value of the converter before adjustment, Qset_2 is the target value of the reactive power of the converter, and ΔQ is the correction amount of reactive power.

[0065] When the converter is in AC voltage control mode, and the reactive power of the converter before regulation is Q_set3, the control device can determine the control command using the following formula:

[0066] Qset_2 = Qset_3 + △Q;

[0067] Where Qset_3 is the reactive power value of the converter before adjustment, Qset_2 is the target reactive power value of the converter, and ΔQ is the reactive power correction amount.

[0068] For example, when the converter is operating in unipolar mode, the target value for the reactive power of the converter is Qset_2.

[0069] When the converter is operating as a bipolar converter or a multi-converter system with high and low valve groups, the control device can evenly distribute the required reactive power correction to each converter; the control device can also flexibly distribute the reactive power correction according to the power margin of each converter.

[0070] For example, referring to Figure 2, when starting the on-load tap changer regulation control loop of pole 1 converter, the control command for pole 1 converter can be:

[0071] Qset2_1 = Qset1_1 + (△Q) / 2;

[0072] The control commands for the Pole 2 converter can be:

[0073] Qset2_2 = Qset1_2 + (△Q) / 2;

[0074] Where Qset2_1 is the target value of reactive power of pole 1 converter, Qset1_1 is the reactive power value of pole 1 converter before adjustment, Qset2_2 is the target value of reactive power of pole 2 converter, Qset1_2 is the reactive power value of pole 2 converter before adjustment, and ΔQ is the correction amount of reactive power.

[0075] In step S150, reactive power is generated or absorbed according to the control command so that the valve-side voltage meets the target value of the valve-side voltage.

[0076] According to the example embodiment, the target value of the valve-side voltage can be such that the valve-side voltage meets the valve-side voltage value under normal operating conditions of the flexible DC system. The flexible DC converter can be in an unlocked operating state, and can absorb or generate reactive power whether the flexible DC converter is in reactive power control mode or AC voltage control mode.

[0077] For example, in step S150, the control device causes the converter to generate or absorb reactive power according to the generated control command, so that the regulated valve-side voltage can meet the target value of the valve-side voltage.

[0078] When the valve-side voltage difference ΔUV < ΔUV_set1, the control device causes the converter to output reactive power to increase the valve-side voltage of the converter transformer, thereby making the valve-side voltage meet the target value of the valve-side voltage.

[0079] When the valve-side voltage difference ΔUV > UV_set2, the control device causes the converter to absorb reactive power to reduce the valve-side voltage of the converter transformer, thereby ensuring that the valve-side voltage meets the target value.

[0080] Through the above embodiments, this application utilizes the flexible adjustment capability of the converter's reactive power to regulate the valve-side voltage of the converter transformer to meet the target value of the valve-side voltage. Thus, the regulation of the converter replaces the regulation of the on-load tap changer.

[0081] This application can reduce the operational risks of converter transformers by avoiding the mechanical operation of the on-load tap changer when repeated on-load adjustments are required.

[0082] Optionally, referring to Figure 3, step S130 may include step S131 or step S132.

[0083] In step S131, if it is determined that the valve-side voltage difference meets the first preset range, the first correction amount of reactive power is determined based on the valve-side voltage difference.

[0084] According to the example embodiment, the first preset range can be that the valve-side voltage difference is less than a preset range, that is, △UV < △UV_set1.

[0085] For example, in step S131, if the control device determines that the valve-side voltage difference meets the first preset range, i.e., the converter is not in normal operation, then the converter activates the reactive power regulation state. The control device determines the first correction amount of reactive power based on the valve-side voltage difference.

[0086] According to the example embodiment, the first correction amount of reactive power can be a correction value of reactive power that increases the valve-side voltage, thereby satisfying the normal operating range of the valve-side voltage.

[0087] The first correction for reactive power can be proportional to, integrally related to, or proportional-integral related to the voltage difference on the valve side. The formula for calculating the first correction is the same as the formula for calculating the correction mentioned above, and will not be repeated here.

[0088] In step S132, if it is determined that the valve-side voltage difference meets the second preset range, the second correction amount of reactive power is determined based on the valve-side voltage difference.

[0089] According to the example embodiment, the second preset range can be that the valve-side voltage difference is greater than a preset range, that is, △UV>UV_set2.

[0090] For example, in step S132, if the control device determines that the valve-side voltage difference meets the second preset range, i.e., the converter is not in normal operation, then the converter activates the reactive power regulation state. The control device determines a second correction amount for reactive power based on the valve-side voltage difference.

[0091] According to the example embodiment, the second correction amount of reactive power can be a correction value of reactive power that reduces the valve-side voltage, thereby satisfying the normal operating range of the valve-side voltage.

[0092] The second correction for reactive power can be proportional to, integrally related to, or proportional-integral related to the voltage difference on the valve side. The formula for calculating the second correction is the same as the formula for calculating the correction mentioned above, and will not be repeated here.

[0093] Optionally, referring to Figure 4, step S140 may include step S141 or step S142.

[0094] In step S141, a first control command is generated based on the first correction amount.

[0095] According to an example embodiment, the first control command can be instruction information regarding the reactive power of the converter that causes an increase in the valve-side voltage. The first control command may include a target value for the reactive power of the converter.

[0096] For example, in step S141, when the converter is in reactive power control mode, the reactive power of the converter before adjustment is Q_set1. Then, the control device can generate control commands using the following formula:

[0097] Qset_2 = Qset_1 + △Q;

[0098] Where Qset_1 is the reactive power value of the converter before adjustment, Qset_2 is the target reactive power value of the converter, ΔQ is the reactive power correction amount, and Qset_2 is greater than Qset_1.

[0099] When the converter is in AC voltage control mode, and the reactive power of the converter before regulation is Q_set3, the control device can determine the control command using the following formula:

[0100] Qset_2 = Qset_3 + △Q;

[0101] Where Qset_3 is the reactive power value of the converter before adjustment, Qset_2 is the target reactive power value of the converter, ΔQ is the reactive power correction amount, and Qset_2 is greater than Qset_3.

[0102] In step S142, a second control command is generated based on the second correction amount.

[0103] According to an example embodiment, the second control command can be instruction information regarding the reactive power of the converter that causes a reduction in the valve-side voltage. The second control command may include a target value for the reactive power of the converter.

[0104] For example, in step S142, when the converter is in reactive power control mode, the reactive power of the converter before adjustment is Q_set1. Then, the control device can generate control commands using the following formula:

[0105] Qset_2 = Qset_1 + △Q;

[0106] Where Qset_1 is the reactive power value of the converter before adjustment, Qset_2 is the target reactive power value of the converter, ΔQ is the reactive power correction amount, and Qset_2 is less than Qset_1.

[0107] When the converter is in AC voltage control mode, and the reactive power of the converter before regulation is Q_set3, the control device can determine the control command using the following formula:

[0108] Qset_2 = Qset_3 + △Q;

[0109] Where Qset_3 is the reactive power value of the converter before adjustment, Qset_2 is the target reactive power value of the converter, ΔQ is the reactive power correction amount, and Qset_2 is less than Qset_3.

[0110] Optionally, referring to Figure 5, step S150 may include step S151 or step S152.

[0111] In step S151, reactive power is issued according to the first control command so that the valve-side voltage meets the target value of the valve-side voltage.

[0112] For example, in step S151, the control device causes the converter to output reactive power according to the generated first control command, so as to increase the valve-side voltage of the converter transformer, thereby making the valve-side voltage meet the target value of the valve-side voltage.

[0113] In step S152, reactive power is absorbed according to the second control command so that the valve-side voltage meets the target value of the valve-side voltage.

[0114] For example, in step S152, the control device causes the converter to absorb reactive power according to the generated second control command, so as to reduce the valve-side voltage of the converter transformer, thereby making the valve-side voltage meet the target value of the valve-side voltage.

[0115] Optionally, this application also provides a control method 2000 for a flexible DC system. Referring to FIG6, the control method 2000 may include steps S210-S260. Exemplarily, the control method 2000 may be executed by a control device for the flexible DC system.

[0116] Referring to the figure, steps S210-S230 are the same as steps S110-S130 described above, and will not be repeated here.

[0117] In step S240, if it is determined that the correction amount meets the preset correction range, a control command and a third control command are generated based on the correction amount.

[0118] The description of the control commands is the same as that in step S140 above, and will not be repeated here.

[0119] According to the example embodiment, the preset correction range can be defined as the correction amount for the converter's reactive power exceeding the converter's reactive power adjustment range. The converter's reactive power adjustment range is related to the converter's capacity. Therefore, the preset correction range can be defined as the correction amount exceeding the converter's capacity.

[0120] The third control command can be an instruction message that adjusts the on-load tap changer position of the converter transformer.

[0121] For example, in step S240, if the control device determines that the reactive power correction amount meets the preset correction range (i.e., the correction amount exceeds the reactive power adjustment range of the converter), then it generates a control command and a third control command based on the correction amount. If the reactive power capacity of the converter is Q_rl, the reactive power correction amount is ΔQ, and the reactive power before adjustment is Q_set1, then the control device can generate the control command using the following formula:

[0122] Qset_2 = Qset_1 + Q_rl;

[0123] Where Qset_1 is the reactive power value of the converter before adjustment, Qset_2 is the target reactive power value of the converter, and Q_rl is the capacity of the converter.

[0124] The control device can generate the third control command using the following formula:

[0125] Qset_4 = △Q - Qset_2;

[0126] Where △Q is the correction amount for reactive power.

[0127] In step S250, reactive power is generated or absorbed according to the control command.

[0128] For example, in step S250, the control device causes the converter to generate or absorb reactive power according to the generated control command, so as to increase or decrease the voltage value of the valve side voltage.

[0129] When the valve-side voltage difference ΔUV < ΔUV_set1, the control device causes the converter to output reactive power to increase the valve-side voltage of the converter transformer.

[0130] When the valve-side voltage difference ΔUV > UV_set2, the control device causes the converter to absorb reactive power in order to reduce the valve-side voltage of the converter transformer.

[0131] In step S260, a third control command is sent to cause the on-load tap changer to adjust its position so that the valve-side voltage meets the target value of the valve-side voltage.

[0132] For example, in step S260, the control device can send a third control command to the user. The user, in response to the third control command, generates and transmits a user command. The on-load tap changer, in response to the user command, adjusts its position to increase or decrease the valve-side voltage, thereby ensuring that the valve-side voltage meets the target value.

[0133] After adjusting the on-load tap changer, the judgment device can continue to determine whether the valve-side voltage meets the target value. If the valve-side voltage does not meet the target value, after a delay, the on-load tap changer is adjusted again to further increase or decrease the valve-side voltage, thereby ensuring that the valve-side voltage meets the target value.

[0134] Through the above embodiments, this application determines whether the reactive power correction of the converter exceeds the converter's capacity. If the reactive power correction exceeds the converter's capacity, the valve-side voltage is adjusted first using the converter's regulation capability, and then the on-load tap changer's position is adjusted, thereby reducing the on-load tap changer's regulation frequency.

[0135] Optionally, when the converter is operating as a bipolar converter or a multi-converter system with high and low valve groups, converters requiring precise reactive power control only execute power commands. The control device can select a specific converter to activate either reactive power control mode or AC voltage control mode when the valve-side voltage fluctuates. By selecting certain converters for valve-side voltage regulation control based on requirements, a strategy can be implemented that precisely controls the reactive power of the converters while effectively controlling the valve-side voltage of the converter transformers.

[0136] Optionally, when the converter starts in reactive power control mode or AC voltage control mode, hysteresis comparison circuit, delayed start logic, and delayed exit logic can be added according to the requirements of the DC system. This ensures that the reactive power of the converter remains relatively stable even when the valve-side voltage fluctuates frequently at the boundary value of the preset valve-side voltage.

[0137] According to another aspect of this application, a control device 300 for a flexible DC system is provided. Referring to FIG7, the control device 300 includes a converter 301 and a control unit 302.

[0138] According to the example embodiment, the control unit 302 can be located inside the converter 301, or it can be located in the background control system of the flexible DC system.

[0139] The converter 301 monitors the valve-side voltage of the flexible DC system. The control unit 302 determines the valve-side voltage difference based on the valve-side voltage and a preset valve-side voltage value. If the control unit 302 determines that the valve-side voltage difference meets the preset range, it determines a reactive power correction amount based on the valve-side voltage difference. Based on the correction amount, the control unit 302 generates and transmits control commands. The converter 301, according to the control commands, either generates or absorbs reactive power to ensure that the valve-side voltage meets the target value.

[0140] According to the example embodiment, the concepts and calculation process of valve-side voltage, valve-side voltage preset value, valve-side voltage difference, preset range, correction amount, control command, and target value of valve-side voltage are the same as those described in the control method 1000 of the flexible DC system above, and will not be repeated here.

[0141] Through the above embodiments, this application utilizes the flexible adjustment capability of the converter's reactive power to regulate the valve-side voltage of the converter transformer to meet the target value of the valve-side voltage. Thus, the regulation of the converter replaces the regulation of the on-load tap changer.

[0142] This application can reduce the operational risks of converter transformers by avoiding the mechanical operation of the on-load tap changer when repeated on-load adjustments are required.

[0143] Optionally, the control unit 302 further determines a first correction amount for reactive power based on the valve-side voltage difference if the valve-side voltage difference meets a first preset range. Alternatively, the control unit 302 further determines a second correction amount for reactive power based on the valve-side voltage difference if the valve-side voltage difference meets a second preset range.

[0144] The control unit 302 further generates a first control command based on a first correction amount. Alternatively, the control unit 302 further generates a second control command based on a second correction amount. The converter 301 further outputs reactive power according to the first control command to ensure that the valve-side voltage meets the target value of the valve-side voltage. Alternatively, the converter 301 further absorbs reactive power according to the second control command to ensure that the valve-side voltage meets the target value of the valve-side voltage.

[0145] According to the example embodiment, the concepts and calculation processes of the first preset range, the first correction amount, the second preset range, and the second correction amount are the same as those described in the control method 1000 of the flexible DC system above, and will not be repeated here.

[0146] Optionally, the control unit 302 further determines that, if the correction amount meets the preset correction range, it generates a control command and a third control command based on the correction amount. The converter 301 also generates or absorbs reactive power according to the control command. The control unit 302 further sends the third control command to cause the on-load tap changer to adjust its position, thereby ensuring that the valve-side voltage meets the target value of the valve-side voltage.

[0147] According to the example embodiment, the concept and calculation process of the third control command are the same as those described in the above-described control method 2000 for flexible DC systems, and will not be repeated here.

[0148] According to one aspect of this application, this application also provides a non-volatile computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, can implement a control method for a flexible DC system as described above.

[0149] According to one aspect of this application, this application also provides an electronic device, including: one or more processors; and a storage device for storing one or more programs, which, when executed by one or more processors, enable the one or more processors to implement a control method for a flexible DC system as described above.

[0150] According to one aspect of this application, this application also provides a computer program product, comprising: a computer program stored on a computer-readable storage medium; the computer program includes program instructions that, when executed by a computer, cause the computer to perform a control method for a flexible DC system as described above.

[0151] Finally, it should be noted that the above description is merely a preferred embodiment of this application and is not intended to limit this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions of the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A control method for a flexible DC system, characterized in that, The control method includes: monitoring the valve-side voltage of the flexible DC system; determining the valve-side voltage difference based on the valve-side voltage and a preset valve-side voltage value; determining a reactive power correction amount based on the valve-side voltage difference when the valve-side voltage difference meets a preset range; generating a control command based on the correction amount; and issuing or absorbing the reactive power based on the control command so that the valve-side voltage meets the target value of the valve-side voltage.

2. The control method according to claim 1, characterized in that, The correction amount is directly proportional to the voltage difference on the valve side.

3. The control method according to claim 1, characterized in that, The correction amount is integrally related to the voltage difference on the valve side.

4. The control method according to claim 1, characterized in that, The correction amount is proportional to the valve-side voltage difference.

5. The control method according to any one of claims 2-4, characterized in that, When it is determined that the valve-side voltage difference meets a preset range, determining the correction amount of the reactive power based on the valve-side voltage difference includes: when it is determined that the valve-side voltage difference meets a first preset range, determining a first correction amount of the reactive power based on the valve-side voltage difference; or when it is determined that the valve-side voltage difference meets a second preset range, determining a second correction amount of the reactive power based on the valve-side voltage difference; generating a control command based on the correction amount includes: generating a first control command based on the first correction amount; or generating a second control command based on the second correction amount; issuing or absorbing the reactive power based on the control command so that the valve-side voltage meets the target value of the valve-side voltage includes: issuing the reactive power based on the first control command so that the valve-side voltage meets the target value of the valve-side voltage; or absorbing the reactive power based on the second control command so that the valve-side voltage meets the target value of the valve-side voltage.

6. The control method according to claim 1, characterized in that, When it is determined that the valve-side voltage difference meets the preset range, after determining the correction amount of the reactive power based on the valve-side voltage difference, the control method further includes: when it is determined that the correction amount meets the preset correction range, generating the control command and the third control command based on the correction amount; issuing or absorbing reactive power based on the control command; sending the third control command to cause the on-load tap changer to adjust its position, thereby making the valve-side voltage meet the target value of the valve-side voltage.

7. A control device for a flexible DC system, characterized in that, The control device includes: a converter for monitoring the valve-side voltage of the flexible DC system; a control unit for determining the valve-side voltage difference based on the valve-side voltage and a preset valve-side voltage value; the control unit determines a reactive power correction amount based on the valve-side voltage difference when the valve-side voltage difference meets a preset range; the control unit generates and transmits control commands based on the correction amount; and the converter emits or absorbs reactive power according to the control commands to ensure that the valve-side voltage meets the target value of the valve-side voltage.

8. The control device according to claim 7, characterized in that, The control unit further determines that if the correction amount meets the preset correction range, it generates the control command and the third control command based on the correction amount; the converter further issues or absorbs the reactive power according to the control command; the control unit further sends the third control command to cause the on-load tap changer to adjust its position, thereby making the valve-side voltage meet the target value of the valve-side voltage.

9. A non-volatile computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the control method for the flexible DC system as described in any one of claims 1-6.

10. An electronic device, characterized in that, include: One or more processors; Storage device for storing one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement the control method for the flexible DC system as described in any one of claims 1-6.

11. A computer program product, characterized in that, The computer program includes a computer program stored on a computer-readable storage medium, the computer program including program instructions that, when executed by a computer, cause the computer to perform the control method for the flexible DC system as described in any one of claims 1-6.

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