Active power coordination control method and system for multi-terminal flexible DC power transmission system

Abstract

The invention provides an active power coordination control method and system for a multi-terminal flexible DC power transmission system, and relates to the technical field of flexible DC power transmission. The active power coordination control method comprises the following steps: detecting the active power of each current converter in the multi-terminal flexible direct current power transmission system, and calculating the active power lifting amount and the falling amount of each current converter; determining a triggering condition for performing active power coordination control on the multi-terminal flexible direct current power transmission system; according to the triggering condition and the active power lifting quantity and the falling quantity of each converter, the active power variation of the multi-terminal flexible direct-current power transmission system caused by the triggering condition is distributed; and generating and executing an instruction of each converter in the multi-terminal flexible direct current power transmission system according to the active power variation after distribution is completed. According to the method and the system, the real-time active power of a running converter is utilized to realize automatic adjustment of the active power of a plurality of converters when the active power of a power grid changes, and the power balance of the multi-terminal flexible DC converter is kept.

Description

Technical Field

[0001] The present application relates to the technical field of flexible direct current transmission, and in particular to a method and system for coordinated control of active power of a multi-terminal flexible direct current transmission system. Background Art

[0002] Flexible DC transmission has the characteristics of flexible control, rapid dynamic response, low harmonic content, etc. It can quickly and independently adjust active power and reactive power, and has flexible control and coordination capabilities. It is widely regarded as one of the technical means for island power transmission, grid interconnection, reliable access and effective utilization of new energy, and has broad application prospects. Especially in the field of urban grid interconnection, it can realize reliable grid zoning, reduce short-circuit current, and realize rapid active power support in various regions.

[0003] After the urban power grid deploys multi-terminal flexible direct current transmission, the power balance at each end is maintained during steady-state operation. When a converter exits due to a fault or other external factors cause the active power of a converter to change, if no coordinated control is performed and the power is allowed to be distributed automatically, there will be uneven active power distribution and mismatch of system active power, which will lead to overvoltage or undervoltage on the DC side of the system and cause the system to trip and stop operating.

[0004] Therefore, it is necessary to find a coordinated control method for active power of multi-terminal flexible DC transmission, which can coordinate the distribution of active power, avoid active power imbalance, and meet the requirements of stable operation of multi-terminal flexible DC transmission. Summary of the invention

[0005] In order to solve at least one of the above problems, the present application proposes an active power coordinated control method and system for a multi-terminal flexible direct current transmission system.

[0006] According to the first aspect of the present application, at least one embodiment of the present application provides a method for coordinated active power control of a multi-terminal flexible direct current transmission system, including: detecting the active power of each converter in the multi-terminal flexible direct current transmission system, and calculating the amount of active power that can be increased and the amount of active power that can be reduced of each converter; determining the triggering conditions for coordinated active power control of the multi-terminal flexible direct current transmission system; allocating the active power change of the multi-terminal flexible direct current transmission system caused by the triggering conditions according to the triggering conditions and the amount of active power that can be increased and the amount of active power that can be reduced of each converter; and generating and executing instructions for each converter in the multi-terminal flexible direct current transmission system according to the allocated active power change.

[0007] For example, in some embodiments of the present application, the multi-terminal flexible direct current transmission system includes n converters, one converter among the n converters is determined as a DC voltage-controlled operating converter, n-1 converters among the n converters are determined as active power-controlled operating converters, and n is an integer greater than or equal to 3.

[0008] For example, in some embodiments of the present application, detecting the active power of each converter in the multi-terminal flexible direct current power transmission system and calculating the amount of active power that can be increased and the amount of active power that can be reduced of each converter include:

[0009] The increase in active power of each converter is calculated according to the following formula:

[0010]

[0011] The amount of active power that can be reduced for each converter is calculated according to the following formula:

[0012]

[0013] Among them, P j is the active power of each converter, j=1,2,...,n, is the amount of active power increase of each converter, is the rated forward active power of each converter, is the amount of active power that can be reduced for each converter, is the rated negative active power of each converter.

[0014] For example, in some embodiments of the present application, the trigger conditions include: the active power control operation converter exits operation; the DC voltage control operation converter exits operation; an external signal is received to trigger the active power control operation converter to adjust power; and / or an external signal is received to trigger the DC voltage control operation converter to adjust power.

[0015] For example, in some embodiments of the present application, the active power change of the multi-terminal flexible direct current transmission system caused by the trigger condition is distributed according to the trigger condition, the active power increase amount and the active power reduction amount of each converter, including: when the trigger condition is that the active power control operation converter exits operation, determining the active power increase change or active power reduction change of the multi-terminal flexible direct current transmission system caused by the active power control operation converter exiting operation; judging whether the active power increase change or active power reduction change of the multi-terminal flexible direct current transmission system exceeds the active power increase amount or active power reduction amount of the DC voltage control operation converter; when the active power increase change or the active power reduction change does not exceed the DC voltage control operation converter When the active power of the converter can be increased or decreased, the DC voltage controlled converter shall bear the change in active power increase or the change in active power decrease; when the change in active power increase or the change in active power decrease exceeds the active power increase or the active power decrease of the DC voltage controlled converter, the converter shall bear the change in active power increase or the active power decrease according to the proportion of the active power increase or the active power decrease of each of the n-1 converters to the total active power increase or the total active power decrease of the n-1 converters, wherein the n-1 converters are the DC voltage controlled converters and the active power controlled converters except the active power controlled converter that has been shut down.

[0016] For example, in some embodiments of the present application, the active power change of the multi-terminal flexible direct current transmission system caused by the trigger condition is distributed according to the trigger condition, the active power increase amount and the active power reduction amount of each converter, including: when the trigger condition is that the active power control operation converter exits operation, determining the active power increase change or active power reduction change of the multi-terminal flexible direct current transmission system caused by the active power control operation converter exiting operation; judging whether the active power increase change or active power reduction change of the multi-terminal flexible direct current transmission system exceeds the active power increase amount or active power reduction amount of the DC voltage control operation converter; when the active power increase change or the active power reduction change does not exceed the active power increase amount or active power reduction amount of the DC voltage control operation converter, the DC voltage control operation converter shall bear the active power increase change or or the active power reduction change; when the active power increase change or the active power reduction change exceeds the active power increase amount or the active power reduction amount of the DC voltage controlled operation converter, the active power increase change or the active power reduction change is borne according to the active power increase amount or the active power reduction amount of the DC voltage controlled operation converter, and the first active power increase change or the first active power reduction change is obtained; according to the ratio of the active power increase amount or the active power reduction amount of each active power controlled operation converter in the n-2 active power controlled operation converters to the sum of the active power increase amounts or the sum of the active power reduction amounts of the n-2 active power controlled operation converters, the active power increase change or the active power reduction change is borne, wherein the n-2 active power controlled operation converters are active power controlled operation converters except the active power controlled operation converter that has exited operation.

[0017] For example, in some embodiments of the present application, the active power change of the multi-terminal flexible direct current transmission system caused by the trigger condition is distributed according to the trigger condition, the active power increase amount and the active power reduction amount of each converter, including: when the trigger condition is that the DC voltage-controlled operating converter exits operation, determining the active power increase change or the active power reduction change of the multi-terminal flexible direct current transmission system caused by the DC voltage-controlled operating converter exiting operation; assuming the active power increase change or the active power reduction change according to the ratio of the active power increase amount or the active power reduction amount of each active power controlled operating converter among the n-1 active power controlled operating converters to the total active power increase amount or the total active power reduction amount of the n-1 active power controlled operating converters; determining the active power controlled operating converter to which the least active power increase change or active power reduction change is allocated among the n-1 active power controlled operating converters as the updated DC voltage-controlled operating converter.

[0018] For example, in some embodiments of the present application, the active power change of the multi-terminal flexible direct current transmission system caused by the trigger condition is distributed according to the trigger condition, the active power increase amount and the active power reduction amount of each converter, including: when the trigger condition is that an external signal is received to trigger the active power control operation converter to perform power adjustment, determining the active power increase change or active power reduction change of the multi-terminal flexible direct current transmission system caused by the active power control operation converter to perform power adjustment; judging whether the active power increase change or active power reduction change of the multi-terminal flexible direct current transmission system exceeds the active power increase amount or active power reduction amount of the DC voltage control operation converter; when the active power increase change or the active power reduction change does not exceed the DC voltage control operation converter, determining whether the active power increase change or the active power reduction change of the multi-terminal flexible direct current transmission system exceeds the active power increase amount or active power reduction amount of the DC voltage control operation converter; and determining whether the active power increase change or the active power reduction change does not exceed the active power increase amount or the active power reduction change of the DC voltage control operation converter. When the active power increase amount or the active power reduction amount of the DC voltage controlled operation converter exceeds the active power increase amount or the active power reduction amount of the DC voltage controlled operation converter, the active power increase amount or the active power reduction amount shall be borne by the DC voltage controlled operation converter; when the active power increase amount or the active power reduction amount exceeds the active power increase amount or the active power reduction amount of the DC voltage controlled operation converter, the active power increase amount or the active power reduction amount shall be borne according to the proportion of the active power increase amount or the active power reduction amount of each converter in the n-1 converters to the total active power increase amount or the total active power reduction amount of the n-1 converters, wherein the n-1 converters are the DC voltage controlled operation converter and the active power controlled operation converter except the active power controlled operation converter for power adjustment.

[0019] For example, in some embodiments of the present application, the active power change of the multi-terminal flexible direct current transmission system caused by the trigger condition is distributed according to the trigger condition, the active power increase amount and the active power reduction amount of each converter, including: when the trigger condition is that an external signal is received to trigger the active power control operation converter to perform power adjustment, determining the active power increase change or active power reduction change of the multi-terminal flexible direct current transmission system caused by the active power control operation converter performing power adjustment; judging whether the active power increase change or active power reduction change of the multi-terminal flexible direct current transmission system exceeds the active power increase amount or active power reduction amount of the DC voltage control operation converter; when the active power increase change or the active power reduction change does not exceed the active power increase amount or active power reduction amount of the DC voltage control operation converter, the DC voltage control operation converter shall bear the active power increase amount. The active power increase variation or the active power reduction variation is determined by the following steps: when the active power increase variation or the active power reduction variation exceeds the active power increaseable amount or the active power reductionable amount of the DC voltage controlled operation converter, the active power increase variation or the active power reduction variation is borne according to the active power increaseable amount or the active power reductionable amount of the DC voltage controlled operation converter, and a first active power increase variation or a first active power reduction variation is obtained; the active power increase variation or the active power reduction variation is borne according to the ratio of the active power increaseable amount or the active power reductionable amount of each active power controlled operation converter in the n-2 active power controlled operation converters to the total active power increaseable amount or the total active power reductionable amount of the n-2 active power controlled operation converters, wherein the n-2 active power controlled operation converters are active power controlled operation converters other than the active power controlled operation converters that perform power adjustment.

[0020] For example, in some embodiments of the present application, the active power change of the multi-terminal flexible direct current transmission system caused by the trigger condition is allocated according to the trigger condition, the active power increase amount and the active power reduction amount of each converter, including: when the trigger condition is receiving an external signal to trigger the DC voltage control operation converter to perform power adjustment, determining the active power increase change or active power reduction change of the multi-terminal flexible direct current transmission system caused by the DC voltage control operation converter performing power adjustment; assuming the active power increase change or the active power reduction change according to the ratio of the active power increase amount or active power reduction amount of each active power control operation converter among the n-1 active power control operation converters to the sum of the active power increase amounts or the active power reduction amounts of the n-1 active power control operation converters.

[0021] According to the second aspect of the present application, at least one embodiment of the present application provides an active power coordination control system for a multi-terminal flexible direct current transmission system, which is used to execute the active power coordination control method as described in any one of the first aspects, and the active power coordination control system includes: an operation data detection module, which is used to detect the active power of each converter in the multi-terminal flexible direct current transmission system, and calculate the active power increase amount and active power reduction amount of each converter; a trigger condition detection module, which is used to determine the trigger condition for active power coordinated control of the multi-terminal flexible direct current transmission system; a coordination allocation module, which is used to allocate the active power change of the multi-terminal flexible direct current transmission system caused by the trigger condition according to the trigger condition, the active power increase amount and active power reduction amount of each converter; an active power change execution module, which is used to generate and execute instructions for each converter in the multi-terminal flexible direct current transmission system according to the allocated active power change amount.

[0022] Through the above-mentioned example embodiments, the present application provides an active power coordination control method and system for a multi-terminal flexible direct current transmission system. By judging the current amount of active power that can be increased and reduced of each converter, and detecting the triggering conditions that cause active power adjustment, different power coordination allocation methods are performed, different active power instructions are output, and the real-time active power of the running converter is fully utilized. Automatic adjustment of the active power of multiple converters when the active power of the power grid changes is achieved, the power balance of the multi-terminal flexible direct current converters is maintained, and the fluctuation of the direct current voltage is minimized, thereby avoiding direct current overvoltage or undervoltage caused by active power imbalance.

[0023] It should be understood that the foregoing general description and the following detailed description are exemplary only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] By describing in detail exemplary embodiments thereof with reference to the accompanying drawings, the above and other objects, features and advantages of the present application will become more apparent. The accompanying drawings described below are only some embodiments of the present application, and are not intended to limit the present application.

[0025] Figure 1 A schematic diagram of a multi-terminal flexible direct current transmission system of the present application is shown;

[0026] Figure 2 A flow chart showing an active power coordinated control method for a multi-terminal flexible direct current transmission system according to an exemplary embodiment;

[0027] Figure 3 A schematic diagram of an active power coordination control system for a multi-terminal flexible direct current transmission system is shown according to an exemplary embodiment. DETAILED DESCRIPTION

[0028] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this application will be comprehensive and complete and will fully convey the concepts of the example embodiments to those skilled in the art. The same reference numerals in the figures represent the same or similar parts, and thus their repeated description will be omitted.

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

[0030] The flowcharts shown in the accompanying drawings are only exemplary and do not necessarily include all the contents and operations / steps, nor must they be executed in the order described. For example, some operations / steps can be decomposed, and some operations / steps can be combined or partially combined, so the actual execution order may change according to actual conditions.

[0031] The terms "first", "second", etc. in the specification and claims of this application and the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally includes steps or units that are not listed, or optionally includes other steps or units inherent to these processes, methods, products or devices.

[0032] Those skilled in the art will appreciate that the drawings are merely schematic diagrams of example embodiments, and the modules or processes in the drawings are not necessarily necessary for implementing the present application, and therefore cannot be used to limit the scope of protection of the present application.

[0033] Figure 1 A schematic diagram of a multi-terminal flexible direct current transmission system of the present application is shown.

[0034] like Figure 1 As shown, the multi-terminal flexible DC transmission system includes n converters: one converter among the n converters is determined as a DC voltage controlled operating converter, and n-1 converters among the n converters are determined as active power controlled operating converters, where n is an integer greater than or equal to 3. Converter 1 is set as a DC voltage controlled operating converter, and the other converters are active power controlled operating converters. The operating converter refers to a converter that is in an unlocked state and connected on the DC side.

[0035] Figure 2 A flow chart of an active power coordinated control method for a multi-terminal flexible direct current transmission system is shown according to an exemplary embodiment.

[0036] like Figure 2 As shown, the steps of the active power coordinated control method for a multi-terminal flexible direct current transmission system include:

[0037] Step S101, detecting the active power of each converter in the multi-terminal flexible direct current transmission system, and calculating the amount of active power that can be increased and the amount of active power that can be reduced of each converter.

[0038] According to an exemplary embodiment, when the multi-terminal flexible direct current transmission system is running, the active power P of each converter is detected. j , define the direction of active power from negative to positive as the power increase direction, and the direction of active power from positive to negative as the power reduction direction, where j = 1, 2, ..., n.

[0039] The increase in active power of each converter can be calculated according to the following formula:

[0040]

[0041] The amount of active power that can be reduced for each converter is calculated according to the following formula:

[0042]

[0043] in, The amount of active power that can be increased for each converter is: is the rated forward active power of each converter, The amount of active power that can be reduced for each converter is: is the rated negative active power of each converter,

[0044] Step S102: determining a triggering condition for performing coordinated active power control on the multi-terminal HVDC flexible power transmission system.

[0045] According to an example embodiment, the triggering conditions include: the active power control operation converter exits operation, the DC voltage control operation converter exits operation, an external signal is received to trigger the active power control operation converter to perform power adjustment, or an external signal is received to trigger the DC voltage control operation converter to perform power adjustment.

[0046] According to some embodiments, the external signal includes stabilization control, frequency control, etc.

[0047] Step S103, allocating the active power change of the multi-terminal flexible direct current transmission system caused by the triggering condition according to the triggering condition, the amount of active power that can be increased and the amount of active power that can be reduced of each converter.

[0048] According to an example embodiment, when the trigger condition is that the active power control operation converter is deactivated, the active power increase change amount or the active power reduction change amount of the multi-terminal flexible direct current transmission system caused by the active power control operation converter deactivating is determined. It is judged whether the active power increase change amount or the active power reduction change amount of the multi-terminal flexible direct current transmission system exceeds the active power increase amount or the active power reduction amount of the direct current voltage control operation converter:

[0049] When the change in active power increase or active power reduction does not exceed the amount of active power increase or active power reduction that can be achieved by the DC voltage controlled converter, the DC voltage controlled converter shall bear the change in active power increase or active power reduction.

[0050] When the active power increase or decrease change exceeds the active power increase or active power decrease of the DC voltage control converter, two active power coordinated control schemes are included:

[0051] Option 1:

[0052] The change in active power increase or active power reduction is borne according to the ratio of the active power increase or active power reduction of each converter among the n-1 converters to the total active power increase or active power reduction of the n-1 converters, wherein the n-1 converters are DC voltage controlled converters and active power controlled converters except the active power controlled converter that has been shut down.

[0053] For example, when the active power control operation converter x stops running, its active power before the stop is set to P x , if P x ≥0, the total active power increase change of other converters in the multi-terminal flexible DC transmission system is P x When the DC voltage is controlled, the active power of the converter can be increased by The total active power increase change P is borne entirely by the DC voltage control operation converter x If any The current is allocated in proportion to the available capacity of the remaining operating converters. Calculate according to the following formula:

[0054]

[0055] If P x <0, the total active power drop change of other converters in the multi-terminal flexible DC transmission system is |P x |, when the DC voltage controls the active power of the converter, the amount of power that can be reduced The total active power drop change is borne by the DC voltage control converter. x |, if any The amount of power reduction allocated to each converter is Calculate according to the following formula:

[0056]

[0057] Option 2:

[0058] According to the amount of active power that can be increased or the amount of active power that can be reduced of the DC voltage control running converter, the active power increase variation or the active power reduction variation is borne, and the first active power increase variation or the first active power reduction variation is obtained. According to the proportion of the amount of active power that can be increased or the amount of active power that can be reduced of each active power control running converter in the n-2 active power control running converters to the sum of the amount of active power that can be increased or the sum of the amount of active power that can be reduced of the n-2 active power control running converters, the active power increase variation or the active power reduction variation is borne, wherein the n-2 active power control running converters are active power control running converters other than the active power control running converter that has exited operation.

[0059] For example, when the active power control operation converter x stops running, its active power before the stop is set to P x If P x ≥0, the total active power increase change of other converters in the multi-terminal flexible DC transmission system is P x When the DC voltage is controlled, the active power of the converter can be increased by The total active power increase change P is borne entirely by the DC voltage control operation converter x If any The DC voltage is used to control the operation of the converter, and the amount of active power can be increased. Bear, and then increase the active power by the change amount P x Subtract the DC voltage to operate the converter to increase the active power Get the first increase in active power change P x1 , according to the proportion of the available capacity of the remaining operating converters, the available capacity allocated to each converter is Calculate according to the following formula:

[0060]

[0061] If P x <0, the total active power drop change of other converters in the multi-terminal flexible DC transmission system is |P x |. When the DC voltage is controlled, the active power of the converter can be reduced The total active power drop change is borne by the DC voltage control converter. x |; If any The DC voltage is used to control the operation of the converter according to the amount of active power that can be reduced. Bear, and then reduce the active power change |P x |Minus the amount of active power that can be reduced when the DC voltage is running Get the first drop change of active power |Px1 |, according to the proportion of the available reduction of the remaining operating converters, the available reduction amount allocated to each converter is Calculate according to the following formula:

[0062]

[0063] According to an example embodiment, when the trigger condition is that the DC voltage control operation converter exits operation, the active power increase change or active power reduction change of the multi-terminal flexible DC transmission system caused by the DC voltage control operation converter exiting operation is determined. According to the proportion of the active power increase or active power reduction of each active power control operation converter in the n-1 active power control operation converters to the sum of the active power increase or active power reduction of the n-1 active power control operation converters, the active power increase change or active power reduction change is borne. In addition, the active power control operation converter that is allocated the least active power increase change or active power reduction change among the n-1 active power control operation converters is determined as the new DC voltage control operation converter.

[0064] For example, when the DC voltage control running converter 1 is out of operation, its active power before exiting is set to P1. If P1 ≥ 0, the total active power increase change of other converters in the multi-terminal flexible DC transmission system is P1, which is proportionally distributed according to the available increase of the remaining running converters. The available increase allocated to each converter is Calculate according to the following formula:

[0065]

[0066] If P1 < 0, the total active power reduction of other converters in the multi-terminal flexible DC transmission system is |P1|, which is allocated according to the ratio of the available active power reduction of the remaining operating converters. The available active power reduction allocated to each converter is Calculate according to the following formula:

[0067]

[0068] According to an example embodiment, when the trigger condition is that an external signal is received to trigger the active power control operation converter to perform power adjustment, the active power increase change amount or active power reduction change amount of the multi-terminal flexible direct current transmission system caused by the active power control operation converter performing power adjustment is determined. It is determined whether the active power increase change amount or active power reduction change amount of the multi-terminal flexible direct current transmission system exceeds the active power increase amount or active power reduction amount of the direct current voltage control operation converter:

[0069] When the change in active power increase or active power reduction does not exceed the amount of active power increase or active power reduction that can be achieved by the DC voltage controlled converter, the DC voltage controlled converter shall bear the change in active power increase or active power reduction.

[0070] When the active power increase or decrease change exceeds the active power increase or active power decrease of the DC voltage control converter, two active power coordinated control schemes are included:

[0071] Option 1:

[0072] The change in active power increase or active power reduction is borne according to the ratio of the amount of active power increase or active power reduction of each converter among the n-1 converters to the total amount of active power increase or active power reduction of the n-1 converters, wherein the n-1 converters are DC voltage controlled converters and active power controlled converters except the active power controlled converter for power adjustment.

[0073] For example, when an external signal triggers active power control to operate converter x to adjust power, if the adjustment amount ΔP x ≥0, the total active power drop change of other converters in the multi-terminal flexible DC transmission system is ΔP x , when the DC voltage is controlled, the active power of the converter can be reduced The DC voltage controls the operation of the converter to bear all the active power drop changes ΔP x ;like The amount of power reduction allocated to each converter is Calculate according to the following formula:

[0074]

[0075] If ΔP x <0, the total active power increase change of other converters in the multi-terminal flexible DC transmission system is |ΔP x |, when the DC voltage is controlled, the active power of the converter can be increased by The total active power increase change |ΔP is borne entirely by the DC voltage control operating converter x |; If The current is allocated according to the proportion of the available capacity of the remaining operating converters. The available capacity allocated to each converter is Calculate according to the following formula:

[0076]

[0077] Option 2:

[0078] According to the active power increase amount or active power reduction amount of the DC voltage control running converter, the active power increase change amount or active power reduction change amount is assumed, and the first active power increase change amount or the first active power reduction change amount is obtained; according to the proportion of the active power increase amount or active power reduction amount of each active power control running converter in the n-2 active power control running converters to the total active power increase amount or the total active power reduction amount of the n-2 active power control running converters, the active power increase change amount or the active power reduction change amount is assumed. Among them, the n-2 active power control running converters are active power control running converters other than the active power control running converters that perform power adjustment.

[0079] For example, when an external signal triggers active power control to operate converter x to adjust power, if the adjustment amount ΔP x ≥0, the total active power drop change of other converters in the multi-terminal flexible DC transmission system is ΔP x , when the DC voltage is controlled, the active power of the converter can be reduced The DC voltage controls the operation of the converter to bear all the active power drop changes ΔP x ;like The DC voltage is used to control the operation of the converter according to the amount of active power that can be reduced. Bear, and then reduce the active power change ΔP x Subtract the active power reduction amount of the DC voltage operating converter Get the first drop in active power ΔP x1 , according to the proportion of the available reduction of the remaining operating converters, the available reduction amount allocated to each converter is Calculate according to the following formula:

[0080]

[0081] If ΔP x <0, the total active power increase change of other converters in the multi-terminal flexible DC transmission system is |ΔP x |, when the DC voltage is controlled, the active power of the converter can be increased by The total active power increase change |ΔP is borne entirely by the DC voltage control operating converter x |; If The DC voltage is used to control the operation of the converter, and the amount of active power can be increased. Bear, and then increase the active power by the change |ΔP x|Minus the DC voltage to operate the converter's active power can be increased Get the first increase in active power |ΔP x1 |, according to the proportion of the available capacity of the remaining operating converters, the available capacity allocated to each converter is Calculate according to the following formula:

[0082]

[0083] According to an example embodiment, when the trigger condition is that an external signal is received to trigger the DC voltage control operation converter to perform power adjustment, the active power increase change or active power reduction change of the multi-terminal flexible DC transmission system caused by the DC voltage control operation converter performing power adjustment is determined. The active power increase change or active power reduction change is borne according to the ratio of the active power increase amount or active power reduction amount of each active power control operation converter in the n-1 active power control operation converters to the sum of the active power increase amounts or active power reduction amounts of the n-1 active power control operation converters.

[0084] For example, when an external signal triggers the DC voltage control operation converter 1 to adjust the power, if the adjustment amount ΔP1 ≥ 0, the total active power reduction change of other converters in the multi-terminal flexible DC transmission system is ΔP1, which is distributed according to the proportion of the available reduction of the remaining operating converters. The available reduction amount allocated to each converter is Calculate according to the following formula:

[0085]

[0086] If ΔP1≤0, the total active power increase of other converters in the multi-terminal flexible DC transmission system is |ΔP1|, which is allocated according to the proportion of the available active power of the remaining operating converters. The available active power reduction allocated to each converter is Calculate according to the following formula:

[0087]

[0088] Step S104: generating and executing instructions for each converter in the multi-terminal flexible direct current transmission system according to the distributed active power variation.

[0089] According to an exemplary embodiment, the allocated active power variation is added to the active power of the corresponding operating control converter to form a new active power control instruction and execute it.

[0090] The present application also provides an active power coordination control system for a multi-terminal flexible DC power transmission system, which is used to execute the active power coordination control method for a multi-terminal flexible DC power transmission system as described above. Figure 3 As shown, the active power coordinated control system includes: an operation data detection module, a trigger condition detection module, a coordinated allocation module and an active power change execution module.

[0091] Among them, the operation data detection module is used to detect the active power of each converter in the multi-terminal flexible DC transmission system, and calculate the amount of active power that can be increased and the amount of active power that can be reduced of each converter.

[0092] The trigger condition detection module is used to determine the trigger condition for active power coordinated control of the multi-terminal flexible direct current transmission system.

[0093] The coordinated allocation module is used to allocate the active power change of the multi-terminal flexible direct current transmission system caused by the triggering conditions according to the triggering conditions, the active power increase amount and the active power reduction amount of each converter.

[0094] The active power variation execution module is used to generate and execute instructions for each converter in the multi-terminal flexible direct current transmission system according to the allocated active power variation.

[0095] The active power coordinated control system is used to execute the active power coordinated control method as described above, so it will not be described in detail here.

[0096] The present application provides an active power coordination control method and system for a multi-terminal flexible direct current transmission system. By judging the current amount of active power that can be increased and reduced by each converter and detecting the triggering conditions that cause active power adjustment, different power coordination allocation methods are performed, different active power instructions are output, and the real-time active power of the running converter is fully utilized to achieve automatic adjustment of the active power of multiple converters when the active power of the power grid changes, so as to maintain the power balance of the multi-terminal flexible direct current converters and minimize the fluctuation of the direct current voltage, thereby avoiding direct current overvoltage or undervoltage caused by active power imbalance.

[0097] It should be clearly understood that the present application describes how to form and use specific examples, but the present application is not limited to any details of these examples. On the contrary, based on the teaching of the content disclosed in the present application, these principles can be applied to many other embodiments.

[0098] In addition, it should be noted that the above figures are only schematic illustrations of the processes included in the method according to the exemplary embodiments of the present application, and are not intended to be limiting. It is easy to understand that the processes shown in the above figures do not indicate or limit the time sequence of these processes. In addition, it is also easy to understand that these processes can be performed synchronously or asynchronously, for example, in multiple modules.

[0099] The exemplary embodiments of the present application are specifically shown and described above. It should be understood that the present application is not limited to the detailed structures, configurations or implementations described herein; on the contrary, the present application is intended to cover various modifications and equivalent configurations included within the objectives and scope of the appended claims.

Claims

1. A method for coordinated control of active power in a multi-terminal flexible direct current transmission system, characterized in that: include: Detecting the active power of each converter in the multi-terminal flexible direct current power transmission system, and calculating the amount of active power that can be increased and the amount of active power that can be reduced of each converter; Determining a trigger condition for performing active power coordinated control on the multi-terminal flexible direct current transmission system; Allocating the active power change of the multi-terminal flexible direct current transmission system caused by the triggering condition according to the triggering condition, the amount of active power that can be increased and the amount of active power that can be reduced of each converter; According to the distributed active power variation, an instruction of each converter in the multi-terminal flexible direct current transmission system is generated and executed.

2. The active power coordinated control method according to claim 1, characterized in that: The multi-terminal flexible direct current transmission system includes n converters, one converter among the n converters is determined as a direct current voltage controlled operating converter, n-1 converters among the n converters are determined as active power controlled operating converters, and n is an integer greater than or equal to 3.

3. The active power coordinated control method according to claim 2, characterized in that: The detecting the active power of each converter in the multi-terminal flexible direct current power transmission system and calculating the amount of active power that can be increased and the amount of active power that can be reduced of each converter includes: The increase in active power of each converter is calculated according to the following formula: The amount of active power that can be reduced for each converter is calculated according to the following formula: Among them, P j is the active power of each converter, j=1,2,...,n, is the amount of active power increase of each converter, is the rated forward active power of each converter, is the amount of active power that can be reduced for each converter, is the rated negative active power of each converter.

4. The active power coordinated control method according to claim 2, characterized in that: The trigger conditions include: Active power control operation converter is out of operation; The DC voltage controls the running converter to exit operation; Receiving an external signal to trigger active power control to operate the converter to adjust power; and / or Receiving an external signal triggers the DC voltage control to operate the converter for power adjustment.

5. The active power coordinated control method according to claim 4, characterized in that: The method of allocating the active power change of the multi-terminal flexible direct current power transmission system caused by the triggering condition according to the triggering condition, the active power increase amount and the active power reduction amount of each converter, comprises: When the trigger condition is that the active power control operation converter is deactivated, determining the active power increase change or active power reduction change of the multi-terminal flexible direct current transmission system caused by the active power control operation converter being deactivated; Determine whether the active power increase or active power reduction change of the multi-terminal flexible direct current power transmission system exceeds the active power increase or active power reduction of the direct current voltage controlled converter; In the case where the active power increase variation or the active power reduction variation does not exceed the active power increase amount or the active power reduction amount of the DC voltage controlled operation converter, the DC voltage controlled operation converter shall bear the active power increase variation or the active power reduction variation; In the case where the active power increase change or the active power reduction change exceeds the active power increase amount or active power reduction amount of the DC voltage-controlled operating converter, the active power increase change or the active power reduction change is borne according to the ratio of the active power increase amount or active power reduction amount of each of the n-1 converters to the total active power increase amounts or the total active power reduction amounts of the n-1 converters, wherein the n-1 converters are the DC voltage-controlled operating converters and the active power controlled operating converters except the active power controlled operating converter that has been shut down.

6. The active power coordinated control method according to claim 4, characterized in that: The method of allocating the active power change of the multi-terminal flexible direct current power transmission system caused by the triggering condition according to the triggering condition, the active power increase amount and the active power reduction amount of each converter, comprises: When the trigger condition is that the active power control operation converter is deactivated, determining the active power increase change or active power reduction change of the multi-terminal flexible direct current transmission system caused by the active power control operation converter being deactivated; Determine whether the active power increase or active power reduction change of the multi-terminal flexible direct current power transmission system exceeds the active power increase or active power reduction of the direct current voltage controlled converter; In the case where the active power increase variation or the active power reduction variation does not exceed the active power increase amount or the active power reduction amount of the DC voltage controlled operation converter, the DC voltage controlled operation converter shall bear the active power increase variation or the active power reduction variation; In the case where the active power increase variation or the active power reduction variation exceeds the active power increaseable amount or the active power reductionable amount of the DC voltage controlled converter, the active power increase variation or the active power reductionable amount is borne according to the active power increaseable amount or the active power reductionable amount of the DC voltage controlled converter, and a first active power increase variation or a first active power reduction variation is obtained; According to the ratio of the amount of active power that can be increased or the amount of active power that can be reduced of each active power controlled operation converter among the n-2 active power controlled operation converters to the total amount of active power that can be increased or the total amount of active power that can be reduced of the n-2 active power controlled operation converters, the active power increase change or the active power reduction change is borne, wherein the n-2 active power controlled operation converters are the active power controlled operation converters except the active power controlled operation converter that has been exited from operation.

7. The active power coordinated control method according to claim 4, characterized in that: The method of allocating the active power change of the multi-terminal flexible direct current power transmission system caused by the triggering condition according to the triggering condition, the active power increase amount and the active power reduction amount of each converter, comprises: When the trigger condition is that the DC voltage-controlled converter is out of operation, determining the active power increase change or active power reduction change of the multi-terminal flexible DC power transmission system caused by the DC voltage-controlled converter being out of operation; According to the ratio of the amount of active power that can be increased or the amount of active power that can be reduced of each active power control operation converter in the n-1 active power control operation converters to the sum of the amounts of active power that can be increased or the sum of the amounts of active power that can be reduced of the n-1 active power control operation converters, the active power increase change or the active power reduction change is assumed; The active power control operation converter to which the least active power increase variation or active power decrease variation is allocated among the n-1 active power control operation converters is determined as the updated DC voltage control operation converter.

8. The active power coordinated control method according to claim 4, characterized in that: The method of allocating the active power change of the multi-terminal flexible direct current power transmission system caused by the triggering condition according to the triggering condition, the active power increase amount and the active power reduction amount of each converter, comprises: When the trigger condition is receiving an external signal to trigger the active power control operation converter to perform power adjustment, determining the active power increase change or active power reduction change of the multi-terminal flexible direct current transmission system caused by the active power control operation converter performing power adjustment; Determine whether the active power increase or active power reduction change of the multi-terminal flexible direct current power transmission system exceeds the active power increase or active power reduction of the direct current voltage controlled converter; In the case where the active power increase variation or the active power reduction variation does not exceed the active power increase amount or the active power reduction amount of the DC voltage controlled operation converter, the DC voltage controlled operation converter shall bear the active power increase variation or the active power reduction variation; In the case where the active power increase change or the active power reduction change exceeds the active power increase amount or active power reduction amount of the DC voltage controlled operation converter, the active power increase change or the active power reduction change is borne according to the ratio of the active power increase amount or active power reduction amount of each converter in the n-1 converters to the total active power increase amount or the total active power reduction amount of the n-1 converters, wherein the n-1 converters are DC voltage controlled operation converters and active power controlled operation converters except the active power controlled operation converter for power adjustment.

9. The active power coordinated control method according to claim 4, characterized in that: The method of allocating the active power change of the multi-terminal flexible direct current power transmission system caused by the triggering condition according to the triggering condition, the active power increase amount and the active power reduction amount of each converter, comprises: When the trigger condition is receiving an external signal to trigger the active power control operation converter to perform power adjustment, determining the active power increase change or active power reduction change of the multi-terminal flexible direct current transmission system caused by the active power control operation converter performing power adjustment; Determine whether the active power increase or active power reduction change of the multi-terminal flexible direct current power transmission system exceeds the active power increase or active power reduction of the direct current voltage controlled converter; In the case where the active power increase variation or the active power reduction variation does not exceed the active power increase amount or the active power reduction amount of the DC voltage controlled operation converter, the DC voltage controlled operation converter shall bear the active power increase variation or the active power reduction variation; In the case where the active power increase variation or the active power reduction variation exceeds the active power increaseable amount or the active power reductionable amount of the DC voltage controlled converter, the active power increase variation or the active power reductionable amount is borne according to the active power increaseable amount or the active power reductionable amount of the DC voltage controlled converter, and a first active power increase variation or a first active power reduction variation is obtained; According to the ratio of the amount of active power that can be increased or the amount of active power that can be reduced of each active power controlled and operated converter among the n-2 active power controlled and operated converters to the total amount of active power that can be increased or the total amount of active power that can be reduced of the n-2 active power controlled and operated converters, the active power increase change or the active power reduction change is borne, wherein the n-2 active power controlled and operated converters are active power controlled and operated converters other than the active power controlled and operated converter for power adjustment.

10. The active power coordinated control method according to claim 4, characterized in that: The method of allocating the active power change of the multi-terminal flexible direct current power transmission system caused by the triggering condition according to the triggering condition, the active power increase amount and the active power reduction amount of each converter, comprises: When the trigger condition is receiving an external signal to trigger the DC voltage control operation converter to perform power adjustment, determining the active power increase change or active power reduction change of the multi-terminal flexible DC power transmission system caused by the DC voltage control operation converter performing power adjustment; The active power increase change or the active power reduction change is borne according to the ratio of the active power increase amount or the active power reduction amount of each active power control running converter in the n-1 active power control running converters to the total active power increase amount or the total active power reduction amount of the n-1 active power control running converters.

11. An active power coordination control system for a multi-terminal flexible direct current transmission system, characterized in that: Used to execute the active power coordinated control method according to any one of claims 1 to 10, the active power coordinated control system comprising: An operation data detection module is used to detect the active power of each converter in the multi-terminal flexible direct current power transmission system, and calculate the amount of active power that can be increased and the amount of active power that can be reduced of each converter; A trigger condition detection module, used to determine the trigger condition for performing active power coordinated control on the multi-terminal flexible direct current transmission system; A coordination allocation module, configured to allocate the active power change of the multi-terminal flexible direct current transmission system caused by the trigger condition according to the trigger condition, the amount of active power that can be increased and the amount of active power that can be reduced of each converter; The active power variation execution module is used to generate and execute instructions for each converter in the multi-terminal flexible direct current transmission system according to the allocated active power variation.

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