Active power coordinated control method and system for multi-terminal flexible direct current transmission system

Abstract

The application 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 converter in the multi-terminal flexible DC power transmission system, calculating the active power increase and decrease of each converter; determining a trigger condition for the active power coordination control of the multi-terminal flexible DC power transmission system; distributing the active power change amount of the multi-terminal flexible DC power transmission system caused by the trigger condition according to the trigger condition, the active power increase and decrease of each converter; and generating and executing the instructions of each converter in the multi-terminal flexible DC power transmission system according to the distributed active power change amount. The method and system utilize the real-time active power of the running converter, realize the automatic adjustment of the active power of multiple converters when the power grid active power changes, and maintain the power balance of the multi-terminal flexible DC converter.

Description

TECHNICAL FIELD

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

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

[0003] After deploying multi-terminal flexible direct current power transmission in urban power grid, in steady state operation, the power balance of each terminal is maintained, when a converter is out of service due to failure or other external factors cause the active power of a converter to change, if no coordination control is performed and the power is distributed by itself, there will be uneven distribution of active power and mismatch of system active power, which will lead to overvoltage or undervoltage on the DC side of the system, causing system trip and shutdown.

[0004] Therefore, it is necessary to find a coordination control method for active power of multi-terminal flexible direct current power transmission, which can coordinate the distribution of active power and avoid uneven distribution of active power, to meet the demand for stable operation of multi-terminal flexible direct current power transmission. SUMMARY

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

[0006] According to a first aspect of the present application, at least one embodiment of the present application provides an active power coordination control method for a multi-terminal flexible direct current power transmission system, comprising: detecting the active power of each converter in the multi-terminal flexible direct current power transmission system, calculating the active power that can be increased and the active power that can be decreased of each converter; determining a trigger condition for active power coordination control of the multi-terminal flexible direct current power transmission system; according to the trigger condition, the active power that can be increased and the active power that can be decreased of each converter, distributing the active power change amount of the multi-terminal flexible direct current power transmission system caused by the trigger condition; according to the distributed active power change amount, generating and executing the instructions of each converter in the multi-terminal flexible direct current power transmission system.

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

[0008] For example, in some embodiments of the present application, the detecting the active power of each converter in the multi-terminal flexible HVDC power transmission system and calculating the active power up-amount and the active power down-amount of each converter includes:

[0009] The active power up-amount of each converter is calculated according to the following formula:

[0010]

[0011] The active power down-amount of each converter is calculated according to the following formula:

[0012]

[0013] wherein, P j is the active power of each converter, j = 1, 2, …, n, is the active power up-amount of each converter, is the rated positive active power of each converter, is the active power down-amount of each converter, is the rated negative active power of each converter.

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

[0015] For example, in some embodiments of the present application, the method for distributing the active power variation of the multi-terminal flexible HVDC power transmission system caused by the trigger condition according to the trigger condition, the active power up-amount and the active power down-amount of each converter comprises: in the case that the trigger condition is that the active power control operating converter exits operation, determining the active power up-variation or the active power down-variation of the multi-terminal flexible HVDC power transmission system caused by the active power control operating converter exiting operation; judging whether the active power up-variation or the active power down-variation of the multi-terminal flexible HVDC power transmission system exceeds the active power up-amount or the active power down-amount of the DC voltage control operating converter; in the case that the active power up-variation or the active power down-variation does not exceed the active power up-amount or the active power down-amount of the DC voltage control operating converter, the DC voltage control operating converter undertakes the active power up-variation or the active power down-variation; in the case that the active power up-variation or the active power down-variation exceeds the active power up-amount or the active power down-amount of the DC voltage control operating converter, according to the proportion of the active power up-amount or the active power down-amount of each converter in the n-1 converters to the total of the active power up-amount or the active power down-amount of the n-1 converters, the active power up-variation or the active power down-variation is undertaken, wherein the n-1 converters are the DC voltage control operating converters and the active power control operating converters except the active power control operating converter exiting operation.

[0016] For example, in some embodiments of the present application, the method of distributing the active power change amount of the multi-terminal flexible HVDC power transmission system caused by the trigger condition according to the trigger condition, the active power up-amount and the active power down-amount of each converter comprises: in the case that the trigger condition is that an active power control operating converter exits operation, determining the active power up-amount or the active power down-amount of the multi-terminal flexible HVDC power transmission system caused by the active power control operating converter exiting operation; judging whether the active power up-amount or the active power down-amount of the multi-terminal flexible HVDC power transmission system exceeds the active power up-amount or the active power down-amount of the DC voltage control operating converter; in the case that the active power up-amount or the active power down-amount does not exceed the active power up-amount or the active power down-amount of the DC voltage control operating converter, the DC voltage control operating converter undertakes the active power up-amount or the active power down-amount; in the case that the active power up-amount or the active power down-amount exceeds the active power up-amount or the active power down-amount of the DC voltage control operating converter, the DC voltage control operating converter undertakes the active power up-amount or the active power down-amount according to the active power up-amount or the active power down-amount of the DC voltage control operating converter, and obtains an active power first up-amount or an active power first down-amount; and the active power up-amount or the active power down-amount is undertaken according to the proportion of the active power up-amount or the active power down-amount of each active power control operating converter in the sum of the active power up-amount or the sum of the active power down-amount of n-2 active power control operating converters, wherein the n-2 active power control operating converters are active power control operating converters other than the active power control operating converter exiting operation.

[0017] For example, in some embodiments of the present application, the step of allocating the active power change amount of the multi-terminal flexible HVDC power transmission system caused by the trigger condition according to the trigger condition, the active power up-amount and the active power down-amount of each converter includes: in the case that the trigger condition is that the DC voltage control operating converter exits operation, determining the active power up-change amount or the active power down-change amount of the multi-terminal flexible HVDC power transmission system caused by the DC voltage control operating converter exiting operation; and according to the proportion of the active power up-amount or the active power down-amount of each of the n-1 active power control operating converters in the sum of the active power up-amount or the sum of the active power down-amount of the n-1 active power control operating converters, the n-1 active power control operating converters bear the active power up-change amount or the active power down-change amount; and determining that the active power control operating converter which is allocated the least active power up-change amount or the active power down-change amount among the n-1 active power control operating converters is the updated DC voltage control operating converter.

[0018] For example, in some embodiments of the present application, the step of allocating the active power change amount of the multi-terminal flexible HVDC power transmission system caused by the trigger condition according to the trigger condition, the active power up-amount and the active power down-amount of each converter includes: in the case that the trigger condition is that the DC voltage control operating converter exits operation, determining the active power up-change amount or the active power down-change amount of the multi-terminal flexible HVDC power transmission system caused by the DC voltage control operating converter exiting operation; and according to the proportion of the active power up-amount or the active power down-amount of each of the n-1 active power control operating converters in the sum of the active power up-amount or the sum of the active power down-amount of the n-1 active power control operating converters, the n-1 active power control operating converters bear the active power up-change amount or the active power down-change amount; and determining that the active power control operating converter which is allocated the least active power up-change amount or the active power down-change amount among the n-1 active power control operating converters is the updated DC voltage control operating converter.

[0019] For example, in some embodiments of the present application, the method of distributing the active power change amount of the multi-terminal flexible HVDC power transmission system caused by the trigger condition according to the trigger condition, the active power increase amount and the active power decrease amount of each converter includes: in the case that the trigger condition is receiving an external signal to trigger the active power control operating converter to adjust power, determining the active power increase change amount or the active power decrease change amount of the multi-terminal flexible HVDC power transmission system caused by the active power control operating converter adjusting power; determining whether the active power increase change amount or the active power decrease change amount of the multi-terminal flexible HVDC power transmission system exceeds the active power increase amount or the active power decrease amount of the DC voltage control operating converter; in the case that the active power increase change amount or the active power decrease change amount does not exceed the active power increase amount or the active power decrease amount of the DC voltage control operating converter, the DC voltage control operating converter undertakes the active power increase change amount or the active power decrease change amount; in the case that the active power increase change amount or the active power decrease change amount exceeds the active power increase amount or the active power decrease amount of the DC voltage control operating converter, the DC voltage control operating converter undertakes the active power increase change amount or the active power decrease change amount according to the active power increase amount or the active power decrease amount of the DC voltage control operating converter, and obtains an active power first increase change amount or an active power first decrease change amount; and the active power increase change amount or the active power decrease change amount is undertaken according to the proportion of the active power increase amount or the active power decrease amount of each of the n-2 active power control operating converters in the total of the active power increase amount or the total of the active power decrease amount of the n-2 active power control operating converters, wherein the n-2 active power control operating converters are the active power control operating converters other than the active power control operating converter adjusting power.

[0020] For example, in some embodiments of the present application, the step of allocating the active power change amount of the multi-terminal flexible HVDC power transmission system caused by the trigger condition according to the trigger condition, the active power increase amount and the active power decrease amount of each converter includes: in the case that the trigger condition is receiving an external signal to trigger the DC voltage control operation converter to adjust power, determining the active power increase change amount or the active power decrease change amount of the multi-terminal flexible HVDC power transmission system caused by the power adjustment of the DC voltage control operation converter; and according to the proportion of the active power increase amount or the active power decrease amount of each of the n-1 active power control operation converters in the total of the active power increase amount or the total of the active power decrease amount of the n-1 active power control operation converters, the n-1 active power control operation converters bear the active power increase change amount or the active power decrease change amount.

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

[0022] Through the above example embodiments, the present application provides an active power coordinated control method and system for a multi-terminal flexible HVDC power transmission system. By judging the current active power increase amount and the active power decrease amount of each converter, and detecting the trigger condition causing the active power adjustment, different power coordination allocation methods are performed, and different active instructions are output. The real-time active power of the operation converter is fully utilized, the automatic adjustment of the active power of the multiple converters when the grid active power changes is realized, the power balance of the multi-terminal flexible HVDC converter is maintained, the fluctuation of the DC voltage is minimized, and the DC overvoltage or under-voltage caused by the active power imbalance is avoided.

[0023] It should be understood that the above general description and the following detailed description are only exemplary and cannot limit the present application. BRIEF DESCRIPTION OF DRAWINGS

[0024] The above and other objects, features and advantages of the present application will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which like reference characters refer to like elements throughout the figures, and in which:

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

[0026] Figure 2 A flow chart of an active power coordinated control method for a multi-terminal flexible HVDC power transmission system of an example embodiment is shown;

[0027] Figure 3 A schematic diagram of an active power coordinated control system for a multi-terminal flexible HVDC power transmission system of an example embodiment is shown. DETAILED DESCRIPTION

[0028] Example embodiments now will be described more fully hereinafter with reference to the accompanying drawings. Example embodiments, however, can be implemented in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of example embodiments to those skilled in the art. Like reference numerals refer to like elements throughout the figures and the specification.

[0029] The described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of embodiments of the disclosure. One skilled in the relevant art will recognize, however, that the techniques described can be practiced without one or more of the specific details, or with other methods, components, materials, and so forth. In some instances, well-known structures, methods, devices, implementations, materials, and operations are not shown or described in detail.

[0030] The flow charts shown in the figures are only exemplary and do not necessarily have to include all of the content and operations / steps, nor do they have to be executed in the order described. For example, some operations / steps can be further broken down, while some operations / steps can be combined or partially combined, so the actual execution order can be changed according to actual conditions.

[0031] The terms "first", "second", and the like in the description and in the claims of the present application and above drawings are used for distinguishing between similar objects and not necessarily for describing a specific sequential or chronological order. The terms "comprises", "comprising", "includes", "including" and the like are to be construed open- ended, meaning that they are used to describe various embodiments and exclude neither sequence nor composition of elements. For example, a process, method, article, or apparatus that comprises a list of steps or elements is not necessarily limited to the listed steps or elements, but can include further or other steps or elements neither expressly listed nor essential to the process, method, article, or apparatus.

[0032] Those skilled in the art can understand that the modules or flows in the drawings are not necessarily essential for implementing the present application, and therefore cannot be used to limit the protection scope of the present application.

[0033] Figure 1 A schematic diagram of a multi-terminal flexible HVDC power transmission system is shown.

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

[0035] Figure 2 A flowchart of an active power coordination control method for a multi-terminal flexible HVDC power transmission system according to an example embodiment is shown.

[0036] As shown in Figure 2 , the steps of the active power coordination control method for a multi-terminal flexible HVDC power transmission system include:

[0037] Step S101, detecting the active power of each converter in the multi-terminal flexible HVDC power transmission system, and calculating the active power that can be raised and the active power that can be lowered for each converter.

[0038] According to an example embodiment, when the multi-terminal flexible HVDC power transmission system is running, the active power P j of each converter is detected, and the active power is defined as the power raising direction from negative to positive, and the power lowering direction from positive to negative, where j = 1, 2,..., n.

[0039] The active power that can be raised for each converter is calculated according to the following formula:

[0040]

[0041] The active power reducible amount of each converter is calculated according to the following formula:

[0042]

[0043] wherein, is the active power reducible amount of each converter, is the rated positive active power of each converter, is the active power reducible amount of each converter, is the rated negative active power of each converter,

[0044] Step S102, determining a triggering condition for active power coordinated control of the multi-terminal flexible DC power transmission system.

[0045] According to an example embodiment, the triggering condition includes that the active power control operating converter exits operation, the DC voltage control operating converter exits operation, an external signal triggering the active power control operating converter to adjust power is received, or an external signal triggering the DC voltage control operating converter to adjust power is received.

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

[0047] Step S103, according to the triggering condition, the active power reducible amount and the active power reducible amount of each converter, distributing the active power change amount of the multi-terminal flexible DC power transmission system caused by the triggering condition.

[0048] According to an example embodiment, in the case that the triggering condition is that the active power control operating converter exits operation, the active power increase change amount or the active power reduction change amount of the multi-terminal flexible DC power transmission system caused by the active power control operating converter exiting operation is determined. It is judged whether the active power increase change amount or the active power reduction change amount of the multi-terminal flexible DC power transmission system exceeds the active power reducible amount or the active power reducible amount of the DC voltage control operating converter:

[0049] In the case that the active power increase change amount or the active power reduction change amount does not exceed the active power reducible amount or the active power reducible amount of the DC voltage control operating converter, the active power increase change amount or the active power reduction change amount is borne by the DC voltage control operating converter.

[0050] In the case that the active power increase change amount or the active power reduction change amount exceeds the active power reducible amount or the active power reducible amount of the DC voltage control operating converter, two active power coordinated control schemes are included:

[0051] Scheme one:

[0052] Based on the proportion of the active power increase or decrease that each of the n-1 converters can achieve to the sum of the active power increase or decrease of the total active power of the n-1 converters, the converters are responsible for the change in active power increase or decrease. The n-1 converters are DC voltage control converters and active power control converters, excluding active power control converters that have been taken out of operation.

[0053] For example, when the active power control converter x is taken out of operation, its active power before taking out of operation is set to P. x If P x If ≥0, then the resulting change in the total active power of other converters in the multi-terminal flexible DC transmission system is P. x When the DC voltage controls the operation of the converter, the active power can be increased. The DC voltage-controlled converter then bears the entire responsibility for the total active power increase P. x If there is The remaining operational converters will be allocated proportionally based on their upgrade potential, with each converter receiving an allocated upgrade potential. Calculate according to the following formula:

[0054]

[0055] If P x If <0, then the resulting change in the total active power reduction of other converters in the multi-terminal flexible DC transmission system is |P x | When the DC voltage controls the operation of the converter, the active power can be reduced. The DC voltage-controlled converter then bears the entire impact of the total active power reduction change |P x |, if The reduction amount is allocated according to the proportion of the remaining operating converters, with each converter allocated a reduction amount. Calculate according to the following formula:

[0056]

[0057] Option 2:

[0058] According to the active power boostable amount or the active power reducible amount of the DC voltage control operating converter, the active power boost change or the active power reduction change is borne, and an active power first boost change or an active power first reduction change is obtained. According to the proportion of the active power boostable amount or the active power reducible amount of each of the n-2 active power control operating converters in the sum of the active power boostable amount or the sum of the active power reducible amount of the n-2 active power control operating converters, the active power boost change or the active power reduction change is borne, wherein the n-2 active power control operating converters are the active power control operating converters other than the active power control operating converter that exits operation.

[0059] For example, when the active power control operating converter x exits operation, the active power before it exits is set as P x . If P x ≥ 0, the total active power boost change of the other converters of the multi-terminal flexible DC power transmission system caused is P x . When the active power boostable amount of the DC voltage control operating converter is P , the total active power boost change P x is borne by the DC voltage control operating converter. If the active power boostable amount of the DC voltage control operating converter is P , first, the DC voltage control operating converter bears according to the active power boostable amount P , then the active power boost change P x is reduced by the active power boostable amount P of the DC voltage operating converter to obtain the active power first boost change P x1 , and the boostable amount of each of the remaining operating converters is distributed in proportion, and the boostable amount of each converter is calculated according to the following formula:

[0060]

[0061] If P x < 0, the total active power reduction change of the other converters of the multi-terminal flexible DC power transmission system caused is |P x |. When the active power reducible amount of the DC voltage control operating converter is P , the total active power reduction change |P x | is borne by the DC voltage control operating converter. If the active power reducible amount of the DC voltage control operating converter is P , first, the DC voltage control operating converter bears according to the active power reducible amount P , then the active power reduction change |P x | is reduced by the active power reducible amount P of the DC voltage operating converter to obtain the active power first reduction change |P x1 |, and the reducible amount of each of the remaining operating converters is distributed in proportion, and the reducible amount of each converter is calculated according to the following formula:x1 |P1|, and the available amount of power reduction of each of the remaining operating converters is allocated in proportion to the available amount of power reduction of the remaining operating converters The following formula is used for calculation:

[0062]

[0063] According to the example embodiment, in the case that the triggering condition is that the DC voltage control operating converter exits operation, the active power increase variation or the active power reduction variation of the multi-terminal VSC-MTDC system caused by the DC voltage control operating converter exiting operation is determined. The active power increase variation or the active power reduction variation is borne by each of the n-1 active power control operating converters in proportion to the total of the active power increase amount or the active power reduction amount of the n-1 active power control operating converters. Furthermore, the active power control operating converter to which the least active power increase variation or the least active power reduction variation is allocated among the n-1 active power control operating converters is determined as the new DC voltage control operating converter.

[0064] For example, when the DC voltage control operating converter 1 exits operation, the active power of the DC voltage control operating converter 1 before exiting operation is set as P1. If P1≥0, the total active power increase variation of the other converters of the multi-terminal VSC-MTDC system caused by the DC voltage control operating converter 1 exiting operation is P1, and the available amount of power increase of each of the remaining operating converters is allocated in proportion to the available amount of power increase of the remaining operating converters The following formula is used for calculation:

[0065]

[0066] If P1<0, the total active power reduction variation of the other converters of the multi-terminal VSC-MTDC system caused by the DC voltage control operating converter 1 exiting operation is |P1|, and the available amount of power reduction of each of the remaining operating converters is allocated in proportion to the available amount of power reduction of the remaining operating converters The following formula is used for calculation:

[0067]

[0068] According to the example embodiment, in the case that the triggering condition is that an external signal is received to trigger the active power control operating converter to perform power adjustment, the active power increase variation or the active power reduction variation of the multi-terminal VSC-MTDC system caused by the active power control operating converter performing power adjustment is determined. It is determined whether the active power increase variation or the active power reduction variation of the multi-terminal VSC-MTDC system exceeds the active power increase amount or the active power reduction amount of the DC voltage control operating converter:

[0069] In the case that the active power increase variation or the active power decrease variation does not exceed the active power increase amount or the active power decrease amount of the DC voltage control operating converter, the active power increase variation or the active power decrease variation is borne by the DC voltage control operating converter.

[0070] In the case that the active power increase variation or the active power decrease variation exceeds the active power increase amount or the active power decrease amount of the DC voltage control operating converter, two active power coordination control schemes are included:

[0071] Scheme one:

[0072] According to the proportion of the active power increase amount or the active power decrease amount of each of the n-1 converters in the total of the active power increase amounts or the total of the active power decrease amounts of the n-1 converters, the active power increase variation or the active power decrease variation is borne, wherein the n-1 converters are the DC voltage control operating converters and the active power control operating converters except the active power control operating converter that performs power adjustment.

[0073] For example, when the external signal triggers the active power control operating converter x to perform power adjustment, if the adjustment amount ΔP x ≥ 0, the total active power decrease variation of the other converters of the multi-terminal flexible DC power transmission system is ΔP x When the active power decrease amount of the DC voltage control operating converter is ΔP , the DC voltage control operating converter bears all the active power decrease variation ΔP x ; if ΔP , the decrease amount is distributed according to the proportion of the decrease amount of the remaining operating converters, and the decrease amount allocated to each converter is ΔP , which is calculated according to the following formula:

[0074]

[0075] If ΔP x < 0, the total active power increase variation of the other converters of the multi-terminal flexible DC power transmission system is |ΔP x |, when the active power increase amount of the DC voltage control operating converter is ΔP , the DC voltage control operating converter bears all the total active power increase variation |ΔP x |; if ΔP , the increase amount is distributed according to the proportion of the increase amount of the remaining operating converters, and the increase amount allocated to each converter is ΔP , which is calculated according to the following formula:

[0076]

[0077] Scheme two:

[0078] According to the active power boostable amount or the active power reducible amount of the DC voltage control operating converter, the active power boost change amount or the active power reduction change amount is borne, and an active power first boost change amount or an active power first reduction change amount is obtained. According to the proportion of the active power boostable amount or the active power reducible amount of each active power control operating converter in the sum of the active power boostable amount or the active power reducible amount of the n-2 active power control operating converters, the active power boost change amount or the active power reduction change amount is borne. The n-2 active power control operating converters are the active power control operating converters other than the active power control operating converter performing power adjustment.

[0079] For example, when the external signal triggers the active power control operating converter x to perform power adjustment, if the adjustment amount ΔP x ≥ 0, the total active power reduction change amount of other converters of the multi-terminal flexible DC power transmission system caused is ΔP x When the active power reducible amount of the DC voltage control operating converter is ΔP x , the active power reduction change amount ΔP is borne by the DC voltage control operating converter entirely; if the active power reducible amount of the DC voltage control operating converter is ΔP x , the active power reduction change amount ΔP is borne by the DC voltage control operating converter according to the active power reducible amount ΔP x1 , and the active power first reduction change amount ΔP x is obtained by subtracting the active power reducible amount ΔP of the DC voltage control operating converter from the active power reduction change amount ΔP x , and the reducible amount of each converter is allocated according to the proportion of the reducible amount of the remaining operating converters.

[0080]

[0081] If ΔP x < 0, the total active power boost change amount of other converters of the multi-terminal flexible DC power transmission system caused is |ΔP x |, when the active power boostable amount of the DC voltage control operating converter is ΔP x , the total active power boost change amount |ΔP is borne by the DC voltage control operating converter entirely; if the active power boostable amount of the DC voltage control operating converter is ΔP x|Subtracting the active power of the DC voltage control operating converter can improve the amount Obtaining the first improved active power change amount |ΔP x1 |According to the proportion of the remaining operating converter, each converter is allocated an improved amount According to the following formula:

[0082]

[0083] According to an example embodiment, in the case of triggering the DC voltage control operating converter to perform power adjustment by receiving an external signal, the active power improved change amount or the active power reduced change amount of the multi-terminal flexible DC power transmission system caused by the power adjustment of the DC voltage control operating converter is determined. According to the proportion of the active power improved amount or the active power reduced amount of each of the n-1 active power control operating converters in the total of the active power improved amount or the total of the active power reduced amount of the n-1 active power control operating converters, the active power improved change amount or the active power reduced change amount is borne.

[0084] For example, when the external signal triggers the DC voltage control operating converter 1 to perform power adjustment, if the adjustment amount ΔP1≥0, the total active power reduced change amount of the other converters of the multi-terminal flexible DC power transmission system caused by the power adjustment is ΔP1, and the remaining operating converters are allocated according to the proportion of the reduced amount According to the following formula:

[0085]

[0086] If ΔP1≤0, the total active power improved amount of the other converters of the multi-terminal flexible DC power transmission system caused by the power adjustment is |ΔP1|, and the remaining operating converters are allocated according to the proportion of the improved amount According to the following formula:

[0087]

[0088] Step S104, generating and executing the instructions of each converter in the multi-terminal flexible DC power transmission system according to the allocated active power change amount.

[0089] According to an example embodiment, the allocated active power change amount is added to the active power of the corresponding operating control operating converter to form a new active power control instruction and is executed.

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

[0091] The operation data detection module is configured to detect the active power of each converter in the multi-terminal flexible HVDC power transmission system and calculate the active power increase amount and the active power decrease amount of each converter.

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

[0093] The coordinated distribution module is configured to distribute the active power change amount of the multi-terminal flexible HVDC power transmission system caused by the trigger condition according to the trigger condition, the active power increase amount and the active power decrease amount of each converter.

[0094] The active power change amount execution module is configured to generate and execute the instruction of each converter in the multi-terminal flexible HVDC power transmission system according to the distributed active power change amount.

[0095] The active power coordinated control system is configured to execute the active power coordinated control method as described above, and thus will not be described here.

[0096] The active power coordinated control method and system for the multi-terminal flexible HVDC power transmission system provided by the present application can fully utilize the real-time active power of the operating converter by judging the active power increase amount and the active power decrease amount of each converter and detecting the trigger condition for the active power adjustment, output different active instructions, automatically adjust the active power of multiple converters when the grid active power changes, maintain the power balance of the multi-terminal flexible converter, minimize the fluctuation of the DC voltage, and avoid DC overvoltage or under-voltage 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 teachings of the present disclosure, these principles can be applied to many other embodiments.

[0098] In addition, it should be noted that the above-described figures are only schematic illustrations of the processes included in the method according to the exemplary embodiments of the present application, and are not for limiting purposes. It is easy to understand that the processes shown in the above-described 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 executed synchronously or asynchronously, for example, in multiple modules.

[0099] The exemplary embodiments of this application are specifically illustrated and described herein. But, it is to be understood that the application is not limited to the details of the illustrated implementations; rather, this application is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. An active power coordinated control method for a multi-terminal flexible HVDC power transmission system, characterized in that, The multi-terminal flexible HVDC power transmission system includes n converters, one of the n converters is determined as a DC voltage control operation converter, n-1 of the n converters are determined as active power control operation converters, n is an integer greater than or equal to 3, and the active power coordination control method includes: detecting the active power of each converter in the multi-terminal flexible HVDC power transmission system, and calculating the active power increase amount and the active power decrease amount of each converter; determining a trigger condition for the active power coordination control of the multi-terminal flexible HVDC power transmission system, wherein the trigger condition includes: the active power control operation converter exits operation; the DC voltage control operation converter exits operation; an external signal triggering the active power control operation converter to adjust power; and / or an external signal triggering the DC voltage control operation converter to adjust power; according to the trigger condition, the active power increase amount and the active power decrease amount of each converter, the active power change amount of the multi-terminal flexible HVDC power transmission system caused by the trigger condition is allocated, including: in the case that the trigger condition is that the active power control operation converter exits operation, determining the active power increase change amount or the active power decrease change amount of the multi-terminal flexible HVDC power transmission system caused by the active power control operation converter exiting operation; judging whether the active power increase change amount or the active power decrease change amount of the multi-terminal flexible HVDC power transmission system exceeds the active power increase amount or the active power decrease amount of the DC voltage control operation converter; in the case that the active power increase change amount or the active power decrease change amount does not exceed the active power increase amount or the active power decrease amount of the DC voltage control operation converter, the DC voltage control operation converter bears the active power increase change amount or the active power decrease change amount; in the case that the active power increase change amount or the active power decrease change amount exceeds the active power increase amount or the active power decrease amount of the DC voltage control operation converter, according to the proportion of the active power increase amount or the active power decrease amount of each of the n-1 converters in the total sum of the active power increase amount or the active power decrease amount of the n-1 converters, the active power increase change amount or the active power decrease change amount is borne, wherein the n-1 converters are the DC voltage control operation converters and the active power control operation converters except the active power control operation converter that exits operation; generating and executing the instructions of each converter in the multi-terminal flexible HVDC power transmission system according to the allocated active power change amount.

2. The active power coordination control method of claim 1, wherein, The detection of the active power of each converter in the multi-terminal flexible HVDC power transmission system and the calculation of the active power increase amount and the active power decrease amount of each converter include: the active power increase amount of each converter is calculated according to the following formula: P r+j = P N+j - P j the active power decrease amount of each converter is calculated according to the following formula: P r-j = |P N-j -P j | where P j is the active power of the each converter, j = 1, 2,..., n, P r+j is the active power of the each converter, j = 1, 2,..., n, P N+j is the active power of the each converter, j = 1, 2,..., n, P r-j is the active power of the each converter, j = 1, 2,..., n, P N-j is the active power of the each converter, j = 1, 2,..., n, P 3. The active power coordination control method of claim 1, wherein, The method comprises the following steps: In the case that the trigger condition is that the active power control operating converter exits operation, determining the active power increase change or the active power decrease change of the multi-terminal flexible DC power transmission system caused by the active power control operating converter exiting operation; Determining whether the active power increase change or the active power decrease change of the multi-terminal flexible DC power transmission system exceeds the active power increase amount or the active power decrease amount of the DC voltage control operating converter; In the case that the active power increase change or the active power decrease change does not exceed the active power increase amount or the active power decrease amount of the DC voltage control operating converter, the DC voltage control operating converter bears the active power increase change or the active power decrease change; In the case that the active power increase change or the active power decrease change exceeds the active power increase amount or the active power decrease amount of the DC voltage control operating converter, the DC voltage control operating converter bears the active power increase change or the active power decrease change according to the active power increase amount or the active power decrease amount of the DC voltage control operating converter, and obtains the first active power increase change or the first active power decrease change; According to the proportion of the active power increase amount or the active power decrease amount of each of the n-2 active power control operating converters in the total of the active power increase amounts or the total of the active power decrease amounts of the n-2 active power control operating converters, the active power increase change or the active power decrease change is borne, wherein the n-2 active power control operating converters are the active power control operating converters other than the active power control operating converter exiting operation.

4. The active power coordination control method of claim 1, wherein, The method comprises the following steps: In the case that the trigger condition is that the DC voltage control operating converter exits operation, determining the active power increase change or the active power decrease change of the multi-terminal flexible DC power transmission system caused by the DC voltage control operating converter exiting operation; According to the proportion of the active power increase amount or the active power decrease amount of each of the n-1 active power control operating converters in the total of the active power increase amounts or the total of the active power decrease amounts of the n-1 active power control operating converters, the active power increase change or the active power decrease change is borne; In the case that the trigger condition is that the DC voltage control operating converter exits operation, determining the active power increase change or the active power decrease change of the multi-terminal flexible DC power transmission system caused by the DC voltage control operating converter exiting operation; According to the proportion of the active power increase amount or the active power decrease amount of each of the n-1 active power control operating converters in the total of the active power increase amounts or the total of the active power decrease amounts of the n-1 active power control operating converters, the active power increase change or the active power decrease change is borne; determining the n-1 active power control operating converters which are assigned the least active power increase change or active power decrease change as the updated DC voltage control operating converters.

5. The active power coordination control method of claim 1, wherein, The method for distributing the active power change of the multi-terminal VSC-MTDC caused by the trigger condition according to the trigger condition, the active power increase amount and the active power decrease amount of each converter comprises: In the case that the trigger condition is receiving an external signal to trigger the active power control operating converter to adjust power, determining the active power increase change or the active power decrease change of the multi-terminal VSC-MTDC caused by the power adjustment of the active power control operating converter; determining whether the active power increase change or the active power decrease change of the multi-terminal VSC-MTDC exceeds the active power increase amount or the active power decrease amount of the DC voltage control operating converter; In the case that the active power increase change or the active power decrease change does not exceed the active power increase amount or the active power decrease amount of the DC voltage control operating converter, the DC voltage control operating converter bears the active power increase change or the active power decrease change; In the case that the active power increase change or the active power decrease change exceeds the active power increase amount or the active power decrease amount of the DC voltage control operating converter, the active power increase change or the active power decrease change is borne according to the proportion of the active power increase amount or the active power decrease amount of each of the n-1 converters in the total of the active power increase amount or the active power decrease amount of the n-1 converters, wherein the n-1 converters are the DC voltage control operating converters and the active power control operating converters except the active power control operating converter which adjusts power.

6. The active power coordination control method of claim 1, wherein, The method for distributing the active power change of the multi-terminal VSC-MTDC caused by the trigger condition according to the trigger condition, the active power increase amount and the active power decrease amount of each converter comprises: In the case that the trigger condition is receiving an external signal to trigger the active power control operating converter to adjust power, determining the active power increase change or the active power decrease change of the multi-terminal VSC-MTDC caused by the power adjustment of the active power control operating converter; determining whether the active power increase change or the active power decrease change of the multi-terminal VSC-MTDC exceeds the active power increase amount or the active power decrease amount of the DC voltage control operating converter; In the case that the active power increase change or the active power decrease change does not exceed the active power increase amount or the active power decrease amount of the DC voltage control operating converter, the DC voltage control operating converter bears the active power increase change or the active power decrease change; In the case that the active power increase change or the active power decrease change exceeds the active power increase amount or the active power decrease amount of the DC voltage control operating converter, the active power increase change or the active power decrease change is borne according to the proportion of the active power increase amount or the active power decrease amount of each of the n-1 converters in the total of the active power increase amount or the active power decrease amount of the n-1 converters, wherein the n-1 converters are the DC voltage control operating converters and the active power control operating converters except the active power control operating converter which adjusts power. In the case that the active power increase change amount or the active power decrease change amount exceeds the active power increase amount or the active power decrease amount of the DC voltage control operating converter, the active power increase change amount or the active power decrease change amount is borne according to the proportion of the active power increase amount or the active power decrease amount of each of the n-2 active power control operating converters in the total of the active power increase amounts or the total of the active power decrease amounts of the n-2 active power control operating converters. In the case that the active power increase change amount or the active power decrease change amount exceeds the active power increase amount or the active power decrease amount of the DC voltage control operating converter, the active power increase change amount or the active power decrease change amount is borne according to the proportion of the active power increase amount or the active power decrease amount of each of the n-2 active power control operating converters in the total of the active power increase amounts or the total of the active power decrease amounts of the n-2 active power control operating converters.

7. The active power coordination control method of claim 1, wherein, The method comprises the following steps: In the case that the trigger condition is receiving an external signal to trigger the DC voltage control operating converter to perform power adjustment, the active power increase change amount or the active power decrease change amount of the multi-terminal VSC-MTDC system caused by the power adjustment of the DC voltage control operating converter is determined. The active power increase change amount or the active power decrease change amount is borne according to the proportion of the active power increase amount or the active power decrease amount of each of the n-1 active power control operating converters in the total of the active power increase amounts or the total of the active power decrease amounts of the n-1 active power control operating converters.

8. An active power coordinated control system for a multi-terminal flexible direct current power transmission system, characterized in that, The active power increase change amount or the active power decrease change amount is borne according to the proportion of the active power increase amount or the active power decrease amount of each of the n-2 active power control operating converters in the total of the active power increase amounts or the total of the active power decrease amounts of the n-2 active power control operating converters. The active power coordination control system comprises: An operating data detection module is configured to detect the active power of each converter in the multi-terminal VSC-MTDC system and calculate the active power increase amount and the active power decrease amount of each converter; A trigger condition detection module is configured to determine a trigger condition for performing active power coordination control on the multi-terminal VSC-MTDC system; A coordination distribution module is configured to distribute the active power change amount of the multi-terminal VSC-MTDC system caused by the trigger condition according to the trigger condition and the active power increase amount and the active power decrease amount of each converter; An active power change amount execution module is configured to generate and execute an instruction of each converter in the multi-terminal VSC-MTDC system according to the distributed active power change amount.

Images