A fault recovery control method, device and equipment for a multi-terminal direct current transmission system

Abstract

The present application relates to a fault recovery control method, apparatus, and equipment for a multi-terminal direct current (HVDC) transmission system. The fault recovery control method for the multi-terminal direct current (HVDC) transmission system controls the operation of each converter station in the multi-terminal direct current (HVDC) transmission system by using the power reference value upper limit and control mode of each converter station in the multi-terminal direct current (HVDC) transmission system. This method can achieve fault recovery at the corresponding converter station, avoid unreasonable power distribution among the converter stations after a fault in the multi-terminal direct current (HVDC) transmission system, and achieve power balance in the multi-terminal direct current (HVDC) transmission system. The fault recovery control method for the multi-terminal direct current (HVDC) transmission system also fully utilizes the power mutual assistance advantages of the multi-terminal direct current (HVDC) transmission system. In the case of limited converter station power, the method considers the power recovery capabilities of each receiving-end converter station to scientifically and rationally distribute direct current power after a fault. This method solves the technical problem of the relatively extensive and unscientific power distribution methods among converter stations in existing multi-terminal direct current systems after a fault.

Description

Technical Field

[0001] The present application relates to the technical field of multi-terminal direct current (HVDC) transmission, and in particular to a fault recovery control method, apparatus, and device for a multi-terminal direct current (HVDC) transmission system. Background Art

[0002] For DC converter stations with transient power limits lower than the rated power in existing DC transmission systems, measures such as limiting DC power or adding dynamic reactive power compensation equipment are often required to ensure normal recovery of the DC transmission system after a fault. However, these measures are not economical.

[0003] A key issue that needs to be addressed in multi-terminal HVDC transmission system control is the distribution of power among converter stations. Common power control methods for converter stations in multi-terminal HVDC transmission systems include master-slave control and droop control. These two power control strategies are independent of communication between converter stations. Their advantages lie in their simplicity and high reliability. However, these methods are relatively crude, lacking sufficient consideration of various influencing factors, and their power distribution principles and methods are not scientifically sound. For example, in both master-slave control and droop control, power distribution is not considered in light of factors such as the operating status and power margin of the converter stations at each end. Summary of the Invention

[0004] The embodiments of the present application provide a fault recovery control method, device and equipment for a multi-terminal direct current transmission system, which are used to solve the technical problem that the power allocation method of each converter station in the existing multi-terminal direct current system is relatively extensive and unscientific after a fault occurs.

[0005] In order to achieve the above objectives, the embodiments of the present application provide the following technical solutions:

[0006] In one aspect, a fault recovery control method for a multi-terminal direct current transmission system is provided, comprising the following steps:

[0007] Obtaining pre-fault DC power and post-fault recovery information of each receiving-end converter station in a multi-terminal DC transmission system, and setting reference power data, the reference power data including an initial reference power upper limit and a reference power step;

[0008] Calculating, using a fault recovery simulation rule according to the recovery information of the receiving-end converter station and the reference power data, a maximum recoverable power and a power recovery margin corresponding to the receiving-end converter station;

[0009] After a fault occurs in a converter station, the converter stations of the multi-terminal direct current transmission system are divided into a fault receiving-end converter station, a sending-end converter station, and a plurality of non-fault receiving-end converter stations; a fault receiving-end control strategy is adopted to perform processing according to the DC power, the maximum recoverable power, and the power recovery margin of the fault receiving-end converter station, to obtain a first power reference value upper limit and a first control mode of the fault receiving-end converter station; a sending-end control strategy is adopted to perform processing according to the maximum recoverable power and the power recovery margin of the fault receiving-end converter station and the non-fault receiving-end converter station, to obtain a second power reference value upper limit and a second control mode of the sending-end converter station; a non-fault receiving-end control strategy is adopted to perform processing according to the power recovery margin and the DC power of each non-fault receiving-end converter station, to obtain a third power reference value upper limit and a third control mode corresponding to the non-fault receiving-end converter station;

[0010] The operation of the faulty receiving-end converter station is controlled according to the first power reference value upper limit and the first control mode; the operation of the sending-end converter station is controlled according to the second power reference value upper limit and the second control mode; and the operation of the corresponding non-faulty receiving-end converter station is controlled according to the third power reference value upper limit and the third control mode.

[0011] Preferably, the content of the fault recovery simulation rule includes:

[0012] If the recovery information of the receiving converter station indicates that the DC power of the receiving converter station cannot be normally restored after the fault, updating the reference power upper limit value of the receiving converter station in a decreasing manner according to the initial reference power upper limit value and the reference power step size to obtain a first reference power upper limit adjustment value; and performing a short circuit fault simulation on the receiving converter station according to the first reference power upper limit adjustment value to obtain a simulation result;

[0013] If the simulation result shows that the DC power of the receiving converter station cannot be normally restored, the first reference power upper limit adjustment value is used as the new initial reference power upper limit value, the reference power upper limit value of the receiving converter station is updated in a decreasing manner according to the first reference power upper limit adjustment value and the reference power step size to obtain a first reference power upper limit update value, and a short-circuit fault simulation is performed on the receiving converter station according to the first reference power upper limit update value until the simulation result shows that the DC power of the receiving converter station is normally restored;

[0014] If the DC power of the receiving-end converter station is restored normally according to the simulation result, the first reference power upper limit adjustment value or the first reference power upper limit update value corresponding to the normal restoration of the DC power of the receiving-end converter station is used as the maximum restorable power of the receiving-end converter station;

[0015] The power recovery margin corresponding to the receiving-end converter station is obtained according to the maximum recoverable power of each receiving-end converter station and the DC power.

[0016] Preferably, the content of the fault recovery simulation rule includes:

[0017] If the recovery information of the receiving converter station indicates that the DC power of the receiving converter station has recovered normally after the fault, incrementally updating the reference power upper limit value of the receiving converter station according to the initial reference power upper limit value and the reference power step size to obtain a second reference power upper limit adjustment value; performing a short-circuit fault simulation on the receiving converter station according to the second reference power upper limit adjustment value to obtain a simulation result;

[0018] If the simulation result shows that the DC power of the receiving converter station has been restored normally, the second reference power upper limit adjustment value is used as the new initial reference power upper limit value, and the reference power upper limit value of the receiving converter station is incrementally updated according to the second reference power upper limit adjustment value and the reference power step size to obtain a second reference power upper limit update value; and a short circuit fault simulation is performed on the receiving converter station according to the second reference power upper limit update value until the simulation result shows that the DC power of the receiving converter station cannot be restored normally.

[0019] According to the simulation result, the DC power of the receiving-end converter station cannot be restored normally, using the initial reference power upper limit value or the second reference power upper limit update value of the last DC power normal recovery simulation corresponding to the DC power of the receiving-end converter station being unable to be restored normally as the maximum restorable power of the receiving-end converter station;

[0020] The power recovery margin corresponding to the receiving-end converter station is obtained according to the maximum recoverable power of each receiving-end converter station and the DC power.

[0021] Preferably, the process of adopting a fault receiving-end control strategy to process the DC power, the maximum restorable power, and the power restoration margin of the fault receiving-end converter station to obtain a first power reference value upper limit and a first control mode of the fault receiving-end converter station includes:

[0022] Obtaining a control mode of the fault receiving-end converter station before the fault;

[0023] If the power recovery margin of the fault receiving-end converter station is not less than zero, the DC power of the fault receiving-end converter station before the fault is used as the first power reference value upper limit, and the control mode of the fault receiving-end converter station before the fault is used as the first control mode;

[0024] If the power recovery margin of the fault receiving converter station is less than zero, the maximum recoverable power of the fault receiving converter station is used as the upper limit of the first power reference value, and the first control mode of the fault receiving converter station is a fixed DC power control mode.

[0025] Preferably, the sending-end control strategy is used to process the maximum restorable power and the power restoration margin of the faulty receiving-end converter station and the non-faulty receiving-end converter station to obtain the second power reference value upper limit and the second control mode of the sending-end converter station, including:

[0026] According to the power recovery margins of the non-fault receiving-end converter stations, the non-fault receiving-end converter stations satisfying the power recovery margin being greater than zero are screened out to obtain a converter station set;

[0027] Calculating the total power recovery margin based on the power recovery margins of all the non-fault receiving-end converter stations in the converter station set; and calculating the limited power based on the DC power and the maximum recoverable power of the fault receiving-end converter station;

[0028] Obtaining the sending-end DC power of the sending-end converter station before a fault occurs; based on the total power recovery margin being not less than the limited power, using the sending-end DC power of the sending-end converter station as the upper limit of the second power reference value, and setting the second control mode of the sending-end converter station to a fixed DC power control mode;

[0029] The sending-end power reference value is calculated based on the sending-end DC power, the limited power and the total power recovery margin; based on the total power recovery margin being less than the limited power, the sending-end power reference value of the sending-end converter station is used as the upper limit of the second power reference value, and the second control mode of the sending-end converter station is a fixed DC power control mode.

[0030] Preferably, the non-fault receiving-end control strategy is adopted to process the power recovery margin and the DC power of each non-fault receiving-end converter station to obtain the third power reference value upper limit and the third control mode corresponding to the non-fault receiving-end converter station, including:

[0031] If the power recovery margin of each of the non-fault receiving-end converter stations is less than zero, the DC power of the corresponding non-fault receiving-end converter station before the fault is used as the upper limit of the third power reference value, and the third control mode corresponding to the non-fault receiving-end converter station is a fixed DC power control mode;

[0032] If the power recovery margin of each non-fault receiving-end converter station is not less than zero, the DC voltage change of the non-fault receiving-end converter station before and after the fault is obtained, and the recovery power reference value of the non-fault receiving-end converter station is calculated based on the DC power, the power recovery margin and the DC voltage change of the non-fault receiving-end converter station; the recovery power reference value of the non-fault receiving-end converter station is used as the upper limit of the third power reference value, and the third control mode of the non-fault receiving-end converter station is the DC power-DC voltage droop control mode.

[0033] In yet another aspect, a fault recovery control device for a multi-terminal direct current transmission system is provided, comprising a data acquisition module, a calculation module, a recovery data acquisition module, and a fault recovery execution module;

[0034] The data acquisition module is used to obtain the DC power before the fault and the recovery information after the fault of each receiving-end converter station in the multi-terminal DC transmission system, and set reference power data, wherein the reference power data includes an initial reference power upper limit value and a reference power step size;

[0035] The calculation module is configured to calculate, based on the recovery information of the receiving-end converter station and the reference power data, using a fault recovery simulation rule to obtain a maximum recoverable power and a power recovery margin corresponding to the receiving-end converter station;

[0036] The recovery data acquisition module is configured to divide the converter stations of the multi-terminal direct current transmission system into a faulty receiving-end converter station, a sending-end converter station, and a plurality of non-faulty receiving-end converter stations according to a fault at the converter station; adopt a faulty receiving-end control strategy to perform processing based on the DC power, the maximum recoverable power, and the power recovery margin of the faulty receiving-end converter station to obtain a first power reference value upper limit and a first control mode of the faulty receiving-end converter station; adopt a sending-end control strategy to perform processing based on the maximum recoverable power and the power recovery margin of the faulty receiving-end converter station and the non-faulty receiving-end converter station to obtain a second power reference value upper limit and a second control mode of the sending-end converter station; adopt a non-faulty receiving-end control strategy to perform processing based on the power recovery margin and the DC power of each non-faulty receiving-end converter station to obtain a third power reference value upper limit and a third control mode corresponding to the non-faulty receiving-end converter station;

[0037] The fault recovery execution module is used to control the operation of the faulty receiving-end converter station according to the first power reference value upper limit and the first control mode; control the operation of the sending-end converter station according to the second power reference value upper limit and the second control mode; and control the operation of the corresponding non-faulty receiving-end converter station according to the third power reference value upper limit and the third control mode.

[0038] Preferably, the content of the fault recovery simulation rule includes:

[0039] If the recovery information of the receiving converter station indicates that the DC power of the receiving converter station cannot be normally restored after the fault, updating the reference power upper limit value of the receiving converter station in a decreasing manner according to the initial reference power upper limit value and the reference power step size to obtain a first reference power upper limit adjustment value; and performing a short circuit fault simulation on the receiving converter station according to the first reference power upper limit adjustment value to obtain a simulation result;

[0040] If the simulation result shows that the DC power of the receiving converter station cannot be normally restored, the first reference power upper limit adjustment value is used as the new initial reference power upper limit value, the reference power upper limit value of the receiving converter station is updated in a decreasing manner according to the first reference power upper limit adjustment value and the reference power step size to obtain a first reference power upper limit update value, and a short-circuit fault simulation is performed on the receiving converter station according to the first reference power upper limit update value until the simulation result shows that the DC power of the receiving converter station is normally restored;

[0041] If the DC power of the receiving-end converter station is restored normally according to the simulation result, the first reference power upper limit adjustment value or the first reference power upper limit update value corresponding to the normal restoration of the DC power of the receiving-end converter station is used as the maximum restorable power of the receiving-end converter station;

[0042] Calculating, based on the maximum recoverable power of each receiving-end converter station and the DC power, to obtain a power recovery margin corresponding to the receiving-end converter station;

[0043] or

[0044] If the recovery information of the receiving converter station indicates that the DC power of the receiving converter station has recovered normally after the fault, incrementally updating the reference power upper limit value of the receiving converter station according to the initial reference power upper limit value and the reference power step size to obtain a second reference power upper limit adjustment value; performing a short-circuit fault simulation on the receiving converter station according to the second reference power upper limit adjustment value to obtain a simulation result;

[0045] If the simulation result shows that the DC power of the receiving converter station has been restored normally, the second reference power upper limit adjustment value is used as the new initial reference power upper limit value, and the reference power upper limit value of the receiving converter station is incrementally updated according to the second reference power upper limit adjustment value and the reference power step size to obtain a second reference power upper limit update value; and a short circuit fault simulation is performed on the receiving converter station according to the second reference power upper limit update value until the simulation result shows that the DC power of the receiving converter station cannot be restored normally.

[0046] According to the simulation result, the DC power of the receiving-end converter station cannot be restored normally, using the initial reference power upper limit value or the second reference power upper limit update value of the last DC power normal recovery simulation corresponding to the DC power of the receiving-end converter station being unable to be restored normally as the maximum restorable power of the receiving-end converter station;

[0047] The power recovery margin corresponding to the receiving-end converter station is obtained according to the maximum recoverable power of each receiving-end converter station and the DC power.

[0048] Preferably, the content of the fault receiving end control strategy includes:

[0049] Obtaining a control mode of the fault receiving-end converter station before the fault;

[0050] If the power recovery margin of the fault receiving-end converter station is not less than zero, the DC power of the fault receiving-end converter station before the fault is used as the first power reference value upper limit, and the control mode of the fault receiving-end converter station before the fault is used as the first control mode;

[0051] If the power recovery margin of the fault receiving-end converter station is less than zero, the maximum recoverable power of the fault receiving-end converter station is used as the upper limit of the first power reference value, and the first control mode of the fault receiving-end converter station is a fixed DC power control mode;

[0052] The content of the sending end control strategy includes:

[0053] According to the power recovery margins of the non-fault receiving-end converter stations, the non-fault receiving-end converter stations satisfying the power recovery margin being greater than zero are screened out to obtain a converter station set;

[0054] Calculating the total power recovery margin based on the power recovery margins of all the non-fault receiving-end converter stations in the converter station set; and calculating the limited power based on the DC power and the maximum recoverable power of the fault receiving-end converter station;

[0055] Obtaining the sending-end DC power of the sending-end converter station before a fault occurs; based on the total power recovery margin being not less than the limited power, using the sending-end DC power of the sending-end converter station as the upper limit of the second power reference value, and setting the second control mode of the sending-end converter station to a fixed DC power control mode;

[0056] a sending-end power reference value is calculated based on the sending-end DC power, the limited power, and the total power recovery margin; based on the total power recovery margin being less than the limited power, the sending-end power reference value of the sending-end converter station is used as the upper limit of the second power reference value, and the second control mode of the sending-end converter station is a fixed DC power control mode;

[0057] The content of the non-fault receiving end control strategy includes:

[0058] If the power recovery margin of each of the non-fault receiving-end converter stations is less than zero, the DC power of the corresponding non-fault receiving-end converter station before the fault is used as the upper limit of the third power reference value, and the third control mode corresponding to the non-fault receiving-end converter station is a fixed DC power control mode;

[0059] If the power recovery margin of each non-fault receiving-end converter station is not less than zero, the DC voltage change of the non-fault receiving-end converter station before and after the fault is obtained, and the recovery power reference value of the non-fault receiving-end converter station is calculated based on the DC power, the power recovery margin and the DC voltage change of the non-fault receiving-end converter station; the recovery power reference value of the non-fault receiving-end converter station is used as the upper limit of the third power reference value, and the third control mode of the non-fault receiving-end converter station is the DC power-DC voltage droop control mode.

[0060] In another aspect, a terminal device is provided, comprising a processor and a memory;

[0061] The memory is used to store program code and transmit the program code to the processor;

[0062] The processor is configured to execute the above-mentioned fault recovery control method for a multi-terminal direct current transmission system according to the instructions in the program code.

[0063] The fault recovery control method, device and equipment of the multi-terminal direct current transmission system include obtaining the DC power before the fault and the recovery information after the fault of each receiving-end converter station in the multi-terminal direct current transmission system, and setting reference power data, wherein the reference power data includes an initial reference power upper limit value and a reference power step size; using the fault recovery simulation rule to calculate according to the recovery information and reference power data of each receiving-end converter station, the maximum recoverable power and power recovery margin of the corresponding receiving-end converter station are obtained; after the fault occurs in the converter station, the converter stations of the multi-terminal direct current transmission system are divided into a fault receiving-end converter station, a sending-end converter station and a plurality of non-fault receiving-end converter stations; and using the fault receiving-end control strategy to process according to the DC power, maximum recoverable power and power recovery margin of the fault receiving-end converter station, to obtain A first power reference value upper limit and a first control mode for the faulty receiving-end converter station; processing using a sending-end control strategy based on the maximum recoverable power and power recovery margin of the faulty receiving-end converter station and the non-faulty receiving-end converter station to obtain a second power reference value upper limit and a second control mode for the sending-end converter station; processing using a non-faulty receiving-end control strategy based on the power recovery margin and DC power of each non-faulty receiving-end converter station to obtain a third power reference value upper limit and a third control mode for the corresponding non-faulty receiving-end converter station; controlling the operation of the faulty receiving-end converter station based on the first power reference value upper limit and the first control mode; controlling the operation of the sending-end converter station based on the second power reference value upper limit and the second control mode; and controlling the operation of the corresponding non-faulty receiving-end converter station based on the third power reference value upper limit and the third control mode. As can be seen from the above technical solutions, the embodiments of the present application have the following advantages: the fault recovery control method for a multi-terminal DC transmission system controls the operation of the corresponding converter station through the power reference value upper limit and control mode of each converter station in the multi-terminal DC transmission system, thereby achieving fault recovery of the corresponding converter station, avoiding unreasonable power distribution among the converter stations after a fault in the multi-terminal DC transmission system, and achieving power balance in the multi-terminal DC transmission system; the fault recovery control method for a multi-terminal DC transmission system also fully utilizes the power mutual assistance advantage of the multi-terminal DC transmission system. In the case of limited converter station power, the power recovery capability of each receiving-end converter station is taken into account to scientifically and reasonably distribute the DC power after the fault, thereby solving the technical problem that the power distribution method of each converter station in the existing multi-terminal DC transmission system after a fault occurs is relatively extensive and unscientific. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0065] Figure 1This is a flowchart of the steps of the fault recovery control method of the multi-terminal direct current transmission system according to an embodiment of the present application;

[0066] Figure 2 This is a flow chart of the fault recovery simulation rules in the fault recovery control method for a multi-terminal direct current transmission system according to an embodiment of the present application;

[0067] Figure 3 This is a flow chart of the fault receiving-end control strategy and the sending-end control strategy in the fault recovery control method of the multi-terminal direct current transmission system according to an embodiment of the present application;

[0068] Figure 4 This is a flow chart of the control strategy for the non-fault receiving end in the fault recovery control method for the multi-terminal direct current transmission system according to an embodiment of the present application;

[0069] Figure 5 This is a schematic diagram of the framework of the fault recovery control device for the multi-terminal direct current transmission system according to an embodiment of the present application;

[0070] Figure 6 This is a schematic diagram of the terminal device described in an embodiment of the present application. DETAILED DESCRIPTION

[0071] In order to make the purpose, features, and advantages of the invention of this application more obvious and easy to understand, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the embodiments described below are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0072] In the description of the embodiments of the present application, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0073] In the embodiments of the present application, unless otherwise expressly specified or limited, the terms "installed," "connected," "connected," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections, electrical connections; direct connections, or indirect connections through an intermediate medium; and can refer to internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the embodiments of the present application based on specific circumstances.

[0074] In this application, when a DC converter station feeds into an AC system, when an AC system fault occurs, it may cause a DC power interruption. During the recovery process, the DC power of this power grid system may not be able to recover to the power level before the fault due to insufficient dynamic reactive power, overvoltage, etc., that is, the DC transient stable operating power limit is lower than its steady-state operating power.

[0075] Multi-terminal DC transmission systems offer advantages such as flexible operation. Currently, the primary control method for multi-terminal DC transmission systems is master-slave control. For example, a multi-terminal DC transmission system consists of one converter station controlling DC voltage (also known as a voltage-controlled station) and multiple converter stations controlling DC power (also known as power-controlled stations). When the power of the power-controlled station changes, the DC voltage fluctuates. To maintain a constant DC voltage, the voltage-controlled station adjusts its power, absorbing power fluctuations and achieving power balance. Droop control is also a common method in multi-terminal DC transmission systems. In droop control, the converter stations at each end no longer maintain a constant DC voltage. Instead, they employ power control or power-DC voltage droop control (i.e., a linear relationship is established between DC power and DC voltage). When the power of a converter station fluctuates, the DC voltage changes, and the power of the converter station using droop control changes. The power fluctuation is absorbed by all converter stations using droop control, thus maintaining power balance.

[0076] The embodiments of the present application provide a fault recovery control method, device and equipment for a multi-terminal direct current transmission system, which solves the technical problem that the power allocation method for each converter station in the existing multi-terminal direct current system is relatively extensive and unscientific after a fault occurs.

[0077] Example 1:

[0078] Figure 1 This is a flowchart of the steps of the fault recovery control method for a multi-terminal direct current transmission system described in an embodiment of the present application.

[0079] like Figure 1 As shown, the embodiment of the present application provides a fault recovery control method for a multi-terminal direct current transmission system, comprising the following steps:

[0080] S1. Obtain the DC power before a fault and the recovery information after a fault at each receiving-end converter station in the multi-terminal DC transmission system, and set reference power data, which includes an initial reference power upper limit and a reference power step.

[0081] It should be noted that in step S1, the multi-terminal DC transmission system is simulated to obtain data on the recovery capability of each receiving-end converter station of the multi-terminal DC transmission system after a fault occurs. The data includes the DC power of each receiving-end converter station before the fault and the reference power data of each receiving-end converter station after the fault. In this embodiment, the DC power of each receiving-end converter station is recorded as P0, and the initial reference power upper limit value of each receiving-end converter station is recorded as P refLim The reference power step length of each receiving converter station is recorded as △P ref The fault recovery control method of the multi-terminal direct current transmission system is described by taking a multi-terminal direct current transmission system including a plurality of receiving-end converter stations and a sending-end converter station as an example.

[0082] S2. Calculate the maximum recoverable power and power recovery margin of the corresponding receiving converter station using the fault recovery simulation rule based on the recovery information and reference power data of each receiving converter station.

[0083] It should be noted that in step S2, the DC power and reference power data of each receiving converter station are obtained according to step S1, and the maximum recoverable power P of the corresponding receiving converter station is calculated using the fault recovery simulation rule. Lim and power recovery margin △P recover According to the maximum recoverable power and power recovery margin of each receiving converter station, the recovery capability of each receiving converter station after a fault occurs is known. In this embodiment, an AC system fault is set in the vicinity of the receiving converter station. The fault type is determined by relevant regulations or dispatching control requirements. After the fault, the DC reference power upper limit of the receiving converter station remains unchanged. The maximum recoverable power P of each receiving converter station is calculated based on the power recovery status of the converter station after the fault. Lim The fault recovery control method of the multi-terminal direct current transmission system is used to measure the power recovery potential of the converter station after a fault occurs based on the maximum recoverable power and power recovery margin of the receiving-end converter station.

[0084] S3. After a fault occurs in a converter station, the converter stations of the multi-terminal DC transmission system are divided into a fault receiving-end converter station, a sending-end converter station and a plurality of non-fault receiving-end converter stations; a fault receiving-end control strategy is adopted to process the DC power, maximum recoverable power and power recovery margin of the fault receiving-end converter station to obtain a first power reference value upper limit and a first control mode of the fault receiving-end converter station; a sending-end control strategy is adopted to process the maximum recoverable power and power recovery margin of the fault receiving-end converter station and the non-fault receiving-end converter station to obtain a second power reference value upper limit and a second control mode of the sending-end converter station; a non-fault receiving-end control strategy is adopted to process the power recovery margin and DC power of each non-fault receiving-end converter station to obtain a third power reference value upper limit and a third control mode of the corresponding non-fault receiving-end converter station.

[0085] It should be noted that in step S3, after a fault occurs on the AC side of a converter station in the MTDC system, the converter stations are divided into a faulty receiving-end converter station, a sending-end converter station, and multiple non-faulty receiving-end converter stations. Subsequently, the maximum recoverable power and power recovery margin of each receiving-end converter station calculated in step S2 are used to determine the control mode and power reference upper limit for the faulty receiving-end converter station, the sending-end converter station, and each non-faulty receiving-end converter station.

[0086] S4. Control the operation of the faulty receiving-end converter station according to the first power reference value upper limit and the first control mode; control the operation of the sending-end converter station according to the second power reference value upper limit and the second control mode; and control the operation of the corresponding non-faulty receiving-end converter station according to the third power reference value upper limit and the third control mode.

[0087] It should be noted that, in step S4, the upper limit of the power reference value of each converter station in the multi-terminal DC transmission system and the control mode are obtained according to step S3 to control the operation of the corresponding converter station, so that fault recovery of the corresponding converter station can be achieved, thereby avoiding unreasonable power distribution among the converter stations after a fault occurs in the multi-terminal DC transmission system and achieving power balance in the multi-terminal DC transmission system.

[0088] The present application provides a fault recovery control method for a multi-terminal direct current transmission system, the method comprising obtaining the DC power before a fault and the recovery information after a fault of each receiving-end converter station in the multi-terminal direct current transmission system, and setting reference power data, the reference power data including an initial reference power upper limit value and a reference power step size; calculating using a fault recovery simulation rule based on the recovery information and reference power data of each receiving-end converter station to obtain the maximum recoverable power and power recovery margin of the corresponding receiving-end converter station; dividing the converter stations of the multi-terminal direct current transmission system into a faulty receiving-end converter station, a sending-end converter station, and a plurality of non-faulty receiving-end converter stations according to the occurrence of a fault in the converter station; processing using a faulty receiving-end control strategy based on the DC power, maximum recoverable power, and power recovery margin of the faulty receiving-end converter station to obtain The first power reference value upper limit and the first control mode of the faulty receiving-end converter station are determined; the sending-end control strategy is used to process the maximum recoverable power and power recovery margin of the faulty receiving-end converter station and the non-faulty receiving-end converter station, and the second power reference value upper limit and the second control mode of the sending-end converter station are obtained; the non-faulty receiving-end control strategy is used to process the power recovery margin and DC power of each non-faulty receiving-end converter station, and the third power reference value upper limit and the third control mode of the corresponding non-faulty receiving-end converter station are obtained; the operation of the faulty receiving-end converter station is controlled according to the first power reference value upper limit and the first control mode; the operation of the sending-end converter station is controlled according to the second power reference value upper limit and the second control mode; the operation of the corresponding non-faulty receiving-end converter station is controlled according to the third power reference value upper limit and the third control mode. The fault recovery control method for a multi-terminal direct current (HVDC) system controls the operation of corresponding converter stations through the power reference value upper limit and control mode of each converter station in the multi-terminal direct current (HVDC) system, thereby achieving fault recovery of the corresponding converter stations. This avoids unreasonable power distribution among the converter stations after a fault occurs in the multi-terminal direct current (HVDC) system, thereby achieving power balance in the multi-terminal direct current (HVDC) system. The fault recovery control method for a multi-terminal direct current (HVDC) system also fully utilizes the power mutual assistance advantage of the multi-terminal direct current (HVDC) system. In response to the power limitation of the converter stations, the method considers the power recovery capability of each receiving-end converter station and scientifically and reasonably distributes the DC power after the fault occurs. This method solves the technical problem of the relatively extensive and unscientific power distribution method among the converter stations in existing multi-terminal direct current systems after a fault occurs.

[0089] Figure 2 This is a flow chart of the fault recovery simulation rules in the fault recovery control method for a multi-terminal direct current transmission system according to an embodiment of the present application.

[0090] like Figure 2 As shown, in one embodiment of the present application, the content of the fault recovery simulation rule includes:

[0091] If the recovery information of the receiving-end converter station indicates that the DC power of the receiving-end converter station cannot be normally restored after the fault, the reference power upper limit value of the receiving-end converter station is updated in a decreasing manner according to the initial reference power upper limit value and the reference power step size to obtain a first reference power upper limit adjustment value; and a short-circuit fault simulation is performed on the receiving-end converter station according to the first reference power upper limit adjustment value to obtain a simulation result.

[0092] According to a simulation result indicating that the DC power of the receiving-end converter station cannot be normally restored, the first reference power upper limit adjustment value is used as a new initial reference power upper limit value, the reference power upper limit value of the receiving-end converter station is updated in a decreasing manner according to the first reference power upper limit adjustment value and the reference power step size to obtain a first reference power upper limit update value, and a short-circuit fault simulation is performed on the receiving-end converter station according to the first reference power upper limit update value until a simulation result indicating that the DC power of the receiving-end converter station is normally restored is obtained;

[0093] If the DC power of the receiving-end converter station is restored normally according to the simulation result, the first reference power upper limit adjustment value or the first reference power upper limit update value corresponding to the normal restoration of the DC power of the receiving-end converter station is used as the maximum restorable power of the receiving-end converter station;

[0094] Calculating, based on the maximum recoverable power of each receiving-end converter station and the DC power, a power recovery margin corresponding to the receiving-end converter station;

[0095] or

[0096] If the recovery information of each receiving converter station indicates that the DC power of the receiving converter station has been restored normally after the fault, the reference power upper limit value of the receiving converter station is incrementally updated according to the initial reference power upper limit value and the reference power step size to obtain a second reference power upper limit adjustment value; and a short circuit fault simulation is performed on the receiving converter station according to the second reference power upper limit adjustment value to obtain a simulation result.

[0097] If the simulation result shows that the DC power of the receiving-end converter station has been restored normally, the second reference power upper limit adjustment value is used as a new initial reference power upper limit value, and the reference power upper limit value of the receiving-end converter station is incrementally updated according to the second reference power upper limit adjustment value and the reference power step size to obtain a second reference power upper limit update value; a short-circuit fault simulation is performed on the receiving-end converter station according to the second reference power upper limit update value until a simulation result shows that the DC power of the receiving-end converter station cannot be restored normally;

[0098] According to the simulation result, the DC power of the receiving-end converter station cannot be restored normally, the initial reference power upper limit value or the second reference power upper limit update value of the last DC power normal recovery simulation corresponding to the DC power of the receiving-end converter station cannot be restored normally is used as the maximum recoverable power of the receiving-end converter station;

[0099] The power recovery margin of the corresponding receiving-end converter station is obtained based on the maximum recoverable power and DC power of each receiving-end converter station.

[0100] It should be noted that after a fault occurs at a receiving-end converter station in a multi-terminal DC transmission system, if the power at the receiving-end converter station cannot be restored normally through the fault recovery simulation rules, the DC power of the corresponding receiving-end converter station can be restored by lowering the reference power upper limit, thereby avoiding DC blocking of the corresponding receiving-end converter station and reducing the power loss of the receiving-end converter station; it also avoids limiting DC power during steady-state operation and saves the investment in installing reactive compensation equipment in the multi-terminal DC transmission system; and it also allows the fault recovery control method of the multi-terminal DC transmission system to give full play to the advantages of power regulation in the multi-terminal DC transmission system through the fault recovery simulation rules.

[0101] In the embodiments of this application, Figure 2 As shown, if the DC power of the receiving converter station cannot be restored normally after the fault, the receiving converter station is simulated. The simulation content includes: first, the operation of the receiving converter station is set to the DC power P0 before the fault, and the AC system fault is set. After the fault, the first reference power upper limit adjustment value P of the receiving converter station is adjusted. refLim1 According to the initial reference power upper limit value P refLim0 Reduce △P ref If the DC power of the receiving converter station cannot be restored, continue the next simulation and continue to reduce the reference power step △P ref Get the first reference power upper limit update value P refLimk , P refLimk =P refLimk-1 -△P ref , k is the number of simulations, and the simulation ends when the DC power of the receiving converter station is restored normally. The first reference power upper limit adjustment value or the first reference power upper limit update value at which the DC power in the receiving converter station can be restored normally is used as the maximum recoverable power P of the receiving converter station. Lim .

[0102] In the embodiments of this application, Figure 2 As shown, if the DC power of the receiving converter station can be restored normally after the fault, the receiving converter station is simulated. The simulation content includes: first, the operation of the receiving converter station is set to the DC power P0 before the fault, and the AC system fault is set. After the fault, the second reference power upper limit adjustment value P of the receiving converter station is adjusted. refLim1 'According to the initial reference power upper limit value P refLim0 Increase △P ref If the DC power of the receiving converter station is restored normally, the next simulation will continue at the reference power step △P refIncrease to obtain the second reference power upper limit update value P refLimk ′,P refLimk ′=P refLimk-1 ′-△P ref , k is the number of simulations, until the DC power of the receiving converter station cannot be restored normally, then the simulation ends. refLim0 Or the DC power in the receiving converter station cannot be restored normally. The DC power of the receiving converter station obtained in the last simulation can be restored to normal. The second reference power upper limit update value is used as the maximum recoverable power P of the receiving converter station. Lim For example, if P refLimk ′ is used as the upper limit of the DC power reference of the receiving converter station to simulate the AC fault. The simulation result shows that the DC power of the receiving converter station cannot be restored normally. The maximum recoverable power P of the receiving converter station is Lim =P refLimk-1 ′,P refLimk-1 ' is the second reference power upper limit update value when the DC power in the receiving-end converter station cannot be restored normally and the DC power can be restored to normal in the last simulation.

[0103] In the embodiments of this application, Figure 2 As shown, according to the DC power P0 of the receiving converter station and the maximum recoverable power P Lim Continue to calculate the power recovery margin △P of the receiving converter station recover =P Lim -P0.

[0104] It should be noted that when calculating the maximum recoverable power and power recovery margin of a receiving-end converter station using the fault recovery simulation rules, to eliminate the impact of non-faulty converter stations, all converter stations in the MTDC system, except the faulty receiving-end converter station, must maintain stable operation. If the remaining converter stations in the MTDC system cannot operate stably, methods such as connecting to an infinite power source can be used to maintain stable operation of the corresponding converter stations, ensuring the accuracy and precision of the calculated maximum recoverable power and power recovery margin of the receiving-end converter station.

[0105] Figure 3 This is a flow chart of the fault receiving-end control strategy and the sending-end control strategy in the fault recovery control method of the multi-terminal direct current transmission system described in an embodiment of the present application.

[0106] like Figure 3 As shown, in one embodiment of the present application, a fault receiving-end control strategy is adopted to process the DC power, maximum recoverable power, and power recovery margin of the fault receiving-end converter station, and a first power reference value upper limit and a first control mode of the fault receiving-end converter station are obtained, including:

[0107] Obtain the control mode of the fault receiving converter station before the fault;

[0108] If the power recovery margin of the fault receiving-end converter station is not less than zero, the DC power of the fault receiving-end converter station before the fault is used as the upper limit of the first power reference value, and the control mode of the fault receiving-end converter station before the fault is used as the first control mode;

[0109] If the power recovery margin of the fault receiving end converter station is less than zero, the maximum recoverable power of the fault receiving end converter station is used as the upper limit of the first power reference value, and the first control mode of the fault receiving end converter station is the fixed DC power control mode.

[0110] It should be noted that, after a converter station failure occurs, the converter stations of the multi-terminal DC transmission system are divided into a fault receiving-end converter station i, a sending-end converter station, and a plurality of non-fault receiving-end converter stations. In this embodiment, assuming that a fault occurs on the AC side of the i-th receiving-end converter station, the maximum recoverable power P of the fault receiving-end converter station i is obtained through step S2. Limi and power recovery margin △P recoveri If △P recoveri ≥0, it means that the fault receiving terminal converter station i can recover to the power level before the fault normally after the fault. The multi-terminal DC transmission system uses the original control mode of the fault receiving terminal converter station i as the first control mode and the DC power P of the fault receiving terminal converter station i 0i As the upper limit of the first power reference value, the operation of the fault receiving converter station i is controlled. recoveri <0, it means that the DC power of the fault receiving end converter station i cannot be restored to the power level before the fault after the fault, and the DC power after the fault needs to be limited. After the fault occurs, the control mode of the fault receiving end converter station i is switched to the fixed DC power control mode as the first control mode, and the upper limit of the first power reference value of the fault receiving end converter station i is set to its maximum recoverable power P Limi Afterwards, the multi-terminal direct current transmission system controls the operation of the fault receiving-end converter station i according to the first control mode and the first power reference value upper limit of the fault receiving-end converter station i.

[0111] like Figure 3 As shown, in one embodiment of the present application, a sending-end control strategy is used to process the maximum recoverable power and power recovery margin of the faulty receiving-end converter station and the non-faulty receiving-end converter station, and the second power reference value upper limit and the second control mode of the sending-end converter station are obtained, including:

[0112] According to the power recovery margin of each non-fault receiving-end converter station, non-fault receiving-end converter stations satisfying the power recovery margin greater than zero are selected to obtain a converter station set;

[0113] The total power recovery margin is calculated based on the power recovery margins of all non-fault receiving converter stations in the converter station set; the limited power is calculated based on the DC power and maximum recoverable power of the fault receiving converter station;

[0114] Obtaining the sending-end DC power of the sending-end converter station before the fault; based on the total power recovery margin being no less than the limited power, the sending-end DC power of the sending-end converter station is used as the upper limit of the second power reference value, and the second control mode of the sending-end converter station is a fixed DC power control mode;

[0115] The sending-end power reference value is calculated based on the sending-end DC power, the limited power and the total power recovery margin; since the total power recovery margin is less than the limited power, the sending-end power reference value of the sending-end converter station is used as the upper limit of the second power reference value, and the second control mode of the sending-end converter station is the fixed DC power control mode.

[0116] It should be noted that when the regulation capacity of the non-fault receiving converter station is sufficient to absorb the power fluctuation of the faulty receiving converter station, the power of the sending converter station remains unchanged; if the regulation capacity of the non-fault receiving converter station cannot fully absorb the power fluctuation of the faulty converter station, the reference power of the sending converter station needs to be reduced, and the reduction value is the part that exceeds the regulation capacity of the receiving end. The content of the sending end control strategy includes: first, calculating the total power recovery margin of the non-fault receiving converter station △P recoverj >0, j is the jth non-fault receiving converter station with a power recovery margin greater than zero, m is the total number of non-fault receiving converter stations with a power recovery margin greater than zero in the converter station set, and the restricted power P of the fault receiving converter station i after the fault 0i -P Limi If P R ≥P 0i -P Limi , that is, the regulation capacity of the receiving-end converter station is sufficient to absorb the limited power of the faulty receiving-end converter station i, then the second control mode of the sending-end converter station is set to the fixed DC power control mode, and the upper limit of the second power reference value of the sending-end converter station is maintained at the sending-end DC power P before the fault. S0 If P R <P 0i -P Limi , that is, the regulating capacity of the receiving-end converter station is insufficient to absorb the restricted power of the fault receiving-end converter station i. At this time, the sending-end power needs to be lowered. The second control mode of the sending-end converter station is set to the fixed DC power control mode, and the upper limit of the second power reference value of the sending-end converter station is lowered to the sending-end power reference value P S0 -P 0i -P Limi -P R In this embodiment, the fault recovery control method of the multi-terminal DC transmission system reduces the power of the converter station after the fault through the sending-end control strategy, and the non-fault receiving-end converter station takes priority to bear the power, thereby ensuring that the transmission power of the sending-end converter station is not reduced.

[0117] Figure 4This is a flow chart of the control strategy for the non-fault receiving end in the fault recovery control method for the multi-terminal direct current transmission system described in an embodiment of the present application.

[0118] like Figure 4 As shown, in one embodiment of the present application, a non-fault receiving-end control strategy is used to process the power recovery margin and DC power of each non-fault receiving-end converter station, and the third power reference value upper limit and the third control mode corresponding to the non-fault receiving-end converter station are obtained, including:

[0119] If the power recovery margin of each non-fault receiving-end converter station is less than zero, the DC power of the corresponding non-fault receiving-end converter station before the fault is used as the upper limit of the third power reference value, and the third control mode of the corresponding non-fault receiving-end converter station is the fixed DC power control mode;

[0120] If the power recovery margin of each non-fault receiving-end converter station is not less than zero, the DC voltage change of the non-fault receiving-end converter station before and after the fault is obtained, and the recovery power reference value of the non-fault receiving-end converter station is calculated based on the DC power, power recovery margin and DC voltage change of the non-fault receiving-end converter station; the recovery power reference value of the non-fault receiving-end converter station is used as the third power reference value upper limit, and the third control mode of the non-fault receiving-end converter station is the DC power-DC voltage droop control mode.

[0121] It should be noted that if Figure 4 As shown in Figure 1, after a fault occurs, the non-fault receiving converter station absorbs the power reduction after the fault receiving converter station is restored according to its ability to bear power fluctuations. The non-fault receiving control strategy includes: if the power recovery margin △P of the non-fault receiving converter station j′ is recoverj′ <0, the power increase margin of the non-fault receiving converter station j′ is small. After the fault of the fault receiving converter station i, the third control mode of the non-fault receiving converter station j′ is set to the fixed DC power control mode. The upper limit of the third power reference value of the non-fault receiving converter station j′ is maintained at the DC power P before the fault. 0j′ If the power recovery margin △P of the receiving converter station j′ is not recoverj′ ≥0, the third control mode of the non-fault receiving converter station j′ is set to the DC power-DC voltage droop control mode, and the droop slope of the DC power-DC voltage droop control mode is proportional to the power recovery margin △P of the corresponding non-fault receiving converter station j′. recoverj′ The third power reference value upper limit of the non-fault receiving converter station j′ is the restoration power reference value P refj′ , the calculation formula for the restored power reference value is P refj' =P 0j' +M*ΔP recoverj' ΔU d , where △U dis the DC voltage change, and M is a fixed coefficient. The formula for calculating the restoration power reference value indicates that the greater the power restoration margin of a non-fault receiving-end converter station, the more unbalanced power it will absorb. In this embodiment, compared to traditional master-slave control and droop control for multi-terminal DC transmission systems, this fault recovery control method for a multi-terminal DC transmission system utilizes a fault receiving-end control strategy, a sending-end control strategy, and a non-fault receiving-end control strategy to distribute multi-terminal DC power. This fully considers the power recovery potential of the receiving-end converter station, resulting in more reasonable power allocation.

[0122] In an embodiment of the present application, the fault recovery control method of the multi-terminal DC transmission system realizes the reasonable distribution of unbalanced power between the non-fault receiving-end converter station and the sending-end converter station through the sending-end control strategy and the non-fault receiving-end control strategy. The excess power in the multi-terminal DC transmission system is preferentially shared by the receiving-end converter station according to the power recovery capability, and the insufficient part is then balanced by reducing the power injected by the sending-end converter station.

[0123] It should be noted that the fault recovery control method for this multi-terminal DC transmission system uses a sending-end control strategy and a non-fault receiving-end control strategy to achieve a reasonable distribution of unbalanced power between the non-fault receiving-end converter stations and the sending-end converter stations. A four-terminal DC transmission system consisting of one sending-end converter station and three receiving-end converter stations is used as an example. First, if an AC fault occurs at a station, according to the fault receiving-end control strategy, if the faulted receiving-end converter station cannot recover to its pre-fault power level, the power of this faulted receiving-end converter station will be reduced, resulting in restricted power. For example, if faulted receiving-end converter station No. 1 had a pre-fault power of 2000MW, it could only recover to 1800MW after the fault, resulting in a restricted power of 200MW. This restricted power is preferentially shared by the other non-fault receiving-end converter stations, proportionally distributed according to the size of the power recovery margin (i.e., the non-fault receiving-end control strategy). In a four-terminal HVDC transmission system, the fault recovery margins of the non-fault receiving converter stations 2 and 3 are in a 4:1 ratio. Therefore, the 200MW of restricted power is distributed to the receiving converter stations 2 and 3 at a ratio of 160MW and 40MW, respectively. If the total power recovery margin of the non-fault receiving converter stations is less than the restricted power, meaning that the other non-fault receiving converter stations are insufficient to absorb the entire restricted power, the upper limit of the second power reference value of the sending converter stations must be lowered. If the total power recovery margin of the non-fault receiving converter stations 2 and 3 is only 150MW, then after the non-fault receiving converter stations 2 and 3 absorb 150MW, there will still be 50MW that cannot be shared by the non-fault receiving converter stations. Therefore, the upper limit of the second power reference value of the sending converter stations must be lowered by 50MW, so that the non-fault receiving converter stations can fully absorb the restricted power at the receiving end, ensuring power balance in the four-terminal HVDC transmission system after a fault occurs.

[0124] Example 2:

[0125] Figure 5 This is a schematic diagram of the framework of the fault recovery control device of the multi-terminal direct current transmission system according to the embodiment of the present application.

[0126] like Figure 5 As shown, the embodiment of the present application provides a fault recovery control device for a multi-terminal direct current transmission system, including a data acquisition module 10, a calculation module 20, a recovery data acquisition module 30 and a fault recovery execution module 40;

[0127] The data acquisition module 10 is used to obtain the DC power before the fault and the recovery information after the fault of each receiving-end converter station in the multi-terminal DC transmission system, and to set reference power data, which includes the initial reference power upper limit value and the reference power step size;

[0128] A calculation module 20 is configured to calculate, based on the restoration information and reference power data of each receiving-end converter station, the maximum restorable power and power restoration margin of the corresponding receiving-end converter station using a fault restoration simulation rule;

[0129] The recovery data acquisition module 30 is configured to divide the converter stations of the multi-terminal direct current transmission system into a faulty receiving-end converter station, a sending-end converter station, and a plurality of non-faulty receiving-end converter stations after a fault occurs in the converter station; adopt a faulty receiving-end control strategy to process the DC power, maximum recoverable power, and power recovery margin of the faulty receiving-end converter station to obtain a first power reference value upper limit and a first control mode for the faulty receiving-end converter station; adopt a sending-end control strategy to process the maximum recoverable power and power recovery margin of the faulty receiving-end converter station and the non-faulty receiving-end converter stations to obtain a second power reference value upper limit and a second control mode for the sending-end converter station; and adopt a non-faulty receiving-end control strategy to process the power recovery margin and DC power of each non-faulty receiving-end converter station to obtain a third power reference value upper limit and a third control mode for the corresponding non-faulty receiving-end converter station.

[0130] The fault recovery execution module 40 is used to control the operation of the faulty receiving-end converter station according to the first power reference value upper limit and the first control mode; control the operation of the sending-end converter station according to the second power reference value upper limit and the second control mode; and control the operation of the corresponding non-faulty receiving-end converter station according to the third power reference value upper limit and the third control mode.

[0131] In the embodiment of the present application, the content of the fault recovery simulation rule includes:

[0132] If the recovery information of each receiving converter station indicates that the DC power of the receiving converter station cannot be normally restored after the fault, the reference power upper limit value of the receiving converter station is updated in a decreasing manner according to the initial reference power upper limit value and the reference power step size to obtain a first reference power upper limit adjustment value; and a short circuit fault simulation is performed on the receiving converter station according to the first reference power upper limit adjustment value to obtain a simulation result.

[0133] According to a simulation result indicating that the DC power of the receiving-end converter station cannot be normally restored, the first reference power upper limit adjustment value is used as a new initial reference power upper limit value, the reference power upper limit value of the receiving-end converter station is updated in a decreasing manner according to the first reference power upper limit adjustment value and the reference power step size to obtain a first reference power upper limit update value, and a short-circuit fault simulation is performed on the receiving-end converter station according to the first reference power upper limit update value until a simulation result indicating that the DC power of the receiving-end converter station is normally restored is obtained;

[0134] If the DC power of the receiving-end converter station is restored normally according to the simulation result, the first reference power upper limit adjustment value or the first reference power upper limit update value corresponding to the normal restoration of the DC power of the receiving-end converter station is used as the maximum restorable power of the receiving-end converter station;

[0135] The power recovery margin of the corresponding receiving converter station is obtained based on the maximum recoverable power and DC power of each receiving converter station;

[0136] or

[0137] If the recovery information of each receiving converter station indicates that the DC power of the receiving converter station has been restored normally after the fault, the reference power upper limit value of the receiving converter station is incrementally updated according to the initial reference power upper limit value and the reference power step size to obtain a second reference power upper limit adjustment value; and a short circuit fault simulation is performed on the receiving converter station according to the second reference power upper limit adjustment value to obtain a simulation result.

[0138] If the simulation result shows that the DC power of the receiving-end converter station has been restored normally, the second reference power upper limit adjustment value is used as a new initial reference power upper limit value, and the reference power upper limit value of the receiving-end converter station is incrementally updated according to the second reference power upper limit adjustment value and the reference power step size to obtain a second reference power upper limit update value; a short-circuit fault simulation is performed on the receiving-end converter station according to the second reference power upper limit update value until a simulation result shows that the DC power of the receiving-end converter station cannot be restored normally;

[0139] According to the simulation result, the DC power of the receiving-end converter station cannot be restored normally, the initial reference power upper limit value or the second reference power upper limit update value of the last DC power normal recovery simulation corresponding to the DC power of the receiving-end converter station cannot be restored normally is used as the maximum recoverable power of the receiving-end converter station;

[0140] The power recovery margin of the corresponding receiving-end converter station is obtained based on the maximum recoverable power and DC power of each receiving-end converter station.

[0141] In the embodiment of the present application, the fault receiving end control strategy includes:

[0142] Obtain the control mode of the fault receiving converter station before the fault;

[0143] If the power recovery margin of the fault receiving-end converter station is not less than zero, the DC power of the fault receiving-end converter station before the fault is used as the upper limit of the first power reference value, and the control mode of the fault receiving-end converter station before the fault is used as the first control mode;

[0144] If the power recovery margin of the fault receiving-end converter station is less than zero, the maximum recoverable power of the fault receiving-end converter station is used as the upper limit of the first power reference value, and the first control mode of the fault receiving-end converter station is the fixed DC power control mode;

[0145] The contents of the sending-end control strategy include:

[0146] According to the power recovery margin of each non-fault receiving-end converter station, non-fault receiving-end converter stations satisfying the power recovery margin greater than zero are selected to obtain a converter station set;

[0147] The total power recovery margin is calculated based on the power recovery margins of all non-fault receiving converter stations in the converter station set; the limited power is calculated based on the DC power and maximum recoverable power of the fault receiving converter station;

[0148] Obtaining the sending-end DC power of the sending-end converter station before the fault; based on the total power recovery margin being no less than the limited power, the sending-end DC power of the sending-end converter station is used as the upper limit of the second power reference value, and the second control mode of the sending-end converter station is a fixed DC power control mode;

[0149] A sending-end power reference value is calculated based on the sending-end DC power, the limited power, and the total power recovery margin; since the total power recovery margin is less than the limited power, the sending-end power reference value of the sending-end converter station is used as the upper limit of the second power reference value, and the second control mode of the sending-end converter station is the fixed DC power control mode;

[0150] The control strategy for the non-faulty receiving end includes:

[0151] If the power recovery margin of each non-fault receiving-end converter station is less than zero, the DC power of the corresponding non-fault receiving-end converter station before the fault is used as the upper limit of the third power reference value, and the third control mode of the corresponding non-fault receiving-end converter station is the fixed DC power control mode;

[0152] If the power recovery margin of each non-fault receiving-end converter station is not less than zero, the DC voltage change of the non-fault receiving-end converter station before and after the fault is obtained, and the recovery power reference value of the non-fault receiving-end converter station is calculated based on the DC power, power recovery margin and DC voltage change of the non-fault receiving-end converter station; the recovery power reference value of the non-fault receiving-end converter station is used as the third power reference value upper limit, and the third control mode of the non-fault receiving-end converter station is the DC power-DC voltage droop control mode.

[0153] It should be noted that the contents of the modules in the apparatus of Example 2 correspond to the steps of the method of Example 1. The contents of the fault recovery control method of the multi-terminal DC transmission system have been described in Example 1, and the steps of the fault recovery control method of the multi-terminal DC transmission system will not be described in detail in this embodiment.

[0154] Example 3:

[0155] Figure 6 This is a schematic diagram of the terminal device described in an embodiment of the present application.

[0156] like Figure 6 As shown, an embodiment of the present application provides a terminal device, including a processor and a memory;

[0157] A memory, configured to store program codes and transmit the program codes to a processor;

[0158] The processor is configured to execute the above-mentioned fault recovery control method for the multi-terminal direct current transmission system according to the instructions in the program code.

[0159] It should be noted that the processor is configured to execute the steps in the embodiment of the fault recovery control method for a multi-terminal direct current transmission system according to the instructions in the program code. Alternatively, the processor implements the functions of the modules / units in the above-mentioned system / device embodiments when executing the computer program.

[0160] For example, a computer program may be divided into one or more modules / units, one or more of which are stored in a memory and executed by a processor to complete the present application. One or more modules / units may be a series of computer program instruction segments capable of performing specific functions, and the instruction segments are used to describe the execution process of the computer program in a terminal device.

[0161] Terminal devices can be computing devices such as desktop computers, laptops, PDAs, and cloud servers. Terminal devices may include, but are not limited to, processors and memory. Those skilled in the art will appreciate that this does not constitute a limitation on terminal devices and may include more or fewer components than shown, or a combination of certain components, or different components. For example, terminal devices may also include input / output devices, network access devices, buses, and the like.

[0162] The processor may be a central processing unit (CPU), other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (dSIC), field-programmable gate arrays (FPGAs), other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor, etc.

[0163] The memory can be an internal storage unit of a terminal device, such as a hard drive or memory of the terminal device. The memory can also be an external storage device of the terminal device, such as a plug-in hard drive equipped with the terminal device, a smart memory card (SMC), a secure digital (SD) card, a flash memory card, etc. Furthermore, the memory can include both the internal storage unit of the terminal device and an external storage device. The memory is used to store computer programs and other programs and data required by the terminal device. The memory can also be used to temporarily store data that has been output or is about to be output.

[0164] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0165] In the several embodiments provided in this application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are merely schematic. For example, the division of the units is merely a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or units, which can be electrical, mechanical or other forms.

[0166] The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of these units may be selected to achieve the purpose of this embodiment according to actual needs.

[0167] In addition, the functional units in the various embodiments of the present application may be integrated into a single processing unit, or each unit may exist physically separately, or two or more units may be integrated into a single unit. The aforementioned integrated units may be implemented in the form of hardware or software functional units.

[0168] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application is essentially or the part that contributes to the prior art or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a number of instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: various media that can store program codes, such as a U disk, a mobile hard disk, a read-only memory (ROM), a random access memory (RdM), a magnetic disk or an optical disk.

[0169] As described above, the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A fault recovery control method for a multi-terminal direct current transmission system, characterized in that: The following steps are involved: Obtaining pre-fault DC power and post-fault recovery information of each receiving-end converter station in a multi-terminal DC transmission system, and setting reference power data, the reference power data including an initial reference power upper limit and a reference power step; Calculating, using a fault recovery simulation rule according to the recovery information of the receiving-end converter station and the reference power data, a maximum recoverable power and a power recovery margin corresponding to the receiving-end converter station; After a fault occurs in a converter station, the converter stations of the multi-terminal direct current transmission system are divided into a fault receiving-end converter station, a sending-end converter station, and a plurality of non-fault receiving-end converter stations; a fault receiving-end control strategy is adopted to perform processing according to the DC power, the maximum recoverable power, and the power recovery margin of the fault receiving-end converter station, to obtain a first power reference value upper limit and a first control mode of the fault receiving-end converter station; a sending-end control strategy is adopted to perform processing according to the maximum recoverable power and the power recovery margin of the fault receiving-end converter station and the non-fault receiving-end converter station, to obtain a second power reference value upper limit and a second control mode of the sending-end converter station; a non-fault receiving-end control strategy is adopted to perform processing according to the power recovery margin and the DC power of each non-fault receiving-end converter station, to obtain a third power reference value upper limit and a third control mode corresponding to the non-fault receiving-end converter station; controlling the operation of the faulty receiving-end converter station according to the first power reference value upper limit and the first control mode; controlling the operation of the sending-end converter station according to the second power reference value upper limit and the second control mode; and controlling the operation of the corresponding non-faulty receiving-end converter station according to the third power reference value upper limit and the third control mode; The sending-end control strategy is used to process the maximum restorable power and the power restoration margin of the faulty receiving-end converter station and the non-faulty receiving-end converter station to obtain a second power reference value upper limit and a second control mode of the sending-end converter station, including: According to the power recovery margins of the non-fault receiving-end converter stations, the non-fault receiving-end converter stations satisfying the power recovery margin being greater than zero are screened out to obtain a converter station set; Calculating the total power recovery margin based on the power recovery margins of all the non-fault receiving-end converter stations in the converter station set; and calculating the limited power based on the DC power and the maximum recoverable power of the fault receiving-end converter station; Obtaining the sending-end DC power of the sending-end converter station before a fault occurs; based on the total power recovery margin being not less than the limited power, using the sending-end DC power of the sending-end converter station as the upper limit of the second power reference value, and setting the second control mode of the sending-end converter station to a fixed DC power control mode; The sending-end power reference value is calculated based on the sending-end DC power, the limited power and the total power recovery margin; based on the total power recovery margin being less than the limited power, the sending-end power reference value of the sending-end converter station is used as the upper limit of the second power reference value, and the second control mode of the sending-end converter station is a fixed DC power control mode.

2. The fault recovery control method for a multi-terminal direct current transmission system according to claim 1, characterized in that: The content of the fault recovery simulation rule includes: If the recovery information of the receiving converter station indicates that the DC power of the receiving converter station cannot be normally restored after the fault, updating the reference power upper limit value of the receiving converter station in a decreasing manner according to the initial reference power upper limit value and the reference power step size to obtain a first reference power upper limit adjustment value; and performing a short circuit fault simulation on the receiving converter station according to the first reference power upper limit adjustment value to obtain a simulation result; If the simulation result shows that the DC power of the receiving converter station cannot be normally restored, the first reference power upper limit adjustment value is used as the new initial reference power upper limit value, the reference power upper limit value of the receiving converter station is updated in a decreasing manner according to the first reference power upper limit adjustment value and the reference power step size to obtain a first reference power upper limit update value, and a short-circuit fault simulation is performed on the receiving converter station according to the first reference power upper limit update value until the simulation result shows that the DC power of the receiving converter station is normally restored; If the DC power of the receiving-end converter station is restored normally according to the simulation result, the first reference power upper limit adjustment value or the first reference power upper limit update value corresponding to the normal restoration of the DC power of the receiving-end converter station is used as the maximum restorable power of the receiving-end converter station; The power recovery margin corresponding to the receiving-end converter station is obtained according to the maximum recoverable power of each receiving-end converter station and the DC power.

3. The fault recovery control method for a multi-terminal direct current transmission system according to claim 1, characterized in that: The content of the fault recovery simulation rule includes: If the recovery information of the receiving converter station indicates that the DC power of the receiving converter station has recovered normally after the fault, incrementally updating the reference power upper limit value of the receiving converter station according to the initial reference power upper limit value and the reference power step size to obtain a second reference power upper limit adjustment value; performing a short-circuit fault simulation on the receiving converter station according to the second reference power upper limit adjustment value to obtain a simulation result; If the simulation result shows that the DC power of the receiving converter station has been restored normally, the second reference power upper limit adjustment value is used as the new initial reference power upper limit value, and the reference power upper limit value of the receiving converter station is incrementally updated according to the second reference power upper limit adjustment value and the reference power step size to obtain a second reference power upper limit update value; and a short circuit fault simulation is performed on the receiving converter station according to the second reference power upper limit update value until the simulation result shows that the DC power of the receiving converter station cannot be restored normally. According to the simulation result, the DC power of the receiving-end converter station cannot be restored normally, using the initial reference power upper limit value or the second reference power upper limit update value of the last DC power normal recovery simulation corresponding to the DC power of the receiving-end converter station being unable to be restored normally as the maximum restorable power of the receiving-end converter station; The power recovery margin corresponding to the receiving-end converter station is obtained according to the maximum recoverable power of each receiving-end converter station and the DC power.

4. The fault recovery control method for a multi-terminal direct current transmission system according to claim 1, characterized in that: The first power reference value upper limit and the first control mode of the fault receiving-end converter station are obtained by adopting a fault receiving-end control strategy according to the DC power, the maximum restorable power, and the power restoration margin of the fault receiving-end converter station. Obtaining a control mode of the fault receiving-end converter station before the fault; If the power recovery margin of the fault receiving-end converter station is not less than zero, the DC power of the fault receiving-end converter station before the fault is used as the first power reference value upper limit, and the control mode of the fault receiving-end converter station before the fault is used as the first control mode; If the power recovery margin of the fault receiving converter station is less than zero, the maximum recoverable power of the fault receiving converter station is used as the upper limit of the first power reference value, and the first control mode of the fault receiving converter station is a fixed DC power control mode.

5. The fault recovery control method for a multi-terminal direct current transmission system according to claim 1, characterized in that: Processing the power recovery margin and the DC power of each non-fault receiving-end converter station using a non-fault receiving-end control strategy to obtain a third power reference value upper limit and a third control mode corresponding to the non-fault receiving-end converter station includes: If the power recovery margin of each of the non-fault receiving-end converter stations is less than zero, the DC power of the corresponding non-fault receiving-end converter station before the fault is used as the upper limit of the third power reference value, and the third control mode corresponding to the non-fault receiving-end converter station is a fixed DC power control mode; If the power recovery margin of each non-fault receiving-end converter station is not less than zero, the DC voltage change of the non-fault receiving-end converter station before and after the fault is obtained, and the recovery power reference value of the non-fault receiving-end converter station is calculated based on the DC power, the power recovery margin and the DC voltage change of the non-fault receiving-end converter station; the recovery power reference value of the non-fault receiving-end converter station is used as the upper limit of the third power reference value, and the third control mode of the non-fault receiving-end converter station is the DC power-DC voltage droop control mode.

6. A fault recovery control device for a multi-terminal direct current transmission system, characterized in that: It includes a data acquisition module, a calculation module, a recovery data acquisition module and a fault recovery execution module; The data acquisition module is used to obtain the DC power before the fault and the recovery information after the fault of each receiving-end converter station in the multi-terminal DC transmission system, and set reference power data, wherein the reference power data includes an initial reference power upper limit value and a reference power step size; The calculation module is configured to calculate, based on the recovery information of the receiving-end converter station and the reference power data, using a fault recovery simulation rule to obtain a maximum recoverable power and a power recovery margin corresponding to the receiving-end converter station; The recovery data acquisition module is configured to divide the converter stations of the multi-terminal direct current transmission system into a faulty receiving-end converter station, a sending-end converter station, and a plurality of non-faulty receiving-end converter stations according to a fault at the converter station; adopt a faulty receiving-end control strategy to perform processing based on the DC power, the maximum recoverable power, and the power recovery margin of the faulty receiving-end converter station to obtain a first power reference value upper limit and a first control mode of the faulty receiving-end converter station; adopt a sending-end control strategy to perform processing based on the maximum recoverable power and the power recovery margin of the faulty receiving-end converter station and the non-faulty receiving-end converter station to obtain a second power reference value upper limit and a second control mode of the sending-end converter station; adopt a non-faulty receiving-end control strategy to perform processing based on the power recovery margin and the DC power of each non-faulty receiving-end converter station to obtain a third power reference value upper limit and a third control mode corresponding to the non-faulty receiving-end converter station; The fault recovery execution module is configured to control the operation of the faulty receiving-end converter station according to the first power reference value upper limit and the first control mode; control the operation of the sending-end converter station according to the second power reference value upper limit and the second control mode; and control the operation of the corresponding non-faulty receiving-end converter station according to the third power reference value upper limit and the third control mode; The content of the sending end control strategy includes: According to the power recovery margins of the non-fault receiving-end converter stations, the non-fault receiving-end converter stations satisfying the power recovery margin being greater than zero are screened out to obtain a converter station set; Calculating the total power recovery margin based on the power recovery margins of all the non-fault receiving-end converter stations in the converter station set; and calculating the limited power based on the DC power and the maximum recoverable power of the fault receiving-end converter station; Obtaining the sending-end DC power of the sending-end converter station before a fault occurs; based on the total power recovery margin being not less than the limited power, using the sending-end DC power of the sending-end converter station as the upper limit of the second power reference value, and setting the second control mode of the sending-end converter station to a fixed DC power control mode; The sending-end power reference value is calculated based on the sending-end DC power, the limited power and the total power recovery margin; based on the total power recovery margin being less than the limited power, the sending-end power reference value of the sending-end converter station is used as the upper limit of the second power reference value, and the second control mode of the sending-end converter station is a fixed DC power control mode.

7. The fault recovery control device for a multi-terminal direct current transmission system according to claim 6, characterized in that: The content of the fault recovery simulation rule includes: If the recovery information of the receiving converter station indicates that the DC power of the receiving converter station cannot be normally restored after the fault, updating the reference power upper limit value of the receiving converter station in a decreasing manner according to the initial reference power upper limit value and the reference power step size to obtain a first reference power upper limit adjustment value; and performing a short circuit fault simulation on the receiving converter station according to the first reference power upper limit adjustment value to obtain a simulation result; If the simulation result shows that the DC power of the receiving converter station cannot be normally restored, the first reference power upper limit adjustment value is used as the new initial reference power upper limit value, the reference power upper limit value of the receiving converter station is updated in a decreasing manner according to the first reference power upper limit adjustment value and the reference power step size to obtain a first reference power upper limit update value, and a short-circuit fault simulation is performed on the receiving converter station according to the first reference power upper limit update value until the simulation result shows that the DC power of the receiving converter station is normally restored; If the DC power of the receiving-end converter station is restored normally according to the simulation result, the first reference power upper limit adjustment value or the first reference power upper limit update value corresponding to the normal restoration of the DC power of the receiving-end converter station is used as the maximum restorable power of the receiving-end converter station; Calculating, based on the maximum recoverable power of each receiving-end converter station and the DC power, to obtain a power recovery margin corresponding to the receiving-end converter station; or If the recovery information of the receiving converter station indicates that the DC power of the receiving converter station has recovered normally after the fault, incrementally updating the reference power upper limit value of the receiving converter station according to the initial reference power upper limit value and the reference power step size to obtain a second reference power upper limit adjustment value; performing a short-circuit fault simulation on the receiving converter station according to the second reference power upper limit adjustment value to obtain a simulation result; If the simulation result shows that the DC power of the receiving converter station has been restored normally, the second reference power upper limit adjustment value is used as the new initial reference power upper limit value, and the reference power upper limit value of the receiving converter station is incrementally updated according to the second reference power upper limit adjustment value and the reference power step size to obtain a second reference power upper limit update value; and a short circuit fault simulation is performed on the receiving converter station according to the second reference power upper limit update value until the simulation result shows that the DC power of the receiving converter station cannot be restored normally. According to the simulation result, the DC power of the receiving-end converter station cannot be restored normally, using the initial reference power upper limit value or the second reference power upper limit update value of the last DC power normal recovery simulation corresponding to the DC power of the receiving-end converter station being unable to be restored normally as the maximum restorable power of the receiving-end converter station; The power recovery margin corresponding to the receiving-end converter station is obtained according to the maximum recoverable power of each receiving-end converter station and the DC power.

8. The fault recovery control device for a multi-terminal direct current transmission system according to claim 6, characterized in that: The fault receiving end control strategy includes: Obtaining a control mode of the fault receiving-end converter station before the fault; If the power recovery margin of the fault receiving-end converter station is not less than zero, the DC power of the fault receiving-end converter station before the fault is used as the first power reference value upper limit, and the control mode of the fault receiving-end converter station before the fault is used as the first control mode; If the power recovery margin of the fault receiving-end converter station is less than zero, the maximum recoverable power of the fault receiving-end converter station is used as the upper limit of the first power reference value, and the first control mode of the fault receiving-end converter station is a fixed DC power control mode; The content of the non-fault receiving end control strategy includes: If the power recovery margin of each of the non-fault receiving-end converter stations is less than zero, the DC power of the corresponding non-fault receiving-end converter station before the fault is used as the upper limit of the third power reference value, and the third control mode corresponding to the non-fault receiving-end converter station is a fixed DC power control mode; If the power recovery margin of each non-fault receiving-end converter station is not less than zero, the DC voltage change of the non-fault receiving-end converter station before and after the fault is obtained, and the recovery power reference value of the non-fault receiving-end converter station is calculated based on the DC power, the power recovery margin and the DC voltage change of the non-fault receiving-end converter station; the recovery power reference value of the non-fault receiving-end converter station is used as the upper limit of the third power reference value, and the third control mode of the non-fault receiving-end converter station is the DC power-DC voltage droop control mode.

9. A terminal device, characterized in that: including a processor and a memory; The memory is used to store program code and transmit the program code to the processor; The processor is configured to execute the fault recovery control method for a multi-terminal direct current transmission system according to any one of claims 1 to 5 according to instructions in the program code.

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