Methods, devices, and equipment for screening the internal grid topology of DC offshore wind farms

Abstract

This application relates to a method, apparatus, and equipment for screening the internal grid topology of a DC-type offshore wind farm. The method includes: acquiring the topology type and grid parameters of the offshore DC wind farm; calculating internal grid loss indicators, reliability indicators, and construction cost indicators based on the grid parameters; acquiring weight data, market electricity price, and estimated operating life; calculating the economic cost based on the weight data, market electricity price, estimated operating life, internal grid loss indicators, reliability indicators, and construction cost indicators; and selecting the topology type with the lowest economic cost value from all topology types as the internal grid topology of the offshore DC wind farm. This method calculates the internal grid loss indicators, reliability indicators, and construction cost indicators using grid parameters and topology type, then calculates the economic cost for each topology type, and selects the topology type with the lowest economic cost value from all topology types as the internal grid topology of the offshore DC wind farm.

Description

Technical Field

[0001] This application relates to the field of offshore wind farm technology, and in particular to a method, apparatus and equipment for screening the internal grid topology of a DC offshore wind farm. Background Technology

[0002] With the increase in the capacity and distance from shore of offshore wind farm systems, the transmission voltage of offshore wind farm systems has reached the level of high-voltage direct current transmission. The topology of the internal network of offshore wind farms has a particularly important impact on the economy, reliability, and power generation efficiency of offshore wind farm systems.

[0003] Once the capacity, number of turbines, transmission voltage, and other parameters of an offshore wind farm system are determined, there are usually different options for its internal network topology. Choosing a suitable internal network topology for an offshore wind farm plays a positive role in improving the operational performance and economic indicators of the offshore wind farm system. Summary of the Invention

[0004] This application provides a method, apparatus, and equipment for screening the internal network topology of a DC offshore wind farm, which solves the technical problem that existing evaluation methods do not select the optimal internal network topology for offshore DC wind farms.

[0005] To achieve the above objectives, this application provides the following technical solution:

[0006] On the one hand, a method for screening the internal grid topology of a DC offshore wind farm is provided, including the following steps:

[0007] Obtain the topology type of the offshore DC wind farm and the corresponding grid parameters for each topology type;

[0008] Based on the power grid parameters, the internal grid loss index and reliability index of the offshore DC wind farm are calculated; based on the topology type and the corresponding power grid parameters, the construction cost index corresponding to the topology type is calculated.

[0009] Obtain weighted data, market electricity sales price and estimated operating life of offshore DC wind farms, and calculate the economic cost corresponding to each topology type based on the weighted data, market electricity sales price, estimated operating life, internal grid loss index, reliability index and construction cost index of each topology type.

[0010] The topology with the lowest economic cost value among all the topology types is selected as the internal network topology of the offshore DC wind farm;

[0011] The grid parameters include the annual average operating time, the first annual average effective value of the current injected into the unit cable by each wind turbine, the cable length, the unit resistance value of the cable, the total cable length, the cable capacity, the cable cost coefficient, the number of cables, the second annual average effective value of the current of the DC circuit breaker, the resistance value of the DC circuit breaker, the cost of the DC circuit breaker, the number of DC circuit breakers, the annual average effective value of the power of the DC converter station, the efficiency of the DC converter station, the additional investment of the DC converter station, the number of DC converter stations, the number of electronic components, the annual average number of failures, the average repair time of a single failure, and the average power loss per failure; the topology types include parallel topology, series topology, and matrix topology.

[0012] Preferably, the internal grid loss index of the offshore DC wind farm is calculated based on the grid parameters, including:

[0013] Each DC cable is segmented to obtain a unit cable; the annual average power loss of the corresponding DC cable is calculated based on the first annual average current effective value, the unit resistance value, and the cable length of the unit cable.

[0014] The first power loss of the corresponding DC circuit breaker is calculated based on the second annual average current effective value of each DC circuit breaker and the resistance value of the DC circuit breaker.

[0015] The second power loss of the corresponding DC converter station is calculated based on the annual average power effective value and the efficiency of each DC converter station.

[0016] The internal grid loss index of the offshore DC wind farm is calculated based on the average annual operating time, the number of cables, the number of DC circuit breakers, the number of DC converter stations, the average annual power loss, the first power loss, and the second power loss.

[0017] Preferably, the method for selecting the internal network topology of the DC offshore wind farm includes: calculating the annual average power loss of the corresponding DC cable using a cable loss formula based on the first annual average effective current value, the unit resistance value, and the cable length per unit cable; calculating the first power loss of the corresponding DC circuit breaker using a circuit breaker loss formula based on the second annual average effective current value of each DC circuit breaker and the resistance value of the DC circuit breaker; and calculating the second power loss of the corresponding DC converter station using a converter station loss formula based on the annual average effective power value and the efficiency of each DC converter station; the cable loss formula is:

[0018]

[0019] The circuit breaker loss formula is as follows: ;

[0020] The converter station loss formula is as follows: ;

[0021] In the formula, P Cablek Let i be the average annual power loss of the k-th DC cable. m R is the effective value of the average current of the first year for the m-th segment of the unit cable. Cablen Let L be the unit resistance value of the nth segment of the cable. n Let i be the length of the nth unit cable segment, where n, e, and v are all natural numbers greater than 1. Brke R is the effective value of the average current in the second year for the e-th DC circuit breaker. Brke Let p be the resistance value of the e-th DC circuit breaker. v Let v be the annual average effective power value of the v-th DC converter. Let P be the efficiency of the v-th DC converter. Conv For the second power loss of the vth DC converter station, P Brke This represents the first power loss of the e-th DC circuit breaker.

[0022] Preferably, the reliability indicators of the offshore DC wind farm, calculated based on the grid parameters, include:

[0023] The energy loss of the DC cable is calculated using the energy loss formula based on the number of electronic components in the DC cable, the annual average number of faults corresponding to the DC cable, the average repair time of a single fault, and the average power loss per fault.

[0024] The energy loss of the DC circuit breaker is calculated using the energy loss formula based on the number of electronic components of the DC circuit breaker, the annual average number of faults corresponding to the DC circuit breaker, the average repair time of a single fault, and the average power loss per fault.

[0025] The energy loss of the DC converter is calculated using the energy loss formula based on the number of electronic components in the DC converter, the annual average number of faults corresponding to the DC converter, the average repair time of a single fault, and the average power loss per fault.

[0026] The expected energy loss of the offshore DC wind farm is calculated based on the energy loss of the DC cable, the energy loss of the DC circuit breaker, and the energy loss of the DC converter, and the expected energy loss is used as a reliability indicator.

[0027] The energy loss formula is as follows:

[0028]

[0029] In the formula, N iLet λ be the number of the i-th electronic component, which includes DC cables, DC circuit breakers, and DC converters. i h represents the average number of failures per year for the i-th electronic component. i Let be the mean time to repair a single fault of the i-th electronic component, λ be the average annual reliability of the electronic component, h be the average annual repair time to repair a single fault of the electronic component, and P be the mean time to repair a single fault of the electronic component. F Let W be the average power loss per fault in an offshore DC wind farm, and let W be the energy loss of electronic components.

[0030] Preferably, the construction cost index corresponding to the topology type is calculated based on the topology type and the corresponding power grid parameters, including:

[0031] The cost of the submarine DC cable is calculated using a cable cost formula based on the number of cables, the total length of the cables, the cable capacity, and the cable cost coefficient; and / or

[0032] If the topology is a series topology, the cost of the submarine DC cable will be used as a construction cost indicator.

[0033] If the topology is a parallel topology, the construction cost index is calculated based on the cost of the submarine DC cable and the additional investment in the DC converter station.

[0034] If the topology type is a matrix topology, the construction cost index is obtained based on the cost of the submarine DC cable, the additional investment in the DC converter station, and the cost of the DC circuit breaker.

[0035] The cable cost formula is as follows:

[0036]

[0037] In the formula, I nvcable Let S be the cost of the submarine DC cable, K be the cable cost coefficient, and S be the cost of the cable. i Let l be the total length of the i-th cable. i Let be the cable capacity of the i-th cable.

[0038] Preferably, the method for selecting the internal grid topology of the DC-type offshore wind farm includes: calculating the economic cost corresponding to each topology type using an economic cost formula based on the weighted data, the market electricity price, the estimated operating life, the internal grid loss index, the reliability index, and the construction cost index for each topology type; the economic cost formula is: In the formula, E sum For economic costs, These represent the weights of the internal network loss index, reliability index, and construction cost index, respectively, k. pN represents the market sales price of electricity from offshore DC wind farms. y For the estimated operational life of offshore DC wind farms, W ss Inv is an internal network loss indicator. sum W is a construction cost indicator. F，loss This is a reliability indicator.

[0039] On the other hand, a device for screening the internal grid topology of a DC offshore wind farm is provided, including a data acquisition module, an index calculation module, a cost calculation module and a topology screening module.

[0040] The data acquisition module is used to acquire the topology type of the offshore DC wind farm and the grid parameters corresponding to each topology type;

[0041] The index calculation module is used to calculate, based on the grid parameters, the internal grid loss index and reliability index of the offshore DC wind farm; and to calculate, based on the topology type and the corresponding grid parameters, the construction cost index corresponding to the topology type.

[0042] The cost calculation module is used to acquire weight data, the market electricity price and estimated operating life of the offshore DC wind farm, and calculate the economic cost corresponding to each topology type based on the weight data, the market electricity price, the estimated operating life, the internal network loss index, the reliability index, and the construction cost index of each topology type.

[0043] The topology filtering module is used to filter out the topology type with the lowest economic cost value from all the topology types as the internal network topology of the offshore DC wind farm.

[0044] The grid parameters include the annual average operating time, the first annual average effective value of the current injected into the unit cable by each wind turbine, the cable length, the unit resistance value of the cable, the total cable length, the cable capacity, the cable cost coefficient, the number of cables, the second annual average effective value of the current of the DC circuit breaker, the resistance value of the DC circuit breaker, the cost of the DC circuit breaker, the number of DC circuit breakers, the annual average effective value of the power of the DC converter station, the efficiency of the DC converter station, the additional investment of the DC converter station, the number of DC converter stations, the number of electronic components, the annual average number of failures, the average repair time of a single failure, and the average power loss per failure; the topology types include parallel topology, series topology, and matrix topology.

[0045] Preferably, the cost calculation module is further configured to calculate, using an economic cost formula, the weighted data, the market electricity price, the estimated operating life, the internal network loss index, the reliability index, and the construction cost index for each topology type, to obtain the economic cost corresponding to each topology type; the economic cost formula is: In the formula, E sum For economic costs, These are the weighted data for internal network loss indicators, reliability indicators, and construction cost indicators, respectively, k. p N represents the market sales price of electricity from offshore DC wind farms. y For the estimated operational life of offshore DC wind farms, W ss Inv is an internal network loss indicator. sum W is a construction cost indicator. F，loss This is a reliability indicator.

[0046] Preferably, the indicator calculation module includes a first indicator calculation submodule, a second indicator calculation submodule, and a third indicator calculation submodule;

[0047] The first index calculation submodule is used to segment each DC cable to obtain a unit cable; calculate the annual average power loss of the corresponding DC cable using the cable loss formula based on the first annual average current effective value, the unit resistance value, and the cable length of the unit cable; calculate the first power loss of the corresponding DC circuit breaker using the circuit breaker loss formula based on the second annual average current effective value and the resistance value of each DC circuit breaker; and calculate the second power loss of the corresponding DC converter station using the converter station loss formula based on the annual average power effective value and the efficiency of each DC converter station.

[0048] The second index calculation submodule is used to calculate the energy loss of electronic components based on the number of electronic components, the annual average number of failures corresponding to the electronic components, the average repair time of a single failure, and the average power loss per failure using an energy loss formula; and to calculate the expected energy loss of the offshore DC wind farm based on the energy loss of all electronic components, and to use the expected energy loss as a reliability index.

[0049] The third indicator calculation submodule is used to calculate the cost of the submarine DC cable using a cable cost formula based on the number of cables, the total length of the cables, the cable capacity, and the cable cost coefficient; and / or, if the topology type is a series topology, the cost of the submarine DC cable is used as the construction cost indicator; if the topology type is a parallel topology, the construction cost indicator is calculated based on the cost of the submarine DC cable and the additional investment in the DC converter station; if the topology type is a matrix topology, the construction cost indicator is calculated based on the cost of the submarine DC cable, the additional investment in the DC converter station, and the cost of the DC circuit breaker.

[0050] The cable loss formula is as follows:

[0051]

[0052] The circuit breaker loss formula is as follows: ;

[0053] The converter station loss formula is as follows: ;

[0054] The energy loss formula is as follows:

[0055]

[0056] The formula for the cost of the cable is:

[0057]

[0058] In the formula, I nvcable Let S be the cost of the submarine DC cable, K be the cable cost coefficient, and S be the cost of the cable. i Let l be the total length of the i-th cable. i P represents the cable capacity of the i-th cable; Cablek Let i be the average annual power loss of the k-th DC cable. m R is the effective value of the average current of the first year for the m-th segment of the unit cable. Cablen Let L be the unit resistance value of the nth segment of the cable. n Let i be the length of the nth unit cable segment, where n, e, and v are all natural numbers greater than 1. Brke R is the effective value of the average current in the second year for the e-th DC circuit breaker. Brke Let p be the resistance value of the e-th DC circuit breaker. v Let v be the annual average effective power value of the v-th DC converter. Let P be the efficiency of the v-th DC converter. Conv For the second power loss of the vth DC converter station, P Brke N represents the first power loss of the e-th DC circuit breaker; iLet λ be the number of the i-th electronic component, which includes DC cables, DC circuit breakers, and DC converters. i h represents the average number of failures per year for the i-th electronic component. i Let be the mean time to repair a single fault of the i-th electronic component, λ be the average annual reliability of the electronic component, h be the average annual repair time to repair a single fault of the electronic component, and P be the mean time to repair a single fault of the electronic component. F Let W be the average power loss per fault in an offshore DC wind farm, and let W be the energy loss of electronic components.

[0059] On the other hand, a terminal device is provided, including a processor and a memory;

[0060] The memory is used to store program code and transmit the program code to the processor;

[0061] The processor is used to execute the above-described method for filtering the internal network topology of a DC-type offshore wind farm according to the instructions in the program code.

[0062] The present invention relates to a method, apparatus, and equipment for screening the internal grid topology of a DC-type offshore wind farm. The method includes: acquiring the topology type of the offshore DC wind farm and the corresponding grid parameters for each topology type; calculating the internal grid loss index and reliability index of the offshore DC wind farm based on the grid parameters; calculating the construction cost index corresponding to the topology type based on the topology type and the corresponding grid parameters; acquiring weight data, the market electricity price per unit area, and the estimated operating life of the offshore DC wind farm; calculating the economic cost corresponding to each topology type based on the weight data, market electricity price per unit area, estimated operating life, internal grid loss index, reliability index, and construction cost index for each topology type; and selecting the topology type with the lowest economic cost value from all topology types as the internal grid topology of the offshore DC wind farm.

[0063] As can be seen from the above technical solutions, this application has the following advantages: The method for selecting the internal network topology of the DC offshore wind farm first calculates the internal network loss index, reliability index, and construction cost index of each topology type based on the obtained grid parameters and topology type, then calculates the economic cost of each topology type, and selects the topology type with the smallest economic cost value from all topology types as the internal network topology of the offshore DC wind farm, thereby achieving the selection of the optimal internal network topology of the offshore DC wind farm; it solves the technical problem that the existing evaluation method does not select the optimal internal network topology of the offshore DC wind farm. Attached Figure Description

[0064] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0065] Figure 1 This is a flowchart illustrating the steps of the method for screening the internal network topology of a DC-type offshore wind farm as described in an embodiment of this application.

[0066] Figure 2 This is a schematic diagram illustrating the segmentation of DC cables in the internal network topology screening method for DC-type offshore wind farms described in this application embodiment;

[0067] Figure 3 This is a schematic diagram of the frame of the internal network topology screening device for a DC-type offshore wind farm as described in the embodiments of this application;

[0068] Figure 4 This is a schematic diagram of the terminal device described in the embodiments of this application;

[0069] Figure 5 It is a parallel topology for the existing offshore DC wind farm internal network;

[0070] Figure 6 The existing series-parallel topology of the offshore DC wind farm internal network;

[0071] Figure 7 The existing offshore DC wind farm internal network uses a parallel-series topology.

[0072] Figure 8 This is a matrix topology for the internal network of existing offshore DC wind farms. Detailed Implementation

[0073] To make the inventive objectives, features, and advantages of this application more apparent and understandable, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0074] In the description of the embodiments of this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0075] In the embodiments of this application, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0076] In this embodiment, the internal grid topology of offshore DC wind farms using high-voltage direct current (HVDC) transmission includes parallel topology, series boost topology (hereinafter referred to as series topology), and matrix topology; wherein the series topology includes series-parallel topology and parallel-series topology. Each of these internal grid topologies for offshore DC wind farms has its own advantages and disadvantages. Specifically:

[0077] like Figure 5 As shown, the parallel topology is a simple DC internal network topology. In this topology, the wind turbines are connected in parallel to achieve power aggregation, and then the voltage level is raised to a level suitable for high-voltage DC transmission through a single-stage boost converter. This parallel topology requires the construction of a DC-DC converter equivalent to the entire wind farm capacity, which seriously affects the economic indicators of offshore wind farms and increases internal network losses.

[0078] like Figure 6 As shown, in the series-parallel topology, a group of wind turbines are first connected in series to form a cluster, achieving a voltage level suitable for high-voltage DC transmission. Then, several clusters of series-connected turbines are connected in parallel to achieve the wind farm's rated output power and transmit the power. This series-parallel topology eliminates the need for expensive and loss-prone offshore converter platforms. The series-parallel topology is clear, simple, and easy to control.

[0079] like Figure 7 As shown, the parallel-series topology first connects a group of wind turbines in parallel to form a unit with a certain power level, and then connects multiple units in series to achieve the required voltage level. This parallel-series topology effectively avoids the problem of the entire series cluster of wind turbines being disconnected from the grid due to a DC cable failure in a series-parallel structure.

[0080] like Figure 8 As shown, the matrix topology is based on the series-parallel topology, with the addition of additional DC cable lines and DC circuit breakers to form a crisscrossing matrix network structure. This matrix topology can effectively improve the utilization rate of wind energy, but at the cost of economic efficiency.

[0081] In this embodiment, the advantages and disadvantages of three indicators—internal network loss, construction cost, and reliability—of offshore DC wind farms under different internal network topologies are comprehensively compared. The most suitable internal network topology for the offshore DC wind farm can be determined from the four topologies mentioned above. The comparison of these three indicators requires parameters related to the loss, cost, and reliability of electrical equipment such as DC wind turbines, high-power DC circuit breakers, and high-power DC-DC converters. However, in current offshore DC wind farm projects, these electrical equipment are not operational on a large scale, making it impossible to directly obtain accurate comparison parameters.

[0082] To facilitate comparison of different internal network topologies for offshore DC wind farms, this application employs an incremental method. This method involves disregarding identical components in the internal network loss, economic efficiency, and reliability indicators of comparative models for offshore DC wind farms with different internal and external topologies. Instead, it focuses on comparing the differences in these indicators under different internal network topologies. The internal network of an offshore DC wind farm consists of two parts: DC wind turbine units and a collection network. The collection network includes DC cables, necessary DC circuit breakers, and DC converter stations. Since the indicators for DC wind turbine units are identical across various internal network topologies, they can be disregarded. By comparing the technical and economic indicators of existing components in the collection network, the superiority or inferiority of different internal network topologies for offshore DC wind farms can be determined.

[0083] This application provides a method, apparatus, and equipment for screening the internal network topology of a DC offshore wind farm, which solves the technical problem that existing evaluation methods do not select the optimal internal network topology of offshore DC wind farms.

[0084] Example 1:

[0085] Figure 1 This is a flowchart illustrating the steps of the method for screening the internal network topology of a DC-type offshore wind farm as described in an embodiment of this application.

[0086] like Figure 1 As shown in the figure, this application provides a method for screening the internal network topology of a DC offshore wind farm, including the following steps:

[0087] S1. Obtain the topology type of the offshore DC wind farm and the corresponding grid parameters for each topology type.

[0088] It should be noted that obtaining the grid parameters of the offshore DC wind farm in step S1 provides data for calculating the economic cost of each type of offshore DC wind farm internal grid topology; it also provides basic calculation data for calculating the three indicators of internal grid loss, construction cost, and reliability of the subsequent offshore DC wind farm internal grid aggregation topology.

[0089] In this embodiment, the power grid parameters include the annual average operating time, the first annual average effective value of the current injected into the unit cable by each wind turbine, the cable length, the unit resistance value of the cable, the total cable length, the cable capacity, the cable cost coefficient, the number of cables, the second annual average effective value of the current of the DC circuit breaker, the resistance value of the DC circuit breaker, the cost of the DC circuit breaker, the number of DC circuit breakers, the annual average effective value of the power of the DC converter station, the efficiency of the DC converter station, the additional investment of the DC converter station, the number of DC converter stations, the number of electronic components, the annual average number of failures, the average repair time of a single failure, and the average power loss per failure; the topology types include parallel topology, series topology, and matrix topology.

[0090] S2. Based on the grid parameters, calculate the internal grid loss index and reliability index of the offshore DC wind farm; based on the topology type and the corresponding grid parameters, calculate the construction cost index corresponding to the topology type.

[0091] It should be noted that in step S2, the internal network loss index, construction cost index and reliability index of the offshore DC wind farm are calculated based on the grid parameters and / or topology type obtained in step S1, so as to provide data for the subsequent calculation of the economic cost of each topology type.

[0092] S3. Obtain weighted data, market electricity sales price and estimated operating life of offshore DC wind farms. Calculate the economic cost corresponding to each topology type based on the weighted data, market electricity sales price, estimated operating life, internal grid loss index, reliability index, and construction cost index for each topology type.

[0093] It should be noted that in step S3, the weight data, market electricity price, and estimated operating life are first obtained. Then, the economic cost of each topology type is calculated by combining the internal network loss index, construction cost index, and reliability index obtained in step S2. In this embodiment, the weight data includes the weights of the internal network loss index, the construction cost index, and the reliability index.

[0094] S4. Select the topology type with the lowest economic cost from all topology types as the internal network topology of the offshore DC wind farm.

[0095] It should be noted that in step S4, the topology with the smallest economic cost value is selected based on the economic cost of each topology type calculated in step S3. The topology type with the smallest economic cost value is used as the internal network topology of the offshore DC wind farm, which is also the optimal internal network topology of the offshore DC wind farm.

[0096] This application provides a method for screening the internal grid topology of a DC offshore wind farm, including obtaining the topology type of the offshore DC wind farm and the corresponding grid parameters for each topology type; calculating the internal grid loss index and reliability index of the offshore DC wind farm based on the grid parameters; calculating the construction cost index corresponding to the topology type based on the topology type and the corresponding grid parameters; obtaining weight data, the market electricity price per unit and the estimated operating life of the offshore DC wind farm; calculating the economic cost corresponding to each topology type based on the weight data, the market electricity price per unit, the estimated operating life, the internal grid loss index, the reliability index, and the construction cost index for each topology type; and selecting the topology type with the lowest economic cost value from all topology types as the internal grid topology of the offshore DC wind farm. The proposed method for selecting the internal grid topology of a DC offshore wind farm first calculates the internal grid loss index, reliability index, and construction cost index for each topology type based on the obtained grid parameters and topology type. Then, it calculates the economic cost of each topology type and selects the topology type with the lowest economic cost from all topology types as the internal grid topology of the offshore DC wind farm, thus achieving the selection of the optimal internal grid topology for the offshore DC wind farm. This method solves the technical problem of existing evaluation methods that do not select the optimal internal grid topology for offshore DC wind farms.

[0097] In one embodiment of this application, the internal grid loss index of an offshore DC wind farm is calculated based on grid parameters, including:

[0098] Each DC cable is segmented to obtain a unit cable; based on the effective value of the average current in the first year, the unit resistance value, and the cable length of the unit cable, the annual average power loss of the corresponding DC cable is calculated.

[0099] The first power loss of the corresponding DC circuit breaker is calculated based on the second year's average effective current value and the resistance value of the DC circuit breaker.

[0100] The second power loss of the corresponding DC converter station is calculated based on the annual average power effective value and efficiency of each DC converter station.

[0101] The internal grid loss index of offshore DC wind farms is calculated based on the annual average operating time, number of cables, number of DC circuit breakers, number of DC converter stations, annual average power loss, first power loss and second power loss.

[0102] It should be noted that the internal grid losses of a DC-type offshore wind farm include the losses of the DC wind turbines and the losses of the collection network. Due to the current lack of actual engineering data for DC wind turbines, their losses are difficult to calculate. However, the internal grid topology screening method for this DC-type offshore wind farm assumes that the model and location of the DC wind turbines are the same. Therefore, changes in the internal grid topology can be considered as not altering the internal grid losses of the wind turbines; that is, the power loss of the wind turbines within the offshore DC wind farm can be treated as a constant. This incremental method for screening the internal grid topology of a DC-type offshore wind farm can ignore the impact of wind turbine losses in comparative analysis, focusing instead on the impact of the internal grid topology on the internal power losses of the offshore DC wind farm. Therefore, only the power losses of the collection network need to be calculated, including cable losses, DC circuit breaker losses, and DC converter station losses.

[0103] Figure 2 This is a schematic diagram illustrating the segmentation of DC cables in the internal network topology screening method for DC-type offshore wind farms described in this application embodiment.

[0104] In the collection network of an offshore DC wind farm, the current intensities flowing through different sections of each DC cable vary, resulting in different power losses. Therefore, it is necessary to first calculate the losses segment by segment and then accumulate the losses segment by segment to obtain a more accurate comparison result. Thus, a schematic diagram illustrating the current calculation for different segments under the same branch is shown below. Figure 2 As shown. In this embodiment, the annual average power loss of the corresponding DC cable is calculated using the cable loss formula based on the effective value of the average current in the first year, the unit resistance value, and the cable length per unit cable. The cable loss formula is:

[0105]

[0106] In the formula, P Cablek Let i be the average annual power loss of the k-th DC cable. m R is the effective value of the average current of the first year for the m-th segment of the unit cable. Cablen Let L be the unit resistance value of the nth segment of the cable. n Let n be the length of the nth unit cable segment, where n is a natural number greater than 1.

[0107] It should be noted that R Cablen =π(D / 2) 2 ρ and D are the diameters of the DC cable, and ρ is the resistivity of the DC cable.

[0108] In this embodiment, the first power loss of the corresponding DC circuit breaker is calculated using the circuit breaker loss formula based on the second annual average current effective value and the resistance value of each DC circuit breaker; the circuit breaker loss formula is: In the formula, e is a natural number greater than 1, and i Brke R is the effective value of the average current in the second year for the e-th DC circuit breaker. Brke Let P be the resistance value of the e-th DC circuit breaker. Brke This represents the first power loss of the e-th DC circuit breaker.

[0109] In this embodiment, the second power loss of the corresponding DC converter station is calculated using the converter station loss formula based on the annual average effective power value and efficiency of each DC converter station; the converter station loss formula is: In the formula, v is a natural number greater than 1, and p v Let v be the annual average effective power value of the v-th DC converter. Let P be the efficiency of the v-th DC converter. Conv This represents the second power loss of the vth DC converter station.

[0110] In this embodiment, the internal grid loss index of the offshore DC wind farm is calculated using the internal grid loss formula based on the annual average operating time, number of cables, number of DC circuit breakers, number of DC converter stations, annual average power loss, first power loss, and second power loss. The internal grid loss formula is as follows:

[0111]

[0112] In the formula, W ss T represents the internal grid loss index for offshore DC wind farms. y_av denoted as n1, n2, and n3, respectively, represent the annual average operating time of the offshore DC wind farm, and n1, n2, and n3 represent the number of cables, DC circuit breakers, and DC converter stations within the offshore DC wind farm.

[0113] In one embodiment of this application, the construction cost index corresponding to the topology type is calculated based on the topology type and the corresponding power grid parameters, including:

[0114] The cost of submarine DC cables is calculated using the cable cost formula based on the number of cables, total cable length, cable capacity, and cable cost coefficient; and / or

[0115] If the topology is a series topology, the cost of the submarine DC cable will be used as the construction cost indicator.

[0116] If the topology is a parallel topology, the construction cost index is calculated based on the cost of submarine DC cables and the additional investment in DC converter stations.

[0117] If the topology is a matrix topology, the construction cost index is obtained based on the cost of submarine DC cables, the additional investment in DC converter stations, and the cost of DC circuit breakers.

[0118] The formula for cable cost is as follows:

[0119]

[0120] In the formula, I nvcable Let S be the cost of the submarine DC cable, K be the cable cost coefficient, and S be the cost of the cable. i Let l be the total length of the i-th cable. i Let be the cable capacity of the i-th cable.

[0121] It should be noted that construction cost is a crucial consideration when constructing offshore DC wind farms. The internal network construction cost of an offshore DC wind farm refers to the investment cost of building the internal network topology, including: wind turbine costs, DC cable costs, DC circuit breaker costs, and DC converter station costs. The method for selecting the internal network topology structure for this DC offshore wind farm analyzes the impact of the internal network topology on the economics of the wind farm. When the number and model of wind turbines are given, the comparison of wind turbine costs can be ignored; the main focus is on comparing the investment costs of DC cables, DC circuit breakers, and DC converter stations in the collection network under different structures. The costs of DC cables, DC circuit breakers, and high-power DC converter stations can also be obtained through market inquiries. In this embodiment, the cost of the DC cable on the seabed of the offshore DC wind farm can be calculated by using the direct proportional relationship between the investment cost of any section of DC cable and the cable length and cable capacity, as shown in the cable cost formula.

[0122] In this embodiment, if a parallel topology is adopted, a large-capacity DC converter station needs to be constructed, which will result in unique additional investment. nvStation The construction cost index for a parallel topology is the cost of the submarine DC cable plus the additional investment in the DC converter station. sum =I nvStation +I nvcable Similarly, if a matrix topology is used, an additional batch of DC circuit breakers needs to be installed on top of the parallel topology. The cost of these additional DC circuit breakers is I. nvBrk The construction cost index Inv for matrix topology should also be considered. sum =I nvStation +I nvcable +I nvBrk .

[0123] In one embodiment of this application, the reliability indicators of an offshore DC wind farm are calculated based on grid parameters, including:

[0124] The energy loss of a DC cable is calculated using the energy loss formula based on the number of electronic components in the DC cable, the annual average number of faults, the average repair time for a single fault, and the average power loss per fault.

[0125] The energy loss of a DC circuit breaker is calculated using the energy loss formula based on the number of electronic components in the DC circuit breaker, the annual average number of faults corresponding to the DC circuit breaker, the average repair time of a single fault, and the average power loss per fault.

[0126] The energy loss of the DC converter is calculated using the energy loss formula based on the number of electronic components in the DC converter, the annual average number of failures, the average repair time for a single failure, and the average power loss per failure.

[0127] Based on the energy loss of DC cables, DC circuit breakers, and DC converters, the expected energy loss of offshore DC wind farms is calculated, and the expected energy loss is used as a reliability indicator.

[0128] The energy loss formula is as follows:

[0129]

[0130] In the formula, N i Let λ be the number of the i-th electronic component, which includes DC cables, DC circuit breakers, and DC converters. i h represents the average number of failures per year for the i-th electronic component. i Let be the mean time to repair a single fault of the i-th electronic component, λ be the average annual reliability of the electronic component, h be the average annual repair time to repair a single fault of the electronic component, and P be the mean time to repair a single fault of the electronic component. F Let W be the average power loss per fault in an offshore DC wind farm, and let W be the energy loss of electronic components.

[0131] It should be noted that compared to offshore AC wind farms, offshore DC wind farms operate in harsher environments, are more difficult to maintain, and have higher reliability requirements. Therefore, when selecting the internal network topology for large-scale offshore DC wind farms, its impact on reliability must be considered. Indicators characterizing the reliability of offshore DC wind farms include parameters such as average annual number of failures, average repair time per failure, and estimated energy (e.g., power) loss. Since reliability data for DC wind turbines in offshore DC wind farms is currently lacking, the incremental comparison method is used to select the internal network topology for this type of offshore wind farm. When comparing the reliability of the internal network of an offshore DC wind farm, DC wind turbines with the same reliability can still be ignored. Only the reliability parameters of electronic components in the internal network of the offshore DC wind farm need to be compared. Specifically, it is only necessary to consider the impact of the DC cables in the network and the different electronic components required for certain topology types on the reliability of the offshore DC wind farm. With the reliability assessment parameters of key electronic components (such as DC cables, DC circuit breakers, and DC converter stations) already determined, the reliability index of each electronic component can be calculated using the energy loss formula.

[0132] In this embodiment, the calculated energy loss of the DC cable, the energy loss of the DC circuit breaker, and the energy loss of the DC converter are added together to obtain the expected energy loss of the offshore DC wind farm, which is also the reliability index W of the offshore DC wind farm. F，loss .

[0133] In this embodiment, since the requirements for the three major indicators will differ for each offshore wind farm, and considering the time value of money, the three indicators—internal grid loss, reliability, and construction cost—can be assigned full weights based on the investment needs of the offshore wind farm's construction. The weights of the internal grid loss, reliability, and construction cost indicators are as follows: .

[0134] In one embodiment of this application, the method for selecting the internal grid topology of the DC-type offshore wind farm includes: calculating the economic cost corresponding to each topology type using an economic cost formula based on weighted data, market electricity price, estimated operating life, internal grid loss index, reliability index, and construction cost index for each topology type; the economic cost formula is: In the formula, E sum For economic costs, These represent the weights of the internal network loss index, reliability index, and construction cost index, respectively, k. p N represents the market sales price of electricity from offshore DC wind farms. y For the estimated operational life of offshore DC wind farms, W ss Inv is an internal network loss indicator. sum W is a construction cost indicator.F，loss This is a reliability indicator.

[0135] Example 2:

[0136] Figure 3 This is a schematic diagram of the internal network topology screening device for a DC-type offshore wind farm as described in an embodiment of this application.

[0137] like Figure 3 As shown in the figure, this application provides a device for screening the internal network topology of a DC offshore wind farm, including a data acquisition module 10, an index calculation module 20, a cost calculation module 30, and a topology screening module 40.

[0138] The data acquisition module 10 is used to acquire the topology type of the offshore DC wind farm and the grid parameters corresponding to each topology type;

[0139] The index calculation module 20 is used to calculate the internal grid loss index and reliability index of the offshore DC wind farm based on the grid parameters; and to calculate the construction cost index corresponding to the topology type based on the topology type and the corresponding grid parameters.

[0140] The cost calculation module 30 is used to obtain weight data, market electricity sales price and estimated operating life of offshore DC wind farms, and calculate the economic cost corresponding to each topology type based on the weight data, market electricity sales price, estimated operating life, internal network loss index, reliability index and construction cost index of each topology type.

[0141] The topology filtering module 40 is used to filter out the topology type with the lowest economic cost value from all topology types as the internal network topology of the offshore DC wind farm.

[0142] The grid parameters include the average annual operating time, the first-year average effective value of the current injected into the unit cable by each wind turbine, cable length, unit resistance value of the cable, total cable length, cable capacity, cable cost coefficient, number of cables, the second-year average effective value of the current of the DC circuit breaker, the resistance value of the DC circuit breaker, the cost of the DC circuit breaker, the number of DC circuit breakers, the annual average effective value of the power of the DC converter station, the efficiency of the DC converter station, the additional investment of the DC converter station, the number of DC converter stations, the number of electronic components, the average number of annual failures, the average repair time of a single failure, and the average power loss per failure; the topology types include parallel topology, series topology, and matrix topology.

[0143] In this embodiment, the cost calculation module 30 is further configured to calculate the economic cost corresponding to each topology type using an economic cost formula based on weighted data, market electricity price, estimated operating life, internal network loss index, reliability index, and construction cost index for each topology type; the economic cost formula is: In the formula, E sum For economic costs, These are the weighted data for internal network loss indicators, reliability indicators, and construction cost indicators, respectively, k. p N represents the market sales price of electricity from offshore DC wind farms. y For the estimated operational life of offshore DC wind farms, W ss Inv is an internal network loss indicator. sum W is a construction cost indicator. F，loss This is a reliability indicator.

[0144] In this embodiment of the application, the indicator calculation module 20 includes a first indicator calculation submodule, a second indicator calculation submodule, and a third indicator calculation submodule;

[0145] The first indicator calculation submodule is used to segment each DC cable to obtain a unit cable; calculate the annual average power loss of the corresponding DC cable using the cable loss formula based on the first annual average current effective value, unit resistance value, and cable length of the unit cable; calculate the first power loss of the corresponding DC circuit breaker using the circuit breaker loss formula based on the second annual average current effective value and resistance value of each DC circuit breaker; and calculate the second power loss of the corresponding DC converter station using the converter station loss formula based on the annual average power effective value and efficiency of each DC converter station.

[0146] The second indicator calculation submodule is used to calculate the energy loss of electronic components based on the number of electronic components, the annual average number of failures corresponding to the electronic components, the average repair time of a single failure, and the average power loss per failure using the energy loss formula. Based on the energy loss calculation of all electronic components, the expected energy loss of the offshore DC wind farm is obtained, and the expected energy loss is used as a reliability indicator.

[0147] The third indicator calculation submodule is used to calculate the cost of submarine DC cables using the cable cost formula based on the number of cables, total cable length, cable capacity, and cable cost coefficient; and / or, if the topology type is a series topology, the cost of submarine DC cables is used as the construction cost indicator; if the topology type is a parallel topology, the construction cost indicator is calculated based on the cost of submarine DC cables and the additional investment in DC converter stations; if the topology type is a matrix topology, the construction cost indicator is calculated based on the cost of submarine DC cables, the additional investment in DC converter stations, and the cost of DC circuit breakers.

[0148] The cable loss formula is as follows:

[0149]

[0150] The circuit breaker loss formula is: ;

[0151] The converter station loss formula is: ;

[0152] The energy loss formula is:

[0153]

[0154] The formula for cable cost is:

[0155]

[0156] In the formula, I nvcable Let S be the cost of the submarine DC cable, K be the cable cost coefficient, and S be the cost of the cable. i Let l be the total length of the i-th cable. i P represents the cable capacity of the i-th cable; Cablek Let i be the average annual power loss of the k-th DC cable. m R is the effective value of the average current of the first year for the m-th segment of the unit cable. Cablen Let L be the unit resistance value of the nth segment of the cable. n Let i be the length of the nth unit cable segment, where n, e, and v are all natural numbers greater than 1. Brke R is the effective value of the average current in the second year for the e-th DC circuit breaker. Brke Let p be the resistance value of the e-th DC circuit breaker. v Let v be the annual average effective power value of the v-th DC converter. Let P be the efficiency of the v-th DC converter. Conv For the second power loss of the vth DC converter station, P Brke N represents the first power loss of the e-th DC circuit breaker; i Let λ be the number of the i-th electronic component, which includes DC cables, DC circuit breakers, and DC converters. i h represents the average number of failures per year for the i-th electronic component. i Let be the mean time to repair a single fault of the i-th electronic component, λ be the average annual reliability of the electronic component, h be the average annual repair time to repair a single fault of the electronic component, and P be the mean time to repair a single fault of the electronic component. F Let W be the average power loss per fault in an offshore DC wind farm, and let W be the energy loss of electronic components.

[0157] It should be noted that the modules in the device of Embodiment 2 correspond to the steps in the method of Embodiment 1. The content of the method for screening the internal grid topology of the DC offshore wind farm has been described in Embodiment 1, and the module content of the device for screening the internal grid topology of the DC offshore wind farm will not be described in detail in this embodiment.

[0158] Example 3:

[0159] Figure 4 This is a schematic diagram of the terminal device described in an embodiment of this application.

[0160] like Figure 4 As shown, this application provides a terminal device, including a processor and a memory;

[0161] Memory is used to store program code and transfer the program code to the processor;

[0162] The processor is used to execute the above-mentioned method for filtering the internal network topology of a DC-type offshore wind farm according to the instructions in the program code.

[0163] It should be noted that the processor is used to execute the steps in the above embodiment of the method for screening the internal network topology of a DC-type offshore wind farm according to the instructions in the program code. Alternatively, when the processor executes the computer program, it implements the functions of each module / unit in the above system / device embodiments.

[0164] For example, a computer program can be divided into one or more modules / units, one or more of which are stored in memory and executed by a processor to complete this application. One or more modules / units can be a series of computer program instruction segments capable of performing a specific function, which describe the execution process of the computer program in a terminal device.

[0165] Terminal devices can be computing devices such as desktop computers, laptops, handheld computers, and cloud servers. Terminal devices may include, but are not limited to, processors and memory. Those skilled in the art will understand that this does not constitute a limitation on the terminal device, which may include more or fewer components than illustrated, or combinations of certain components, or different components. For example, a terminal device may also include input / output devices, network access devices, buses, etc.

[0166] The processor can be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), off-the-shelf programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor can be a microprocessor or any conventional processor, etc.

[0167] Memory can be an internal storage unit of a terminal device, such as a hard drive or RAM. Memory can also be an external storage device, such as a plug-in hard drive, smart memory card (SMC), secure digital card (SD) card, or flash card. Furthermore, memory can include both internal and external storage units. Memory is used to store computer programs and other programs and data required by the terminal device. Memory can also be used to temporarily store data that has been output or will be output.

[0168] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0169] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection between apparatuses or units through some interfaces, and may be electrical, mechanical, or other forms.

[0170] The units described as separate components may or may not be physically separate. 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 the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0171] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0172] If the integrated unit is implemented as 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 this application, in essence, 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. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0173] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A method for selecting the internal grid topology of a DC-type offshore wind farm, characterized in that, Includes the following steps: Obtain the topology type of the offshore DC wind farm and the corresponding grid parameters for each topology type; Based on the power grid parameters, the internal grid loss index and reliability index of the offshore DC wind farm are calculated; based on the topology type and the corresponding power grid parameters, the construction cost index corresponding to the topology type is calculated. Obtain weighted data, market electricity sales price and estimated operating life of offshore DC wind farms, and calculate the economic cost corresponding to each topology type based on the weighted data, market electricity sales price, estimated operating life, internal grid loss index, reliability index and construction cost index of each topology type. The topology with the lowest economic cost value among all the topology types is selected as the internal network topology of the offshore DC wind farm; The grid parameters include: annual average operating time, first-year average effective value of current injected into a unit cable by each wind turbine, cable length, unit resistance value of the cable, total cable length, cable capacity, cable cost coefficient, number of cables, second-year average effective value of current of DC circuit breakers, resistance value of DC circuit breakers, cost of DC circuit breakers, number of DC circuit breakers, annual average effective value of power of DC converter stations, efficiency of DC converter stations, additional investment of DC converter stations, number of DC converter stations, number of electronic components, annual average number of failures, average repair time of a single failure, and average power loss per failure; the topology types include parallel topology, series topology, and matrix topology. Based on the aforementioned grid parameters, the internal grid loss indicators for offshore DC wind farms are calculated as follows: Each DC cable is segmented to obtain a unit cable; the annual average power loss of the corresponding DC cable is calculated based on the first annual average current effective value, the unit resistance value, and the cable length of the unit cable. The first power loss of the corresponding DC circuit breaker is calculated based on the second annual average current effective value of each DC circuit breaker and the resistance value of the DC circuit breaker. The second power loss of the corresponding DC converter station is calculated based on the annual average power effective value and the efficiency of each DC converter station. The internal grid loss index of the offshore DC wind farm is calculated based on the annual average operating time, the number of cables, the number of DC circuit breakers, the number of DC converter stations, the annual average power loss, the first power loss, and the second power loss. Based on the weighted data, the market electricity price, the estimated operating life, the internal network loss index, the reliability index, and the construction cost index for each topology type, an economic cost formula is used to calculate the economic cost corresponding to each topology type; the economic cost formula is: In the formula, E sum For economic costs, These represent the weights of the internal network loss index, reliability index, and construction cost index, respectively, k. p N represents the market sales price of electricity from offshore DC wind farms. y For the estimated operational life of offshore DC wind farms, W ss Inv is an internal network loss indicator. sum W is a construction cost indicator. F，loss This is a reliability indicator.

2. The method for screening the internal grid topology of a DC-type offshore wind farm according to claim 1, characterized in that, include: The annual average power loss of the corresponding DC cable is calculated using the cable loss formula based on the first annual average current effective value, the unit resistance value, and the cable length per unit cable. The first power loss of each DC circuit breaker is calculated using the circuit breaker loss formula based on the second annual average current effective value and the resistance value of the DC circuit breaker; the second power loss of each DC converter station is calculated using the converter station loss formula based on the annual average power effective value and the efficiency; the cable loss formula is: ； The circuit breaker loss formula is as follows: ; The converter station loss formula is as follows: ; In the formula, P Cablek Let i be the average annual power loss of the k-th DC cable. m R is the effective value of the average current of the first year for the m-th segment of the unit cable. Cablen Let L be the unit resistance value of the nth segment of the cable. n Let i be the length of the nth unit cable segment, where n, e, and v are all natural numbers greater than 1. Brke R is the effective value of the average current in the second year for the e-th DC circuit breaker. Brke Let p be the resistance value of the e-th DC circuit breaker. v Let v be the annual average effective power value of the v-th DC converter. Let P be the efficiency of the v-th DC converter. Conv For the second power loss of the vth DC converter station, P Brke This represents the first power loss of the e-th DC circuit breaker.

3. The method for screening the internal grid topology of a DC-type offshore wind farm according to claim 1, characterized in that, Based on the aforementioned grid parameters, the reliability indicators of offshore DC wind farms include: The energy loss of the DC cable is calculated using the energy loss formula based on the number of electronic components in the DC cable, the annual average number of faults corresponding to the DC cable, the average repair time of a single fault, and the average power loss per fault. The energy loss of the DC circuit breaker is calculated using the energy loss formula based on the number of electronic components of the DC circuit breaker, the annual average number of faults corresponding to the DC circuit breaker, the average repair time of a single fault, and the average power loss per fault. The energy loss of the DC converter is calculated using the energy loss formula based on the number of electronic components in the DC converter, the annual average number of faults corresponding to the DC converter, the average repair time of a single fault, and the average power loss per fault. The expected energy loss of the offshore DC wind farm is calculated based on the energy loss of the DC cable, the energy loss of the DC circuit breaker, and the energy loss of the DC converter, and the expected energy loss is used as a reliability indicator. The energy loss formula is as follows: ； In the formula, N i Let λ be the number of the i-th electronic component, which includes DC cables, DC circuit breakers, and DC converters. i h represents the average number of failures per year for the i-th electronic component. i Let be the mean time to repair a single fault of the i-th electronic component, λ be the average annual reliability of the electronic component, h be the average annual repair time to repair a single fault of the electronic component, and P be the mean time to repair a single fault of the electronic component. F Let W be the average power loss per fault in an offshore DC wind farm, and let W be the energy loss of electronic components.

4. The method for screening the internal grid topology of a DC-type offshore wind farm according to claim 1, characterized in that, Based on the topology type and the corresponding power grid parameters, the construction cost indicators corresponding to the topology type are calculated as follows: The cost of the submarine DC cable is calculated using a cable cost formula based on the number of cables, the total length of the cables, the cable capacity, and the cable cost coefficient; and / or If the topology is a series topology, the cost of the submarine DC cable will be used as a construction cost indicator. If the topology is a parallel topology, the construction cost index is calculated based on the cost of the submarine DC cable and the additional investment in the DC converter station. If the topology type is a matrix topology, the construction cost index is obtained based on the cost of the submarine DC cable, the additional investment in the DC converter station, and the cost of the DC circuit breaker. The cable cost formula is as follows: ； In the formula, I nvcable Let S be the cost of the submarine DC cable, K be the cable cost coefficient, and S be the cost of the cable. i Let l be the total length of the i-th cable. i Let be the cable capacity of the i-th cable.

5. A device for screening the internal grid topology of a DC-type offshore wind farm, characterized in that, It includes a data acquisition module, an indicator calculation module, a cost calculation module, and a topology filtering module; The data acquisition module is used to acquire the topology type of the offshore DC wind farm and the grid parameters corresponding to each topology type; The index calculation module is used to calculate, based on the grid parameters, the internal grid loss index and reliability index of the offshore DC wind farm; and to calculate, based on the topology type and the corresponding grid parameters, the construction cost index corresponding to the topology type. The cost calculation module is used to acquire weight data, the market electricity price and estimated operating life of the offshore DC wind farm, and calculate the economic cost corresponding to each topology type based on the weight data, the market electricity price, the estimated operating life, the internal network loss index, the reliability index, and the construction cost index of each topology type. The topology filtering module is used to filter out the topology type with the lowest economic cost value from all the topology types as the internal network topology of the offshore DC wind farm. The grid parameters include: annual average operating time, first-year average effective value of current injected into a unit cable by each wind turbine, cable length, unit resistance value of the cable, total cable length, cable capacity, cable cost coefficient, number of cables, second-year average effective value of current of DC circuit breakers, resistance value of DC circuit breakers, cost of DC circuit breakers, number of DC circuit breakers, annual average effective value of power of DC converter stations, efficiency of DC converter stations, additional investment of DC converter stations, number of DC converter stations, number of electronic components, annual average number of failures, average repair time of a single failure, and average power loss per failure; the topology types include parallel topology, series topology, and matrix topology. The cost calculation module is further configured to calculate the economic cost corresponding to each topology type using an economic cost formula based on the weighted data, the market electricity price, the estimated operating life, the internal network loss index, the reliability index, and the construction cost index for each topology type; the economic cost formula is: In the formula, E sum For economic costs, These are the weighted data for internal network loss indicators, reliability indicators, and construction cost indicators, respectively, k. p N represents the market sales price of electricity from offshore DC wind farms. y For the estimated operational life of offshore DC wind farms, W ss Inv is an internal network loss indicator. sum W is a construction cost indicator. F，loss For reliability indicators; The index calculation module includes a first index calculation submodule, which is used to segment each DC cable to obtain a unit cable; calculate the annual average power loss of the corresponding DC cable using a cable loss formula based on the first annual average current effective value, the unit resistance value, and the cable length of the unit cable; calculate the first power loss of the corresponding DC circuit breaker using a circuit breaker loss formula based on the second annual average current effective value and the resistance value of each DC circuit breaker; and calculate the second power loss of the corresponding DC converter station using a converter station loss formula based on the annual average power effective value and the efficiency of each DC converter station. The index calculation module is also used to calculate, based on the annual average operating time, the number of cables, the number of DC circuit breakers, the number of DC converter stations, the annual average power loss, the first power loss, and the second power loss, to obtain the internal grid loss index of the offshore DC wind farm.

6. The internal grid topology screening device for DC-type offshore wind farms according to claim 5, characterized in that, The indicator calculation module further includes a second indicator calculation submodule and a third indicator calculation submodule; The second index calculation submodule is used to calculate the energy loss of electronic components based on the number of electronic components, the annual average number of failures corresponding to the electronic components, the average repair time of a single failure, and the average power loss per failure using an energy loss formula; and to calculate the expected energy loss of the offshore DC wind farm based on the energy loss of all electronic components, and to use the expected energy loss as a reliability index. The third indicator calculation submodule is used to calculate the cost of the submarine DC cable using a cable cost formula based on the number of cables, the total length of the cables, the cable capacity, and the cable cost coefficient; and / or, if the topology type is a series topology, the cost of the submarine DC cable is used as the construction cost indicator; if the topology type is a parallel topology, the construction cost indicator is calculated based on the cost of the submarine DC cable and the additional investment in the DC converter station; if the topology type is a matrix topology, the construction cost indicator is calculated based on the cost of the submarine DC cable, the additional investment in the DC converter station, and the cost of the DC circuit breaker. The cable loss formula is as follows: ； The circuit breaker loss formula is as follows: ; The converter station loss formula is as follows: ; The energy loss formula is as follows: ； The formula for the cost of the cable is: ； In the formula, I nvcable Let S be the cost of the submarine DC cable, K be the cable cost coefficient, and S be the cost of the cable. i Let l be the total length of the i-th cable. i P represents the cable capacity of the i-th cable; Cablek Let i be the average annual power loss of the k-th DC cable. m R is the effective value of the average current of the first year for the m-th segment of the unit cable. Cablen Let L be the unit resistance value of the nth segment of the cable. n Let i be the length of the nth unit cable segment, where n, e, and v are all natural numbers greater than 1. Brke R is the effective value of the average current in the second year for the e-th DC circuit breaker. Brke Let p be the resistance value of the e-th DC circuit breaker. v Let v be the annual average effective power value of the v-th DC converter. Let P be the efficiency of the v-th DC converter. Conv For the second power loss of the vth DC converter station, P Brke N represents the first power loss of the e-th DC circuit breaker; i Let λ be the number of the i-th electronic component, which includes DC cables, DC circuit breakers, and DC converters. i h represents the average number of failures per year for the i-th electronic component. i Let be the mean time to repair a single fault of the i-th electronic component, λ be the average annual reliability of the electronic component, h be the average annual repair time to repair a single fault of the electronic component, and P be the mean time to repair a single fault of the electronic component. F Let W be the average power loss per fault in an offshore DC wind farm, and let W be the energy loss of electronic components.

7. A terminal device, characterized in that, Including the processor and memory; The memory is used to store program code and transmit the program code to the processor; The processor is configured to execute the internal network topology screening method for DC-type offshore wind farms as described in any one of claims 1-4, according to the instructions in the program code.

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