Method and device for determining direct-current drop point of multi-direct-current feed-in receiving end power grid

Abstract

The invention discloses a method and a device for determining a direct current drop point of a multi-direct-current feed-in receiving-end power grid. The method comprises the following steps of: obtaining an electric power gap of each subarea of the receiving-end power grid and a direct current full transmission power and an operation mode of each transmitting-end direct current line; based on the power gap of each subarea of the receiving-end power grid and the direct-current full transmission power and the operation mode of each transmitting-end direct-current line, performing matching degree evaluation on the direct-current drop points and the subareas of the receiving-end power grid, and giving an initial drop point scheme set of the receiving-end power grid; performing voltage stability evaluation and fault risk evaluation on the initial drop point scheme set, and giving a screened and updated optimized drop point scheme set; and based on matching degree evaluation, voltage stability evaluation and fault risk evaluation results, carrying out comprehensive evaluation on the optimized drop point scheme set of the receiving-end power grid, and giving an optimal optimized drop point scheme in the optimized drop point scheme set. According to the invention, the stable and economic operation capability of the multi-direct-current feed-in receiving end power grid can be improved.

Description

Technical Field

[0001] This invention belongs to the field of power system technology, and specifically relates to a method and apparatus for determining the DC landing point of a multi-DC feed-in receiving-end power grid. Background Technology

[0002] With the large-scale development of new energy sources and the rapid development of multiple DC feed-in receiving-end power grids, the planning and operation of AC / DC hybrid systems face severe challenges. In receiving-end power grids with multiple centralized DC feed-in, the optimal layout of DC feed-in points is a complex system decision-making problem that requires consideration of multiple factors to improve the stable and economical operation of the large AC / DC power grid. Among these factors, the operating mode of the sending-end power grid (islanded or interconnected) has a critical impact on the planning of receiving-end feed-in points. For example, in the sending-end islanded mode, the power fluctuations of new energy sources (such as wind power and photovoltaics) are large. Due to the lack of support from the large power grid, the output is significantly random and intermittent, leading to unstable power fed into the receiving end via DC, exacerbating the absorption pressure and stability risks of the receiving-end power grid. In the sending-end interconnected mode, the fluctuations of new energy sources are smoothed by the regional power grid, the DC power output is relatively stable, and the power flow distribution of the receiving-end power grid is more predictable.

[0003] The receiving-end power grid needs to dynamically adjust the DC landing point layout based on the fluctuation characteristics of the sending-end renewable energy sources to avoid power flow congestion, voltage instability, or fault propagation caused by power fluctuations. However, traditional planning methods often ignore the impact of sending-end fluctuations, resulting in poor adaptability of the landing point scheme in actual operation. For example, patent CN103986180A discloses a method for selecting DC landing points in the receiving-end power grid. It establishes the DC landing point region of the receiving-end power grid based on the principle of power balance; it calculates and analyzes all 500kV nodes within the DC landing point region established in step one using two stability indicators: static voltage stability and transient stability, to obtain feasible DC landing points; it selects two economic indicators: grid construction cost and network loss cost, the sum of which is the total economic cost of the landing point; and the node with the lowest total economic cost among the feasible DC landing points is the most economically efficient landing point. The receiving-end power grid DC landing point determination method proposed in this invention can select the most economically efficient landing point while ensuring the safe and stable operation of the power grid. This ensures both safe and reliable power supply to users and protects the interests of the power grid company, providing important guidance for the selection of DC landing points in the receiving-end power grid during power grid planning.

[0004] Therefore, how to transform the fluctuating characteristics of new energy at the sending end into quantitative decisions on the receiving end is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] To address the shortcomings of the existing technology, this invention provides a method and apparatus for determining the DC landing point of a multi-DC feed-in receiving-end power grid. This can improve the stable and economical operation capability of a multi-DC feed-in receiving-end power grid.

[0006] In a first aspect, the present invention provides a method for determining the DC landing point of a multi-DC feed-in receiving-end power grid, comprising: Obtain the power shortage of each section of the receiving-end power grid, as well as the full DC transmission power and operating mode of each sending-end DC line; Based on the power shortage of each section of the receiving-end power grid, the full DC transmission power and operating mode of each sending-end DC line, the matching degree between the DC landing point and the receiving-end power grid section is evaluated, and an initial landing point scheme set for the receiving-end power grid is given. Voltage stability and fault risk assessments are performed on the initial set of landing point schemes, and a set of optimized landing point schemes is provided after screening and updating. Based on the results of matching degree assessment, voltage stability assessment, and fault risk assessment, a comprehensive evaluation of the set of optimal landing point schemes for the receiving-end power grid is conducted, and the best optimal landing point scheme in the set of optimal landing point schemes is given.

[0007] Furthermore, the operating modes include isolated network operating mode and network operating mode.

[0008] Furthermore, based on the power shortage in each section of the receiving-end power grid, the full DC transmission capacity and operating mode of each sending-end DC line, the matching degree between the DC landing point and the receiving-end power grid section is evaluated, and an initial landing point scheme set for the receiving-end power grid is given, including: Based on the power shortage of each section of the receiving-end power grid, the full DC transmission power and operating mode of each sending-end DC line, determine the matching rules between each sending-end DC line and the power shortage of each section. Based on the matching rules between each sending-end DC line and the power gap of each region, all DC landing point schemes corresponding to each sending-end DC line and each region of the receiving-end power grid are given. Based on the matching rules between each sending-end DC line and the power gap of each zone, the power spatial matching degree between all sending-end DC lines and the power gap of each zone is determined. Based on the power spatial matching degree between all sending-end DC lines and the power gaps in each region, the schemes for each DC landing point of all sending-end DC lines are screened to provide an initial landing point scheme set for the receiving-end power grid.

[0009] Furthermore, the matching rules between each sending-end DC line and the power shortage in each zone are determined, including: Based on the operating mode of the sending-end DC line, the cumulative value of the power shortage in multiple zones is corrected, and combined with the corresponding full DC transmission power, the matching rules between each sending-end DC line and the power shortage in each zone are given.

[0010] Furthermore, based on the matching rules between each sending-end DC line and the power gap in each zone, the power spatial matching degree between all sending-end DC lines and the power gap in each zone is determined, including: Choose one DC landing point scheme from each sending-end DC line and give a set of multiple DC landing point schemes; Determine the total power shortage of multiple zones corresponding to each DC landing scheme in each DC landing scheme set; Based on the total power gap of multiple zones corresponding to each DC landing point scheme, and combined with the DC transmission capacity of all sending-end DC lines, the power spatial matching degree is given.

[0011] Furthermore, voltage stability and fault risk assessments are performed on the initial set of landing point schemes, and a filtered and updated set of optimized landing point schemes is provided, including: Based on the operating mode of each sending-end DC line, determine the control strategy for each initial landing point scheme; Based on the control strategy, simulations are performed on each initial landing point scheme to provide a voltage-stable initial landing point scheme. Fault simulations were performed on the initial landing point schemes with stable voltage, and the initial landing point schemes with fault risk in the fault simulation were optimized to obtain the optimized landing point scheme set.

[0012] Furthermore, based on the control strategy, simulations are performed on each initial landing point scheme to provide voltage-stable initial landing point schemes, including: Based on the control strategy, simulations are performed on each initial landing point scheme, and the voltage stiffness of all sending-end DC lines corresponding to each initial landing point scheme is given. Based on the voltage stiffness of all sending-end DC lines corresponding to each initial landing point scheme, determine the voltage support capability value of each initial landing point scheme. Based on the voltage support capability value of each initial landing point scheme, initial landing point schemes that are greater than or equal to the preset capability threshold are selected.

[0013] Furthermore, based on the voltage stiffness of all sending-end DC lines corresponding to each initial landing point scheme, the voltage support capability value of each initial landing point scheme is determined, including: The average voltage stiffness value is determined based on the voltage stiffness of all sending-end DC lines corresponding to each initial landing point scheme. Based on the power space matching degree corresponding to the initial landing point scheme set, the average voltage stiffness value is scaled to give the voltage support capability value of the initial landing point scheme.

[0014] Furthermore, fault simulations were performed on the initial landing point schemes with stable voltage, and the initial landing point schemes with fault risk in the fault simulation were optimized to obtain an optimized landing point scheme set, including: An N-1 fault simulation was performed on the selected initial landing point scheme to give the DC power loss of the receiving end grid during the fault and the total external power received by the receiving end grid before the fault. The severity value of the DC fault is determined based on the lost DC power and the total received external power. An initial landing point scheme with a DC fault severity value greater than a preset fault threshold is selected, and based on the matching rules between each sending-end DC line and the power gap in each zone, some DC landing points in the initial landing point scheme are divided. Based on the initial landing point scheme after partitioning, and combined with the initial landing point scheme that is less than or equal to the preset fault threshold, an optimized landing point scheme set is given.

[0015] Furthermore, an initial landing point scheme with a DC fault severity value greater than a preset fault threshold is selected. Based on the matching rules between each sending-end DC line and the power gap in each zone, some DC landing points in the initial landing point scheme are divided, including: Select an initial landing point scheme with a DC fault severity value greater than a preset fault threshold, and select a corresponding DC landing point of less than a predetermined number of sending-end DC lines from the initial landing point scheme. Based on the severity level of the DC fault in the initial landing point scheme and the matching rules between each sending-end DC line and the power gap in each zone, the candidate zone group corresponding to each selected sending-end DC line is given. Based on the candidate partition group corresponding to each selected DC sending end line, determine the corresponding DC landing point scheme after partitioning. The integrated and divided DC landing point schemes and the DC landing point schemes corresponding to the sending-end DC lines with a DC landing point greater than or equal to a predetermined number are given, and the initial landing point scheme after the division is presented.

[0016] Furthermore, based on the severity level of the DC fault in the initial landing point scheme and combined with the matching rules between each sending-end DC line and the power shortage in each zone, candidate zone groups corresponding to each selected sending-end DC line are given, including: Based on the severity level of the DC fault in the initial landing point scheme, the number of pre-defined DC landing points for the selected sending-end DC line is given. Based on the number of pre-divided DC landing points of the selected sending-end DC lines, and combined with the matching rules between each sending-end DC line and the power gap of each zone, the candidate zone group corresponding to each selected sending-end DC line is given. For each candidate partition group, the electrical distance to multiple DC landing points is determined and compared with a preset distance threshold. Candidate partition groups with at least one electrical distance less than the preset distance threshold are eliminated. Determine the total electrical distance of each of the remaining candidate partition groups and sort them by size, and give the candidate partition group with the largest total electrical distance.

[0017] Furthermore, based on the results of matching degree assessment, voltage stability assessment, and fault risk assessment, a comprehensive evaluation of the optimized landing point scheme set for the receiving-end power grid is conducted, and the optimal landing point scheme in the optimized landing point scheme set is given, including: Obtain the power spatial matching degree, voltage support capability value, and fault severity value of the optimized landing point scheme set, as well as the corresponding weight coefficients; The values ​​of power spatial matching degree, voltage support capability, and fault severity are standardized, and the standardized values ​​of power spatial matching degree, voltage support capability, and fault severity are given for each optimized landing point scheme. Based on the weighting coefficients corresponding to the standardized power spatial matching degree, voltage support capability value, and fault severity value of each optimized landing point scheme, a comprehensive evaluation index for each optimized landing point scheme is determined. Based on the ranking of comprehensive evaluation indicators, the DC full-power delivery scheme corresponding to the maximum comprehensive evaluation indicator is given.

[0018] Secondly, the present invention also provides a device for determining the DC landing point of a multi-DC feed-in receiving-end power grid, employing the aforementioned method for determining the DC landing point of a multi-DC feed-in receiving-end power grid, the device comprising: The data acquisition module is used to acquire the power gap of each section of the receiving-end power grid, as well as the full DC transmission power and operating mode of each sending-end DC line; The initial scheme determination module is used to evaluate the matching degree between the DC landing point and the receiving-end power grid section based on the power gap of each section of the receiving-end power grid, the full DC transmission power and operating mode of each sending-end DC line, and to give the initial landing point scheme set of the receiving-end power grid. The scheme optimization module is used to evaluate the voltage stability and fault risk of the initial landing point scheme set, and provide a filtered and updated optimized landing point scheme set. The scheme selection module is used to comprehensively evaluate the set of optimal landing schemes for the receiving-end power grid based on the results of matching degree assessment, voltage stability assessment, and fault risk assessment, and to provide the best optimal landing scheme in the set of optimal landing schemes.

[0019] Furthermore, the initial scheme determination module is used for: Based on the power shortage of each section of the receiving-end power grid, the full DC transmission power and operating mode of each sending-end DC line, determine the matching rules between each sending-end DC line and the power shortage of each section. Based on the matching rules between each sending-end DC line and the power gap of each region, all DC landing point schemes corresponding to each sending-end DC line and each region of the receiving-end power grid are given. Based on the matching rules between each sending-end DC line and the power gap of each zone, the power spatial matching degree between all sending-end DC lines and the power gap of each zone is determined. Based on the power spatial matching degree between all sending-end DC lines and the power gaps in each region, the schemes for each DC landing point of all sending-end DC lines are screened to provide an initial landing point scheme set for the receiving-end power grid.

[0020] Furthermore, the initial scheme determination module is used for: Based on the operating mode of the sending-end DC line, the cumulative value of the power shortage in multiple zones is corrected, and combined with the corresponding full DC transmission power, the matching rules between each sending-end DC line and the power shortage in each zone are given.

[0021] Furthermore, the initial scheme determination module is also used for: Choose one DC landing point scheme from each sending-end DC line and give a set of multiple DC landing point schemes; Determine the total power shortage of multiple zones corresponding to each DC landing scheme in each DC landing scheme set; Based on the total power gap of multiple zones corresponding to each DC landing point scheme, and combined with the DC transmission capacity of all sending-end DC lines, the power spatial matching degree is given.

[0022] Furthermore, the solution optimization module is used for: Based on the operating mode of each sending-end DC line, determine the control strategy for each initial landing point scheme; Based on the control strategy, simulations are performed on each initial landing point scheme to provide a voltage-stable initial landing point scheme. Fault simulations were performed on the initial landing point schemes with stable voltage, and the initial landing point schemes with fault risk in the fault simulation were optimized to obtain the optimized landing point scheme set.

[0023] Furthermore, the solution optimization module is used for: Based on the control strategy, simulations are performed on each initial landing point scheme, and the voltage stiffness of all sending-end DC lines corresponding to each initial landing point scheme is given. Based on the voltage stiffness of all sending-end DC lines corresponding to each initial landing point scheme, determine the voltage support capability value of each initial landing point scheme. Based on the voltage support capability value of each initial landing point scheme, initial landing point schemes that are greater than or equal to the preset capability threshold are selected.

[0024] Furthermore, the solution optimization module is used for: The average voltage stiffness value is determined based on the voltage stiffness of all sending-end DC lines corresponding to each initial landing point scheme. Based on the power space matching degree corresponding to the initial landing point scheme set, the average voltage stiffness value is scaled to give the voltage support capability value of the initial landing point scheme.

[0025] Furthermore, the solution optimization module is used for: An N-1 fault simulation was performed on the selected initial landing point scheme to give the DC power loss of the receiving end grid during the fault and the total external power received by the receiving end grid before the fault. The severity value of the DC fault is determined based on the lost DC power and the total received external power. An initial landing point scheme with a DC fault severity value greater than a preset fault threshold is selected, and based on the matching rules between each sending-end DC line and the power gap in each zone, some DC landing points in the initial landing point scheme are divided. Based on the initial landing point scheme after partitioning, and combined with the initial landing point scheme that is less than or equal to the preset fault threshold, an optimized landing point scheme set is given.

[0026] Furthermore, the solution optimization module is used for: Select an initial landing point scheme with a DC fault severity value greater than a preset fault threshold, and select a corresponding DC landing point of less than a predetermined number of sending-end DC lines from the initial landing point scheme. Based on the severity level of the DC fault in the initial landing point scheme and the matching rules between each sending-end DC line and the power gap in each zone, the candidate zone group corresponding to each selected sending-end DC line is given. Based on the candidate partition group corresponding to each selected DC sending end line, determine the corresponding DC landing point scheme after partitioning. The integrated and divided DC landing point schemes and the DC landing point schemes corresponding to the sending-end DC lines with a DC landing point greater than or equal to a predetermined number are given, and the initial landing point scheme after the division is presented.

[0027] Furthermore, the solution optimization module is also used for: Based on the severity level of the DC fault in the initial landing point scheme, the number of pre-defined DC landing points for the selected sending-end DC line is given. Based on the number of pre-divided DC landing points of the selected sending-end DC lines, and combined with the matching rules between each sending-end DC line and the power gap of each zone, the candidate zone group corresponding to each selected sending-end DC line is given. For each candidate partition group, the electrical distance to multiple DC landing points is determined and compared with a preset distance threshold. Candidate partition groups with at least one electrical distance less than the preset distance threshold are eliminated. Determine the total electrical distance of each of the remaining candidate partition groups and sort them by size, and give the candidate partition group with the largest total electrical distance.

[0028] Furthermore, the solution selection module is also used for: Obtain the power spatial matching degree, voltage support capability value, and fault severity value of the optimized landing point scheme set, as well as the corresponding weight coefficients; The values ​​of power spatial matching degree, voltage support capability, and fault severity are standardized, and the standardized values ​​of power spatial matching degree, voltage support capability, and fault severity are given for each optimized landing point scheme. Based on the weighting coefficients corresponding to the standardized power spatial matching degree, voltage support capability value, and fault severity value of each optimized landing point scheme, a comprehensive evaluation index for each optimized landing point scheme is determined. Based on the ranking of comprehensive evaluation indicators, the DC full-power delivery scheme corresponding to the maximum comprehensive evaluation indicator is given.

[0029] The present invention provides a method and apparatus for determining the DC landing point of a multi-DC feed-in receiving-end power grid, which has at least the following beneficial effects: (1) By comprehensively considering the matching degree assessment of the operation mode, voltage stability assessment and fault risk assessment, a quantitative correlation between the sending end fluctuation characteristics and the receiving end DC landing point planning can be established, and the low-precision static planning can be optimized into high-precision dynamic adaptation, which can effectively improve the stable and economical operation capability of the AC / DC hybrid power grid under the high proportion of new energy access.

[0030] (2) By correcting the power shortage through the operation mode, the impact of the sending end fluctuation on the receiving end consumption demand can be accurately reflected, and the planning accuracy of DC landing point can be improved. Attached Figure Description

[0031] Figure 1 A flowchart of a method for determining the DC landing point of a multi-DC feed-in receiving-end power grid provided by the present invention; Figure 2 This is an architectural diagram of a DC landing point determination method provided in a certain embodiment of the present invention; Figure 3 A flowchart illustrating an initial landing point scheme set provided in one embodiment of the present invention; Figure 4 A flowchart for determining the electrical spatial matching degree is provided in one embodiment of the present invention; Figure 5 A flowchart illustrating a set of optimized landing point schemes is provided for one embodiment of the present invention; Figure 6 A flowchart illustrating an initial landing point scheme is provided in one embodiment of the present invention; Figure 7 A flowchart illustrating the process of obtaining an optimized landing point scheme set according to a certain embodiment of the present invention; Figure 8 A flowchart for dividing a portion of DC landing points according to a certain embodiment of the present invention; Figure 9 A flowchart for providing candidate partition groups is provided as an embodiment of the present invention; Figure 10A flowchart illustrating the optimal landing point scheme provided in a certain embodiment of the present invention; Figure 11 This is a schematic diagram of a DC landing point determination device for a multi-DC feed-in receiving-end power grid provided by the present invention. Detailed Implementation

[0032] To better understand the above technical solutions, a detailed description of the solutions will be provided below in conjunction with the accompanying drawings and specific embodiments. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0033] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms, and “multiple” generally includes at least two unless the context clearly indicates otherwise.

[0034] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or device that includes said element.

[0035] In a receiving-end system with multiple centralized DC feeds, further considering the optimal layout of multiple DC landing points while taking into account the DC grid connection method is a complex system decision-making problem. It requires a comprehensive evaluation of the advantages and disadvantages of multiple DC feed-in receiving-end grid DC landing point schemes to improve the stable and economical operation capability of the AC / DC power grid. The structure of the receiving-end grid with multiple DC feeds consists of multiple sending-end grids connected to the receiving-end grid through DC systems to form an AC / DC hybrid system. The DC system is connected to the receiving-end grid through multiple DC landing points, and the sending-end grid and the DC system form sending-end DC lines. The DC landing point is the location where the DC system injects power into the receiving-end grid, corresponding to the high-voltage side bus of the main transformer in the receiving-end grid section (such as the 500kV / 1000kV bus).

[0036] like Figure 1 and Figure 2 As shown, the present invention provides a method for determining the DC landing point of a multi-DC feed-in receiving-end power grid, comprising: The system obtains the power shortage of each zone in the receiving-end power grid, as well as the full DC transmission capacity and operating mode of each sending-end DC line. Based on administrative boundaries, grid structure, and load density, the receiving-end power grid is divided into several independent zones. These zones must meet the following criteria: 1. The load share within the zone is ≥10% of the total load; 2. The zone has a 500kV hub substation for support; 3. New energy bases or concentrated load centers form separate zones. The power shortage is the difference between the zone's base load and local power supply. Operating modes include islanded operation mode and grid-connected operation mode. Based on the power shortage of each section of the receiving-end power grid, the full DC transmission power and operating mode of each sending-end DC line, the matching degree between the DC landing point and the receiving-end power grid section is evaluated, and the initial landing point scheme set of the receiving-end power grid is given; where the full DC transmission power is the maximum power that the sending-end DC line can stably transmit over a long period of time under the design or operating conditions. Voltage stability and fault risk assessments are performed on the initial set of landing point schemes, and a set of optimized landing point schemes is provided after screening and updating. Based on the results of matching degree assessment, voltage stability assessment, and fault risk assessment, a comprehensive evaluation of the set of optimal landing point schemes for the receiving-end power grid is conducted, and the best optimal landing point scheme in the set of optimal landing point schemes is given.

[0037] Considering that the sending-end DC transmission line has both islanded and grid-connected operation modes, the power fluctuations of new energy sources are larger when the sending-end grid operates in islanded mode, while the power fluctuations are smaller when it operates in grid-connected mode. Therefore, the receiving-end grid needs to plan the receiving-end landing points according to the characteristics of new energy sources under the operating mode adopted by the sending-end grid. This is specifically reflected in matching degree assessment and voltage stability assessment.

[0038] like Figure 3 As shown, in practical application scenarios, based on the power shortage of each section of the receiving-end power grid, the full DC transmission power and operating mode of each sending-end DC line, the matching degree between the DC landing point and the receiving-end power grid section is evaluated, and an initial landing point scheme set for the receiving-end power grid is given, which may include: Based on the power shortage of each section of the receiving-end power grid, the full DC transmission power and operating mode of each sending-end DC line, determine the matching rules between each sending-end DC line and the power shortage of each section. Based on the matching rules between each sending-end DC line and the power gap of each region, all DC landing point schemes corresponding to each sending-end DC line and each region of the receiving-end power grid are given. Based on the matching rules between each sending-end DC line and the power gap of each zone, the power spatial matching degree between all sending-end DC lines and the power gap of each zone is determined. Based on the power spatial matching degree between all sending-end DC lines and the power gaps in each region, the schemes for each DC landing point of all sending-end DC lines are screened to provide an initial landing point scheme set for the receiving-end power grid.

[0039] The matching rules for each sending-end DC line and the power shortage in each region are determined, which may include: correcting the cumulative value of the power shortage in multiple regions based on the operating mode of the sending-end DC line, and giving the matching rules for each sending-end DC line and the power shortage in each region in combination with the corresponding full DC transmission power. Specifically, correcting the cumulative value of the power shortage in multiple regions based on the operating mode of the sending-end DC line includes: when the operating mode of the sending-end DC line is islanded, correcting the cumulative value of the power shortage in multiple regions based on the time-varying power output function of the new energy source in the islanded operating mode; in one application scenario, the time-varying power output function of the new energy source includes the wind power output function and the photovoltaic power output function; correspondingly, the correction of the cumulative value of the power shortage in multiple regions satisfies the following relationship: Δ k (t)=Δ k +α[P wind (t)-P pv [(t)], the cumulative value of the corrected power shortage across multiple zones is ΣΔ k (t), where Δ k The static power gap, Δ, is the regional power gap pre-matched with the sending-end DC line in islanded operation mode. k (t) represents the correction value for the regional power shortage, where is the dynamic power shortage, α is the fluctuation reduction factor, and its value ranges from 0.8 to 1.2. wind (t) is the wind power output function, P pv (t) represents the photovoltaic output function. When the sending-end DC line operates in grid-connected mode, its corresponding regional power gap remains unchanged, i.e., Δ k (t)=Δ k The matching rule between each sending-end DC line and the power shortage of each zone refers to the cumulative power shortage of multiple zones falling within the range of the corresponding DC transmission capacity (DC injection power) of the sending-end DC line. The DC transmission capacity range is determined by the DC transmission capacity of the sending-end DC line and a predetermined proportional coefficient, i.e., P. k,范围 =(1±a)P dk a is 1%~5%, P k,范围 Let P be the range of DC transmission capacity of the k-th sending-end DC line. dk Let be the DC power transmission capacity of the k-th sending-end DC line.

[0040] Based on the matching rules between each sending-end DC line and the power gap in each region, all DC landing point schemes corresponding to each sending-end DC line and each region of the receiving-end power grid are given. This can include: determining multiple region combinations that satisfy the matching rules for each sending-end DC line; forming a DC landing point scheme for the sending-end DC line based on the landing point corresponding to each region in each region combination; that is, one region combination corresponds to one DC landing scheme. For example... Figure 4 As shown, after determining the DC landing point scheme for each sending-end current line, the power spatial matching degree between all sending-end DC lines and the power gaps of each zone can be determined based on the matching rules between each sending-end DC line and the power gaps of each zone. Specifically, this includes: Choose one DC landing point scheme from each sending-end DC line and give multiple sets of DC landing point schemes; wherein, the set of DC landing point schemes includes one DC landing point scheme from each sending-end DC line; Determine the total power shortage of multiple zones corresponding to each DC landing scheme in each DC landing scheme set; Based on the total power gap of multiple zones corresponding to each DC landing point scheme, and combined with the DC transmission capacity of all sending-end DC lines, the power spatial matching degree is given, satisfying the following relationship:

[0041] In the formula, f1 is the power spatial matching degree, K(i) is the number of partitions in the i-th DC landing point scheme set, and P dij Let n be the DC transmission capacity of the j-th sending-end DC line in the i-th DC landing point scheme set, and n be the number of sending-end DC lines in the i-th DC landing point scheme set.

[0042] Based on the matching rules between each sending-end DC line and the power gap of each region, the power spatial matching degree between all sending-end DC lines and the power gap of each region is determined. This may further include: determining the total power gap of multiple regions corresponding to each DC landing point scheme in each set of DC landing point schemes; determining the fluctuation penalty coefficient based on the operating mode of the sending-end DC lines; and, based on the total power gap of multiple regions corresponding to each DC landing scheme, combining the fluctuation penalty coefficient and the DC transmission capacity of all sending-end DC lines, giving the power spatial matching degree, satisfying the following relationship:

[0043] In the formula, f1 is the power spatial matching degree, K(i) is the number of partitions in the i-th DC landing point scheme set, and P dijLet be the DC transmission capacity of the j-th sending-end DC line in the i-th DC landing point scheme set, n be the number of sending-end DC lines in the i-th DC landing point scheme set, and δ be the fluctuation penalty coefficient, with a value of 0.1~0.3. By adding a penalty term (the product of the derivative of the total power gap in all zones and the fluctuation penalty coefficient), the layout of DC landing points can be guided to avoid long-distance transfer paths. That is, the greater the gap change rate, the more frequent the power flow adjustment, increasing the evacuation pressure, and ultimately leading to a decrease in the power spatial matching degree.

[0044] This invention adheres to the principle of local power consumption while considering the impact of DC landing point schemes on the power balance of each region. The power of the sending-end DC line should prioritize regions with larger power injection deficits to avoid large-scale power transfer within the receiving-end grid and reduce the risk of power dissipation near the DC landing point. The power spatial matching degree is mainly measured by calculating the difference between the power space of the receiving-end grid in the planned DC landing point area and the DC injection power. A larger difference indicates a more superior DC landing point scheme, a larger power space in the DC landing point area, and consequently, less pressure on the receiving-end grid to dissipate DC power.

[0045] After determining the power spatial matching degree of each DC landing point scheme set, the DC landing point schemes for all sending-end DC lines can be screened based on the power spatial matching degree between all sending-end DC lines and the power gaps in each region, resulting in an initial landing point scheme set for the receiving-end power grid. Specifically, this includes: identifying and comparing all corresponding regions in each DC landing point scheme set to obtain a set of DC landing point schemes with identical regions; removing the sets of DC landing point schemes with identical regions to obtain the remaining set of DC landing point schemes and their power spatial matching degrees. After removing the sets of DC landing point schemes with identical regions, based on a preset matching degree threshold, the remaining sets of DC landing point schemes with values ​​less than the preset matching degree threshold can be removed, retaining the sets of DC landing point schemes with values ​​greater than or equal to the preset matching degree threshold and their power spatial matching degrees. The remaining set of DC landing point schemes after removing the preset matching degree threshold constitutes the initial landing point scheme set.

[0046] like Figure 5 As shown, voltage stability and fault risk assessments are performed on the initial set of landing point schemes, and an optimized set of landing point schemes that has been selected and updated is presented, including: Based on the operating mode of each sending-end DC line, determine the control strategy for each initial landing point scheme; Based on the control strategy, simulations are performed on each initial landing point scheme to provide a voltage-stable initial landing point scheme. Fault simulations were performed on the initial landing point schemes with stable voltage, and the initial landing point schemes with fault risk in the fault simulation were optimized to obtain the optimized landing point scheme set.

[0047] Among them, such as Figure 6 As shown, based on the control strategy, simulations are performed on each initial landing point scheme to provide a voltage-stable initial landing point scheme, which may include: Based on the control strategy, simulations are performed for each initial landing point scheme, and the voltage stiffness of all sending-end DC lines corresponding to each initial landing point scheme is given. The control strategy is determined by the operating mode: AC voltage control is used for simulation in islanded grid operation mode, and constant power control is used in grid-connected operation mode. Furthermore, PSCAD / EMTP simulations can be used to simulate multiple operating conditions (e.g., high / low power flow, renewable energy fluctuations). The voltage stiffness, which is the reciprocal of the coupling strength between reactive power injection and voltage change, is determined through simulation. Based on the voltage stiffness of all sending-end DC lines corresponding to each initial landing point scheme, determine the voltage support capability value of each initial landing point scheme. Based on the voltage support capability value of each initial landing point scheme, initial landing point schemes with a value greater than or equal to a preset capability threshold are selected; wherein, the preset capability threshold can be 0.5 to 0.7.

[0048] In one application scenario, based on the voltage stiffness of all sending-end DC lines corresponding to each initial landing point scheme, the voltage support capability value of each initial landing point scheme is determined, which may include: The average voltage stiffness value is determined based on the voltage stiffness of all sending-end DC lines corresponding to each initial landing point scheme. Based on the power space matching degree corresponding to the initial landing point scheme set, the average voltage stiffness value is scaled to give the voltage support capability value of the initial landing point scheme.

[0049] The voltage stiffness of all sending-end DC lines corresponding to each initial landing point scheme can form a voltage stiffness matrix. The average voltage stiffness value can be quickly calculated using this matrix. Specifically, the voltage stiffness matrix satisfies the following relationship:

[0050] In the formula, K is the voltage stiffness matrix, p is the number of initial landing point schemes, and K ij The voltage stiffness of the DC line at the j-th sending end of the i-th initial landing point scheme; The voltage support capability value satisfies the following relationship:

[0051] In the formula, f2 is the voltage support capability value, γ is the coordination coefficient, and its value ranges from 0.1 to 0.2. avg Let f be the mean of dynamic matching degree, A be the number of partitions corresponding to the i-th initial landing point scheme, and f be the mean of dynamic matching degree.1,i The power spatial matching degree corresponding to the i-th partition is calculated using f1, which is the power gap corrected by partitioning and the DC transmission capacity allocated to the corresponding DC landing point, M. avg Alternatively, it can be determined directly by the quotient (ratio) of the power space matching degree corresponding to the i-th initial landing point scheme and the total number of partitions.

[0052] Typically, in multi-infeed or multi-terminal DC transmission systems, the inverter stations at each DC landing point are coupled to each other through the receiving-end AC system, and the electrical distance between them is relatively short. Therefore, when the AC system experiences a severe fault or is weak, a commutation failure at one DC or one DC landing point inverter station often leads to consecutive commutation failures at multiple inverter stations, threatening the overall power supply reliability of the AC / DC hybrid system. This is especially true for large-capacity, long-distance DC transmission systems, where recovery after a fault is difficult and prone to significant power fluctuations; commutation failure or DC blocking can severely disrupt the safe and stable operation of the receiving-end grid. Based on this... Figure 7 As shown, after determining the initial landing point scheme for voltage stability, fault simulation can be performed on the initial landing point scheme for voltage stability, and the initial landing point schemes with fault risk in the fault simulation can be optimized to obtain the optimized landing point scheme set, which specifically includes: The initial landing point schemes selected are subjected to N-1 fault simulation to provide the DC power loss of the receiving end grid during the fault and the total external power received by the receiving end grid before the fault. Among them, the N-1 fault simulation is mainly used to simulate the three-phase short-circuit fault of the receiving end bus. That is, the selected initial landing point schemes are simulated to simulate the three-phase short-circuit fault of the receiving end bus through N-1 fault simulation. Based on the lost DC power and the total received external power, the severity of the DC fault is determined, satisfying the following relationship: f3=P los / P sum f3 is the severity value of the DC fault, P los To lose DC power, P sum This represents the total received external power. An initial landing point scheme with a DC fault severity value greater than a preset fault threshold is selected, and based on the matching rules between each sending-end DC line and the power gap in each zone, some DC landing points in the initial landing point scheme are divided; wherein, the preset fault threshold value is 0.1~0.3, preferably 0.2; Based on the initial landing point scheme after partitioning, and combined with the initial landing point scheme that is less than or equal to the preset fault threshold, an optimized landing point scheme set is given; wherein, the optimized landing point scheme set includes the initial landing point scheme after partitioning and the initial landing point scheme that is less than or equal to the preset fault threshold.

[0053] like Figure 8As shown, in practical application scenarios, an initial landing point scheme is selected where the severity value of the DC fault is greater than a preset fault threshold. Based on the matching rules between each sending-end DC line and the power gap in each zone, some DC landing points in the initial landing point scheme are divided, which may include: Select an initial landing point scheme where the severity value of the DC fault is greater than the preset fault threshold, and select a sending-end DC line with a corresponding DC landing point less than a predetermined number from the initial landing point scheme; wherein, the predetermined number can be 1, that is, select a sending-end DC line with only 1 DC landing point. Based on the severity level of the DC fault in the initial landing point scheme and the matching rules between each sending-end DC line and the power gap in each zone, the candidate zone group corresponding to each selected sending-end DC line is given. Based on the candidate partition group corresponding to each selected DC sending end line, determine the corresponding DC landing point scheme after partitioning. The initial landing point scheme after the division is given by integrating the DC landing point schemes of the divided DC lines and the corresponding DC landing point schemes of the sending-end DC lines with a DC landing point greater than or equal to a predetermined number. That is, during the division, only the sending-end DC lines with a DC landing point less than the predetermined number are re-determined, while the other sending-end DC lines remain unchanged. After the division, they are merged with the undivided sending-end DC lines to obtain the initial landing point scheme after the division.

[0054] Among them, such as Figure 9 As shown, based on the severity level of the DC fault in the initial landing point scheme and combined with the matching rules between each sending-end DC line and the power gap in each zone, the candidate zone groups corresponding to each selected sending-end DC line are given, including: Based on the severity level of the DC fault in the initial fault location scheme, the pre-defined number of DC fault locations for the selected sending-end DC line is given. The fault levels include Level 1, Level 2, and Level 3. The lower limit of Level 1 is equal to the preset fault threshold, the upper limit of Level 1 is the lower limit of Level 2, and the upper limit of Level 2 is the lower limit of Level 3. For example, when the preset fault threshold is 0.2, Levels 1, 2, and 3 can be 0.2~0.3, 0.3~0.4, and 0.4~1, respectively. Correspondingly, at Level 1, the pre-defined number of DC fault locations can be 2; at Level 2, 3; and at Level 3, 4. Based on the number of pre-divided DC landing points of the selected sending-end DC lines, and combined with the matching rules between each sending-end DC line and the power gap of each zone, the candidate zone group corresponding to each selected sending-end DC line is given; that is, the candidate zone group corresponding to each selected sending-end DC line satisfies the matching rules. For each candidate partition group, the electrical distance between multiple DC landing points is determined and compared with a preset distance threshold. Candidate partition groups with at least one electrical distance less than the preset distance threshold are eliminated. The electrical distance can be an impedance value, and the electrical distance between candidate DC landing points is calculated using a node impedance matrix. Specifically, the node impedance matrix can be obtained by building a detailed model of the receiving-end power grid using power system analysis software (such as PSASP, PSCAD / EMTP, MATLAB / Simulink), inputting parameters of components such as lines, transformers, and generators, and calculating the node impedance matrix. Determine the total electrical distance for each of the remaining candidate partition groups and sort them by size. Then, identify the candidate partition group with the largest total electrical distance. A larger total electrical distance helps prevent fault coupling, thereby improving voltage support capability.

[0055] like Figure 10 As shown, after determining the optimal landing point scheme set, a comprehensive evaluation can be performed on the optimal landing point scheme set of the receiving-end power grid based on the matching degree evaluation, voltage stability evaluation, and fault risk evaluation results. This evaluation will then yield the best optimal landing point scheme in the set, specifically including: Obtain the power spatial matching degree, voltage support capability value, and fault severity value of the optimized landing point scheme set, as well as the corresponding weight coefficients; The values ​​of power spatial matching degree, voltage support capability, and fault severity are standardized, and the standardized values ​​of power spatial matching degree, voltage support capability, and fault severity are given for each optimized landing point scheme. Based on the weighting coefficients corresponding to the standardized power spatial matching degree, voltage support capability value, and fault severity value of each optimized landing point scheme, a comprehensive evaluation index for each optimized landing point scheme is determined. Based on the ranking of comprehensive evaluation indicators, the DC full-power delivery scheme corresponding to the maximum comprehensive evaluation indicator is given.

[0056] In practical applications, the weighting coefficients for power spatial matching degree, voltage support capability, and fault severity can be determined using a binomial coefficient weighting method. When the number of indicators is even (2k), the weighting coefficients are:

[0057] When the number of indicators is odd (2k+1), the weighting coefficient is:

[0058] In the formula, all coefficients satisfy 0 < λk < 1, and Sum(Г) = 1, where Г is the weighting coefficient matrix. Correspondingly, k = 1, meaning there are three indices. Therefore, the weighting coefficients for power spatial matching degree, voltage support capability value, and fault severity value are 0.25, 0.5, and 0.25, respectively. Furthermore, in DC landing point planning, the importance order of the indices for power spatial matching degree, voltage support capability value, and fault severity value satisfies: f2 > f1 ≈ f3. Therefore, voltage stability corresponding to the voltage support capability value is crucial for AC / DC systems, and the weighting coefficients determined by the binomial coefficient weighting method can well meet the requirements of indicator importance. In addition, the weighting coefficients for power spatial matching degree, voltage support capability value, and fault severity value can also be determined using expert methods, relative comparison methods, etc.

[0059] Standardizing the values ​​of power spatial matching degree, voltage support capability, and fault severity can satisfy the following relationships:

[0060] In the formula, Let f1(i), f2(i), and f3(i) be the power spatial matching degree, voltage support capability, and fault severity value of the i-th optimized landing scheme after standardization, respectively. Let f1(i), f2(i), and f3(i) be the power spatial matching degree, voltage support capability, and fault severity value of the i-th optimized landing scheme before standardization, respectively. Let maxf1 and minf1 be the maximum and minimum power spatial matching degree values ​​of the optimized landing schemes, respectively. Let maxf2 and minf2 be the maximum and minimum voltage support capability values ​​of the optimized landing schemes, respectively. Let maxf3 and minf3 be the maximum and minimum fault severity values ​​of the optimized landing schemes, respectively.

[0061] Correspondingly, the comprehensive evaluation indicators satisfy the following relationship:

[0062] In the formula, S is the comprehensive evaluation index, and ε1, ε2, and ε3 are the weighting coefficients corresponding to the power spatial matching degree, voltage support capability value, and fault severity value, respectively.

[0063] In practical applications, the step structure of the DC landing point determination method of this invention is as follows: (1) First, consider the impact of DC on power flow evacuation. The goal is to achieve the best power space matching degree of DC landing point layout, ensure safe power flow evacuation, and feed in in layers and zones.

[0064] (2) Considering the influence of DC reactive power control mode, the voltage stiffness of the two control modes of constant reactive power and constant AC voltage are compared to select the landing point; (3) Considering the impact of the N-1 fault in the DC system, if the power loss due to the N-1 fault is greater than the specified value, it indicates that the fault at the DC landing point is more serious. It is advisable to split the single landing point into multiple landing points for connection.

[0065] like Figure 11 As shown, the present invention also provides a device for determining the DC landing point of a multi-DC feed-in receiving-end power grid, employing the above-described method for determining the DC landing point of a multi-DC feed-in receiving-end power grid. The device includes: The data acquisition module is used to acquire the power gap of each section of the receiving-end power grid, as well as the full DC transmission power and operating mode of each sending-end DC line; The initial scheme determination module is used to evaluate the matching degree between the DC landing point and the receiving-end power grid section based on the power gap of each section of the receiving-end power grid, the full DC transmission power and operating mode of each sending-end DC line, and to give the initial landing point scheme set of the receiving-end power grid. The scheme optimization module is used to evaluate the voltage stability and fault risk of the initial landing point scheme set, and provide a filtered and updated optimized landing point scheme set. The scheme selection module is used to comprehensively evaluate the set of optimal landing schemes for the receiving-end power grid based on the results of matching degree assessment, voltage stability assessment, and fault risk assessment, and to provide the best optimal landing scheme in the set of optimal landing schemes.

[0066] Furthermore, the initial scheme determination module is used for: Based on the power shortage of each section of the receiving-end power grid, the full DC transmission power and operating mode of each sending-end DC line, determine the matching rules between each sending-end DC line and the power shortage of each section. Based on the matching rules between each sending-end DC line and the power gap of each region, all DC landing point schemes corresponding to each sending-end DC line and each region of the receiving-end power grid are given. Based on the matching rules between each sending-end DC line and the power gap of each zone, the power spatial matching degree between all sending-end DC lines and the power gap of each zone is determined. Based on the power spatial matching degree between all sending-end DC lines and the power gaps in each region, the schemes for each DC landing point of all sending-end DC lines are screened to provide an initial landing point scheme set for the receiving-end power grid.

[0067] Furthermore, the initial scheme determination module is used for: Based on the operating mode of the sending-end DC line, the cumulative value of the power shortage in multiple zones is corrected, and combined with the corresponding full DC transmission power, the matching rules between each sending-end DC line and the power shortage in each zone are given.

[0068] Furthermore, the initial scheme determination module is also used for: Choose one DC landing point scheme from each sending-end DC line and give a set of multiple DC landing point schemes; Determine the total power shortage of multiple zones corresponding to each DC landing scheme in each DC landing scheme set; Based on the total power gap of multiple zones corresponding to each DC landing point scheme, and combined with the DC transmission capacity of all sending-end DC lines, the power spatial matching degree is given.

[0069] Furthermore, the solution optimization module is used for: Based on the operating mode of each sending-end DC line, determine the control strategy for each initial landing point scheme; Based on the control strategy, simulations are performed on each initial landing point scheme to provide a voltage-stable initial landing point scheme. Fault simulations were performed on the initial landing point schemes with stable voltage, and the initial landing point schemes with fault risk in the fault simulation were optimized to obtain the optimized landing point scheme set.

[0070] Furthermore, the solution optimization module is used for: Based on the control strategy, simulations are performed on each initial landing point scheme, and the voltage stiffness of all sending-end DC lines corresponding to each initial landing point scheme is given. Based on the voltage stiffness of all sending-end DC lines corresponding to each initial landing point scheme, determine the voltage support capability value of each initial landing point scheme. Based on the voltage support capability value of each initial landing point scheme, initial landing point schemes that are greater than or equal to the preset capability threshold are selected.

[0071] Furthermore, the solution optimization module is used for: The average voltage stiffness value is determined based on the voltage stiffness of all sending-end DC lines corresponding to each initial landing point scheme. Based on the power space matching degree corresponding to the initial landing point scheme set, the average voltage stiffness value is scaled to give the voltage support capability value of the initial landing point scheme.

[0072] Furthermore, the solution optimization module is also used for: An N-1 fault simulation was performed on the selected initial landing point scheme to give the DC power loss of the receiving end grid during the fault and the total external power received by the receiving end grid before the fault. The severity value of the DC fault is determined based on the lost DC power and the total received external power. An initial landing point scheme with a DC fault severity value greater than a preset fault threshold is selected, and based on the matching rules between each sending-end DC line and the power gap in each zone, some DC landing points in the initial landing point scheme are divided. Based on the initial landing point scheme after partitioning, and combined with the initial landing point scheme that is less than or equal to the preset fault threshold, an optimized landing point scheme set is given.

[0073] Furthermore, the solution optimization module is used for: Select an initial landing point scheme with a DC fault severity value greater than a preset fault threshold, and select a corresponding DC landing point of less than a predetermined number of sending-end DC lines from the initial landing point scheme. Based on the severity level of the DC fault in the initial landing point scheme and the matching rules between each sending-end DC line and the power gap in each zone, the candidate zone group corresponding to each selected sending-end DC line is given. Based on the candidate partition group corresponding to each selected DC sending end line, determine the corresponding DC landing point scheme after partitioning. The integrated and divided DC landing point schemes and the DC landing point schemes corresponding to the sending-end DC lines with a DC landing point greater than or equal to a predetermined number are given, and the initial landing point scheme after the division is presented.

[0074] Furthermore, the solution optimization module is also used for: Based on the severity level of the DC fault in the initial landing point scheme, the number of pre-defined DC landing points for the selected sending-end DC line is given. Based on the number of pre-divided DC landing points of the selected sending-end DC lines, and combined with the matching rules between each sending-end DC line and the power gap of each zone, the candidate zone group corresponding to each selected sending-end DC line is given. For each candidate partition group, the electrical distance to multiple DC landing points is determined and compared with a preset distance threshold. Candidate partition groups with at least one electrical distance less than the preset distance threshold are eliminated. Determine the total electrical distance of each of the remaining candidate partition groups and sort them by size, and give the candidate partition group with the largest total electrical distance.

[0075] Furthermore, the solution selection module is also used for: Obtain the power spatial matching degree, voltage support capability value, and fault severity value of the optimized landing point scheme set, as well as the corresponding weight coefficients; The values ​​of power spatial matching degree, voltage support capability, and fault severity are standardized, and the standardized values ​​of power spatial matching degree, voltage support capability, and fault severity are given for each optimized landing point scheme. Based on the weighting coefficients corresponding to the standardized power spatial matching degree, voltage support capability value, and fault severity value of each optimized landing point scheme, a comprehensive evaluation index for each optimized landing point scheme is determined. Based on the ranking of comprehensive evaluation indicators, the DC full-power delivery scheme corresponding to the maximum comprehensive evaluation indicator is given.

[0076] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its spirit and scope. Thus, if these modifications and modifications of the invention fall within the scope of the claims and their equivalents, the invention is also intended to include these modifications and modifications.

Claims

1. A method for determining the DC landing point of a multi-DC feed-in receiving-end power grid, characterized in that, include: Obtain the power shortage of each section of the receiving-end power grid, as well as the full DC transmission power and operating mode of each sending-end DC line; Based on the power shortage of each section of the receiving-end power grid, the full DC transmission power and operating mode of each sending-end DC line, the matching degree between the DC landing point and the receiving-end power grid section is evaluated, and an initial landing point scheme set for the receiving-end power grid is given. Voltage stability and fault risk assessments are performed on the initial set of landing point schemes, and a set of optimized landing point schemes is provided after screening and updating. Based on the results of matching degree assessment, voltage stability assessment, and fault risk assessment, a comprehensive evaluation of the set of optimal landing point schemes for the receiving-end power grid is conducted, and the best optimal landing point scheme in the set of optimal landing point schemes is given.

2. The method for determining the DC landing point as described in claim 1, characterized in that, Based on the power shortage in each region of the receiving-end power grid, the full DC transmission capacity and operating mode of each sending-end DC line, the matching degree between the DC landing point and the receiving-end power grid region is evaluated, and an initial landing point scheme set for the receiving-end power grid is given, including: Based on the power shortage of each section of the receiving-end power grid, the full DC transmission power and operating mode of each sending-end DC line, determine the matching rules between each sending-end DC line and the power shortage of each section. Based on the matching rules between each sending-end DC line and the power gap of each region, all DC landing point schemes corresponding to each sending-end DC line and each region of the receiving-end power grid are given. Based on the matching rules between each sending-end DC line and the power gap of each zone, the power spatial matching degree between all sending-end DC lines and the power gap of each zone is determined. Based on the power spatial matching degree between all sending-end DC lines and the power gaps in each region, the schemes for each DC landing point of all sending-end DC lines are screened to provide an initial landing point scheme set for the receiving-end power grid.

3. The method for determining the DC landing point as described in claim 2, characterized in that, The matching rules between each sending-end DC line and the power shortage in each zone are determined, including: Based on the operating mode of the sending-end DC line, the cumulative value of the power shortage in multiple zones is corrected, and combined with the corresponding full DC transmission power, the matching rules between each sending-end DC line and the power shortage in each zone are given.

4. The method for determining the DC landing point as described in claim 2, characterized in that, Based on the matching rules between each sending-end DC line and the power gap in each zone, the power spatial matching degree between all sending-end DC lines and the power gap in each zone is determined, including: Choose one DC landing point scheme from each sending-end DC line and give a set of multiple DC landing point schemes; Determine the total power shortage of multiple zones corresponding to each DC landing scheme in each DC landing scheme set; Based on the total power gap of multiple zones corresponding to each DC landing point scheme, and combined with the DC transmission capacity of all sending-end DC lines, the power spatial matching degree is given.

5. The method for determining the DC landing point as described in claim 4, characterized in that, Voltage stability and fault risk assessments are performed on the initial set of landing point schemes, and a filtered and updated set of optimized landing point schemes is provided, including: Based on the operating mode of each sending-end DC line, determine the control strategy for each initial landing point scheme; Based on the control strategy, simulations are performed on each initial landing point scheme to provide a voltage-stable initial landing point scheme. Fault simulations were performed on the initial landing point schemes with stable voltage, and the initial landing point schemes with fault risk in the fault simulation were optimized to obtain the optimized landing point scheme set.

6. The method for determining the DC landing point as described in claim 5, characterized in that, Based on the control strategy, simulations are performed for each initial landing point scheme, and voltage-stable initial landing point schemes are presented, including: Based on the control strategy, simulations are performed on each initial landing point scheme, and the voltage stiffness of all sending-end DC lines corresponding to each initial landing point scheme is given. Based on the voltage stiffness of all sending-end DC lines corresponding to each initial landing point scheme, determine the voltage support capability value of each initial landing point scheme. Based on the voltage support capability value of each initial landing point scheme, initial landing point schemes that are greater than or equal to the preset capability threshold are selected.

7. The method for determining the DC landing point as described in claim 6, characterized in that, Based on the voltage stiffness of all sending-end DC lines corresponding to each initial landing point scheme, the voltage support capability value of each initial landing point scheme is determined, including: The average voltage stiffness value is determined based on the voltage stiffness of all sending-end DC lines corresponding to each initial landing point scheme. Based on the power space matching degree corresponding to the initial landing point scheme set, the average voltage stiffness value is scaled to give the voltage support capability value of the initial landing point scheme.

8. The method for determining the DC landing point as described in claim 6, characterized in that, Fault simulations were performed on the initial landing point schemes with stable voltage, and the initial landing point schemes with fault risk in the fault simulation were optimized to obtain a set of optimized landing point schemes, including: An N-1 fault simulation was performed on the selected initial landing point scheme to give the DC power loss of the receiving end grid during the fault and the total external power received by the receiving end grid before the fault. The severity value of the DC fault is determined based on the lost DC power and the total received external power. An initial landing point scheme with a DC fault severity value greater than a preset fault threshold is selected, and based on the matching rules between each sending-end DC line and the power gap in each zone, some DC landing points in the initial landing point scheme are divided. Based on the initial landing point scheme after partitioning, and combined with the initial landing point scheme that is less than or equal to the preset fault threshold, an optimized landing point scheme set is given.

9. The method for determining the DC landing point as described in claim 8, characterized in that, An initial landing point scheme is selected based on the DC fault severity value being greater than a preset fault threshold. Then, based on the matching rules between each sending-end DC line and the power gap in each zone, some DC landing points in the initial landing point scheme are divided, including: Select an initial landing point scheme with a DC fault severity value greater than a preset fault threshold, and select a corresponding DC landing point of less than a predetermined number of sending-end DC lines from the initial landing point scheme. Based on the severity level of the DC fault in the initial landing point scheme and the matching rules between each sending-end DC line and the power gap in each zone, the candidate zone group corresponding to each selected sending-end DC line is given. Based on the candidate partition group corresponding to each selected DC sending end line, determine the corresponding DC landing point scheme after partitioning. The integrated and divided DC landing point schemes and the DC landing point schemes corresponding to the sending-end DC lines with a DC landing point greater than or equal to a predetermined number are given, and the initial landing point scheme after the division is presented.

10. The method for determining the DC landing point as described in claim 9, characterized in that, Based on the severity level of the DC fault according to the initial landing point scheme, and combined with the matching rules between each sending-end DC line and the power gap in each zone, the candidate zone groups corresponding to each selected sending-end DC line are given, including: Based on the severity level of the DC fault in the initial landing point scheme, the number of pre-defined DC landing points for the selected sending-end DC line is given. Based on the number of pre-divided DC landing points of the selected sending-end DC lines, and combined with the matching rules between each sending-end DC line and the power gap of each zone, the candidate zone group corresponding to each selected sending-end DC line is given. For each candidate partition group, the electrical distance to multiple DC landing points is determined and compared with a preset distance threshold. Candidate partition groups with at least one electrical distance less than the preset distance threshold are eliminated. Determine the total electrical distance of each of the remaining candidate partition groups and sort them by size, and give the candidate partition group with the largest total electrical distance.

11. The method for determining the DC landing point as described in any one of claims 1 to 10, characterized in that, Based on the results of matching degree assessment, voltage stability assessment, and fault risk assessment, a comprehensive evaluation of the optimal landing point scheme set for the receiving-end power grid is conducted, and the best optimal landing point scheme in the optimal landing point scheme set is given, including: Obtain the weighting coefficients of the power spatial matching degree, voltage support capability value, and fault severity value corresponding to the optimized landing point scheme set; The values ​​of power spatial matching degree, voltage support capability, and fault severity are standardized, and the standardized values ​​of power spatial matching degree, voltage support capability, and fault severity are given for each optimized landing point scheme. Based on the weighting coefficients corresponding to the standardized power spatial matching degree, voltage support capability value, and fault severity value of each optimized landing point scheme, a comprehensive evaluation index for each optimized landing point scheme is determined. Based on the ranking of comprehensive evaluation indicators, the DC full-power delivery scheme corresponding to the maximum comprehensive evaluation indicator is given.

12. A device for determining the DC landing point of a multi-DC feed-in receiving-end power grid, characterized in that, The apparatus employing the DC landing point determination method for multiple DC feed-in receiving-end power grids as described in any one of claims 1 to 11 includes: The data acquisition module is used to acquire the power gap of each section of the receiving-end power grid, as well as the full DC transmission power and operating mode of each sending-end DC line; The initial scheme determination module is used to evaluate the matching degree between the DC landing point and the receiving-end power grid section based on the power gap of each section of the receiving-end power grid, the full DC transmission power and operating mode of each sending-end DC line, and to give the initial landing point scheme set of the receiving-end power grid. The scheme optimization module is used to evaluate the voltage stability and fault risk of the initial landing point scheme set, and provide a filtered and updated optimized landing point scheme set. The scheme selection module is used to comprehensively evaluate the set of optimal landing schemes for the receiving-end power grid based on the results of matching degree assessment, voltage stability assessment, and fault risk assessment, and to provide the best optimal landing scheme in the set of optimal landing schemes.

13. The DC landing point determination device as claimed in claim 12, characterized in that, The initial scheme determination module is used for: Based on the power shortage of each section of the receiving-end power grid, the full DC transmission power and operating mode of each sending-end DC line, determine the matching rules between each sending-end DC line and the power shortage of each section. Based on the matching rules between each sending-end DC line and the power gap of each region, all DC landing point schemes corresponding to each sending-end DC line and each region of the receiving-end power grid are given. Based on the matching rules between each sending-end DC line and the power gap of each zone, the power spatial matching degree between all sending-end DC lines and the power gap of each zone is determined. Based on the power spatial matching degree between all sending-end DC lines and the power gaps in each region, the schemes for each DC landing point of all sending-end DC lines are screened to provide an initial landing point scheme set for the receiving-end power grid.

14. The DC landing point determination device as claimed in claim 12, characterized in that, The solution optimization module is used for: Based on the operating mode of each sending-end DC line, determine the control strategy for each initial landing point scheme; Based on the control strategy, simulations are performed on each initial landing point scheme to provide a voltage-stable initial landing point scheme. Fault simulations were performed on the initial landing point schemes with stable voltage, and the initial landing point schemes with fault risk in the fault simulation were optimized to obtain the optimized landing point scheme set.

15. The DC landing point determination device as claimed in claim 12, characterized in that, The solution selection module is also used for: Obtain the power spatial matching degree, voltage support capability value, and fault severity value of the optimized landing point scheme set, as well as the corresponding weight coefficients; The values ​​of power spatial matching degree, voltage support capability, and fault severity are standardized, and the standardized values ​​of power spatial matching degree, voltage support capability, and fault severity are given for each optimized landing point scheme. Based on the weighting coefficients corresponding to the standardized power spatial matching degree, voltage support capability value, and fault severity value of each optimized landing point scheme, a comprehensive evaluation index for each optimized landing point scheme is determined. Based on the ranking of comprehensive evaluation indicators, the DC full-power delivery scheme corresponding to the maximum comprehensive evaluation indicator is given.

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