High-capacity trans-regional extra-high voltage direct current receiving end grid-connected voltage grade selection method and system

Abstract

The embodiment of the invention provides a high-capacity trans-regional extra-high voltage direct current receiving end grid-connected voltage grade selection method and system. The method comprises the steps of obtaining input parameters of a trans-regional extra-high voltage direct current power transmission system; based on the input parameters, an optimization model is constructed, and the optimization model comprises a target function with the comprehensive cost minimization as the core; and solving the optimization model by adopting a mathematical optimization algorithm to obtain and output a recommended grid-connected voltage grade, a power distribution proportion of each consumption area and a net rack upgrading capacity scheme. According to the technical scheme provided by the invention, comprehensive optimization of the voltage grade, the evacuation path and the investment benefit can be realized under multiple factors and multiple constraints.

Description

Technical Field

[0001] This invention belongs to the field of power system technology, and in particular relates to a method and system for selecting the receiving-end grid connection voltage level of large-capacity inter-regional ultra-high voltage direct current transmission lines. Background Technology

[0002] In the planning and construction of inter-regional ultra-high voltage direct current (UHVDC) transmission systems, determining the grid connection voltage level of the converter station receiving end is one of the key technical aspects. Traditional methods typically rely on engineering experience or single economic indicators, such as empirically determining whether to connect to a 500kV or 1000kV AC grid based on the converter station's capacity or geographical location. While this empirical approach is feasible for simple grid structures or small converter capacities, it lacks a systematic quantitative basis for decision-making in complex situations such as multiple infeeds, multiple receiving ends in different regions, and large-capacity DC parallel operation.

[0003] Currently, commonly used evaluation methods include: static verification method based on power flow analysis and short-circuit ratio calculation, simulation comparison method based on voltage stability margin, and quantitative evaluation method with the goal of minimizing economic cost.

[0004] However, these methods often have the following drawbacks:

[0005] (1) Single indicator: Only economic efficiency or short-circuit ratio is used as the main judgment basis, ignoring the constraints of system absorption path, supply and demand balance at the receiving end and cross-regional power transmission pattern on grid connection level.

[0006] (2) Insufficient regional coordination: In the case of multiple converter stations operating in parallel or multiple feeders at the receiving end, the impact of grid connection level selection on the system short-circuit ratio and mutual electromagnetic coupling was not considered.

[0007] (3) Lack of quantitative models: Most methods rely on human experience and simulation comparison, and lack quantifiable and solvable mathematical optimization models.

[0008] (4) Ignoring construction constraints: failing to comprehensively consider engineering constraints such as tight corridors and limited access in densely populated urban areas.

[0009] Existing technologies only consider a single technical indicator (such as short-circuit ratio or investment cost) and fail to incorporate multiple factors such as power consumption direction, receiving-end grid carrying capacity, renovation investment, and corridor construction constraints into the same framework, making it difficult to form a globally optimal decision. Summary of the Invention

[0010] The method and system for selecting the grid-connected voltage level of large-capacity inter-regional ultra-high voltage direct current transmission lines provided in this application can achieve the comprehensive optimization of voltage level, evacuation route and investment benefits under multiple factors and constraints.

[0011] In a first aspect, embodiments of this application provide a method for selecting the grid connection voltage level of a large-capacity inter-regional ultra-high voltage direct current (UHVDC) receiver, including:

[0012] Obtain the input parameters of the inter-regional ultra-high voltage direct current transmission system;

[0013] Based on the input parameters, an optimization model is constructed, which includes an objective function with the core objective of minimizing the overall cost.

[0014] The optimization model is solved using a mathematical optimization algorithm to obtain and output the recommended grid connection voltage level, the power allocation ratio of each absorption area, and the grid upgrade capacity scheme.

[0015] In one alternative implementation, the input parameters include rated DC output, maximum absorbable power of the target absorption area, capacity of the receiving-end grid, line corridor constraints, and short-circuit ratio data.

[0016] In one alternative implementation, the total cost includes the cost of converter station construction, the investment cost of grid upgrade, and the cost of new line construction.

[0017] In one alternative implementation, the objective function of the optimization model further includes a short-circuit ratio deficiency penalty term and an unabsorbed power penalty term.

[0018] In one alternative implementation, the constraints of the optimization model include power balance constraints, regional absorption capacity constraints, grid dispersal capacity constraints, line corridor constraints, and short-circuit ratio safety constraints.

[0019] In one alternative implementation, when constructing the optimization model, multiple power grid operation scenarios are defined, and probability weights are assigned to each power grid operation scenario; the objective function of the optimization model is to minimize the weighted comprehensive cost of all power grid operation scenarios.

[0020] In one alternative implementation, the mathematical optimization algorithm is a mixed-integer linear programming algorithm or a multi-objective evolutionary algorithm.

[0021] In one alternative implementation, it further includes:

[0022] Based on the recommended output, power flow simulation and short-circuit simulation are performed to verify the system's safety margin.

[0023] Secondly, embodiments of this application provide a large-capacity inter-regional ultra-high voltage direct current receiving-end grid connection voltage level selection system, including:

[0024] The data acquisition module is used to acquire the input parameters of the inter-regional ultra-high voltage direct current transmission system.

[0025] The optimization model building module is used to build an optimization model based on the input parameters. The optimization model includes an objective function with the core objective of minimizing the overall cost.

[0026] The output module is used to solve the optimization model using mathematical optimization algorithms, obtain the recommended grid-connected voltage level, the power allocation ratio of each absorption area, and the grid upgrade capacity scheme, and output them.

[0027] Thirdly, embodiments of this application provide an electronic device, including a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, it implements the method provided in embodiments of this application.

[0028] Fourthly, embodiments of this application provide a computer-readable storage medium, characterized in that it stores a computer program thereon, which, when executed in a computer, causes the computer to perform the method provided in embodiments of this application.

[0029] The technical solution provided in this application has the following beneficial effects:

[0030] This invention constructs an optimization model with the objective function of minimizing the comprehensive cost throughout the entire life cycle, and introduces a penalty term representing system safety risks. It coordinates and balances traditionally separate considerations such as short-circuit ratio safety margin, grid absorption path, grid carrying capacity limit, line corridor constraints, and various investment costs. Using mathematical optimization algorithms such as mixed integer programming, it automatically solves the model, which includes multiple constraints such as power balance, evacuation capacity, and short-circuit ratio safety. This realizes the transformation from qualitative experience judgment to quantitative optimization decision-making, improving the scientific nature and repeatability of decision-making. It can automatically generate planning schemes that achieve the optimal balance between investment costs and system safety under complex multi-constraint conditions. Finally, the model has good scalability and can cope with the uncertainty of future operation modes through multi-scenario weighted analysis, providing robust and globally optimized decision support for the planning of complex receiving-end power grids with multiple DC feeds. Attached Figure Description

[0031] Figure 1 This is a flowchart illustrating the method for selecting the grid connection voltage level of a large-capacity inter-regional ultra-high voltage direct current transmission line provided in this application embodiment;

[0032] Figure 2 This is a schematic diagram of the structure of the large-capacity inter-regional ultra-high voltage direct current receiving-end grid connection voltage level selection system provided in the embodiments of this application. Detailed Implementation

[0033] The present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0034] This application provides a method for selecting the grid connection voltage level of large-capacity inter-regional ultra-high voltage direct current (UHVDC) receivers. Figure 1 This is a flowchart illustrating the method for selecting the grid connection voltage level of a large-capacity inter-regional ultra-high voltage direct current receiving end provided in an embodiment of this application. The method can be executed by a large-capacity inter-regional ultra-high voltage direct current receiving end grid connection voltage level selection system. The system can be implemented by software and / or hardware and can be configured in electronic devices such as computers.

[0035] like Figure 1 As shown, the technical solution provided in this application includes the following steps:

[0036] S110. Obtain the input parameters of the inter-regional ultra-high voltage direct current transmission system.

[0037] The input parameters include:

[0038] DC rated output P DC , refers to the rated transmission power of the planned UHVDC transmission system, that is, the total power that needs to be absorbed by the receiving-end grid, and is one of the core inputs in the optimization model;

[0039] The target absorption area set J refers to the set of geographical or network areas in the receiving-end power grid that may accept the DC power. For example, it may be the power supply area of ​​different provincial grids, load centers or specific substations.

[0040] Maximum absorbable power D in each target absorption area j For each region j in set J, it is necessary to obtain the maximum additional power that it can safely withstand under the current network structure. This parameter reflects the region's own load demand and network acceptance capacity.

[0041] The set of optional grid-connected voltage levels I refers to the technically feasible grid-connected voltage level options for the AC side of the receiving-end converter station, such as 500, 1000, 220kV, etc. This set defines the optional scheme space of the optimization model.

[0042] Evacuation capacity U of the grid structure at each voltage level grid,v For each voltage level v in the set, it is necessary to assess the remaining transmission capacity of the existing receiving-end AC grid at that voltage level that can be used to accommodate DC power or the channel capacity that can be quickly built.

[0043] Existing converter station set K and short-circuit capacity S of each converter station k Collect information on existing, especially nearby, converter stations or high-power sources in the receiving-end power grid, and use their short-circuit capacity to calculate the equivalent short-circuit ratio.

[0044] Power transmission distance d j, refers to the expected transmission line distance from the planned receiving-end converter station site to the junction point or hub substation of each target consumption area j. This parameter directly affects the line construction cost.

[0045] Line corridor constraints , refers to the maximum number of newly built power transmission channels that each target absorption area j can provide due to factors such as geographical environment, urban planning, and ecological protection;

[0046] Short-circuit ratio data, mainly including the calculation of the equivalent short-circuit ratio (SCR). eff The required data, such as the short-circuit capacity S of the existing system mentioned above. k Grid impedance Z grid,v And so on, as well as the minimum permissible short-circuit ratio (SCR) required for the safe operation of the system. min .

[0047] S120. Based on the input parameters, construct an optimization model, which includes an objective function with the core objective of minimizing overall cost.

[0048] In some embodiments, the objective function is the direction pursued by the optimization model. In this embodiment, the core objective is to minimize the overall cost over the entire life cycle, and a penalty term is introduced to ensure system safety, achieving a balance between economy and safety.

[0049] The mathematical expression for the objective function is as follows:

[0050] ;

[0051] ;

[0052] ;

[0053] ;

[0054] Where Z represents the overall objective function, which represents the comprehensive index to be minimized; α, β, and γ represent weighting coefficients used to balance the relative importance between economic costs and safety penalties; and C... cont x represents the construction cost of the converter station. v It is a binary decision variable, representing whether to choose voltage level v; the value is 1 if voltage level v is chosen, and 0 otherwise. C represents the cost required to construct a converter station with a voltage level of V. upgrade This represents the investment cost for network upgrades, where m represents a network node or line, and u represents the network upgrade cost. m For continuous decision variables, represents the upgrade capacity at a network node or line m. This represents the unit capacity upgrade cost for a network node or line m. d represents the cost of constructing the new line.j p represents the power transmission distance from the converter station to the target absorption area j. j Let be a continuous decision variable, representing the power allocated to the target absorption region j. This represents the construction cost per unit length and unit capacity of the power line. This represents a penalty term for unabsorbed power. When DC power cannot be completely absorbed due to grid constraints, this penalty term increases, forcing the model to seek a solution that can completely absorb the DC output. This represents a penalty term for insufficient short-circuit ratios. When the calculated equivalent short-circuit ratio is lower than the safety threshold, this penalty term will increase significantly, thereby ensuring that the recommended grid connection scheme can meet the requirements for stable system operation. This objective function comprehensively considers the costs of AC-side access to the converter station, grid reinforcement, and line construction, while maintaining system safety margins through the penalty term.

[0055] In some embodiments, the constraints of the optimization model include power balance constraints, regional absorption capacity constraints, grid dispersal capacity constraints, line corridor constraints, and short-circuit ratio safety constraints.

[0056] Power balance constraints:

[0057] ;

[0058] This constraint ensures that the total power P delivered by the ultra-high voltage direct current system is DC All of them must be allocated to one or more target disposal areas without omission.

[0059] Regional absorption capacity constraints:

[0060] ;

[0061] Among them, M j This represents the set of grid-connected equipment that affects the absorption capacity of the target absorption area j. For each absorption area j, the power p supplied to that area is... j It cannot exceed its current maximum absorbable capacity D j This constraint, combined with the increased capacity from potential grid upgrades, prevents the injection of excessive power into a region, thus avoiding overload.

[0062] Space frame evacuation capacity constraints:

[0063] ;

[0064] Among them, the receiving-end network structure for different voltage levels has a capacity limit; if the limit is exceeded, an upgrade variable u needs to be added. m For the receiving-end grid structure at the selected voltage level v, the total power allocated to all absorption areas (i.e., the total DC power) cannot exceed the current maximum evacuation capacity U of the receiving-end grid structure at that voltage level.grid,v Combined with the additional capacity provided by the grid upgrade, this ensures the smooth operation of the entire transmission channel.

[0065] Corridor constraints:

[0066] ;

[0067] This is an engineering physical constraint that limits the number of new transmission line corridors (n) allowed for each absorption area (j). j An upper limit was set. .

[0068] Short-circuit ratio safety constraints:

[0069] ;

[0070] Among these, the constraint is a key power grid security and stability constraint, which requires the final scheme to calculate the equivalent short-circuit ratio (SCR) at the grid connection point. eff The system's safety threshold (SCR) must be greater than or equal to the minimum threshold required for safe system operation. min The equivalent short-circuit ratio is the ratio of the short-circuit capacity at the grid connection point to the rated DC power, and its calculation depends on the selected voltage level (via x). v (Reflection), system short-circuit capacity (S) k ) and load distribution (D j Factors such as ( ).

[0071] Furthermore, the short-circuit ratio safety constraint is determined through power flow / short-circuit simulation or empirical formulas, and can be approximately expressed as:

[0072] ;

[0073] ;

[0074] The short-circuit ratio is characterized by the ratio of the equivalent short-circuit capacity at the grid connection point to the rated DC power. Therefore, the short-circuit ratio is essentially the ratio between the "grid's ability to resist disturbances" and the "scale of the disturbance source (DC system)". A higher ratio indicates a more robust grid and a more stable system after DC connection. This refers to the equivalent short-circuit capacity at the grid connection point under the selected voltage level v, which incorporates the grid impedance Z. grid,v and all power supplies S k The impact reflects the "strength" or "support capacity" of the power grid at that point.

[0075] In some embodiments, when considering different power grid operation scenarios (such as high load, low load, and high wind and solar power output scenarios), a scenario set S is defined, with different parameters (load D, grid capacity U, and distance constraints) for each scenario. Probability weights are assigned to each power grid operation scenario; the objective function of the optimization model is to minimize the weighted comprehensive cost of all power grid operation scenarios.

[0076] ;

[0077] Where s represents the s-th defined scenario, π s Let Z be the probability weight of the s-th scenario, representing the likelihood or importance of that scenario occurring in the future. It can be determined based on historical data statistical analysis or expert prediction. The sum of all probability weights should be 1. (s) This represents the objective function value under a specific scenario s. For each scenario s, the parameters corresponding to that scenario (such as the load level D, available grid capacity U, and power transmission distance limitations) need to be substituted into the optimization model constructed in S120 to calculate an independent comprehensive cost Z. Therefore, Z (s) This measures the performance of the planned scheme under scenario s. This method yields a grid-connected voltage selection scheme with strong robustness under uncertain conditions.

[0078] The essence of this formula is to find the minimum expected cost of the planning scheme. It no longer pursues the absolute optimality of the scheme under the "typical approach," but rather guides the optimization algorithm to find a scheme that performs best in a weighted average sense across all possible scenarios. The algorithm will tend to choose a scheme that has a low cost in high-probability scenarios, while in low-probability but extreme scenarios (such as high security risks), it will not perform extremely poorly due to the existence of a penalty term.

[0079] S130. The optimization model is solved using a mathematical optimization algorithm to obtain and output the recommended grid connection voltage level, the power allocation ratio of each absorption area, and the grid upgrade capacity scheme.

[0080] In some embodiments, the mathematical optimization algorithm is a mixed-integer linear programming (MILP) algorithm or a multi-objective evolutionary algorithm (such as NSGA-II).

[0081] Mixed Integer Linear Programming (MILP) Algorithm: If both the objective function and constraints can be linearized, this algorithm is preferred. It can efficiently find the global optimal solution to the problem and has a fast computation speed.

[0082] Multi-objective evolutionary algorithms (such as NSGA-II): These algorithms are used when the problem is highly nonlinear or when a set of Pareto optimal solutions that balance different objectives (such as lowest cost and highest safety margin) is desired for decision-makers to choose from.

[0083] Solution process: Input the mathematical expressions for the objective function and all constraints, along with the parameter values ​​obtained from S110, into the solver and start the calculation. The solver will automatically search for the numerical combination of decision variables that minimizes the objective function Z while satisfying all constraints.

[0084] After the algorithm completes the solution, the optimal values ​​of the key decision variables are extracted from the solver output.

[0085] Analysis based on the solution results:

[0086] Grid connection voltage level selection: View the binary variable x v The value of x is 1. v The corresponding voltage level v is the grid connection voltage level recommended by the model. There may be a single voltage level (such as only 1000kV) or a combination scheme (such as 500kV / 1000kV hierarchical access).

[0087] Power allocation scheme: View the continuous variable p j The value of p, each j The value represents the DC power P DC How much of the power is allocated to the absorption area j can be determined, and thus the power allocation ratio of each area can be calculated.

[0088] Space frame upgrade suggestion: Check the continuous variable u m The value of u is non-zero. m It indicates at which location (node ​​or line m) in the network structure the required capacity upgrade and expansion to meet the requirements for absorption and evacuation.

[0089] Comprehensive cost and safety indicators: Record the objective function value Z corresponding to the optimal solution, as well as the specific values ​​of various costs and penalties, to evaluate the economy and safety of the solution.

[0090] Furthermore, based on the analysis results, the following output will be provided:

[0091] Recommended grid-connected voltage level combination: Clarify the final voltage level selection.

[0092] Power allocation and transmission channel number for each absorption area: Provide the power level for each area and suggest the number of transmission channels (n) based on the power and line capacity. j .

[0093] Required space frame upgrade capacity and investment amount: List the space frame equipment to be upgraded, the upgrade capacity, and the estimated investment cost C. upgrade .

[0094] Key performance indicators comparison table: Provides the equivalent short-circuit ratio (SCR) under this scheme. effKey indicators include voltage stability margin and total investment cost.

[0095] In some embodiments, in order to verify the safety and feasibility of the optimization results in a real power grid environment, the recommended schemes (grid connection point, power allocation, grid upgrade, etc.) are substituted into power system simulation software (such as PSD-BPA, PSASP, etc.) for verification.

[0096] Verification content:

[0097] Power flow simulation: Verify whether the voltage of each node in the system is within the allowable range and whether each line and device is not overloaded under various typical operating conditions.

[0098] Short-circuit calculation / stability simulation: Accurately calculate the actual short-circuit ratio at the grid connection point, and perform transient stability and voltage stability analyses to verify whether the dynamic safety and stability level of the system meets the requirements of the regulations.

[0099] Feedback and Correction: If simulation verification reveals potential risks (such as voltage exceeding limits or stability issues), it is necessary to return to S120 and adjust the model's constraints (such as adjusting the SCR). min The requirements (or cost parameters) are then determined, and the solution is recalculated (S130) for a new round of iterative optimization until an optimized and safe solution is obtained.

[0100] Figure 2 This is a schematic diagram of the structure of the large-capacity inter-regional ultra-high voltage direct current receiving-end grid connection voltage level selection system provided in the embodiments of this application. See also... Figure 2 The system includes:

[0101] The data acquisition module is used to acquire the input parameters of the inter-regional ultra-high voltage direct current transmission system;

[0102] The optimization model building module is used to build an optimization model based on the input parameters. The optimization model includes an objective function with the core objective of minimizing the overall cost.

[0103] The output module is used to solve the optimization model using mathematical optimization algorithms, obtain the recommended grid-connected voltage level, the power allocation ratio of each absorption area, and the grid upgrade capacity scheme, and output them.

[0104] The execution process of the system part of this application embodiment is the same as that of the method part of the embodiment described above, and will not be repeated here.

[0105] This application also provides an electronic device, including: at least one processor; a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to execute any of the new energy-based power grid multi-resource coordinated control methods.

[0106] This application also proposes a computer storage medium storing a computer program, which, when executed by a processor, implements any one of the new energy-based power grid multi-resource coordinated control methods.

[0107] Computer storage media may be simply referred to as media. Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. Any references to memory, storage, databases, or other media used in the embodiments provided in this application may include non-volatile and / or volatile memory. Non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory may include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in various forms, such as Static RAM (SRAM), Dynamic RAM (DRAM), Synchronous DRAM (SDRAM), Dual Data SDRAM (DDRSDRAM), Enhanced SDRAM (ESDRAM), Synchlink DRAM (SLDRAM), Rambus Direct RAM (RDRAM), Direct Memory Bus Dynamic RAM (DRDRAM), and Memory Bus Dynamic RAM (RDRAM). The various embodiments described in this specification are presented in a progressive manner, and similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on describing the differences from other embodiments. In particular, for embodiments of apparatus, devices, and non-volatile computer storage media, since they are substantially similar to the method embodiments, the description is relatively simple, and relevant parts can be referred to the description of the method embodiments.

[0108] The above embodiments are merely illustrative examples and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom are still within the scope of protection of this application.

Claims

1. A method for selecting the grid connection voltage level of large-capacity inter-regional ultra-high voltage direct current transmission lines, characterized in that: include: Obtain the input parameters of the inter-regional ultra-high voltage direct current transmission system; Based on the input parameters, an optimization model is constructed, which includes an objective function with the core objective of minimizing the overall cost. The optimization model is solved using a mathematical optimization algorithm to obtain and output the recommended grid connection voltage level, the power allocation ratio of each absorption area, and the grid upgrade capacity scheme.

2. The method according to claim 1, characterized in that, The input parameters include rated DC output, maximum absorbable power of the target absorption area, capacity of the receiving-end grid, line corridor constraints, and short-circuit ratio data.

3. The method according to claim 1, characterized in that, The comprehensive cost includes the construction cost of the converter station, the investment cost of grid upgrade, and the cost of new line construction.

4. The method according to claim 3, characterized in that, The objective function of the optimization model also includes a penalty term for insufficient short-circuit ratio and a penalty term for unabsorbed power.

5. The method according to claim 4, characterized in that, The constraints of the optimization model include power balance constraints, regional absorption capacity constraints, grid dispersal capacity constraints, line corridor constraints, and short-circuit ratio safety constraints.

6. The method according to claim 1, characterized in that, When constructing the optimization model, multiple power grid operation scenarios are defined, and probability weights are assigned to each power grid operation scenario; the objective function of the optimization model is to minimize the weighted comprehensive cost of all power grid operation scenarios.

7. The method according to claim 1, characterized in that, The mathematical optimization algorithm is either a mixed-integer linear programming algorithm or a multi-objective evolutionary algorithm.

8. The method according to claim 1, characterized in that, Also includes: Based on the recommended output, power flow simulation and short-circuit simulation are performed to verify the system's safety margin.

9. A large-capacity, inter-regional ultra-high voltage direct current receiving-end grid connection voltage level selection system, characterized in that, include: The data acquisition module is used to acquire the input parameters of the inter-regional ultra-high voltage direct current transmission system; An optimization model construction module is used to construct an optimization model based on the input parameters, wherein the optimization model includes an objective function with the core objective of minimizing the overall cost. The output module is used to solve the optimization model using mathematical optimization algorithms to obtain and output the recommended grid-connected voltage level, the power allocation ratio of each absorption area, and the grid upgrade capacity scheme.

10. A computer-readable storage medium, characterized in that, It stores a computer program that, when executed in a computer, causes the computer to perform the method of any one of claims 1-8.

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