A method and system for optimizing network power capacity configuration

Abstract

The present invention discloses a method and system for optimizing the configuration of the capacity of a grid power source, and belongs to the technical field of power system planning. The method includes: based on the constraint conditions of the stability of the new energy grid connection, associating the technical indicators corresponding to the grid power source, estimating and giving the initial configuration capacity of the grid power source; selecting the access location of the grid power source as the high-voltage side and the low-voltage side of the step-up transformer of the new energy station; verifying whether the grid power source meets the constraint requirements according to the short-circuit ratio constraints of the new energy machine end and the grid connection point, the static safety constraints, and the transient stability constraints, and if not, adjusting the access capacity; if satisfied, calculating the cost required for the current capacity according to the comprehensive unit price; comparing the total cost of the corresponding capacity of the two access locations, and selecting the economically optimal as the final configuration capacity. This method takes the stability and economic optimization of the new energy station as the goal, determines the optimal access location and capacity of the grid power source when a single new energy station is connected to the grid, and improves the stability of the power grid in the new energy grid connection scenario.

Description

Technical Field

[0001] The present invention belongs to the technical field of power system planning, and more specifically, relates to a method and system for optimizing grid power capacity configuration. Background Art

[0002] In recent years, with the large-scale access of new energy to the grid, a new power system has gradually taken shape. The weak support of new energy power generation equipment has led to a low short-circuit ratio at the grid connection point and weak support for the grid voltage, making it difficult to meet the safety and stability requirements of the system. When the system is disturbed, the risk of system instability increases. This instability can not only cause the loss of new energy grid-connected power generation, but also may lead to a series of serious consequences, such as damage to power equipment and interruption of power supply, which has a huge impact on various fields such as industrial production and residents' lives.

[0003] In this context, the conventional practice is to introduce rotating synchronous phase condensers to improve the stability of new energy grid connection. With the advancement of technology, the industry has proposed the idea of ​​solving similar problems based on power electronic grid converters in recent years. The so-called grid power supply is based on the excellent control performance of power electronic equipment to achieve the role of voltage sources such as traditional thermal power and hydropower units in supporting the stability of the power grid. However, the cost of grid power supply equipment is high. How to improve the voltage support capability of grid power supply in the new power system through scientific and reasonable capacity configuration has become an urgent problem to be solved.

[0004] Existing research and practice mainly focus on equipment performance optimization and control strategies, while factors that affect capacity configuration, such as access location and stability requirements, are less considered; traditional power system planning methods mainly rely on experience and simple calculation models, and often ignore the impact of access location and economic factors. These methods are powerless in the face of complex and changeable new power demands. Especially in terms of site selection and capacity configuration, traditional practices may lead to waste of resources, low system efficiency and even safety hazards. At this stage, there is little research on economical and reasonable methods for configuring grid power capacity, with the constraints of improving the grid-connected stability and economy of new energy sites.

[0005] Prior art document 1 (CN118797893A) discloses a method and system for optimizing the configuration of grid-type energy storage equipment. Its shortcomings are that the access to grid-type energy storage only solves the transient overvoltage problem of a single system, does not pay attention to the static voltage stability and short-circuit ratio problems, and does not consider the economic efficiency of equipment access.

[0006] Prior art document 2 (CN116054218A) discloses a method, device, terminal and storage medium for optimizing the capacity of grid-type energy storage. Its shortcoming is that the access of grid-type energy storage only solves the problem of short-circuit ratio not meeting the standard, without considering the system stability and equipment economy. Summary of the invention

[0007] In order to address the deficiencies in the prior art, the present invention provides a method and system for optimizing the capacity configuration of a grid power source. Through the short-circuit ratio constraints of multiple stations at the machine end and the grid connection point, static safety constraints and transient stability constraints, the access location and capacity of the grid power source are determined under the economically optimal condition, thereby solving the problems of low short-circuit ratio and voltage stability after the grid connection of new energy, and providing strong support for the stable operation of new energy.

[0008] The present invention adopts the following technical solution.

[0009] A first aspect of the present invention provides a method for optimizing network power capacity configuration, specifically comprising:

[0010] Step 1: according to different constraints of renewable energy grid connection stability and combined with grid power technical indicators, estimate the initial configuration capacity of grid power;

[0011] Step 2: connect the initial configuration capacity of the grid power source estimated in step 1 to the high voltage side or low voltage side of the step-up transformer of the new energy station to obtain the current access side;

[0012] Step 3: Based on the configuration capacity of the current access side in step 2, the configuration capacity is calculated in turn according to the critical short-circuit ratio constraint, the static safety analysis constraint condition, and the transient stability analysis constraint condition to obtain the configuration capacity of the current access side that meets the constraints;

[0013] Step 4, comparing the configuration capacity of the current access side that meets the constraints obtained in step 3 with the initial configuration capacity of the network power supply, optimizing the configuration capacity of the current access side that meets the constraints according to the comparison result, obtaining the optimized configuration capacity of the current access side, and calculating the cost of the optimized configuration capacity of the current access side;

[0014] Step 5: Connect the initial configuration capacity of the grid power supply to the other access side of the step-up transformer of the new energy station, calculate the cost of the optimized configuration capacity of the other access side and compare it with the cost of the configuration capacity of the current access side calculated in step 4, and the configuration capacity with the lowest cost and its access side are respectively determined as the optimal configuration capacity and the optimal access side of the configuration capacity, so as to realize the optimization of the grid power supply capacity configuration.

[0015] Preferably, in step 1, the minimum value of the network power capacity estimated according to the short-circuit ratio of multiple stations at the new energy grid-connected point, the network power capacity estimated according to the static safety analysis constraint conditions, and the network power capacity estimated according to the transient stability analysis constraint conditions is set as the initial configuration capacity of the network power supply.

[0016] Preferably, according to the constraints of the stability of the new energy grid connection, the multi-station short-circuit ratio MRSCR of the new energy grid connection point w, combined with the grid power supply technical indicators including the grid power supply overcurrent multiple k, grid power supply rated current I n As well as the short-circuit current peaks of the system side, grid power supply and new energy, estimate S n1 , the grid power capacity S estimated based on the short-circuit ratio of multiple stations at the new energy grid connection point n1 , expressed as follows:

[0017]

[0018] In the formula,

[0019] MRSCR w In order to consider the short-circuit current peak simultaneous rate of the new energy grid connection point multi-station short-circuit ratio,

[0020] MRSCR wmin is the short-circuit ratio of multiple stations at critical new energy grid connection points,

[0021] SCR w The traditional short-circuit ratio of the new energy grid connection point is

[0022] c s 、c ES and c j They are the short-circuit current peak simultaneous coefficients of the system side, grid power supply and new energy,

[0023] I s ,I ES and I J They are the short-circuit currents provided by the system, grid power supply and new energy sources respectively.

[0024] I n is the rated current of the grid power supply,

[0025] U n is the rated voltage of the grid power supply,

[0026] k is the overcurrent multiple of the network power supply,

[0027] S n1 It is the estimated grid power capacity based on the short-circuit ratio of multiple stations at the renewable energy grid connection point.

[0028] Preferably, according to the static safety analysis constraint conditions in the constraint conditions of the stability of the new energy grid connection, combined with the static reactive voltage support coefficient k1 of the grid power supply included in the technical indicators of the grid power supply, S n2 , the grid power capacity S estimated according to the static safety analysis constraints n2 , expressed as follows:

[0029]

[0030] In the formula,

[0031] ΔQ1 is the static reactive power change,

[0032] ΔU1 is the static voltage change on the high-voltage side of the step-up transformer. If the voltage on the high-voltage side of the step-up transformer exceeds the lower limit after the system element is static N-1, ΔU1 is the difference between the lowest voltage after N-1 and the lower limit of the static safety analysis constraint; if the voltage on the high-voltage side of the step-up transformer exceeds the upper limit after the system element is static N-1, ΔU1 is the difference between the maximum voltage after N-1 and the upper limit of the static safety analysis constraint;

[0033] k1 is the static reactive voltage support coefficient of the grid power supply,

[0034] S n2 It is the estimated grid power capacity according to the static safety analysis constraints.

[0035] Preferably, according to the transient stability analysis constraints of the constraints of the new energy grid-connected stability, combined with the transient reactive voltage support factor k2 included in the grid power technical indicators, S n3 , the grid power capacity estimated according to the transient stability analysis constraints is expressed as follows:

[0036]

[0037] In the formula,

[0038] ΔQ2 is the transient reactive power change,

[0039] ΔU2 is the change in transient voltage at the generator end. After a transient N-1 fault occurs in the system, if a transient overvoltage occurs in the renewable energy source, ΔU2 is the difference between the maximum transient voltage at the generator end and the upper limit of the transient stability analysis constraint condition; if a transient undervoltage occurs in the renewable energy source, ΔU2 is the difference between the minimum transient voltage at the generator end and the lower limit of the transient stability analysis constraint condition;

[0040] k2 is the transient reactive voltage support coefficient,

[0041] S n3 It is the estimated grid power capacity based on transient stability analysis constraints.

[0042] Preferably, in step 2, the short-circuit ratio of multiple stations at the new energy machine end and the short-circuit ratio of multiple stations at the grid connection point are calculated according to the configuration capacity of the current access side, and the calculation results are combined with the critical short-circuit ratio to solve the configuration capacity that meets the critical short-circuit ratio;

[0043] Based on the solved configuration capacity that meets the critical short-circuit ratio, calculate the voltage of the new energy grid connection point after the static N-1 of a single component of the system, and combine the static safety analysis constraints to solve the configuration capacity that meets the static voltage;

[0044] Based on the solved configuration capacity that meets the static voltage, the voltage at the terminal of the new energy machine after a transient failure of a single component in the system is calculated. Combined with the transient stability analysis constraints, the configuration capacity that meets the constraints on the current access side is solved.

[0045] Preferably, the critical short-circuit ratio includes a critical short-circuit ratio of multiple stations at the new energy machine end and a critical short-circuit ratio of multiple stations at the new energy grid connection point, and it is judged whether the short-circuit ratio of multiple stations at the new energy machine end and the short-circuit ratio of multiple stations at the grid connection point are greater than the critical short-circuit ratio of multiple stations at the new energy machine end and the critical short-circuit ratio of multiple stations at the new energy grid connection point, respectively, and is expressed by the following formula:

[0046]

[0047] In the formula,

[0048] MRSCR j is the short-circuit ratio of multiple stations at the new energy machine end,

[0049] MRSCR jmin is the short-circuit ratio of multiple stations at the critical new energy machine end,

[0050] MRSCR w In order to consider the short-circuit current peak simultaneous rate of the new energy grid connection point multi-station short-circuit ratio,

[0051] MRSCR wmin It is the short-circuit ratio of multiple stations at critical new energy grid-connected points.

[0052] Preferably, the configuration capacity of the current access side is set to the access capacity. When the judgment result does not meet the formula 4, on the basis of the access capacity, the fixed adjustment capacity is repeatedly increased and the short-circuit ratio of the multi-station at the new energy machine end and the short-circuit ratio of the multi-station at the grid connection point are calculated again until the judgment result meets the formula 4. It is determined that the increased access capacity at this time is the configuration capacity that meets the critical short-circuit ratio; the increased access capacity is expressed by the following formula:

[0053] S′=S+ΔS (5)

[0054] In the formula,

[0055] S is the access capacity determined last time,

[0056] S' is the increased access capacity,

[0057] ΔS is the fixed regulation capacity.

[0058] Preferably, the static safety analysis constraint is expressed as follows:

[0059] U simin ≤U si ≤U simax (6)

[0060] In the formula,

[0061] U si It is the voltage of the new energy grid connection point after the static N-1 of a single component in the system.

[0062] U simax , U simin They are the upper and lower limits of the static constraint voltage after static N-1 respectively;

[0063] Set the configuration capacity that meets the critical short-circuit ratio as the access capacity, and calculate the voltage U of the new energy grid connection point after the static N-1 of a single component in the system. si , if U si If formula 6 is not satisfied, the fixed adjustment capacity is repeatedly added to the access capacity and U is calculated again. si Until U si If formula 6 is satisfied, it is determined that the increased access capacity is the configuration capacity that meets the static voltage.

[0064] Preferably, the transient stability analysis constraint is expressed as follows:

[0065] U timin ≤U ti ≤U timax (7)

[0066] In the formula,

[0067] U ti The voltage at the terminal of the new energy generator after a transient failure of a single component in the system.

[0068] U timax , U timin are the upper and lower limits of the transient constraint voltage after the fault respectively;

[0069] Set the configuration capacity that meets the static voltage to the access capacity. If U ti If formula 7 is not satisfied, the fixed adjustment capacity is repeatedly added to the access capacity and U is calculated again. ti Until U ti If formula 7 is satisfied, it is determined that the increased access capacity is the configuration capacity of the current access side that meets the constraints.

[0070] Preferably, in step 4, when the configuration capacity that meets the constraints of the current access side is equal to the initial configuration capacity of the network power supply, the initial configuration capacity of the network power supply is reduced by a fixed adjustment capacity, and the process returns to step 3 to re-solve the configuration capacity that meets the constraints of the current access side until the configuration capacity that meets the constraints of the current access side is greater than the initial configuration capacity of the network power supply, and the cost of the optimized configuration capacity of the current access side is calculated;

[0071] The initial configuration capacity of the grid power supply is reduced by a fixed adjustment capacity, which can be expressed as follows:

[0072] S1=S0-ΔS (8)

[0073] In the formula,

[0074] S0 is the initial configuration capacity of the grid power supply.

[0075] S1 is to reduce the post-access capacity,

[0076] ΔS is the fixed regulation capacity.

[0077] The second aspect of the present invention provides a network power capacity configuration optimization system, which runs the network power capacity configuration optimization method described in the first aspect of the present invention, including:

[0078] The initial configuration capacity estimation module is used to estimate the initial configuration capacity of the grid power supply according to different constraints on the stability of new energy grid connection and combined with the technical indicators of the grid power supply;

[0079] The access side setting module is used to connect the estimated initial configuration capacity of the grid power source to the high voltage side or low voltage side of the step-up transformer of the new energy station to obtain the current access side;

[0080] A configuration capacity optimization module is used to calculate the configuration capacity in sequence based on the configuration capacity of the current access side according to the critical short-circuit ratio constraint, the static safety analysis constraint condition and the transient stability analysis constraint condition, so as to obtain the configuration capacity of the current access side that meets the constraints;

[0081] The cost calculation module is used to compare the obtained configuration capacity that meets the constraints of the current access side with the initial configuration capacity of the network power supply, optimize the configuration capacity that meets the constraints of the current access side according to the comparison result, obtain the optimized configuration capacity of the current access side, and calculate the cost of the optimized configuration capacity of the current access side;

[0082] The optimal configuration capacity solution module is used to connect the initial configuration capacity of the grid power supply to the other access side of the step-up transformer of the new energy station, calculate the cost of the optimized configuration capacity of the other access side and compare it with the cost of the configuration capacity of the current access side. The configuration capacity with the lowest cost and its access side are respectively determined as the optimal configuration capacity and the optimal access side of the configuration capacity, so as to realize the optimization of the grid power supply capacity configuration.

[0083] Compared with the prior art, the beneficial effects of the present invention include at least:

[0084] The present invention proposes to determine the minimum capacity of the grid-building power supply required for each installation location under the constraints of the short-circuit ratio of the machine end and the grid connection point, the static safety constraint and the transient voltage stability constraint. On the other hand, it proposes to determine the actual access location of the grid-building power supply taking into account the optimal economy of the grid-building equipment access system. The present invention determines the optimal installation location and capacity of the grid-building power supply through iterative calculation, solves the problem of the short-circuit ratio of multiple new energy stations not meeting the standard, effectively suppresses the occurrence of static voltage and transient voltage exceeding the limit of the system, which causes the new energy to be disconnected from the grid, and has important value for improving the stability of the new energy grid connection. BRIEF DESCRIPTION OF THE DRAWINGS

[0085] Figure 1 A flowchart of a method for optimizing network power capacity configuration proposed in an embodiment of the present invention;

[0086] Figure 2 A geographical wiring diagram of a power grid in an embodiment of the present invention;

[0087] Figure 3 It is a voltage curve diagram of the new energy machine terminal after a transient fault in an embodiment of the present invention;

[0088] Figure 4 This is a voltage curve diagram of the new energy machine terminal after connecting to the optimized grid power supply in an embodiment of the present invention. DETAILED DESCRIPTION

[0089] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The described embodiments are only embodiments of a part of the present invention, not all embodiments. Based on the spirit of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the protection scope of the present invention.

[0090] like Figure 1 As shown, embodiment 1 of the present invention provides a method for optimizing network power capacity configuration, comprising the following steps:

[0091] Step 1: according to different constraints of renewable energy grid connection stability and combined with grid power technical indicators, estimate the initial configuration capacity of grid power;

[0092] Step 1.1: According to the constraints of renewable energy grid stability, the multi-station short-circuit ratio MRSCR of renewable energy grid connection points w The traditional short-circuit ratio SCR is used for preliminary estimation, combined with the grid power supply technical indicators including the grid power supply overcurrent multiple k, grid power supply rated current I n As well as the short-circuit current peak simultaneous coefficients of the system side, the grid power supply and the new energy, the grid power supply capacity estimated based on the short-circuit ratio of multiple stations at the new energy grid connection point is estimated, which is expressed as the following formula:

[0093]

[0094] In the formula,

[0095] MRSCR w In order to consider the short-circuit current peak simultaneous rate of the new energy grid connection point multi-station short-circuit ratio,

[0096] MRSCR wmin is the short-circuit ratio of multiple stations at critical new energy grid connection points,

[0097] SCR w The traditional short-circuit ratio of the new energy grid connection point is

[0098] c s 、c ES and c j They are the short-circuit current peak simultaneous coefficients of the system side, grid power supply and new energy,

[0099] I s is the system short-circuit current,

[0100] I ES The short-circuit current provided by the grid power supply,

[0101] I j The short-circuit current provided by new energy sources,

[0102] I n is the rated current of the grid power supply,

[0103] U n is the rated voltage of the grid power supply,

[0104] k is the overcurrent multiple of the network power supply,

[0105] S n1 It is the estimated grid power capacity based on the short-circuit ratio of multiple stations at the renewable energy grid connection point.

[0106] Step 1.2: According to the static safety analysis constraints of the new energy grid-connected stability constraints, combined with the technical indicators corresponding to the grid power supply, estimate the grid power supply capacity estimated according to the static safety analysis constraints;

[0107] The static safety analysis constraints in the constraints of new energy grid-connected stability are combined with the grid power static reactive voltage support factor k1 included in the grid power technical indicators to estimate the grid power capacity estimated based on the static safety analysis constraints, which can be expressed as the following formula:

[0108]

[0109] In the formula,

[0110] ΔQ1 is the static reactive power change,

[0111] ΔU1 is the static voltage change on the high-voltage side of the step-up transformer.

[0112] k1 is the static reactive voltage support coefficient of the grid power supply,

[0113] S n2 It is the estimated grid power capacity according to the static safety analysis constraints.

[0114] If the high-voltage side voltage of the step-up transformer after the static N-1 period of the system component exceeds the lower limit, ΔU1 is the difference between the lowest voltage after N-1 and the lower limit of the static safety analysis constraint; if the high-voltage side voltage of the step-up transformer after the static N-1 period of the system component exceeds the upper limit, ΔU1 is the difference between the maximum voltage after N-1 and the upper limit of the static safety analysis constraint.

[0115] Step 1.3: According to the transient stability analysis constraint in the constraint of new energy grid-connected stability, combined with the transient reactive voltage support coefficient k2 of the grid power source included in the technical indicators of the grid power source, estimate the initial configuration capacity of the grid power source;

[0116]

[0117] In the formula,

[0118] ΔQ2 is the transient reactive power change,

[0119] ΔU2 is the transient voltage change at the machine end.

[0120] k2 is the transient reactive voltage support coefficient of the grid power supply,

[0121] S n3 It is the estimated grid power capacity based on transient stability analysis constraints.

[0122] After a transient N-1 fault occurs in the system, if a transient overvoltage occurs in the renewable energy source, ΔU2 is the difference between the maximum transient voltage at the generator end and the upper limit of the transient stability analysis constraint condition; if a transient undervoltage occurs in the renewable energy source, ΔU2 is the difference between the minimum transient voltage at the generator end and the lower limit of the transient stability analysis constraint condition.

[0123] Step 1.4: Take the minimum value of the network power capacity estimated in steps 1.1, 1.2 and 1.3, and take the minimum network power capacity as the initial configuration capacity.

[0124] According to each set of constraints on the stability of new energy grid connection and the technical indicators of the associated grid-connected power source, the corresponding configuration capacity can be calculated. The minimum value of the grid-connected power source capacity estimated according to the short-circuit ratio of multiple stations at the new energy grid connection point, the grid-connected power source capacity estimated according to the constraints of static safety analysis, and the grid-connected power source capacity estimated according to the constraints of transient stability analysis is set as the initial configuration capacity of the grid-connected power source.

[0125] Step 2: Select the initial configuration capacity access location of the grid power source as the high voltage side or low voltage side of the step-up transformer of the new energy station, obtain the current access side, and enter the following steps in sequence;

[0126] Here, the access from the high-voltage side and the low-voltage side has no effect on the processing of subsequent steps. The initial capacity is set on the high-voltage side. The capacity set on the high-voltage side is calculated until step 4. After step 4, the corresponding price of the access capacity on the high-voltage side is obtained. Repeat the same steps to calculate the capacity of the access low-voltage side and obtain the corresponding price. Finally, in step 5, the two are compared to select the economically optimal final access location.

[0127] The side with the lowest cost is selected as the best access location. The setting of the initial capacity will not affect the final result, but setting the value arbitrarily may lead to too many iterations, so the initial capacity value is determined by estimation.

[0128] Step 3: Based on the configuration capacity of the current access side in step 2, the configuration capacity is calculated in turn according to the critical short-circuit ratio constraint, the static safety analysis constraint condition, and the transient stability analysis constraint condition to obtain the configuration capacity of the current access side that meets the constraints;

[0129] Step 3.1, based on the current configuration capacity of the access side, calculate the short-circuit ratio of multiple stations at the new energy machine end and the short-circuit ratio of multiple stations at the grid connection point, combine the calculation results with the critical short-circuit ratio, and solve the configuration capacity that meets the critical short-circuit ratio.

[0130] The configuration capacity of the current access side is set as the access capacity. After detailed system modeling through BPA simulation software, the short-circuit ratio of multiple stations on the grid-connected new energy machine end and the short-circuit ratio of multiple stations on the grid-connected point are calculated. The critical short-circuit ratio includes the critical short-circuit ratio of multiple stations on the critical new energy machine end and the short-circuit ratio of multiple stations on the critical new energy grid-connected point.

[0131] Determine whether the short-circuit ratio of multiple stations at the new energy machine end and the short-circuit ratio of multiple stations at the grid connection point are greater than the critical short-circuit ratio. If not, that is, when the judgment result does not meet the formula (4), then on the basis of the access capacity, increase the fixed regulation capacity, calculate the short-circuit ratio of multiple stations again, repeat the increase of the fixed regulation capacity and calculate the short-circuit ratio of multiple stations at the new energy machine end and the short-circuit ratio of multiple stations at the grid connection point again, until the judgment result meets the formula (4), go to step 3.2; if yes, that is, the judgment result meets the formula (4), go to step 3.2.

[0132] The critical short-circuit ratio includes the critical short-circuit ratio of multiple stations at the new energy machine end and the critical short-circuit ratio of multiple stations at the new energy grid connection point. It is judged whether the short-circuit ratio of multiple stations at the new energy machine end and the short-circuit ratio of multiple stations at the grid connection point are greater than the critical short-circuit ratio of multiple stations at the new energy machine end and the critical short-circuit ratio of multiple stations at the new energy grid connection point, respectively, and is expressed by the following formula

[0133]

[0134] In the formula,

[0135] MRSCR j is the short-circuit ratio of multiple stations at the new energy machine end,

[0136] MRSCR jmin is the short-circuit ratio of multiple stations at the critical new energy machine end,

[0137] MRSCR w To consider the short-circuit current peak simultaneous rate of the new energy grid connection point multi-station short-circuit ratio,

[0138] MRSCR wmin It is the short-circuit ratio of multiple stations at critical new energy grid-connected points.

[0139] When the fixed regulation capacity is added for the first time, S is the initial configuration of the grid power source connected in step 2.

[0140] On the basis of the previous access capacity, a fixed adjustment capacity is added. The corresponding formula is as follows:

[0141] S′=S+ΔS (5)

[0142] In the formula,

[0143] S is the access capacity determined last time,

[0144] S' is the increased access capacity,

[0145] ΔS is the fixed regulation capacity, which is a given empirical value and can be taken as 5% of the connected new energy capacity.

[0146] Step 3.2, based on the solved configuration capacity that meets the critical short-circuit ratio, calculate the voltage of the new energy grid-connected point after the static N-1 of a single component of the system, and combine the static safety analysis constraints to solve the configuration capacity that meets the static voltage.

[0147] Based on the static safety analysis constraints, determine the configuration capacity: According to the BPA simulation modeling and the power flow calculation method, calculate the voltage of the new energy grid connection point after the single component N-1 of the system, and compare it with the upper and lower limits of the static constraint voltage. If the upper and lower limits are not met, it is necessary to increase the fixed adjustment capacity on the basis of the capacity in step 3, and calculate the static N-1 again. If it is satisfied, go to step 3.3;

[0148] The grid operation requires that the bus voltage after static N-1 cannot exceed the limit. Step 3.2 is based on the short-circuit ratio of multiple stations in step 3.1. In order to further meet the voltage limit after static N-1, it is necessary to further increase the configuration capacity based on the capacity in step 3.1.

[0149] Set the configuration capacity that meets the critical short-circuit ratio as the access capacity, and calculate the voltage U of the new energy grid connection point after the static N-1 of a single component in the system. si , if U si If formula (6) is not satisfied, the fixed adjustment capacity is repeatedly added to the access capacity and U is calculated again. si Until U si If formula (6) is satisfied, it is determined that the increased access capacity is the configuration capacity that meets the static voltage.

[0150] Static safety analysis constraints are expressed as follows:

[0151] U simin ≤U si ≤U simax (6)

[0152] In the formula,

[0153] U si It is the voltage of the new energy grid connection point after the static N-1 of a single component in the system.

[0154] U simax , U simin They are the upper and lower limits of the static constraint voltage after static N-1 respectively.

[0155] Step 3.3, based on the solved configuration capacity that meets the static voltage, calculate the voltage at the terminal of the new energy machine after the transient failure of a single component of the system, and combine the transient stability analysis constraints to solve the configuration capacity that meets the constraints on the current access side.

[0156] Based on the transient stability analysis constraints, determine the configuration capacity: set the configuration capacity that meets the static voltage as the access capacity, calculate the voltage at the new energy machine end after a transient fault in a single component of the system, and compare it with the upper and lower limits of the transient constraint voltage. The voltage should be between the upper and lower limits of the transient constraint voltage. If it does not meet the upper and lower limits, that is, U tiIf formula (7) is not satisfied, it is necessary to repeatedly increase the fixed adjustment capacity on the access capacity and calculate U again. ti , check the fault again until U ti If formula (7) is satisfied, it is determined that the increased access capacity is the configuration capacity of the current access side that meets the constraints. If so, it is directly determined that the increased access capacity is the configuration capacity of the current access side that meets the constraints, and the process goes to step 4;

[0157] The transient stability analysis constraints are expressed as follows:

[0158] U timin ≤U ti ≤U timax (7)

[0159] In the formula,

[0160] U ti The voltage at the terminal of the new energy generator after a transient failure of a single component in the system.

[0161] U timax , U timin They are the upper and lower limits of the transient constraint voltage after the fault respectively.

[0162] Step 4, compare the configuration capacity of the current access side that meets the constraints obtained in step 3 with the initial configuration capacity of the network power supply, optimize the configuration capacity of the current access side that meets the constraints according to the comparison result, obtain the optimized configuration capacity of the current access side, and calculate the cost of the optimized configuration capacity of the current access side;

[0163] If the configuration capacity that meets the constraints of the current access side is equal to the initial configuration capacity of the network power supply, then reduce the initial configuration capacity of the network power supply by a fixed adjustment capacity, and return to step 3 to re-solve the configuration capacity that meets the constraints of the current access side until the configuration capacity that meets the constraints of the current access side is greater than the initial configuration capacity of the network power supply, and calculate the cost of the optimized configuration capacity of the current access side; if the configuration capacity that meets the constraints of the current access side is greater than the initial configuration capacity of the network power supply, then calculate the cost required for the optimized configuration capacity of the current access side according to the comprehensive unit price;

[0164] Step 4 includes comparing the current capacity with the initial configuration capacity. If the current capacity is equal to the initial configuration capacity, the initial configuration capacity of the grid power supply is reduced by a fixed adjustment capacity. The corresponding formula is as follows:

[0165] S1=S0-ΔS (8)

[0166] In the formula,

[0167] S0 is the initial configuration capacity,

[0168] S1 is to reduce the post-access capacity,

[0169] ΔS is the fixed regulation capacity, which is a given empirical value and can be taken as 5% of the connected new energy capacity.

[0170] The fixed regulation capacity in formula (8) and the fixed regulation capacity in formula (5) are set to the same value.

[0171] Calculate the cost of the current capacity based on the comprehensive unit price, which needs to take into account the equipment price, installation and maintenance costs, land cost, and the cost of supporting secondary protection and monitoring equipment;

[0172] Step 5, connect the initial configuration capacity of the grid power supply to the other access side of the step-up transformer of the new energy station, calculate the cost of the optimized configuration capacity of the other access side according to steps 3 to 4 and compare it with the cost of the configuration capacity of the current access side calculated in step 4, determine the configuration capacity with the lowest cost as the optimal configuration capacity, obtain the optimal configuration capacity, and realize the optimization of the grid power supply capacity configuration.

[0173] Compared with the prior art, the beneficial effects of the present invention include at least:

[0174] The present invention proposes to determine the minimum capacity of the grid-building power supply required for each installation location under the constraints of the short-circuit ratio of the machine end and the grid connection point, the static safety constraint and the transient voltage stability constraint. On the other hand, it proposes to determine the actual access location of the grid-building power supply taking into account the optimal economy of the grid-building equipment access system. The present invention determines the optimal installation location and capacity of the grid-building power supply through iterative calculation, solves the problem of the short-circuit ratio of multiple new energy stations not meeting the standard, effectively suppresses the new energy disconnection caused by the static voltage and transient fault voltage exceeding the limit of the system, and is of great value to improving the stability of the new energy grid connection.

[0175] Example 2

[0176] like Figure 2 As shown, embodiment 2 of the present invention provides a network power capacity configuration optimization system, which runs a network power capacity configuration optimization method described in embodiment 1, including:

[0177] The initial configuration capacity estimation module is used to estimate the initial configuration capacity of the grid power supply according to different constraints on the stability of new energy grid connection and combined with the technical indicators of the grid power supply;

[0178] The access side setting module is used to connect the estimated initial configuration capacity of the grid power source to the high voltage side or low voltage side of the step-up transformer of the new energy station to obtain the current access side;

[0179] A configuration capacity optimization module is used to calculate the configuration capacity in sequence based on the configuration capacity of the current access side according to the critical short-circuit ratio constraint, the static safety analysis constraint condition and the transient stability analysis constraint condition, so as to obtain the configuration capacity of the current access side that meets the constraints;

[0180] A cost calculation module is used to compare the obtained configuration capacity that meets the constraints of the current access side with the initial configuration capacity of the network power supply, optimize the configuration capacity that meets the constraints of the current access side according to the comparison result, obtain the optimized configuration capacity of the current access side, and calculate the cost of the optimized configuration capacity of the current access side;

[0181] The optimal configuration capacity solution module is used to connect the initial configuration capacity of the grid power supply to the other access side of the step-up transformer of the new energy station, calculate the cost of the optimized configuration capacity of the other access side and compare it with the cost of the calculated configuration capacity of the current access side. The configuration capacity with the lowest cost is determined as the optimal configuration capacity, and the optimal configuration capacity is obtained to achieve the optimization of the grid power supply capacity configuration.

[0182] Example 3

[0183] like Figure 2 As shown, Example 3 of the present invention takes a certain local renewable energy power grid as an example, and studies the connection of a newly built 200MW photovoltaic station D10 to the grid, and then connects D11 to the high-voltage side and the low-voltage side of the boost transformer to solve the problem of photovoltaic power transmission stability. D10 has a capacity of 200MW and is connected to the grid 110kV C4 substation. After step-by-step boosting of 110 / 330kV and 330 / 750kV, it is collected at the 750kV A2 station for transmission. D1~D9 are 9 existing renewable energy stations with a total capacity of 2200MW.

[0184] Step 1: Estimate and determine the initial configuration capacity of the grid power supply.

[0185] (1) The 110kV busbar of D10 station is the new energy grid connection point. The required short-circuit ratio of multiple stations is not less than 2. The overcurrent multiple of D11 grid power supply is k=3. The system provides a short-circuit current I s =127.625kA, short-circuit current peak simultaneous coefficient c s =0.96, c ES =0.98 and c j =0.98, the grid power configuration capacity can be estimated according to formula (1), and S n1 =10.0MW, which is 5% of the photovoltaic capacity.

[0186] (2) According to the difference between the lowest voltage of the 110kV grid connection point after the single element of the system is static N-1 and the lower limit of the static safety analysis constraint condition (99kV), it can be obtained that ΔU1 = 4.6kV and the static reactive voltage support coefficient k1 = 2.8. According to formula (2), the grid power configuration capacity can be estimated to calculate S n2 =12.8MW, accounting for 6.4% of photovoltaic capacity.

[0187] (3) According to the transient overvoltage caused by the transient three-phase N-1 fault at the 110kV grid connection point, as shown in the attached figure Figure 2 As shown in the figure, taking the difference between the maximum overvoltage and the upper limit of the transient stability analysis constraint condition (1.3pu), we can get ΔU1 = 16.5kV, the transient reactive voltage support factor adjustment factor k1 = 3.0, and according to formula (3), the grid power configuration capacity is estimated to calculate S n =39.5MW, which is 19.75% of the photovoltaic capacity.

[0188] (4) Among the three estimated capacities, take the minimum value S n1 = 10MW as the initial configuration capacity S n .

[0189] Step 2: Select the high voltage side of the D10 step-up transformer as the initial access point.

[0190] Step 3: Optimize the configuration capacity that meets the constraints on the current access side according to the critical short-circuit ratio constraints, static safety analysis constraints, and transient stability analysis constraints.

[0191] (1) After the grid power supply is connected, the short-circuit ratio of the grid-connected new energy machine end and the grid-connected point multi-station is calculated through simulation, and the results are as follows:

[0192]

[0193] The critical value of the short-circuit ratio of multiple stations at the machine end is 1.5, and the critical value of the short-circuit ratio of multiple stations at the grid connection point is 2. It can be judged that the current capacity does not meet the requirements.

[0194] When the capacity is increased to 10+200*5%=20MW, the short-circuit ratio calculation results are as follows:

[0195]

[0196] If the short-circuit ratio of multiple stations at the machine end and the grid connection point meets the requirements, go to step 4.

[0197] (2) The voltage at the grid connection point of the new energy source after the simulation calculation of the single component N-1 of the system. The minimum voltage of the system is shown in Table 1. The static constraint voltage value range of 110 kV is: 0.9 pu ≤ U si ≤1.1pu.

[0198] Table 1 Minimum voltage of new energy grid connection point after single component N-1 in the system

[0199]

[0200] The grid connection point voltage meets the static constraint voltage range requirements.

[0201] (3) The voltage at the terminal of the new energy generator after a transient fault occurs in the system is calculated by simulation. The voltage curve at the terminal of the new energy generator after a transient fault is shown in the attached figure. Figure 3 As shown, the transient constraint voltage range is 0.85pu≤U ti ≤1.3pu. When the access capacity is 20MW, after transient stability analysis, after the A1-A2 line has a three-permanent N-1 fault, there is still a transient overvoltage problem;

[0202] Continue to increase the capacity twice to 20+2*200*5%=40MW. After the A1-A2 line has a three-permanent N-1 fault, the voltage at the new energy generator terminal meets the requirements of the upper and lower threshold values ​​of the transient voltage. The voltage curve is as shown in the attached figure. Figure 4 shown.

[0203] Step 4: Compare the access capacity of 40MW in step 3 with the initial configuration capacity of 10MW. The access capacity is larger than the initial configuration capacity. The cost required for the current capacity is calculated based on the comprehensive unit price. The comprehensive unit price of network power sources at different voltage levels is shown in Table 2.

[0204] Table 2 Comprehensive unit price of grid power supply at different voltage levels

[0205]

[0206] Based on the high-voltage side grid power configuration capacity of 40MW, the total cost can be calculated to be 23.76 million yuan.

[0207] Step 5: Similarly to steps 1-4, it can be calculated that the grid power capacity required on the low-voltage side is 30MW, and the total cost is 14.7 million yuan.

[0208] After comparison, connecting the low-voltage side of the step-up transformer to the grid power supply is the most economical result, so the final configuration plan is to connect the grid power supply to the low-voltage 35kV side of the step-up transformer, with a configuration capacity of 30MW, which is 15% of the photovoltaic capacity.

[0209] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for optimizing network power capacity configuration, characterized in that: include: According to different constraints on the stability of new energy grid connection and combined with the technical indicators of grid power supply, the initial configuration capacity of grid power supply is estimated; Connecting the estimated initial configuration capacity of the grid power source to the high voltage side or low voltage side of the step-up transformer of the new energy station to obtain the current connection side; Based on the configuration capacity of the current access side, the configuration capacity is calculated in sequence according to the critical short circuit ratio constraint, the static safety analysis constraint condition and the transient stability analysis constraint condition to obtain the configuration capacity of the current access side that meets the constraints; Compare the obtained configuration capacity of the current access side that meets the constraints with the initial configuration capacity of the network power supply, optimize the configuration capacity of the current access side that meets the constraints according to the comparison result, obtain the optimized configuration capacity of the current access side, and calculate the cost of the optimized configuration capacity of the current access side; The initial configuration capacity of the grid power supply is connected to the other access side of the step-up transformer of the new energy station, the cost of the optimized configuration capacity on the other access side is calculated and compared with the cost of the configuration capacity on the current access side, the configuration capacity with the lowest cost and its access side are respectively determined as the optimal configuration capacity and the access side with the optimal configuration capacity, so as to realize the optimization of the grid power supply capacity configuration.

2. A method for optimizing network power capacity configuration according to claim 1, characterized in that: The minimum value of the grid power supply capacity estimated according to the short-circuit ratio of multiple stations at the new energy grid-connected point, the grid power supply capacity estimated according to the static safety analysis constraint conditions, and the grid power supply capacity estimated according to the transient stability analysis constraint conditions is set as the initial configuration capacity of the grid power supply.

3. According to a method for optimizing network power capacity configuration as claimed in claim 2, it is characterized in that: According to the constraints of new energy grid stability, the short-circuit ratio of multiple stations at the new energy grid connection point MRSCR w , combined with the grid power supply technical indicators including the grid power supply overcurrent multiple k, grid power supply rated current I n As well as the short-circuit current peaks of the system side, grid power supply and new energy, estimate S n1 ; Estimated grid power capacity S based on short-circuit ratio of multiple stations at new energy grid connection points n1 , expressed as follows: In the formula, MRSCR w In order to consider the short-circuit current peak simultaneous rate of the new energy grid connection point multi-station short-circuit ratio, MRSCR wmin is the short-circuit ratio of multiple stations at critical new energy grid connection points, SCR w The traditional short-circuit ratio of the new energy grid connection point is c s 、c ES and c j They are the short-circuit current peak simultaneous coefficients of the system side, grid power supply and new energy, I s ,I ES and I j The short-circuit current provided by the system, grid power supply and new energy respectively. I n is the rated current of the grid power supply, U n is the rated voltage of the grid power supply, k is the overcurrent multiple of the network power supply, S n1 It is the estimated grid power capacity based on the short-circuit ratio of multiple stations at the renewable energy grid connection point.

4. A method for optimizing network power capacity configuration according to claim 2, characterized in that: According to the static safety analysis constraints in the constraints of new energy grid-connected stability, combined with the grid power supply static reactive voltage support coefficient k1 included in the grid power supply technical indicators, S n2 ; The grid power capacity S estimated according to the static safety analysis constraints n2 , expressed as follows: In the formula, ΔQ1 is the static reactive power change, ΔU1 is the static voltage change on the high-voltage side of the step-up transformer. If the voltage on the high-voltage side of the step-up transformer exceeds the lower limit after the system element is static N-1, ΔU1 is the difference between the lowest voltage after N-1 and the lower limit of the static safety analysis constraint; If the voltage on the high-voltage side of the step-up transformer exceeds the upper limit after the static N-1 period of the system element, ΔU1 is the difference between the maximum voltage after N-1 and the upper limit of the static safety analysis constraint condition; k1 is the static reactive voltage support coefficient of the grid power supply, S n2 It is the estimated grid power capacity according to the static safety analysis constraints.

5. A method for optimizing network power capacity configuration according to claim 2, characterized in that: According to the transient stability analysis constraints of the new energy grid-connected stability constraints, combined with the transient reactive voltage support factor k2 included in the grid power technical indicators, S n3 ; The grid power capacity estimated according to the transient stability analysis constraints is expressed as follows: In the formula, ΔQ2 is the transient reactive power change, ΔU2 is the change in transient voltage at the generator end. After a transient N-1 fault occurs in the system, if a transient overvoltage occurs in the renewable energy source, ΔU2 is the difference between the maximum transient voltage at the generator end and the upper limit of the transient stability analysis constraint condition. If the renewable energy has a transient low voltage, ΔU2 is the difference between the minimum transient voltage of the generator terminal and the lower limit of the transient stability analysis constraint; k2 is the transient reactive voltage support coefficient, S n3 It is the estimated grid power capacity based on transient stability analysis constraints.

6. A method for optimizing network power capacity configuration according to claim 1, characterized in that: According to the current configuration capacity of the access side, calculate the short-circuit ratio of multiple stations at the new energy machine end and the short-circuit ratio of multiple stations at the grid connection point, combine the calculation results with the critical short-circuit ratio, and solve the configuration capacity that meets the critical short-circuit ratio; Based on the solved configuration capacity that meets the critical short-circuit ratio, calculate the voltage of the new energy grid connection point after the static N-1 of a single component of the system, and combine the static safety analysis constraints to solve the configuration capacity that meets the static voltage; Based on the solved configuration capacity that meets the static voltage, the voltage at the terminal of the new energy machine after a transient failure of a single component in the system is calculated. Combined with the transient stability analysis constraints, the configuration capacity that meets the constraints on the current access side is solved.

7. A method for optimizing network power capacity configuration according to claim 6, characterized in that: The critical short-circuit ratio includes the critical short-circuit ratio of multiple stations at the new energy machine end and the critical short-circuit ratio of multiple stations at the new energy grid connection point. It is judged whether the short-circuit ratio of multiple stations at the new energy machine end and the short-circuit ratio of multiple stations at the grid connection point are greater than the critical short-circuit ratio of multiple stations at the new energy machine end and the critical short-circuit ratio of multiple stations at the new energy grid connection point, respectively, and is expressed by the following formula: In the formula, MRSCR j is the short-circuit ratio of multiple stations at the new energy machine end, MRSCR jmin is the short-circuit ratio of multiple stations at the critical new energy machine end, MRSCR w In order to consider the short-circuit current peak simultaneous rate of the new energy grid connection point multi-station short-circuit ratio, MRSCR wmin It is the short-circuit ratio of multiple stations at the critical new energy grid connection point; The configuration capacity of the current access side is set as the access capacity. When the judgment result does not meet the formula 4, the fixed adjustment capacity is repeatedly increased on the basis of the access capacity and the short-circuit ratio of multiple stations at the new energy machine end and the short-circuit ratio of multiple stations at the grid connection point are calculated again until the judgment result meets the formula 4. It is determined that the increased access capacity at this time is the configuration capacity that meets the critical short-circuit ratio. The increased access capacity is expressed by the following formula: S′=S+ΔS (5) In the formula, S is the access capacity determined last time, S' is the increased access capacity, ΔS is the fixed regulation capacity.

8. A method for optimizing network power capacity configuration according to claim 6, characterized in that: Static safety analysis constraints are expressed as follows: IN simin ≤U si ≤U simax (6) In the formula, U si It is the voltage of the new energy grid connection point after the static N-1 of a single component in the system. U simax , U simin They are the upper and lower limits of the static constraint voltage after static N-1 respectively; Set the configuration capacity that meets the critical short-circuit ratio as the access capacity, and calculate the voltage U of the new energy grid connection point after the static N-1 of a single component in the system. si , if U si If formula 6 is not satisfied, the fixed adjustment capacity is repeatedly added to the access capacity and U is calculated again. si Until U si If formula 6 is satisfied, it is determined that the increased access capacity is the configuration capacity that meets the static voltage; The transient stability analysis constraints are expressed as follows: IN timin ≤U ti ≤U timax (7) In the formula, U ti The voltage at the terminal of the new energy generator after a transient failure of a single component in the system. U timax , U timin are the upper and lower limits of the transient constraint voltage after the fault respectively; Set the configuration capacity that meets the static voltage to the access capacity. If U ti If formula 7 is not satisfied, the fixed adjustment capacity is repeatedly added to the access capacity and U is calculated again. ti Until U ti If formula 7 is satisfied, it is determined that the increased access capacity is the configuration capacity of the current access side that meets the constraints.

9. A method for optimizing network power capacity configuration according to claim 1, characterized in that: When the configuration capacity that meets the constraints on the current access side is equal to the initial configuration capacity of the network power supply, the initial configuration capacity of the network power supply is reduced by a fixed adjustment capacity, and the configuration capacity that meets the constraints on the current access side is solved again until the configuration capacity that meets the constraints on the current access side is greater than the initial configuration capacity of the network power supply, and the cost of the optimized configuration capacity on the current access side is calculated; The initial configuration capacity of the grid power supply is reduced by a fixed adjustment capacity, which can be expressed as follows: S1=S0-ΔS (8) In the formula, S0 is the initial configuration capacity of the grid power supply. S1 is to reduce the post-access capacity, ΔS is the fixed regulation capacity.

10. A network power capacity configuration optimization system, running a network power capacity configuration optimization method according to any one of claims 1 to 9, characterized in that: The initial configuration capacity estimation module is used to estimate the initial configuration capacity of the grid power supply according to different constraints on the stability of new energy grid connection and combined with the technical indicators of the grid power supply; The access side setting module is used to connect the estimated initial configuration capacity of the grid power source to the high voltage side or low voltage side of the step-up transformer of the new energy station to obtain the current access side; A configuration capacity optimization module is used to calculate the configuration capacity in sequence based on the configuration capacity of the current access side according to the critical short-circuit ratio constraint, the static safety analysis constraint condition and the transient stability analysis constraint condition, so as to obtain the configuration capacity of the current access side that meets the constraints; The cost calculation module is used to compare the obtained configuration capacity that meets the constraints of the current access side with the initial configuration capacity of the network power supply, optimize the configuration capacity that meets the constraints of the current access side according to the comparison result, obtain the optimized configuration capacity of the current access side, and calculate the cost of the optimized configuration capacity of the current access side; The optimal configuration capacity solution module is used to connect the initial configuration capacity of the grid power supply to the other access side of the step-up transformer of the new energy station, calculate the cost of the optimized configuration capacity of the other access side and compare it with the cost of the configuration capacity of the current access side. The configuration capacity with the lowest cost and its access side are respectively determined as the optimal configuration capacity and the optimal access side of the configuration capacity, so as to realize the optimization of the grid power supply capacity configuration.

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