Method and device for evaluating frequency security new energy receiving capacity caused by voltage drop

Abstract

The application discloses a new energy receiving capacity evaluation method and system for frequency safety caused by voltage drop, and the voltage drop degree of new energy and the voltage drop degree of load are calculated, and then the system short-time energy impact caused by voltage drop, that is, the active power change of new energy and the active power change of load, is evaluated; the maximum kinetic energy change amount allowed by the system is combined; the current power flow mode is evaluated as the minimum starting mode and the maximum receiving capacity, so that the new energy receiving capacity evaluation method for the system short-time power impact scene caused by voltage drop is realized, and the research on the new energy receiving capacity evaluation under the frequency safety and stability constraint is further improved.

Description

Technical Field

[0001] This invention relates to a method and apparatus for assessing the acceptance capacity of new energy sources for frequency security caused by voltage dips, belonging to the field of power system and automation technology. Background Technology

[0002] Current assessment methods for renewable energy integration capacity mainly consider the following aspects: power system peak-shaving capacity, system economic dispatch, and system security and stability. Among these, the assessment method for renewable energy integration capacity with transient frequency security and stability as a constraint typically considers the maximum possible permanent power loss / surplus scenario that the system may experience.

[0003] With the replacement of a large number of synchronous generators, the proportion of renewable energy is increasing, the dynamic reactive power support capacity is decreasing, and the AC system strength is declining. The low-voltage ride-through range of renewable energy sources after short-term short-circuit faults in the power grid will further expand, and the recovery process will be further prolonged. Short-term voltage disturbances cause power flow fluctuations in the near-area and renewable energy sources, resulting in short-term power surges across the entire network that may pose a risk to system frequency stability. In systems with a high proportion of renewable energy, the impact of short-term power surges caused by ordinary voltage dips on the entire network's frequency can be even more severe than the impact of permanent power loss. Therefore, the impact of short-term high-power surges caused by voltage dips on system frequency safety and stability will become one of the important factors that cannot be ignored in assessing the renewable energy integration capacity. However, there is currently no method for assessing the renewable energy integration capacity in scenarios involving short-term power surges caused by voltage dips. Summary of the Invention

[0004] This invention provides a method and apparatus for assessing the acceptance capability of new energy sources for frequency security caused by voltage dips, which solves the problems disclosed in the background art.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0006] Methods for assessing the capacity to accept new energy sources include:

[0007] The voltage drop of the new energy source is calculated based on the short-circuit current of the new energy source under the current power flow mode, the electrical distance of the new energy source relative to the voltage drop fault point, and the voltage drop degree of the voltage drop fault point.

[0008] The voltage sag of the load is calculated based on the short-circuit current of the load under the current power flow mode, the electrical distance of the load relative to the voltage sag fault point, and the voltage sag degree of the voltage sag fault point.

[0009] Based on the voltage sag of renewable energy sources and the low-voltage ride-through control strategy for renewable energy sources, the change in active power of renewable energy sources during the voltage sag period under the current power flow mode is calculated.

[0010] Based on the degree of voltage drop in the load and the power change characteristics of the load after being disturbed by voltage drop, calculate the change of active power of the load during the voltage drop period under the current power flow mode.

[0011] Calculate the short-time energy change of the entire network based on the changes in active power of new energy sources and the changes in active power of loads;

[0012] If the short-term energy change of the entire network is less than or equal to the maximum kinetic energy change allowed by the system under the current power flow mode, and the absolute value of the difference between the short-term energy change of the entire network and the maximum kinetic energy change is less than the kinetic energy change of a single generator that has been started in the system under voltage drop disturbance, then the current power flow mode is the minimum start-up mode, and the current renewable energy capacity is the maximum capacity under the current power flow mode.

[0013] Based on the short-circuit current of the renewable energy source under the current power flow conditions, the electrical distance of the renewable energy source relative to the voltage sag fault point, and the voltage sag degree of the voltage sag fault point, the voltage sag degree of the renewable energy source is calculated, including:

[0014] Based on the short-circuit current of the renewable energy source and the electrical distance of the renewable energy source relative to the voltage dip fault point under the current power flow mode, calculate the voltage impact factor of the voltage dip fault point on the renewable energy source.

[0015] The voltage drop degree of new energy sources is calculated based on the voltage impact factor of the voltage drop fault point on the new energy source and the voltage drop degree of the voltage drop fault point.

[0016] The formula for calculating the voltage impact factor of voltage dip fault points on new energy sources is:

[0017]

[0018] Among them, S k-i Let I be the voltage impact factor of voltage drop fault point k on new energy source i. i Z is the short-circuit current of new energy i. ki Let i be the electrical distance of the new energy source i relative to the voltage drop fault point k;

[0019] The voltage drop of a new energy source is the product of the voltage drop fault point's influence factor on the new energy source's voltage and the voltage drop degree of the fault point.

[0020] Based on the load's short-circuit current under the current power flow pattern, the electrical distance of the load relative to the voltage dip fault point, and the degree of voltage dip at the voltage dip fault point, calculate the load's voltage dip degree, including:

[0021] Based on the short-circuit current of the load and the electrical distance of the load relative to the voltage dip fault point under the current power flow mode, calculate the voltage impact factor of the voltage dip fault point on the load.

[0022] The voltage drop degree of the load is calculated based on the voltage impact factor of the voltage drop fault point on the load and the voltage drop degree of the voltage drop fault point.

[0023] The formula for calculating the voltage impact factor of a voltage dip fault point on the load is:

[0024]

[0025] Among them, S k-j I is the voltage impact factor of the voltage drop fault point k on the load j. j Z is the short-circuit current of load j. kj Let j be the electrical distance of the load j relative to the voltage drop fault point k;

[0026] The voltage drop of the load is the product of the voltage drop fault point's influence factor on the load's voltage and the voltage drop degree of the fault point.

[0027] Based on the voltage sag of renewable energy sources and the low-voltage ride-through control strategy, the change in active power of renewable energy sources during the voltage sag period under the current power flow mode is calculated, including:

[0028] Calculate the voltage at the generator terminals of the new energy source based on the voltage drop of the new energy source.

[0029] Based on the relationship between the generator terminal voltage and active current in the low-voltage ride-through control strategy for new energy sources, the active power of new energy sources during voltage dips under the current power flow mode is calculated.

[0030] Based on the active power of renewable energy sources during voltage dips and the steady-state active power of renewable energy sources under the current power flow pattern, calculate the change in active power of renewable energy sources during voltage dips under the current power flow pattern.

[0031] Based on the degree of voltage sag in the load and the power change characteristics of the load after being disturbed by the voltage sag, the change in active power of the load during the voltage sag under the current power flow mode is calculated, including:

[0032] Calculate the load voltage based on the degree of voltage drop across the load;

[0033] Based on the relationship between load voltage and active power in the power change characteristics after the load is subjected to voltage dip disturbance, calculate the load active power during the voltage dip under the current power flow mode.

[0034] Based on the load active power and load steady-state active power during the voltage dip under the current power flow mode, calculate the change in load active power during the voltage dip under the current power flow mode.

[0035] The formula for calculating the short-time energy change of the entire network is:

[0036]

[0037] Where ΔW is the short-term energy change of the entire network, t0 is the voltage drop time, t is the voltage recovery time, and ΔP is the voltage drop time. i Let ΔP be the change in active power of new energy source i. j Let be the change in active power of load j, m be the total number of new energy sources in the entire network, and n be the total number of loads in the entire network.

[0038] The maximum change in kinetic energy is calculated based on the system's lowest frequency constraint, using the following formula:

[0039]

[0040] Where, ΔE MWs J represents the maximum permissible change in kinetic energy of the system under the current power flow pattern. i1 Let ωi1 be the moment of inertia of the generator rotor, ω0 be the generator speed during stable operation, and ωi be the rotational speed. min N represents the minimum permissible speed during the generator transient process, N represents the total number of generators in operation under the current power flow mode, and M represents the number of generators after they are replaced by new energy sources.

[0041] The evaluation method also includes:

[0042] If the short-term energy change of the entire network is less than or equal to the maximum kinetic energy change allowed by the system under the current power flow mode, and the absolute value of the difference between the short-term energy change of the entire network and the maximum kinetic energy change is greater than the maximum kinetic energy change allowed by a single generator already started in the system, the system power balance is maintained by increasing new energy sources while shutting down traditional generator sets, thus obtaining a new power flow mode. The new energy acceptance capacity is then reassessed based on the new power flow mode.

[0043] The renewable energy acceptance capacity assessment device includes:

[0044] The new energy voltage drop calculation module is used to calculate the voltage drop of the new energy based on the short-circuit current of the new energy under the current power flow mode, the electrical distance of the new energy relative to the voltage drop fault point, and the voltage drop degree of the voltage drop fault point.

[0045] The load voltage dip calculation module is used to calculate the load voltage dip based on the load short-circuit current, the electrical distance of the load relative to the voltage dip fault point, and the voltage dip degree of the voltage dip fault point under the current power flow mode.

[0046] The active power change calculation module for new energy sources is used to calculate the change in active power of new energy sources during voltage dips under the current power flow mode, based on the voltage dip level of new energy sources and the low voltage ride-through control strategy of new energy sources.

[0047] The load active power change calculation module is used to calculate the load active power change during the voltage drop period under the current power flow mode, based on the degree of voltage drop of the load and the power change characteristics of the load after being disturbed by voltage drop.

[0048] The whole network short-time energy change calculation module is used to calculate the whole network short-time energy change based on the changes in active power of new energy sources and the changes in active power of loads;

[0049] The first evaluation module is used to determine if the short-term energy change of the entire network is less than or equal to the maximum kinetic energy change allowed by the system under the current power flow mode, and the absolute value of the difference between the short-term energy change of the entire network and the maximum kinetic energy change is less than the kinetic energy change of a single generator that has been started in the system under voltage drop disturbance. In this case, the current power flow mode is the minimum start-up mode, and the current renewable energy capacity is the maximum capacity under the current start-up mode.

[0050] The new energy voltage drop calculation module includes:

[0051] The first voltage impact factor calculation module is used to calculate the voltage impact factor of the voltage drop fault point on the new energy source based on the short-circuit current of the new energy source and the electrical distance of the new energy source relative to the voltage drop fault point under the current power flow mode.

[0052] The first voltage drop calculation module is used to calculate the voltage drop degree of new energy sources based on the voltage impact factor of the voltage drop fault point on the new energy source and the voltage drop degree of the voltage drop fault point.

[0053] The load voltage drop calculation module includes:

[0054] The second voltage influence factor calculation module is used to calculate the voltage influence factor of the voltage drop fault point on the load based on the short-circuit current of the load and the electrical distance of the load relative to the voltage drop fault point under the current power flow mode.

[0055] The second voltage dip calculation module is used to calculate the voltage dip of the load based on the voltage impact factor of the voltage dip fault point on the load and the voltage dip degree of the voltage dip fault point.

[0056] The active power change calculation module for new energy sources includes:

[0057] Terminal voltage calculation module, used to calculate the terminal voltage of new energy source based on the voltage drop of the new energy source;

[0058] The new energy active power calculation module is used to calculate the new energy active power during voltage dips under the current power flow mode, based on the relationship between the new energy generator terminal voltage and active current in the new energy low voltage ride-through control strategy.

[0059] The first change calculation module is used to calculate the change in the active power of new energy sources during the voltage dip period under the current power flow mode, based on the active power of new energy sources and the steady-state active power of new energy sources during the voltage dip period under the current power flow mode.

[0060] The load active power change calculation module includes:

[0061] The load voltage calculation module is used to calculate the load voltage based on the degree of voltage drop of the load.

[0062] Load active power calculation module: Based on the relationship between load voltage and active power in the power change characteristics of the load after being disturbed by voltage drop, calculate the load active power during the voltage drop period under the current power flow mode;

[0063] The second change calculation module is used to calculate the change in load active power during the voltage drop period under the current power flow mode, based on the load active power and load steady-state active power during the voltage drop period under the current power flow mode.

[0064] The device also includes a second evaluation module;

[0065] The second evaluation module is used to assess the system's power balance if the short-term energy change of the entire network is less than or equal to the maximum kinetic energy change allowed under the current power flow mode, and the absolute value of the difference between the short-term energy change of the entire network and the maximum kinetic energy change is greater than the maximum kinetic energy change allowed for a single generator already started in the system. In this case, a new power flow mode is obtained by increasing the amount of renewable energy while shutting down traditional generators. Based on the new power flow mode, the renewable energy acceptance capacity is reassessed.

[0066] A computer-readable storage medium storing one or more programs, the one or more programs including instructions that, when executed by a computing device, cause the computing device to perform a renewable energy adoption capacity assessment method.

[0067] The beneficial effects achieved by this invention are as follows: This invention calculates the voltage drop of new energy sources and the voltage drop of loads, and then assesses the short-term energy surge caused by voltage drop, i.e., the change in active power of new energy sources and the change in active power of loads. Combined with the maximum allowable change in kinetic energy of the system, it assesses the current power flow mode as the minimum start-up mode and the maximum capacity to be accommodated. This realizes a method for assessing the new energy acceptance capability in the scenario of short-term power surge caused by voltage drop, and further improves the research on the assessment of new energy acceptance capability under frequency security and stability constraints. Attached Figure Description

[0068] Figure 1 A flowchart for assessing the capacity to accept new energy sources;

[0069] Figure 2A flowchart of the overall methodology for assessing the acceptance capacity of new energy sources;

[0070] Figure 3 This is a schematic diagram of the WSCC 9-node simulation system;

[0071] Figure 4 To assess node voltage for voltage sag;

[0072] Figure 5 The active power response of the load is caused by a voltage dip;

[0073] Figure 6 This is due to the active power response of new energy sources caused by voltage dips. Detailed Implementation

[0074] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0075] like Figure 1 As shown, the assessment method for renewable energy acceptance capacity includes:

[0076] Step 1: Calculate the voltage sag of the new energy source based on the short-circuit current of the new energy source under the current power flow mode, the electrical distance of the new energy source relative to the voltage sag fault point, and the voltage sag degree of the voltage sag fault point.

[0077] The voltage sag of the load is calculated based on the short-circuit current of the load under the current power flow mode, the electrical distance of the load relative to the voltage sag fault point, and the voltage sag degree of the voltage sag fault point.

[0078] Step 2: Based on the voltage drop of the new energy source and the low voltage ride-through control strategy of the new energy source, calculate the change of active power of the new energy source during the voltage drop period under the current power flow mode.

[0079] Based on the degree of voltage drop in the load and the power change characteristics of the load after being disturbed by voltage drop, calculate the change of active power of the load during the voltage drop period under the current power flow mode.

[0080] Step 3: Calculate the short-time energy change of the entire network based on the changes in active power of new energy sources and the changes in active power of loads;

[0081] Step 4: If the short-time energy change of the entire network is less than or equal to the maximum kinetic energy change allowed by the system under the current power flow mode, and the absolute value of the difference between the short-time energy change of the entire network and the maximum kinetic energy change is less than the kinetic energy change of a single generator that has been started in the system under voltage drop disturbance, then the current power flow mode is the minimum start-up mode, and the current renewable energy acceptance capacity is the maximum acceptance capacity under the current start-up mode.

[0082] The above method calculates the voltage drop of new energy sources and the voltage drop of loads, and then assesses the short-term energy surge caused by the voltage drop, i.e., the change in active power of new energy sources and the change in active power of loads. Combined with the maximum allowable change in kinetic energy of the system, it assesses the current power flow mode as the minimum start-up mode and the maximum capacity to be accommodated. This realizes a method for assessing the new energy acceptance capability in the scenario of short-term power surge caused by voltage drop, and further improves the research on the assessment of new energy acceptance capability under frequency security and stability constraints.

[0083] The voltage impact factor reflects the impact of voltage dips on renewable energy sources and loads. Based on the calculation of the voltage impact factor, the voltage dip levels of renewable energy sources and loads can be calculated by measuring the voltage dip levels at fault points.

[0084] Specifically, the voltage impact factor of the voltage sag fault point on the new energy source can be calculated based on the short-circuit current of the new energy source under the current power flow mode and the electrical distance of the new energy source relative to the voltage sag fault point.

[0085] Let the voltage dip fault point k, the renewable energy source i, and the load j be defined. The voltage impact factor of the voltage dip fault point k on the renewable energy source i can be calculated. The specific formula can be expressed as:

[0086]

[0087] Among them, S k-i Let I be the voltage impact factor of voltage drop fault point k on new energy source i. i Z is the short-circuit current of new energy i. ki Let i be the electrical distance of the new energy source i relative to the voltage drop fault point k;

[0088] Then, based on the voltage impact factor of the voltage drop fault point on the new energy source and the voltage drop degree of the voltage drop fault point, the voltage drop degree of the new energy source is calculated:

[0089] The voltage drop degree is the amount of voltage change, specifically the product of the voltage drop fault point's impact factor on the voltage of new energy sources and the voltage drop degree at the fault point. This can be expressed by the formula:

[0090] Δu i =Δu k S k-i

[0091] Where, Δu i The voltage drop of new energy source i, i.e., the change, is Δu. k The voltage drop is the degree of voltage drop at the voltage drop fault point k.

[0092] Based on the voltage sag of renewable energy sources and the low-voltage ride-through control strategy, the change in active power of renewable energy sources during the voltage sag period under the current power flow mode can be calculated. The specific process is as follows:

[0093] 1) Calculate the voltage at the generator terminals of the new energy source based on the voltage drop of the new energy source;

[0094] Based on the calculated Δu i The terminal voltage U of the new energy source can be further calculated. i =U i0 -Δu i U i0 Let i be the initial voltage of the new energy source.

[0095] 2) Based on the relationship between the generator terminal voltage and active current in the low-voltage ride-through control strategy for new energy sources, calculate the active power of new energy sources during the voltage sag under the current power flow mode.

[0096] The low voltage ride-through control strategy for new energy defines the relationship between the terminal voltage and active current of the new energy generator. Combined with the terminal voltage of the new energy generator calculated in 1), the active current of the new energy generator can be obtained, and thus the real-time active power of the new energy during the voltage drop period can be calculated.

[0097] 3) Based on the active power of new energy sources during voltage dips and the steady-state active power of new energy sources under the current power flow mode, calculate the change in active power of new energy sources during voltage dips under the current power flow mode; whereby the change in active power of new energy sources is the steady-state active power minus the active power during voltage dips.

[0098] The change in low-voltage ride-through power of new energy sources caused by voltage dips is a transient power disturbance. The unbalanced electromagnetic power of the synchronous machine is determined by both the system load and the power change of new energy sources. Therefore, it is also necessary to calculate the change in active power of the load.

[0099] Similar to the calculation process for new energy sources, we can first calculate the voltage impact factor of the voltage sag fault point on the load based on the short-circuit current of the load under the current power flow mode and the electrical distance of the load relative to the voltage sag fault point. The specific formula can be expressed as:

[0100]

[0101] Among them, S k-j I is the voltage impact factor of the voltage drop fault point k on the load j. j Z is the short-circuit current of load j. kj Let j be the electrical distance of the load j relative to the voltage drop fault point k;

[0102] Then, based on the voltage impact factor of the voltage dip fault point on the load and the voltage dip degree of the voltage dip fault point, the voltage dip degree of the load is calculated:

[0103] The voltage drop of the load is the product of the voltage impact factor of the voltage drop fault point on the load and the voltage drop degree of the voltage drop fault point, which can be expressed by the formula:

[0104] Δu j =Δu k S k-j

[0105] Where, Δu j The voltage drop of load j is the degree of change.

[0106] Based on the degree of voltage sag, load type, and power change characteristics of the load after being disturbed by voltage sag, the change in active power of the load during the voltage sag under the current power flow mode is calculated. The specific process is as follows:

[0107] 11) Calculate the load voltage based on the degree of voltage drop across the load;

[0108] Based on the calculated Δu j The load voltage U can then be calculated. j =U j0 -Δu j U j0 Let be the initial voltage of load j;

[0109] 12) Based on the relationship between load voltage and active power in the power change characteristics after the load is subjected to voltage dip disturbance, calculate the load active power during the voltage dip under the current power flow mode;

[0110] The power change characteristics define the load type, impedance, load voltage and active power relationship, etc. Combined with the load voltage calculated in 11), the load active power can be obtained.

[0111] 13) Based on the load active power and load steady-state active power during the voltage dip under the current power flow mode, calculate the change in load active power during the voltage dip under the current power flow mode; where the change in load active power is the steady-state active power minus the active power during the voltage dip.

[0112] Based on the changes in active power from new energy sources and changes in active power from loads, the following formula can be used to calculate the short-time energy change of the entire network.

[0113]

[0114] Where ΔW is the short-term energy change of the entire network, t0 is the voltage drop time, t is the voltage recovery time, and ΔP is the voltage drop time.i Let ΔP be the change in active power of new energy source i. j Let be the change in active power of load j, m be the total number of new energy sources in the entire network, and n be the total number of loads in the entire network.

[0115] Simultaneously, based on the system's minimum frequency constraint, the maximum allowable change in kinetic energy under the current power flow mode can be calculated, as shown in the following formula:

[0116]

[0117] Where, ΔE MWs J represents the maximum permissible change in kinetic energy of the system under the current power flow pattern. i1 Let ωi1 be the moment of inertia of the generator rotor, ω0 be the generator speed during stable operation, and ωi be the rotational speed. min N represents the minimum permissible speed during the generator transient process, N represents the total number of generators in operation under the current power flow mode, and M represents the number of generators after they are replaced by new energy sources.

[0118] The assessment of renewable energy acceptance capacity is based on the short-term energy change and maximum kinetic energy change of the entire network, specifically as follows:

[0119] S1) If the short-time energy change of the entire network is less than or equal to the maximum kinetic energy change allowed by the system under the current power flow mode, and the absolute value of the difference between the short-time energy change of the entire network and the maximum kinetic energy change is less than the kinetic energy change of a single generator that has been started in the system under voltage drop disturbance, then the current power flow mode is the minimum start-up mode, and the current renewable energy acceptance capacity is the maximum acceptance capacity under the current start-up mode.

[0120] S2) If the short-time energy change of the entire network is less than or equal to the maximum kinetic energy change allowed by the system under the current power flow mode, and the absolute value of the difference between the short-time energy change of the entire network and the maximum kinetic energy change is greater than the maximum kinetic energy change allowed by a single generator already started in the system, the system power balance is maintained by increasing new energy sources while shutting down traditional generator sets, and a new power flow mode is obtained. The new energy acceptance capacity is reassessed based on the new power flow mode, that is, the assessment starts again from step 1.

[0121] The low-voltage ride-through power change of renewable energy caused by voltage dips is a transient power disturbance. The unbalanced electromagnetic power of the synchronous machine is jointly determined by the system load and renewable energy power changes. From the initial voltage dip, renewable energy active power response, and load power response, as the renewable energy acceptance capacity increases, the voltage dip amplitude, renewable energy active power and load active power changes at different nodes with different renewable energy proportions can be calculated and evaluated. Furthermore, the maximum system frequency deviation can be evaluated, thereby assessing the maximum renewable energy acceptance capacity and minimum start-up mode of the power grid under the system frequency security constraints.

[0122] The rough estimate of the renewable energy acceptance capacity, ignoring the frequency regulation functions of generators and loads, is only applicable to scenarios where power surges recover rapidly after a fault is cleared. If the power surge lasts for a longer period, the frequency regulation functions of conventional units and loads cannot be ignored, and the timing of the system frequency minimum may also be delayed and uncertain. Therefore, a closed-loop control model for system frequency under low-frequency transient power disturbances is required.

[0123] by Figure 3 The simulation system shown is an implementation example, combining the specific process of the above method. Figure 2 An assessment will be conducted.

[0124] The simulation model parameters in the implementation examples include typical conventional thermal power installed capacity and output, generators and their excitation systems, speed governors, power system stabilizer data, AC transmission line parameters, transformer parameters, network interconnection topology, loads using a constant impedance model, and new energy models using typical parameters of a doubly fed wind turbine model.

[0125] The initial power flow configuration is as follows: load 315MW, load model is constant impedance model, renewable energy output 106MW, renewable energy is all doubly-fed wind turbines, 3 conventional units, each with a rated power of 300MW, and each generator's inertial time constant is 2.93s, for a total output of 212MW, denoted as Mode 1; subsequent mode adjustments will be numbered sequentially, i.e., Mode 2, Mode 3, etc. If the load remains unchanged in Mode 2, renewable energy output is increased, 1 conventional power source is decommissioned, and the power supply consists of 2 conventional generator units and 3 renewable energy sources.

[0126] Referring to the accompanying drawings, the specific process of this embodiment is as follows:

[0127] 1) Perform fault scanning based on the current power flow method to obtain voltage drop faults that restrict the system frequency.

[0128] In this embodiment, the fault location is set as a ground fault on the STNA-230 bus. The voltage at node A drops to 0.5 pu for 0.1 s and then immediately recovers to about 1.0 pu.

[0129] 2) Calculate the voltage impact factor of the voltage drop fault point on the new energy source and the voltage impact factor of the voltage drop fault point on the load. Combine the voltage drop degree of the voltage drop fault point to calculate the voltage drop degree of the new energy source and the load.

[0130] Let there be a voltage sag fault point k, a renewable energy source i, and a load node j. Calculate the voltage impact factor of voltage sag fault point k on renewable energy source i as follows:

[0131]

[0132] The voltage drop fault point k is calculated as follows, affecting the voltage of load j:

[0133]

[0134] Among them, S k-i Let I be the voltage impact factor of voltage drop fault point k on new energy source i. i Z is the short-circuit current of new energy i. ki S represents the electrical distance of new energy source i relative to the voltage drop fault point k. k-j I is the voltage impact factor of the voltage drop fault point k on the load j. j Z is the short-circuit current of load j. kj Let j be the electrical distance of the load j relative to the voltage drop fault point k.

[0135] The voltage drop at the voltage sag point is used to assess the voltage sag at other nodes. The voltage change of new energy sources can be simply expressed as: Δu i =Δu k S k-i The terminal voltage can be expressed as: U i =U i0 -Δu i The change in load voltage can be simply expressed as: Δu j =Δu k S k-j The terminal voltage can be expressed as: U j =U j0 -Δu j ; where Δu k For the voltage drop at fault point k, Δu i For the voltage drop of new energy i, Δu j For the voltage drop of load j, U i0 U is the initial voltage of new energy i. j0 Let be the initial voltage of load j.

[0136] In this embodiment, a short-time ground fault at the STNA-230 node causes a voltage drop fault. The equivalent impedance, short-circuit current, and voltage influence factor of the current power flow mode are calculated using power system simulation software, as shown in Table 1.

[0137] Table 1. Voltage Influence Factors for Method 1

[0138]

[0139] In this embodiment, taking the lowest voltage value of node GEN1-230 (referred to as node 1) as an example, the maximum voltage drop of fault node A is Δu. AIf the voltage drop is 0.5 pu and the total duration of the voltage drop is 0.1 s, and it immediately recovers to about 1.0 pu, then the maximum voltage drop at node 1 caused by the voltage drop at fault node A is Δu1 = Δu A S A-1 =0.5 × 0.91536 = 0.458 pu, the initial voltage at node 1 is u 10 =1.0 pu, and the lowest voltage during the voltage sag is u1 = 1 - Δu1 = 1 - 0.458 = 0.542 pu. Therefore, the voltage response of node 1 after being subjected to a voltage sag disturbance is calculated using the above method, and compared with the simulated voltage response curve of node 1. The results are shown in the attached figure. Figure 4 As shown, the results indicate that the node voltage calculated by this invention is highly consistent with the simulated voltage.

[0140] 3) Calculate the change in active power of new energy sources during voltage dips under the current power flow mode.

[0141] Based on the voltage dip of renewable energy sources, combined with the current output level of renewable energy sources and the low-voltage ride-through control strategy, the change in active power of renewable energy sources during the voltage dip period under the current power flow mode can be calculated.

[0142] The voltage drop at node A causes a change in the terminal voltage of the renewable energy unit, and the terminal voltage of the renewable energy unit is strongly correlated with the active power control strategy during the low-voltage ride-through period. In this embodiment, the renewable energy unit adopts the following low-voltage ride-through active power control model, and the power loss area during the low-voltage ride-through period is:

[0143] When t in <t<t out

[0144]

[0145] when

[0146] ΔP i =ΔP t＝tout -γ(tt out )

[0147]

[0148] Where ΔS represents the change in active power of new energy sources during the voltage drop, and ΔP i This represents the change in active power of new energy source i, where P0 is the steady-state active power output before entering the low-voltage breakdown state, I0 is the current value before entering the low-voltage breakdown state, and t is the current value. in To enter the low-voltage ride-through control moment, t out To control the timing of low-altitude penetration, U is the end time of low-power recovery. iI is the current voltage value during low-voltage ride-through. max The maximum current limit for the converter of the new energy unit; k′ represents the reactive current calculation coefficient during the low-voltage period, and γ is the recovery rate of active power during the low-voltage period.

[0149] In this embodiment, the active power control strategy for new energy sources specifies the active current during the fault period as 50% of the initial current before the voltage drop, and the initial recovery power during fault recovery is the actual power during the fault period, with an active power recovery rate of 1.5 MW / s. Using method 2), the voltage response of the new energy source node under voltage drop disturbance is calculated, and the active power is calculated in conjunction with the new energy source low-voltage ride-through control strategy. The calculation results are shown in the attached figure. Figure 5 As shown, the results are basically consistent with the actual simulation results.

[0150] 4) Calculate the change in active power of the load during the voltage drop period under the current power flow mode.

[0151] Based on the voltage dip at the load node, combined with the load type and the power change characteristics of the load after being disturbed by the voltage dip, the change of active power of the load during the voltage dip under the current power flow mode is calculated.

[0152] In this embodiment, the load model is a constant impedance model, so the change in active power of the load during the voltage drop period can be expressed as:

[0153]

[0154] Wherein, ΔP j P represents the change in active power of load j during the voltage dip. j0 Let X be the active power of load j. j S represents the load reactance. k-j Let Δu be the voltage impact factor of the voltage drop fault point k on the load j. k Let be the voltage drop at fault point k.

[0155] In this embodiment, the active power P of the load is calculated. j0 If the voltage is 125MW, and A is the fault voltage drop point, then the voltage influence factor is 1, X j =0.94, calculate the change in active power of the load at the moment when the node voltage drop reaches its maximum of 0.5 pu as ΔP. j =125×(1-0.5×1) 2 / 0.94=33.2MW; the simulation results show a minimum load active power of 35MW. Therefore, the above method is used to calculate the load active power response of the node after a voltage dip disturbance, and the result is compared with the simulated node load active power response curve, as shown in the attached figure. Figure 6As shown, although there are deviations between the load power change assessment under voltage drop conditions proposed in this invention and the actual simulation results, they are highly similar, which demonstrates the correctness of the load power assessment method based on voltage drop proposed in this invention.

[0156] 5) Calculate the short-term energy change of the entire network.

[0157] Calculate the integral of the short-time energy change, i.e., the net power loss, over time for the entire network:

[0158]

[0159] Where ΔW is the short-term energy change of the entire network, t0 is the voltage drop time, t is the voltage recovery time, and ΔP is the voltage drop time. i Let ΔP be the change in active power of new energy source i. j Let be the change in active power of load j, m be the total number of new energy sources in the entire network, and n be the total number of loads in the entire network.

[0160] In this embodiment, based on the estimated active power response curve of the renewable energy source and the active power response curve of the load, and considering the two renewable energy power plants in the current method, the integral of the change in renewable energy active power over the voltage sag time is calculated as follows: P i0 P represents the active power of the new energy source before the voltage drop disturbance. it Let represent the active power at time t after the voltage sag disturbance of each new energy source; the system has three load nodes, so the integral of the change in load active power over the voltage sag time is... P jL0 P represents the active power before the voltage drop disturbance at load j. jLt This represents the active power at time t after the voltage drop disturbance at load j; during the voltage drop period, the short-time energy change of the entire network is ΔW = ΔW1 - ΔW2 = 38 MW·s.

[0161] 6) Based on the minimum frequency constraint of the system, calculate the maximum allowable change in system kinetic energy.

[0162] Based on the system's minimum frequency constraint, the maximum allowable change in kinetic energy is:

[0163]

[0164] Where, ΔE MWs J represents the maximum permissible change in kinetic energy of the system under the current power flow pattern. i1 Let ωi1 be the moment of inertia of the generator rotor, and ω0 be the generator's steady-state operating speed, typically 314 r / s. ω0 = 2πf0. min ω is the minimum permissible speed for the generator transient process. min =2πf minThe specific number of generators is given by the power grid operation requirements. N is the total number of generators in operation under the current power flow mode, and M is the number of generators after they are replaced by new energy sources.

[0165] In this embodiment, the lowest frequency that the system can withstand, 49Hz, is used as the boundary condition for calculating the maximum capacity for accepting new energy sources. The inertial time constant of a single conventional generator is T. j = 2.93s, the capacity of a single conventional generator is S n =300MW, ω0=2×3.14×50=314r / s, ω min =2×3.14×49=307.72r / s, N=3, M=2, the energy provided by the generator when the system is operating stably (system frequency is 50Hz) is E1=3×0.5×2.93×300×(2×3.14×50) 2 / (4×3.14 2 ×3000)=1098.8MW·s, and the energy provided by the generator under the minimum frequency constraint of the system (system frequency is 49Hz) is E2=2×0.5×2.93×300×(2×3.14×49) 2 / (4×3.14 2 (×3000)=703.5MW·s, ΔE=E1-E2=395.3MW·s, so the maximum kinetic energy change that the system can withstand is 395MW·s.

[0166] 7) Compare the net power loss of the entire network with the change in system kinetic energy. If ΔW ≤ ΔE MWs And |ΔE MWs If ΔW| is greater than or equal to the change in kinetic energy of a single generator already running in the system under voltage disturbance, then the system power balance is maintained by increasing new energy sources while shutting down traditional generators, resulting in a new power flow pattern. Based on this new power flow pattern, the new energy acceptance capacity is reassessed, i.e., proceed to 2); if ΔW≤ΔE MWs And |ΔE MWs If -ΔW| is less than the change in kinetic energy of a single generator already started in the system under voltage disturbance, then the current start-up mode is the minimum start-up mode, and the current renewable energy capacity is the maximum capacity under the current start-up mode.

[0167] In this embodiment, the maximum kinetic energy change that the system can withstand is 395 MW·s, and the kinetic energy change of a single generator already started in the system under voltage disturbance is 90 MW·s. The system power supply for Mode 1 consists of 3 conventional generator sets and 2 new energy sources. The estimated ΔW for Mode 1 is approximately 38 MW·s. Since 395 ≥ 38, the maximum allowable change in kinetic energy of the system is greater than or equal to the change in system energy caused by the voltage drop. Furthermore, |395 - 38| = 357 is greater than or equal to the change in kinetic energy of a single generator already started in the system under voltage disturbance. Therefore, the mode is adjusted: the system load remains unchanged, the output of new energy sources is increased, and one conventional power source is shut down. At this time, the power supply consists of 2 conventional generator sets and 3 new energy sources, resulting in Mode 2. Returning to step 2), the above process is continued. The estimated short-term unbalanced energy ΔW for Mode 2 is approximately 230 MW·s. Since 395 ≥ 230, the change in system energy caused by the voltage drop is less than the maximum allowable change in system kinetic energy. Furthermore, |395 - 230| = 165 is greater than or equal to the change in kinetic energy of a single generator already started in the system under voltage disturbance. Continue adjusting the mode as described above to obtain the new current start-up mode, denoted as Mode 3. The power supply consists of one conventional generator set and four new energy sources. ΔW is approximately 550MW·s. 395 < 500, meaning that the voltage drop causes the change in system energy to be greater than the maximum allowable change in kinetic energy of the system. The calculation ends here. The maximum output of the new energy sources accounts for 51% of the load.

[0168] Voltage dips causing low-voltage ride-through power changes in renewable energy sources are transient power disturbances. Without considering primary frequency regulation capabilities, the system's ability to withstand short-term power disturbances from a frequency safety and stability perspective is determined by system inertia. This invention first assesses the total short-term power disturbance energy of the system based on the degree of voltage dips at renewable energy and load nodes after a constraint fault. It then calculates whether the rotor kinetic energy allowed by the system under the current power flow mode is sufficient. If sufficient, it adopts a renewable energy output replacement synchronous start-up method to increase the proportion of renewable energy. This process is iteratively repeated to calculate the minimum start-up mode and the maximum renewable energy integration capacity. From an energy perspective, this invention, based on theoretical calculations, can simply and quickly provide the system's maximum renewable energy capacity and minimum start-up mode, guiding the planning and operation of power grids with a high proportion of renewable energy and promoting the safe consumption of renewable energy.

[0169] Based on the same technical solution, the present invention also discloses a software device for the above method, and a new energy acceptance capacity assessment device, comprising:

[0170] The new energy voltage drop calculation module is used to calculate the voltage drop of the new energy based on the short-circuit current of the new energy under the current power flow mode, the electrical distance of the new energy relative to the voltage drop fault point, and the voltage drop degree of the voltage drop fault point.

[0171] The new energy voltage drop calculation module includes:

[0172] The first voltage impact factor calculation module is used to calculate the voltage impact factor of the voltage drop fault point on the new energy source based on the short-circuit current of the new energy source and the electrical distance of the new energy source relative to the voltage drop fault point under the current power flow mode.

[0173] The first voltage drop calculation module is used to calculate the voltage drop degree of new energy sources based on the voltage impact factor of the voltage drop fault point on the new energy source and the voltage drop degree of the voltage drop fault point.

[0174] The load voltage drop calculation module is used to calculate the load voltage drop based on the load's short-circuit current, the electrical distance of the load relative to the voltage drop fault point, and the voltage drop degree of the voltage drop fault point under the current power flow mode.

[0175] The load voltage drop calculation module includes:

[0176] The second voltage influence factor calculation module is used to calculate the voltage influence factor of the voltage drop fault point on the load based on the short-circuit current of the load and the electrical distance of the load relative to the voltage drop fault point under the current power flow mode.

[0177] The second voltage dip calculation module is used to calculate the voltage dip of the load based on the voltage impact factor of the voltage dip fault point on the load and the voltage dip degree of the voltage dip fault point.

[0178] The active power change calculation module for new energy sources is used to calculate the change in active power of new energy sources during voltage dips under the current power flow mode, based on the voltage dip level of new energy sources and the low voltage ride-through control strategy of new energy sources.

[0179] The active power change calculation module for new energy sources includes:

[0180] Terminal voltage calculation module, used to calculate the terminal voltage of new energy source based on the voltage drop of the new energy source;

[0181] The new energy active power calculation module is used to calculate the new energy active power during voltage dips under the current power flow mode, based on the relationship between the new energy generator terminal voltage and active current in the new energy low voltage ride-through control strategy.

[0182] The first change calculation module is used to calculate the change in the active power of new energy sources during the voltage dip period under the current power flow mode, based on the active power of new energy sources and the steady-state active power of new energy sources during the voltage dip period under the current power flow mode.

[0183] The load active power change calculation module is used to calculate the load active power change during the voltage drop period under the current power flow mode, based on the degree of voltage drop and the power change characteristics of the load after being disturbed by the voltage drop.

[0184] The load active power change calculation module includes:

[0185] The load voltage calculation module is used to calculate the load voltage based on the degree of voltage drop of the load.

[0186] Load active power calculation module: Based on the relationship between load voltage and active power in the power change characteristics of the load after being disturbed by voltage drop, calculate the load active power during the voltage drop period under the current power flow mode;

[0187] The second change calculation module is used to calculate the change in load active power during the voltage drop period under the current power flow mode, based on the load active power and load steady-state active power during the voltage drop period under the current power flow mode.

[0188] The module for calculating short-time energy change across the entire network is used to calculate the short-time energy change across the entire network based on changes in the active power of new energy sources and changes in the active power of the load.

[0189] The first evaluation module is used to determine if the short-term energy change of the entire network is less than or equal to the maximum kinetic energy change allowed by the system under the current power flow mode, and the absolute value of the difference between the short-term energy change of the entire network and the maximum kinetic energy change is less than the kinetic energy change of a single generator that has been started in the system under voltage drop disturbance. In this case, the current power flow mode is the minimum start-up mode, and the current renewable energy capacity is the maximum capacity under the current start-up mode.

[0190] The second evaluation module is used to assess the system's power balance if the short-term energy change of the entire network is less than or equal to the maximum kinetic energy change allowed under the current power flow mode, and the absolute value of the difference between the short-term energy change of the entire network and the maximum kinetic energy change is greater than the maximum kinetic energy change allowed for a single generator already started in the system. In this case, a new power flow mode is obtained by increasing the amount of renewable energy while shutting down traditional generators. Based on the new power flow mode, the renewable energy acceptance capacity is reassessed.

[0191] The data processing flow and methods of each module in the above-mentioned new energy acceptance capacity assessment device are consistent, and will not be described again here.

[0192] Based on the same technical solution, the present invention discloses a computer-readable storage medium storing one or more programs, wherein the one or more programs include instructions that, when executed by a computing device, cause the computing device to perform a new energy acceptance capability assessment method.

[0193] Based on the same technical solution, the present invention discloses a computing device, including one or more processors, one or more memories, and one or more programs, wherein the one or more programs are stored in the one or more memories and configured to be executed by the one or more processors, and the one or more programs include instructions for performing a new energy acceptance capacity assessment method.

[0194] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0195] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0196] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0197] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0198] The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of the claims of the present invention pending approval.

Claims

1. A method for assessing the acceptance capacity of new energy sources, characterized in that, include: The voltage drop of the new energy source is calculated based on the short-circuit current of the new energy source under the current power flow mode, the electrical distance of the new energy source relative to the voltage drop fault point, and the voltage drop degree of the voltage drop fault point. The voltage sag of the load is calculated based on the short-circuit current of the load under the current power flow mode, the electrical distance of the load relative to the voltage sag fault point, and the voltage sag degree of the voltage sag fault point. Based on the voltage drop of the new energy source, calculate the new energy source terminal voltage. Based on the relationship between the new energy source terminal voltage and active current in the new energy source low voltage ride-through control strategy, calculate the new energy source active power during the voltage drop period under the current power flow mode. Based on the new energy source active power during the voltage drop period and the new energy source steady-state active power under the current power flow mode, calculate the change in new energy source active power during the voltage drop period under the current power flow mode. Calculate the load voltage based on the degree of voltage drop of the load. Calculate the load active power during the voltage drop period under the current power flow mode based on the relationship between load voltage and active power in the power change characteristics of the load after being disturbed by voltage drop. Calculate the change in load active power during the voltage drop period under the current power flow mode based on the load active power during the voltage drop period and the load steady-state active power. Calculate the short-time energy change of the entire network based on the changes in active power of new energy sources and the changes in active power of loads; If the short-term energy change of the entire network is less than or equal to the maximum kinetic energy change allowed by the system under the current power flow mode, and the absolute value of the difference between the short-term energy change of the entire network and the maximum kinetic energy change is less than the kinetic energy change of a single generator that has been started in the system under voltage drop disturbance, then the current power flow mode is the minimum start-up mode, and the current renewable energy capacity is the maximum capacity under the current power flow mode. The formula for calculating the short-term energy change of the entire network is as follows: Where ΔW is the short-term energy change of the entire network, t0 is the voltage drop time, t is the voltage recovery time, and ΔP is the voltage drop time. i Let ΔP be the change in active power of new energy source i. j Let be the change in active power of load j, m be the total number of new energy sources in the entire network, and n be the total number of loads in the entire network. The maximum change in kinetic energy is calculated based on the system's lowest frequency constraint, using the following formula: Where, ΔE MWs J represents the maximum permissible change in kinetic energy of the system under the current power flow pattern. i1 Let ωi1 be the moment of inertia of the generator rotor, ω0 be the generator speed during stable operation, and ωi be the rotational speed. min N represents the minimum permissible speed during the generator transient process, N represents the total number of generators in operation under the current power flow mode, and M represents the number of generators after they are replaced by new energy sources.

2. The method for assessing the acceptance capacity of new energy sources according to claim 1, characterized in that, Based on the short-circuit current of the renewable energy source under the current power flow conditions, the electrical distance of the renewable energy source relative to the voltage sag fault point, and the voltage sag degree of the voltage sag fault point, the voltage sag degree of the renewable energy source is calculated, including: Based on the short-circuit current of the renewable energy source and the electrical distance of the renewable energy source relative to the voltage dip fault point under the current power flow mode, calculate the voltage impact factor of the voltage dip fault point on the renewable energy source. The voltage drop degree of new energy sources is calculated based on the voltage impact factor of the voltage drop fault point on the new energy source and the voltage drop degree of the voltage drop fault point.

3. The method for assessing the acceptance capacity of new energy sources according to claim 2, characterized in that, The formula for calculating the voltage impact factor of voltage dip fault points on new energy sources is: Among them, S k-i Let I be the voltage impact factor of voltage drop fault point k on new energy source i. i Z is the short-circuit current of new energy i. ki Let i be the electrical distance of the new energy source i relative to the voltage drop fault point k; The voltage drop of a new energy source is the product of the voltage drop fault point's influence factor on the new energy source's voltage and the voltage drop degree of the fault point.

4. The method for assessing the acceptance capacity of new energy sources according to claim 1, characterized in that, Based on the load's short-circuit current under the current power flow pattern, the electrical distance of the load relative to the voltage dip fault point, and the degree of voltage dip at the voltage dip fault point, calculate the load's voltage dip degree, including: Based on the short-circuit current of the load and the electrical distance of the load relative to the voltage dip fault point under the current power flow mode, calculate the voltage impact factor of the voltage dip fault point on the load. The voltage drop degree of the load is calculated based on the voltage impact factor of the voltage drop fault point on the load and the voltage drop degree of the voltage drop fault point.

5. The method for assessing the acceptance capacity of new energy sources according to claim 4, characterized in that, The formula for calculating the voltage impact factor of a voltage dip fault point on the load is: Among them, S k-j I is the voltage impact factor of the voltage drop fault point k on the load j. j Z is the short-circuit current of load j. kj Let j be the electrical distance of the load j relative to the voltage drop fault point k; The voltage drop of the load is the product of the voltage drop fault point's influence factor on the load's voltage and the voltage drop degree of the fault point.

6. The method for assessing the acceptance capacity of new energy sources according to claim 1, characterized in that, The evaluation method also includes: If the short-term energy change of the entire network is less than or equal to the maximum kinetic energy change allowed by the system under the current power flow mode, and the absolute value of the difference between the short-term energy change of the entire network and the maximum kinetic energy change is greater than the maximum kinetic energy change allowed by a single generator already started in the system, the system power balance is maintained by increasing new energy sources while shutting down traditional generator sets, thus obtaining a new power flow mode. The new energy acceptance capacity is then reassessed based on the new power flow mode.

7. A device for assessing the acceptance capacity of new energy sources, characterized in that, include: The new energy voltage drop calculation module is used to calculate the voltage drop of the new energy based on the short-circuit current of the new energy under the current power flow mode, the electrical distance of the new energy relative to the voltage drop fault point, and the voltage drop degree of the voltage drop fault point. The load voltage dip calculation module is used to calculate the load voltage dip based on the load short-circuit current, the electrical distance of the load relative to the voltage dip fault point, and the voltage dip degree of the voltage dip fault point under the current power flow mode. The new energy active power change calculation module is used to calculate the new energy generator terminal voltage based on the voltage drop degree of the new energy, calculate the new energy active power during the voltage drop period under the current power flow mode based on the relationship between the new energy generator terminal voltage and active current in the new energy low voltage ride-through control strategy, and calculate the new energy active power change during the voltage drop period under the current power flow mode based on the new energy active power during the voltage drop period and the new energy steady-state active power. The load active power change calculation module is used to calculate the load voltage based on the degree of voltage drop of the load, calculate the load active power during the voltage drop period under the current power flow mode based on the relationship between load voltage and active power in the power change characteristics of the load after being disturbed by voltage drop, and calculate the load active power change during the voltage drop period under the current power flow mode based on the load active power during the voltage drop period and the load steady-state active power. The whole network short-time energy change calculation module is used to calculate the whole network short-time energy change based on the changes in active power of new energy sources and the changes in active power of loads; The formula for calculating the short-time energy change of the entire network is: Where ΔW is the short-term energy change of the entire network, t0 is the voltage drop time, t is the voltage recovery time, and ΔP is the voltage drop time. i Let ΔP be the change in active power of new energy source i. j Let be the change in active power of load j, m be the total number of new energy sources in the entire network, and n be the total number of loads in the entire network. The first evaluation module is used to determine if the short-term energy change of the entire network is less than or equal to the maximum kinetic energy change allowed by the system under the current power flow mode, and the absolute value of the difference between the short-term energy change of the entire network and the maximum kinetic energy change is less than the kinetic energy change of a single generator that has been started in the system under voltage drop disturbance. In this case, the current power flow mode is the minimum start-up mode, and the current renewable energy capacity is the maximum capacity under the current start-up mode. The maximum change in kinetic energy is calculated based on the system's lowest frequency constraint, using the following formula: Where, ΔE MWs J represents the maximum permissible change in kinetic energy of the system under the current power flow pattern. i1 Let ωi1 be the moment of inertia of the generator rotor, ω0 be the generator speed during stable operation, and ωi be the rotational speed. min N represents the minimum permissible speed during the generator transient process, N represents the total number of generators in operation under the current power flow mode, and M represents the number of generators after they are replaced by new energy sources.

8. The new energy acceptance capacity assessment device according to claim 7, characterized in that, The new energy voltage drop calculation module includes: The first voltage impact factor calculation module is used to calculate the voltage impact factor of the voltage drop fault point on the new energy source based on the short-circuit current of the new energy source and the electrical distance of the new energy source relative to the voltage drop fault point under the current power flow mode. The first voltage drop calculation module is used to calculate the voltage drop degree of new energy sources based on the voltage impact factor of the voltage drop fault point on the new energy source and the voltage drop degree of the voltage drop fault point.

9. The new energy acceptance capacity assessment device according to claim 7, characterized in that, The load voltage drop calculation module includes: The second voltage influence factor calculation module is used to calculate the voltage influence factor of the voltage drop fault point on the load based on the short-circuit current of the load and the electrical distance of the load relative to the voltage drop fault point under the current power flow mode. The second voltage dip calculation module is used to calculate the voltage dip of the load based on the voltage impact factor of the voltage dip fault point on the load and the voltage dip degree of the voltage dip fault point.

10. The new energy acceptance capacity assessment device according to claim 7, characterized in that, The device also includes a second evaluation module; The second evaluation module is used to assess the system's power balance if the short-term energy change of the entire network is less than or equal to the maximum kinetic energy change allowed under the current power flow mode, and the absolute value of the difference between the short-term energy change of the entire network and the maximum kinetic energy change is greater than the maximum kinetic energy change allowed for a single generator started in the system. In this case, a new power flow mode is obtained by increasing the amount of renewable energy while shutting down traditional generators. Based on the new power flow mode, the renewable energy acceptance capacity is reassessed.

11. A computer-readable storage medium for storing one or more programs, characterized in that, The one or more programs include instructions that, when executed by a computing device, cause the computing device to perform any of the methods according to claims 1 to 6.

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