Offshore wind power bundled multi-type power supply grid-connected sending-out scheme evaluation method and device, electronic equipment and storage medium

Abstract

The invention discloses an offshore wind power bundled multi-type power supply grid-connected sending scheme evaluation method and device, electronic equipment and a storage medium, and belongs to the technical field of electric power system planning. The method comprises the steps that according to a power grid topological structure, a power supply output curve and a line rated thermal stability capacity, when an N-1 fault occurs in a power grid alternating current line, the power supply output curve is calculated; a thermal stability margin corresponding to each sending scheme; calculating a short-circuit current margin corresponding to each sending scheme according to the power grid power flow data and the power grid transient data; calculating the maximum frequency offset corresponding to each sending scheme when the direct current bipolar locking fault occurs; according to the thermal stability margin, the short-circuit current margin and the maximum frequency offset, the evaluation score of each sending scheme is calculated, and the sending scheme with the highest evaluation score is used as the bundling sending scheme of the offshore wind power. The problem of lack of a comprehensive comparison and selection system for multi-type power supply joint sending schemes in the prior art can be solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power system planning, and particularly relates to a method and device for evaluating a sending-out scheme of offshore wind power bundled with multiple types of power sources connected to a grid, an electronic device and a storage medium. BACKGROUND

[0002] With the promotion of the "double carbon" goal, large-scale development of offshore wind power has become a trend. However, offshore wind power has strong volatility and low inertia characteristics, and separate access to the grid can easily cause voltage instability, frequency fluctuation and other problems. At present, offshore wind power is often bundled with thermal power, energy storage and other power sources for sending-out, but different sending-out schemes have significant differences in the impact on grid safety. Existing technologies mostly design evaluation methods for single power source access scenarios, and lack a comprehensive comparison and selection system for joint sending-out schemes of multiple types of power sources. Therefore, it is urgent to propose a comparison and selection method to provide a more scientific basis for optimizing the joint sending-out scheme of large-scale offshore wind power and multiple types of power sources connected to the grid through a flexible DC system. SUMMARY

[0003] The present application provides a method and device for evaluating a sending-out scheme of offshore wind power bundled with multiple types of power sources connected to a grid, an electronic device and a storage medium, which can solve the problem of lack of a comprehensive comparison and selection system for joint sending-out schemes of multiple types of power sources in the prior art.

[0004] To solve the above technical problems, the present application provides a method for evaluating a sending-out scheme of offshore wind power bundled with multiple types of power sources connected to a grid, which comprises:

[0005] Obtaining corresponding grid parameters, wherein the grid parameters include: grid topology structure, power output curve, line rated thermal stability capacity, grid power flow data and grid transient data;

[0006] According to the grid topology structure, power output curve and line rated thermal stability capacity, the actual transmission capacity of the line corresponding to each sending-out scheme when an N-1 fault occurs in the grid AC line is calculated, and then the thermal stability margin corresponding to each sending-out scheme is calculated according to the actual transmission capacity of the line;

[0007] According to the grid power flow data and grid transient data, the three-phase short-circuit current of the grid connection point in each sending-out scheme is calculated, and then the short-circuit current margin corresponding to each sending-out scheme is calculated according to the three-phase short-circuit current;

[0008] The system frequency dynamic response corresponding to each sending-out scheme when a DC bipolar blocking fault occurs is calculated, and then the maximum frequency offset corresponding to each sending-out scheme is calculated according to the system frequency dynamic response;

[0009] According to the thermal stability margin, short-circuit current margin and maximum frequency offset corresponding to each sending scheme, the evaluation score of each sending scheme is calculated, and then the sending scheme with the highest evaluation score is taken as the bundling sending scheme of the offshore wind power.

[0010] As a preferred scheme, the evaluation score of each sending scheme is calculated according to the thermal stability margin, short-circuit current margin and maximum frequency offset corresponding to each sending scheme, which comprises:

[0011] The weight coefficient corresponding to the thermal stability margin, the weight coefficient corresponding to the short-circuit current margin and the weight coefficient corresponding to the maximum frequency offset are obtained.

[0012] According to the thermal stability margin, short-circuit current margin, maximum frequency offset, weight coefficient corresponding to the thermal stability margin, weight coefficient corresponding to the short-circuit current margin and weight coefficient corresponding to the maximum frequency offset corresponding to each sending scheme, the evaluation score of each sending scheme is calculated.

[0013] As a preferred scheme, the thermal stability margin corresponding to each sending scheme is calculated according to the following formula:

[0014]

[0015] Wherein, γ themal is the thermal stability margin corresponding to the sending scheme, S max is the rated thermal stability capacity of the line, S fault is the actual transmission capacity of the line after the fault.

[0016] As a preferred scheme, the short-circuit current margin corresponding to each sending scheme is calculated according to the following formula:

[0017]

[0018] Wherein, λ sc is the short-circuit current margin corresponding to the sending scheme, I limit is the upper limit of the breaking capacity of the circuit breaker, I sc is the actual value of three-phase short-circuit current.

[0019] On the basis of the above-mentioned embodiments, another embodiment of the present application provides a sending scheme evaluation device for offshore wind power bundling multiple types of power sources, comprising: a power grid parameter acquisition module, a thermal stability margin calculation module, a short-circuit current margin calculation module, a maximum frequency offset calculation module and a sending scheme comparison and selection module.

[0020] The power grid parameter acquisition module is used to acquire corresponding power grid parameters; wherein, the power grid parameters comprise: power grid topology, power output curve, rated thermal stability capacity of the line, power grid flow data and power grid transient data.

[0021] The thermal stability margin calculation module is configured to calculate actual transmission capacities of lines corresponding to each power transmission scheme when an N-1 fault occurs in an alternating current line of the power grid according to the power grid topology, power output curves and rated thermal stability capacities of the lines, and then calculate thermal stability margins corresponding to each power transmission scheme according to the actual transmission capacities of the lines.

[0022] The short-circuit current margin calculation module is configured to calculate three-phase short-circuit currents of the grid connection points in each power transmission scheme according to power flow data and transient data of the power grid, and then calculate short-circuit current margins corresponding to each power transmission scheme according to the three-phase short-circuit currents.

[0023] The frequency maximum deviation calculation module is configured to calculate system frequency dynamic responses corresponding to each power transmission scheme when a DC bipolar blocking fault occurs, and then calculate frequency maximum deviations corresponding to each power transmission scheme according to the system frequency dynamic responses.

[0024] The power transmission scheme comparison module is configured to calculate evaluation scores of each power transmission scheme according to the thermal stability margins, the short-circuit current margins and the frequency maximum deviations corresponding to each power transmission scheme, and then select a power transmission scheme with the highest evaluation score as the bundled power transmission scheme of the offshore wind power.

[0025] As a preferred solution, the calculation of the evaluation scores of each power transmission scheme according to the thermal stability margins, the short-circuit current margins and the frequency maximum deviations corresponding to each power transmission scheme includes:

[0026] obtaining a weight coefficient corresponding to the thermal stability margin, a weight coefficient corresponding to the short-circuit current margin and a weight coefficient corresponding to the frequency maximum deviation;

[0027] calculating the evaluation scores of each power transmission scheme according to the thermal stability margins, the short-circuit current margins, the frequency maximum deviations, the weight coefficient corresponding to the thermal stability margin, the weight coefficient corresponding to the short-circuit current margin and the weight coefficient corresponding to the frequency maximum deviation.

[0028] As a preferred solution, the thermal stability margin corresponding to each power transmission scheme is calculated according to the following formula:

[0029]

[0030] wherein γ themal is the thermal stability margin corresponding to the power transmission scheme, S max is the rated thermal stability capacity of the line, S fault is the actual transmission capacity of the line after the fault.

[0031] As a preferred solution, the short-circuit current margin corresponding to each power transmission scheme is calculated according to the following formula:

[0032]

[0033] wherein, λ sc is the short-circuit current margin corresponding to the sending-out scheme, I limit is the upper limit of the breaking capacity of the circuit breaker, I sc is the actual value of the three-phase short-circuit current.

[0034] On the basis of the above-mentioned embodiments, a further embodiment of the application provides an electronic device, which comprises a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, and the processor implements the offshore wind power bundled multi-type power grid-connected sending-out scheme evaluation method of the above-mentioned application embodiments when executing the computer program.

[0035] On the basis of the above-mentioned embodiments, a further embodiment of the application provides a storage medium, which comprises a stored computer program, wherein the device where the storage medium is located executes the offshore wind power bundled multi-type power grid-connected sending-out scheme evaluation method of the above-mentioned application embodiments when the computer program runs.

[0036] Compared with the prior art, the embodiments of the application have the following beneficial effects:

[0037] The application provides an offshore wind power bundled multi-type power grid-connected sending-out scheme evaluation method, which acquires corresponding grid parameters; wherein the grid parameters comprise a grid topology structure, a power output curve, a line rated thermal stability capacity, grid power flow data, and grid transient data;

[0038] According to the grid topology structure, the power output curve, and the line rated thermal stability capacity, the actual transmission capacity of each sending-out scheme corresponding to the line is calculated when N-1 fault occurs in the grid AC line, and then the thermal stability margin corresponding to each sending-out scheme is calculated according to the actual transmission capacity of each line; according to the grid power flow data and the grid transient data, the three-phase short-circuit current of the grid-connected point in each sending-out scheme is calculated, and then the short-circuit current margin corresponding to each sending-out scheme is calculated according to each three-phase short-circuit current; the system frequency dynamic response corresponding to each sending-out scheme is calculated when the DC bipolar blocking fault occurs, and then the maximum frequency offset corresponding to each sending-out scheme is calculated according to each system frequency dynamic response; the evaluation score of each sending-out scheme is calculated according to the thermal stability margin, the short-circuit current margin, and the maximum frequency offset corresponding to each sending-out scheme, and then the sending-out scheme with the highest evaluation score is taken as the bundled sending-out scheme of the offshore wind power.

[0039] The application evaluates the power evacuation capability of different sending schemes by calculating the thermal stability margin, evaluates the short-circuit current level of different sending schemes by calculating the short-circuit current margin, and evaluates the frequency support capability of different sending schemes by calculating the maximum frequency deviation, and then calculates the evaluation score of the different sending schemes of the offshore wind power bundled multi-type power grid connection according to the above three dimensions, thereby providing technical support for the selection of the offshore wind power and multi-type power joint sending scheme, and overcoming the problem of the lack of a comprehensive comparison system for the multi-type power joint sending scheme in the prior art. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 is a flowchart of a sending scheme evaluation method for offshore wind power bundled multi-type power grid connection provided by an embodiment of the application;

[0041] Figure 2 is a frequency change graph of a receiving end power grid under the offshore wind power and different type power bundled sending scheme;

[0042] Figure 3 is a frequency change graph of a receiving end power grid under the offshore wind power and different type power bundled sending scheme;

[0043] Figure 4 is a structural diagram of a sending scheme evaluation device for offshore wind power bundled multi-type power grid connection provided by an embodiment of the application. DETAILED DESCRIPTION

[0044] To make the objectives, technical solutions and advantages of the present application clearer, the technical solutions in the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without any creative work fall within the scope of protection of the present application.

[0045] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present application; the terms "include" and "have" and any variations thereof in the specification and claims of the present application and the above description of drawings are intended to cover non-exclusive inclusion.

[0046] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise specifically limited.

[0047] Reference to“an embodiment” herein means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase“in an embodiment” in various places in the specification are not necessarily referring to the same embodiment, nor are they necessarily mutually exclusive of one another. It is expressly understood that any of the embodiments described herein can be incorporated into any other embodiment.

[0048] In the description of the embodiments of the application, the term“and / or” only means an association relationship of the associated objects, which can mean that there are three relationships, for example, A and / or B, which can mean that A exists alone, A and B exist together, and B exists alone. In addition, the character“ / ” herein generally means that the front and rear associated objects are in an“or” relationship.

[0049] In the description of the embodiments of the application, the terms“a plurality of” and“several” refer to two or more (including two), and similarly, “a plurality of groups” refers to two or more groups (including two groups), and “a plurality of pieces” refers to two or more pieces (including two pieces).

[0050] In the description of the embodiments of the application, unless otherwise explicitly specified and limited, the technical terms“mounting”,“connecting”,“connecting”,“fixing” and the like should be understood in a broad sense, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanical connection, or it can be electrical connection; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the embodiments of the application can be understood according to the specific circumstances.

[0051] Embodiment one

[0052] Please refer to Figure 1 To solve the problem of lack of comprehensive comparison and selection system for joint sending scheme of multiple types of power in the prior art, an embodiment of the application provides a flowchart of an offshore wind power bundling multiple types of power grid-connected sending scheme evaluation method, which includes the following specific steps:

[0053] S1, obtaining corresponding grid parameters; wherein the grid parameters include: grid topology structure, power output curve, line rated thermal stability capacity, grid power flow data and grid transient data;

[0054] Specifically, first, the grid topology structure, power output curve, line rated thermal stability capacity, grid power flow data and grid transient data are obtained.

[0055] S2, according to the power grid topology, power output curve and line rated thermal stability capacity, the actual transmission capacity of the line corresponding to each sending scheme when N-1 fault occurs in the AC line of the power grid is calculated, and then the thermal stability margin corresponding to each sending scheme is calculated according to the actual transmission capacity of each line;

[0056] Preferably, the thermal stability margin corresponding to each sending scheme is calculated according to the following formula:

[0057]

[0058] Wherein, γ themal is the thermal stability margin corresponding to the sending scheme, S max is the rated thermal stability capacity of the line, S fault is the actual transmission capacity of the line after the fault.

[0059] Specifically, after obtaining the power grid parameters, the thermal stability margin after N-1 fault of the AC line is calculated, and the influence of different offshore wind power bundling sending schemes on the line power dissipation capacity is quantified according to the thermal stability margin, which is specifically implemented as follows:

[0060] (1) Input data: power grid topology, power output curve and line thermal stability capacity limit;

[0061] (2) Fault simulation: N-1 fault simulation is performed on the key line, and the post-fault power flow distribution is calculated;

[0062] Exemplarily, in the power system simulation software DSP, N-1 fault is set by commenting out one of the double-circuit lines, and the post-fault power flow distribution is simulated. The power flow calculation can be performed by using the Newton method or the P-Q decomposition method to obtain the post-fault power flow distribution, and the actual transmission capacity of the key line after the fault is the value of the active and reactive power transmission of the line calculated by the power flow calculation. Then the thermal stability margin of the key line is calculated according to the post-fault power flow distribution.

[0063] (3) Margin calculation: after obtaining the actual transmission capacity of the key line after the fault based on the N-1 fault simulation, the margin value can be calculated by using the above thermal stability margin index formula.

[0064] S3, according to the power grid power flow data and the power grid transient data, the three-phase short-circuit current of the grid connection point in each sending scheme is calculated, and then the short-circuit current margin corresponding to each sending scheme is calculated according to each three-phase short-circuit current;

[0065] Preferably, the short-circuit current margin corresponding to each sending scheme is calculated according to the following formula:

[0066]

[0067] Wherein, λsc Isc is the short-circuit current margin corresponding to the sending-out scheme limit Ic is the upper limit of the breaking capacity of the circuit breaker sc Isc is the actual value of the three-phase short-circuit current.

[0068] Specifically, by calculating the short-circuit current margin near the grid-connected point of the offshore wind power, the short-circuit current levels of different schemes are compared and selected according to the short-circuit current margin, and the scheme meeting the equipment safety requirements is screened, which is specifically implemented as follows:

[0069] (1) Short-circuit calculation: the actual value of the three-phase short-circuit current at the grid-connected point is calculated by the symmetrical component method;

[0070] According to the power flow data and transient data of the power grid, the short-circuit current is calculated in the power system simulation software DSP. The transient stability data is a data file containing the transient model of the generator, the flexible HVDC converter model, the line positive, negative and zero sequence model, the load model and other transient models. The PQ, PV and V θ nodes in the power flow file are assigned to the transient model, and the transition process from one stable point to another stable point can be obtained through transient calculation. The transient data is obtained by statistically analyzing the actual generator parameters, line parameters and flexible HVDC converter parameters. According to the power flow data, the impedance from the fault point to each power supply node can be obtained, and according to the transient file, the transient characteristics of each power supply node under short-circuit fault can be obtained. The combination of the two can calculate the short-circuit current.

[0071] (2) Margin evaluation: the short-circuit current margin value is calculated according to the above formula, and the short-circuit current over-standard node is identified.

[0072] The smaller the short-circuit current margin (close to 0 or less than 0), the more likely the short-circuit current will exceed the standard; according to the size of the short-circuit current margin, the short-circuit current levels of different schemes are compared and selected, the larger the margin value, the better the short-circuit current level, and the less likely the short-circuit current will exceed the standard.

[0073] S4, calculating the system frequency dynamic response corresponding to each sending-out scheme when a DC bipolar blocking fault occurs, and then calculating the maximum frequency deviation corresponding to each sending-out scheme according to each system frequency dynamic response;

[0074] Specifically, by calculating the system frequency variation of the receiving end power grid under DC bipolar blocking fault, the frequency support ability of different schemes is compared and selected, and the scheme with strong frequency modulation ability is optimized, which is specifically implemented as follows:

[0075] (1) Fault simulation: set the DC bipolar blocking fault, and calculate the system frequency dynamic response;

[0076] Exemplarily, the DC bipolar blocking fault can be set in the power system simulation software DSP, and the system frequency dynamic response under fault can be calculated through transient simulation.

[0077] (2) Index evaluation: analyze the maximum frequency deviation.

[0078] The essence is the rotor motion equation and the governor (primary frequency regulation link), and the DC bipolar blocking causes a power shortage of the system, and this part of the missing power is first borne by the rotor kinetic energy of the synchronous machine, which will cause the speed to drop, and since there is a certain relationship between the speed and the system frequency (w = 2pf), the system frequency will drop, and the governor detects the frequency deviation of the system, and starts to increase the output power, and when the governor output power is equal to the system frequency shortage, the maximum frequency deviation (i.e. the frequency maximum deviation) is reached. According to the calculated frequency dynamic response curve, the maximum deviation of the system frequency is obtained; the smaller the maximum deviation of the frequency, the stronger the frequency support capability under the scheme.

[0079] S5, according to the thermal stability margin, short-circuit current margin and frequency maximum deviation corresponding to each sending scheme, calculate the evaluation score of each sending scheme, and then take the sending scheme with the highest evaluation score as the bundling sending scheme of the offshore wind power.

[0080] Preferably, the evaluation score of each sending scheme is calculated according to the thermal stability margin, short-circuit current margin and frequency maximum deviation corresponding to each sending scheme, including: obtaining the weight coefficient corresponding to the thermal stability margin, the weight coefficient corresponding to the short-circuit current margin and the weight coefficient corresponding to the frequency maximum deviation; according to the thermal stability margin, the short-circuit current margin, the frequency maximum deviation, the weight coefficient corresponding to the thermal stability margin, the weight coefficient corresponding to the short-circuit current margin and the weight coefficient corresponding to the frequency maximum deviation corresponding to each sending scheme, the evaluation score of each sending scheme is calculated.

[0081] Specifically, the above indexes are weighted and scored by the analytic hierarchy process (AHP), and the strong and weak classification results are formed, which provides a scientific basis for determining the bundling multi-type power sending scheme of offshore wind power. The sending scheme with the highest evaluation score is taken as the bundling sending scheme of offshore wind power, and the specific implementation is as follows:

[0082] (1) From three dimensions (thermal stability margin, short-circuit current margin and frequency maximum deviation), different sending schemes are scored (0-100 points);

[0083] (2) The comprehensive score of each sending scheme is calculated by using the formula, and the comparison result is obtained.

[0084] According to the actual demand of the receiving end power grid of the super large scale offshore wind power sending, a judgment matrix is constructed, and a weight vector is determined, and the comprehensive score formula is:

[0085]

[0086] In the formula, Wp is the AHP weight of the pth index, S p is the normalized score of the scheme under the index.

[0087] In a specific embodiment, the above sending scheme evaluation method is further illustrated based on the data of the 2030 planning of the Southern Power Grid:

[0088] Design scheme one: offshore wind power 6000MW flexible sending; scheme two: offshore wind power 6000MW, island thermal power 3000MW, bundled flexible sending; scheme three: replace the thermal power plant in scheme two with a nuclear power plant; scheme four: offshore wind power 6000MW and interconnected thermal power 3000MW bundled flexible sending scheme; scheme five: replace the thermal power plant in scheme four with a nuclear power plant, and the adaptability evaluation method for offshore wind power and interconnected thermal power bundled sending into the receiving end power grid proposed in the present application is introduced in the specific embodiment.

[0089] (1) AC line N-1 thermal stability margin analysis:

[0090] Under different schemes, the change of the N-1 thermal stability margin of the relevant lines of the receiving end power grid is calculated, as shown in the following Table 1. Then the average value of the AC line N-1 thermal stability margin is taken as the score of the scheme under this dimension.

[0091] Table 1 AC line N-1 thermal stability margin change table under different power source organization schemes

[0092]

[0093]

[0094] (2) Short-circuit current margin analysis:

[0095] Under different schemes, the change of the short-circuit current margin of part of the nodes of the receiving end power grid is calculated, as shown in the following Table 2. Then the average value of the node short-circuit current margin is taken as the score of the scheme under this dimension.

[0096] Table 2 Change table of short-circuit current margin of part of the nodes under different power source organization schemes

[0097]

[0098]

[0099] (3) Frequency support capability analysis:

[0100] Please refer to Figure 2and coating, respectively, the frequency variation chart of the receiving end power grid under the scheme of offshore wind power and different types of power bundled sending out, and the frequency variation chart of the receiving end power grid under the scheme of offshore wind power and different types of power bundled sending out, under different schemes, by using power system calculation and analysis software, setting the bipolar blocking fault of the DC, the frequency variation of the system under different power supply organization schemes is analyzed, and the maximum frequency deviation of the system under different schemes is shown in Table 3 as follows. Then, according to the maximum frequency deviation from small to large, 100 / 90 / 80 / 70 / 60 is assigned in turn.

[0101] Table 3 Maximum frequency deviation of the system under different power supply organization schemes

[0102]

[0103] (4) The comprehensive score of each scheme is calculated by using the analytic hierarchy process:

[0104] From the three dimensions, the scores of different schemes are obtained, and the weight coefficients of the three dimensions are set to 0.3 / 0.3 / 0.4, and the final scores of each scheme are shown in Table 4 as follows.

[0105] Table 4 Comprehensive score of different power supply organization schemes

[0106]

[0107]

[0108] It can be seen that the present application provides a sending out scheme evaluation method for offshore wind power bundled with multiple types of power supply, the present application evaluates the power dissipation capacity of different sending out schemes by calculating the thermal stability margin; the short-circuit current level of different sending out schemes is evaluated by calculating the short-circuit current margin; the frequency support capacity of different sending out schemes is evaluated by calculating the maximum frequency deviation; then, the evaluation score of different sending out schemes for offshore wind power bundled with multiple types of power supply is calculated according to the above three dimensions, which provides technical support for the optimization of offshore wind power and multiple types of power supply joint sending out scheme, and overcomes the problem of lack of comprehensive comparison system for multiple types of power supply joint sending out scheme in the prior art.

[0109] In another specific embodiment, for the above step S2, the specific calculation steps of the power flow calculation by using the Newton-Raphson method or the P-Q decomposition method are as follows:

[0110] I. Power flow calculation steps of Newton-Raphson method (Newton-Lafson method):

[0111] 1. Basic principle: Newton-Raphson method is based on iterative solution of nonlinear equations, by constantly correcting the amplitude and phase angle of voltage phasor, so that the power error converges to the allowable range. The mathematical basis is to perform Taylor expansion of the power equation near the iteration point, and form a linear equation group after ignoring the high-order terms.

[0112] 2. Specific steps:

[0113] Step 1: Establish the mathematical model of the system:

[0114] Node classification:

[0115] PQ node: known injected active power P i and reactive power P i , to be solved voltage amplitude |V i | and phase angle δ i .

[0116] PV node: known P i and |V i |, to be solved δ i and Q i .

[0117] Balancing node: known |V s | and δ s (usually set as the reference node, phase angle is 0), to be solved injected power P s and Q s .

[0118] Power equation: for the i-th node, the active and reactive power expressions are:

[0119] P i = |V i |∑ j＝1n |V j |;

[0120] (Gijcosδij+Bijsinδij)Q i = |V i |∑ j＝1n |V j |(Gijsinδij-Bijcosδij);

[0121] Where δ ij = δ i - δ j , G ij and B ij are the node admittance matrix elements.

[0122] Step 2: Set the initial value:

[0123] Given the initial value of each node voltage: usually |V i |(0) = 1.0 (unit value), δ i(0) = 0 (except for slack bus).

[0124] Step 3: Form Jacobian matrix:

[0125] The iteration equation of Newton-Raphson method is:

[0126] Where:

[0127] ΔP and ΔQ are active and reactive power error vectors;

[0128] Δδ and ΔV are phase angle and voltage magnitude corrections;

[0129] Calculation of Jacobian matrix elements (take J1 as an example):

[0130]

[0131] Step 4: Iterative solution:

[0132] Calculate power error: ΔP i = P iset - P i(k) , ΔQ i = Q iset - Q i(k) ;

[0133] Where P iset and Q iset are given values, P i(k) and Q i(k) are the values calculated in the kth iteration.

[0134] Solve correction equation: solve Δδ and ΔV through Jacobian matrix.

[0135] Update voltage and phase angle: δ i(k+1) = δ i(k) + Δδ i , |V i|(k+1) = |V i | (k) + Δ|V i |;

[0136] Convergence judgment: if |ΔP i |, |ΔQ i | < ε (error threshold, such as 10-5), the iteration ends; otherwise, return to step 4.

[0137] Step 5: Calculate the power of the slack bus and the reactive power of the PV node:

[0138] Slack bus power: P s = ∑ i＝1n Piinjected (system power balance).

[0139] PV node reactive power: Q i = Q i(k+1) (value after iteration converges).

[0140] II. P-Q decomposition method power flow calculation steps:

[0141] 1. Basic principle:

[0142] P-Q decomposition method is a simplified form of Newton-Raphson method, based on the characteristics of high voltage power grid resistance R << reactance X (i.e. G << B) and voltage phase angle difference δ is small, the Jacobian matrix of Newton-Raphson method is decomposed into active-angle and reactive-voltage two independent iteration equations, reducing the amount of calculation and storage.

[0143] 2. Specific steps:

[0144] Step 1: Simplify power equation and iteration equation:

[0145] Approximate conditions:

[0146] G ij ≈0, i.e. ignore the conductance, only consider the susceptance B ij ;

[0147] cosδ ij ≈1, sinδ ij ≈δ ij (when δ is small).

[0148] Decomposed iteration equation: ΔP = B' Δδ ΔQ = B" ΔV / V; where B' and B" are the simplified coefficient matrix (usually constant matrix, only related to network structure).

[0149] Step 2: Set initial value: same as Newton-Raphson method, usually |V i |(0) = 1.0, δ i (0) = 0 (except for the equilibrium node).

[0150] Step 3: Iterative solution (active and reactive iteration)

[0151] Active-angle iteration: calculate active power error ΔP; solve Δδ = (B') -1 ΔP; update phase angle: δ i(k+1) = δ i(k) + Δδ i .

[0152] Reactive-voltage iteration: calculate reactive power error ΔQ; solve ΔV / V = (B") -1 ΔQ; update voltage amplitude: |V i |(k+1) = |V i (k) + Δ |V i .

[0153] Step 4: Alternately iterate until convergence: Alternately iterate active- phase angle and reactive- voltage iteration until power error satisfies | ΔP i |, | ΔQ i | < ε.

[0154] Step 5: Calculate equilibrium node power and PV node reactive power: After iteration convergence, calculate equilibrium node power and PV node reactive power as in Newton-Raphson method.

[0155] III. Comparison between Newton-Raphson method and P-Q decomposition method:

[0156]

[0157] Table 1 Comparison between Newton-Raphson method and P-Q decomposition method

[0158] In another specific embodiment, for the above step S3, the specific calculation steps of calculating the actual value of the three-phase short-circuit current of the grid-connected point by using the symmetrical component method are as follows:

[0159] Short-circuit current calculation:

[0160] Using the node equation for fault calculation, it is necessary to form the node admittance (or impedance) matrix of the system. The IEC60909 document has detailed provisions for the impedance calculation of each element of the power system, and its characteristics are that the calculation items are more, the concept is clear, the impedance correction is scientific, and the calculation result is relatively conservative. The IEC standard provides that, except for the zero sequence system, all line capacitances, shunt admittances, and non-rotating type loads are ignored, and both remote and near short circuits can be calculated by using the equivalent voltage source to calculate the short-circuit current.

[0161] For a network in normal state, the short circuit is equivalent to adding an injection current at the fault node f. Therefore, the voltage of any node i in the network can be expressed as:

[0162]

[0163] In the formula, Z ij is the mutual impedance between node i and node j, and Z ir is the mutual impedance between node i and fault node f after adding the ground impedance. As can be seen from formula (1), the voltage of any node voltage i is superimposed by two terms. The first term is the voltage generated by all power sources in the network at node i when I f = 0, that is, the node voltage in the normal operating state before the short circuit, denoted as ​The second term is that when all current sources in the network are disconnected and potential sources are short-circuited, only the short-circuit current— The voltage generated at node i. The superposition of these two components equals the actual voltage at node i after the short circuit, that is:

[0164]

[0165] Formula (2) also applies to the faulty node f, so we have:

[0166]

[0167] Z ff It is the self-impedance of the fault node f, also known as the input impedance. Equation (3) contains two unknowns. and Based on the fault boundary conditions, we can obtain:

[0168]

[0169] Solving from formulas (3) and (4):

[0170]

[0171] It should be noted that when considering asynchronous power sources such as flexible DC power and new energy units, the above formula needs to be modified as follows:

[0172]

[0173] Where V △Is The fault point voltage is caused by the change in current source ΔIs after the fault, and can be obtained using the formula YU=I, where Y is the admittance matrix, I is the node injected current vector, and U is the node voltage vector. Unless otherwise specified, the short-circuit currents mentioned in this article are all short-circuit currents under three-phase short-circuit faults.

[0174] In the DSP software of China Southern Power Grid, the calculation principle for short-circuit current is as follows:

[0175] (1) Consider static load (using equivalent impedance model);

[0176] (2) Consider parallel reactive power compensation;

[0177] (3) Consider the line charging power;

[0178] (4) Consider flexible DC systems;

[0179] (5) Consider the contribution of new energy sources;

[0180] (6) Consider STATCOM contributions;

[0181] (7) Short circuit voltage coefficient is 1.08 pu.

[0182] Embodiment two

[0183] Please refer to Figure 4 A structure schematic diagram of a sending scheme evaluation device for offshore wind power bundling multi-type power supply grid connection is provided in an embodiment of the present application, and the device comprises: a power grid parameter acquisition module, a thermal stability margin calculation module, a short circuit current margin calculation module, a frequency maximum offset calculation module and a sending scheme comparison and selection module.

[0184] The power grid parameter acquisition module is used to acquire corresponding power grid parameters; wherein the power grid parameters comprise: power grid topology structure, power supply output curve, line rated thermal stability capacity, power grid flow data and power grid transient data;

[0185] The thermal stability margin calculation module is used to calculate the actual transmission capacity of the line corresponding to each sending scheme when N-1 fault occurs in the AC line of the power grid according to the power grid topology structure, power supply output curve and line rated thermal stability capacity, and then calculate the thermal stability margin corresponding to each sending scheme according to the actual transmission capacity of the line;

[0186] The short circuit current margin calculation module is used to calculate the three-phase short circuit current of the grid connection point in each sending scheme according to the power grid flow data and power grid transient data, and then calculate the short circuit current margin corresponding to each sending scheme according to the three-phase short circuit current;

[0187] The frequency maximum offset calculation module is used to calculate the system frequency dynamic response corresponding to each sending scheme when DC bipolar blocking fault occurs, and then calculate the frequency maximum offset corresponding to each sending scheme according to the system frequency dynamic response;

[0188] The sending scheme comparison and selection module is used to calculate the evaluation score of each sending scheme according to the thermal stability margin, short circuit current margin and frequency maximum offset corresponding to each sending scheme, and then take the sending scheme with the highest evaluation score as the bundling sending scheme of offshore wind power.

[0189] Preferably, the calculation of the evaluation score of each sending scheme according to the thermal stability margin, short circuit current margin and frequency maximum offset corresponding to each sending scheme comprises:

[0190] acquiring the weight coefficient corresponding to the thermal stability margin, the weight coefficient corresponding to the short circuit current margin and the weight coefficient corresponding to the frequency maximum offset;

[0191] According to the thermal stability margin, the short-circuit current margin, the maximum frequency offset, the weight coefficient corresponding to the thermal stability margin, the weight coefficient corresponding to the short-circuit current margin and the weight coefficient corresponding to the maximum frequency offset of each sending scheme, the evaluation score of each sending scheme is calculated.

[0192] Preferably, the thermal stability margin corresponding to each sending scheme is calculated according to the following formula:

[0193]

[0194] Wherein, γ themal is the thermal stability margin corresponding to the sending scheme, S max is the rated thermal stability capacity of the line, S fault is the actual transmission capacity of the line after the fault.

[0195] Preferably, the short-circuit current margin corresponding to each sending scheme is calculated according to the following formula:

[0196]

[0197] Wherein, λ sc is the short-circuit current margin corresponding to the sending scheme, I limit is the upper limit of the breaking capacity of the circuit breaker, I sc is the actual value of three-phase short-circuit current.

[0198] It should be noted that the device embodiments described above are only schematic, wherein the units described as separate components can or can not be physically separated, and the components displayed as units can or can not be physical units, i.e. they can be located in one place, or distributed on multiple network units. Part or all of the modules can be selected to achieve the purpose of the embodiment according to actual needs. In addition, the connection relationship between the modules in the device embodiment provided by the present application indicates that there is a communication connection between them, which can be realized as one or more communication buses or signal lines. Those skilled in the art can understand and implement it without creative labor.

[0199] Those skilled in the art can clearly understand that, in order to facilitate and be brief, the specific working process of the device described above can refer to the corresponding process in the foregoing method embodiment, which will not be described here.

[0200] Embodiment three

[0201] Correspondingly, the embodiment of the present application provides an electronic device, the device comprising a processor, a memory and a computer program stored in the memory and configured to be executed by the processor, the processor implementing the offshore wind power bundling multi-type power grid-connected sending scheme evaluation method when executing the computer program.

[0202] The electronic device can be a desktop computer, a notebook computer, a palm computer, a cloud server and the like. The device can include but is not limited to a processor and a memory.

[0203] The processor can be a central processing unit (CPU), and can also be other general-purpose processors, digital signal processors (DSP), application specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor and the like. The processor is the control center of the device, and connects all parts of the device through various interfaces and lines.

[0204] Embodiment four

[0205] Correspondingly, the embodiment of the present application provides a storage medium, the storage medium comprising a stored computer program, wherein the computer program controls the device where the storage medium is located to execute the offshore wind power bundling multi-type power grid-connected sending scheme evaluation method when the computer program is running.

[0206] The memory can be used to store the computer program, and the processor realizes various functions of the device by running or executing the computer program stored in the memory, and calling data stored in the memory. The memory can mainly include a program storage area and a data storage area, wherein the program storage area can store an operating system, at least one application required by a function and the like; the data storage area can store data created according to the use of the mobile phone and the like. In addition, the memory can include a high-speed random access memory, and can also include a non-volatile memory, for example, a hard disk, a memory, a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, at least one disk storage device, a flash memory device, or other volatile solid-state memory device.

[0207] The storage medium is a computer readable storage medium, and the computer program is stored in the computer readable storage medium. When the computer program is executed by a processor, the steps of each method embodiment described above can be implemented. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or some intermediate forms, etc. The computer readable medium can include any entity or device capable of carrying the computer program code, recording medium, U disk, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signal, telecommunication signal, and software distribution medium, etc. It should be noted that the content included in the computer readable medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction, for example, in some jurisdictions, according to legislation and patent practice, the computer readable medium does not include electrical carrier signals and telecommunication signals.

[0208] The above is the preferred embodiment of the present application. It should be noted that for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, which are also considered within the scope of protection of the present application.

Claims

1. A method for evaluating transmission schemes of offshore wind power bundled with multiple types of power sources for grid connection, characterized in that, include: Obtain the corresponding power grid parameters; wherein, the power grid parameters include: power grid topology, power output curves, line rated thermal stability capacity, power grid power flow data, and power grid transient data; Based on the power grid topology, power output curves, and line rated thermal stability capacity, calculate the actual transmission capacity of each transmission scheme when an N-1 fault occurs on the AC power grid line. Then, based on the actual transmission capacity of each line, calculate the thermal stability margin of each transmission scheme. Based on the power flow data and power transient data, the three-phase short-circuit current at the grid connection point in each transmission scheme is calculated, and then the short-circuit current margin corresponding to each transmission scheme is calculated based on the three-phase short-circuit current. Calculate the system frequency dynamic response corresponding to each transmission scheme when a DC bipolar blocking fault occurs, and then calculate the maximum frequency offset corresponding to each transmission scheme based on the system frequency dynamic response. Based on the thermal stability margin, short-circuit current margin, and maximum frequency offset of each transmission scheme, the evaluation score of each transmission scheme is calculated, and then the transmission scheme with the highest evaluation score is selected as the bundled transmission scheme for offshore wind power.

2. The evaluation method for the transmission scheme of offshore wind power bundling and grid connection of multiple types of power sources as described in claim 1, characterized in that, The evaluation score for each transmission scheme is calculated based on its corresponding thermal stability margin, short-circuit current margin, and maximum frequency offset, including: Obtain the weighting coefficients corresponding to thermal stability margin, short-circuit current margin, and maximum frequency offset; The evaluation score for each transmission scheme is calculated based on the thermal stability margin, short-circuit current margin, maximum frequency offset, weighting coefficient corresponding to the thermal stability margin, weighting coefficient corresponding to the short-circuit current margin, and weighting coefficient corresponding to the maximum frequency offset.

3. The evaluation method for the transmission scheme of offshore wind power bundling and grid connection of multiple types of power sources as described in claim 1, characterized in that, Calculate the thermal stability margin for each delivery scheme using the following formula: Where, γ themal To provide the thermal stability margin corresponding to the delivery scheme, S max The rated thermal stability capacity S of the line fault This represents the actual transmission capacity of the line after the fault.

4. The evaluation method for the transmission scheme of offshore wind power bundling and grid connection of multiple types of power sources as described in claim 1, characterized in that, Calculate the short-circuit current margin for each power transmission scheme using the following formula: Where, λ sc For the short-circuit current margin of the power supply scheme, I limit I is the upper limit of the circuit breaker's breaking capacity. sc This represents the actual value of the three-phase short-circuit current.

5. An evaluation device for a transmission scheme of offshore wind power bundling multiple types of power sources for grid connection, characterized in that, include: The module includes a power grid parameter acquisition module, a thermal stability margin calculation module, a short-circuit current margin calculation module, a maximum frequency offset calculation module, and a transmission scheme comparison and selection module. The power grid parameter acquisition module is used to acquire corresponding power grid parameters; wherein, the power grid parameters include: power grid topology, power output curve, line rated thermal stability capacity, power grid power flow data, and power grid transient data; The thermal stability margin calculation module is used to calculate the actual transmission capacity of each transmission scheme when an N-1 fault occurs in the AC line of the power grid, based on the power grid topology, power output curve and line rated thermal stability capacity, and then calculate the thermal stability margin of each transmission scheme based on the actual transmission capacity of each line. The short-circuit current margin calculation module is used to calculate the three-phase short-circuit current at the grid connection point in each transmission scheme based on the power flow data and power transient data, and then calculate the short-circuit current margin corresponding to each transmission scheme based on the three-phase short-circuit current. The maximum frequency offset calculation module is used to calculate the dynamic response of the system frequency corresponding to each transmission scheme when a DC bipolar blocking fault occurs, and then calculate the maximum frequency offset corresponding to each transmission scheme based on the dynamic response of the system frequency. The transmission scheme comparison module is used to calculate the evaluation score of each transmission scheme based on the thermal stability margin, short-circuit current margin and maximum frequency offset of each transmission scheme, and then select the transmission scheme with the highest evaluation score as the bundled transmission scheme for offshore wind power.

6. The evaluation device for the transmission scheme of offshore wind power bundling and grid connection of multiple types of power sources as described in claim 5, characterized in that, The evaluation score for each transmission scheme is calculated based on its corresponding thermal stability margin, short-circuit current margin, and maximum frequency offset, including: Obtain the weighting coefficients corresponding to thermal stability margin, short-circuit current margin, and maximum frequency offset; The evaluation score for each transmission scheme is calculated based on the thermal stability margin, short-circuit current margin, maximum frequency offset, weighting coefficient corresponding to the thermal stability margin, weighting coefficient corresponding to the short-circuit current margin, and weighting coefficient corresponding to the maximum frequency offset.

7. The evaluation device for the transmission scheme of offshore wind power bundling and grid connection of multiple types of power sources as described in claim 5, characterized in that, Calculate the thermal stability margin for each delivery scheme using the following formula: Where, γ themal To provide the thermal stability margin corresponding to the delivery scheme, S max S is the rated thermal stability capacity of the line. fault This represents the actual transmission capacity of the line after the fault.

8. The evaluation device for the transmission scheme of offshore wind power bundling and grid connection of multiple types of power sources as described in claim 5, characterized in that, Calculate the short-circuit current margin for each power transmission scheme using the following formula: Where, λ sc For the short-circuit current margin of the power supply scheme, I limit I is the upper limit of the circuit breaker's breaking capacity. sc This represents the actual value of the three-phase short-circuit current.

9. An electronic device, characterized in that, The system includes a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein the processor executes the computer program to implement the evaluation method for grid connection of offshore wind power bundled with multiple types of power sources as described in any one of claims 1 to 4.

10. A storage medium, characterized in that, The storage medium includes a stored computer program, wherein, when the computer program is running, it controls the device where the storage medium is located to execute the evaluation method for the grid connection of multiple types of offshore wind power bundled as described in any one of claims 1 to 4.

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