Method and device for calculating harmonic impedance sensitivity of power system

Abstract

The invention relates to a power system harmonic impedance sensitivity calculation method and device, and the method comprises the steps: obtaining a network topology structure of a power system, and constructing a harmonic node voltage solving equation in the power system according to the network topology structure of the power system; constructing a harmonic impedance sensitivity calculation equation in the power system according to a solving result of the harmonic node voltage solving equation; and according to a calculation result of the harmonic impedance sensitivity calculation equation, obtaining a harmonic minimum operation direction of the current operation working point position. According to the method, by sorting the AC power grid-new energy station nodes and generating the block matrix, the equation solving efficiency is improved; a complete harmonic sensitivity calculation system is established, and the precision of a solving result is improved; and the harmonic wave minimum operation direction is searched near the current working point by calculating the maximum value of the harmonic wave sensitivity, so that the safe and stable operation of the power system is ensured.

Description

Technical Field

[0001] The present application relates to the technical field of power system monitoring, and in particular to a method and device for calculating harmonic impedance sensitivity of a power system. Background Art

[0002] As the proportion of new energy generation devices and power electronic equipment in power systems gradually increases, the harmonic problem of power systems has become increasingly prominent. Due to the nonlinear characteristics of harmonic sources and the changes in the complex topological structure of the power grid, harmonic impedance has become an important factor affecting the harmonic characteristics and stability of the power system. Harmonic impedance reflects the response characteristics of the power system to harmonics of different frequencies, and its parameter changes are directly related to the amplification effect and resonance phenomenon of the power system harmonics. In complex power systems, harmonic impedance has significant time-varying and nonlinear characteristics. The impedance values ​​of harmonics of different frequencies are not only affected by the operating state of the system, but also closely related to equipment parameters and network topology. Due to the accurate calculation of harmonic impedance sensitivity, the response law of system harmonic characteristics to parameter changes can be revealed, providing theoretical support for harmonic suppression and system optimization design. However, most of the existing calculation methods of harmonic impedance sensitivity rely on complex mathematical models and a large number of simulation calculations, which cannot take into account both calculation accuracy and efficiency. And with the development of new power systems, the diversification and dynamic characteristics of power grid structures have aggravated the complexity of sensitivity analysis, which has greatly reduced the calculation accuracy and efficiency of harmonic impedance sensitivity in power systems. Summary of the invention

[0003] In order to overcome the above-mentioned deficiencies of the prior art, the present application provides a method and device for calculating harmonic impedance sensitivity of a power system, which specifically adopts the following technical solutions:

[0004] A method for calculating harmonic impedance sensitivity of a power system comprises the following steps:

[0005] Obtain the network topology of the power system, and construct the harmonic node voltage solution equation in the power system according to the network topology of the power system;

[0006] According to the solution results of the harmonic node voltage solution equation, the harmonic impedance sensitivity calculation equation in the power system is constructed;

[0007] According to the calculation result of the harmonic impedance sensitivity calculation equation, the harmonic minimum operating direction of the current operating point position is obtained.

[0008] Optionally: the step of constructing a harmonic node voltage solution equation in the power system according to the network topology of the power system includes:

[0009] Obtain the order of each harmonic node in the network topology and the harmonic current of each branch; wherein the order of each harmonic node in the network topology is the grid connection point where the AC power grid is connected to the new energy station - the connection node directly connected to the grid connection point - the high-voltage side node of the new energy station step-up transformer;

[0010] Establish the corresponding harmonic node admittance matrix according to the order of each harmonic node in the network topology;

[0011] The node voltage equations of each harmonic node are established respectively, and the harmonic voltage of each harmonic node in the power system is obtained by combining the harmonic node admittance matrix and the harmonic current calculation of each branch.

[0012] Optionally: the node voltage equation adopts the harmonic node voltage equation after matrix block division:

[0013]

[0014] where Y Grid Admittance unit containing only the impedance of the onshore power grid; Y Line is an admittance unit containing only the series admittance of the transmission line; Y Line The transpose of Y REs is a diagonal matrix, and the diagonal elements are the frequency domain equivalent self-admittance of the new energy station; I Grid is the background harmonic current on the grid side; I REs is the background harmonic current on the renewable energy side; U Grid is the grid-side node harmonic voltage; U REs It is the harmonic voltage of the node on the new energy side.

[0015] Optionally: When the harmonic voltage of each harmonic node in the power system is obtained by combining the harmonic node admittance matrix and the harmonic current of each branch, the inverse matrix of the harmonic node admittance matrix and the node injection harmonic column vector are used to obtain the corresponding node harmonic voltage column vector, and the corresponding calculation method includes:

[0016]

[0017] Among them U h is the node harmonic voltage column vector; is the inverse matrix of the harmonic node admittance matrix; I h Injects a harmonic column vector into a node.

[0018] Optionally: the step of constructing a harmonic impedance sensitivity calculation equation in a power system includes:

[0019] Obtain the harmonic voltage and harmonic current of each harmonic node in the power system;

[0020] Calculate the sensitivity of the harmonic voltage to the admittance change at each harmonic node in the power system;

[0021] Calculate the sensitivity of the harmonic current of each harmonic node in the power system to the change of admittance;

[0022] Calculate the sensitivity of the harmonic voltage of each harmonic node in the power system to the background harmonic source;

[0023] The sensitivity of the harmonic current of each harmonic node in the power system to the background harmonic source is calculated.

[0024] Optionally: the step of calculating the sensitivity of the harmonic voltage of each harmonic node in the power system to the change in admittance includes:

[0025] A first calculation equation for the sensitivity of harmonic voltage to admittance change is constructed, wherein the first calculation equation is obtained based on the node injection harmonic column vector, the harmonic node admittance matrix and the first matrix, wherein the first matrix is ​​a square matrix of the same order as the harmonic node admittance matrix, and the elements in the i-th row and j-th column of the square matrix are 1, and the remaining elements are 0; specifically, the first calculation equation is:

[0026]

[0027] Where S Vh is the sensitivity of harmonic voltage to admittance change; Y h is the harmonic node admittance matrix; I h Inject harmonic column vector into the node; U h is the node harmonic voltage column vector; Y ij is the admittance element of the i-th row and j-th column of the harmonic node admittance matrix; E h For a h A square matrix of the same order, with the element in the i-th row and j-th column being 1 and the rest being 0;

[0028] When calculating the admittance sensitivity of the AC grid side admittance unit, the admittance sensitivity of the new energy side admittance unit, and the admittance sensitivity of the transmission line admittance unit, the positions of the admittance elements in the first matrix are different. Grid When the admittance sensitivity is h It is expressed as:

[0029]

[0030] When calculating the new energy side admittance unit Y REs When the admittance sensitivity is h It is expressed as:

[0031]

[0032] When calculating the transmission line admittance unit Y Line When the admittance sensitivity is h It is expressed as:

[0033]

[0034] or E h It is expressed as:

[0035]

[0036] Optionally: the step of calculating the sensitivity of the harmonic current of each harmonic node in the power system to the change in admittance includes:

[0037] A second calculation equation for the sensitivity of harmonic current to admittance change is constructed, wherein the second calculation equation is obtained based on the admittance elements of the harmonic node admittance matrix and the harmonic voltages corresponding to the admittance elements, wherein the second calculation equation is:

[0038]

[0039] Where S Ih is the sensitivity of harmonic current to admittance change; I ij is the harmonic current flowing through the line between node i and node j; Y ij is the admittance element of the i-th row and j-th column of the harmonic node admittance matrix; U i is the harmonic voltage at node i; U j is the harmonic voltage at node j;

[0040] When the derived admittance element is not directly related to the admittance element of the harmonic node admittance matrix, the sensitivity of the harmonic current to the admittance matrix is ​​obtained by the harmonic voltage corresponding to the admittance element in the harmonic node admittance matrix. ij When not directly related, the sensitivity of harmonic current to the admittance matrix is:

[0041] S Ih =Y ij (S Vh (i)-S Vh (j));

[0042] Where S Vh is the sensitivity of harmonic voltage to admittance change; S Vh (i) represents the vector S Vh The i-th element of is the sensitivity of the harmonic voltage at node i to the change in admittance; S Vh (j) represents the vector S Vh The jth element of is the sensitivity of the harmonic voltage at node j to the change of admittance;

[0043] When calculating the sensitivity of harmonic current to the change of the overall admittance of the onshore power grid, the sensitivity of harmonic current to the admittance matrix is ​​obtained by the harmonic voltage corresponding to the admittance element in the harmonic node admittance matrix and the sensitivity of harmonic voltage to the admittance change. That is, the sensitivity of harmonic current to the admittance matrix is:

[0044] S Ih =Y ij (S Vh (i)-S Vh (j))-U i +U j .

[0045] Optionally: the step of calculating the sensitivity of the harmonic voltage of each harmonic node in the power system to the background harmonic source includes:

[0046] A third calculation equation for the sensitivity of the harmonic voltage to the background harmonic source is constructed, wherein the third calculation equation is obtained based on the admittance element of the inverse matrix of the harmonic node admittance matrix, wherein the third calculation equation is:

[0047]

[0048] Where S VI is the sensitivity of harmonic voltage to background harmonic source; is the inverse matrix of the harmonic node admittance matrix, U i is the node voltage of node i; represents the admittance element of the i-th row and j-th column of the inverse matrix of the harmonic node admittance matrix;

[0049] The node voltage U of node i is i The calculation equation is:

[0050]

[0051] Where I j is the injected harmonic current of node j, and n is the number of nodes in the grid-connected system.

[0052] Optionally: the step of calculating the sensitivity of the harmonic current of each harmonic node in the power system to the background harmonic source includes:

[0053] A fourth calculation equation for the sensitivity of harmonic current to background harmonic sources is constructed. The fourth calculation equation is obtained based on the harmonic node admittance matrix and the admittance elements of the corresponding inverse matrix. The fourth calculation equation is:

[0054]

[0055] Where S Ieis the sensitivity of harmonic current to background harmonic current source; Represents the admittance element in the i-th row and j-th column of the inverse matrix of the harmonic node admittance matrix.

[0056] Optionally, the step of obtaining the harmonic minimum operating direction of the current operating point position according to the calculation result of the harmonic impedance sensitivity calculation equation includes:

[0057] Select the maximum value of the sensitivity amplitude in the calculation result of the harmonic impedance sensitivity calculation equation as the best control variable of the harmonic;

[0058] When the imaginary part of the optimal control variable is positive, the harmonic minimum operation direction is the direction in which the optimal control variable decreases;

[0059] When the imaginary part of the optimal control variable is negative, the harmonic minimum operating direction is the direction in which the optimal control variable increases.

[0060] Furthermore, the present application also discloses a device for calculating harmonic impedance sensitivity of a power system, the device comprising:

[0061] A node voltage solving module is used to obtain the network topology of the power system and construct a harmonic node voltage solving equation in the power system according to the network topology of the power system;

[0062] A sensitivity calculation module is used to construct a harmonic impedance sensitivity calculation equation in the power system according to the solution result of the harmonic node voltage solution equation;

[0063] The harmonic direction judgment module is used to obtain the minimum harmonic running direction of the current running working point according to the calculation result of the harmonic impedance sensitivity calculation equation.

[0064] Beneficial Effects

[0065] The technical solution of this application has the following beneficial effects:

[0066] The power system harmonic impedance sensitivity calculation method of the present application improves the efficiency of equation solving by sorting the nodes of the AC power grid-new energy station order and generating a block matrix when solving the harmonic node voltage; and when calculating the harmonic impedance sensitivity, it covers the sensitivity calculation of harmonic voltage and harmonic current to each element of the node voltage equation, and establishes a complete harmonic sensitivity calculation system to improve the accuracy of the solution result; and then by calculating the maximum value of the harmonic sensitivity, the minimum harmonic operating direction is found near the current working point, thereby ensuring the safe and stable operation of the power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 This is a flow chart of a method for calculating harmonic impedance sensitivity of a power system in this application.

[0068] Figure 2 This is a topology diagram of the new energy grid-connected system in the embodiment of the present application; RES represents a new energy station, and SVG represents a static synchronous generator.

[0069] Figure 3 It is the frequency domain admittance model of the new energy grid-connected system in the embodiment of the present application.

[0070] Figure 4 It is a time domain simulation diagram of the current operating point of the working condition 1 in the embodiment of the present application. Figure 4 (a) is the time domain waveform diagram under operating condition 1; Figure 4 (b) is the frequency domain FFT analysis diagram under operating condition 1; Figure 4 (c) is the time domain waveform diagram under the second operating condition; Figure 4 (d) is the frequency domain FFT analysis diagram under operating condition 2.

[0071] Figure 5 is the sensitivity calculation result at the dominant harmonic frequency of the current operating point of the working condition 1 in the embodiment of the present application. Figure 5 (a) is a schematic diagram of the calculation results of the sensitivity of harmonic voltage and harmonic current to admittance in working condition 1; Figure 5 (b) is a schematic diagram of the calculation results of the sensitivity of harmonic voltage and harmonic current to harmonic sources in operating condition 1.

[0072] Figure 6 It is the time domain simulation result after adjusting the system parameters according to the harmonic minimum operation direction at the current operating point of the working condition 1 in the embodiment of the present application. Figure 6 (a) is the time domain waveform diagram of the current operating point of working condition 1 after adjusting the system parameters according to the harmonic minimum operating direction; Figure 6 (b) is the frequency domain FFT analysis diagram of the current operating point of operating condition 1 after adjusting the system parameters according to the harmonic minimum operating direction.

[0073] Figure 7 This is a time domain simulation diagram of the current operating point of the second working condition in the embodiment of the present application. Figure 7 (a) is the time domain waveform diagram under three operating conditions; Figure 7 (b) is the frequency domain FFT analysis diagram under three operating conditions; Figure 7 (c) is the time domain waveform diagram under three operating conditions; Figure 7 (d) is the frequency domain FFT analysis diagram under three operating conditions.

[0074] Figure 8 is the sensitivity calculation result at the dominant harmonic frequency of the current operating point of the working condition 2 in the embodiment of the present application. Figure 8(a) is a schematic diagram of the calculation results of the sensitivity of the second harmonic voltage and harmonic current to the admittance under the working condition; Figure 8 (b) is a schematic diagram of the calculation results of the sensitivity of the second harmonic voltage and harmonic current to the harmonic source under the working conditions.

[0075] Fig. 9 It is the time domain simulation result after adjusting the system parameters according to the harmonic minimum operation direction at the current operating point of the working condition 2 in the embodiment of the present application. Fig. 9 (a) is the time domain waveform diagram of the current operating point of working condition 2 after adjusting the system parameters according to the harmonic minimum operating direction; Fig. 9 (b) is the frequency domain FFT analysis diagram of the current operating point of operating condition 2 after adjusting the system parameters according to the harmonic minimum operating direction.

[0076] Fig.10 This is a structural diagram of the power system harmonic impedance sensitivity calculation device in this application.

[0077] Fig.11 This is a structural diagram of an electronic device in an embodiment of the present application. DETAILED DESCRIPTION

[0078] The present application is further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and cannot be used to limit the scope of protection of the present application. It should be noted that the following detailed descriptions are all exemplary and are intended to provide further explanation of the present application.

[0079] Combination Figure 1 As shown, the embodiment of the present application specifically discloses a method for calculating harmonic impedance sensitivity of a power system, which includes the following steps:

[0080] Step 1: Obtain the network topology of the power system, and construct the harmonic node voltage solution equation in the power system according to the network topology of the power system;

[0081] Step 2: Based on the solution of the harmonic node voltage solution equation, construct the harmonic impedance sensitivity calculation equation in the power system;

[0082] Step 3: According to the calculation result of the harmonic impedance sensitivity calculation equation, the harmonic minimum operating direction of the current operating point position is obtained.

[0083] It should be noted that the purpose of this method in the present application is to quickly solve the harmonic node voltage, to measure the sensitivity of the harmonic voltage and harmonic current to each element of the node voltage equation, and to establish a complete harmonic sensitivity calculation system; and then by calculating the maximum value of the harmonic sensitivity, find the minimum harmonic operating direction near the current operating point to ensure the safe and stable operation of the power system.

[0084] Specifically, the step of constructing a harmonic node voltage solution equation in the power system according to the network topology of the power system in step 1 includes:

[0085] Obtain the order of each harmonic node in the network topology and the harmonic current of each branch; wherein the order of each harmonic node in the network topology is the grid connection point where the AC power grid is connected to the new energy station - the connection node directly connected to the grid connection point - the high-voltage side node of the new energy station step-up transformer;

[0086] Establish the corresponding harmonic node admittance matrix according to the order of each harmonic node in the network topology;

[0087] The node voltage equations of each harmonic node are established respectively, and the harmonic voltage of each harmonic node in the power system is obtained by combining the harmonic node admittance matrix and the harmonic current calculation of each branch.

[0088] Furthermore, in this embodiment, when establishing the node voltage equation of each harmonic node, the harmonic node voltage equation after matrix block division can be used. By appropriately dividing the harmonic node admittance matrix, complex matrix multiplication and other operations can be converted into relatively simple sub-block operations, thereby greatly reducing the amount of matrix operations and improving the solution efficiency. Specifically, the harmonic node voltage equation after matrix block division in the embodiment of the present application is:

[0089]

[0090] where Y Grid Admittance unit containing only the impedance of the onshore power grid; Y Line is an admittance unit containing only the series admittance of the transmission line; Y Line The transpose of Y REs is a diagonal matrix, and the diagonal elements are the frequency domain equivalent self-admittance of the new energy station; I Grid is the background harmonic current on the grid side; I REs is the background harmonic current on the renewable energy side; U Grid is the grid-side node harmonic voltage; U REs It is the harmonic voltage of the node on the new energy side.

[0091] In detail, in this embodiment, when the harmonic voltage of each harmonic node in the power system is obtained by combining the harmonic node admittance matrix and the harmonic current of each branch, the corresponding node harmonic voltage column vector is obtained by the inverse matrix of the harmonic node admittance matrix and the node injection harmonic column vector, and the corresponding calculation method is:

[0092]

[0093] Among them U h is the node harmonic voltage column vector; is the inverse matrix of the harmonic node admittance matrix; I h Injects a harmonic column vector into a node.

[0094] Furthermore, the step of constructing the harmonic impedance sensitivity calculation equation in the power system in step 2 includes:

[0095] (1) Obtain the harmonic voltage and harmonic current of each harmonic node in the power system;

[0096] (2) Calculate the sensitivity of the harmonic voltage of each harmonic node in the power system to the change in admittance:

[0097] A first calculation equation for the sensitivity of harmonic voltage to admittance change is constructed, wherein the first calculation equation is obtained based on the node injection harmonic column vector, the harmonic node admittance matrix and the first matrix, that is, the first calculation equation is:

[0098]

[0099] Where S Vh is the sensitivity of harmonic voltage to admittance change; Y h is the harmonic node admittance matrix; I h Inject harmonic column vector into the node; U h is the node harmonic voltage column vector; Y ij is the admittance element of the i-th row and j-th column of the harmonic node admittance matrix; E h For a h A square matrix of the same order, with the element in the i-th row and j-th column being 1 and the rest being 0;

[0100] When calculating the admittance sensitivity of the admittance unit on the AC grid side, the admittance sensitivity of the admittance unit on the new energy side, and the admittance sensitivity of the transmission line admittance unit, the positions of the admittance elements in the first matrix are different:

[0101] When calculating the AC grid side admittance unit Y Grid When the admittance sensitivity is h It is expressed as:

[0102]

[0103] When calculating the new energy side admittance unit Y REs When the admittance sensitivity is h It is expressed as:

[0104]

[0105] When calculating the transmission line admittance unit Y Line When the admittance sensitivity is h It is expressed as:

[0106]

[0107] or E h It is expressed as:

[0108]

[0109] (3) Calculate the sensitivity of the harmonic current of each harmonic node in the power system to the change in admittance:

[0110] A second calculation equation for the sensitivity of harmonic current to admittance change is constructed. The second calculation equation is obtained based on the admittance elements of the harmonic node admittance matrix and the harmonic voltages corresponding to the admittance elements. That is, the second calculation equation is:

[0111]

[0112] Where S Ih is the sensitivity of harmonic current to admittance change; I ij is the harmonic current flowing through the line between node i and node j; Y ij is the admittance element of the i-th row and j-th column of the harmonic node admittance matrix; U i is the harmonic voltage at node i; U j is the harmonic voltage at node j.

[0113] When the admittance element to be differentiated is ij When there is no direct correlation, the sensitivity of harmonic current to the admittance matrix is ​​obtained by the harmonic voltage corresponding to the admittance element in the harmonic node admittance matrix. At this time, the sensitivity of harmonic current to the admittance matrix is:

[0114] S Ih =Y ij (S Vh (i)-S Vh (j));

[0115] Where S Vh is the sensitivity of harmonic voltage to admittance change; S Vh (i) represents the vector S Vh The i-th element of is the sensitivity of the harmonic voltage at node i to the change in admittance; S Vh (j) represents the vector S Vh The j-th element of is the sensitivity of the harmonic voltage at node j to the change in admittance.

[0116] When calculating the sensitivity of harmonic current to the change of the overall admittance of the onshore power grid, the sensitivity of harmonic current to the admittance matrix is ​​obtained by the harmonic voltage corresponding to the admittance element in the harmonic node admittance matrix and the sensitivity of harmonic voltage to the admittance change. At this time, the sensitivity of harmonic current to the admittance matrix is:

[0117] S Ih =Y ij (S Vh (i)-S Vh (j))-U i +U j .

[0118] (4) Calculate the sensitivity of the harmonic voltage of each harmonic node in the power system to the background harmonic source:

[0119] A third calculation equation for the sensitivity of harmonic voltage to background harmonic source is constructed. The third calculation equation is obtained based on the admittance element of the inverse matrix of the harmonic node admittance matrix, that is, the third calculation equation is:

[0120]

[0121] Where S VI is the sensitivity of harmonic voltage to background harmonic source; is the inverse matrix of the harmonic node admittance matrix, U i is the node voltage of node i; Represents the admittance element in the i-th row and j-th column of the inverse matrix of the harmonic node admittance matrix.

[0122] The node voltage U of node i is i The calculation equation is:

[0123]

[0124] Where I j is the injected harmonic current of node j, n is the number of nodes in the grid-connected system;

[0125] (5) Calculate the sensitivity of the harmonic current of each harmonic node in the power system to the background harmonic source:

[0126] A fourth calculation equation for the sensitivity of harmonic current to background harmonic sources is constructed. The fourth calculation equation is obtained based on the harmonic node admittance matrix and the admittance elements of the corresponding inverse matrix, that is, the fourth calculation equation is:

[0127]

[0128] Where S Ie is the sensitivity of harmonic current to background harmonic current source; Represents the i-th row and j-th column element of the inverse harmonic nodal admittance matrix.

[0129] Furthermore, in step 3 of this embodiment, the step of obtaining the harmonic minimum operating direction of the current operating point position according to the calculation result of the harmonic impedance sensitivity calculation equation includes:

[0130] Select the maximum value of the sensitivity amplitude in the calculation result of the harmonic impedance sensitivity calculation equation as the best control variable of the harmonic;

[0131] When the imaginary part of the optimal control variable is positive, the harmonic minimum operation direction is the direction in which the optimal control variable decreases;

[0132] When the imaginary part of the optimal control variable is negative, the harmonic minimum operating direction is the direction in which the optimal control variable increases.

[0133] To further verify the effectiveness of this method, Figure 2 The new energy grid-connected system topology diagram and Figure 3 The frequency domain admittance model of the new energy grid-connected system is used for analysis, and this embodiment sets two grid operation conditions.

[0134] Working condition 1: Conventional operation mode of AC power grid:

[0135] set up Figure 2 The number of wind turbines in operation at the new energy station A is A, the number of wind turbines in operation at the new energy station B is B, and the number of wind turbines in operation at the new energy station C is C. There are two operating conditions in operating condition 1: A = 40, B = 0, C = 18 (operating condition 1) and A = 40, B = 0, C = 27 (operating condition 2). Figure 4 As shown, Figure 4 (a) and (b) are the time domain simulation results of the transmission line current of the new energy station under the operating conditions of A=40, B=0, and C=18 respectively; Figure 4 (c) and (d) are the time domain simulation results of the transmission line current of the new energy station under the operating conditions of A = 40, B = 0, and C = 27. Figure 4 It can be seen that the main reason for the harmonic exceeding the limit under this working condition is that the 11th harmonic current of the RES-A (new energy station A) transmission line exceeds the standard. Since the weight factor in the calculation formula of the defined harmonic comprehensive evaluation index increases exponentially with the change of the amplification factor, the calculated harmonic comprehensive evaluation index value range is large at this time, and the result accuracy is low.

[0136] This embodiment fully considers the harmonic sources of the AC power grid and the new energy station, and calculates the harmonic impedance sensitivity according to step 2 of the above method. Assuming that the working condition is the conventional operation mode of the AC power grid, that is, the working condition A=40, B=0, C=27, Figure 4 It can be seen that the dominant harmonic frequency is 11th at this time, and the sensitivity analysis of the current working condition is as follows: Figure 5 shown.

[0137] Combination Figure 5 The four sensitivities S shown in Vh , S Ih , S VI and SIe From the calculation results, it can be seen that under the current working conditions, the changes in the admittance of the new energy station, the admittance of RES-A and the admittance of the AC power grid have a greater impact on the 11th harmonic current and harmonic voltage of the grid-connected system, and the harmonic source of RES-A contributes more to the harmonic current and harmonic voltage.

[0138] To verify the correctness of the analysis results, the time domain simulation results when A = 40, B = 0, C = 27 are converted to Figure 6 .Depend on Figure 6 It can be seen that under this condition, the 11th harmonic current of the RES-A transmission line meets the constraints, and the time domain simulation results are consistent with the frequency domain analysis.

[0139] Working condition 2: Line break near PCC point:

[0140] There are also two operating conditions in operating condition 2: A=0, B=0, C=27 (operating condition 3) and A=20, B=39, C=27 (operating condition 4). Figure 7 As shown, Figure 7 (a) and (b) are the time domain simulation results of the transmission line current of the new energy station under the operating conditions of A=0, B=0, and C=27; Figure 7 (c) and (d) are the time domain simulation results of the transmission line current of the new energy station under the operating conditions of A = 20, B = 39, and C = 27. Figure 7 It can be seen that the main reason for the negative harmonic comprehensive evaluation index under the above working conditions is that the 5th harmonic current of RES-B / C (new energy station B / C) transmission line exceeds the standard. Then further discussion was carried out on the system under the PCC (public connection point) near the line disconnection.

[0141] Considering the harmonic voltage constraint and harmonic current constraint completely, assuming the working condition A=20,B=39,C=27, and the AC power grid PCC near the area is disconnected, the 5th harmonic is the dominant harmonic frequency. The sensitivity of the 5th harmonic under this working condition is calculated as follows: Figure 8 shown.

[0142] Depend on Figure 8 It can be seen that the harmonic voltage and harmonic current are most sensitive to the admittance of the new energy station, followed by the admittance of the transmission line. However, the sensitivity of the harmonic voltage and harmonic current to the change of the admittance of a single new energy station is relatively small. In order to reduce the fifth harmonic on the transmission line of RES-B (new energy station B) and RES-C (new energy station), the length of the grid-connected transmission line can be adjusted. In addition, by comparing Figure 8 (a) and Figure 5 (a), it can be seen that the sensitivity of the transmission line is significantly increased, indicating that the change of the transmission line length and parameters in this embodiment has a greater impact on the low-frequency harmonics.

[0143] Therefore, combined with the sensitivity analysis results, it is considered to shorten the transmission line length by 20% under the operating conditions of A = 20, B = 39, C = 27, and keep the number of units in the new energy station unchanged, still A = 20, B = 39, C = 27. The time domain simulation results are as follows Fig. 9 shown.

[0144] contrast Fig. 9 and Figure 7 It can be seen that when the transmission line length is shortened by 20%, the harmonic current of RES-B / C transmission line is reduced from 153.3A to 83.7A, and the total harmonic distortion rate is changed from 9.94% to 5.79%. Although the harmonic risk level is still high, it also shows that the transmission line length has a greater impact on the 5th harmonic current under the current working conditions.

[0145] In combination with the above embodiments, the method for calculating the harmonic impedance sensitivity of the power system of the present application arranges the nodes in the order of AC power grid-new energy station when solving the harmonic node voltage, and generates a block matrix, so that the equation solving efficiency is higher; and when calculating the harmonic impedance sensitivity, this method covers the sensitivity calculation of harmonic voltage and harmonic current to each element of the node voltage equation, and establishes a complete harmonic sensitivity calculation system. By calculating the maximum value of the harmonic sensitivity, it finds the minimum harmonic operating direction near the current operating point, thereby ensuring the safe and stable operation of the power system.

[0146] Further, combined with Fig.10 As shown, the present application also discloses a device for calculating harmonic impedance sensitivity of a power system, the device comprising:

[0147] A node voltage solving module is used to obtain the network topology of the power system and construct a harmonic node voltage solving equation in the power system according to the network topology of the power system;

[0148] A sensitivity calculation module is used to construct a harmonic impedance sensitivity calculation equation in the power system according to the solution result of the harmonic node voltage solution equation;

[0149] The harmonic direction judgment module is used to obtain the minimum harmonic running direction of the current running working point according to the calculation result of the harmonic impedance sensitivity calculation equation.

[0150] The device provided in the embodiment of the present application can achieve Figure 1 To avoid repetition, the various processes implemented by the method embodiment will not be described again here.

[0151] like Fig.11 As shown, the embodiment of the present application also provides an electronic device, including a processor and a memory, a program or instruction stored in the memory and executable on the processor, and when the program or instruction is executed by the processor, the following is achieved: Figure 1The various processes of the method embodiment shown in the figure can achieve the same technical effect. To avoid repetition, they will not be described again here.

[0152] The embodiment of the present application also provides a readable storage medium on which a program or instruction is stored. When the program or instruction is executed by a processor, the above Figure 1 The various processes of the method embodiments described above can achieve the same technical effect, and will not be described again here to avoid repetition.

[0153] The present application also provides a computer program product, including computer instructions, which, when executed by a processor, implement the above Figure 1 The various processes of the method embodiments described above can achieve the same technical effect, and will not be described again here to avoid repetition.

[0154] It should be understood that "one embodiment" or "an embodiment" mentioned throughout the specification means that specific features, structures or characteristics related to the embodiment are included in at least one embodiment of the present application. Therefore, "in one embodiment" or "in an embodiment" appearing throughout the specification does not necessarily refer to the same embodiment. In addition, these specific features, structures or characteristics can be combined in one or more embodiments in any suitable manner. It should be understood that in various embodiments of the present application, the size of the sequence number of the above-mentioned processes does not mean the order of execution, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application. The above-mentioned sequence numbers of the embodiments of the present application are only for description and do not represent the advantages and disadvantages of the embodiments.

[0155] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0156] In the several embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. The device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as: multiple units or components can be combined, or can be integrated into another device, or some features can be ignored or not executed. In addition, the coupling, direct coupling, or communication connection between the components shown or discussed can be through some interfaces, and the indirect coupling or communication connection of the devices or units can be electrical, mechanical or other forms.

[0157] The units described above as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units; they may be located in one place or distributed on multiple network units; some or all of the units may be selected according to actual needs to achieve the purpose of the present embodiment.

[0158] In addition, all functional units in the embodiments of the present application may be integrated into one processing unit, or each unit may be a separate unit, or two or more units may be integrated into one unit; the above-mentioned integrated units may be implemented in the form of hardware or in the form of hardware plus software functional units.

[0159] A person skilled in the art can understand that all or part of the steps of implementing the above method embodiment can be completed by hardware related to program instructions, and the aforementioned program can be stored in a computer-readable storage medium. When the program is executed, it executes the steps of the above method embodiment; and the aforementioned storage medium includes: mobile storage devices, read-only memories (ROM), magnetic disks or optical disks, etc., various media that can store program codes.

[0160] Alternatively, if the above-mentioned integrated unit of the present application is implemented in the form of a software function module and sold or used as an independent product, it can also be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the embodiment of the present application can essentially or in other words, the part that contributes to the prior art can be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for a device (which can be a terminal or a platform, etc.) to execute all or part of the methods described in each embodiment of the present application. The aforementioned storage medium includes: various media that can store program codes, such as mobile storage devices, ROMs, magnetic disks, or optical disks.

[0161] The above is only a preferred implementation of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A method for calculating harmonic impedance sensitivity of a power system, characterized in that: The steps include: Obtain the network topology of the power system, and construct the harmonic node voltage solution equation in the power system according to the network topology of the power system; According to the solution results of the harmonic node voltage solution equation, the harmonic impedance sensitivity calculation equation in the power system is constructed; According to the calculation result of the harmonic impedance sensitivity calculation equation, the harmonic minimum operating direction of the current operating point position is obtained.

2. The method for calculating harmonic impedance sensitivity of a power system according to claim 1, characterized in that: The step of constructing a harmonic node voltage solution equation in the power system according to the network topology of the power system comprises: Obtain the order of each harmonic node in the network topology and the harmonic current of each branch; wherein the order of each harmonic node in the network topology is the grid connection point where the AC power grid is connected to the new energy station - the connection node directly connected to the grid connection point - the high-voltage side node of the new energy station step-up transformer; Establish the corresponding harmonic node admittance matrix according to the order of each harmonic node in the network topology; The node voltage equations of each harmonic node are established respectively, and the harmonic voltage of each harmonic node in the power system is obtained by combining the harmonic node admittance matrix and the harmonic current calculation of each branch.

3. The method for calculating harmonic impedance sensitivity of a power system according to claim 2, characterized in that: The node voltage equation adopts the harmonic node voltage equation after matrix block division: where Y Grid Admittance unit containing only the impedance of the onshore power grid; Y Line is an admittance unit containing only the series admittance of the transmission line; Y Line The transpose of Y REs is a diagonal matrix, and the diagonal elements are the frequency domain equivalent self-admittance of the new energy station; I Grid is the background harmonic current on the grid side; I REs is the background harmonic current on the renewable energy side; U Grid is the grid-side node harmonic voltage; U REs It is the harmonic voltage of the node on the new energy side.

4. The method for calculating harmonic impedance sensitivity of a power system according to claim 2, characterized in that: When the harmonic voltage of each harmonic node in the power system is obtained by combining the harmonic node admittance matrix and the harmonic current of each branch, the corresponding node harmonic voltage column vector is obtained through the inverse matrix of the harmonic node admittance matrix and the node injection harmonic column vector.

5. The method for calculating harmonic impedance sensitivity of a power system according to claim 1, characterized in that: The step of constructing a harmonic impedance sensitivity calculation equation in the power system comprises: Obtain the harmonic voltage and harmonic current of each harmonic node in the power system; Calculate the sensitivity of the harmonic voltage of each harmonic node in the power system to the change of admittance; Calculate the sensitivity of the harmonic current of each harmonic node in the power system to the change of admittance; Calculate the sensitivity of the harmonic voltage of each harmonic node in the power system to the background harmonic source; The sensitivity of the harmonic current of each harmonic node in the power system to the background harmonic source is calculated.

6. The method for calculating harmonic impedance sensitivity of a power system according to claim 5, characterized in that: The step of calculating the sensitivity of the harmonic voltage of each harmonic node in the power system to the change of admittance comprises: Constructing a first calculation equation for the sensitivity of harmonic voltage to admittance change, wherein the first calculation equation is obtained based on the node-injected harmonic column vector, the harmonic node admittance matrix, and the first matrix, wherein the first matrix is ​​a square matrix of the same order as the harmonic node admittance matrix, and the elements in the i-th row and j-th column of the square matrix are 1, and the remaining elements are 0; When calculating the admittance sensitivity of the admittance unit on the AC power grid side, calculating the admittance sensitivity of the admittance unit on the new energy side, and calculating the admittance sensitivity of the transmission line admittance unit, the positions of the admittance elements in the first matrix are different.

7. The method for calculating harmonic impedance sensitivity of a power system according to claim 5, characterized in that: The step of calculating the sensitivity of the harmonic current of each harmonic node in the power system to the change of admittance comprises: Constructing a second calculation equation for the sensitivity of harmonic current to admittance change, wherein the second calculation equation is obtained based on the admittance elements of the harmonic node admittance matrix and the harmonic voltages corresponding to the admittance elements; When the derived admittance element is not directly related to the admittance element of the harmonic node admittance matrix, the sensitivity of the harmonic current to the admittance matrix is ​​obtained by the harmonic voltage corresponding to the admittance element in the harmonic node admittance matrix; When calculating the sensitivity of harmonic current to the change of the overall admittance of the onshore power grid, the sensitivity of harmonic current to the admittance matrix is ​​obtained by the harmonic voltage corresponding to the admittance element in the harmonic node admittance matrix and the sensitivity of the harmonic voltage to the admittance change.

8. The method for calculating harmonic impedance sensitivity of a power system according to claim 5, characterized in that: The step of calculating the sensitivity of the background harmonic source according to the harmonic voltage of each harmonic node in the power system comprises: A third calculation equation for the sensitivity of the harmonic voltage to the background harmonic source is constructed, wherein the third calculation equation is obtained based on the admittance element of the inverse matrix of the harmonic node admittance matrix.

9. The method for calculating harmonic impedance sensitivity of a power system according to claim 5, characterized in that: The step of calculating the sensitivity of the harmonic current of each harmonic node in the power system to the background harmonic source includes: A fourth calculation equation for the sensitivity of the harmonic current to the background harmonic source is constructed, wherein the fourth calculation equation is obtained based on the harmonic node admittance matrix and the admittance elements of the corresponding inverse matrix.

10. The method for calculating harmonic impedance sensitivity of a power system according to claim 1, characterized in that: The step of obtaining the harmonic minimum operating direction of the current operating point position according to the calculation result of the harmonic impedance sensitivity calculation equation includes: Select the maximum value of the sensitivity amplitude in the calculation result of the harmonic impedance sensitivity calculation equation as the best control variable of the harmonic; When the imaginary part of the optimal control variable is positive, the harmonic minimum operation direction is the direction in which the optimal control variable decreases; When the imaginary part of the optimal control variable is negative, the harmonic minimum operating direction is the direction in which the optimal control variable increases.

11. A device for calculating harmonic impedance sensitivity of a power system, characterized in that: The device comprises: A node voltage solving module is used to obtain the network topology of the power system and construct a harmonic node voltage solving equation in the power system according to the network topology of the power system; A sensitivity calculation module is used to construct a harmonic impedance sensitivity calculation equation in the power system according to the solution result of the harmonic node voltage solution equation; The harmonic direction judgment module is used to obtain the minimum harmonic running direction of the current running working point according to the calculation result of the harmonic impedance sensitivity calculation equation.

Images