Method, device and equipment for determining broadband harmonic resonance of power distribution network comprising grid-connected converter and medium

Abstract

The invention discloses a method, a device and equipment for determining broadband harmonic resonance of a power distribution network containing a grid-connected converter and a medium, and relates to the technical field of harmonic resonance. The method comprises the following steps: injecting a harmonic source into each node of the power distribution network at a plurality of preset frequencies in a sweep frequency manner, obtaining harmonic quantities under different frequencies, and determining harmonic amplification degree indexes under different frequencies; forming an amplification factor frequency characteristic curve with the frequency as the horizontal axis and the harmonic amplification degree index as the longitudinal axis, and determining a resonance amplification area; determining an original disturbance frequency harmonic severity index according to the resonance amplification region; determining secondary resonance severity indexes under different frequencies according to the harmonic quantity; and according to the original disturbance frequency harmonic severity index, the secondary resonance severity index and the harmonic amplification degree index, determining a harmonic danger region of each node and each branch in the power distribution network, and finally determining a harmonic resonance danger position in the power distribution network. By defining the secondary resonance severity index, the accuracy of harmonic quantization of the whole power distribution network can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of harmonic resonance, in particular to a power distribution network broadband harmonic resonance determination method, device and equipment containing a grid-connected converter and a medium. BACKGROUND

[0002] With the construction of new power systems, the power system is gradually developing towards a high proportion of new energy. Voltage source converters (VSC) used for new energy grid connection are also gradually widely used in power electronic distribution networks. However, the use of VSC can cause harmonic amplification of the distribution network. There are two reasons for this. On the one hand, the harmonic current generated by the VSC covers the low-frequency harmonic generated by the dead zone effect and the high-frequency harmonic generated by the PWM (Pulse Width Modulation), and the distribution network has a harmonic amplification problem caused by resonance. On the other hand, the secondary harmonic generated by the interaction between the VSC and the system harmonic source further enriches the harmonic spectrum, causing the harmonic amplification problem to worsen.

[0003] In order to fully understand the harmonic resonance characteristics of the entire distribution network at different frequencies and adapt to the needs of new energy equipment access, it is necessary to quantify the harmonic amplification of the VSC-containing distribution network. Harmonic device interaction makes the distribution network face the risk of harmonic amplification everywhere. One type of research starts from the resonance or harmonic amplification principle, uses the VSC grid connection transfer function, compensates the capacity-to-system capacity ratio, and uses the load state ratio to describe the harmonic amplification phenomenon at the grid connection point. This type of research often evaluates harmonic resonance based on the characteristics of the index itself, has strong pertinence, does not need to use additional limit boundaries, and has high flexibility, but only considers the influence of system background harmonics on the VSC grid connection point. When multiple disturbance sources are connected to the distribution network, the method often fails.

[0004] Considering that the frequency coupling effect of the VSC will make the propagation and response of the harmonic more complex, the evaluation system should consider the secondary harmonic, and solve the evaluation problem of the time sequence harmonic over-limit of the distribution network under actual working conditions. Therefore, the existing research is based on existing indexes such as THD and HRU, uses the applicability of the index itself, uses evaluation methods such as fuzzy mathematics and analytic hierarchy process, and compares with the harmonic standard limit to evaluate the harmonic resonance. The method has high applicability, the calculation process is systematic and standardized, but it depends on the limit standard and has strong subjectivity.

[0005] It can be seen that the existing research has not fully discussed the influence of VSC frequency coupling phenomenon on the whole network harmonic evaluation and the definition method of secondary harmonic index, only carries out low-frequency harmonic resonance analysis for the grid-connected point, and fails to provide a risk quantification method for each node and branch of the whole network, and does not meet the requirement of wide frequency domain harmonic resonance quantification. Even if there is a research that uses resonance classification method to construct a harmonic resonance risk evaluation system and gives the whole network risk quantification result, the evaluation method does not consider the definition method of secondary harmonic. SUMMARY

[0006] The purpose of the present application is to provide a power distribution network wide frequency harmonic resonance determination method, device, equipment and medium containing a grid-connected converter, which defines a secondary resonance severity index, and improves the accuracy of harmonic quantification of the whole power distribution network.

[0007] To achieve the above-mentioned purpose, the present application provides the following solutions:

[0008] In a first aspect, the present application provides a power distribution network wide frequency harmonic resonance determination method containing a grid-connected converter, comprising: injecting a harmonic source into each node of the power distribution network at a plurality of preset frequencies to obtain harmonic quantities at different frequencies; determining a harmonic amplification degree index at different frequencies according to the harmonic quantities at different frequencies; forming an amplification frequency characteristic curve with frequency as the horizontal axis and the harmonic amplification degree index as the vertical axis according to the harmonic amplification degree index at different frequencies, and determining a resonance amplification region on the amplification frequency characteristic curve; determining a primary disturbance frequency harmonic severity index according to the resonance amplification region; determining a secondary resonance severity index at different frequencies according to the harmonic quantities at different frequencies; determining a harmonic danger zone of each node and each branch in the power distribution network according to the primary disturbance frequency harmonic severity index, the secondary resonance severity index at different frequencies and the harmonic amplification degree index at different frequencies; determining a harmonic resonance dangerous position in the power distribution network according to the harmonic danger zone; and the harmonic resonance dangerous position includes a dangerous node and a dangerous branch.

[0009] In a second aspect, the present application provides a power distribution network wide frequency harmonic resonance determination device containing a grid-connected converter, comprising: a sweep injection module, an amplification index determination module, an amplification region determination module, a primary disturbance severity index determination module, a secondary resonance severity index determination module, a harmonic danger zone determination module and a dangerous position determination module.

[0010] The sweep injection module is configured to inject a harmonic source at a plurality of preset frequencies into each node of the power distribution network to obtain harmonic quantities at different frequencies. The amplification index determination module is configured to determine harmonic amplification degree indexes at different frequencies according to the harmonic quantities at different frequencies. The amplification region determination module is configured to form an amplification frequency characteristic curve with frequency as the horizontal axis and the harmonic amplification degree indexes as the vertical axis according to the harmonic amplification degree indexes at different frequencies, and determine a resonance amplification region on the amplification frequency characteristic curve. The original disturbance severity index determination module is configured to determine an original disturbance frequency harmonic severity index according to the resonance amplification region. The secondary resonance severity index determination module is configured to determine secondary resonance severity indexes at different frequencies according to the harmonic quantities at different frequencies. The harmonic danger region determination module is configured to determine harmonic danger regions of each node and each branch in the power distribution network according to the original disturbance frequency harmonic severity index, the secondary resonance severity indexes at different frequencies, and the harmonic amplification degree indexes at different frequencies. The dangerous position determination module is configured to determine a harmonic resonance dangerous position in the power distribution network according to the harmonic danger regions, and the harmonic resonance dangerous position includes a dangerous node and a dangerous branch.

[0011] In a third aspect, the present application provides a computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, and the processor executes the computer program to implement the power distribution network wideband harmonic resonance determination method with grid-connected converters as described above.

[0012] In a fourth aspect, the present application provides a computer readable storage medium having a computer program stored thereon, and the computer program is executed by a processor to implement the power distribution network wideband harmonic resonance determination method with grid-connected converters as described above.

[0013] According to the specific embodiments provided by the present application, the present application has the following technical effects:

[0014] The present application provides a power distribution network wideband harmonic resonance determination method, device, equipment and medium with grid-connected converters, defines a secondary resonance severity index, comprehensively considers an original disturbance frequency harmonic severity index, a secondary resonance severity index and a harmonic amplification degree index, quantifies harmonic danger regions of each node and each branch in the power distribution network, meets the requirement of wideband harmonic resonance quantification, and improves the accuracy of harmonic quantification of the entire power distribution network. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the related art, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0016] Figure 1 A flowchart of a power distribution network broadband harmonic resonance determination method provided by an embodiment of the present application is shown in the figure.

[0017] Figure 2 An amplification frequency characteristic curve provided by another embodiment of the present application is shown in the figure.

[0018] Figure 3 A functional module diagram of a power distribution network broadband harmonic resonance determination device provided by an embodiment of the present application is shown in the figure.

[0019] Figure 4 A structural diagram of a computer device provided by an embodiment of the present application is shown in the figure. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part 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 creative work fall within the scope of protection of the present application.

[0021] The above purposes, features and advantages of the present application will be more apparent and understandable. The present application will be described in further detail below with reference to the drawings and specific embodiments.

[0022] In an exemplary embodiment, as shown in Figure 1 a power distribution network broadband harmonic resonance determination method provided by an embodiment of the present application is provided, including the following steps 101 to 107.

[0023] Step 101: Inject harmonic sources at a plurality of preset frequencies into each node of the power distribution network to obtain harmonic quantities at different frequencies.

[0024] Step 102: Determine harmonic amplification degree indicators at different frequencies according to the harmonic quantities at different frequencies.

[0025] Step 103: Form an amplification frequency characteristic curve with frequency as the horizontal axis and harmonic amplification degree indicator as the vertical axis according to the harmonic amplification degree indicators at different frequencies, and determine a resonance amplification region on the amplification frequency characteristic curve.

[0026] Step 104: Determine original disturbance frequency harmonic severity indicators according to the resonance amplification region.

[0027] Step 105: Determine secondary resonance severity indicators at different frequencies according to the harmonic quantities at different frequencies.

[0028] Step 106: According to the original disturbance frequency harmonic severity index, the secondary resonance severity index at different frequencies and the harmonic amplification degree index at different frequencies, the harmonic danger zone of each node and each branch in the distribution network is determined.

[0029] Step 107: According to the harmonic danger zone, the harmonic resonance danger position in the distribution network is determined; the harmonic resonance danger position includes a dangerous node and a dangerous branch.

[0030] The above steps 101 to 107 are implemented, facing the VSC distribution network, based on the harmonic amplification multiple as the harmonic resonance judgment basis, the secondary harmonic severity index is defined, and the dangerous node and the dangerous branch of the whole network are evaluated in the form of frequency sweep injection.

[0031] In another exemplary embodiment of the present application, in order to evaluate the harmonic and interharmonic resonance response of a distribution network in a wide frequency domain range, in the analysis of the frequency domain range, each node is swept at a certain frequency resolution without distinction, and the response degree of the voltage of each node and the current of each branch is analyzed, so as to obtain the system harmonic resonance severity evaluation.

[0032] Therefore, the non-discriminatory danger zone evaluation quantifies the overall risk of the system determined by the network structure.

[0033] A unit harmonic current source is injected at bus j, and the harmonic self-impedance Z fjj at bus j is measured; the harmonic mutual impedance Z fij between bus i (i = 1, 2, …, n) and bus j; the harmonic voltage V at bus j; the harmonic current injected at bus j I The harmonic impedance Z ab of branch ab; the harmonic current of branch ab I

[0034] In another exemplary embodiment of the present application, in order to reflect the harmonic amplification of the distribution network, based on the self-impedance and mutual impedance relationship characteristic curve in the node impedance matrix, the amplification multiple index is used for harmonic amplification discrimination.

[0035] When the harmonic source is a unit voltage source, the harmonic amplification degree index is the harmonic voltage amplification multiple (Amplification of Harmonic Voltage, AHV), AHV (i.e. AHU in the formula below) has the physical meaning of the harmonic voltage of the non-harmonic source node, reflecting the voltage amplification of the non-harmonic source node. The determination formula of the harmonic voltage amplification multiple is:

[0036]

[0037] In the formula, AHUfij Amplification of Harmonic Voltage (AHV) is the amplification factor of harmonic voltage between bus i and bus j, AHV

[0038] When the harmonic source is a unit current source, the harmonic amplification degree index is the amplification of harmonic current (AHC), AHC has a physical meaning of harmonic current of each branch, reflecting the amplification of branch current. The determination formula of the harmonic current amplification factor is:

[0039]

[0040] In the formula, AHC abj Amplification of Harmonic Current (AHC) is the amplification factor of harmonic current between branch ab and bus j, Z aj Zab is the harmonic mutual impedance between branch a and bus j, Z bj Zbc is the harmonic mutual impedance between branch b and bus j.

[0041] If the harmonic voltage amplification factor and the harmonic current amplification factor are greater than 1, it means that at the fth harmonic, the corresponding bus and branch have occurred off-site harmonic amplification, and when f is the same as the resonance frequency, off-site resonance occurs.

[0042] When the harmonic source is a current source that generates the maximum allowable current, the harmonic amplification degree index is the amplification of harmonic impedance (AHZ), AHZ reflects the voltage amplification of the harmonic source node. When AHZ is greater than 1, it means that the distribution network injects a harmonic source at bus j, and local harmonic amplification occurs. The determination formula of the harmonic impedance amplification factor is:

[0043]

[0044] In the formula, AHZ fj Amplification of Harmonic Impedance (AHZ) is the amplification factor of harmonic impedance at bus j, Z fjjmax Z is the equivalent harmonic impedance of the system when the harmonic source node voltage does not exceed the standard.

[0045] The risk assessment system is a comprehensive measure of the degree of harm existing in the network, and the risk index is used to characterize the influence of system operation. In order to evaluate the influence of harmonic propagation in distribution network, the resonance risk assessment index system is established based on the resonance amplification index of original disturbance resonance and secondary resonance.

[0046] ​In another example embodiment of the present application, under the background harmonic effect, the voltage source grid-connected converter will generate a corresponding frequency harmonic current response, and each node and branch of the power distribution network will generate a harmonic amplification phenomenon under the original disturbance frequency current injection. Therefore, the harmonic source is injected into each node of the network with a certain frequency resolution, and the frequency characteristic of the amplification factor, i.e., the amplification factor frequency characteristic curve, is obtained, as shown in Figure 2

[0047] When the amplification factor (harmonic amplification degree index) is greater than 1, it indicates that harmonic amplification occurs. Therefore, the curve part of the amplification factor frequency characteristic curve where the harmonic amplification degree index is greater than 1 is determined as the resonance amplification region. Taking y = AHU as an example, Figure 2 where the horizontal coordinate is the harmonic frequency, and the vertical coordinate is the AHU value. AHUmax is the peak value of the AHU curve, and Figure 2 f ＞1 is the resonance amplification region, and the frequency range other than f ＞1 is the non-resonance amplification region.

[0048] In another example embodiment of the present application, the above step 104 can be replaced by the following steps 201 to 204:

[0049] Step 201: defining the original disturbance frequency harmonic severity index, including the resonance frequency bandwidth index, the resonance average amplification index, and the resonance amplification severity index.

[0050] Step 202: obtaining the resonance frequency bandwidth index according to the resonance amplification region by using the formula ; in the formula, RABI is the resonance frequency bandwidth index, f ＞1 is the frequency of the resonance amplification region, and f all is the total frequency bandwidth.

[0051] Step 203: obtaining the resonance average amplification index according to the resonance amplification region by using the formula ; in the formula, RAAI is the resonance average amplification index, and is the average value of all harmonic amplification degree indexes in the resonance amplification region.

[0052] Step 204: obtaining the resonance amplification severity index according to the resonance amplification region by using the formula ; in the formula, RASI is the resonance amplification severity index, x is the difference between the starting frequency and the frequency corresponding to the peak value of the resonance amplification region where the peak value of the amplification factor frequency characteristic curve is located, y is the difference between the harmonic amplification degree index and 1 on the amplification factor frequency characteristic curve, x max is the maximum difference between the starting frequency and the frequency corresponding to the peak value of the resonance amplification region where the peak value of the amplification factor frequency characteristic curve is located, and y max ​The maximum difference between the harmonic amplification degree index on the amplification frequency characteristic curve and 1.

[0053] The resonance bandwidth index (RABI) reflects the frequency band range of the harmonic amplification, the resonance average amplification index (RAAI) quantifies the average degree of the harmonic amplification, and the resonance amplification severity index (RASI) reflects the resonance condition near the resonance point.

[0054] In another exemplary embodiment of the present application, the secondary harmonic emission caused by the interaction of the voltage source grid-connected converter with the background disturbance can also cause the harmonic amplification. Therefore, to describe the results of the secondary harmonic in the frequency scan, the secondary harmonic voltage content (SHUC) and the secondary harmonic current content (SHCC) indexes are defined to reflect the content of the secondary harmonic.

[0055] The existing literature proposes that the secondary harmonic emission caused by the control asymmetry and the background disturbance frequency f p The related f p -f0frequency and the secondary harmonic emission caused by the sampling and PWM switching sideband and the switching frequency f c The related f c -f p , f c -f p -f0and f p +f0frequency, and the existing literature has verified the accuracy of the model, so the present application considers the secondary harmonic content of the four frequencies f p -2f0, f c -f p , f c -f p -f0and f p +f0.

[0056] The definitions of the secondary harmonic voltage content and the secondary harmonic current content are the square root value, the numerator is the square root value of the harmonic amount of all secondary frequencies in the sweep range, and the denominator is the square root value of the harmonic amount of all original disturbance frequencies in the sweep range. The secondary harmonic content quantifies the richness of the secondary harmonic, and based on the secondary harmonic content, the secondary harmonic severity index is defined.

[0057] The step 105 can be replaced by steps 301-303 as follows:

[0058] Step 301: According to the harmonic amount at each frequency, the formula is used to determine the secondary harmonic voltage content at each frequency; in the formula, SHUC kl is the secondary harmonic voltage content of the lower node k injected into the node l, is the secondary harmonic voltage of the s-th secondary frequency of the lower node k injected into the node l, is the primary disturbance frequency p harmonic voltage of the lower node k injected into the node l. There are four secondary frequencies, which are f p related to the disturbance frequency f p -2f0 frequency, f c related to the switching frequency f c -f p frequency, f c -f p -f0 frequency, and f p +f0 frequency; f0 is the fundamental frequency.

[0059] Step 302: According to the harmonic amount at each frequency, the formula is used to determine the secondary harmonic current content at each frequency; in the formula, SHCC kl is the secondary harmonic current content of the lower node k injected into the node l, is the secondary harmonic current of the s-th secondary frequency of the lower node k injected into the node l, is the primary disturbance frequency p harmonic current of the lower node k injected into the node l.

[0060] Step 303: According to the secondary harmonic voltage content at each frequency and the secondary harmonic current content at each frequency, the formula is used to determine the secondary resonance severity index at different frequencies; in the formula, S1 k is the first secondary resonance severity index, which means the secondary harmonic severity of the node k under the disturbance of different injected nodes n; S2 k is the second secondary resonance severity index, which means the secondary harmonic voltage severity of the node k under the disturbance of each frequency of other nodes; S3 k is the third secondary resonance severity index, which means the secondary harmonic severity of the branch; n is the number of nodes, and b is the number of branches.

[0061] In another exemplary embodiment of the present application, in order to comprehensively describe the dangerous degree of the disturbance source injected at different nodes and the dangerous degree of the network nodes and branches in response to the disturbance, a dangerous region evaluation index is defined from the aspects of disturbance injection and response. The dangerous region evaluation index is a sequence of values, which reflects the relative size of the dangerous degree of the nodes or branches. For the disturbance source position dangerous region, the greater the value, the higher the comprehensive dangerous degree caused by the disturbance source injected at the node; for the node / branch dangerous region, the greater the value, the higher the comprehensive dangerous degree of the node / branch response.

[0062] For the disturbance source position dangerous region, all the harmonic resonance amplification indexes and the secondary severity indexes defined above are selected, and the indexes are weighted and summed to obtain a node incentive risk metric (NIM) capable of quantifying the dangerous degree of the disturbance source injection. For the response dangerous region, according to the response categories, the response can be divided into node harmonic voltage response and branch harmonic current response. Therefore, the harmonic amplification degree indexes based on the impedance amplification factor and the voltage amplification factor, and the secondary harmonic voltage severity index are selected to constitute a node response risk metric (NRM); the harmonic amplification degree indexes based on the current amplification factor, and the secondary harmonic current severity index are selected to constitute a branch response risk metric (BRM). According to the NRM and the BRM, the dangerous regions with higher resonance risk in the network response can be quantified.

[0063] The above step 106 can be replaced by the following steps 401 to 404:

[0064] Step 401: Determine that the harmonic dangerous region of each node in the power distribution network includes a node incentive risk metric and a node response risk metric, and the harmonic dangerous region of each branch in the power distribution network includes a branch response risk metric.

[0065] Step 402: According to the original disturbance frequency harmonic severity index and the secondary resonance severity index at different frequencies, the node incentive risk metric is determined by using the formula ; in the formula, NIM k is the node incentive risk metric; w c is the weight of the cth index, R c is the cth index adopted by the NIM, N1 is the number of indexes adopted by the NIM. k

[0066] Step 403: According to the harmonic voltage amplification factor at different frequencies, the harmonic impedance amplification factor at different frequencies, and the secondary resonance severity index at different frequencies, the node response risk metric is determined by using the formula ​determining a node response risk index; wherein, NRM k is the node response risk index, w d is the weight of the dth index, R d is the dth index adopted by the NRM, N2 is the NRM k the number of indexes adopted.

[0067] Step 404: according to the harmonic current amplification factor at different frequencies and the secondary resonance severity index at different frequencies, the formula determining a branch response risk index; wherein, BRM k is the node response risk index, w e is the weight of the e th index, R e is the e th index adopted by the BRM, N3 is the BRM k the number of indexes adopted.

[0068] In another exemplary embodiment of the present application, based on the above obtained node excitation risk index, node response risk index and branch response risk index, step 107 can specifically include: taking the node corresponding to the node excitation risk index greater than the first threshold value as the dangerous node with high disturbance source injection risk in the power distribution network. Taking the node corresponding to the node response risk index greater than the second threshold value as the dangerous node with high response resonance risk in the power distribution network. Taking the branch corresponding to the branch response risk index greater than the third threshold value as the dangerous branch with high response resonance risk in the power distribution network.

[0069] Based on the impedance amplification factor and the voltage / current amplification factor, the present application quantifies the harmonic resonance amplification degree, defines the disturbance source position dangerous domain, node / branch response dangerous domain index. And proposes an evaluation method of non-discriminative quantization of disturbance source position dangerous area, node / branch response dangerous area considering coupled harmonics, realizes the discrimination of disturbance source access position, power distribution network resonance overvoltage node and resonance overcurrent serious branch.

[0070] Based on the same inventive concept, the present application also provides a power distribution network wide frequency harmonic resonance determination device with a grid-connected converter for implementing the power distribution network wide frequency harmonic resonance determination method involving the grid-connected converter as described above. The implementation scheme for solving the problem provided by the device is similar to the implementation scheme recorded in the above method, so the specific limitations in one or more power distribution network wide frequency harmonic resonance determination device embodiments of the grid-connected converter provided below can refer to the limitations of the power distribution network wide frequency harmonic resonance determination method of the grid-connected converter in the above, which will not be repeated here.

[0071] In one exemplary embodiment, as Figure 3As shown, a power distribution network wideband harmonic resonance determination device with grid-connected converters is provided, which comprises a frequency sweep injection module, an amplification index determination module, an amplification region determination module, an original disturbance severity index determination module, a secondary resonance severity index determination module, a harmonic danger zone determination module, and a dangerous position determination module.

[0072] The frequency sweep injection module is configured to inject harmonic sources into each node of the power distribution network at a plurality of preset frequencies to obtain harmonic quantities at different frequencies. The amplification index determination module is configured to determine harmonic amplification degree indexes at different frequencies according to the harmonic quantities at different frequencies. The amplification region determination module is configured to form an amplification frequency characteristic curve with frequency as the horizontal axis and harmonic amplification degree index as the vertical axis according to the harmonic amplification degree indexes at different frequencies, and determine a resonance amplification region on the amplification frequency characteristic curve. The original disturbance severity index determination module is configured to determine an original disturbance frequency harmonic severity index according to the resonance amplification region. The secondary resonance severity index determination module is configured to determine secondary resonance severity indexes at different frequencies according to the harmonic quantities at different frequencies. The harmonic danger zone determination module is configured to determine harmonic danger zones of each node and each branch in the power distribution network according to the original disturbance frequency harmonic severity index, the secondary resonance severity indexes at different frequencies, and the harmonic amplification degree indexes at different frequencies. The dangerous position determination module is configured to determine harmonic resonance dangerous positions in the power distribution network according to the harmonic danger zones; the harmonic resonance dangerous positions include dangerous nodes and dangerous branches.

[0073] In an exemplary embodiment, a computer device is provided, which can be a server or a terminal, and an internal structure diagram thereof can be as shown in the figure. Figure 4 The computer device comprises a processor, a memory, an input / output interface (I / O), and a communication interface. The processor, the memory, and the input / output interface are connected through a system bus, and the communication interface is connected to the system bus through the input / output interface. The processor of the computer device is configured to provide computing and control capabilities. The memory of the computer device comprises a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program, and a database. The internal memory provides an environment for the operating system and the computer program in the non-volatile storage medium to run. The database of the computer device is configured to store harmonic resonance dangerous positions in the power distribution network. The input / output interface of the computer device is configured to exchange information between the processor and external devices. The communication interface of the computer device is configured to communicate with external terminals through network connection. The computer program is executed by the processor to implement a power distribution network wideband harmonic resonance determination method with grid-connected converters.

[0074] Those skilled in the art can understand that, Figure 4The structure shown in the figure is only a block diagram of part of the structure related to the scheme of the present application, and does not constitute a limitation on the computer device to which the scheme of the present application is applied. The specific computer device can include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components. In one exemplary embodiment, a computer device is provided, including a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement the steps in the above method embodiments.

[0075] In one exemplary embodiment, a computer readable storage medium is provided, storing a computer program, which is executed by a processor to implement the steps in the above method embodiments.

[0076] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data for analysis, stored data, displayed data, etc.) involved in the present application are all information and data authorized by the user or authorized by all parties.

[0077] A person of ordinary skill in the art can understand that all or part of the processes in the above method embodiments can be completed by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer readable storage medium and executed to include the processes of the above method embodiments. Any reference to a memory, database or other medium used in the embodiments provided by the present application can include at least one of a non-volatile and volatile memory. The non-volatile memory can include a read-only memory (ROM), a magnetic tape, a floppy disk, a flash memory, an optical storage, a high-density embedded non-volatile memory, a resistive random access memory (ReRAM), a magnetoresistive random access memory (MRAM), a ferroelectric random access memory (FRAM), a phase change memory (PCM), a graphene memory, etc. The volatile memory can include a random access memory (RAM) or an external cache memory, etc. As an illustration but not limitation, the RAM can be in various forms, such as a static random access memory (SRAM) or a dynamic random access memory (DRAM), etc.

[0078] The database involved in each of the embodiments provided in the present application can include at least one of a relational database and a non-relational database. The non-relational database can include a distributed database based on a blockchain, and the like, without being limited thereto. The processor involved in each of the embodiments provided in the present application can be a general-purpose processor, a central processing unit, a graphics processing unit, a digital signal processor, a programmable logic device, a data processing logic device based on quantum computing, and the like, without being limited thereto.

[0079] Any combination of the technical features of the above embodiments can be made. In order to make the description simple, all possible combinations of the technical features in the above embodiments are not described, however, as long as the combination of the technical features does not exist, it should be considered as the scope of the present application.

[0080] The principles and implementation modes of the present application are described by applying specific examples herein, and the above embodiments are only used to help understand the method of the present application and its core idea; meanwhile, for those skilled in the art, according to the idea of the present application, the specific implementation mode and application range will be changed. In conclusion, the content of the present application should not be understood as a limitation.

Claims

1. A method for determining broadband harmonic resonance in a power distribution grid containing grid-tie converters, the method comprising: The method comprises the following steps: Harmonic sources are swept at preset frequencies to inject each node of the power distribution network to obtain harmonic quantities at different frequencies; According to the harmonic quantities at different frequencies, harmonic amplification degree indexes at different frequencies are determined; According to the harmonic amplification degree indexes at different frequencies, an amplification frequency characteristic curve with frequency as the horizontal axis and the harmonic amplification degree indexes as the vertical axis is formed, and a resonance amplification region is determined on the amplification frequency characteristic curve; According to the resonance amplification region, a harmonic severity index of the original disturbance frequency is determined; According to the harmonic quantities at different frequencies, secondary resonance severity indexes at different frequencies are determined; According to the harmonic severity index of the original disturbance frequency, the secondary resonance severity indexes at different frequencies and the harmonic amplification degree indexes at different frequencies, harmonic danger domains of each node and each branch in the power distribution network are determined; According to the harmonic danger domains, harmonic resonance dangerous positions in the power distribution network are determined; the harmonic resonance dangerous positions include dangerous nodes and dangerous branches.

2. The method of claim 1, wherein the grid-connected converter is a voltage source converter. When the harmonic source is a unit voltage source, the harmonic amplification degree index is a harmonic voltage amplification multiple, and a determination formula of the harmonic voltage amplification multiple is: wherein AHU fij is the harmonic voltage amplification factor between bus i and bus j, is the harmonic voltage at bus i, is the harmonic voltage at bus j, Z fij is the harmonic mutual impedance between bus i and bus j, Z fjj is the harmonic self-impedance at bus j; When the harmonic source is a unit current source, the harmonic amplification degree index is a harmonic current amplification multiple, and a determination formula of the harmonic current amplification multiple is: wherein AHC abj is the harmonic current amplification factor between branch ab and bus j, is the harmonic current of branch ab, is the injected harmonic current at bus j, Z aj is the harmonic mutual impedance between branch a and bus j, Z bj is the harmonic mutual impedance between branch b and bus j, Z ab is the harmonic impedance of branch ab; When the harmonic source is a current source generating a maximum allowable current, the harmonic amplification degree index is a harmonic impedance amplification multiple, and a determination formula of the harmonic impedance amplification multiple is: where AHZ fj is the harmonic impedance amplification factor at bus j, Z fjjmax is the system equivalent harmonic impedance when the harmonic source node voltage is not over-standard.

3. The method of claim 1, wherein the grid-connected converter is a voltage source converter. On the amplification frequency characteristic curve, the resonance amplification region is determined, specifically including: The curve part with the harmonic amplification degree index greater than 1 on the amplification frequency characteristic curve is determined as the resonance amplification region.

4. The method of claim 1, wherein, According to the resonance amplification region, the harmonic severity index of the original disturbance frequency is determined, specifically including: The harmonic severity index of the original disturbance frequency includes a resonance frequency bandwidth index, a resonance average amplification index and a resonance amplification severity index; According to the resonance amplification region, a formula is obtained, wherein RABI is the resonance frequency band width index, f ＞1 is the frequency of the resonance amplification region, and f all is the total frequency band width. According to the resonance amplification region, a formula is used to obtain a resonance average amplification index; in the formula, RAAI is the resonance average amplification index, is an average of all harmonic amplification degree indexes in the resonance amplification region. According to the resonance amplification region, a formula is used to obtain a resonance amplification severity index; in the formula, RASI is the resonance amplification severity index, x is a difference between a starting frequency in a resonance amplification region in which a peak of an amplification frequency characteristic curve is located and a frequency corresponding to the peak, and y is a difference between a harmonic amplification degree index on the amplification frequency characteristic curve and 1, x max is a maximum difference between the starting frequency in the resonance amplification region in which the peak of the amplification frequency characteristic curve is located and the frequency corresponding to the peak, and y max is a maximum difference between the harmonic amplification degree index on the amplification frequency characteristic curve and 1.

5. The method of claim 1, wherein, According to the harmonic quantities at different frequencies, the secondary resonance severity indexes at different frequencies are determined, specifically including: According to the harmonic amount under each frequency, the formula is used to determine the secondary harmonic voltage content ratio under each frequency; in the formula, SHUC kl is the secondary harmonic voltage content ratio of the lower node k injected into the node l, is the secondary harmonic voltage of the s-th secondary frequency of the lower node k injected into the node l, is the primary harmonic voltage of the original disturbance frequency p of the lower node k injected into the node l; the secondary frequency has four kinds, which are respectively f p , f p , f c , f c , f p , f c , f p , f p , f According to the harmonic amount under each frequency, the formula determines the secondary harmonic current content ratio under each frequency; in the formula, SHCC kl injects the secondary harmonic current content ratio of the lower node k into the node l, injects the secondary harmonic current of the s-th secondary frequency of the lower node k into the node l, injects the primary disturbance frequency p harmonic current of the lower node k into the node l; According to the secondary harmonic voltage content ratio under each frequency and the secondary harmonic current content ratio under each frequency, the formula is used to determine the secondary resonance severity index under different frequencies; in the formula, S1 k is the first secondary resonance severity index, which means the secondary harmonic severity of node k under the disturbance of different injection nodes n; S2 k is the second secondary resonance severity index, which means the response secondary harmonic voltage severity of node k under the disturbance of other nodes at each frequency; S3 k is the third secondary resonance severity index, which means the response secondary harmonic severity of branches; n is the number of nodes, and b is the number of branches.

6. The method of claim 2, wherein the grid-connected converter is a grid-connected inverter. According to the harmonic severity index of the original disturbance frequency, the secondary resonance severity indexes at different frequencies and the harmonic amplification degree indexes at different frequencies, the harmonic danger domains of each node and each branch in the power distribution network are determined, specifically including: The harmonic danger domains of each node in the power distribution network include a node excitation risk index and a node response risk index, and the harmonic danger domains of each branch in the power distribution network include a branch response risk index; According to the original disturbance frequency harmonic severity index and the secondary resonance severity index under different frequencies, the formula is used to determine the node excitation risk index; in the formula, NIM k is the node excitation risk index; w c is the weight of the cth index; R c is the cth index used by NIM; N1 is the number of indexes used by NIM k ; S1 k is the first secondary resonance severity index, which means the secondary harmonic severity of the node k under different injected node n disturbances; According to the harmonic voltage amplification factor under different frequencies, the harmonic impedance amplification factor under different frequencies and the secondary resonance severity index under different frequencies, the formula is used to determine the node response risk index; in the formula, NRM k is the node response risk index, w d is the weight of the dth index, R d is the dth index used by NRM, N2 is the number of indexes used by NRM k S2 k is the second secondary resonance severity index, which means the node k response secondary harmonic voltage severity under each frequency disturbance of other nodes; According to the harmonic current amplification factor under different frequencies and the secondary resonance severity index under different frequencies, the formula is used to determine the branch response risk index; in the formula, BRM k is the node response risk index, w e is the weight of the e-th index, R e is the e-th index adopted by the BRM, N3 is the number of indexes adopted by the BRM k S3 k is the third secondary resonance severity index, which means the branch response secondary harmonic severity.

7. The method of claim 6, wherein the grid-connected converter is a voltage source converter. According to the harmonic danger domains, the harmonic resonance dangerous positions in the power distribution network are determined, specifically including: The node corresponding to the node excitation risk index greater than a first threshold value is taken as a dangerous node with high disturbance source injection risk in the power distribution network; The node corresponding to the node response risk index greater than a second threshold value is taken as a dangerous node with high resonance response risk in the power distribution network; The branch corresponding to the branch response risk index greater than a third threshold value is taken as a dangerous branch with high resonance response risk in the power distribution network.

8. An apparatus for determining broadband harmonic resonance in a power distribution grid containing grid-tie inverters, the apparatus comprising: The method comprises the following steps: The sweep injection module is configured to sweep harmonic sources at preset frequencies to inject each node of the power distribution network to obtain harmonic quantities at different frequencies; An amplification index determination module is configured to determine a harmonic amplification degree index at different frequencies according to the harmonic amount at the different frequencies. An amplification region determination module is configured to form an amplification frequency characteristic curve with frequency as the horizontal axis and the harmonic amplification degree index as the vertical axis according to the harmonic amplification degree index at different frequencies, and determine a resonance amplification region on the amplification frequency characteristic curve. An original disturbance severity index determination module is configured to determine an original disturbance frequency harmonic severity index according to the resonance amplification region. A secondary resonance severity index determination module is configured to determine a secondary resonance severity index at different frequencies according to the harmonic amount at the different frequencies. A harmonic danger region determination module is configured to determine a harmonic danger region of each node and each branch in the power distribution network according to the original disturbance frequency harmonic severity index, the secondary resonance severity index at different frequencies, and the harmonic amplification degree index at different frequencies. A dangerous position determination module is configured to determine a harmonic resonance dangerous position in the power distribution network according to the harmonic danger region; the harmonic resonance dangerous position includes a dangerous node and a dangerous branch.

9. A computer device comprising: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the power distribution network wideband harmonic resonance determination method with grid-connected converters according to any one of claims 1-7.

10. A computer-readable storage medium having stored thereon a computer program, characterized in that, The computer program is executed by the processor to implement the power distribution network wideband harmonic resonance determination method with grid-connected converters according to any one of claims 1-7.

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