Iterative calculation method and system for harmonic voltage distribution of power distribution network

Abstract

The invention discloses a power distribution network harmonic voltage distribution iterative calculation method and system, and aims at a power distribution network in which multiple power electronic devices are merged, the characteristics of a converter are considered, iterative calculation is adopted, and a harmonic impedance model of the converter is introduced, so that the harmonic voltage distribution of the power distribution network can be calculated more accurately, and the calculation precision is improved. The method is especially suitable for increasing converter access modern power distribution networks. According to the method, the defects of a traditional method in processing the characteristics of the power electronic equipment are effectively overcome, and the method has high precision and practicability.

Description

Background Art

[0002] In recent years, with the development of renewable energy systems, power electronic devices have been connected to the grid on a large scale. Unlike traditional linear loads, power electronic devices will have complex responses when subjected to harmonic voltage disturbances, such as frequency coupling and other characteristics. Traditional harmonic power flow calculations only consider the impact of linear loads. As the degree of power electronics in the distribution network increases, the deviation of traditional calculations increases. Therefore, it is necessary to consider the characteristics of power electronic devices in harmonic power flow calculations to improve the accuracy of harmonic calculations.

[0003] Traditional harmonic voltage calculation ignores the disturbed response of the converter, treats the converter as a constant power source, and neglects the interaction within the power electronic equipment, resulting in poor calculation accuracy. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide an iterative calculation method and system for harmonic voltage distribution in a distribution network in view of the deficiencies in the above-mentioned prior art, taking into account the characteristics of the converter and combining the two by an iterative calculation method, so as to solve the technical problem that the traditional calculation method is insufficient in processing the converter, and has high accuracy and practicality.

[0005] The present invention adopts the following technical solutions: A method for iteratively calculating harmonic voltage distribution in a power distribution network comprises the following steps: S1. Obtain the load size of each node of the distribution network and the line impedance between nodes, and determine the access capacity and location of the power electronic converter and harmonic source; S2, obtaining the filter parameters of the power electronic converter in step S1 and the control method thereof, and determining the harmonic emission characteristics of the harmonic source in step S1 ; S3, calculating the fundamental power flow of the distribution network according to the node load conditions and line parameters obtained in step S1; S4. According to the power flow calculation result of step S3, the load on the distribution network node except the converter is equivalent to a resistance and inductance series load, and the equivalent parameters are calculated; S5. Calculate the harmonic impedance matrix of the grid according to the line parameters obtained in step S1 and the equivalent load obtained in step S4. ; S6, obtaining the harmonic impedance characteristics of the power electronic converter model according to the filter parameters and controller parameters of the power electronic converter in step S2; S7, using the harmonic emission characteristics of the harmonic source in step S2 as the initial harmonic disturbance, combined with the harmonic impedance matrix in step S4, to calculate the initial distribution of the harmonic voltage of the distribution network; S8. Calculate a new harmonic current disturbance of the distribution network according to the harmonic voltage distribution in step S7 and the harmonic impedance characteristics of the power electronic converter in step S6; S9, superimposing the harmonic current disturbance value in step S8 on the initial harmonic disturbance, and combining with the grid harmonic impedance matrix in step S5 to calculate a new harmonic voltage distribution; S10. According to the harmonic voltage distribution of step S9, steps S7 to S8 are repeated until the harmonic voltage converges, thus completing the iterative calculation of the harmonic voltage distribution of the distribution network.

[0006] Preferably, in step S4, the equivalent parameters are calculated as follows:

[0007] in, R is the equivalent resistance, X is the equivalent reactance, P is the active power of the node, Q is the reactive power of the node, U is the effective value of the voltage at the node.

[0008] Preferably, in step S5, the grid harmonic impedance matrix is ​​the impedance matrix corresponding to each harmonic, and the specific calculation process is as follows: Calculate the line impedance and the equivalent impedance of the load according to the calculated harmonic frequency; list the node admittance matrix of the grid; perform the inverse operation on the node admittance matrix to obtain the final harmonic impedance matrix.

[0009] Preferably, in step S6, the power electronic converter model includes harmonic state space and impedance modeling methods.

[0010] Preferably, the harmonic impedance characteristic of the power electronic converter for:

[0011] in, is the harmonic disturbance voltage, is the harmonic impedance value of the converter.

[0012] Preferably, in step S7, the initial distribution of the harmonic voltage of the distribution network for:

[0013] in, is the harmonic impedance matrix of the grid, is the harmonic emission characteristic of the harmonic source.

[0014] Preferably, in step S8, the new harmonic current disturbance of the distribution network for:

[0015] in, is the initial distribution of harmonic voltage in the distribution network, is the harmonic impedance value of the converter.

[0016] Preferably, steps S7 to S9 obtain more accurate distribution network harmonic voltage distribution results taking into account converter characteristics through repeated iterations of harmonic voltage distribution and harmonic current calculation.

[0017] Preferably, in step S9, the new harmonic voltage distribution for:

[0018] in, is the harmonic impedance matrix of the grid, is the harmonic emission characteristic of the harmonic source, New harmonic current disturbances in the distribution network.

[0019] In a second aspect, an embodiment of the present invention provides a system for iteratively calculating harmonic voltage distribution in a power distribution network, comprising: Parameter module, which obtains the load size of each node of the distribution network, the line impedance between nodes, determines the access capacity and location of the power electronic converter and the harmonic source; obtains the filter parameters of the power electronic converter and its control method, and determines the harmonic emission characteristics of the harmonic source ; Calculate the fundamental power flow of the distribution network according to the node load conditions and line parameters; The calculation module, based on the power flow calculation results, equates the loads on the distribution network nodes except the converter to the resistance and inductance series loads, and calculates the equivalent parameters; based on the line parameters and equivalent loads, calculates the harmonic impedance matrix of the grid ; The disturbance module obtains the harmonic impedance characteristics of the power electronic converter model according to the filter parameters and controller parameters of the power electronic converter; the harmonic emission characteristics of the harmonic source are used as the initial harmonic disturbance, and combined with the harmonic impedance matrix, the initial distribution of the harmonic voltage of the distribution network is calculated; The voltage module calculates the new harmonic current disturbance of the distribution network according to the harmonic voltage distribution and the harmonic impedance characteristics of the power electronic converter; superimposes the harmonic current disturbance value on the initial harmonic disturbance, and calculates the new harmonic voltage distribution in combination with the grid harmonic impedance matrix; The output module repeats the process according to the new harmonic voltage distribution until the harmonic voltage converges, thus completing the iterative calculation of the harmonic voltage distribution of the distribution network.

[0020] In a third aspect, a computer device comprises a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the above-mentioned iterative calculation method for harmonic voltage distribution in a distribution network when executing the computer program.

[0021] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium, comprising a computer program, which, when executed by a processor, implements the steps of the above-mentioned method for iteratively calculating the harmonic voltage distribution of the power distribution network.

[0022] In a fifth aspect, a chip comprises a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the above-mentioned method for iteratively calculating the harmonic voltage distribution of the distribution network when executing the computer program.

[0023] In a sixth aspect, an embodiment of the present invention provides an electronic device, comprising a computer program, which, when executed by the electronic device, implements the steps of the above-mentioned iterative calculation method for harmonic voltage distribution in the power distribution network.

[0024] Compared with the prior art, the present invention has at least the following beneficial effects: An iterative calculation method for harmonic voltage distribution in distribution network is designed for new distribution network system incorporating multiple power electronic devices. In addition to the traditional harmonic calculation method, the characteristics of the converter are considered. By introducing the impedance model of the converter, the output current characteristics of the converter under harmonic voltage disturbance are calculated, and the harmonic voltage distribution of the distribution network is calculated more accurately; the harmonic current emission of the converter under voltage disturbance is described by using the harmonic state space or impedance model; the converter model and the node impedance matrix are linked in an iterative manner, and finally the harmonic voltage distribution of the distribution network is calculated.

[0025] Furthermore, the general load is modeled by using a linear element equivalent method. This method is close to the characteristics of linear loads on the one hand, and does not increase the complexity of the network impedance equation on the other hand.

[0026] Furthermore, the network impedance equation of the system cannot be solved directly, and is generally obtained by inverting the node admittance equation of the system. The node admittance equation of the system can be directly written according to the structure and impedance parameters of the system. The network impedance equations of the system at different frequencies are independent of each other and need to be calculated separately.

[0027] Furthermore, the present invention relates to a method for calculating harmonic voltage distribution. Therefore, when modeling the converter, it is necessary to adopt a method that can reflect the harmonic impedance characteristics of the converter, wherein both harmonic state space and impedance modeling can accurately describe the harmonic impedance characteristics of the converter.

[0028] Furthermore, considering that the converter model and the system network impedance equation are obtained in different coordinate systems and number domains, they cannot be solved directly together, but the calculation results of the two can be equivalently converted. For this purpose, an iterative method is adopted: first calculate the network harmonic voltage distribution, and then use the calculation results to calculate the harmonic emission of the converter. Finally, according to the harmonic emission of the converter, the harmonic voltage distribution is updated. Repeated iterations eventually reach convergence. The iterative method realizes the interaction between the two models, and finally calculates the steady-state results.

[0029] It can be understood that the beneficial effects of the second to sixth aspects mentioned above can be found in the relevant description of the first aspect mentioned above, and will not be repeated here.

[0030] In summary, the present invention can more accurately calculate the harmonic voltage distribution of the distribution network and improve the calculation accuracy, and is particularly suitable for modern distribution networks where converters are increasingly connected.

[0031] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is an iterative flow chart of the method of the present invention; Figure 2 A verification scene diagram for the method of the present invention; FIG3 is a comparison result diagram of the method of the present invention and the traditional method, wherein (a) is the 7th harmonic voltage iteration result (amplitude) of the node, (b) is the 7th harmonic voltage iteration result (phase) of the node, (c) is the 11th harmonic voltage iteration result (amplitude) of the node, and (d) is the 11th harmonic voltage iteration result (phase) of the node; Figure 4 A schematic diagram of a computer device provided by an embodiment of the present invention; Figure 5 The block diagram of a chip provided according to an embodiment of the present invention. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] In the description of the present invention, it should be understood that the terms “include” and “comprises” indicate the presence of described features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or collections thereof.

[0035] It should also be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0036] It should be further understood that the term "and / or" used in the present specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes these combinations. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in the present invention generally indicates that the associated objects are in an "or" relationship.

[0037] It should be understood that, although the terms first, second, third, etc. may be used to describe preset ranges, etc. in the embodiments of the present invention, these preset ranges should not be limited to these terms. These terms are only used to distinguish preset ranges from each other. For example, without departing from the scope of the embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0038] The word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to determining" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)", depending on the context.

[0039] Various structural schematic diagrams of the embodiments disclosed in the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0040] In traditional distribution networks, there are few power electronic devices connected, and the characteristics of the converter are not obvious. Nowadays, more and more converters are connected to the distribution network, and the original characteristics of the distribution network have changed significantly. The converter has strong frequency coupling and interaction characteristics, which enhances the interaction between distribution network nodes. The existing harmonic voltage distribution calculation method ignores the consideration of the characteristics of power electronic equipment, resulting in poor calculation accuracy and cannot meet the calculation requirements under the new distribution network. Compared with the original method, the calculation method proposed in the present invention introduces a description of the converter characteristics, which improves the calculation accuracy of the harmonic voltage distribution of the distribution network.

[0041] The present invention provides an iterative calculation method for harmonic voltage distribution in a distribution network, which adopts the idea of ​​iterative calculation to improve the calculation accuracy of harmonic voltage distribution in a distribution network incorporating multiple power electronic devices. On the basis of traditional harmonic calculation, the harmonic disturbed emission characteristics of the converter are introduced to more comprehensively characterize the harmonic voltage distribution of the distribution network.

[0042] See also Figure 1 The present invention provides an iterative calculation method for harmonic voltage distribution in a power distribution network, comprising the following steps: S1. Obtain the load size of each node of the distribution network and the line impedance between nodes, and determine the access capacity and location of the power electronic converter and harmonic source; S2, obtaining the filter parameters and control method of the power electronic converter in step S1, and obtaining the harmonic emission characteristics of the harmonic source in S1 ; According to the characteristics of the harmonic source, a constant current source model can be used for fitting.

[0043] S3, calculating the fundamental power flow of the distribution network according to the node load conditions and line parameters obtained in step S1; The fundamental power flow calculation method of distribution network is relatively mature, and Newton iteration method is generally used for calculation.

[0044] S4. According to the power flow calculation result of step S3, the load on the distribution network node except the converter is equivalent to a resistance and inductance series load, and the equivalent parameters are calculated; The equivalent impedance is calculated based on the power and voltage of the node. The specific expression is as follows:

[0045] in, R is the equivalent resistance, X is the equivalent reactance, P is the active power of the node, Q is the reactive power of the node, U is the effective value of the voltage at the node, obtained by the power flow calculation in step S3.

[0046] S5. Calculate the harmonic impedance matrix of the grid according to the line parameters obtained in step S1 and the equivalent load obtained in step S4. ; The grid harmonic impedance matrix is ​​the impedance matrix corresponding to each harmonic. The specific calculation process is as follows: Firstly, the line impedance and the equivalent impedance of the load are calculated according to the calculated harmonic frequency; Secondly, list the node admittance matrix of the grid; Then the node admittance matrix is ​​inverted to obtain the final harmonic impedance matrix.

[0047] S6, obtaining the harmonic impedance characteristics of the power electronic converter model according to the filter parameters and controller parameters of the power electronic converter in step S2 ; Power electronic converter models include harmonic state space and impedance modeling methods.

[0048] S7, using the harmonic emission characteristics of the harmonic source in step S2 as the initial harmonic disturbance, combined with the harmonic impedance matrix in step S4, to calculate the initial distribution of the harmonic voltage of the distribution network, ; S8, according to the harmonic voltage distribution in step S7 and the harmonic impedance characteristics of the power electronic converter in step S6, calculate the new harmonic current disturbance of the distribution network ; S9, superimposing the harmonic current disturbance value in step S8 on the initial harmonic disturbance, and combining with the grid harmonic impedance matrix in step S5 to calculate the new harmonic voltage distribution ; Steps S7 to S9 can obtain a more accurate distribution network harmonic voltage distribution result taking into account the converter characteristics through repeated iterations of harmonic voltage distribution and harmonic current calculation.

[0049] S10. Repeat steps S7 to S8 according to the harmonic voltage distribution of step S9 until the harmonic voltage converges.

[0050] It will be appreciated by those skilled in the art that various aspects of the present invention may be implemented as systems, methods or program products. Therefore, various aspects of the present invention may be specifically implemented in the following forms, namely: complete hardware implementation, complete software implementation (including firmware, microcode, etc.), or a combination of hardware and software implementations, which may be collectively referred to herein as "circuits", "modules" or "platforms".

[0051] In another embodiment of the present invention, a distribution network harmonic voltage distribution iterative calculation system is provided, which can be used to implement the above-mentioned distribution network harmonic voltage distribution iterative calculation method. Specifically, the distribution network harmonic voltage distribution iterative calculation system includes a parameter module, a calculation module, a disturbance module, a voltage module and an output module.

[0052] The parameter module obtains the load size of each node of the distribution network, the line impedance between nodes, determines the access capacity and location of the power electronic converter and the harmonic source; obtains the filter parameters of the power electronic converter and its control method, and determines the harmonic emission characteristics of the harmonic source. ; Calculate the fundamental power flow of the distribution network according to the node load conditions and line parameters; The calculation module, based on the power flow calculation results, equates the loads on the distribution network nodes except the converter to the resistance and inductance series loads, and calculates the equivalent parameters; based on the line parameters and equivalent loads, calculates the harmonic impedance matrix of the grid ; The disturbance module obtains the harmonic impedance characteristics of the power electronic converter model according to the filter parameters and controller parameters of the power electronic converter; the harmonic emission characteristics of the harmonic source are used as the initial harmonic disturbance, and combined with the harmonic impedance matrix, the initial distribution of the harmonic voltage of the distribution network is calculated; The voltage module calculates the new harmonic current disturbance of the distribution network according to the harmonic voltage distribution and the harmonic impedance characteristics of the power electronic converter; superimposes the harmonic current disturbance value on the initial harmonic disturbance, and calculates the new harmonic voltage distribution in combination with the grid harmonic impedance matrix; The output module repeats the process according to the new harmonic voltage distribution until the harmonic voltage converges, thus completing the iterative calculation of the harmonic voltage distribution of the distribution network.

[0053] In another embodiment of the present invention, a terminal device is provided, which includes a processor and a memory, wherein the memory is used to store a computer program, the computer program includes program instructions, and the processor is used to execute the program instructions stored in the computer storage medium. The processor may be a central processing unit (CPU), or other general-purpose processors, graphics processors (GPU), tensor processors (TPU), digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc., which are the computing core and control core of the terminal, which are suitable for implementing one or more instructions, and are specifically suitable for loading and executing one or more instructions to implement the corresponding method flow or corresponding functions; the processor described in the embodiment of the present invention can be used for the operation of the iterative calculation method of the harmonic voltage distribution of the distribution network, including: Obtain the load size of each node of the distribution network and the line impedance between nodes, determine the access capacity and location of the power electronic converter and the harmonic source; obtain the filter parameters of the power electronic converter and its control method, and determine the harmonic emission characteristics of the harmonic source ; According to the obtained node load conditions and line parameters, the fundamental power flow of the distribution network is calculated; according to the power flow calculation results, the loads on the distribution network nodes except the converter are equivalent to resistance and inductance series loads, and the equivalent parameters are calculated; according to the obtained line parameters and equivalent loads, the harmonic impedance matrix of the grid is calculated ; The harmonic impedance characteristics of the power electronic converter model are obtained according to the filter parameters and controller parameters of the power electronic converter; the harmonic emission characteristics of the harmonic source are used as the initial harmonic disturbance, combined with the harmonic impedance matrix, to calculate the initial distribution of the harmonic voltage of the distribution network; according to the harmonic voltage distribution and the harmonic impedance characteristics of the power electronic converter, the new harmonic current disturbance of the distribution network is calculated; the harmonic current disturbance value is superimposed on the initial harmonic disturbance, combined with the grid harmonic impedance matrix, to calculate the new harmonic voltage distribution; according to the new harmonic voltage distribution, repeat until the harmonic voltage converges, and complete the iterative calculation of the harmonic voltage distribution of the distribution network.

[0054] See also Figure 4, the terminal device is a computer device, and the computer device 60 of this embodiment includes: a processor 61, a memory 62, and a computer program 63 stored in the memory 62 and executable on the processor 61. When the computer program 63 is executed by the processor 61, the iterative calculation method for the distribution network harmonic voltage distribution in the embodiment is implemented. To avoid repetition, it is not described one by one here. Alternatively, when the computer program 63 is executed by the processor 61, the functions of each model / unit in the iterative calculation system for the distribution network harmonic voltage distribution in the embodiment are implemented. To avoid repetition, it is not described one by one here.

[0055] The computer device 60 may be a computing device such as a desktop computer, a notebook, a PDA, or a cloud server. The computer device 60 may include, but is not limited to, a processor 61 and a memory 62. Those skilled in the art will appreciate that Figure 4 This is only an example of the computer device 60 and does not constitute a limitation of the computer device 60. It may include more or fewer components than shown in the figure, or a combination of certain components, or different components. For example, the computer device may also include input and output devices, network access devices, buses, etc.

[0056] The processor 61 may be a central processing unit (CPU), or other general-purpose processors, graphics processing units (GPU), tensor processing units (TPU), digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or the processor may be any conventional processor, etc.

[0057] The memory 62 may be an internal storage unit of the computer device 60, such as a hard disk or memory of the computer device 60. The memory 62 may also be an external storage device of the computer device 60, such as a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc., equipped on the computer device 60.

[0058] Furthermore, the memory 62 may include both an internal storage unit of the computer device 60 and an external storage device. The memory 62 is used to store computer programs and other programs and data required by the computer device. The memory 62 may also be used to temporarily store data that has been output or is to be output.

[0059] See also Figure 5 , the terminal device is a chip, and the chip 600 of this embodiment includes a processor 622, which may be one or more, and a memory 632 for storing a computer program executable by the processor 622. The computer program stored in the memory 632 may include one or more modules, each corresponding to a set of instructions. In addition, the processor 622 may be configured to execute the computer program to execute the above-mentioned iterative calculation method for the harmonic voltage distribution of the distribution network.

[0060] In addition, the chip 600 may further include a power supply component 626 and a communication component 650, wherein the power supply component 626 may be configured to perform power management of the chip 600, and the communication component 650 may be configured to implement communication, for example, wired or wireless communication, of the chip 600. In addition, the chip 600 may further include an input / output interface 658. The chip 600 may operate based on an operating system stored in the memory 632.

[0061] In another embodiment of the present invention, the present invention also provides a storage medium, specifically a computer-readable storage medium, which is a memory device in a terminal device for storing programs and data. It can be understood that the computer-readable storage medium here can include both the built-in storage medium in the terminal device and the extended storage medium supported by the terminal device. The computer-readable storage medium provides a storage space, which stores the operating system of the terminal. In addition, one or more instructions suitable for being loaded and executed by the processor are also stored in the storage space, and these instructions can be one or more computer programs. It should be noted that the computer-readable storage medium here can be a high-speed RAM memory, or a non-volatile memory (Non-VolatileMemory), such as at least one disk memory.

[0062] One or more instructions stored in a computer-readable storage medium may be loaded and executed by a processor to implement the corresponding steps of the iterative calculation method for harmonic voltage distribution of a power distribution network in the above embodiment; one or more instructions in the computer-readable storage medium may be loaded and executed by a processor as follows: Obtain the load size of each node of the distribution network and the line impedance between nodes, determine the access capacity and location of the power electronic converter and the harmonic source; obtain the filter parameters of the power electronic converter and its control method, and determine the harmonic emission characteristics of the harmonic source ; According to the obtained node load conditions and line parameters, the fundamental power flow of the distribution network is calculated; according to the power flow calculation results, the loads on the distribution network nodes except the converter are equivalent to resistance and inductance series loads, and the equivalent parameters are calculated; according to the obtained line parameters and equivalent loads, the harmonic impedance matrix of the grid is calculated ; The harmonic impedance characteristics of the power electronic converter model are obtained according to the filter parameters and controller parameters of the power electronic converter; the harmonic emission characteristics of the harmonic source are used as the initial harmonic disturbance, combined with the harmonic impedance matrix, to calculate the initial distribution of the harmonic voltage of the distribution network; according to the harmonic voltage distribution and the harmonic impedance characteristics of the power electronic converter, the new harmonic current disturbance of the distribution network is calculated; the harmonic current disturbance value is superimposed on the initial harmonic disturbance, combined with the grid harmonic impedance matrix, to calculate the new harmonic voltage distribution; according to the new harmonic voltage distribution, repeat until the harmonic voltage converges, and complete the iterative calculation of the harmonic voltage distribution of the distribution network.

[0063] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present invention described and shown in the drawings here can usually be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0064] See also Figure 1 , the iterative process of the algorithm is: First, the fundamental power flow is calculated, and the harmonic impedance matrix of the grid is calculated based on the grid information. Secondly, the harmonic current characteristics of the harmonic source in the distribution network are used as harmonic current disturbances, and the harmonic voltage distribution of the distribution network is calculated based on the harmonic impedance matrix of the grid. Then, based on the distribution of harmonic voltages and the model of the converter (with the fundamental power flow result as the steady-state operating point of the converter), the harmonic current emission of the converter is calculated. The harmonic current emission of the converter is superimposed on the harmonic source characteristics to form a new harmonic disturbance characteristic, and iterative calculation is performed.

[0065] See also Figure 2,The verification scenario of the algorithm described is as follows: the scenario contains three nodes, and each node is connected to a 40kW converter device.

[0066] Among them, the harmonic current source and linear load (20kW) are connected to node 1. The specific parameters of the line impedance are shown in the table:

[0067] The simulation verification includes two working conditions: 1) The harmonic current source injects 7th harmonic 100A into the grid; 2) The harmonic current source injects 11th harmonic 50A into the grid.

[0068] Please refer to Figure 3 for the comparison of the algorithm proposed in the present invention and the traditional algorithm and simulation results. Figures 3 (a) and (b) show the distribution and comparison of harmonic voltages at each node of the distribution network under the 7th harmonic current disturbance, where Figures 3 (a) and 3 (b) reflect the iterative calculation process of the harmonic voltage amplitude and phase. Table 1 calculates the accuracy of the proposed method and the comparison of simulation results, and Table 2 compares the results of the traditional calculation method and the simulation results.

[0069] Table 1 Comparison of the method of the present invention and simulation results

[0070] Table 2 Comparison of traditional methods and simulation results

[0071] Figures 3 (c) and (d) show the distribution and comparison of harmonic voltages at each node of the distribution network under the 11th harmonic current disturbance. Figures 3 (c) and (d) reflect the iterative calculation process of the harmonic voltage amplitude and phase. Table 3 calculates the accuracy of the proposed method and the simulation results. Table 4 compares the results of the traditional calculation method with the simulation results.

[0072] Table 3 Comparison of the method of the present invention and simulation results

[0073] Table 4 Comparison of traditional method and simulation results

[0074] According to the comparison results, the solution of the present invention improves the calculation accuracy of the harmonic voltage distribution of the distribution network by introducing the description of the converter characteristics, and the calculation error is less than 5%, which is much higher than the accuracy of traditional calculations.

[0075] In summary, the present invention provides an iterative calculation method and system for harmonic voltage distribution in a distribution network, which takes into account the characteristics of the converter in the traditional harmonic calculation method. By introducing the impedance model of the converter, the output current characteristics of the converter under harmonic voltage disturbance are calculated, and the harmonic voltage distribution of the distribution network is calculated more accurately. The converter has strong frequency coupling and interaction characteristics, which enhances the interaction between the nodes of the distribution network. The existing harmonic voltage distribution calculation method ignores the consideration of the characteristics of power electronic equipment, resulting in poor calculation accuracy and cannot meet the calculation requirements under the new distribution network; compared with the original method, the description of the converter characteristics is introduced to improve the calculation accuracy of the harmonic voltage distribution of the distribution network.

[0076] The technicians in the relevant field can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional units and modules is used as an example for illustration. In practical applications, the above-mentioned function allocation can be completed by different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiment can be integrated in a processing unit, or each unit can exist physically separately, or two or more units can be integrated in one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units. In addition, the specific names of the functional units and modules are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of this application. The specific working process of the units and modules in the above-mentioned system can refer to the corresponding process in the aforementioned method embodiment, which will not be repeated here.

[0077] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0078] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed in the present invention can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0079] In the embodiments provided by the present invention, it should be understood that the disclosed devices / terminals and methods can be implemented in other ways. For example, the device / terminal embodiments described above are only schematic. For example, the division of the modules or 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 integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0080] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, 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 solution of this embodiment.

[0081] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0082] If the integrated module / unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present invention implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium, and the computer program can implement the steps of the above-mentioned various method embodiments when executed by the processor. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may include: any entity or device capable of carrying the computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electric carrier signal, telecommunication signal and software distribution medium, etc. It should be noted that the content contained in the computer-readable medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, computer-readable media do not include electric carrier signals and telecommunication signals.

[0083] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices, and computer program products according to the embodiments of the present application. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of the processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0084] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0085] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0086] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for iterative calculation of harmonic voltage distribution in a distribution network, characterized in that: The following steps are involved: S1. Obtain the load size of each node of the distribution network and the line impedance between nodes, and determine the access capacity and location of the power electronic converter and harmonic source; S2, obtaining the filter parameters of the power electronic converter in step S1 and the control method thereof, and determining the harmonic emission characteristics of the harmonic source in step S1 ; S3, calculating the fundamental power flow of the distribution network according to the node load conditions and line parameters obtained in step S1; S4. According to the power flow calculation result of step S3, the load on the distribution network node except the converter is equivalent to a resistance and inductance series load, and the equivalent parameters are calculated; S5. Calculate the harmonic impedance matrix of the grid according to the line parameters obtained in step S1 and the equivalent load obtained in step S4. ; S6, obtaining the harmonic impedance characteristics of the power electronic converter model according to the filter parameters and controller parameters of the power electronic converter in step S2; S7, using the harmonic emission characteristics of the harmonic source in step S2 as the initial harmonic disturbance, combined with the harmonic impedance matrix in step S4, to calculate the initial distribution of the harmonic voltage of the distribution network; S8. Calculate a new harmonic current disturbance of the distribution network according to the harmonic voltage distribution in step S7 and the harmonic impedance characteristics of the power electronic converter in step S6; S9, superimposing the harmonic current disturbance value in step S8 on the initial harmonic disturbance, and combining with the grid harmonic impedance matrix in step S5 to calculate a new harmonic voltage distribution; S10. According to the harmonic voltage distribution of step S9, steps S7 to S8 are repeated until the harmonic voltage converges, thus completing the iterative calculation of the harmonic voltage distribution of the distribution network.

2. The iterative calculation method for harmonic voltage distribution in a power distribution network according to claim 1, characterized in that: In step S4, the equivalent parameters are calculated as follows: in, R is the equivalent resistance, X is the equivalent reactance, P is the active power of the node, Q is the reactive power of the node, U is the effective value of the voltage at the node.

3. The iterative calculation method for harmonic voltage distribution in a power distribution network according to claim 1, characterized in that: In step S5, the grid harmonic impedance matrix is ​​calculated by respectively calculating the corresponding impedance matrix under each harmonic, and the specific calculation process is as follows: Calculate the line impedance and the equivalent impedance of the load according to the calculated harmonic frequency; list the node admittance matrix of the grid; perform the inverse operation on the node admittance matrix to obtain the final harmonic impedance matrix.

4. The iterative calculation method for harmonic voltage distribution in a power distribution network according to claim 1, characterized in that: In step S6, the power electronic converter model includes harmonic state space and impedance modeling methods.

5. The iterative calculation method for harmonic voltage distribution in a power distribution network according to claim 4, characterized in that: Harmonic Impedance Characteristics of Power Electronic Converters for: in, is the harmonic disturbance voltage, is the harmonic impedance value of the converter.

6. The iterative calculation method for harmonic voltage distribution in a power distribution network according to claim 1, characterized in that: In step S7, the initial distribution of the harmonic voltage of the distribution network for: in, is the harmonic impedance matrix of the grid, is the harmonic emission characteristic of the harmonic source.

7. The iterative calculation method for harmonic voltage distribution in a power distribution network according to claim 1, characterized in that: In step S8, the new harmonic current disturbance of the distribution network for: in, is the initial distribution of harmonic voltage in the distribution network, is the harmonic impedance value of the converter.

8. The iterative calculation method for harmonic voltage distribution in a power distribution network according to claim 1, characterized in that: Steps S7 to S9 obtain more accurate distribution network harmonic voltage distribution results taking into account converter characteristics through repeated iterations of harmonic voltage distribution and harmonic current calculation.

9. The iterative calculation method for harmonic voltage distribution in a power distribution network according to claim 1, characterized in that: In step S9, the new harmonic voltage distribution for: in, is the harmonic impedance matrix of the grid, is the harmonic emission characteristic of the harmonic source, New harmonic current disturbances in the distribution network.

10. A distribution network harmonic voltage distribution iterative calculation system, characterized in that: include: The parameter module obtains the load size of each node in the distribution network, the line impedance between nodes, and determines the access capacity and location of the power electronic converter and harmonic source; Obtain filter parameters and control methods of power electronic converters, and determine harmonic emission characteristics of harmonic sources ; Calculate the fundamental power flow of the distribution network according to the node load conditions and line parameters; The calculation module, based on the power flow calculation results, equates the loads on the distribution network nodes except the converter to the resistance and inductance series loads, and calculates the equivalent parameters; based on the line parameters and equivalent loads, calculates the harmonic impedance matrix of the grid ; The disturbance module obtains the harmonic impedance characteristics of the power electronic converter model according to the filter parameters and controller parameters of the power electronic converter; the harmonic emission characteristics of the harmonic source are used as the initial harmonic disturbance, and combined with the harmonic impedance matrix, the initial distribution of the harmonic voltage of the distribution network is calculated; The voltage module calculates the new harmonic current disturbance of the distribution network according to the harmonic voltage distribution and the harmonic impedance characteristics of the power electronic converter; The harmonic current disturbance value is superimposed on the initial harmonic disturbance, and the new harmonic voltage distribution is calculated by combining the grid harmonic impedance matrix; The output module repeats the process according to the new harmonic voltage distribution until the harmonic voltage converges, thus completing the iterative calculation of the harmonic voltage distribution of the distribution network.

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