Resonance risk assessment method for direct-current circuit of flexible direct-current system and related device

Abstract

The invention discloses a flexible direct current system direct current circuit resonance risk assessment method and a related device. The method comprises the steps of constructing a flexible direct current converter direct current circuit resonance analysis model; constructing a direct-current circuit resonance analysis model of the flexible direct-current power transmission system by combining the direct-current circuit resonance analysis model of the flexible direct-current converter; based on a DC loop resonance analysis model of the flexible DC power transmission system, DC loop impedance frequency characteristics are obtained through frequency scanning; and evaluating the resonance risk of the DC loop of the flexible DC system according to the impedance frequency characteristics of the DC loop. The invention provides a direct-current circuit resonance analysis model of the flexible direct-current converter, and further establishes a direct-current circuit resonance analysis model of the flexible direct-current power transmission system. Furthermore, a risk assessment criterion of the direct-current circuit resonance of the flexible direct-current power transmission system is determined. Therefore, the problem that at present, the flexible direct-current power transmission system still lacks related evaluation methods is solved.

Description

Technical Field

[0001] The present application relates to the technical field of flexible DC system analysis, and in particular to a method for assessing the resonance risk of a DC circuit in a flexible DC system and a related device. Background Art

[0002] The main reason for DC circuit resonance is that the DC circuit impedance has a resonance point near the fundamental frequency or low-order harmonic frequency (mainly 50Hz, 100Hz and 150Hz), or the impedance is too low, which will cause the DC circuit to amplify the harmonics at this frequency or even oscillate. At the same time, the 50Hz DC circuit resonance will cause the DC component of the AC side transformer to be too large, causing the converter transformer to saturate, causing the equipment to heat and vibrate, affecting the safety of the equipment. According to the commutation characteristics of the traditional DC transmission system, the impedance-frequency characteristics of the long-distance DC line, smoothing reactor, DC filter, etc., may cause DC circuit resonance in the traditional DC transmission system.

[0003] At present, there are relatively mature research and evaluation methods for the DC loop resonance of traditional DC transmission systems. However, there is still a lack of relevant evaluation methods for flexible DC transmission systems. At present, due to the "dual carbon" goals and the construction of new power systems, the application of flexible DC transmission will become more and more extensive. Therefore, it is urgent to design a DC loop resonance evaluation method for flexible DC transmission systems, which can be applied to the planning and design of flexible DC transmission systems, judge the DC loop resonance risk in advance, and ensure the safe and stable operation of systems and equipment. Summary of the invention

[0004] The present application provides a method and related device for evaluating the risk of direct current loop resonance in a flexible direct current system, which are used to solve the problem that there is still a lack of relevant evaluation methods for flexible direct current transmission systems.

[0005] In view of this, the first aspect of the present application provides a method for evaluating the risk of DC circuit resonance in a flexible DC system, the method comprising:

[0006] Construct a DC loop resonance analysis model for a flexible DC converter;

[0007] In combination with the DC circuit resonance analysis model of the flexible DC converter, a DC circuit resonance analysis model of the flexible DC transmission system is constructed;

[0008] Based on the DC loop resonance analysis model of the flexible DC power transmission system, the DC loop impedance frequency characteristics are obtained by frequency scanning;

[0009] The resonance risk of the DC circuit of the flexible DC system is evaluated according to the DC circuit impedance frequency characteristic.

[0010] Optionally, the constructing of a DC loop resonance analysis model of a flexible DC converter includes:

[0011] A DC circuit resonance analysis model of a flexible DC converter including m valve groups connected in series is constructed.

[0012] Optionally, the constructing of a DC circuit resonance analysis model of a flexible DC power transmission system in combination with the DC circuit resonance analysis model of the flexible DC converter includes:

[0013] A transmission line frequency-variable parameter model is adopted, combined with the flexible DC converter DC circuit resonance analysis model, to construct a flexible DC transmission system DC circuit resonance analysis model.

[0014] Optionally, the obtaining of the DC link impedance frequency characteristics by frequency scanning based on the DC link resonance analysis model of the flexible DC power transmission system includes:

[0015] Based on the DC link resonance analysis model of the flexible DC power transmission system, after an impulse voltage source is introduced into the DC link to generate a current response, the voltage source voltmeter current is obtained and Fourier analysis is performed to obtain the frequency response characteristics of the DC voltage and the frequency response characteristics of the DC current. According to the frequency response characteristics of the DC voltage and the frequency response characteristics of the DC current, the DC link impedance frequency characteristics are calculated.

[0016] Optionally, the evaluating the resonance risk of the DC circuit of the flexible DC system according to the DC circuit impedance frequency characteristic includes:

[0017] Based on the DC loop impedance frequency characteristics, the DC loop impedance characteristics with DC loop impedance frequency characteristics near 50 Hz, 100 Hz and 150 Hz are calculated respectively, and whether the DC loop has a resonance risk is evaluated according to the DC loop impedance characteristics near 50 Hz, 100 Hz and 150 Hz.

[0018] A second aspect of the present application provides a DC loop resonance risk assessment system for a flexible DC system, the system comprising:

[0019] The first construction unit is used to construct a DC loop resonance analysis model of a flexible DC converter;

[0020] A second construction unit is used to construct a DC circuit resonance analysis model of a flexible DC power transmission system in combination with the DC circuit resonance analysis model of the flexible DC converter;

[0021] An acquisition unit, configured to acquire a DC circuit impedance frequency characteristic by frequency scanning based on the DC circuit resonance analysis model of the flexible DC power transmission system;

[0022] An evaluation unit is used to evaluate the resonance risk of the DC circuit of the flexible DC system according to the DC circuit impedance frequency characteristic.

[0023] Optionally, the first construction unit is specifically used to:

[0024] A DC circuit resonance analysis model of a flexible DC converter including m valve groups connected in series is constructed.

[0025] Optionally, the second construction unit is specifically used to:

[0026] A transmission line frequency-variable parameter model is adopted, combined with the flexible DC converter DC circuit resonance analysis model, to construct a flexible DC transmission system DC circuit resonance analysis model.

[0027] Optionally, the acquisition unit is specifically used to:

[0028] Based on the DC link resonance analysis model of the flexible DC power transmission system, after an impulse voltage source is introduced into the DC link to generate a current response, the voltage source voltmeter current is obtained and Fourier analysis is performed to obtain the frequency response characteristics of the DC voltage and the frequency response characteristics of the DC current. According to the frequency response characteristics of the DC voltage and the frequency response characteristics of the DC current, the DC link impedance frequency characteristics are calculated.

[0029] Optionally, the evaluation unit is specifically used to:

[0030] Based on the DC loop impedance frequency characteristics, the DC loop impedance characteristics with DC loop impedance frequency characteristics near 50 Hz, 100 Hz and 150 Hz are calculated respectively, and whether the DC loop has a resonance risk is evaluated according to the DC loop impedance characteristics near 50 Hz, 100 Hz and 150 Hz.

[0031] It can be seen from the above technical solutions that this application has the following advantages:

[0032] The present application provides a method for assessing the risk of DC circuit resonance in a flexible DC system. First, a DC circuit resonance analysis model of a flexible DC converter is established; secondly, a DC circuit resonance analysis model of a flexible DC transmission system is established; then, the DC circuit resonance is acquired through frequency scanning; finally, the DC circuit impedance characteristics at 50Hz, 100Hz and 150Hz are observed, and the DC circuit resonance of the flexible DC transmission system is clarified through resonance criterion. The present application proposes a DC circuit resonance analysis model of a flexible DC converter, and then establishes a DC circuit resonance analysis model of a flexible DC transmission system, and clarifies the DC circuit resonance risk assessment criterion of a flexible DC transmission system. The present application can be applied to the planning and design of a flexible DC transmission system, to judge the DC circuit resonance risk in advance, and to ensure the safe and stable operation of the system and equipment. This solves the problem that there is still a lack of relevant evaluation methods for flexible DC transmission systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A schematic flow chart of a method for evaluating the risk of direct current loop resonance in a flexible direct current system provided in an embodiment of the present application;

[0034] Figure 2 A schematic diagram of a DC loop resonance analysis model of a flexible DC converter provided in an embodiment of the present application;

[0035] Figure 3 A schematic diagram of a DC loop resonance analysis model for a flexible DC power transmission system provided in an embodiment of the present application;

[0036] Figure 4 It is a structural schematic diagram of a DC loop resonance risk assessment system for a flexible DC system provided in an embodiment of the present application. DETAILED DESCRIPTION

[0037] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0038] See also Figure 1 A method for assessing the risk of direct current circuit resonance in a flexible direct current system provided in an embodiment of the present application includes:

[0039] Step 101: construct a DC loop resonance analysis model of a flexible DC converter.

[0040] Step 102: construct a DC loop resonance analysis model of a flexible DC power transmission system in combination with a DC loop resonance analysis model of a flexible DC converter.

[0041] Step 103: Based on the DC link resonance analysis model of the flexible DC power transmission system, obtain the DC link impedance frequency characteristics through frequency scanning.

[0042] Step 104 : Evaluate the resonance risk of the DC circuit of the flexible DC system according to the DC circuit impedance frequency characteristic.

[0043] In one embodiment, the above step 101 includes:

[0044] A DC circuit resonance analysis model of a flexible DC converter including m valve groups connected in series is constructed.

[0045] It should be noted that if Figure 2As shown in Figure 1, the DC loop resonance analysis model of the converter of the flexible DC transmission system is composed of inductors and capacitors in series, where the inductor L represents the bridge arm reactor and the capacitor C represents the flexible DC module capacitor.

[0046] Generally, the flexible DC is a structure with multiple valve groups in series. If there are m valve groups in series, there are m inductors and m capacitors in series. At the same time, if the flexible DC is equipped with a smoothing reactor, the smoothing reactor L p Connected in series to the corresponding position, a DC loop resonance analysis model of the flexible DC converter is formed.

[0047] In one embodiment, the above step 102 includes:

[0048] The frequency-variable parameter model of the transmission line is used in combination with the DC loop resonance analysis model of the flexible DC converter to construct a DC loop resonance analysis model of the flexible DC transmission system.

[0049] It should be noted that the DC transmission line can be an overhead line or a cable, and the analysis process is the same as the traditional DC analysis process, using the frequency-dependent (Phase) model. Figure 1 The flexible DC converter model shown in the figure can be used to establish a DC loop resonance analysis model for the flexible DC transmission system. The multi-terminal flexible DC transmission system can establish a corresponding model based on the series-parallel relationship of the converter stations.

[0050] In one embodiment, the above step 103 includes:

[0051] Based on the DC link resonance analysis model of the flexible DC transmission system, after introducing an impulse voltage source into the DC link to generate a current response, the voltage source voltmeter current is obtained and Fourier analysis is performed to obtain the frequency response characteristics of the DC voltage and the frequency response characteristics of the DC current. According to the frequency response characteristics of the DC voltage and the frequency response characteristics of the DC current, the DC link impedance frequency characteristics are calculated.

[0052] It should be noted that based on the DC link resonance analysis model of the flexible DC transmission system, a unit impulse voltage source is connected in series in the DC link. After obtaining the current response, Fourier analysis is performed on the voltage source voltmeter current to obtain the frequency response characteristics of the DC voltage and the frequency response characteristics of the DC current, which are U HVDC (f) I HVDC (f), and the DC loop impedance frequency characteristic is calculated by formula (1).

[0053] (1)

[0054] In one embodiment, the above step 104 includes:

[0055] Based on the DC loop impedance frequency characteristics, the DC loop impedance characteristics at frequencies near 50 Hz, 100 Hz and 150 Hz are calculated respectively. Based on the DC loop impedance characteristics at frequencies near 50 Hz, 100 Hz and 150 Hz, it is assessed whether there is a resonance risk in the DC loop.

[0056] It should be noted that the DC circuit impedance frequency characteristics calculated by the above formula (1) are the DC circuit impedance characteristics near 50Hz, 100Hz and 150Hz. If there is a resonance point near the above three frequency points ±6Hz, that is, the phase crosses zero from negative to positive or from positive to negative, the amplitude of the resonance point is at a nearby valley value, and the impedance at the three frequency points is lower than 200 , it is considered that there is a risk of resonance in the DC circuit and suppression measures need to be taken.

[0057] This application proposes a DC circuit resonance risk assessment method for a flexible DC transmission system that can be applied to actual planning, design and engineering applications. First, a DC circuit resonance analysis model for a flexible DC converter is established; secondly, a DC circuit resonance analysis model for a flexible DC transmission system is established; then, the DC circuit resonance is obtained through frequency scanning; finally, the DC circuit impedance characteristics at 50Hz, 100Hz and 150Hz are observed, and the DC circuit resonance of the flexible DC transmission system is clarified through resonance criteria. This application proposes a DC circuit resonance analysis model for a flexible DC converter, and then establishes a DC circuit resonance analysis model for a flexible DC transmission system, and clarifies the DC circuit resonance risk assessment criterion for a flexible DC transmission system. This application can be applied to the planning and design of a flexible DC transmission system, to judge the DC circuit resonance risk in advance, and to ensure the safe and stable operation of the system and equipment.

[0058] The above is a method for assessing the resonance risk of a DC circuit of a flexible DC system provided in an embodiment of the present application. The following is a system for assessing the resonance risk of a DC circuit of a flexible DC system provided in an embodiment of the present application.

[0059] See also Figure 4 A DC loop resonance risk assessment system for a flexible DC system provided in an embodiment of the present application includes:

[0060] The first constructing unit 201 is used to construct a DC loop resonance analysis model of a flexible DC converter.

[0061] The second constructing unit 202 is used to construct a DC loop resonance analysis model of the flexible DC power transmission system in combination with the DC loop resonance analysis model of the flexible DC converter.

[0062] The acquisition unit 203 is configured to acquire the DC link impedance frequency characteristic by frequency scanning based on the DC link resonance analysis model of the flexible DC power transmission system.

[0063] The evaluation unit 204 is used to evaluate the resonance risk of the DC link of the flexible DC system according to the DC link impedance frequency characteristic.

[0064] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0065] The terms "first", "second", "third", "fourth", etc. (if any) in the specification of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein, for example. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0066] It should be understood that in this application, "at least one (item)" means one or more, and "plurality" means two or more. "And / or" is used to describe the association relationship of associated objects, indicating that three relationships may exist. For example, "A and / or B" can mean: only A exists, only B exists, and A and B exist at the same time, where A and B can be singular or plural. The character " / " generally indicates that the objects associated before and after are in an "or" relationship. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, at least one of a, b or c can mean: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, c can be single or multiple.

[0067] In the several embodiments provided in the present application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or 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 an indirect coupling or communication connection through some interfaces, devices or units, which can be electrical, mechanical or other forms.

[0068] 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.

[0069] In addition, each functional unit in each embodiment of the present application 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.

[0070] If the integrated 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 technical solution of the present application is essentially or the part that contributes to the prior art or all or part of the technical solution can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions to enable a computer device (which can be a personal computer, server, or network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (full name in English: Read-Only Memory, English abbreviation: ROM), random access memory (full name in English: Random Access Memory, English abbreviation: RAM), disk or optical disk and other media that can store program codes.

[0071] As described above, the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for assessing the risk of DC loop resonance in a flexible DC system, characterized in that: include: Construct a DC loop resonance analysis model for a flexible DC converter; In combination with the DC circuit resonance analysis model of the flexible DC converter, a DC circuit resonance analysis model of the flexible DC transmission system is constructed; Based on the DC loop resonance analysis model of the flexible DC power transmission system, the DC loop impedance frequency characteristics are obtained by frequency scanning; The resonance risk of the DC circuit of the flexible DC system is evaluated according to the DC circuit impedance frequency characteristic.

2. The method for evaluating the risk of DC circuit resonance in a flexible DC system according to claim 1, characterized in that: The constructing of the DC loop resonance analysis model of the flexible DC converter includes: A DC circuit resonance analysis model of a flexible DC converter including m valve groups connected in series is constructed.

3. The method for evaluating the risk of DC circuit resonance in a flexible DC system according to claim 1, characterized in that: The method of combining the DC circuit resonance analysis model of the flexible DC converter to construct a DC circuit resonance analysis model of the flexible DC power transmission system includes: A transmission line frequency-variable parameter model is adopted, combined with the flexible DC converter DC circuit resonance analysis model, to construct a flexible DC transmission system DC circuit resonance analysis model.

4. The method for evaluating the risk of DC circuit resonance in a flexible DC system according to claim 1, characterized in that: The method of obtaining the DC circuit impedance frequency characteristic by frequency scanning based on the DC circuit resonance analysis model of the flexible DC power transmission system includes: Based on the DC link resonance analysis model of the flexible DC power transmission system, after an impulse voltage source is introduced into the DC link to generate a current response, the voltage source voltmeter current is obtained and Fourier analysis is performed to obtain the frequency response characteristics of the DC voltage and the frequency response characteristics of the DC current. According to the frequency response characteristics of the DC voltage and the frequency response characteristics of the DC current, the DC link impedance frequency characteristics are calculated.

5. The method for evaluating the risk of DC circuit resonance in a flexible DC system according to claim 1, characterized in that: The step of evaluating the resonance risk of the DC circuit of the flexible DC system according to the DC circuit impedance frequency characteristic includes: Based on the DC loop impedance frequency characteristics, the DC loop impedance characteristics with DC loop impedance frequency characteristics near 50 Hz, 100 Hz and 150 Hz are calculated respectively, and whether the DC loop has a resonance risk is evaluated according to the DC loop impedance characteristics near 50 Hz, 100 Hz and 150 Hz.

6. A DC loop resonance risk assessment system for a flexible DC system, characterized in that: include: The first construction unit is used to construct a DC loop resonance analysis model of a flexible DC converter; A second construction unit is used to construct a DC circuit resonance analysis model of a flexible DC power transmission system in combination with the DC circuit resonance analysis model of the flexible DC converter; An acquisition unit, configured to acquire a DC circuit impedance frequency characteristic by frequency scanning based on the DC circuit resonance analysis model of the flexible DC power transmission system; An evaluation unit is used to evaluate the resonance risk of the DC circuit of the flexible DC system according to the DC circuit impedance frequency characteristic.

7. The DC loop resonance risk assessment system of a flexible DC system according to claim 6, characterized in that: The first building unit is specifically used for: A DC circuit resonance analysis model of a flexible DC converter including m valve groups connected in series is constructed.

8. The DC link resonance risk assessment system of a flexible DC system according to claim 6, characterized in that: The second building block is specifically used for: A transmission line frequency-variable parameter model is adopted, combined with the flexible DC converter DC circuit resonance analysis model, to construct a flexible DC transmission system DC circuit resonance analysis model.

9. The DC loop resonance risk assessment system of a flexible DC system according to claim 6, characterized in that: The acquisition unit is specifically used for: Based on the DC link resonance analysis model of the flexible DC power transmission system, after an impulse voltage source is introduced into the DC link to generate a current response, the voltage source voltmeter current is obtained and Fourier analysis is performed to obtain the frequency response characteristics of the DC voltage and the frequency response characteristics of the DC current. According to the frequency response characteristics of the DC voltage and the frequency response characteristics of the DC current, the DC link impedance frequency characteristics are calculated.

10. The DC loop resonance risk assessment system of a flexible DC system according to claim 6, characterized in that: The evaluation unit is specifically used for: Based on the DC loop impedance frequency characteristics, the DC loop impedance characteristics with DC loop impedance frequency characteristics near 50 Hz, 100 Hz and 150 Hz are calculated respectively, and whether the DC loop has a resonance risk is evaluated according to the DC loop impedance characteristics near 50 Hz, 100 Hz and 150 Hz.

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