Method for evaluating subsynchronous torsional vibration interaction between thermal power and direct current and related device

Abstract

The invention discloses a thermal power and direct current subsynchronous torsional vibration interaction assessment method and related device, and the method comprises the steps: calculating a first electrical damping and a first reactance drop coefficient seen from a neutral point of a thermal power generating unit when a high-voltage direct current power transmission system exists, and judging whether the thermal power generating unit has a torsional vibration risk or not to obtain a first analysis result; when the torsional vibration risk exists, disconnecting the high-voltage direct-current power transmission system from the power system, calculating second electrical damping and a second reactance drop coefficient seen from the neutral point of the thermal power generating unit when the high-voltage direct-current power transmission system does not exist, and judging whether the thermal power generating unit has the torsional vibration risk or not to obtain a second analysis result; and comparing the first analysis result with the second analysis result, and matching a comparison result with a preset condition to obtain an evaluation result of the subsynchronous torsional vibration interaction between the thermal power and the direct current. Therefore, the problem that the prior art is not suitable for actual planning design and engineering application is solved.

Description

Technical Field

[0001] This application relates to the technical field of power system state analysis, and particularly relates to a method and related device for evaluating the interaction of subsynchronous torsional vibration between thermal power and direct current. Background Art

[0002] With the vigorous development of the construction of large-scale thermal power bases supporting new energy, the mode of sending large-scale steam turbine generator sets through high-voltage direct current transmission will become increasingly common. However, the risk of subsynchronous oscillation caused by high-voltage direct current transmission systems also increases accordingly. Specifically, for example, when subsynchronous torsional vibration occurs between thermal power units and direct current transmission systems, it may cause serious mechanical stress on the shafting of thermal power units. Under long-term action, it may lead to shafting fatigue, cracks, or even direct fracture, posing a serious threat to the safety of equipment and further affecting the stable operation of the power system. Therefore, in order to timely detect and eliminate such potential unstable factors, it is necessary to carry out an assessment of the interaction of subsynchronous torsional vibration between thermal power and direct current to ensure the stable operation of the power system, guarantee the safe operation of equipment, and provide strong technical support for the optimal design and operation of the power system.

[0003] Currently, there are mainly four methods for evaluating the interaction of subsynchronous torsional vibration between thermal power and direct current: 1. Unit Interaction Factor (UIF) analysis method; 2. Radiality Factor analysis method; 3. Complex torque coefficient method; 4. Eigenvalue analysis method. Among them, the Unit Interaction Factor (UIF) analysis method can simply and quickly scan the risk of subsynchronous torsional vibration between units and direct current in the system, and is suitable for actual planning and design and engineering applications. However, this method is only applicable to scenarios without series compensation in the system; the Radiality Factor analysis method solves the problem that the unit interaction coefficient analysis method cannot be applied to systems with series compensation, but is only limited to systems with only 2 devices that may respond to the interaction of subsynchronous torsional vibration; the complex torque coefficient method and the eigenvalue analysis method have high accuracy, but also have high modeling complexity, so they are not very suitable for actual planning and design and engineering applications.

[0004] Therefore, there is an urgent need to design a method for evaluating the interaction of subsynchronous torsional vibration between thermal power and direct current that can be applied to actual planning and design and engineering applications. Summary of the Invention

[0005] This application provides a method and related device for evaluating the interaction of subsynchronous torsional vibration between thermal power and direct current, which is used to solve the problem that the existing technology is not applicable to actual planning and design and engineering applications.

[0006] In view of this, the first aspect of the present application provides a method for evaluating the interaction of subsynchronous torsional vibration between thermal power and direct current, which is applied to a power system including a thermal power unit and a high-voltage direct current transmission system;

[0007] The method includes:

[0008] Calculating a first electrical damping and a first reactance drop coefficient seen from the neutral point of the thermal power unit when the high-voltage direct current transmission system exists;

[0009] Judging whether the thermal power unit has torsional vibration risk respectively according to the first electrical damping and the first reactance drop coefficient, and obtaining a first analysis result;

[0010] When there is torsional vibration risk, disconnect the connection between the high-voltage direct current transmission system and the power system, and calculate a second electrical damping and a second reactance drop coefficient seen from the neutral point of the thermal power unit when the high-voltage direct current transmission system does not exist;

[0011] Judging whether the thermal power unit has torsional vibration risk respectively according to the second electrical damping and the second reactance drop coefficient, and obtaining a second analysis result;

[0012] Comparing the first analysis result with the second analysis result, and matching the comparison result with a preset condition to obtain an evaluation result of the interaction of subsynchronous torsional vibration between thermal power and direct current.

[0013] Optionally, the calculating the first electrical damping and the first reactance drop coefficient seen from the neutral point of the thermal power unit when the high-voltage direct current transmission system exists includes:

[0014] Performing frequency scanning from the low-voltage side port of the step-up transformer of the thermal power unit to the remaining part of the power system to obtain the power system impedance;

[0015] Calculating the subsynchronous impedance of the generator of the thermal power unit;

[0016] Calculating the total impedance seen from the neutral point of the generator according to the power system impedance and the subsynchronous impedance;

[0017] Calculating the first electrical damping according to the total impedance, and calculating the first reactance drop coefficient.

[0018] Optionally, the calculating the subsynchronous impedance of the generator of the thermal power unit includes:

[0019] Based on the subsynchronous impedance calculation formula, calculating the subsynchronous impedance of the generator of the thermal power unit;

[0020] Wherein, the subsynchronous impedance calculation formula is:

[0021] ;

[0022] Wherein, is the sub-synchronous impedance, is the rated frequency of the power system, is the generator armature resistance of the thermal power unit, is the equivalent rotor resistance, is the slip coefficient, is a certain electrical frequency to be studied, is an imaginary expression, , is the equivalent sub-transient reactance.

[0023] Optionally, calculating the total impedance seen from the neutral point of the generator according to the power system impedance and the sub-synchronous impedance includes:

[0024] Adding the power system impedance and the sub-synchronous impedance to obtain the total impedance seen from the neutral point of the generator, and the calculation expression of the total impedance is:

[0025] ;

[0026] Wherein, is the total impedance, is the power system impedance, is the sub-synchronous impedance.

[0027] Optionally, judging whether the thermal power unit has torsional vibration risk according to the first electrical damping and the first reactance drop coefficient respectively, and obtaining a first analysis result includes:

[0028] Within the preset range of the natural torsional vibration frequency of the thermal power unit, when the first electrical damping is less than a first preset value, it is determined that the thermal power unit has torsional vibration risk;

[0029] Within the preset range of the electrical frequency corresponding to the natural torsional vibration frequency of the thermal power unit, when the first reactance drop coefficient is greater than a second preset value, it is determined that the thermal power unit has torsional vibration risk.

[0030] Optionally, the preset conditions include:

[0031] The first preset sub-condition: The torsional vibration risk already exists when the HVDC transmission system does not exist, and after the HVDC transmission system exists, compared with when the HVDC transmission system does not exist, the impedance characteristics of the thermal power unit have not changed;

[0032] Second preset sub - condition: The torsional vibration risk already exists when the HVDC transmission system does not exist, and after the HVDC transmission system exists, compared with when the HVDC transmission system does not exist, the impedance characteristics of the thermal power unit change.

[0033] Optionally, the comparing the first analysis result with the second analysis result, and matching the comparison result with a preset condition to obtain an evaluation result of the subsynchronous torsional vibration interaction between the thermal power and the DC includes:

[0034] Compare the first analysis result with the second analysis result, and match the comparison result with a preset condition;

[0035] If one of the preset conditions is met, it is determined that the subsynchronous torsional vibration interaction between the HVDC transmission system and the thermal power unit will not cause the thermal power unit to vibrate torsionally; otherwise, it is determined that the subsynchronous torsional vibration interaction between the HVDC transmission system and the thermal power unit may cause the thermal power unit to vibrate torsionally.

[0036] The second aspect of the present application provides a subsynchronous torsional vibration interaction evaluation system between thermal power and DC, which is applied to a power system including a thermal power unit and an HVDC transmission system;

[0037] The system includes:

[0038] A first calculation unit for calculating the first electrical damping and the first reactance drop coefficient seen from the neutral point of the thermal power unit when the HVDC transmission system exists;

[0039] A first analysis unit for respectively judging whether the thermal power unit has a torsional vibration risk according to the first electrical damping and the first reactance drop coefficient to obtain a first analysis result;

[0040] A second calculation unit for disconnecting the connection between the HVDC transmission system and the power system when there is a torsional vibration risk, and calculating the second electrical damping and the second reactance drop coefficient seen from the neutral point of the thermal power unit when the HVDC transmission system does not exist;

[0041] A second analysis unit for respectively judging whether the thermal power unit has a torsional vibration risk according to the second electrical damping and the second reactance drop coefficient to obtain a second analysis result;

[0042] An evaluation unit for comparing the first analysis result with the second analysis result, and matching the comparison result with a preset condition to obtain an evaluation result of the subsynchronous torsional vibration interaction between thermal power and DC.

[0043] A third aspect of the present application provides an evaluation device for the subsynchronous torsional interaction between thermal power and direct current. The device includes a processor and a memory:

[0044] The memory is used to store program codes and transmit the program codes to the processor;

[0045] The processor is configured to execute the steps of the evaluation method for the subsynchronous torsional interaction between thermal power and direct current as described in the first aspect above according to the instructions in the program codes.

[0046] A fourth aspect of the present application provides a computer-readable storage medium, which is used to store program codes, and the program codes are used to execute the evaluation method for the subsynchronous torsional interaction between thermal power and direct current as described in the first aspect above.

[0047] It can be seen from the above technical solutions that the present application has the following advantages:

[0048] (1) The evaluation method for the subsynchronous torsional interaction between thermal power and direct current of the present application conducts analysis and research based on frequency scanning, combines the magnitude of the electrical damping / reactance drop coefficient seen from the neutral point of the thermal power unit and the influence of the high-voltage direct current transmission system on the electrical damping / reactance drop coefficient, and clarifies the subsynchronous torsional interaction between thermal power and the high-voltage direct current transmission system. The method of the present application is simple and highly feasible, the obtained results are relatively vivid and intuitive, and it can be conveniently used for actual planning, design and engineering applications.

[0049] (2) The evaluation method for the subsynchronous torsional interaction between thermal power and direct current of the present application does not involve complex modeling and calculation, and various existing power grid analysis tools can complete this research. At the same time, this method looks into the power system from the neutral point of the generator, and can retain the influence of series compensation equipment and other equipment in the system that can respond to the subsynchronous frequency band on the results. It is also applicable to power systems containing multiple devices that may respond to subsynchronous torsional interaction, and the accuracy is relatively high. Description of the Drawings

[0050] Figure 1 It is a schematic flowchart of an evaluation method for the subsynchronous torsional interaction between thermal power and direct current provided in an embodiment of the present application;

[0051] Figure 2 It is a schematic structural diagram of an evaluation system for the subsynchronous torsional interaction between thermal power and direct current provided in an embodiment of the present application. Detailed Embodiments

[0052] To enable those skilled in the art to better understand the solution of this application, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts belong to the scope of protection of this application.

[0053] Please refer to Figure 1 , a method for evaluating the interaction of subsynchronous torsional vibration between thermal power and DC, provided in the embodiments of this application, is applied to a power system including a thermal power unit and a high-voltage DC transmission system;

[0054] The method includes:

[0055] Step 101: Calculate the first electrical damping and the first reactance drop coefficient seen from the neutral point of the thermal power unit when there is a high-voltage DC transmission system.

[0056] In one embodiment, step 101 includes the following steps:

[0057] Step 1011: Perform a frequency scan from the low-voltage side port of the step-up transformer of the thermal power unit to the remaining part of the power system to obtain the power system impedance.

[0058] It should be noted that performing a frequency scan from the low-voltage side port of the step-up transformer of the thermal power unit to the remaining part of the power system can be understood as that the thermal power unit outputs through the high-voltage DC transmission system. That is to say, the direction from the thermal power unit port to the high-voltage DC transmission system is the remaining part of the power system, and the power system impedance in the frequency band of 1 to 100 Hz is obtained, and the expression is: .

[0059] Step 1012: Calculate the subsynchronous impedance of the generator of the thermal power unit.

[0060] It should be noted that the subsynchronous impedance of the generator of the thermal power unit itself is calculated by the following formula (1).

[0061] (1)

[0062] In the formula, is the subsynchronous impedance, is the rated frequency of the power system, is the armature resistance of the generator of the thermal power unit, is the equivalent rotor resistance shown in formula (2), is the slip coefficient as shown in formula (3), is a certain electrical frequency to be studied, is, is the equivalent subtransient reactance as shown in formula (4).

[0063] (2)

[0064] Wherein, and are respectively the sub-transient reactances of the shaft and the shaft of the thermal power unit, and are respectively the sub-transient open-circuit time constants of the shaft and the shaft of the thermal power unit, is the rated angular frequency of the system.

[0065] (3)

[0066] (4)

[0067] Step 1013: Calculate the total impedance seen from the neutral point of the generator according to the power system impedance and the sub-synchronous impedance.

[0068] It should be noted that adding the power system impedance and the sub-synchronous impedance gives the total impedance seen from the neutral point of the generator. The calculation expression of the total impedance is:

[0069] ;

[0070] Wherein, is the total impedance, is the power system impedance, is the sub-synchronous impedance.

[0071] Step 1014: Calculate the first electrical damping according to the total impedance and calculate the first reactance drop coefficient.

[0072] Step 102: Judge whether the thermal power unit has torsional vibration risk according to the first electrical damping and the first reactance drop coefficient respectively, and obtain the first analysis result.

[0073] In one embodiment, step 102 includes:

[0074] Within the preset range of the natural torsional vibration frequency of the thermal power unit, when the first electrical damping is less than the first preset value, it is determined that the thermal power unit has torsional vibration risk;

[0075] Within the preset range of the electrical frequency corresponding to the natural torsional vibration frequency of the thermal power unit, when the first reactance drop coefficient is greater than the second preset value, it is determined that the thermal power unit has torsional vibration risk.

[0076] Regarding Step 1014 - Step 102, it should be noted that the electrical damping and reactance drop coefficient seen from the neutral point of the thermal power unit are calculated, and whether there is torsional vibration risk in the thermal power unit is evaluated through the torsional vibration criterion.

[0077] Among them:

[0078] 1) Electrical damping calculation and torsional vibration risk criterion.

[0079] The electrical damping at a certain mechanical frequency of the thermal power unit will be calculated by Equation (5).

[0080] (5)

[0081] It should be noted that the preset range of the natural torsional vibration frequency of the thermal power unit is selected according to actual needs. In this embodiment, the natural torsional vibration frequency of the thermal power unit is selected near ±1Hz. Specifically, if the electrical damping within ±1Hz near the natural torsional vibration frequency of the thermal power unit is less than 0.1, it is considered that the thermal power unit has torsional vibration risk.

[0082] 2) Reactance drop coefficient calculation and torsional vibration risk criterion.

[0083] It should be noted that the preset range of the electrical frequency corresponding to the natural torsional vibration frequency of the thermal power unit is selected according to actual needs. In this embodiment, the electrical frequency corresponding to the natural torsional vibration frequency of the thermal power unit is selected within the range near ±3Hz. Specifically, the electrical frequency corresponding to the mechanical natural torsional vibration frequency of the thermal power unit is selected within the range near ±3Hz of (rated frequency - natural torsional vibration frequency), in the region, the maximum and minimum reactances, and the reactance drop coefficient is calculated according to Equation (6).

[0084] (6)

[0085] In the formula, is the maximum reactance, is the minimum reactance.

[0086] If is greater than 5%, it is considered that the thermal power unit has torsional vibration risk.

[0087] Step 103: When there is torsional vibration risk, disconnect the connection between the HVDC transmission system and the power system, and calculate the second electrical damping and the second reactance drop coefficient seen from the neutral point of the thermal power unit when there is no HVDC transmission system.

[0088] It should be noted that if there is torsional vibration risk, disconnect the connection between the HVDC transmission system and the power grid system, and repeat the scan again according to the method in Step 1011 to obtain the electrical damping, electrical impedance and reactance drop coefficient seen from the neutral point of the thermal power unit when there is no HVDC transmission system.

[0089] Step 104: Determine whether the thermal power unit has torsional vibration risk based on the second electrical damping and the second reactance drop coefficient respectively, and obtain the second analysis result.

[0090] It should be noted that the method for determining the torsional vibration risk according to Step 102 above will not be elaborated here.

[0091] Step 105: Compare the first analysis result with the second analysis result, and match the comparison result with the preset conditions to obtain the evaluation result of the subsynchronous torsional vibration interaction between the thermal power and the DC.

[0092] In one embodiment, Step 105 includes:

[0093] Compare the first analysis result with the second analysis result, and match the comparison result with the preset conditions;

[0094] If one of the preset conditions is satisfied, it is determined that the subsynchronous torsional vibration interaction between the HVDC transmission system and the thermal power unit will not cause the thermal power unit to have torsional vibration. Otherwise, it is determined that the subsynchronous torsional vibration interaction between the HVDC transmission system and the thermal power unit may cause the thermal power unit to have torsional vibration.

[0095] Among them, the preset conditions include:

[0096] The first preset sub-condition: The torsional vibration risk already exists when the HVDC transmission system does not exist, and after the HVDC transmission system exists, the impedance characteristics of the thermal power unit have not changed compared with when the HVDC transmission system does not exist;

[0097] The second preset sub-condition: The torsional vibration risk already exists when the HVDC transmission system does not exist, and after the HVDC transmission system exists, the impedance characteristics of the thermal power unit have changed compared with when the HVDC transmission system does not exist.

[0098] It should be noted that by comparing the electrical damping and the drop coefficient when the HVDC transmission system exists and does not exist, if any one of the following two preset sub-conditions is satisfied, it is determined that the subsynchronous torsional vibration interaction between the HVDC transmission system and the thermal power unit will not cause the thermal power unit to have torsional vibration. On the contrary, it is determined that the subsynchronous torsional vibration interaction between the HVDC transmission system and the thermal power unit may cause the thermal power unit to have torsional vibration.

[0099] The first preset sub-condition: The torsional vibration risk already exists when the HVDC transmission system does not exist, and compared with when the HVDC transmission system does not exist, the impedance characteristics of the thermal power unit have basically not changed after the HVDC transmission system exists;

[0100] Second preset sub - condition: The torsional vibration risk already exists when the HVDC transmission system does not exist, and compared with the situation without the HVDC transmission system, the impedance characteristics of the thermal power unit have been improved (such as (including in the HVDC transmission system) > (not including DC), (including in the HVDC transmission system) < (not including in the HVDC transmission system)).

[0101] An evaluation method for the subsynchronous torsional vibration interaction between thermal power and DC provided by this application. First, scan from the thermal power unit port to the rest of the system to obtain the system impedance; secondly, calculate the subsynchronous impedance of the generator of the thermal power unit, and add it to the impedance of the power system to obtain the total impedance seen from the neutral point of the thermal power unit; then, calculate the electrical damping and reactance drop - off coefficient seen from the neutral point of the thermal power unit through the total impedance, and evaluate whether there is a torsional vibration risk in the thermal power unit through the torsional vibration criterion. If there is a risk, disconnect the connection between the HVDC transmission system and the power grid, and repeat the scan again to obtain the electrical impedance and reactance drop - off coefficient seen from the neutral point of the thermal power unit when the HVDC transmission system does not exist. Compare the impedance characteristics when the HVDC transmission system exists and when it does not exist. If the torsional vibration risk already exists when the HVDC transmission system does not exist, and compared with the situation without the HVDC transmission system, the impedance characteristics of the thermal power unit basically remain unchanged or have been improved (such as the damping is enhanced and the reactance drop - off is reduced) after the HVDC transmission system exists, it can be shown that the subsynchronous torsional vibration interaction between the HVDC transmission system and the thermal power does not cause torsional vibration of the thermal power unit. If the opposite is true, it means that the subsynchronous torsional vibration interaction between the HVDC transmission system and the thermal power may cause torsional vibration of the thermal power unit, and further time - domain simulation verification is required.

[0102] The above is an evaluation method for the subsynchronous torsional vibration interaction between thermal power and DC provided in the embodiments of this application. The following is an evaluation system for the subsynchronous torsional vibration interaction between thermal power and DC provided in the embodiments of this application.

[0103] Please refer to Figure 2 , an evaluation system for the subsynchronous torsional vibration interaction between thermal power and DC provided in the embodiments of this application, which is applied to a power system including a thermal power unit and an HVDC transmission system;

[0104] The system includes:

[0105] The first calculation unit 201 is used to calculate the first electrical damping and the first reactance drop - off coefficient seen from the neutral point of the thermal power unit when the HVDC transmission system exists.

[0106] The first analysis unit 202 is configured to determine whether there is a torsional vibration risk in the thermal power unit according to the first electrical damping and the first reactance drop coefficient respectively, and obtain a first analysis result.

[0107] The second calculation unit 203 is configured to disconnect the connection between the HVDC transmission system and the power system when there is a torsional vibration risk, and calculate the second electrical damping and the second reactance drop coefficient seen from the neutral point of the thermal power unit when the HVDC transmission system does not exist.

[0108] The second analysis unit 204 is configured to determine whether there is a torsional vibration risk in the thermal power unit according to the second electrical damping and the second reactance drop coefficient respectively, and obtain a second analysis result.

[0109] The evaluation unit 205 is configured to compare the first analysis result with the second analysis result, match the comparison result with a preset condition, and obtain an evaluation result of the subsynchronous torsional vibration interaction between the thermal power and the DC.

[0110] Furthermore, an evaluation device for subsynchronous torsional vibration interaction between thermal power and DC is provided in an embodiment of the present application. The device includes a processor and a memory:

[0111] The memory is configured to store program codes and transmit the program codes to the processor;

[0112] The processor is configured to execute the steps of the method for evaluating the subsynchronous torsional vibration interaction between thermal power and DC as described in the foregoing method embodiment according to the instructions in the program codes.

[0113] Furthermore, a computer-readable storage medium is provided in an embodiment of the present application. The computer-readable storage medium is configured to store program codes, and the program codes are used to execute the method for evaluating the subsynchronous torsional vibration interaction between thermal power and DC as described in the foregoing method embodiment.

[0114] Those skilled in the art can clearly understand that for the convenience and brevity of description, the specific working processes of the above-described systems and units can refer to the corresponding processes in the foregoing method embodiments, and will not be described herein again.

[0115] In the description of this application and the above-mentioned accompanying drawings, the terms "first", "second", "third", "fourth", etc. (if any) are used to distinguish similar objects and do not necessarily describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances so that the embodiments of this application described here can be implemented in an order different from those illustrated or described here. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that comprises a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0116] It should be understood that in this application, "at least one (item)" means one or more, and "a plurality" means two or more. "And / or" is used to describe the association relationship of associated objects and indicates that there can be three relationships. For example, "A and / or B" can mean: only A exists, only B exists, and both A and B exist at the same time. Among them, A and B can be singular or plural. The character " / " generally means that the associated objects before and after are in an "or" relationship. "At least one (one) of the following" or its similar expressions refer to any combination of these items, including any combination of single items (ones) or plural items (ones). For example, at least one (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.

[0117] In several embodiments provided by this 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 merely illustrative. For example, the division of the units is only a logical function division, and there can be other division methods in actual implementation. For example, 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 displayed or discussed coupling or direct coupling or communication connection to each other can be through some interfaces, and the indirect coupling or communication connection of devices or units can be in electrical, mechanical or other forms.

[0118] The units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they can be located in one place or distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0119] In addition, in each embodiment of the present application, each functional unit can be integrated into a processing unit, or each unit can exist physically alone, or two or more units can be integrated into one unit. The above integrated unit can be implemented in the form of hardware or in the form of a software functional unit.

[0120] If the above 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, in essence, or the part that contributes to the prior art, or all or part of this technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in each embodiment of the present application. The foregoing storage medium includes: various media that can store program codes, such as USB flash drives, mobile hard disks, read-only memories (English full name: Read-Only Memory, English abbreviation: ROM), random access memories (English full name: Random Access Memory, English abbreviation: RAM), magnetic disks, or optical discs.

[0121] 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 foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of each embodiment of the present application.

Claims

1. A method for evaluating the interaction between thermal power and DC subsynchronous torsional vibration, characterized in that: Applicable to power systems including thermal power units and high-voltage direct current transmission systems; Methods include: Calculating the first electrical damping and the first reactance drop coefficient of the neutral point of the thermal power generation unit when the high voltage direct current transmission system exists; Determining whether the thermal power unit has a torsional vibration risk according to the first electrical damping and the first reactance drop coefficient, respectively, to obtain a first analysis result; When there is a risk of torsional vibration, disconnect the high-voltage direct current transmission system from the power system, and calculate the second electrical damping and the second reactance drop coefficient of the neutral point of the thermal power unit when the high-voltage direct current transmission system does not exist; Determining whether the thermal power unit has a torsional vibration risk according to the second electrical damping and the second reactance drop coefficient, respectively, to obtain a second analysis result; The first analysis result is compared with the second analysis result, and the comparison result is matched with the preset conditions to obtain an evaluation result of the subsynchronous torsional vibration interaction between thermal power and direct current.

2. The method for evaluating the interaction between thermal power and DC subsynchronous torsional vibration according to claim 1 is characterized in that: The calculation of the first electrical damping and the first reactance drop coefficient observed at the neutral point of the thermal power generation unit when the high voltage direct current transmission system exists includes: Perform frequency scanning from the step-up and low-voltage side port of the thermal power unit to the rest of the power system to obtain the power system impedance; Calculating the subsynchronous impedance of the generator of the thermal power unit; Calculate the total impedance seen by the neutral point of the generator according to the power system impedance and the subsynchronous impedance; A first electrical damping is calculated based on the total impedance, and a first reactance drop coefficient is calculated.

3. The method for evaluating the interaction between thermal power and direct current subsynchronous torsional vibration according to claim 2 is characterized in that: The calculating the subsynchronous impedance of the generator of the thermal power unit comprises: Calculating the subsynchronous impedance of the generator of the thermal power unit based on a subsynchronous impedance calculation formula; Wherein, the subsynchronous impedance calculation formula is: ； In the formula, is the subsynchronous impedance, is the rated frequency of the power system, is the armature resistance of the generator of the thermal power unit, is the equivalent rotor resistance, is the slip coefficient, is a certain electrical frequency to be studied, is an imaginary number expression, , is the equivalent subtransient reactance.

4. The method for evaluating the interaction between thermal power and DC subsynchronous torsional vibration according to claim 2 is characterized in that: The calculating the total impedance seen by the neutral point of the generator according to the power system impedance and the subsynchronous impedance comprises: The power system impedance and the subsynchronous impedance are added together to obtain the total impedance seen by the neutral point of the generator. The calculation expression of the total impedance is: ； In the formula, is the total impedance, is the power system impedance, is the sub-synchronous impedance.

5. The method for evaluating the interaction between thermal power and direct current subsynchronous torsional vibration according to claim 1, characterized in that: The determining whether the thermal power unit has a torsional vibration risk according to the first electrical damping and the first reactance drop coefficient to obtain a first analysis result includes: Within the preset range of the natural torsional vibration frequency of the thermal power unit, when the first electrical damping is less than a first preset value, it is determined that the thermal power unit has a torsional vibration risk; Within the preset range of the electrical frequency corresponding to the natural torsional vibration frequency of the thermal power unit, when the first reactance drop coefficient is greater than a second preset value, it is determined that the thermal power unit has a torsional vibration risk.

6. The method for evaluating the interaction between thermal power and direct current subsynchronous torsional vibration according to claim 1, characterized in that: The preset conditions include: First preset sub-condition: the torsional vibration risk already exists when the high-voltage direct current transmission system does not exist, and the impedance characteristics of the thermal power generation unit do not change after the high-voltage direct current transmission system exists compared to when the high-voltage direct current transmission system does not exist; The second preset sub-condition: the torsional vibration risk already exists when the high-voltage direct current transmission system does not exist, and the impedance characteristics of the thermal power unit change after the high-voltage direct current transmission system exists compared to when the high-voltage direct current transmission system does not exist.

7. The method for evaluating subsynchronous torsional vibration interaction between thermal power and direct current according to claim 1, characterized in that: The first analysis result is compared with the second analysis result, and the comparison result is matched with a preset condition to obtain an evaluation result of the subsynchronous torsional vibration interaction between thermal power and direct current, including: Comparing the first analysis result with the second analysis result, and matching the comparison result with a preset condition; If one of the preset conditions is met, it is determined that the subsynchronous torsional vibration interaction between the high-voltage direct current transmission system and the thermal power unit will not cause torsional vibration of the thermal power unit; otherwise, it is determined that the subsynchronous torsional vibration interaction between the high-voltage direct current transmission system and the thermal power unit may cause torsional vibration of the thermal power unit.

8. A system for evaluating the interaction between thermal power and DC subsynchronous torsional vibration, characterized in that: Applicable to power systems including thermal power units and high-voltage direct current transmission systems; The system includes: A first calculation unit is used to calculate a first electrical damping and a first reactance drop coefficient observed at a neutral point of a thermal power generation unit when the high voltage direct current transmission system exists; a first analysis unit, configured to determine whether the thermal power unit has a torsional vibration risk according to the first electrical damping and the first reactance drop coefficient, and obtain a first analysis result; A second calculation unit is used to disconnect the high-voltage direct current transmission system from the power system when there is a risk of torsional vibration, and calculate a second electrical damping and a second reactance drop coefficient seen by the neutral point of the thermal power generation unit when the high-voltage direct current transmission system does not exist; a second analysis unit, configured to determine whether the thermal power unit has a torsional vibration risk according to the second electrical damping and the second reactance drop coefficient, and obtain a second analysis result; An evaluation unit is used to compare the first analysis result with the second analysis result, match the comparison result with a preset condition, and obtain an evaluation result of the subsynchronous torsional vibration interaction between thermal power and direct current.

9. A device for evaluating the interaction between thermal power and DC subsynchronous torsional vibration, characterized in that: The device comprises a processor and a memory: The memory is used to store program code and transmit the program code to the processor; The processor is used to execute the method for evaluating subsynchronous torsional vibration interaction between thermal power and direct current according to the instructions in the program code as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium is used to store program codes, and the program codes are used to execute the method for evaluating subsynchronous torsional vibration interaction between thermal power and direct current as described in any one of claims 1 to 7.

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