Power transmission line detuning power oscillation suppression method based on detuning frequency measurement

Abstract

The invention discloses a power transmission line detuning power oscillation suppression method based on detuning frequency measurement, and belongs to the field of power oscillation suppression of a power system. The method comprises the following steps: S1, measuring the output frequency of a transmitting-receiving end voltage source type controlled unit of a power transmission line, and respectively calculating the frequency offset and the total frequency tuning amount of the transmitting-receiving end voltage source type controlled unit; s2, calculating a frequency tuning distribution amount according to the frequency offset and the frequency tuning total amount information; s3, monitoring whether the mean value of the power frequency period of the power transmission line meets a set constraint condition or not, if yes, executing S4, and if not, returning to execute S1; and S4, sending the frequency tuning distribution quantity to corresponding voltage source type controlled units at the two ends of the power transmission line to realize local control of the output frequency of the voltage source type controlled units. Therefore, the problem of power oscillation of the power transmission line caused by detuning of the voltage source type controlled unit can be suppressed and eliminated, the blank in the aspect of detuning oscillation suppression research is filled, and safe and stable operation of the voltage source type controlled unit and a power grid is facilitated.

Description

Technical Field

[0001] The present invention belongs to the field of power oscillation suppression in power systems, and particularly relates to a method for suppressing the detuned power oscillation of a transmission line based on detuned frequency measurement. Background Art

[0002] In a new power system, the increase in the number of power electronic devices and new energy grid-connected units makes the power grid weakly synchronous. Due to the advantages of grid-forming (GFM) converters in the grid connection stability of weak power grids, the number of voltage source controlled units (VSCUs) in the power grid is increasing continuously. For example, flexible DC transmission and energy storage systems based on GFM converters with voltage support characteristics at the ports, as well as other similar or equivalent controlled voltage source characteristic power electronic / non-power electronic grid-connected units.

[0003] VSCUs will weaken the phase synchronization ability of the power grid, and may also cause a sharp decline in the local frequency tuning ability of the power grid due to the different output frequency characteristics of VSCUs. Under the dual effects of weak synchronization and weak tuning, the AC power grid is prone to detuning phenomena where the output frequencies of VSCUs at both ends of a local line or multiple VSCUs within a local power grid remain inconsistent for a long time and the relative frequency difference exhibits a non-zero mean characteristic in the steady-state or quasi-steady-state operating conditions. This phenomenon will induce detuned power oscillation problems on AC transmission lines or within AC power grids, accompanied by a severe peak multiplication effect, which is not conducive to the stable operation of the power grid. Therefore, a method for suppressing the detuned power oscillation of a transmission line based on detuned frequency measurement is proposed. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a method for suppressing the detuned power oscillation of a transmission line based on detuned frequency measurement, which solves the problems in the prior art.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A method for suppressing the detuned power oscillation of a transmission line based on detuned frequency measurement includes the following steps:

[0007] S1, measuring the output frequencies of voltage source controlled units at both ends of the transmission line, and respectively calculating the frequency offset and the total frequency tuning amount of the sending and receiving end voltage source controlled units;

[0008] S2, calculating the frequency tuning allocation amount according to the frequency offset and total frequency tuning amount information;

[0009] S3, monitoring whether the power frequency period mean value of the transmission line power meets the set constraint conditions. If it meets, execute S4; if not, return to execute S1;

[0010] S4. Send the frequency tuning allocation amount to the corresponding voltage source type controlled units at both ends of the transmission line to achieve local control of the output frequency of the voltage source type controlled units.

[0011] Further, the calculation formula of the frequency offset is:

[0012] Δf s = f s - f sys

[0013] Δf r = f r - f sys

[0014] In the formula, Δf s is the frequency offset of the sending-end voltage source type controlled unit, f s is the frequency of the sending-end voltage source type controlled unit, Δf r is the frequency offset of the receiving-end voltage source type controlled unit, f r is the frequency of the receiving-end voltage source type controlled unit, f sys is the frequency measurement value of the AC system in the area where the transmission line is located or the set reference frequency value.

[0015] Further, the calculation formula of the total frequency tuning is:

[0016]

[0017] In the formula, f dc is the total frequency tuning, w1 and w2 are the weight coefficients of the frequency difference signal and its mean signal respectively, f ε1 is the detuning frequency setting value, f ε2 is the mean frequency difference signal setting value.

[0018] Further, the calculation formula of the detuning frequency setting value f ε1 is:

[0019]

[0020] In the formula, f d is the detuning frequency, and ε1 is the threshold value of the detuning frequency.

[0021] Further, the calculation formula of the mean frequency difference signal setting value f ε2 is:

[0022]

[0023] In the formula, is the mean frequency difference signal, ε2 is the threshold value of the mean frequency difference signal, t is the time, and T w is for monitoring fd Time period.

[0024] Furthermore, the set constraint conditions are:

[0025] P s (t) ≥ P s-upl or P s (t) ≤ P s-lowl

[0026] P r (t) ≥ P r-upl or P r (t) ≤ P r-lowl

[0027] In the formula, P s (t) is the average sending - end power; P s-upl , P s-lowl are the upper and lower limits of the average sending - end power respectively; P r (t) is the average receiving - end power; P r-upl , P r-lowl are the upper and lower limits of the average receiving - end power respectively.

[0028] A transmission line detuned power oscillation suppression system based on detuned frequency measurement, comprising:

[0029] Frequency offset and tuning total calculation module: Measure the output frequencies of the controlled voltage sources at both ends of the transmission line, and calculate the frequency offsets and the total frequency tuning amounts of the voltage - source - type controlled units at the sending and receiving ends respectively;

[0030] Frequency tuning allocation amount calculation module: Calculate the frequency tuning allocation amount according to the frequency offset and total frequency tuning amount information;

[0031] Judgment module: Monitor whether the power power - frequency period average value of the transmission line meets the set constraint conditions. If it meets, enter the control module; if not, return to the frequency offset and tuning total calculation module;

[0032] And, control module: Send the frequency tuning allocation amount to the corresponding controlled voltage sources at both ends of the transmission line to achieve local control of the output frequencies of the controlled voltage sources.

[0033] A computer storage medium stores a readable program, which can execute the above - mentioned transmission line detuned power oscillation suppression method based on detuned frequency measurement when the program runs.

[0034] An electronic device, comprising: a processor, a memory, a communication interface, and a communication bus. The processor, the memory, and the communication interface complete communication with each other through the communication bus;

[0035] The memory is used to store at least one executable instruction, and the executable instruction causes the processor to perform operations corresponding to the above-mentioned method for suppressing the detuned power oscillation of a transmission line based on detuned frequency measurement.

[0036] A computer program product includes computer instructions, and the computer instructions direct a computing device to perform operations corresponding to the above-mentioned method for suppressing the detuned power oscillation of a transmission line based on detuned frequency measurement.

[0037] Advantages of the present invention:

[0038] The present invention uses a method for suppressing the detuned power oscillation of a transmission line based on detuned frequency measurement to suppress and eliminate the power oscillation problem of the transmission line caused by the detuning of a voltage source type controlled unit, fills the blank in the research on detuned oscillation suppression, and is beneficial to the safe and stable operation of the voltage source type controlled unit and the power grid. Description of the drawings

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0040] Figure 1 is a flowchart of a method for suppressing the detuned power oscillation of a transmission line based on detuned frequency measurement according to the present invention;

[0041] Figure 2 is an equivalent model of a transmission line with detuned controlled voltage sources at both ends according to the present invention;

[0042] Figure 3 is a graph of the mean value of the power frequency period of the single-phase active power at the sending and receiving ends without applying the suppression method;

[0043] Figure 4 is a graph of the mean value of the power frequency period of the single-phase active power at the sending end after applying the suppression method;

[0044] Figure 5 is a graph of the mean value of the power frequency period of the single-phase active power at the receiving end after applying the suppression method;

[0045] Figure 6 is a graph of the frequencies at the sending and receiving ends after applying the suppression method. Detailed implementation manners

[0046] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0047] Embodiment 1

[0048] As Figure 1 shown, a method for suppressing the detuned power oscillation of a transmission line based on detuned frequency measurement includes the following steps:

[0049] S1, measure the output frequencies of the controlled voltage sources at both ends of the transmission line, and calculate the total frequency tuning amount f dc , the frequency offset Δf s of the sending-end voltage source type controlled unit, and the frequency offset Δf r

[0050]

[0051] Δf s = f s - f sys (2)

[0052] Δf r = f r - f sys (3)

[0053] In the formula, w1 and w2 are the weight coefficients of the frequency difference signal and its mean signal respectively; f ε1 is the detuned frequency setting value, which can be calculated from the detuned frequency f d and its threshold value ε1, as shown in formula (4); f ε2 is the average frequency difference signal setting value, which can be calculated from the average frequency difference signal and its threshold value ε2, as shown in formulas (5) and (6); f sys is the frequency measurement value of the AC system in the area where the transmission line is located or the set reference frequency value, which needs to be selected according to the actual control requirements of the system; f s is the frequency of the sending-end voltage source type controlled unit; f r is the frequency of the receiving-end voltage source type controlled unit.

[0054]

[0055]

[0056] In the formula, t is time, and T w is to monitor f dTime period.

[0057] S2. Calculate the frequency tuning allocation based on the frequency offset and the total frequency tuning information.

[0058] The steps for calculating the frequency tuning allocation are as follows:

[0059] S201. When Δf s ≠0, Δf r =0, and f dc ≠0, the frequency tuning allocations f s_in and f r_in of the sending and receiving end VSCUs are

[0060]

[0061] S202. When Δf s =0, Δf r ≠0, and f dc ≠0, the frequency tuning allocations f s_in and f r_in of the sending and receiving end VSCUs are

[0062]

[0063] S203. When Δf s ≠0, Δf r ≠0, and f dc ≠0, the frequency tuning allocations f s_in and f r_in of the sending and receiving end VSCUs are

[0064]

[0065] S204. When Δf s ≠0, Δf r ≠0, and f dc =0, the frequency tuning allocations f s_in and f r_in of the sending and receiving end VSCUs are

[0066]

[0067] S3. Monitor whether the power power frequency period mean value of the transmission line meets the set constraint conditions. If it meets, execute S4; if not, return to execute S1.

[0068] The set constraint conditions are:

[0069] P s (t)≥P s-upl or P s (t)≤P s-lowl (11)

[0070] P r P(t) ≥ P r-upl or P r P(t) ≤ P r-lowl (12)

[0071] Wherein, P s P(t) is the average sending - end power; P s-upl , P s-lowl are the upper and lower limits of the average sending - end power respectively; P r P(t) is the average receiving - end power; P r-upl , P r-lowl are the upper and lower limits of the average receiving - end power respectively.

[0072] S4. Send the frequency tuning allocation amount to the controlled voltage sources corresponding to both ends of the transmission line, so as to achieve the purpose of local control of the output frequency of the voltage - source - type controlled unit.

[0073] Based on a similar inventive concept, an embodiment of the present invention also provides a computer storage medium, storing a readable program, which can execute the above - mentioned method for suppressing the out - of - tune power oscillation of a transmission line based on out - of - tune frequency measurement when the program runs.

[0074] Based on a similar inventive concept, an embodiment of the present invention provides an electronic device, including: a processor, a memory, a communication interface, and a communication bus, and the processor, the memory, and the communication interface complete communication with each other through the communication bus;

[0075] The memory is used to store at least one executable instruction, and the executable instruction enables the processor to execute the operations corresponding to the above - mentioned method for suppressing the out - of - tune power oscillation of a transmission line based on out - of - tune frequency measurement.

[0076] Based on a similar inventive concept, an embodiment of the present invention also provides a computer program product, including computer instructions, and the computer instructions direct a computing device to execute the operations corresponding to the above - mentioned method for suppressing the out - of - tune power oscillation of a transmission line based on out - of - tune frequency measurement.

[0077] Embodiment 2

[0078] In this embodiment, the effect of the method for suppressing the out - of - tune power oscillation of a transmission line based on out - of - tune frequency measurement of the present invention is verified through simulation.

[0079] As Figure 2 shown, taking the equivalent model of a transmission line with out - of - tune controlled voltage sources at both ends as the basic model, selecting the three - phase line - voltage reference value as 500 kV, simulating the VSCU at the sending - end node s of the line s and the VSCU at the receiving - end node r rThe effective values of a certain phase voltage are 1.050 pu and 1.010 pu respectively, and the initial phases are 10.000° and 0.000° respectively.

[0080] Let the detuning frequency threshold values be ε1 = ε2 = 0.001 Hz, and the system frequency reference value f sys = 50.000 Hz. At the same time, based on the above parameters, the active power at the sending and receiving ends under the in-phase condition is calculated as: P s (t)| ωd＝0 = 204.5 MW, P r (t)| ωd＝0 = 201.2 MW, and the upper and lower limits of the sending and receiving end powers are simulated and set as P s-upl = 1.2P s (t)| ωd＝0 、P s-lowl = 0.8P s (t)| ωd＝0 、P r-upl = 1.2P r (t)| ωd＝0 、P r-lowl = 0.8P r (t)| ωd＝0 .

[0081] Simulate a frequency detuning between VSCU s and VSCU r at 3 s, and set f s = 49.99 Hz and f r = 50.01 Hz at this time. At about 3.2 s, it is detected that the average power rate of the receiving-end single phase first crosses the lower limit, and frequency tuning control instructions are sent to VSCU s 、VSCU r respectively;

[0082] Among them, the power frequency period mean curves of the sending-end / receiving-end single-phase active power applying the suppression method of the present invention are respectively as Figure 4 and Figure 5 shown, and the frequency curves of the sending and receiving ends applying the suppression method of the present invention are shown in Figure 6; the power frequency period mean curves of the sending and receiving ends' single-phase active power without applying the suppression method of the present invention are as Figure 3 shown; by comparing the attached Figure 3 without applying the suppression measure, it can be seen that the method of the present invention can suppress the detuning-type power oscillation and ensure the safety of the power grid operation.

[0083] Example 3

[0084] Based on the transmission line detuning power oscillation suppression method based on detuning frequency measurement proposed in Example 1, in this example, a transmission line detuning power oscillation suppression system based on detuning frequency measurement is proposed, including:

[0085] Frequency offset and total tuning amount calculation module: Measure the output frequencies of the controlled voltage sources at both ends of the transmission line, and calculate the frequency offsets and total frequency tuning amounts of the voltage source type controlled units at the sending and receiving ends respectively;

[0086] Frequency tuning allocation amount calculation module: Calculate the frequency tuning allocation amount according to the frequency offset and total frequency tuning amount information;

[0087] Judgment module: Monitor whether the power frequency period average value of the transmission line satisfies the set constraint conditions. If it is satisfied, enter the control module; if not, return to the frequency offset and total tuning amount calculation module;

[0088] And, control module: Send the frequency tuning allocation amount to the corresponding controlled voltage sources at both ends of the transmission line to achieve local control of the output frequencies of the controlled voltage sources.

[0089] The method of the present invention can be implemented in hardware, firmware, or be implemented as software or computer code that can be stored in a recording medium (such as a CDROM, RAM, floppy disk, hard disk, or magneto-optical disk), or be implemented as computer code originally stored in a remote recording medium or a non-transitory machine-readable medium and downloaded through a network and will be stored in a local recording medium, so that the method described herein can be stored in such software processing on a recording medium using a general-purpose computer, a dedicated processor, or programmable or dedicated hardware (such as an ASIC or FPGA). It can be understood that a computer, a processor, a microprocessor controller, or programmable hardware includes a storage component (such as RAM, ROM, flash memory, etc.) that can store or receive software or computer code. When the software or computer code is accessed and executed by the computer, the processor, or the hardware, the method described herein is implemented. In addition, when a general-purpose computer accesses the code for implementing the method shown herein, the execution of the code converts the general-purpose computer into a dedicated computer for executing the method shown herein.

[0090] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art of this industry should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed.

Claims

1. A method for suppressing the detuned power oscillation of a transmission line based on the measurement of the detuned frequency, characterized in that It includes the following steps: S1. Measure the output frequencies of the voltage-source controlled units at both ends of the transmission line, and calculate the frequency deviation amounts and the total frequency tuning amounts of the voltage-source controlled units at the sending and receiving ends respectively; S2. Calculate the frequency tuning allocation amounts according to the frequency deviation amounts and the total frequency tuning amount information; S3. Monitor whether the mean value of the power frequency period of the transmission line satisfies the set constraint conditions. If it is satisfied, execute S4; if not, return to execute S1; S4. Send the frequency tuning allocation amounts to the corresponding voltage-source controlled units at both ends of the transmission line to achieve the local control of the output frequencies of the voltage-source controlled units.

2. A method for suppressing the detuned power oscillation of a transmission line based on detuned frequency measurement according to claim 1, characterized in that, The calculation formula for the frequency deviation amount is: Δf s = f s - f sys Δf r = f r - f sys where, Δf s is the frequency offset of the sending-end voltage-source type controlled unit, f s is the frequency of the sending-end voltage-source type controlled unit, Δf r is the frequency offset of the receiving-end voltage-source type controlled unit, f r is the frequency of the receiving-end voltage-source type controlled unit, and f sys is the measured value of the frequency of the AC system in the area where the transmission line is located or the set reference frequency value.

3. A method for suppressing the detuned power oscillation of a transmission line based on detuned frequency measurement according to claim 1, characterized in that, The calculation formula for the total frequency tuning amount is: where f dc is the total frequency tuning amount, w1 and w2 are the weight coefficients of the frequency difference signal and its mean signal respectively, f ε1 is the set value of the detuning frequency, and f ε2 is the set value of the average frequency difference signal.

4. A method for suppressing the detuned power oscillation of a transmission line based on detuned frequency measurement according to claim 3, characterized in that, The set value f of the detuning frequency ε1 is calculated by the following formula: where f d is the detuning frequency, and ε1 is the threshold value of the detuning frequency.

5. A method for suppressing the detuned power oscillation of a transmission line based on the measurement of the detuned frequency according to claim 3, characterized in that, The set value f of the average frequency difference signal ε2 is calculated by the following formula: Wherein, is the average frequency difference signal, ε2 is the threshold value of the average frequency difference signal, t is time, and T w is the time period for monitoring f d .

6. A method for suppressing the detuned power oscillation of a transmission line based on detuned frequency measurement according to claim 1, characterized in that The set constraint conditions are: P s P(t) ≥ P s-upl or P s P(t) ≤ P s-lowl P r P(t) ≥ P r-upl or P r P(t) ≤ P r-lowl Wherein, P s (t) is the mean sending - end power; P s-upl and P s-lowl are the upper and lower limits of the mean sending - end power respectively; P r (t) is the mean receiving - end power; P r-upl and P r-lowl are the upper and lower limits of the mean receiving - end power respectively.

7. Transmission line detuned power oscillation suppression system based on detuned frequency measurement, characterized in that It includes: Frequency deviation amount and total tuning amount calculation module: Measure the output frequencies of the controlled voltage sources at both ends of the transmission line, and calculate the frequency deviation amounts and the total frequency tuning amounts of the voltage-source controlled units at the sending and receiving ends respectively; Frequency tuning allocation amount calculation module: Calculate the frequency tuning allocation amounts according to the frequency deviation amounts and the total frequency tuning amount information; Judgment module: Monitor whether the mean value of the power frequency period of the transmission line satisfies the set constraint conditions. If it is satisfied, enter the control module; if not, return to the frequency deviation amount and total tuning amount calculation module; And a control module: Send the frequency tuning allocation amounts to the corresponding controlled voltage sources at both ends of the transmission line to achieve the local control of the output frequencies of the controlled voltage sources.

8. A computer storage medium stores a readable program, characterized in that, When the program runs, it can execute a method for suppressing the detuned power oscillation of a transmission line based on detuned frequency measurement according to any one of claims 1-6.

9. An electronic device, characterized in that, It includes: A processor, a memory, a communication interface and a communication bus. The processor, the memory and the communication interface complete the communication with each other through the communication bus; The memory is used to store at least one executable instruction, and the executable instruction enables the processor to execute the operations corresponding to a method for suppressing the detuned power oscillation of a transmission line based on detuned frequency measurement according to any one of claims 1-6.

10. A computer program product, comprising computer instructions, characterized in that, The computer instruction instructs the computing device to execute the operations corresponding to a method for suppressing the detuned power oscillation of a transmission line based on detuned frequency measurement according to any one of claims 1-6.

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