CN111082448B - Double-tuned filter control method, double-tuned filter and direct-current power transmission system - Google Patents
Double-tuned filter control method, double-tuned filter and direct-current power transmission system Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
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Abstract
The invention provides a double-tuned filter control method, a double-tuned filter and a direct-current power transmission system. The method comprises the following steps: acquiring direct-current voltage and direct current at a direct-current polar outlet of a converter station of a direct-current transmission system; judging whether the converter station generates series resonance or not based on the direct current voltage and the direct current; and when the converter station generates series resonance, cutting off the additional capacitance of the double-tuned filter to eliminate the series resonance, wherein the double-tuned filter is set to eliminate the characteristic harmonic of the converter station. By implementing the invention, when series resonance occurs, the impedance frequency characteristic of the double-tuned filter is changed by cutting off the additional capacitor of the double-tuned filter, and then the impedance frequency characteristic of the multi-terminal direct-current power transmission system is adjusted, so that the series resonance is rapidly and accurately eliminated.
Description
Technical Field
The invention relates to the technical field of high-voltage direct-current transmission of a power system, in particular to a double-tuned filter control method, a double-tuned filter and a direct-current transmission system.
Background
The traditional two-end high-voltage direct-current transmission system is particularly suitable for long-distance and large-capacity transmission and plays an extremely important role in the strategy of 'west-east transmission and national networking' in China. However, the conventional two-terminal hvdc transmission system can only realize point-to-point dc power transmission. With economic development and construction of power grids, the power grids are inevitably required to realize multi-power supply and multi-drop power receiving, so that a multi-terminal direct current (MTDC) power transmission system is developed on the basis of a two-terminal high-voltage direct current power transmission system, and the power grids have good development prospects. Each converter station forming a multi-terminal direct-current transmission system, wherein the core electrical equipment, namely the converters, are harmonic voltage sources, and 12k (k is 1,2,3, … …) times of characteristic harmonics are injected into the multi-terminal direct-current transmission system. In order to reduce the harmonic level of the HVDC transmission line, a group of double-tuned filters is connected in parallel at the DC pole line outlet of each converter station. Equivalent impedances of the multi-terminal direct current transmission system under different frequencies are different. With the change of the operation mode of the multi-terminal direct current transmission system, a plurality of natural series resonance frequencies exist in the system. Once the low-frequency background harmonic waves of the alternating current system are modulated to the direct current side through the converter, if the frequency (mainly third harmonic waves) of the low-frequency non-specific harmonic wave voltage is close to or even equal to the inherent series resonance frequency of the multi-terminal direct current transmission system, the multi-terminal direct current transmission system generates series resonance, so that the direct current harmonic wave current is amplified by several times or even dozens of times, the safety of the converter, the direct current transmission line and the double-tuned filter is endangered, the service life of the multi-terminal direct current transmission system is shortened, the multi-terminal direct current transmission system can be difficult to operate or even locked, and the stable operation of the alternating current and direct current system is seriously influenced.
The double-tuned filter of the existing two-terminal direct-current transmission system is designed according to the characteristic harmonic (for example, 12 k-12, 24, … th harmonic) of the suppression converter, and does not have the function of eliminating the series resonance of the direct-current transmission system.
Disclosure of Invention
Therefore, the technical problem to be solved by the present invention is to solve the problem in the prior art that series resonance cannot be eliminated, thereby providing a double-tuned filter control method, a double-tuned filter, and a dc power transmission system.
Therefore, the embodiment of the invention provides the following technical scheme:
in a first aspect, an embodiment of the present invention provides a method for controlling a double-tuned filter, including: acquiring direct-current voltage and direct current at a direct-current polar outlet of a converter station of a direct-current transmission system; judging whether the converter station generates series resonance or not based on the direct current voltage and the direct current; and when the converter station generates series resonance, cutting off the additional capacitance of the double-tuned filter to eliminate the series resonance, wherein the double-tuned filter is set to eliminate the characteristic harmonic of the converter station.
In an embodiment, the determining whether the converter station generates the series resonance based on the dc voltage and the dc current includes: calculating a harmonic impedance of the converter station based on the direct voltage and the direct current; judging whether the harmonic impedance is smaller than a preset threshold value or not; and when the harmonic impedance is smaller than the preset threshold value, determining that the converter station generates series resonance.
In an embodiment, said calculating a harmonic impedance of said converter station based on said dc voltage and said dc current comprises: performing fast Fourier transform on the direct current voltage to obtain a harmonic voltage amplitude corresponding to the direct current voltage; performing fast Fourier transform on the direct current to obtain a harmonic current amplitude corresponding to the direct current; and calculating the harmonic impedance by using the harmonic voltage amplitude and the harmonic current amplitude.
In an embodiment, the calculating the harmonic impedance by using the harmonic voltage amplitude and the harmonic current amplitude includes: calculating the harmonic impedance by the following calculation formula:
wherein Z isdihIs the h-th harmonic impedance at the dc pole line outlet of the i-th converter station;
being a vector of the h-th harmonic voltage amplitude at the dc pole line outlet of the i-th converter station,
is a vector of the h-th harmonic current amplitude at the dc pole line outlet of the i-th converter station.
In one embodiment, the cutting off the additional capacitance of the double tuned filter comprises: sending a turn-on pulse to a first switch for controlling a first additional capacitance path of the double tuned filter to short the first additional capacitance; sending a conduction pulse to a second switch for controlling a second additional capacitance path of the double tuned filter to short the second additional capacitance.
In one embodiment, after the additional capacitance of the double tuned filter is cut off, the method further comprises: detecting whether the converter station still generates series resonance; and when the converter station does not generate the series resonance, restoring the additional capacitance of the double-tuned filter to an initial circuit state.
In one embodiment, the restoring the additional capacitance of the double tuned filter to an initial circuit state comprises: stopping sending a conduction pulse to a first switch for controlling a first additional capacitance path of the double tuned filter so that the first additional capacitance is normally connected into the circuit; stopping sending a conduction pulse to a second switch controlling a second additional capacitance path of the double tuned filter such that the second additional capacitance is normally switched into circuit.
In a second aspect, an embodiment of the present invention provides a double-tuned filter, including: a first capacitor; a first additional capacitor connected in series with the first capacitor; the first switch circuit is connected with the first additional capacitor in parallel and used for controlling the first additional capacitor to be short-circuited when the first switch circuit is conducted; a second capacitor; a second additional capacitor connected in series with the second capacitor; and the second switching circuit is connected with the second additional capacitor in parallel and used for controlling the second additional capacitor to be short-circuited when the second additional capacitor is conducted.
In an embodiment, the first switch circuit comprises a first switch, the second switch circuit comprises a second switch, and the first switch and the second switch are both bidirectional contactless switches.
In a third aspect, an embodiment of the present invention provides a direct current power transmission system, including: a converter station; the double-tuned filter provided in the second aspect of the embodiment of the present invention is configured to eliminate characteristic harmonics of the converter station; and the controller is connected with the double-tuned filter and used for controlling the double-tuned filter to eliminate the series resonance when the converter station generates the series resonance.
The technical scheme of the invention has the following advantages:
according to the double-tuned filter control method, the double-tuned filter and the direct-current power transmission system, the thyristor-based bidirectional contactless switch is adopted, when series resonance occurs, the additional capacitance of the double-tuned filter is quickly and accurately cut off, the impedance frequency characteristic of the double-tuned filter is changed, the impedance frequency characteristic of the multi-terminal direct-current power transmission system is further adjusted, and the series resonance is eliminated. Meanwhile, the design function of the characteristic harmonic of the double-tuned filter is hardly influenced. After the series resonance is eliminated, the normal operation of the double tuned filter is quickly resumed.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
Fig. 1 is a flowchart showing a specific example of a double-tuned filter control method according to an embodiment of the present invention;
FIG. 2 is a topological structure diagram of a specific example of a double tuned filter in an embodiment of the present invention;
FIG. 3 is a flow chart of another specific example of a double tuned filter control method in an embodiment of the present invention;
fig. 4 is a frequency characteristic curve of harmonic impedance of a converter station of the multi-terminal dc transmission system according to an embodiment of the present invention;
FIG. 5 is a flow chart of another specific example of a double tuned filter control method in an embodiment of the present invention;
fig. 6 is a flowchart showing another specific example of a double-tuned filter control method in the embodiment of the present invention;
fig. 7 is a schematic diagram of a parallel three-terminal dc power transmission system according to an embodiment of the present invention;
fig. 8 is an impedance frequency characteristic diagram of a double tuned filter according to an embodiment of the present invention.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the description of the present invention, it should be noted that, in addition, the terms "first", "second", and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; the two elements may be directly connected or indirectly connected through an intermediate medium, or may be communicated with each other inside the two elements, or may be wirelessly connected or wired connected. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
In addition, the technical features involved in the different embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
Example 1
The embodiment of the invention provides a control method of a double-tuned filter, as shown in fig. 1, comprising the following steps:
step S1: and acquiring direct-current voltage and direct current at a direct-current polar line outlet of a converter station of the direct-current transmission system. In an embodiment of the invention, there are a plurality of converter stations in a multi-terminal dc transmission system, and the dc voltage u is measured at the dc pole line outlet of each converter stationdiAnd a direct current idiThe subscript i refers to the number of the converter stations, i is 1,2, … N, and N is the total number of the converter stations forming the multi-terminal direct current transmission system.
Step S2: and judging whether the converter station generates series resonance or not based on the direct current voltage and the direct current. In the embodiment of the invention, the voltage value and the current value of the direct current polar harmonic wave are respectively subjected to fast Fourier transform to obtain the voltage amplitude U of each subharmonic wavedihSum harmonic current amplitude IdihAnd further obtaining the vector of the harmonic voltage amplitude by vector operation
And vector of harmonic current amplitude
The subscript h represents the h-th harmonic order. Vector according to harmonic voltage amplitude
And vector of harmonic current amplitude
And calculating the harmonic impedance, wherein the calculation formula of the harmonic impedance is as follows:
wherein Z isdihIs the h-th harmonic impedance at the dc pole line outlet of the i-th converter station;
being a vector of the h-th harmonic voltage amplitude at the dc pole line outlet of the i-th converter station,
is a vector of the h-th harmonic current amplitude at the dc pole line outlet of the i-th converter station. According to harmonic impedance ZdihThe mode value of (a) determines whether a series resonance of the converter station occurs.
Step S3: and when the converter station generates series resonance, cutting off the additional capacitance of the double-tuned filter to eliminate the series resonance, wherein the double-tuned filter is set to eliminate the characteristic harmonic of the converter station. In the embodiment of the invention, as shown in fig. 2, for the converter station in which the series resonance occurs, the capacitor C is added11And C22Parallel switch S of1And S2Applying a trigger-on pulse to switch S1And S2Equivalent to a short circuit, thereby shorting the additional capacitor C11And C22To realize the harmonic elimination control of the parallel double-tuned filter of the converter station.
According to the control method of the double-tuned filter, when series resonance occurs, the impedance frequency characteristic of the double-tuned filter is changed by cutting off the additional capacitor of the double-tuned filter, and then the impedance frequency characteristic of a multi-terminal direct-current power transmission system is adjusted, so that the series resonance is quickly and accurately eliminated.
In an embodiment, the determining whether the converter station has the series resonance based on the dc voltage and the dc current, as shown in fig. 3, includes the following steps:
step S21: the harmonic impedance of the converter station is calculated on the basis of the direct voltage and the direct current. In the embodiment of the invention, the voltage value and the current value of the direct current polar harmonic wave are respectively subjected to fast Fourier transform to obtain the voltage amplitude U of each subharmonic wavedihSum harmonic current amplitude IdihAnd further obtaining the vector of the harmonic voltage amplitude by vector operation
And vector of harmonic current amplitude
The subscript h represents the h-th harmonic order. Vector according to harmonic voltage amplitude
And vector of harmonic current amplitude
And calculating the harmonic impedance, wherein the calculation formula of the harmonic impedance is as follows:
wherein Z isdihIs the h-th harmonic impedance at the dc pole line outlet of the i-th converter station;
being a vector of the h-th harmonic voltage amplitude at the dc pole line outlet of the i-th converter station,
is a vector of the h-th harmonic current amplitude at the dc pole line outlet of the i-th converter station.
Step S22: and judging whether the harmonic impedance is smaller than a preset threshold value. In the embodiment of the present invention, the preset threshold is 300 Ω.
Step S23: and when the harmonic impedance is smaller than a preset threshold value, determining that the converter station generates series resonance. In the present example, if ZdihIf the mode value is less than 300 omega, judging that the converter station generates series resonance aiming at the h-th harmonic; otherwise, it is determined that no series resonance occurs. When it is determined that the series resonance for the h-th harmonic occurs, it is first determined which converter station(s) has/have occurred, i.e. it is determined that Z with a mode value of less than 300 ΩdihIs what is i in (1). Determining whether a series resonance occurs in a multi-terminal DC transmission system is determined only by commutationThe mode value of the harmonic impedance of the station is determined by the ratio of the mode values measured by the harmonic voltage and the harmonic current of the direct current polar line, so that the amplitude values of the harmonic voltage and the harmonic current can be measured without paying attention to the phase. As shown in fig. 4, minima of less than 300 Ω occur in the low frequency range within 180Hz, and therefore, if the harmonic voltage source generated by the inverter contains a harmonic of 150Hz, a series resonance of 3 rd order harmonics will occur.
In an embodiment, the harmonic impedance of the converter station is calculated based on the dc voltage and the dc current, as shown in fig. 5, comprising the steps of:
step S211: and carrying out fast Fourier transform on the direct current voltage to obtain a harmonic voltage amplitude corresponding to the direct current voltage.
Step S212: and carrying out fast Fourier transform on the direct current to obtain a harmonic current amplitude corresponding to the direct current.
Step S213: and calculating to obtain harmonic impedance by using the harmonic voltage amplitude and the harmonic current amplitude.
In the embodiment of the present invention, specific contents refer to the related description of step S21 in the above embodiment.
In one embodiment, the removing the additional capacitance of the double tuned filter comprises: to a first additional capacitance C for controlling the double-tuned filter11First switch of path S1Sending a conduction pulse to make the first additional capacitor C11Short-circuit connection; to a second additional capacitance C for controlling the double-tuned filter22Second switch S of the path2Sending a conduction pulse to make the second additional capacitor C22And (6) short-circuiting.
In the embodiment of the invention, the additional capacitor C is simultaneously added11And C22Parallel switch S of1And S2Applying a trigger-on pulse to switch S1And S2Equivalent to a short circuit, thereby shorting the additional capacitor C11And C22. At this time, the high-voltage capacitance of the double-tuned filter is changed from C in normal operation1Series C11Is changed into C1Low voltage capacitor from C in normal operation2Series C22Is changed into C2. Wherein，C1、C11And C2、C22The values of (A) are as follows:
from the above, the high-voltage capacitor and the low-voltage capacitor of the double-tuned filter designed according to the dc harmonic standard of the converter station are respectively
In one embodiment, after cutting off the additional capacitance of the double tuned filter, as shown in fig. 6, the following steps are included:
step S4: it is detected whether the converter station still generates a series resonance. In the embodiment of the present invention, specific contents refer to the related description of step S2 in the above embodiment.
Step S5: when the converter station is not producing series resonance, the additional capacitance of the double tuned filter is restored to the initial circuit state. In the embodiment of the present invention, when it is determined that the series resonance is eliminated, that is, ZdihAfter no more than 300 omega, the additional capacitance C is simultaneously added11And C22Parallel switch S of1And S2Stopping sending trigger conducting pulse to make switch S1And S2Equivalent to an open circuit, thereby providing an additional capacitance C11And C22And the series connection is restored to the double-tuned filter circuit again, and the normal operation of the double-tuned filter is restored.
Example 2
An embodiment of the present invention provides a double-tuned filter, as shown in fig. 2, including: a first capacitor C1(ii) a First additional capacitance C11And a first capacitor C1Are connected in series; a first switch circuit, and a first additional capacitor C11In parallel for controlling the first additional capacitance C when switched on11Short-circuit connection; second capacitor C2(ii) a Second additional capacitance C22And a second capacitor C2Are connected in series; a second switch circuit, and a second additional capacitor C22In parallel for controlling the second additional capacitance C when switched on22And (6) short-circuiting. In the embodiment of the present invention, as shown in FIG. 2, a multi-port cancellation scheme is providedA topology structure diagram of a double-tuned filter of series resonance of a direct current transmission system, wherein a capacitor C1Capacitor C2Inductor L1An additional capacitor C11And an additional capacitance C22Are connected in series; inductor L2And a capacitor C2An additional capacitor C22Are connected in parallel; additional capacitance C11And switch S1Are connected in parallel; additional capacitance C22And switch S2Are connected in parallel.
In one embodiment, the first switch circuit comprises a first switch, the second switch circuit comprises a second switch, and the first switch and the second switch are both bidirectional contactless switches. In the embodiment of the present invention, the switch S1Switch S2A thyristor-based bidirectional contactless switch is used.
Example 3
An embodiment of the present invention provides a dc power transmission system, including: a converter station; the double-tuned filter provided by the embodiment 2 of the invention is used for eliminating the characteristic harmonic waves of the converter station; and the controller is connected with the double-tuned filter and used for controlling the double-tuned filter to eliminate the series resonance when the converter station generates the series resonance. In the embodiment of the invention, the multi-terminal direct-current transmission system is provided with a plurality of converter stations, and a group of double-tuned filters is connected in parallel at a direct-current polar line outlet of each converter station.
Example 4
The embodiment of the invention specifically takes a typical ultrahigh voltage direct current transmission project in China as an example for explanation, and constructs a parallel three-terminal direct current transmission system as shown in figure 7, and the rated parameters of the system are shown in the following table. Taking the parallel three-terminal direct-current power transmission system as an example, a simulation model of the parallel three-terminal direct-current power transmission system is built in PSCAD/EMTDC software, and the effect of the double-tuned filter provided by the application is verified.
According to the parallel three-end direct-current transmission system, the three converter stations all adopt the same direct-current filter and adopt a group of 12/24 pairs of the current typical extra-high voltage direct-current transmission systemThe tuning filter has parameters that the high-voltage capacitor and the low-voltage capacitor are respectively 1 mu F and 3.047 mu F; the high-low voltage inductances are 0.0174H and 0.0157H respectively. According to the method provided in example 1 of the present invention, C is calculated1＝1μF，C11＝2C1＝2μF，C2＝3.047μF，C22＝2C2＝6.094F。
As shown in fig. 8, the impedance modulus values of the double-tuned filter in two states are shown in the following table:
| frequency/Hz | Normal operation impedance modulus/omega | Adding additional capacitance impedance modulus/ |
| 400 | 69.45499233 | 28.8242546 |
| 450 | 49.71152423 | 11.59867081 |
| 475 | 40.58393233 | 2.952171586 |
| 500 | 31.7711427 | 6.017056174 |
| 525 | 23.14921154 | 15.61591528 |
| 550 | 14.59435979 | 26.28653959 |
| 575 | 5.974463779 | 38.72744163 |
| 600 | 2.861528823 | 54.15520236 |
| 625 | 12.09834049 | 74.94958697 |
| 650 | 21.97683901 | 106.5580157 |
| 900 | 1294.998879 | 24.54359739 |
| 950 | 203.8049602 | 7.788506706 |
| 975 | 136.8864616 | 1.17546944 |
| 1000 | 99.02626579 | 4.678708802 |
| 1050 | 56.09786327 | 14.78643881 |
| 1100 | 30.97924949 | 23.43933366 |
| 1150 | 13.48858515 | 31.121128 |
| 1100 | 0.000283415 | 38.1157714 |
| 1250 | 11.10582155 | 44.6020482 |
The impedance modulus values of the parallel three-terminal direct-current transmission system near the frequency of 150Hz are shown in the following table:
| frequency/Hz | Normal operation impedance modulus/omega | Adding additional capacitance impedance modulus/omega |
| 130 | 461.08376 | 79.28946694 |
| 135 | 202.7095009 | 110.0517559 |
| 140 | 121.6054417 | 173.728495 |
| 145 | 304.2834618 | 221.373258 |
| 150 | 74.2518643 | 263.668341 |
| 155 | 166.6925437 | 302.1585675 |
| 160 | 228.4374149 | 330.5203788 |
| 165 | 281.6457507 | 341.5672596 |
| 170 | 332.2207633 | 363.8449279 |
As shown in fig. 8, when a minimum value having an impedance value smaller than 300 Ω is defined as the series resonance impedance, series resonance occurs only in the range of f 1 to 250 Hz. And because fundamental frequency components are introduced into the direct current line due to faults such as commutation failure and the like, the negative sequence harmonic of the alternating current system can generate larger 1-3 harmonics on the direct current line, and therefore the impedance frequency characteristic of the MTDC system is researched in the frequency range of 50-150 Hz. Specifically, after the additional capacitor is added, the filter characteristic of the double tuned filter is slightly shifted to the right, but the impedance at the frequencies of 12 and 24 is still very small, and the effect of filtering the harmonic waves at the frequencies of 12 and 24 is not greatly influenced.
According to the double-tuned filter control method, the double-tuned filter and the direct-current power transmission system, the thyristor-based bidirectional contactless switch is adopted, when series resonance occurs, the additional capacitance of the double-tuned filter is quickly and accurately cut off, the impedance frequency characteristic of the double-tuned filter is changed, the impedance frequency characteristic of the multi-terminal direct-current power transmission system is further adjusted, and the series resonance is eliminated. Meanwhile, the design function of the characteristic harmonic of the double-tuned filter is hardly influenced. After the series resonance is eliminated, the normal operation of the double tuned filter is quickly resumed.
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.
Claims (9)
1. A method for controlling a double tuned filter, comprising:
acquiring direct-current voltage and direct current at a direct-current polar outlet of a converter station of a direct-current transmission system;
judging whether the converter station generates series resonance or not based on the direct current voltage and the direct current;
when the converter station generates series resonance, cutting off an additional capacitor of a double-tuned filter to eliminate the series resonance, wherein the double-tuned filter is set to eliminate the characteristic harmonic of the converter station;
the additional capacitance of the double tuned filter is cut off, and the method comprises the following steps:
sending a turn-on pulse to a first switch for controlling a first additional capacitance path of the double tuned filter to short the first additional capacitance;
sending a turn-on pulse to a second switch for controlling a second additional capacitance path of the double tuned filter to short the second additional capacitance
The double tuned filter comprises:
a first capacitor;
a first additional capacitor connected in series with the first capacitor;
the first switch circuit is connected with the first additional capacitor in parallel and used for controlling the first additional capacitor to be short-circuited when the first switch circuit is conducted;
a second capacitor;
a second additional capacitor connected in series with the second capacitor;
and the second switching circuit is connected with the second additional capacitor in parallel and used for controlling the second additional capacitor to be short-circuited when the second additional capacitor is conducted.
2. The double-tuned filter control method of claim 1, wherein said determining whether a series resonance of the converter station occurs based on the dc voltage and the dc current comprises:
calculating a harmonic impedance of the converter station based on the direct voltage and the direct current;
judging whether the harmonic impedance is smaller than a preset threshold value or not;
and when the harmonic impedance is smaller than the preset threshold value, determining that the converter station generates series resonance.
3. The double-tuned filter control method according to claim 2, wherein said calculating harmonic impedances of said converter stations based on said dc voltages and said dc currents comprises:
performing fast Fourier transform on the direct current voltage to obtain a harmonic voltage amplitude corresponding to the direct current voltage;
performing fast Fourier transform on the direct current to obtain a harmonic current amplitude corresponding to the direct current;
and calculating the harmonic impedance by using the harmonic voltage amplitude and the harmonic current amplitude.
4. The method for controlling a double-tuned filter according to claim 3, wherein there are a plurality of said converter stations, and said calculating said harmonic impedance using said harmonic voltage amplitude and said harmonic current amplitude comprises:
calculating the harmonic impedance by the following calculation formula:
wherein Z isdihIs the h-th harmonic impedance at the dc pole line outlet of the i-th converter station;
being a vector of the h-th harmonic voltage amplitude at the dc pole line outlet of the i-th converter station,
is a vector of the h-th harmonic current amplitude at the dc pole line outlet of the i-th converter station.
5. The double-tuned filter control method of claim 1, further comprising, after removing the additional capacitance of the double-tuned filter:
detecting whether the converter station still generates series resonance;
and when the converter station does not generate the series resonance, restoring the additional capacitance of the double-tuned filter to an initial circuit state.
6. The double-tuned filter control method of claim 5, wherein said restoring the additional capacitance of said double-tuned filter to an initial circuit state comprises:
stopping sending a conduction pulse to a first switch for controlling a first additional capacitance path of the double tuned filter so that the first additional capacitance is normally connected into the circuit;
and stopping sending the conducting pulse to a second switch used for controlling a second additional capacitor path of the double-tuned filter, so that the second additional capacitor is normally connected into the circuit.
7. A double tuned filter, characterized in that, using the double tuned filter control method according to any of claims 1-6, the double tuned filter comprises:
a first capacitor;
a first additional capacitor connected in series with the first capacitor;
the first switch circuit is connected with the first additional capacitor in parallel and used for controlling the first additional capacitor to be short-circuited when the first switch circuit is conducted;
a second capacitor;
a second additional capacitor connected in series with the second capacitor;
and the second switching circuit is connected with the second additional capacitor in parallel and used for controlling the second additional capacitor to be short-circuited when the second additional capacitor is conducted.
8. The double-tuned filter of claim 7, wherein said first switching circuit comprises a first switch and said second switching circuit comprises a second switch, and wherein said first switch and said second switch are both bidirectional contactless switches.
9. A direct current power transmission system, comprising:
a converter station;
the double tuned filter of claim 7 or 8, for eliminating said converter station characteristic harmonics;
and the controller is connected with the double-tuned filter and used for controlling the double-tuned filter to eliminate the series resonance when the converter station generates the series resonance.
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| CN202134913U (en) * | 2011-06-30 | 2012-02-01 | 中国西电电气股份有限公司 | Equivalent circuit used for detecting DC side low-order harmonic of high voltage DC power transmission system |
| CN104604072A (en) * | 2012-06-01 | 2015-05-06 | Abb技术有限公司 | A filter apparatus, a method for filtering harmonics in an electrical power transmission or distribution system, and such a system |
| CN110380431A (en) * | 2019-07-25 | 2019-10-25 | 上海良肯电气有限公司 | A kind of multifunction power tuning filtering system and method |
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| US7884886B2 (en) * | 2003-10-27 | 2011-02-08 | Zoran Corporation | Integrated channel filter and method of operation |
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| CN202134913U (en) * | 2011-06-30 | 2012-02-01 | 中国西电电气股份有限公司 | Equivalent circuit used for detecting DC side low-order harmonic of high voltage DC power transmission system |
| CN104604072A (en) * | 2012-06-01 | 2015-05-06 | Abb技术有限公司 | A filter apparatus, a method for filtering harmonics in an electrical power transmission or distribution system, and such a system |
| CN110380431A (en) * | 2019-07-25 | 2019-10-25 | 上海良肯电气有限公司 | A kind of multifunction power tuning filtering system and method |
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