CN108667065B - Circuit for limiting double-twelve-pulse midpoint resonance of direct-current power transmission system - Google Patents
Circuit for limiting double-twelve-pulse midpoint resonance of direct-current power transmission system Download PDFInfo
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- CN108667065B CN108667065B CN201810843210.5A CN201810843210A CN108667065B CN 108667065 B CN108667065 B CN 108667065B CN 201810843210 A CN201810843210 A CN 201810843210A CN 108667065 B CN108667065 B CN 108667065B
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- 230000005540 biological transmission Effects 0.000 title claims abstract description 20
- 230000000670 limiting effect Effects 0.000 title claims abstract description 14
- 239000003990 capacitor Substances 0.000 claims abstract description 118
- 238000004804 winding Methods 0.000 claims 1
- 230000003321 amplification Effects 0.000 abstract description 6
- 238000003199 nucleic acid amplification method Methods 0.000 abstract description 6
- 230000002401 inhibitory effect Effects 0.000 abstract description 2
- 238000000034 method Methods 0.000 description 4
- 238000010586 diagram Methods 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 238000010304 firing Methods 0.000 description 2
- 238000009499 grossing Methods 0.000 description 2
- 238000009413 insulation Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
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- 230000002829 reductive effect Effects 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000005284 excitation Effects 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
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- 230000000452 restraining effect Effects 0.000 description 1
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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
- H02J3/00—Circuit arrangements for AC mains or AC distribution networks
- H02J3/36—Arrangements for transfer of electric power between AC networks via a high-tension DC link
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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
- H02J3/00—Circuit arrangements for AC mains or AC distribution networks
- H02J3/36—Arrangements for transfer of electric power between AC networks via a high-tension DC link
- H02J2003/365—Reducing harmonics or oscillations in HVDC
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]
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Abstract
The invention discloses a circuit for limiting double-twelve-pulse midpoint resonance of a direct-current power transmission system, which comprises an upper twelve-pulse valve bank and a lower twelve-pulse valve bank which have the same structure, the upper twelve pulsating valve bank and the lower twelve pulsating valve bank are connected in series, the upper twelve pulsating valve bank and the lower twelve pulsating valve bank are symmetrical in a circuit structure, two ends of the upper and lower twelve-pulse valve groups are connected in parallel with a direct current filter, the direct current filter comprises a first capacitor group, a second capacitor and a third capacitor, the first capacitor bank, the second capacitor and the third capacitor are connected in series, the first capacitor bank comprises an upper first capacitor and a lower first capacitor, the upper first capacitor is connected with the lower first capacitor in series, and the middle points of the upper twelve-pulse valve bank and the lower twelve-pulse valve bank are connected between the upper first capacitor and the lower first capacitor, so that the aim of inhibiting high-frequency resonance amplification is fulfilled.
Description
Technical Field
The invention relates to the field of high-voltage direct-current transmission, in particular to a circuit for limiting double-twelve-pulse midpoint resonance of a direct-current transmission system.
Background
At present, a double-twelve-pulse structure is mostly adopted in a current source type extra-high voltage direct current transmission system put into operation in the world as shown in figure 1. The current source type direct current transmission system generates a large amount of harmonic waves in the current conversion process of the current converter, and the twelve-pulse structure generates 12-frequency-multiplication sub-characteristic harmonic waves on the direct current side. In general, the upper and lower twelve pulses of the double twenty-pulse structure are identical, so that the generated harmonic waves are superposed by the upper and lower twelve pulses. According to the circuit symmetry principle, the voltage at the midpoint of the twenty-two pulses is zero.
However, in a practical system, the upper twelve pulses and the lower twelve pulses are not completely symmetrical due to triggering angle deviation and parameter deviation of a transformer or a valve, and 24-th harmonic waves are generated at the middle point. Especially considering the stray capacitance of the converter side port to ground, which is typically 10-20nF, the capacitance will resonate with the dc side smoothing reactance about 24 times, thereby amplifying the 24 th harmonic voltage at the midpoint.
The 24-order resonance amplification is most severe especially in the following two cases:
1) the deviation of the trigger angle of the upper twelve-pulse valve group and the lower twelve-pulse valve group is large, the situation often occurs that different tap control modes are adopted in the upper twelve-pulse valve group and the lower twelve-pulse valve group, so that the tap difference is large, the deviation of the trigger angle is large, the 24-order harmonic voltage source at the middle point of excitation is increased, and then the resonance amplification is carried out through the stray capacitor.
2) The upper and lower twelve pulses are accessed in a layered mode and are respectively accessed into different alternating current systems, and phase angle difference exists between the two alternating current systems, so that the upper and lower twelve pulses are asymmetric, a 24-order harmonic voltage source at the midpoint is excited, and resonance amplification is performed through stray capacitors.
In practical engineering and theoretical simulations, the 24 th harmonic voltage source at the mid-point of the twenty-two pulses can reach hundreds of kilovolts at the maximum, which will raise the voltage level at the mid-point and even cause equipment damage.
In the launched direct current engineering, the deviation of the upper and lower twelve pulse firing angles is usually restrained, but for a layered access system, a better method for restraining the resonance is not available. Once the stray capacitance of the equipment and the direct current side smoothing reactance form a resonance relation, the safe and stable operation of the direct current transmission system is seriously threatened.
Disclosure of Invention
The embodiment of the invention aims to provide a circuit for limiting the double-twelve-pulse midpoint resonance of a direct-current power transmission system, and the aim of inhibiting high-frequency resonance amplification is fulfilled.
In order to achieve the above object, an embodiment of the present invention provides a circuit for limiting a twenty-two-twelve pulse midpoint resonance of a dc power transmission system, including an upper valve bank and a lower valve bank with twelve pulses having the same structure, the upper twelve pulsating valve bank and the lower twelve pulsating valve bank are connected in series, the upper twelve pulsating valve bank and the lower twelve pulsating valve bank are symmetrical in a circuit structure, two ends of the upper and lower twelve-pulse valve groups are connected in parallel with a direct current filter, the direct current filter comprises a first capacitor group, a second capacitor and a third capacitor, the first capacitor bank, the second capacitor and the third capacitor are connected in series, the first capacitor bank comprises an upper first capacitor and a lower first capacitor, the upper first capacitor is connected with the lower first capacitor in series, and the middle points of the upper twelve-pulse valve bank and the lower twelve-pulse valve bank are connected between the upper first capacitor and the lower first capacitor.
Preferably, the positive electrode of the upper twelve-pulse valve bank is connected between the upper first capacitor and the lower first capacitor, and the negative electrode of the upper twelve-pulse valve bank is connected to the other end of the upper first capacitor.
Preferably, the twelve-pulse valve group comprises a plurality of thyristors, and the plurality of thyristors are connected in series.
Preferably, a third inductance coil is connected in parallel to two ends of the third capacitor.
Preferably, a second inductance coil is connected in parallel to two ends of the second capacitor.
Preferably, the lower first capacitor is connected with a first inductance coil in series.
Compared with the prior art, the circuit for limiting double-twelve-pulse midpoint resonance of the direct-current transmission system comprises an upper twelve-pulse valve bank and a lower twelve-pulse valve bank which have the same structure, the upper twelve-pulse valve bank and the lower twelve-pulse valve bank are connected in series, the upper twelve-pulse valve bank and the lower twelve-pulse valve bank are symmetrical in the circuit structure, two ends of the upper twelve-pulse valve bank and the lower twelve-pulse valve bank are connected in parallel with a direct-current filter, the direct-current filter comprises a first capacitor bank, a second capacitor and a third capacitor, the first capacitor bank, the second capacitor and the third capacitor are connected in series, the first capacitor bank comprises an upper first capacitor and a lower first capacitor, the upper first capacitor is connected in series with the lower first capacitor, the midpoint of the upper twelve-pulse valve bank and the lower twelve-pulse valve bank is connected between the upper first capacitor and the lower first capacitor, the direct current filter is formed by connecting a first capacitor, a second capacitor and a third capacitor in series, and by utilizing the structure of the original direct current filter, because the first capacitor bears the highest voltage in the whole circuit and has the highest manufacturing cost, the first capacitor is divided into an upper first capacitor and a lower first capacitor, the insulation levels of the two capacitors connected in series are unchanged, the equipment investment is not increased, the upper first capacitor is connected in parallel and pulsates at two ends of an upper twelve-pulse valve bank, when the direct current filter is electrified, the upper first capacitor and the upper two-pulse valve bank form a loop, high-frequency harmonics of the upper twelve-pulse valve bank can be filtered, the high-order harmonic voltage of the middle points of the upper twelve-pulse valve bank and the lower twelve-pulse valve bank is reduced, resonance is inhibited, the external resistance frequency characteristic of the modified direct current filter is unchanged, the function of the direct current filter can be realized, the method is.
Drawings
Fig. 1 is a schematic diagram of a double-twelve pulse structure of a dc transmission system of the present invention;
FIG. 2 is a schematic diagram of a 24 th harmonic equivalent circuit of a DC power transmission system according to the present invention;
fig. 3 is a circuit configuration diagram of the apparatus of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. 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.
A circuit for limiting double-twelve-pulse midpoint resonance of a direct-current transmission system comprises an upper twelve-pulse valve bank and a lower twelve-pulse valve bank which have the same structure, wherein the upper twelve-pulse valve bank and the lower twelve-pulse valve bank are connected in series, the upper twelve-pulse valve bank and the lower twelve-pulse valve bank are symmetrical in the circuit structure, two ends of the upper twelve-pulse valve bank and the lower twelve-pulse valve bank are connected in parallel with a direct-current filter, the direct-current filter comprises a first capacitor bank, a second capacitor and a third capacitor, the first capacitor bank, the second capacitor and the third capacitor are connected in series, the first capacitor bank comprises an upper first capacitor and a lower first capacitor, the upper first capacitor is connected in series with the lower first capacitor, the midpoints of the upper twelve-pulse valve bank and the lower twelve-pulse valve bank are connected between the upper first capacitor and the lower first capacitor, the twelve-pulse valve bank comprises a plurality of thyristors, several thyristors are connected in series. The positive electrode of the upper twelve-pulse valve bank is connected between the upper first capacitor and the lower first capacitor, and the negative electrode of the upper twelve-pulse valve bank is connected to the other end of the upper first capacitor.
The negative electrode of the lower twelve-pulse valve bank is connected with the positive electrode of the upper twelve-pulse valve bank, the positive electrode of the lower twelve-pulse valve bank is connected with one end of a third capacitor, the other end of the third capacitor is connected with a second capacitor, the other end of the second capacitor is connected with a first impedance, the other end of the first impedance is connected with a lower first capacitor, and the other end of the lower first capacitor is connected with the negative electrode of the lower twelve-pulse valve bank.
And two ends of the third capacitor are connected with a third inductance coil in parallel, and two ends of the second capacitor are connected with a second inductance coil in parallel.
As shown in fig. 1 and fig. 2, under the symmetric condition of twelve upper and lower ripple (mainly including the same firing angle and the same phase angle of the ac grid voltage), the 24 th harmonic voltage at the midpoint M is zero. An equivalent circuit of 24 th harmonic voltage, if neglecting the influence of stray capacitance, has:
then there are:
UdM＝(Ud-Up) /2 (formula 2)
From the above equation, Udm reaches a minimum value when the upper twelve ripple harmonic voltage is the same phase as the lower twelve ripple harmonic voltage, and Udm is zero when the amplitudes are also the same.
Therefore, to reduce the amplitude of the harmonic voltage at the midpoint M, the angle of the upper and lower twelve-pulse harmonic voltage sources needs to be adjusted to make them reach or approach the same. However, in an actual system, the upper and lower twelve pulses are difficult to be completely symmetrical, so that high-order resonance is easy to be excited in the actual system, and particularly, when the phases of the upper and lower twelve pulses are opposite, the maximum harmonic voltage can be twice as large as the original harmonic voltage.
The direct current filter is connected in parallel at two ends of an upper twelve-pulse valve bank and a lower twelve-pulse valve bank in a double twelve-pulse structure, the direct current filter is formed by connecting a first capacitor, a second capacitor and a third capacitor in series, and by utilizing the structure of the original direct current filter, because the first capacitor bears the highest voltage in the whole circuit and has the highest manufacturing cost, the first capacitor is split into the upper first capacitor and the lower first capacitor, the insulation level of the two capacitors connected in series is unchanged, the equipment investment is not increased, and the upper first capacitor is connected in parallel at two ends of the upper twelve-pulse valve bank. When the direct current filter is electrified, current flows through the direct current filter, the upper first capacitor and the upper two pulsating valve banks form a loop, the upper first capacitor absorbs high-frequency harmonics of upper twelve pulsations, so that high-order harmonic voltages of middle points of the upper twelve pulsating valve banks and the lower twelve pulsating valve banks are reduced, resonance is inhibited, the external frequency resistance characteristic of the direct current filter after modification is unchanged, and the function of the direct current filter can be still realized.
The method of splitting the first capacitor into the upper first capacitor and the lower first capacitor is easy to realize the reconstruction of the production station, and has the advantages of small reconstruction workload and less investment.
The lower first capacitor is connected with a first inductance coil in series, so that harmonic amplification and overcurrent damage of the lower first capacitor can be avoided.
The second capacitor is connected with a second inductance coil in parallel, and the third capacitor is connected with a third inductance coil in parallel, so that the filtering effect is achieved.
While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention.
Claims (6)
1. A circuit for limiting double-twelve pulse midpoint resonance of a direct current transmission system is characterized by comprising an upper twelve pulse valve bank and a lower twelve pulse valve bank which have the same structure, the upper twelve pulsating valve bank and the lower twelve pulsating valve bank are connected in series, the upper twelve pulsating valve bank and the lower twelve pulsating valve bank are symmetrical in a circuit structure, two ends of the upper and lower twelve-pulse valve groups are connected in parallel with a direct current filter, the direct current filter comprises a first capacitor group, a second capacitor and a third capacitor, the first capacitor bank, the second capacitor and the third capacitor are connected in series, the first capacitor bank comprises an upper first capacitor and a lower first capacitor, the upper first capacitor is connected with the lower first capacitor in series, and the middle points of the upper twelve-pulse valve bank and the lower twelve-pulse valve bank are connected between the upper first capacitor and the lower first capacitor;
wherein, last twelve pulsating valves and lower twelve pulsating valves are symmetrical in circuit structure, include: the trigger angle is the same, and the alternating current network voltage phase angle is the same.
2. The circuit for limiting the twenty-two-twelve pulse midpoint resonance of the direct current transmission system according to claim 1, wherein a positive electrode of the upper twelve pulse valve group is connected between the upper first capacitor and the lower first capacitor, and a negative electrode of the upper twelve pulse valve group is connected to the other end of the upper first capacitor.
3. The circuit for limiting double twelve pulse midpoint resonance of a direct current transmission system of claim 2, wherein the set of twelve pulse valves comprises a plurality of thyristors, the plurality of thyristors being connected in series.
4. The circuit for limiting twenty-two pulse midpoint resonance in a direct current power transmission system according to claim 1, wherein a third inductor is connected in parallel across said third capacitor.
5. A circuit for limiting the twenty-two pulse midpoint resonance of a dc power transmission system as claimed in claim 1, wherein a second inductor is connected in parallel across said second capacitor.
6. A circuit for limiting twenty-two pulse midpoint resonance in a DC power transmission system as claimed in claim 5, wherein said lower first capacitor is connected in series with a first inductor winding.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201810843210.5A CN108667065B (en) | 2018-07-27 | 2018-07-27 | Circuit for limiting double-twelve-pulse midpoint resonance of direct-current power transmission system |
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| CN201810843210.5A CN108667065B (en) | 2018-07-27 | 2018-07-27 | Circuit for limiting double-twelve-pulse midpoint resonance of direct-current power transmission system |
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| CN208433761U (en) * | 2018-07-27 | 2019-01-25 | 南方电网科学研究院有限责任公司 | Circuit for limiting double-twelve-pulse midpoint resonance of direct-current power transmission system |
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| CN208433761U (en) * | 2018-07-27 | 2019-01-25 | 南方电网科学研究院有限责任公司 | Circuit for limiting double-twelve-pulse midpoint resonance of direct-current power transmission system |
Non-Patent Citations (1)
| Title |
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| 特高压直流输电控制系统模型的研究;聂雪松;《中国优秀博士学位论文全文数据库工程科技Ⅱ辑》;20150915;全文 * |
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