CN212588093U - Ultra-high voltage direct current transmission system capable of suppressing harmonic waves - Google Patents

Ultra-high voltage direct current transmission system capable of suppressing harmonic waves Download PDF

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CN212588093U
CN212588093U CN202021175963.2U CN202021175963U CN212588093U CN 212588093 U CN212588093 U CN 212588093U CN 202021175963 U CN202021175963 U CN 202021175963U CN 212588093 U CN212588093 U CN 212588093U
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current
direct current
filter
transmission system
high voltage
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潘爱强
罗祾
张鹏
陈甜甜
潘玲
冯倩
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State Grid Shanghai Electric Power Co Ltd
East China Power Test and Research Institute Co Ltd
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State Grid Shanghai Electric Power Co Ltd
East China Power Test and Research Institute Co Ltd
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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
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/30—Reactive power compensation
    • 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
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/40—Arrangements for reducing harmonics
    • 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 utility model relates to an restrain extra-high voltage direct current transmission system of harmonic, including alternating current network, the current bus, alternating current filter, first converter transformer, second converter transformer, 12 ripple transverters, smoothing reactor and direct current filter, alternating current network inserts the current bus, and alternating current filter connects current bus and ground connection respectively, and first converter transformer and second converter transformer equally divide and do not connect current bus and 12 ripple transverters, and smoothing reactor and 12 ripple transverters are used for connecting the both ends of load respectively, and direct current filter connects smoothing reactor and ground connection respectively; the direct current filter is formed by connecting filter branches with 2/12 times of tuning frequency in parallel. Compared with the prior art, the utility model is provided with the filters on the direct current side and the alternating current side, which is more comprehensive and reliable; a smoothing reactor is additionally arranged to further suppress harmonic waves; the 2 nd order tuning frequency of the dc filter can significantly reduce harmonic damage in order to suppress 2 nd order resonance on the dc side.

Description

Ultra-high voltage direct current transmission system capable of suppressing harmonic waves
Technical Field
The utility model belongs to the technical field of special high voltage direct current transmission and specifically relates to a restrain special high voltage direct current transmission system of harmonic.
Background
The converter used for typical high-voltage direct-current transmission consists of thyristors, is a 12-pulse converter structure, and adopts a switching mode, so that the 12-pulse converter is typical nonlinear equipment and inevitably generates harmonic waves. The voltage level of the high-voltage direct-current transmission is high, and the transmission power is high, so that the generated harmonic waves injected into an alternating current-direct current system are also large; if the harmonic component entering the ac/dc system is too large, adverse effects may be caused on the operation of the converter itself and the dc transmission system, such as heat generation of the rotating electrical machine and the capacitor, interference with communication equipment, and unstable control of the converter.
Most of the existing extra-high voltage direct current transmission systems are only provided with smoothing reactors and direct current filters, the harmonic suppression effect is still not obvious, and the added fundamental wave trappers filter out low-frequency harmonics, so that the complexity and the cost of the system are improved.
SUMMERY OF THE UTILITY MODEL
The utility model aims at providing an extra-high voltage direct current transmission system for overcoming the defects existing in the prior art.
The purpose of the utility model can be realized through the following technical scheme:
an ultra-high voltage direct current transmission system capable of suppressing harmonic waves comprises an alternating current power grid, a current bus, an alternating current filter, a transformer bank, a 12-pulse current converter, a smoothing reactor and a direct current filter, wherein the alternating current power grid is connected to the current bus, one end of the alternating current filter is connected to the current bus, the other end of the alternating current filter is grounded, the transformer bank is respectively connected with the current bus and the 12-pulse current converter, one end of the 12-pulse current converter is directly used for being connected to a load, the other end of the 12-pulse current converter is connected to the smoothing reactor, the smoothing reactor is connected with a first branch and a second branch, the first branch is used for being connected to the load, and the second branch;
the direct current filter comprises a first filter branch and a second filter branch which are connected in parallel, the tuning frequency of the first filter branch is 2 times, and the tuning frequency of the second filter branch is 12 times;
the ultra-high voltage direct current transmission system further comprises a main controller and a low-voltage current-limiting controller, wherein the main controller is sequentially connected with the low-voltage current-limiting controller and the 12-pulse current converter, the main controller and the low-voltage current-limiting controller are both connected with the load, and the main controller is used for receiving a power control instruction and outputting a control electrode current.
Furthermore, the first filter branch is connected with a first switch, and two ends of the first filter branch and two ends of the first switch are respectively connected with a direct current polar line and a neutral bus of a power transmission line of the extra-high voltage direct current power transmission system.
Furthermore, the second filter branch is connected with a second switch, and two ends of the second filter branch and two ends of the second switch are respectively connected with a direct current polar line and a neutral bus of a power transmission line of the extra-high voltage direct current power transmission system.
Further, the smoothing reactor is a dry hollow smoothing reactor.
Further, the smoothing reactor is configured on a direct current polar line and a neutral bus of a power transmission line of the extra-high voltage direct current power transmission system.
Further, the alternating current filter is also connected with reactive compensation equipment.
Further, the low-voltage current-limiting controller is connected with the 12-pulse current converter through a current control amplifier and a current converter trigger controller in sequence.
Furthermore, a current measuring device is further arranged in an access line of the load, an adder is further arranged in a connecting line of the low-voltage current-limiting controller and the current control amplifier, and the current measuring device is accessed to the adder.
Furthermore, the main controller is also provided with a direct current modulation signal interface for receiving a modulation signal to realize direct current power modulation.
Furthermore, an inverter is also arranged in an access line of the load, and the inverter is controlled based on the AMAX.
Compared with the prior art, the utility model has the advantages of it is following:
(1) the utility model discloses suppress the extra-high voltage direct current transmission system of harmonic adds AC filter through the side of exchanging, adds DC filter at the side of direct current, suppresses the harmonic of extra-high voltage direct current transmission system through the filter, and the scheme is economical and feasible, all sets up the filter at direct current side and alternating current side, and is more comprehensive reliable; a smoothing reactor is additionally arranged on the direct current side to further carry out harmonic suppression;
in addition, according to the characteristic that the numerical value of each characteristic harmonic is reduced along with the increase of the harmonic frequency in the ultra-high voltage direct current transmission system, the harmonic with the largest harmonic damage is judged to be the low harmonic; the utility model discloses direct current filter is 2/12 parallelly connected constitutions of filter branch road of times by tuned frequency, and 12 times tuned frequency reduces polar line's harmonic voltage level for the characteristic harmonic that restraines the transverter and produce, and 2 times tuned frequency can reduce harmonic harm for 2 times resonance of restraineing the direct current side by a wide margin.
(2) The utility model discloses the subsidiary reactive compensation equipment of AC filter can effectively cooperate AC filter to satisfy the reactive power exchange demand of direct current transmission system and transverter.
(3) The utility model discloses two converter transformers who are connected with 12 pulsation transverters, one is the star connection, and another is the triangle-shaped wiring to the interchange side that makes two 6 pulsation transverters obtains the commutation voltage that the phase difference is 30, realizes that in 30 repetitive cycle, the alternation of converter valve switches on in turn, safe and reliable, and satisfies the commutation demand.
(4) The utility model discloses control subsystem includes main control unit, low pressure current-limiting controller, current control amplifier and transverter trigger control ware, satisfies the stability control demand to direct current transmission system, increases current measurement device in the access line of load, and the change of load current can be monitored, realizes real-time adjustment, the steady operation of maintenance system.
Drawings
Fig. 1 is a schematic structural diagram of an ultra-high voltage direct current transmission system for suppressing harmonic waves according to the present invention;
fig. 2 is a schematic diagram of a 6-pulse converter;
fig. 3 is a schematic structural diagram of the control subsystem of the present invention;
in the figure, 1, an alternating current power grid, 2, a current bus, 3, a first converter transformer, 4, a second converter transformer, 5, a first 6 pulse current converter, 6, a second 6 pulse current converter, 7, an alternating current filter, 8, a smoothing reactor, 9, a direct current filter, 10, a main controller, 11, a low-voltage current limiting controller, 12, an adder, 13, a current control amplifier, 14, a converter trigger controller, 15, a current measuring device, 16 and an inverter.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. The embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, but the scope of the present invention is not limited to the following embodiments.
Example 1
The embodiment provides an ultra-high voltage direct current transmission system for suppressing harmonic waves, which comprises an alternating current power grid 1, a current bus 2, an alternating current filter 7, a first converter transformer 3, a second converter transformer 4, a 12-pulse converter, a smoothing reactor 8 and a direct current filter 9, wherein the 12-pulse converter comprises a first 6-pulse converter 5 and a second 6-pulse converter 6, the alternating current power grid 1 is connected to the current bus 2, one end of the alternating current filter 7 is connected to the current bus 2, the other end of the alternating current filter is grounded, the first converter transformer 3 is respectively connected to the current bus 2 and the first 6-pulse converter 5, the second converter transformer 4 is respectively connected to the current bus 2 and the second 6-pulse converter 6, one end of the first 6-pulse converter 5 is connected to the second 6-pulse converter 6, the other end of the first converter transformer is connected to the smoothing reactor 8, and the smoothing reactor 8 and the second, one end of the direct current filter 9 is connected with the smoothing reactor 8, and the other end is grounded.
The extra-high voltage direct current transmission system also comprises a control subsystem, which is used for carrying out power modulation on the direct current transmission system, reducing harmonic interference and enhancing the stability of the direct current transmission system.
As shown in fig. 3, the control subsystem includes a main controller 10, a low voltage current limiting controller 11, a current control amplifier 13 and an inverter trigger controller 14, which are connected in sequence, the inverter trigger controller 14 is connected 12 to the pulsating inverter, a current measuring device 15 is further disposed in an access line of the load, an adder 13 is further disposed in a connection line between the low voltage current limiting controller 11 and the current control amplifier 13, and the current measuring device 15 is connected to the adder 13. An inverter 16 is also provided in the access line of the load, and the inverter 16 is an inverter based on AMAX control. The main controller 10 and the low-voltage current-limiting controller 11 are both connected with a load, and the main controller 10 is used for receiving a power control command and outputting a control electrode current.
In the specific implementation, the main elements of the main loop of the direct current transmission system comprise an alternating current filter, a reactive power compensation device, a converter transformer, a converter valve, a direct current filter, a smoothing reactor, a direct current transmission line, a grounding electrode, a circuit breaker, a switch disconnecting link and a lightning arrester.
The following describes each part of the extra-high voltage dc transmission system in this embodiment in detail.
1. DC filter
The dc filter 9 includes a first filter branch and a second filter branch connected in parallel, the tuning frequency of the first filter branch is 2 times, and the tuning frequency of the second filter branch is 12 times.
The first filter branch is connected with a first switch, and two ends of the first filter branch and two ends of the first switch are respectively connected with a direct current polar line and a neutral bus of a power transmission line of the ultra-high voltage direct current power transmission system.
The second filter branch is connected with a second switch, and two ends of the second filter branch and two ends of the second switch are respectively connected with a direct current polar line and a neutral bus of a power transmission line of the ultra-high voltage direct current power transmission system.
In the specific implementation, the direct current filter adopts a simplified filter and is formed by connecting filter branches (HP2/HP12) with the tuning frequency of 2/12 times in parallel. The combined filter is connected to the pole line and the neutral bus via a switch, respectively. The 2-order tuning frequency is added to the DC filter mainly for suppressing the 2-order resonance on the DC side, and the 12-order tuning frequency mainly for suppressing the characteristic harmonic generated by the inverter and reducing the harmonic voltage level of the polar line.
2. Smoothing reactor
The smoothing reactor 8 is a dry hollow smoothing reactor.
Smoothing reactors 8 are arranged on a direct current polar line and a neutral bus of a power transmission line of the extra-high voltage direct current power transmission system.
In this embodiment, the dry hollow smoothing reactor has an inductance of 300mH, and the polar line and the neutral line are symmetrically arranged. In connection with the converter station arrangement needs, each pole line and neutral side is configured with 2 x 75 mH.
3. AC filter
In addition to the ac filter providing a filtering function, usually at the fundamental wave, it also provides reactive power to the system, and in this embodiment the ac filter 7 is also connected to reactive compensation equipment.
4. Control subsystem
The master controller 10(MC) is mainly responsible for power control of the system, receives a remote control center power command, and calculates the pole current output to each pole. In MC systems, the power control part is also referred to as PPC. Besides the power control in normal operation, the controller is also responsible for the control functions of starting, stopping, locking, restarting and the like of direct current. In addition, an interface of a direct current modulation signal is reserved in the PPC, and the PPC can receive the modulation signal of an upper layer to realize direct current power modulation and play a role of enhancing system stability.
The low-voltage current-limiting controller 11(VDCOL) low-voltage current-limiting control means that, when the dc voltage is lower than a certain value under certain conditions, the command value of the current regulator is automatically reduced until the dc voltage recovers, and the VDCOL low-voltage current-limiting controller is an essential key module in the dc pole control system and mainly functions as:
1) the reactive power requirement on an alternating current system is reduced while the direct current power is reduced, and the alternating current voltage is maintained;
2) the instability of power during and after disturbance of the alternating current system is avoided;
3) the direct current system is helped to carry out rapid and controllable recovery after the alternating current and direct current faults are cleared;
4) avoid the overlarge valve stress caused by continuous phase change failure and reduce the harm to the valve
5) The likelihood of a continuous commutation failure during valve recovery is reduced.
And the current control amplifier 13(CCA) realizes constant current control of the direct current transmission system according to the direct current instruction value and outputs a converter valve trigger angle.
The converter trigger controller 14(CFC) belongs to a converter control stage, adjusts and limits the trigger angle output by the CCA according to different operating conditions, calculates the trigger pulse time, and maintains stable operation of the system.
When the inverter 16 is controlled by γ, the dc voltage will decrease in proportion to the dc current. This means that the inverter acts as a negative resistance. This negative resistance will cause stability problems if the ac grid is weak. If the inverter is capable of operating in the fixed alpha mode, the voltage of the inverter will increase in proportion to the dc current. The dynamic resistance at this moment becomes positive and the stability of the current control will be significantly improved. Therefore, in order to increase the stability of the system, a positive slope line segment is artificially added in the characteristic curve of the inverter, and is used for AMAX control, and then a VDCOL function is added.
4. Other parts
Both valve-side windings of the first converter transformer 3 are star-connected. The two valve side windings of the second converter transformer 4 are star-connected and delta-connected, respectively. The first 6 and second 6 pulsating current converters 5, 6 are both three-phase bridge circuits. The first 6 and second 6 pulsating converters 5, 6 each comprise six converter valves comprising a plurality of thyristors.
In a specific implementation, as shown in fig. 2, each 6-pulse converter (6p) is a three-phase bridge circuit, VT 1-VT 6 in fig. 2 represent 6 converter valves, and numbers 1-6 represent the turn-on sequence of the converter valves. Each converter valve is composed of about one hundred thyristors which are connected in series. u. ofa、ub、ucEquivalent fundamental phase voltage of an alternating current system; l isrThe equivalent commutation inductance of each phase consists of the leakage inductance of the converter transformer and the equivalent inductance of the alternating current system; l isdThe inductance value of the smoothing reactor; m and n are respectively a common cathode point and a common anode point of the 6-pulse rectifier; n is the AC system reference potential.
The 12-pulse converter is formed by connecting two 6-pulse converters in series on a direct current side, and the alternating current side of the 12-pulse converter is connected in parallel through a converter transformer. One valve side winding of the converter transformer is in star connection, and the other valve side winding of the converter transformer is in delta connection, so that the alternating current sides of the two 6-pulse converters obtain commutation voltages with the phase difference of 30 degrees. The normal operation mode of the 12-pulse rectifier is that 4 converter valves and 5 converter valves are alternately switched on in a 30 ° repetition period.
The foregoing has described in detail preferred embodiments of the present invention. It should be understood that numerous modifications and variations can be devised by those skilled in the art in light of the present teachings without departing from the inventive concepts. Therefore, the technical solutions that can be obtained by a person skilled in the art through logic analysis, reasoning or limited experiments based on the prior art according to the concepts of the present invention should be within the scope of protection defined by the claims.

Claims (10)

1. An ultra-high voltage direct current transmission system for suppressing harmonic waves is characterized by comprising an alternating current power grid (1), a current bus (2), an alternating current filter (7), a transformer bank, a 12-pulse current converter, a smoothing reactor (8) and a direct current filter (9), the alternating current power grid (1) is connected with the current bus (2), one end of the alternating current filter (7) is connected with the current bus (2), the other end is grounded, the transformer banks are respectively connected with the current bus (2) and the 12-pulse current converter, one end of the 12-pulse current converter is directly used for connecting a load, the other end of the 12-pulse current converter is connected with the smoothing reactor (8), the smoothing reactor (8) is connected with a first branch circuit and a second branch circuit, the first branch circuit is used for accessing a load, and the second branch circuit is connected with the direct current filter (9) and then grounded;
the direct current filter (9) comprises a first filter branch and a second filter branch which are connected in parallel, the tuning frequency of the first filter branch is 2 times, and the tuning frequency of the second filter branch is 12 times;
the ultra-high voltage direct current transmission system further comprises a main controller (10) and a low-voltage current-limiting controller (11), wherein the main controller (10) is sequentially connected with the low-voltage current-limiting controller (11) and the 12 pulse current converter, the main controller (10) and the low-voltage current-limiting controller (11) are connected with the load, and the main controller (10) is used for receiving a power control instruction and outputting a control pole current.
2. The harmonic suppression extra-high voltage direct current transmission system according to claim 1, wherein the first filter branch is connected with a first switch, and two ends of the first filter branch and the first switch are respectively connected with a direct current polar line and a neutral bus of a transmission line of the extra-high voltage direct current transmission system.
3. The harmonic suppression extra-high voltage direct current transmission system according to claim 1, wherein a second switch is connected to the second filter branch, and two ends of the second filter branch and the second switch are respectively connected to a direct current pole line and a neutral bus of a transmission line of the extra-high voltage direct current transmission system.
4. The extra-high voltage direct current transmission system capable of suppressing the harmonic waves according to claim 1, wherein the smoothing reactor (8) is a dry hollow smoothing reactor.
5. The harmonic suppression extra-high voltage direct current transmission system according to claim 1, wherein a direct current pole line and a neutral bus of a transmission line of the extra-high voltage direct current transmission system are both provided with the smoothing reactor (8).
6. The extra-high voltage direct current transmission system with harmonic suppression according to claim 1, characterized in that a reactive power compensation device is further connected to the alternating current filter (7).
7. The extra-high voltage direct current transmission system capable of suppressing the harmonic waves according to claim 1, wherein the low voltage current limiting controller (11) is connected with the 12-pulse converter through a current control amplifier (13) and a converter triggering controller (14) in sequence.
8. The extra-high voltage direct current transmission system capable of suppressing the harmonic waves according to claim 7, wherein a current measuring device (15) is further arranged in an access line of the load, an adder (12) is further arranged in a connection line of the low-voltage current limiting controller (11) and the current control amplifier (13), and the current measuring device (15) is accessed to the adder (12).
9. The extra-high voltage direct current transmission system capable of suppressing the harmonic waves according to claim 1, wherein the main controller (10) is further provided with a direct current modulation signal interface for receiving a modulation signal to realize direct current power modulation.
10. The extra-high voltage direct current transmission system capable of suppressing the harmonic waves according to claim 1, wherein an inverter (16) is further arranged in an access line of the load, and the inverter (16) is an AMAX control-based inverter (16).
CN202021175963.2U 2020-06-22 2020-06-22 Ultra-high voltage direct current transmission system capable of suppressing harmonic waves Active CN212588093U (en)

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Application Number Priority Date Filing Date Title
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