CN111884230B - Method and device for reducing bus voltage fluctuation in switching process of alternating current filter bank - Google Patents
Method and device for reducing bus voltage fluctuation in switching process of alternating current filter bank 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
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
- H02J3/16—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load by adjustment of reactive power
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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
- H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
- H02J3/1821—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators
- H02J3/1835—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators with stepless control
- H02J3/1842—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators with stepless control wherein at least one reactive element is actively controlled by a bridge converter, e.g. active filters
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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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- 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
- Y02E40/10—Flexible AC transmission systems [FACTS]
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- 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
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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 method for reducing bus voltage fluctuation in the switching process of an alternating current filter bank, which comprises the following steps: detecting whether a control system of the direct current converter station sends an input control signal or a cut-off control signal of an alternating current filter bank in real time; after the alternating current filter bank is actually put into or cut off, measuring the effective value of the alternating current bus voltage of the direct current converter station in real time, calculating the change rate of the effective value of the alternating current bus voltage in real time, and generating a corresponding additional reactive power instruction; and adding the additional reactive power instruction to an original reactive power instruction of the STATCOM coordination controller to obtain a target reactive power instruction, and performing reactive power compensation according to the target reactive power instruction. By implementing the embodiment of the invention, the fluctuation amplitude of the alternating current bus voltage of the converter station in the switching process of the alternating current filter bank can be effectively reduced, so that the voltage stress problem of the alternating current bus in the switching process of the alternating current filter bank can be effectively inhibited.
Description
Technical Field
The invention relates to the field of direct current transmission, in particular to a method and a device for reducing fluctuation of bus voltage in the switching process of an alternating current filter bank.
Background
The high-voltage direct-current transmission has the advantages of energy conservation, low line manufacturing cost and the like, and plays an important role in long-distance and high-power transmission. At present, the direct current transmission system based on the thyristor converter valve is most widely applied and is called a conventional direct current transmission system. In order to compensate a large amount of reactive power consumed by the characteristics of the thyristor converter valve and inhibit the characteristic harmonic wave injected into an alternating current power grid, an alternating current side of a conventional direct current transmission converter station is provided with an alternating current filter bank with the direct current rated capacity of about 40% -60%. The ac filter bank is composed of a number of ac filter subgroups, the switching of which generally depends on the value of the reactive power absorbed by the converter station from the ac power grid. When the reactive power value exceeds the upper limit of the control range, the control system of the direct current converter station sends a control signal for putting into a group of filter groups; and when the reactive power value is lower than the lower limit of the control range, the control system of the direct current converter station sends out a control signal for cutting off a group of filter subgroups. In general, after a certain time delay is passed when a switching control signal is sent, the filter group is actually switched on or switched off. Because the reactive capacity of the filter group is large, the alternating current bus voltage of the direct current converter station can generate large fluctuation at the switching moment, so that the voltage peak value in the switching process is too large to cause the overvoltage problem, or the voltage valley value in the cutting process is too low to cause the undervoltage problem.
Currently, some dc converter stations are equipped with a Static Synchronous Compensator (STATCOM) with a certain capacity. The STATCOM is flexible to control and has the functions of quickly transmitting and absorbing reactive power. In the prior art, there is a method of reducing ac voltage fluctuation caused by the input or cut-off of an ac filter by pre-adjusting the output reactive power of a STATCOM before the ac filter bank performs the input or cut-off operation; and a method for improving the transient voltage fluctuation in the switching process of the alternating current filter by changing the PI parameter of the STATCOM. However, in the process of implementing the invention, the inventor finds that the prior art has at least the following problems: pre-adjusting the reactive power output by the STATCOM before the filter bank performs the switching-in or switching-off action can change the reactive power output of the STATCOM in advance, and the pre-adjusted reactive power can change the steady-state voltage level of the converter station before the filter bank is switched in or switched off, so that the steady-state voltage level of the converter station before the filter bank is switched in or switched off can be too high or too low; in the method for improving the transient voltage fluctuation in the switching process of the alternating current filter by changing the PI controller parameter of the STATCOM, the change of the design setting value of the STATCOM is not beneficial to ensuring the safety and the reliability of a power system in practical engineering application because the PI parameter of the STATCOM is closely related to various performances of the STATCOM.
Disclosure of Invention
The embodiment of the invention aims to provide a method and a device for reducing the voltage fluctuation of a bus of an alternating current filter bank in the switching process, which can effectively reduce the fluctuation amplitude of the voltage of the alternating current bus of a converter station in the switching process of the alternating current filter bank, thereby effectively inhibiting the voltage stress problem of the alternating current bus in the switching process of the alternating current filter bank.
In order to achieve the above object, an embodiment of the present invention provides a method for reducing bus voltage fluctuation during switching of an ac filter bank, including:
detecting whether a control system of the direct current converter station sends an input control signal or a cut-off control signal of an alternating current filter bank in real time;
when detecting that the input control signal or the cut-off control signal of the alternating current filter bank is sent by the direct current converter station control system, determining the real input or cut-off moment of the alternating current filter bank, and measuring the effective value of the alternating current bus voltage of the direct current converter station in real time after the alternating current filter bank is really input or cut off;
calculating the change rate of the effective value of the alternating-current bus voltage in real time according to the effective value of the alternating-current bus voltage to generate a corresponding additional reactive power instruction;
adding the additional reactive power instruction to an original reactive power instruction of a STATCOM coordinated controller to obtain a target reactive power instruction of the STATCOM coordinated controller;
and performing reactive power compensation according to the target reactive power instruction.
As an improvement of the above scheme, the calculating, in real time, a change rate of the effective value of the ac bus voltage according to the effective value of the ac bus voltage to generate a corresponding additional reactive power instruction specifically includes:
filtering the effective value of the alternating-current bus voltage through a low-pass filter;
inputting the filtered effective value of the alternating-current bus voltage into a differential hysteresis link, and calculating the differential quantity of the alternating-current bus voltage to obtain the change rate of the effective value of the alternating-current bus voltage;
and inputting the differential quantity of the alternating-current bus voltage into an inverting proportional link for correction so as to generate the additional reactive power instruction.
As an improvement of the above scheme, the adding the additional reactive power instruction to the original reactive power instruction of the STATCOM coordination controller to obtain the target reactive power instruction of the STATCOM coordination controller specifically includes:
and in a first preset time after the AC filter bank is really put into or cut off, adding the additional reactive power instruction to an original reactive power instruction of the STATCOM coordination controller in real time to obtain a target reactive power instruction of the STATCOM coordination controller.
As a modification of the above solution, the first preset time period is determined according to a transient voltage time period of the ac bus after the ac filter bank is switched on or off by the dc converter station.
As an improvement of the above scheme, the first preset time period is 0.15s to 0.2 s.
The embodiment of the invention also provides a device for reducing the voltage fluctuation of the bus in the switching process of the alternating current filter bank, which comprises the following steps:
the switching control signal detection module is used for detecting whether the control system of the direct current converter station sends an input control signal or a cut-off control signal of the alternating current filter bank or not in real time;
the alternating current bus voltage measuring module is used for determining the real switching-in or switching-out moment of the alternating current filter bank when detecting that the switching-in control signal or the switching-out control signal of the alternating current filter bank is sent by the direct current converter station control system, and measuring the effective value of the alternating current bus voltage of the direct current converter station in real time after the alternating current filter bank is really switched in or switched out;
the additional reactive power instruction generating module is used for calculating the change rate of the effective value of the alternating-current bus voltage in real time according to the effective value of the alternating-current bus voltage so as to generate a corresponding additional reactive power instruction;
the target reactive power instruction generation module is used for adding the additional reactive power instruction to an original reactive power instruction of the STATCOM coordination controller so as to obtain a target reactive power instruction of the STATCOM coordination controller;
and the reactive power compensation module is used for performing reactive power compensation according to the target reactive power instruction.
As an improvement of the above scheme, the additional reactive power instruction generation module is specifically configured to:
filtering the effective value of the alternating-current bus voltage through a low-pass filter;
inputting the filtered effective value of the alternating-current bus voltage into a differential hysteresis link, and calculating the differential quantity of the alternating-current bus voltage to obtain the change rate of the effective value of the alternating-current bus voltage;
and inputting the differential quantity of the alternating-current bus voltage into an inverting proportional link for correction so as to generate the additional reactive power instruction.
As an improvement of the above scheme, the target reactive power instruction generation module is specifically configured to:
and in a first preset time after the AC filter bank is really put into or cut off, adding the additional reactive power instruction to an original reactive power instruction of the STATCOM coordination controller in real time to obtain a target reactive power instruction of the STATCOM coordination controller.
As a modification of the above solution, the first preset time period is determined according to a transient voltage time period of the ac bus after the ac filter bank is switched on or off by the dc converter station.
As an improvement of the above scheme, the first preset time period is 0.15s to 0.2 s.
Compared with the prior art, the method and the device for reducing the bus voltage fluctuation in the switching process of the alternating current filter bank disclosed by the invention detect whether the control system of the direct current converter station sends the switching control signal or the cutting control signal of the alternating current filter bank in real time. And after the AC filter bank is actually put into or cut off, measuring the effective value of the AC bus voltage of the DC convertor station in real time. And calculating the change rate of the effective value of the alternating-current bus voltage in real time according to the effective value of the alternating-current bus voltage so as to generate a corresponding additional reactive power instruction. And adding the additional reactive power instruction to an original reactive power instruction of the STATCOM coordination controller to obtain a target reactive power instruction of the STATCOM coordination controller, and performing reactive power compensation according to the target reactive power instruction. According to the embodiment of the invention, after the input control signal or the cut-off control signal of the alternating current filter bank is detected, the corresponding additional reactive power instruction is generated in real time according to the change rate of the alternating current bus voltage, so that the STATCOM can absorb or inject reactive power with a certain capacity in the reverse direction on the basis of the original reactive power output, the reactive power variation of the alternating current network at the moment after the switching of the alternating current filter bank is reduced, the fluctuation amplitude of the alternating current bus voltage at the moment after the input or the cut-off of the alternating current filter bank is reduced, and the voltage stress problem of the converter station bus in the input or the cut-off process of the alternating current filter bank is effectively inhibited. Meanwhile, the embodiment of the invention does not influence the steady-state voltage level of the alternating current bus before the alternating current filter bank is put into or cut off, and the original design setting value of the STATCOM is not required to be changed.
Drawings
Fig. 1 is a schematic flowchart illustrating steps of a method for reducing bus voltage fluctuation during switching of an ac filter bank according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of a dc converter station system equipped with a STATCOM according to a first embodiment of the present invention;
fig. 3 is a schematic control logic diagram of a STATCOM coordination controller of a dc converter station according to an embodiment of the present invention;
fig. 4 is a flowchart illustrating step S3 of the method for reducing bus voltage fluctuation during switching of the ac filter bank according to the first embodiment of the present invention;
FIG. 5 is a schematic control logic diagram of an additional control branch of the STATCOM according to an embodiment of the present invention;
fig. 6 is a schematic diagram comparing response curves of ac bus voltages before and after switching of the ac filter bank in the first embodiment of the present invention;
fig. 7 is a schematic structural diagram of a device for reducing bus voltage fluctuation during switching of an ac filter bank according to a second embodiment 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.
Referring to fig. 2, a schematic structural diagram of a dc converter station system equipped with a STATCOM according to a first embodiment of the present invention is shown. The direct current converter station system comprises a direct current network, a smoothing reactor, a converter valve, a converter transformer, an alternating current network, a direct current converter station control system, an alternating current filter bank, an STATCOM coordination controller, a plurality of STATCOMs and other equipment. Wherein, VDCAnd IDCRespectively, DC voltage and DC current, V, of a DC transmission systemACIs an AC bus voltage, Q, of a DC converter stationACFor reactive power, Q, absorbed from an AC network by a DC converter stationSTTotal reactive power, i, output for STATCOMqref1，iqref2，…iqrefnAnd respectively allocating reactive current instructions of STATCOM 1, STATCOM 2 and … SATATCOM N to the STATCOM coordination controller, wherein N is the total number of the STATCOMs of the direct current converter station, and N is the total number of the alternating current filter groups of the direct current converter station.
The alternating current filter bank is used for compensating a large amount of reactive power consumed by the characteristics of the thyristor converter valve and inhibiting characteristic harmonic waves injected into an alternating current power grid, the alternating current filter bank comprises a plurality of alternating current filter subgroups, and a control system of the direct current converter station sends an input control signal or a cut-off control signal to control the input and cut-off of the alternating current filter subgroups.
Specifically, under a steady-state condition, the control system of the direct current converter station ensures that steady-state reactive power absorbed by the direct current converter station from an alternating current network is within a certain control range [ Q1, Q2 ] by controlling the number of the input alternating current filter subgroups]. The Q1 and Q2 values vary according to the ac network to which the dc converter station is connected, and are closely related to the capacity of the filter sub-group. When the reactive power absorbed by the DC convertor station from the AC network satisfies QAC>At Q2, the dc converter station control system sends a control signal to put into a filter bank, i.e. the ac filter bank put-into control signal is immediately set high. When the reactive power absorbed by the DC convertor station from the AC network satisfies QAC<At Q1, the dc converter station control system sends out a control signal to cut off a group of filter subgroups, i.e. the ac filter subgroup cut-off control signal is immediately set high.
It is worth mentioning that when Q isACValues other than [ Q1, Q2 ]]In the range, the control system of the direct current converter station immediately sends out a switching control signal of the filter group, but the filter group is really put into or cut off after T seconds of delay. Because the reactive capacity of the filter group is large, the AC bus voltage value V of the converter station can be caused at the switching momentACThere is a large fluctuation. When the alternating current filter group is put into use, the bus voltage of the converter station has higher peak value and may appearThe problem of overvoltage occurs; when the alternating current filter group is cut off, the bus voltage of the converter station has a low valley value, and the problem of under-voltage may occur. After the AC filter bank is switched for a period of time, the voltage fluctuation is attenuated.
Referring to fig. 3, a schematic control logic diagram of a coordinated controller of a dc converter station STATCOM according to an embodiment of the present invention is shown. Under normal working conditions, the STATCOM coordinated controller operates in a constant reactive power control mode, and generates a reactive power instruction QSTREFAnd sends a reactive power command QSTREFAlgorithm i for converting into reactive current instructionqrefAnd distributing the reactive power to each STATCOM so that each STATCOM outputs corresponding reactive power. Reactive power command QSTREFThe value of (b) is generally given constant. When each STATCOM runs to a steady state, QSTAnd QSTREFAre substantially equal. In general, the STATCOM can output reactive power to the ac bus, and control the steady-state voltage of the ac bus within a reasonable range.
The embodiment of the invention provides a method for reducing bus voltage fluctuation in the switching process of an alternating current filter bank, which is suitable for a direct current converter station system provided with a STATCOM. Referring to fig. 1, a schematic step flow chart of a method for reducing bus voltage fluctuation in a switching process of an ac filter bank according to an embodiment of the present invention is shown. The method for reducing the bus voltage fluctuation in the switching process of the alternating current filter bank is executed through steps S1 to S5:
and S1, detecting whether the control system of the direct current converter station sends an input control signal or a cut-off control signal of the alternating current filter bank in real time.
S2, when detecting that the input control signal or the cut-off control signal of the alternating current filter bank is sent by the direct current converter station control system, determining the real input or cut-off moment of the alternating current filter bank, and measuring the effective value of the alternating current bus voltage of the direct current converter station in real time after the alternating current filter bank is actually input or cut off;
s3, calculating the change rate of the effective value of the alternating-current bus voltage in real time according to the effective value of the alternating-current bus voltage to generate a corresponding additional reactive power instruction;
s4, adding the additional reactive power instruction to an original reactive power instruction of the STATCOM coordination controller to obtain a target reactive power instruction of the STATCOM coordination controller;
and S5, performing reactive power compensation according to the target reactive power instruction.
It should be noted that, at the moment after the switching of the ac filter group, the ac bus voltage V of the converter stationACThe reason for the higher peaks and lower valleys is: the ac network suddenly increases and suddenly decreases a large amount of reactive power immediately after the ac filter bank is switched.
In the embodiment of the invention, in order to reduce the fluctuation amplitude of the alternating current bus voltage in the switching process of the alternating current filter bank, whether the input control signal or the cut-off control signal of the alternating current filter bank is sent by the control system of the direct current converter station is detected in real time. When the input control signal or the cut-off control signal is detected, the real input or cut-off time of the alternating current filter bank is determined according to the time when the input control signal or the cut-off control signal is detected and the predetermined T second delay, and after the alternating current filter bank is really input or cut off, the effective value V of the alternating current bus voltage of the direct current converter station at the current time is detected in real timeACAnd calculating the change rate of the effective value of the alternating-current bus voltage in real time. According to the effective value V of the AC bus voltageACOf the original reactive power instruction Q on the STATCOM coordinated controllerSTREFCorresponding additional reactive power instructions are added, so that the STATCOM can absorb or inject reactive power with certain capacity in the reverse direction on the basis of the original reactive power output, the reactive power variation of an alternating current filter group in an instant alternating current network after switching is reduced, and the bus voltage V of the converter station is reducedACThe amplitude of the fluctuation of (a).
It should be noted that, after the dc converter station control system sends the input or cut-off control signal of the filter group, the time delay until the filter group is actually input or cut off is T seconds, and the time delay may be obtained in advance according to the actual operation condition of the dc transmission system, and the specific delay time is not limited herein.
By adopting the technical means of the embodiment of the invention, after the real input or the real removal of the alternating current filter bank is determined, the corresponding additional reactive power instruction is generated in real time according to the change rate of the alternating current bus voltage, and the final reactive power instruction (namely the target reactive power instruction) of the STATCOM coordination controller is adjusted in real time so as to realize the regulation and control of the alternating current bus voltage at the moment after the real input or the removal of the alternating current filter bank, therefore, the steady-state voltage level of the alternating current bus before the input or the removal of the alternating current filter bank can not be influenced.
As a preferred embodiment, refer to fig. 4, which is a schematic flowchart of step S3 of a method for reducing fluctuation of bus voltage during switching of an ac filter bank in an embodiment of the present invention. The step S3 is specifically executed by steps S31 to S33:
and S31, filtering the effective value of the alternating-current bus voltage through a low-pass filter.
And S32, inputting the filtered effective value of the alternating-current bus voltage into a differential hysteresis link, and calculating the differential quantity of the alternating-current bus voltage to obtain the change rate of the effective value of the alternating-current bus voltage.
And S33, inputting the differential quantity of the alternating-current bus voltage into an inverting proportional link for correction so as to generate the additional reactive power command.
Specifically, the effective value V of the alternating-current bus voltage of the direct-current converter station is obtained according to real-time measurementACAnd finally, inverting the differential quantity of the alternating-current bus voltage and correcting the differential quantity through a proportional link to form the additional reactive power instruction.
The additional reactive power instruction is for indicating an amount of reactive power output by the STATCOM coordination controller that requires an additional output. It is understood that when detecting that the dc converter station sends an input control signal of an ac filter bank, the reactive power output amount in the additional reactive power instruction should be a negative value; when the direct current converter station is detected to send out a cutting control signal of the alternating current filter bank, the reactive power output quantity in the additional reactive power instruction is a positive value.
Specifically, the mathematical model of the differential hysteresis link is as follows:
preferably, Td＝0.1。
The mathematical model of the inverse proportion link is as follows: -Kd；
Preferably, Kd＝1。
As a preferred implementation manner, step S4 of the method for reducing fluctuation of bus voltage during switching of the ac filter bank in the first embodiment of the present invention is specifically:
a first predetermined duration T after the actual switching in or switching out of the AC filter bankfAnd adding the additional reactive power instruction to an original reactive power instruction of the STATCOM coordination controller in real time to obtain a target reactive power instruction of the STATCOM coordination controller.
In the embodiment of the invention, the original reactive power instruction Q of the STATCOM coordinated controllerSTREFThe adjusting time of the additional reactive power instruction of the upper accessory is the first preset time length TfI.e. at the start of the actual putting in or cutting out of the ac filter bank at the dc converter station, at TfDuring the duration, by measuring the effective value V of the AC bus voltageACAnd generating a corresponding additional reactive power instruction, adding the additional reactive power instruction to the original reactive power instruction to obtain a target reactive power instruction of the STATCOM coordination controller, and controlling the STATCOM to perform reactive power compensation according to the target reactive power instruction. And the elapsed time TfAnd then stopping generating the additional reactive power signal, and controlling the STATCOM to perform reactive power compensation according to the original reactive power instruction.
Further, the first pre-stageSet time length TfThe method is determined according to the transient voltage time period of the alternating current bus of the direct current converter station after the alternating current filter bank is put into or cut off. The transient voltage duration of the alternating current bus of the direct current converter station after the switching of the alternating current filter bank, that is, the duration required by the time period from the steady state voltage of the alternating current bus before the switching of the alternating current filter bank to the recovery of the alternating current bus to the steady state voltage after the switching of the alternating current filter bank, can be obtained through priori knowledge, and is set as the first preset duration TfTherefore, in the transient voltage time period of the alternating current bus, additional reactive power instructions are generated and superposed to reduce the reactive variable quantity of the alternating current network of the alternating current filter group immediately after switching and reduce the bus voltage V of the converter stationACThe amplitude of the fluctuation of (a).
Preferably, the first preset time period TfIs 0.15 s-0.2 s.
As a preferred implementation manner, referring to fig. 5, a schematic control logic diagram of an additional control branch of the STATCOM in the first embodiment of the present invention is shown. In the embodiment of the invention, an additional control branch related to an additional reactive power instruction is added on the control logic of the original reactive power instruction of the STATCOM coordinated controller. Wherein, flag is an identification variable for judging whether the additional control branch is put into or not. And when the flag variable is 0, indicating that the additional control branch is not put into, and on the contrary, when the flag variable is 1, indicating that the additional control branch is put into. When the input or cut-off control signal of the alternating current filter group is not detected, the flag variable is always 0, and at the moment, no additional reactive power instruction is added to the original reactive power instruction Q of the STATCOM coordination controllerSTREFThe above. When an input or cut-off control signal of the alternating current filter group is detected, after T seconds of delay, namely after the alternating current filter group is determined to be really input or cut off, setting a flag variable from 0 to 1, and at the moment, setting an effective value V of the alternating current bus voltage according to the detected effective value V of the alternating current bus voltageACAnd the calculated additional reactive power instruction is added to an original reactive power instruction Q of the STATCOM coordination controllerSTREFThe above. Maintaining a first preset duration TfThereafter, the flag variable is set back to 0 from 1.
For example, refer to fig. 6, which is a schematic diagram comparing response curves of ac bus voltages before and after the ac filter bank is switched in the first embodiment of the present invention. According to fig. 6, it can be seen that when a dc converter station is put into a group of ac filter subgroups and a group of ac filter subgroups is cut off, the STATCOM additional control branch circuit compares the response curves of the bus voltages of the converter stations before and after the addition of the STATCOM additional control branch circuit. Fig. 6(a) is a schematic diagram of a response curve of an ac bus voltage when the dc converter station control system sends an input control signal of the ac filter bank; fig. 6(b) is a schematic diagram of a response curve of the ac bus voltage when the dc converter station control system sends out the cut-off control signal of the ac filter bank. After the STATCOM additional control branch is added, the fluctuation amplitude of the alternating current bus voltage of the converter station is obviously reduced at the moment after the alternating current filter group is put into and cut off. And the final steady-state voltage value after the STATCOM additional control branch circuit is added is consistent with the final steady-state voltage value under the condition that the additional control branch circuit is not added.
The embodiment of the invention provides a method for reducing the voltage fluctuation of a bus in the switching process of an alternating current filter bank, which detects whether a control system of a direct current converter station sends an input control signal or a cut-off control signal of the alternating current filter bank in real time. And after the AC filter bank is actually put into or cut off, measuring the effective value of the AC bus voltage of the DC convertor station in real time. And calculating the change rate of the effective value of the alternating-current bus voltage in real time according to the effective value of the alternating-current bus voltage so as to generate a corresponding additional reactive power instruction. And adding the additional reactive power instruction to an original reactive power instruction of the STATCOM coordination controller to obtain a target reactive power instruction of the STATCOM coordination controller, and performing reactive power compensation according to the target reactive power instruction. According to the embodiment of the invention, after the input control signal or the cut-off control signal of the alternating current filter bank is detected, the corresponding additional reactive power instruction is generated in real time according to the change rate of the alternating current bus voltage, so that the STATCOM can absorb or inject reactive power with a certain capacity in the reverse direction on the basis of the original reactive power output, the reactive power variation of the alternating current network at the moment after the switching of the alternating current filter bank is reduced, the fluctuation amplitude of the alternating current bus voltage at the moment after the input or the cut-off of the alternating current filter bank is reduced, and the voltage stress problem of the converter station bus in the input or the cut-off process of the alternating current filter bank is effectively inhibited. Meanwhile, the embodiment of the invention does not influence the steady-state voltage level of the alternating current bus before the alternating current filter bank is put into or cut off, and the original design setting value of the STATCOM is not required to be changed.
Fig. 7 is a schematic structural diagram of a device for reducing bus voltage fluctuation during switching of an ac filter bank according to a second embodiment of the present invention. The second embodiment of the present invention provides an apparatus 20 for reducing bus voltage fluctuation during switching of an ac filter bank, including: the system comprises a switching control signal detection module 21, an alternating current bus voltage measurement module 22, an additional reactive power instruction generation module 23, a target reactive power instruction generation module 24 and a reactive power compensation module 25; wherein the content of the first and second substances,
the switching control signal detection module 21 is configured to detect whether the dc converter station control system sends an input control signal or a cut-off control signal of the ac filter bank in real time;
the ac bus voltage measuring module 22 is configured to determine a real time when the ac filter bank is actually switched on or switched off when detecting that the dc converter station control system sends a switching-on control signal or a switching-off control signal of the ac filter bank, and measure an effective value of an ac bus voltage of the dc converter station in real time after the ac filter bank is actually switched on or switched off;
the additional reactive power instruction generating module 23 is configured to calculate, in real time, a change rate of the effective value of the ac bus voltage according to the effective value of the ac bus voltage, so as to generate a corresponding additional reactive power instruction;
the target reactive power instruction generating module 24 is configured to attach the additional reactive power instruction to an original reactive power instruction of the STATCOM coordination controller to obtain a target reactive power instruction of the STATCOM coordination controller;
and the reactive power compensation module 25 is configured to perform reactive power compensation according to the target reactive power instruction.
As a preferred embodiment, the additional reactive power instruction generating module 23 is specifically configured to:
filtering the effective value of the alternating-current bus voltage through a low-pass filter;
inputting the filtered effective value of the alternating-current bus voltage into a differential hysteresis link, and calculating the differential quantity of the alternating-current bus voltage to obtain the change rate of the effective value of the alternating-current bus voltage;
and inputting the differential quantity of the alternating-current bus voltage into an inverting proportional link for correction so as to generate the additional reactive power instruction.
As a preferred embodiment, the target reactive power instruction generating module 24 is specifically configured to:
and in a first preset time after the AC filter bank is really put into or cut off, adding the additional reactive power instruction to an original reactive power instruction of the STATCOM coordination controller in real time to obtain a target reactive power instruction of the STATCOM coordination controller.
In a preferred embodiment, the first preset time period is determined according to a transient voltage time period of the ac bus of the dc converter station after the ac filter bank is switched on or off. Preferably, the first preset time period is 0.15s to 0.2 s.
It should be noted that, the apparatus for reducing fluctuation of bus voltage in the switching process of the ac filter bank provided in the embodiment of the present invention is used to execute all the process steps of the method for reducing fluctuation of bus voltage in the switching process of the ac filter bank in the above embodiment, and the working principles and beneficial effects of the two are in one-to-one correspondence, and thus are not described again.
It will be understood by those skilled in the art that all or part of the processes of the methods of the embodiments described above can be implemented by a computer program, which can be stored in a computer-readable storage medium, and when executed, can include the processes of the embodiments of the methods described above. The storage medium may be a magnetic disk, an optical disk, a Read-only memory (ROM), a Random Access Memory (RAM), or the like.
The second embodiment of the invention provides a device for reducing the voltage fluctuation of a bus in the switching process of an alternating current filter bank, and a switching control signal detection module detects whether a direct current converter station control system sends an input control signal or a cut-off control signal of the alternating current filter bank in real time. And after the AC filter bank is actually put into or cut off, the AC bus voltage measuring module measures the effective value of the AC bus voltage of the DC convertor station in real time. And the additional reactive power instruction generating module calculates the change rate of the effective value of the alternating-current bus voltage in real time according to the effective value of the alternating-current bus voltage so as to generate a corresponding additional reactive power instruction. And the target reactive power instruction generating module attaches the additional reactive power instruction to an original reactive power instruction of the STATCOM coordination controller to obtain a target reactive power instruction of the STATCOM coordination controller. And the reactive power compensation module performs reactive power compensation according to the target reactive power instruction. According to the embodiment of the invention, after the input control signal or the cut-off control signal of the alternating current filter bank is detected, the corresponding additional reactive power instruction is generated in real time according to the change rate of the alternating current bus voltage, so that the STATCOM can absorb or inject reactive power with a certain capacity in the reverse direction on the basis of the original reactive power output, the reactive power variation of the alternating current network at the moment after the switching of the alternating current filter bank is reduced, the fluctuation amplitude of the alternating current bus voltage at the moment after the input or the cut-off of the alternating current filter bank is reduced, and the voltage stress problem of the converter station bus in the input or the cut-off process of the alternating current filter bank is effectively inhibited. Meanwhile, the embodiment of the invention does not influence the steady-state voltage level of the alternating current bus before the alternating current filter bank is put into or cut off, and the original design setting value of the STATCOM is not required to be changed.
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 (10)
1. A method for reducing bus voltage fluctuation in the switching process of an alternating current filter bank is characterized by comprising the following steps:
detecting whether a control system of the direct current converter station sends an input control signal or a cut-off control signal of an alternating current filter bank in real time;
when detecting that the input control signal or the cut-off control signal of the alternating current filter bank is sent by the direct current converter station control system, determining the real input or cut-off moment of the alternating current filter bank, and measuring the effective value of the alternating current bus voltage of the direct current converter station in real time after the alternating current filter bank is really input or cut off;
calculating the change rate of the effective value of the alternating-current bus voltage in real time according to the effective value of the alternating-current bus voltage to generate a corresponding additional reactive power instruction;
adding the additional reactive power instruction to an original reactive power instruction of a STATCOM coordinated controller to obtain a target reactive power instruction of the STATCOM coordinated controller;
and performing reactive power compensation according to the target reactive power instruction.
2. The method for reducing bus voltage fluctuation during switching of the ac filter bank according to claim 1, wherein the step of calculating a variation rate of the effective value of the ac bus voltage in real time according to the effective value of the ac bus voltage to generate a corresponding additional reactive power command specifically comprises:
filtering the effective value of the alternating-current bus voltage through a low-pass filter;
inputting the filtered effective value of the alternating-current bus voltage into a differential hysteresis link, and calculating the differential quantity of the alternating-current bus voltage to obtain the change rate of the effective value of the alternating-current bus voltage;
and inputting the differential quantity of the alternating-current bus voltage into an inverting proportional link for correction so as to generate the additional reactive power instruction.
3. The method for reducing the bus voltage fluctuation during the switching process of the ac filter bank according to claim 1, wherein the adding of the additional reactive power instruction to the original reactive power instruction of the STATCOM coordinated controller to obtain the target reactive power instruction of the STATCOM coordinated controller is specifically:
and in a first preset time after the AC filter bank is really put into or cut off, adding the additional reactive power instruction to an original reactive power instruction of the STATCOM coordination controller in real time to obtain a target reactive power instruction of the STATCOM coordination controller.
4. The method for reducing the voltage fluctuation of the alternating current filter bank switching process bus bar according to claim 3, wherein the first preset time period is determined according to a transient voltage time period of the alternating current bus bar after the alternating current filter bank is switched on or switched off by the direct current converter station.
5. The method for reducing bus voltage fluctuation during switching of the alternating current filter bank as claimed in claim 3, wherein the first preset time period is 0.15 s-0.2 s.
6. The utility model provides a reduce device that alternating current filter bank switching process bus voltage fluctuates which characterized in that includes:
the switching control signal detection module is used for detecting whether the control system of the direct current converter station sends an input control signal or a cut-off control signal of the alternating current filter bank or not in real time;
the alternating current bus voltage measuring module is used for determining the real switching-in or switching-out moment of the alternating current filter bank when detecting that the switching-in control signal or the switching-out control signal of the alternating current filter bank is sent by the direct current converter station control system, and measuring the effective value of the alternating current bus voltage of the direct current converter station in real time after the alternating current filter bank is really switched in or switched out;
the additional reactive power instruction generating module is used for calculating the change rate of the effective value of the alternating-current bus voltage in real time according to the effective value of the alternating-current bus voltage so as to generate a corresponding additional reactive power instruction;
the target reactive power instruction generation module is used for adding the additional reactive power instruction to an original reactive power instruction of the STATCOM coordination controller so as to obtain a target reactive power instruction of the STATCOM coordination controller;
and the reactive power compensation module is used for performing reactive power compensation according to the target reactive power instruction.
7. The apparatus for reducing bus voltage ripple during switching of an ac filter bank as recited in claim 6, wherein said additional reactive power command generation module is specifically configured to:
filtering the effective value of the alternating-current bus voltage through a low-pass filter;
inputting the filtered effective value of the alternating-current bus voltage into a differential hysteresis link, and calculating the differential quantity of the alternating-current bus voltage to obtain the change rate of the effective value of the alternating-current bus voltage;
and inputting the differential quantity of the alternating-current bus voltage into an inverting proportional link for correction so as to generate the additional reactive power instruction.
8. The apparatus for reducing bus voltage ripple during ac filter bank switching according to claim 6, wherein the target reactive power command generation module is specifically configured to:
and in a first preset time after the AC filter bank is really put into or cut off, adding the additional reactive power instruction to an original reactive power instruction of the STATCOM coordination controller in real time to obtain a target reactive power instruction of the STATCOM coordination controller.
9. The apparatus for reducing the bus voltage ripple during the switching process of the ac filter bank according to claim 8, wherein the first predetermined period is determined according to a transient voltage period of the ac bus after the ac filter bank is switched on or off by the dc converter station.
10. The apparatus for reducing bus voltage ripple during switching of ac filter bank according to claim 9, wherein the first predetermined time period is 0.15s to 0.2 s.
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