CN109301847B - Correction method of capacitor unbalanced current and filter protection device - Google Patents
Correction method of capacitor unbalanced current and filter protection device Download PDFInfo
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- CN109301847B CN109301847B CN201811223951.XA CN201811223951A CN109301847B CN 109301847 B CN109301847 B CN 109301847B CN 201811223951 A CN201811223951 A CN 201811223951A CN 109301847 B CN109301847 B CN 109301847B
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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
- H02J3/26—Arrangements for eliminating or reducing asymmetry in polyphase networks
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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
- H02J3/01—Arrangements for reducing harmonics or ripples
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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
- Y02E40/40—Arrangements for reducing harmonics
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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
- Y02E40/50—Arrangements for eliminating or reducing asymmetry in polyphase networks
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Abstract
The invention relates to a method for correcting unbalanced current of a capacitor and a filter protection device, wherein the method comprises the following steps: selecting unbalanced currents needing to be corrected according to groups, if the tail ends of the groups of unbalanced currents have currents, calculating the magnitude of each phase current of the groups of unbalanced currents and the relative angle between each phase current of the tail ends, if any phase current of the groups of unbalanced currents is larger than the maximum correction fixed value, taking the phase current or the maximum correction fixed value of the groups of unbalanced currents as initial unbalanced currents, and taking the relative angle between the phase current and the phase current corresponding to the tail ends as the initial angle; and correcting each phase of unbalanced current actually acquired in the unbalanced protection of the filter according to the initial unbalanced current and the initial angle. The invention can realize the correction of the unbalanced current in the unbalanced protection of the filter without hard switching, effectively avoids the phenomenon of false operation of the protection of the alternating current filter and improves the reliability of the protection of the alternating current filter.
Description
Technical Field
The invention relates to a correction method of capacitor unbalanced current and a filter protection device, and belongs to the technical field of relay protection of power systems.
Background
The alternating current filter is an important component of the converter station and is used for filtering harmonic waves generated by the direct current control system so as to improve the quality of electric energy, and meanwhile, the alternating current filter can provide reactive power for the power system so as to improve the stability of the power system. In an ideal situation, the unbalanced current in the capacitor bank of the ac filter is 0, but due to the manufacturing process error and the influence of environmental factors, the current flowing through the unbalanced current transformer CT is not zero at the initial stage of the operation of the ac filter, which easily causes the malfunction of the protection of the ac filter.
Disclosure of Invention
The invention aims to provide a method for correcting unbalanced current of a capacitor and a filter protection device, which are used for solving the problem that the initial unbalanced current of the capacitor can cause misoperation of protection of an alternating current filter.
In order to solve the technical problem, the invention provides a method for correcting unbalanced current of a capacitor, which comprises the following steps:
selecting unbalanced currents to be corrected according to groups, wherein each group of unbalanced currents comprises A, B, C three phases;
calculating and judging whether the tail end corresponding to the group of unbalanced current has current or not according to the unbalanced current which is selected according to the group and needs to be corrected;
if the tail end has current, calculating the magnitude of each phase current of the set of unbalanced current and a relative angle between each phase current of the tail end and each phase current of the set of unbalanced current, and judging whether each phase current of the set of unbalanced current is larger than a maximum correction fixed value or not;
if any phase current of the set of unbalanced currents is larger than the maximum correction fixed value, regarding the phase current larger than the maximum correction fixed value in the set of unbalanced currents, taking the maximum correction fixed value as an initial unbalanced current, and taking a relative angle between the phase current and a phase current corresponding to the tail end as an initial angle; regarding the phase current which is not larger than the maximum correction fixed value in the set of unbalanced current, taking the unbalanced current as initial unbalanced current, and taking the relative angle between the phase current and the phase current corresponding to the tail end as an initial angle;
and correcting each phase of unbalanced current actually acquired in the unbalanced protection of the filter by adopting the initial unbalanced current and the initial angle.
The invention also provides a filter protection device, which comprises an interface processor and a protection processor, wherein the interface processor is used for: selecting unbalanced currents needing to be corrected according to groups and sending the unbalanced currents to a protection processor, wherein each group of unbalanced currents comprises A, B, C three phases; the protection processor is to: calculating and judging whether the tail end corresponding to the group of unbalanced current has current or not according to the unbalanced current which is selected according to the group and needs to be corrected; if the tail end has current, calculating the magnitude of each phase current of the set of unbalanced current and a relative angle between each phase current of the tail end and each phase current of the set of unbalanced current, and judging whether each phase current of the set of unbalanced current is larger than a maximum correction fixed value or not; if any phase current of the set of unbalanced currents is larger than the maximum correction fixed value, regarding the phase current larger than the maximum correction fixed value in the set of unbalanced currents, taking the maximum correction fixed value as an initial unbalanced current, and taking a relative angle between the phase current and a phase current corresponding to the tail end as an initial angle; regarding the phase current which is not larger than the maximum correction fixed value in the set of unbalanced current, taking the unbalanced current as initial unbalanced current, and taking the relative angle between the phase current and the phase current corresponding to the tail end as an initial angle; and correcting each phase of unbalanced current actually acquired in the unbalanced protection of the filter according to the initial unbalanced current and the initial angle.
The invention has the beneficial effects that: the method comprises the steps of selecting unbalanced current to be corrected as required, obtaining initial unbalanced current and an initial phase angle according to a comparison result between any phase current of the unbalanced current and a maximum correction fixed value when the tail end corresponding to the unbalanced current has current, correcting each phase of unbalanced current actually collected in unbalanced protection of a filter according to the initial unbalanced current and an initial angle when fault logic judgment in unbalanced protection of the filter is carried out, reflecting the unbalanced state of a capacitor bank in operation more truly, correcting the unbalanced current without hard entry, effectively avoiding the phenomenon of protection misoperation of an alternating current filter, and improving the reliability of protection of the alternating current filter.
As a further improvement of the method and the apparatus, in order to effectively correct each phase of unbalanced current actually collected in the filter unbalanced protection, the step of correcting each phase of unbalanced current actually collected in the filter unbalanced protection by using the initial unbalanced current and the initial angle is as follows:
if the angle between the actual unbalanced current and the tail end current is positive relative to the initial angle, the corrected unbalanced current amplitude is the actual unbalanced current minus the initial unbalanced current; otherwise, the corrected magnitude of the unbalanced current is the sum of the actual unbalanced current and the initial unbalanced current.
As a further improvement of the method and the device, in order to realize the correction of each phase of unbalanced current actually collected in the unbalanced protection of the filter when the three-phase unbalanced current is not greater than the maximum correction fixed value, if the three-phase current of the group of unbalanced currents is not greater than the maximum correction fixed value, each phase of unbalanced current is taken as an initial unbalanced current, and the angle of each phase of unbalanced current relative to each phase current at the tail end is taken as an initial angle.
As a further improvement of the method and the device, in order to accurately judge whether the current exists at the tail end, the judgment condition that the current exists at the tail end is as follows:
ita > kIn and Itb > kIn and Itc > kIn
Wherein Ita, Itb and Itc are three-phase currents of A, B, C at the tail end respectively, In is the tail end rated current, and k is a coefficient.
As a further improvement of the method and apparatus, in order to improve the accuracy of the determination, the determination condition that the angle between the actual unbalanced current and the tail end current is positive with respect to the initial angle is as follows:
|θ-θ0< α or theta-theta0|＞β
Wherein theta is the angle between the actual unbalanced current and the tail end current, theta0The initial angles α, β are sensitivity angles for discrimination.
Drawings
FIG. 1 is a flow chart of a method of correcting capacitor imbalance current in accordance with the present invention;
fig. 2 is a main wiring diagram of the double-tuned ac filter of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
The embodiment of the correction method of the capacitor unbalanced current comprises the following steps:
the embodiment provides a method for correcting unbalanced current of a capacitor, which can enable a user to correct the unbalanced current actually collected in the unbalanced protection of a filter on a man-machine interface of a filter protection device. The method is suitable for various types of alternating current filter protection devices such as a high-pass C-type alternating current filter, a double-tuning (high-pass) type alternating current filter, a capacitor bank type alternating current filter and the like, and a corresponding flow chart is shown in figure 1.
Fig. 2 shows a main wiring diagram of a double-tuned ac filter, in which the main wiring includes a head-end CT, a C1 unbalanced CT, a C2 unbalanced CT, a resistor CT, a reactor CT, and a tail-end CT. In conjunction with the main connection of the double-tuned ac filter in fig. 2, the method for correcting the unbalanced current of the capacitor specifically includes the following steps:
(1) the unbalance currents to be corrected are selected by groups, each group including A, B, C three phases.
Instead of correcting all the unbalanced currents, the user selects the unbalanced currents to be corrected in groups in the filter protection menu, which are targeted, each group of unbalanced currents comprising A, B, C three phases. In this embodiment, the user chooses to correct the unbalanced current of C1 in fig. 1.
(2) And calculating and judging whether the tail end corresponding to the group of unbalanced current has current or not according to the unbalanced current which is selected according to the group and needs to be corrected.
The user selects the current to be corrected and presses the determining button, the interface CPU (central processing unit), namely the interface processor, of the filter protection device automatically identifies the group number of the unbalanced current channel to be corrected selected by the user and transmits the group number to the protection CPU, namely the protection processor, and the protection CPU calculates and judges whether the tail end of the filter corresponding to the channel has the current. In this embodiment, the interface CPU of the double-tuned ac filter protection device recognizes the group number of the unbalanced current of C1 and transmits it to the protection CPU. Protecting the CPU to calculate the magnitude of the tail end current and judging whether the tail end has the current, wherein the judging condition that the tail end has the current is as follows:
ita > kIn and Itb > kIn and Itc > kIn
Wherein Ita, Itb and Itc are three-phase currents of A, B, C at the tail end respectively, In is the tail end rated current, k is a coefficient, and 0.04 is taken.
(3) If the tail end has current, the magnitude of each phase current of the set of unbalanced current and the relative angle of each phase current of the tail end are calculated, and whether each phase current of the set of unbalanced current is larger than the maximum correction fixed value or not is judged.
That is, if the determination condition that there is a current at the tail end is satisfied, the magnitude of the unbalanced current is determined. The protection CPU calculates the current magnitude of each phase of the group of unbalanced current and judges whether the magnitude of the unbalanced current exceeds a maximum correction fixed value (an unbalanced correction upper limit fixed value), and the judgment condition that the magnitude of the unbalanced current exceeds the maximum correction fixed value is as follows:
iu1a > Iu1set, Iu1b > Iu1set, and Iu1c > Iu1set
Wherein Iu1a, Iu1b, Iu1c are A, B, C three-phase unbalanced currents of the selected group, Iu1set is the maximum correction fixed value of the selected group, Iu1set can be set according to actual conditions during debugging, and the value is generally 0.05A.
In this embodiment, the protection CPU of the double-tuned ac filter protection device calculates the magnitude of the unbalanced C1 current in each phase and the angle between the unbalanced C1 current and the phase current in each phase at the tail end, and determines whether the unbalanced C1 current in each phase is greater than the maximum correction value.
In addition, in step (3), if there is no current at the tail end corresponding to the set of unbalanced currents, feeding back a tail end no-current mark to the interface CPU, and prompting the user of a failure in correction through a pop-up dialog box on the panel of the filter protection device.
(4) If any phase current of the set of unbalanced currents is larger than the maximum correction fixed value, regarding the phase current larger than the maximum correction fixed value in the set of unbalanced currents, taking the maximum correction fixed value as an initial unbalanced current, and taking a relative angle between the phase current and a phase current corresponding to the tail end as an initial angle; for the phase current in the set of unbalanced currents not greater than the maximum correction constant, the unbalanced current is taken as the initial unbalanced current, and the relative angle of the phase current and the tail end corresponding phase current is taken as the initial angle.
Specifically, if any one of the phase unbalanced currents is larger than a maximum correction fixed value, which is a correctable maximum current set by a user, in order to confirm the correction step, the protection CPU of the filter protection apparatus prompts the user whether to confirm correction of the group of unbalanced currents, in order to prompt the user to check whether the capacitor group is in an abnormal operation state, and to prevent correction of the capacitor unbalanced current in the abnormal operation state. After the user operation is determined, the filter protection device writes the current which is not larger than the maximum correction fixed value in the group of unbalanced currents and the relative angle between the current and the tail end current into the power-down loss-free area, and writes the maximum correction fixed value and the relative angle between the current and the tail end current into the power-down loss-free area as the initial unbalanced current for correcting the unbalanced current for the phases which are larger than the maximum correction fixed value.
And if the set of unbalanced current phase currents are not larger than the maximum correction fixed value, storing the set of unbalanced current phase currents and the relative angle of the set of unbalanced current phase currents and the tail end phase currents as initial unbalanced currents. That is, when the three-phase unbalanced current is not greater than the maximum correction fixed value, the unbalanced current and the relative angle with the tail end current at that time are written into the power-down loss-free area by the filter protection device and serve as the initial unbalanced current to correct the unbalanced current.
(5) And correcting each phase of unbalanced current actually acquired in the unbalanced protection of the filter according to the initial unbalanced current and the initial angle.
According to two conditions of comparison between three-phase unbalanced current and a maximum correction fixed value, when the unbalanced current is stored, the initial unbalanced current and the angle of the initial unbalanced current relative to the tail end current are stored, the protection device corrects the unbalanced current according to the stored initial unbalanced current and the initial angle, and the current used by fault logic judgment is the corrected unbalanced current, so that the unbalanced state of the capacitor bank during operation is reflected more truly. And the data can not be lost after the filter protection device is powered off, so that the correction effectiveness is ensured.
The step of correcting each phase of unbalanced current actually collected in the unbalanced protection of the filter according to the initial unbalanced current and the initial angle is as follows:
if the angle between the actual unbalanced current and the tail end current is positive relative to the initial angle, the corrected unbalanced current amplitude is the actual unbalanced current minus the initial unbalanced current; otherwise, the corrected magnitude of the unbalanced current is the sum of the actual unbalanced current and the initial unbalanced current.
Specifically, the angle between the actual unbalanced current and the tail end current is a positive judgment condition relative to the initial angle:
|θ-θ0< α or theta-theta0|＞β
Wherein theta is the angle between the actual unbalanced current and the tail end current, theta0The initial angles α and β are sensitive angles for discrimination, and in the present embodiment, α is 90 °, and β is β270°。
Of course, as another embodiment, if there is no tail current in step (3), and the unbalanced current and the relative angle to the tail current are not calculated, there is no need to write the unbalanced current and the relative angle to the tail current into the power-down non-loss area in step (4).
After the correction is completed, the protection CPU of the filter protection device pops up a dialog box for successful correction of the unbalanced current through the control panel, and feeds back information of successful correction of the unbalanced current to a user.
In the normal operation process of the filter, when unbalanced current occurs, the filter protection device obtains current used for protection logic judgment by adding or subtracting the initial unbalanced current according to the condition that the angle between the actually acquired unbalanced current and the tail end current is relative to the initial angle, and the phenomenon of misoperation is avoided. Since the protection of the filter protection device according to the unbalanced current belongs to the prior art, the details are not described herein.
The method for correcting the unbalanced current of the capacitor can enable a user to flexibly select the unbalanced current to be corrected, can intelligently calculate the magnitude of the tail end current corresponding to the unbalanced current, prompts the user whether to determine correction when the unbalanced current is too large, and finally feeds back information about whether the correction is successful or not to the user. The correction method of the unbalanced current of the capacitor can realize the selection and correction of the unbalanced current on the panel of the filter protection device, the input amount of the protection device is not required to be increased, the operation is more flexible and convenient, the wiring can be reduced, the cost is reduced, the board card resource is saved, the workload of design can be reduced, the unbalanced current can be selected according to groups when the correction is selected, only the channel to be corrected is corrected, the correction method is more flexible, and the phenomenon of protection misoperation of the alternating current filter is effectively avoided.
Filter protection device embodiment:
the embodiment provides a filter protection device, which comprises an interface processor and a protection processor, wherein the interface processor and the protection processor are matched with each other to realize the correction method of the unbalanced current of the capacitor. Since the process of the interface processor and the protection processor cooperating with each other has been described in detail in the above embodiment of the method for correcting the unbalanced current of the capacitor, it is not described herein again.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the protection scope thereof, and although the present application is described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: after reading this application, those skilled in the art will be able to make various changes, modifications and equivalents to the embodiments of the application, which are within the scope of the claims of this application.
Claims (10)
1. A method for correcting unbalanced current of a capacitor is characterized by comprising the following steps:
selecting unbalanced currents to be corrected according to groups, wherein each group of unbalanced currents comprises A, B, C three phases;
calculating and judging whether the tail end corresponding to the group of unbalanced current has current or not according to the unbalanced current which is selected according to the group and needs to be corrected;
if the tail end has current, calculating the magnitude of each phase current of the set of unbalanced current and a relative angle between each phase current of the tail end and each phase current of the set of unbalanced current, and judging whether each phase current of the set of unbalanced current is larger than a maximum correction fixed value or not;
if any phase current of the set of unbalanced currents is larger than the maximum correction fixed value, checking whether the capacitor bank is in an abnormal operation state, if the capacitor bank is not in the abnormal operation state, regarding the phase current larger than the maximum correction fixed value in the set of unbalanced currents, taking the maximum correction fixed value as an initial unbalanced current, and taking a relative angle between the phase current and a phase current corresponding to the tail end as an initial angle; regarding the phase current which is not larger than the maximum correction fixed value in the set of unbalanced current, taking the unbalanced current as initial unbalanced current, and taking the relative angle between the phase current and the phase current corresponding to the tail end as an initial angle;
and correcting each phase of unbalanced current actually acquired in the unbalanced protection of the filter according to the initial unbalanced current and the initial angle.
2. The method for correcting unbalanced current of a capacitor according to claim 1, wherein the step of correcting the unbalanced current of each phase actually collected in the unbalanced protection of the filter by using the initial unbalanced current and the initial angle is as follows:
if the angle between the actual unbalanced current and the tail end current is positive relative to the initial angle, the corrected unbalanced current amplitude is the actual unbalanced current minus the initial unbalanced current; otherwise, the corrected magnitude of the unbalanced current is the sum of the actual unbalanced current and the initial unbalanced current.
3. The method for correcting the unbalanced current of the capacitor according to claim 1 or 2, wherein if none of the three-phase currents of the set of unbalanced currents is greater than a maximum correction fixed value, the unbalanced current of each phase is used as an initial unbalanced current, and an angle of the unbalanced current of each phase with respect to the current of the tail end phase is used as an initial angle.
4. The method for correcting unbalanced current of a capacitor according to claim 1 or 2, wherein the determination condition of the tail end current is as follows:
ita > kIn and Itb > kIn and Itc > kIn
Wherein Ita, Itb and Itc are three-phase currents of A, B, C at the tail end respectively, In is the tail end rated current, and k is a coefficient.
5. The method for correcting unbalanced current of a capacitor according to claim 2, wherein the condition for determining that the angle between the actual unbalanced current and the tail end current is positive with respect to the initial angle is as follows:
|θ-θ0< α or theta-theta0|＞β
Wherein theta is the angle between the actual unbalanced current and the tail end current, theta0The initial angles α, β are sensitivity angles for discrimination.
6. A filter protection device comprising an interface processor and a protection processor, the interface processor being configured to: selecting unbalanced currents needing to be corrected according to groups and sending the unbalanced currents to a protection processor, wherein each group of unbalanced currents comprises A, B, C three phases; the protection processor is to: calculating and judging whether the tail end corresponding to the group of unbalanced current has current or not according to the unbalanced current which is selected according to the group and needs to be corrected; if the tail end has current, calculating the magnitude of each phase current of the set of unbalanced current and a relative angle between each phase current of the tail end and each phase current of the set of unbalanced current, and judging whether each phase current of the set of unbalanced current is larger than a maximum correction fixed value or not; if any phase current of the set of unbalanced currents is larger than the maximum correction fixed value, checking whether the capacitor bank is in an abnormal operation state, if the capacitor bank is not in the abnormal operation state, regarding the phase current larger than the maximum correction fixed value in the set of unbalanced currents, taking the maximum correction fixed value as an initial unbalanced current, and taking a relative angle between the phase current and a phase current corresponding to the tail end as an initial angle; regarding the phase current which is not larger than the maximum correction fixed value in the set of unbalanced current, taking the unbalanced current as initial unbalanced current, and taking the relative angle between the phase current and the phase current corresponding to the tail end as an initial angle; and correcting each phase of unbalanced current actually acquired in the unbalanced protection of the filter according to the initial unbalanced current and the initial angle.
7. The filter protection device of claim 6, wherein the step of correcting each phase unbalanced current actually collected in the filter unbalanced protection by using the initial unbalanced current and the initial angle is as follows:
if the angle between the actual unbalanced current and the tail end current is positive relative to the initial angle, the corrected unbalanced current amplitude is the actual unbalanced current minus the initial unbalanced current; otherwise, the corrected magnitude of the unbalanced current is the sum of the actual unbalanced current and the initial unbalanced current.
8. The filter protection device according to claim 6 or 7, wherein if the set of unbalanced current three-phase currents are not greater than a maximum correction fixed value, the unbalanced current of each phase is used as an initial unbalanced current, and an angle of the unbalanced current of each phase relative to the current of each phase at the tail end is used as an initial angle.
9. The filter protection device according to claim 6 or 7, wherein the current at the tail end is determined by:
ita > kIn and Itb > kIn and Itc > kIn
Wherein Ita, Itb and Itc are three-phase currents of A, B, C at the tail end respectively, In is the tail end rated current, and k is a coefficient.
10. The filter protection device of claim 7, wherein the criterion that the angle of the actual unbalance current and the tail end current is positive with respect to the initial angle is as follows:
|θ-θ0< α or theta-theta0|＞β
Wherein theta is the angle between the actual unbalanced current and the tail end current, theta0The initial angles α, β are sensitivity angles for discrimination.
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| RU2553276C2 (en) * | 2011-02-16 | 2015-06-10 | Абб Рисерч Лтд | Method and configuration for detection of internal malfunction in bank of capacitors connected by n bridge |
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