CN107154637B - Control device and method applied to three-phase unbalance adjustment - Google Patents
Control device and method applied to three-phase unbalance adjustment Download PDFInfo
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- CN107154637B CN107154637B CN201710579548.XA CN201710579548A CN107154637B CN 107154637 B CN107154637 B CN 107154637B CN 201710579548 A CN201710579548 A CN 201710579548A CN 107154637 B CN107154637 B CN 107154637B
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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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- 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 application relates to a control device and a method for adjusting three-phase unbalance, in particular to a control device for adjusting three-phase unbalance, comprising an active SVG module compensation circuit and a 3-path capacitance adjusting circuit; the control method comprises an active SVG module compensation: according to the three-phase unbalanced current, the active SVG module compensation circuit compensates the unbalanced current. And (3) two passive phase-to-phase capacitance adjustment: according to the size of the three-phase unbalanced current and the size of the active current transferred by the inter-phase capacitor, carrying out capacitance adjustment on the three-phase unbalanced current; the three active SVG modules again compensate: and if the second phase-to-phase capacitor switching action exists, calculating unbalanced current after phase-to-phase capacitor adjustment, and compensating residual fundamental wave unbalance by the active SVG module. The application can accurately detect the three-phase unbalanced current, accurately adjust the three-phase unbalance in a large range and improve the power factor.
Description
Technical Field
The application relates to the field of three-phase imbalance treatment, in particular to a control device and a control method for adjusting three-phase imbalance.
Background
At present, in urban and rural power distribution networks, due to the fact that a large number of single-phase loads exist and the early planning of a power grid is incomplete, the problem of serious three-phase active current imbalance exists. Meanwhile, the unbalance phenomenon can be caused by unbalanced load of a three-phase power supply, and can also be caused by that certain large-scale three-phase equipment is operated under unbalanced power grid conditions, such as serious unbalance of the power grid caused by arc welding equipment in industry and the like. Three-phase imbalance causes a number of drawbacks: (1) The problems of overlarge zero line current, serious heating, low utilization efficiency of electrical equipment such as circuits, transformers and the like are caused; (2) The transformer power factor is low due to the inductive load. The improvement of the electric energy quality and the reduction of the energy consumption have become the consensus of all industries of national and industrial economy, and the passive capacitance adjusting device is available on the market at present, but mainly takes reactive compensation as a main part and has limited unbalanced adjusting capability. Therefore, there is a necessary trend in developing a three-phase unbalance automatic adjustment device that can compensate for the unbalanced load.
Currently, for three-phase imbalance compensation, the following three types of existing technologies exist:
the first prior art is: the static var generator SVG for restraining unbalanced load and a control method thereof disclosed in patent document with publication number of CN103475004A adopt a three-phase four-bridge arm inverter, an active current, a reactive current and a zero sequence compensation current of a system are calculated through Clarke and Park conversion by using a current detection method based on an instantaneous reactive theory, a command current is calculated, and the required compensation unbalanced current is output through the inverter.
And the second prior art is as follows: the patent document with publication number of CN105811441A discloses a device and a method for controlling three-phase unbalance and reactive power of an interphase capacitor, which adopts interphase capacitors and phase zero capacitors to control unbalance of a three-phase power grid, and the method adopts pure capacitance adjustment to solve the problems that the accuracy is high, the unbalance degree cannot be effectively adjusted to be within 5 percent, and the compensation response time is slow.
The third prior art is: a three-phase unbalanced current compensation method and device for a low-voltage power network, disclosed in patent document with publication number CN105406494A, compensates negative sequence current by switching an inter-phase capacitor and compensates zero sequence current by an active power filter.
The existing schemes of three-phase unbalance compensation have certain disadvantages. Therefore, a hybrid three-phase imbalance compensation device is needed, which not only comprises a passive phase-to-phase capacitor, but also comprises an active module SVG, so that three-phase imbalance current can be accurately detected, low cost can be ensured, meanwhile, three-phase imbalance of a power distribution network can be adjusted in a large range, power factors can be improved, and precision can be ensured.
Disclosure of Invention
1. The technical problems to be solved are as follows:
aiming at the defects of the prior art, the application provides a control device and a control method for adjusting three-phase unbalance, which not only comprise passive interphase capacitors, but also comprise active SVG modules; the three-phase unbalanced current detection device can accurately detect three-phase unbalanced current, can ensure lower cost, can adjust three-phase unbalance of the power distribution network in a large range, can improve power factors, and can ensure accuracy.
2. The technical scheme is as follows:
a control device for adjusting three-phase imbalance comprises an active SVG module compensation circuit and a 3-path capacitance adjusting circuit; the active SVG module compensation circuit is electrically connected with the three phases; the capacitance adjusting circuit is electrically connected with the three phases;
each path of capacitance adjusting circuit comprises three interphase capacitances, a triangular connection method is arranged among the three interphase capacitances, and the connection points of the triangular connection method are respectively connected with one phase of three-phase electricity; each interphase capacitor is connected with one split-phase thyristor in series and then connected in a triangular mode.
Further, the active SVG module compensation circuit comprises an active SVG module and a fuse; the active SVG module is electrically connected with the three phases through a fuse.
A control method for adjusting three-phase imbalance comprises the following steps
Step one, active SVG module compensation: and according to the extracted three-phase unbalanced current, the active SVG module compensation circuit responds first to compensate the unbalanced current. The extraction current value is automatically extracted by the system.
Step two, passive phase-to-phase capacitance adjustment: extracting the obtained three-phase unbalanced current, and if the three-phase unbalanced current is larger than the size of the phase-to-phase capacitance transfer active current, performing capacitance adjustment on the three-phase unbalanced current so as to adjust the active unbalance of the current; and if the compensated current is not greater than the active current transferred by the interphase capacitor, finishing the adjustment.
Step three, the active SVG module compensates again: and if the second phase-to-phase capacitor switching action exists, calculating unbalanced current after phase-to-phase capacitor adjustment, and compensating residual fundamental wave unbalance by the active SVG module.
Further, in the second step, the capacitance adjusting method includes:
according to Fourier decomposition, load i La (t),i Lb (t),i Lc (t) expressed in the form:
wherein the method comprises the steps of
When n=1, the fundamental active current direct current in the load current is:
according to the direct current of the three-phase active current, the magnitude of the active unbalanced current between each two phases of AB, BC and CA of the three-phase current is calculated to be I PAB 、I PBC 、I PCA ；
Calculating to obtain capacitance current according to rated capacity, rated voltage and grid voltage of the interphase capacitance;
calculating the size of the capacitance transfer active current by adopting a vector analysis method: when AB phase is connected with a single-phase capacitor, A phase reduces active current I AP Phase B increases active power I BP The method comprises the steps of carrying out a first treatment on the surface of the When BC is connected into the single-phase capacitor, B phase reduces the active current I BP Phase C increases the active current I CP The method comprises the steps of carrying out a first treatment on the surface of the When CA phase is connected with a single-phase capacitor, C phase reduces active current I CP Phase a increases active current I AP ；
By setting the switching threshold Ith of the split-phase thyristor connected in series with each capacitor, according to the magnitude IPAB, IPBC, IPCA of the active unbalanced current among AB, BC and CA, and the switching threshold Ith, if the unbalanced current is undercompensated or overcompensated, the corresponding capacitor is controlled to be circularly thrown or cut off, so that the process of regulating the three-phase active unbalanced current by the inter-phase capacitor is realized.
Further, the value of the switching threshold Ith is the corresponding active current plus a certain margin.
3. The beneficial effects are that:
the application not only has the response to the three-phase unbalanced current by the active SVG module, but also transfers the active current by the interphase capacitor, adjusts the three-phase unbalanced current, and finally compensates the residual fundamental wave unbalanced current by the active SVG module, thereby realizing the mixed three-phase unbalanced compensation. The scheme can effectively avoid the problems of small capacity of the active module, high cost, slow response of the reactive module and low precision.
And secondly, after the three-phase unbalance is regulated through the capacitor, the rest three-phase negative sequence current and zero sequence current are compensated through the active SVG module, and the three-phase unbalance is compensated.
And thirdly, the active component and the reactive component of the fundamental wave in the load current obtained by the three-phase current Fourier transformation are subjected to coordinate transformation respectively to obtain the fundamental wave zero sequence current and the fundamental wave negative sequence current, and the active module compensates the residual fundamental wave negative sequence current and the fundamental wave zero sequence current, so that the unbalanced compensation of the fundamental wave of the active module is realized.
Drawings
FIG. 1 is a schematic diagram of a control device for adjusting three-phase imbalance according to the present application;
FIG. 2 is a block diagram of a control method for adjusting three-phase imbalance according to the present application;
FIG. 3 is a vector diagram of the calculation of the capacitance transfer active current using vector analysis in the present application.
Detailed Description
FIG. 1 is a schematic diagram of a control device for adjusting three-phase imbalance according to the present application, where the device shown in FIG. 1 includes an active SVG module compensation circuit and a 3-way capacitance adjusting circuit; the active SVG module compensation circuit is electrically connected with the three phases; the capacitance adjusting circuit is electrically connected with the three phases; each path of capacitance adjusting circuit comprises three interphase capacitances, a triangular connection method is arranged among the three interphase capacitances, and the connection points of the triangular connection method are respectively connected with one phase of three-phase electricity; each interphase capacitor is connected with one split-phase thyristor in series and then connected in a triangular mode. Each split-phase thyristor controls the input or the cut-off of a capacitor connected in series with the thyristor in a split-phase manner, so that the unbalanced three-phase active current is passively regulated; the A-SVG is an active SVG module, and the effect of actively compensating unbalanced current is realized. The active SVG module compensation circuit responds to the three-phase unbalanced current according to the extracted three-phase unbalanced current, and compensates the unbalanced current. The capacitance adjusting circuit extracts the obtained three-phase unbalanced current, and if the three-phase unbalanced current is larger than the size of the active current transferred by the inter-phase capacitance, the capacitance adjustment is carried out on the three-phase unbalanced current, so that the active unbalance of the current is adjusted; and if the compensated current is not greater than the active current transferred by the interphase capacitor, finishing the adjustment.
As shown in fig. 2. It can be seen from the figure that when the three-phase unbalanced load increases, the active SVG module responds first to compensate the current unbalance; if the three-phase unbalanced current in the load is larger than the transferred active current of the interphase capacitor, the phase-splitting thyristor is used for controlling the input interphase capacitor to adjust so as to perform active unbalanced adjustment; finally, the active SVG module compensates for the remaining fundamental imbalance current.
Fig. 3 is a vector diagram of the calculation of the capacitance transfer active current by using the vector analysis method in the application. Wherein, two ends of the capacitor C are respectively and electrically connected with the AB two phases of the three-phase power supply, and the phase A reduces the active current I as can be seen from the figure AP Phase B increases active power I BP 。
While the application has been described with reference to the preferred embodiments, 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 application, and it is intended that the scope of the application shall be defined by the appended claims.
Claims (2)
1. A control device for adjusting three-phase imbalance, characterized in that: the active SVG module compensation circuit and the 3-path capacitance adjusting circuit are included; the active SVG module compensation circuit is electrically connected with the three phases; the capacitance adjusting circuit is electrically connected with the three phases;
each circuit of capacitance adjusting circuit comprises three interphase capacitances, a triangle connection method is arranged among the three interphase capacitances, and the connection points of the triangle connection method are respectively connected with one phase of three-phase power;
each interphase capacitor is connected with one split-phase thyristor in series and then connected in a triangular mode;
the active SVG module compensation circuit comprises an active SVG module and a fuse; the active SVG module is electrically connected with the three phases through a fuse;
a control method for adjusting three-phase imbalance, comprising the steps of:
step one, active SVG module compensation: according to the extracted three-phase unbalanced current, an active SVG module compensation circuit responds first to compensate the unbalanced current;
step two, passive phase-to-phase capacitance adjustment: if the three-phase unbalanced current is larger than the transferred active current of the interphase capacitor, carrying out capacitance adjustment on the three-phase unbalanced current so as to adjust the active unbalance of the current; if the compensated current is not greater than the active current transferred by the interphase capacitor, finishing the adjustment;
step three, the active SVG module compensates again: if the second step has no inter-phase capacitor switching action, the active SVG module keeps the first step, if the second step has the inter-phase capacitor switching action, unbalanced current after inter-phase capacitor adjustment is calculated, and the active SVG module compensates residual fundamental unbalanced current;
the capacitance adjusting method in the second step specifically comprises the following steps:
according to Fourier decomposition, load i La (t),i Lb (t),i Lc (t) expressed in the form:
wherein the method comprises the steps of
When n=1, the fundamental active current direct current in the load current is:
according to the direct current of the three-phase active current, the magnitude of the active unbalanced current between each two phases of AB, BC and CA of the three-phase current is calculated to be I PAB 、I PBC 、I PCA ；
Calculating to obtain capacitance current according to rated capacity, rated voltage and grid voltage of the interphase capacitance;
calculating the size of the capacitance transfer active current by adopting a vector analysis method: when AB phase is connected with a single-phase capacitor, A phase reduces active current I AP Phase B increases the active current I BP The method comprises the steps of carrying out a first treatment on the surface of the When BC is connected into the single-phase capacitor, B phase reduces the active current I BP Phase C increases the active current I CP The method comprises the steps of carrying out a first treatment on the surface of the When CA phase is connected with a single-phase capacitor, C phase reduces active current I CP Phase a increases active current I AP ；
By setting the switching threshold Ith of the split-phase thyristors connected in series with each capacitor, the current I is unbalanced according to the active power among AB, BC and CA PAB 、I PBC 、I PCA And a switching threshold Ith; if the unbalanced current is not compensated or is compensated excessively, the corresponding capacitor is controlled to be put into or cut off, and the process of adjusting the three-phase active unbalance by the interphase capacitor is realized.
2. A control device for adjusting three-phase imbalance according to claim 1, characterized in that: the value of the switching threshold Ith is the corresponding active current plus a certain margin.
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| CN201710579548.XA CN107154637B (en) | 2017-07-17 | 2017-07-17 | Control device and method applied to three-phase unbalance adjustment |
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| CN201710579548.XA CN107154637B (en) | 2017-07-17 | 2017-07-17 | Control device and method applied to three-phase unbalance adjustment |
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN201584790U (en) * | 2009-12-28 | 2010-09-15 | 苏州工业园区和顺电气股份有限公司 | Low-voltage dynamic reactive power compensation device |
| CN205986164U (en) * | 2016-07-27 | 2017-02-22 | 河南隆鑫电力设备有限公司 | Balanced compensation arrangement of intelligence |
| CN207320843U (en) * | 2017-07-17 | 2018-05-04 | 南京亚派科技股份有限公司 | A kind of control device for being applied to adjust three-phase imbalance |
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- 2017-07-17 CN CN201710579548.XA patent/CN107154637B/en active Active
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN201584790U (en) * | 2009-12-28 | 2010-09-15 | 苏州工业园区和顺电气股份有限公司 | Low-voltage dynamic reactive power compensation device |
| CN205986164U (en) * | 2016-07-27 | 2017-02-22 | 河南隆鑫电力设备有限公司 | Balanced compensation arrangement of intelligence |
| CN207320843U (en) * | 2017-07-17 | 2018-05-04 | 南京亚派科技股份有限公司 | A kind of control device for being applied to adjust three-phase imbalance |
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