WO2014063666A2 - Method of controlling an apparatus compensating ground fault currents for compensating for fault currents in an n-phase distribution system - Google Patents

Method of controlling an apparatus compensating ground fault currents for compensating for fault currents in an n-phase distribution system Download PDF

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Publication number
WO2014063666A2
WO2014063666A2 PCT/CZ2013/000068 CZ2013000068W WO2014063666A2 WO 2014063666 A2 WO2014063666 A2 WO 2014063666A2 CZ 2013000068 W CZ2013000068 W CZ 2013000068W WO 2014063666 A2 WO2014063666 A2 WO 2014063666A2
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Prior art keywords
phase
current
currents
ground fault
compensating
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PCT/CZ2013/000068
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French (fr)
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WO2014063666A3 (en
Inventor
Ivan Matuljak
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Ege, Spol. S R.O.
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Priority to EP13731266.6A priority Critical patent/EP2912739A2/en
Publication of WO2014063666A2 publication Critical patent/WO2014063666A2/en
Publication of WO2014063666A3 publication Critical patent/WO2014063666A3/en

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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
    • H02H9/08—Limitation or suppression of earth fault currents, e.g. Petersen coil
    • 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
    • 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
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381—Dispersed generators
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/12—Arrangements for reducing harmonics from ac input or output
    • H02M1/123—Suppression of common mode voltage or current
    • 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

Definitions

  • the invention relates to the field of electrical engineering and energy, specifically a method of controlling an apparatus compensating ground fault currents for compensating for fault currents that occur as a result of ground faults in phases of power line of an electrical distribution system.
  • a ground continuously tuneable arc suppression coil (a "Petersen coil”) is used as a basic apparatus compensating ground fault currents, connected between the node of the transformer and the earth potential.
  • This arc suppression coil functions on the principle of resonance, and upon the occurrence of a ground fault it compensates for the fault current, while the active current is compensated for by an auxiliary device that injects a compensation current to the auxiliary coil of the arc suppression coil.
  • auxiliary device that injects a compensation current to the auxiliary coil of the arc suppression coil.
  • controlled current source formed by a power converter. It is connected between the phase conductors of the transformer of the distribution system and the earth potential.
  • the power converter functions as a compensator for fault currents and higher harmonic orders of fault currents. In a no-fault state of a distribution system, it serves to balance its phase imbalance and compensate for reactive power.
  • the controlled current source may be composed of single-phase power semiconductor converters or may be formed by a single multi-phase power semiconductor converter.
  • the controlled current source may also be e.g. a voltage inverter, power inverter, or frequency inverter.
  • Known apparatuses compensating ground fault currents operate in the presence of a single-phase earth fault principally the same in the sense that there is a corresponding compensation current generated against each vector component of a fault current l p .
  • the fault current l p consists mainly of parasitic capacitances and leads against the earth potential of a distribution system (line-to-earth impedance) and is given by the vector sum of the parasitic currents:
  • the ground fault current l p can be expressed as follows:
  • the apparatus compensating ground fault currents is controlled mechanically or automatically by a program in such a way that it generates the compensating current lo, which compensates for the individual vectors of the fault current l p , while against each vector of the fault current l p a counter-current I02, I03 is created, thus achieving three-phase compensation of the fault current l p , wherein the following applies:
  • a disadvantage of the known process of controlling apparatuses compensating ground fault currents lies in the fact that individual current sources of the apparatus compensating ground fault currents have high current loads resulting from the fact that they have to generate sufficiently large compensation currents loi , I02, I03 to compensate for each vector of the fault current l p .
  • the apparatus compensating ground fault currents, respectively its individual current sources, must then have the corresponding power dimensioning, which is naturally reflected in larger construction dimensions, greater overall weight, and at a higher cost of the apparatus compensating ground fault currents.
  • the task of the invention is therefore to find such a method of controlling the apparatus compensating ground fault currents, which would lead to a reduction in load current of individual current sources and which would permit the production and operation of small apparatuses compensating ground fault currents with less power requirements, less overall weight, and a lower cost of acquisition.
  • the solution of the task is achieved by creating a new method of controlling an apparatus compensating ground fault currents according to the submitted invention.
  • the apparatus compensating ground fault currents equipped with n-controlled current sources or formed by a single n-phase controlled current source is connected in the known method using n + 1 outputs between phase conductors of an n-phase distribution system. Its task is to generate the compensation current lo to compensate for the fault current l p occurring as a result of the single-phase earth faults, and injecting the compensation current l 0 to the phase of the affected earth fault.
  • the essence of the method for controlling the apparatus compensating ground fault currents according to the submitted invention consists in the idea that the total compensation current l 0 is generated as a vector sum of individual n compensating currents, generated by individual controlled current sources or individual phase outputs of the n-phase of the controlled current source.
  • the current amplitudes of these individual compensation currents show, in absolute value, a deviation of no more than 25% from the value of — l 0 /n, and the phase shifts of these individual n
  • compensation currents show a difference of their values of no more than 30 ° as opposed to the total compensation current lo phase-shift.
  • the apparatus compensating ground fault currents is controlled in such a way that the current amplitudes of individual compensating currents have the same size, their value being— of the amplitude of the total compensation current lo.
  • phase shifts of the compensation currents are also equal, and their value equals the value of the phase shift of the total compensation current.
  • the method of the submitted invention has the advantage in that the vector sum of the individual compensation currents set by the above-described parameters comprises the necessary total compensation current l 0 of the components generated at a lower current load of individual controlled current sources or individual phases of an n-phase controlled current source.
  • the reduction of current load of current sources enables the construction of apparatus compensating ground fault currents with smaller space requirements, less weight, lower power requirements and consumption, and last but not least, with lower cost of acquisition.
  • Figure 1 is a diagram of a three-phase distribution system with earth connection in the first phase and with the apparatus compensating ground fault currents containing three controlled current sources;
  • Figure 3 is a phasor diagram of voltages and currents of a three-phase power distribution system according to Figure 1 , showing the individual compensating currents generated by the known method, representing the present state of technology
  • Figure 4 is a phasor diagram of voltages and currents of a three-phase distribution system according to Figure 1 , showing phase shifts of the individual compensation currents ⁇ - ⁇ , ⁇ 2 , ⁇ 3 in the maximum angular tolerance with regard to ⁇ 0
  • Figure 5 is a diagram of the connection of an n-phase distribution system with ground connection in the first phase and with the apparatus compensating ground fault currents containing an n-phase current source. Examples of the preferred embodiments of the invention
  • Figure 1 shows a three-phase distribution system ⁇ with phase conductors l_i , l_ 2 , L 3 . Between the phase conductors l_i , L 2 , L 3 and the site with earth potential 5 the apparatus compensating ground fault currents 2 is connected containing three controlled current sources 3, 3 ' , 3_ ⁇ The first phase conductor Li of the distribution system 1 is affected by the ground fault 6, which causes fault current l p as the sum of parasitic currents in individual phases:
  • the apparatus compensating ground fault currents 2, using controlled current sources 3, 3_[, 3 ⁇ , generates a total compensation current l 0 against fault current l p formed by the vector sum of individual compensation currents loi , I02, I03 generated by the controlled current sources 3, 2 , 3 ⁇ .
  • the controlled current sources 3, 3J., 3 ⁇ are, in the specific example of implementation, created by controlled power converters. These also may be voltage inverters, current inverters, or frequency inverters.
  • the control of current sources 3, 3 , 3J_[ in terms of the regulation of current amplitudes and angles ⁇ 2 , ⁇ 3 of the phase shift is performed by a control system functioning on the basis of DSP microcontrollers and/or field-programmable gate array (FPGA).
  • Figure 2 shows an example of the most preferred method of controlling the apparatus compensating ground fault currents 2 to compensate for the fault current l p in the distribution system according to Figure 1.
  • the total compensation current l 0 is created as a vector sum of individual compensation currents Ioi , I02, I03 generated by individual controlled current sources 3, y_, 3_ ⁇ . Meanwhile, the values of the individual compensation currents I01 , I02, I03 are guided so that the current amplitudes of the individual compensation currents l 0 i , I02, I03 have the same size on the value of 1/3 of the amplitude of the total compensation current l 0 , namely:
  • Figure 2 is a phasor diagram of a 3-phase distribution system 1. according to Figure 1 , showing the voltages and currents in the complex (Gaussian) plane, where the x-axis (RE) shows the real part of the complex number and the y-axis (IM) shows the imaginary part of the complex number.
  • the voltage u-i may have a minimum value.
  • Figure 3 shows the course of the control of the apparatus compensating ground fault currents 2 in a distribution system 1, with ground fault 6 by the current i.e. known method, in which a corresponding compensation current is generated against each vector component of the fault current l p .
  • each controlled current source 3 , 3 ⁇ thus has an amplitude of size - ⁇ and corresponding phase shift ( ⁇ 2, ⁇ 3).
  • Figure 4 shows a further variant of the method of controlling the apparatus compensating ground fault currents 2 according to the invention, different from the variant depicted in Figure 2 and described above.
  • FIG. 5 illustrates another implementation of the invention. This is an n-phase distribution system ⁇ with ground fault 6, as in Figure 1 , but the apparatus compensating ground fault currents 2 here is comprised of an n-phase controlled current source 4 instead of three controlled current sources 3, y, 2T_.
  • the method of control of the n-phase controlled current source 4 is completely the same as the method of control of the apparatus compensating ground fault currents 2 with three controlled current sources 3, 2 , 3 ⁇ _ in the above-described examples, with the difference that the size of the amplitude of the individual compensation currents
  • the method of controlling the apparatus compensating ground fault currents according to the invention can be used to compensate for fault currents that occur as a result of ground faults in an n-phase distribution system.

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Abstract

The apparatus compensating ground fault currents (2) with controlled current sources (3, 3', 3") is, in the known method, connected between the phase conductors L1, L2, L3 of an n-phase distribution system (1 ) and site with earth potential (5). The essence of the new method of its control, according to the invention, lies in the fact that in the occurrence of a ground fault (6), the total compensation current (l0) is formed as a vector sum of individual (n) compensation currents (l01, I02, I03) of all controlled current sources (3, 3', 3"), while their current amplitudes show, in absolute value, a deviation of no more than 25% from the value of l0/n, and the angles (φ1, φ2, Φ3) of their phase shifts show a difference of value of no more than 30% against the angle (φ0) of the phase shift of the total compensation current (l0).

Description

Method of controlling an apparatus compensating ground fault currents for compensating for fault currents in an n-phase distribution system
Field of the invention
The invention relates to the field of electrical engineering and energy, specifically a method of controlling an apparatus compensating ground fault currents for compensating for fault currents that occur as a result of ground faults in phases of power line of an electrical distribution system.
Background of the invention
To compensate for fault currents that occur at the site of a ground fault of some phase of an n-phase distribution system (also called a "single-phase ground fault"), a ground continuously tuneable arc suppression coil (a "Petersen coil") is used as a basic apparatus compensating ground fault currents, connected between the node of the transformer and the earth potential. This arc suppression coil functions on the principle of resonance, and upon the occurrence of a ground fault it compensates for the fault current, while the active current is compensated for by an auxiliary device that injects a compensation current to the auxiliary coil of the arc suppression coil. To compensate for the phase unbalance of the distribution system, as well as to compensate for the harmonics and compensate for the reactive power, other additional devices are used.
According to document EP 1855 366 B1 , another known apparatus compensating ground fault currents and method of compensating for fault current is known, wherein an electric switch is switched on, manually or automatically, connecting the respective phase conductor with the ground fault by filter circuit, which is designed as a power converter and which is arranged between the phase conductor and the site with earth potential. The generated compensation current compensates at least for one frequency of the fault current, and can also compensate for the reactive current. In another document DE 10 2007006719A1 , a similar apparatus compensating ground fault currents is described as in EP 1855 366 B1 , with the difference that the filter circuit is designed as a multi-frequency filter circuit which operates at a single frequency as a suction circuit and at a different frequency as the latching circuit while blocking the fundamental frequency.
From document DE 10 2007 04 9667 B4 there is another apparatus compensating ground fault currents known similar to the apparatuses described in the two previous documents, which also mentions the integration of electronic switches directly into the filter circuit which is created as a power converter, and the filter circuit is also fitted with capacitors controlled by switches that develop a pulse DC voltage supplied to the phase conductor with ground fault. The device is designed to compensate for reactive power.
From document CZ 302920 B6 an apparatus compensating ground fault currents is known with controlled current source, formed by a power converter. It is connected between the phase conductors of the transformer of the distribution system and the earth potential. The power converter functions as a compensator for fault currents and higher harmonic orders of fault currents. In a no-fault state of a distribution system, it serves to balance its phase imbalance and compensate for reactive power. The controlled current source may be composed of single-phase power semiconductor converters or may be formed by a single multi-phase power semiconductor converter. The controlled current source may also be e.g. a voltage inverter, power inverter, or frequency inverter.
Known apparatuses compensating ground fault currents operate in the presence of a single-phase earth fault principally the same in the sense that there is a corresponding compensation current generated against each vector component of a fault current lp. For example, in a three-phase ground system in the occurrence of a single-phase ground fault (the connection of one phase conductor with a site with earth potential), the fault current lp consists mainly of parasitic capacitances and leads against the earth potential of a distribution system (line-to-earth impedance) and is given by the vector sum of the parasitic currents:
Figure imgf000004_0001
Figure imgf000004_0002
wherein:
Ip fault current
lpi , Ip2, Ip3 parasitic currents in individual phases
u-i , U2, U3 phase voltages (line-to-earth voltage) in individual phases
Zi , Z2, Z3 line-to-earth impedance in individual phases
In an ideal earth connection in a single-phase ground fault, the voltage ui at the affected phase is zero, and in the phases not affected by ground fault the voltages are on the associated value, so in an ideal single-phase ground fault the ground fault current lp can be expressed as follows:
h = +
p 7 7
In the compensation of a single-phase ground fault in the known method, the apparatus compensating ground fault currents is controlled mechanically or automatically by a program in such a way that it generates the compensating current lo, which compensates for the individual vectors of the fault current lp, while against each vector of the fault current lp a counter-current I02, I03 is created, thus achieving three-phase compensation of the fault current lp, wherein the following applies:
Figure imgf000005_0001
wherein:
I02, lo3 compensating currents generated against non-zero vectors of fault current lp l0 total compensation current
A disadvantage of the known process of controlling apparatuses compensating ground fault currents lies in the fact that individual current sources of the apparatus compensating ground fault currents have high current loads resulting from the fact that they have to generate sufficiently large compensation currents loi , I02, I03 to compensate for each vector of the fault current lp. The apparatus compensating ground fault currents, respectively its individual current sources, must then have the corresponding power dimensioning, which is naturally reflected in larger construction dimensions, greater overall weight, and at a higher cost of the apparatus compensating ground fault currents. The task of the invention is therefore to find such a method of controlling the apparatus compensating ground fault currents, which would lead to a reduction in load current of individual current sources and which would permit the production and operation of small apparatuses compensating ground fault currents with less power requirements, less overall weight, and a lower cost of acquisition.
Summary of the invention
The solution of the task is achieved by creating a new method of controlling an apparatus compensating ground fault currents according to the submitted invention. The apparatus compensating ground fault currents equipped with n-controlled current sources or formed by a single n-phase controlled current source is connected in the known method using n + 1 outputs between phase conductors of an n-phase distribution system. Its task is to generate the compensation current lo to compensate for the fault current lp occurring as a result of the single-phase earth faults, and injecting the compensation current l0 to the phase of the affected earth fault.
The essence of the method for controlling the apparatus compensating ground fault currents according to the submitted invention consists in the idea that the total compensation current l0 is generated as a vector sum of individual n compensating currents, generated by individual controlled current sources or individual phase outputs of the n-phase of the controlled current source. The current amplitudes of these individual compensation currents show, in absolute value, a deviation of no more than 25% from the value of — l0/n, and the phase shifts of these individual n
compensation currents show a difference of their values of no more than 30 ° as opposed to the total compensation current lo phase-shift.
In an advantageous embodiment of the method of controlling according to the invention, the apparatus compensating ground fault currents is controlled in such a way that the current amplitudes of individual compensating currents have the same size, their value being— of the amplitude of the total compensation current lo. The n
phase shifts of the compensation currents are also equal, and their value equals the value of the phase shift of the total compensation current.
The regulation of amplitudes and phase shifts of the components of the compensation current lo is done using common software and hardware resources, such as using control systems based on the technology of DSP microcontrollers and/or field-programmable gate array (FPGA). Unlike the known method of controlling the apparatus compensating ground fault currents, the method of the submitted invention has the advantage in that the vector sum of the individual compensation currents set by the above-described parameters comprises the necessary total compensation current l0 of the components generated at a lower current load of individual controlled current sources or individual phases of an n-phase controlled current source. The reduction of current load of current sources enables the construction of apparatus compensating ground fault currents with smaller space requirements, less weight, lower power requirements and consumption, and last but not least, with lower cost of acquisition.
Description of the drawings
The invention is described in detail by means of the drawings, in which Figure 1 is a diagram of a three-phase distribution system with earth connection in the first phase and with the apparatus compensating ground fault currents containing three controlled current sources; Figure 2 is a phasor diagram of voltages and currents of a three-phase power distribution system according to Figure. 1 , showing phase shifts of the individual compensation currents φι, φ2, Φ3 = φο, i.e. in the most preferred design of the method of control according to the invention; Figure 3 is a phasor diagram of voltages and currents of a three-phase power distribution system according to Figure 1 , showing the individual compensating currents generated by the known method, representing the present state of technology; Figure 4 is a phasor diagram of voltages and currents of a three-phase distribution system according to Figure 1 , showing phase shifts of the individual compensation currents φ-ι, φ2, φ3 in the maximum angular tolerance with regard to φ0; Figure 5 is a diagram of the connection of an n-phase distribution system with ground connection in the first phase and with the apparatus compensating ground fault currents containing an n-phase current source. Examples of the preferred embodiments of the invention
It should be understood that the following described and illustrated specific examples of the realization of the invention are presented solely for illustrative purposes and not as a limitation of the examples of the embodiments of the invention for the cases indicated. Experts who are familiar with the state of technology shall find, or using routine experimentation will be able to determine, a larger or smaller number of equivalents to the specific realizations of the invention which are specifically described here. These equivalents shall also be included into the scope of the claims.
Figure 1 shows a three-phase distribution system Λ with phase conductors l_i , l_2, L3. Between the phase conductors l_i , L2, L3 and the site with earth potential 5 the apparatus compensating ground fault currents 2 is connected containing three controlled current sources 3, 3', 3_^\ The first phase conductor Li of the distribution system 1 is affected by the ground fault 6, which causes fault current lp as the sum of parasitic currents in individual phases:
Figure imgf000008_0001
I =— +— +—
Z, Z2 Z3
The apparatus compensating ground fault currents 2, using controlled current sources 3, 3_[, 3^, generates a total compensation current l0 against fault current lp formed by the vector sum of individual compensation currents loi , I02, I03 generated by the controlled current sources 3, 2 , 3^. The controlled current sources 3, 3J., 3^ are, in the specific example of implementation, created by controlled power converters. These also may be voltage inverters, current inverters, or frequency inverters. The control of current sources 3, 3 , 3J_[ in terms of the regulation of current amplitudes and angles φ2,φ3 of the phase shift is performed by a control system functioning on the basis of DSP microcontrollers and/or field-programmable gate array (FPGA). Figure 2 shows an example of the most preferred method of controlling the apparatus compensating ground fault currents 2 to compensate for the fault current lp in the distribution system according to Figure 1. The total compensation current l0 is created as a vector sum of individual compensation currents Ioi , I02, I03 generated by individual controlled current sources 3, y_, 3_^. Meanwhile, the values of the individual compensation currents I01 , I02, I03 are guided so that the current amplitudes of the individual compensation currents l0i , I02, I03 have the same size on the value of 1/3 of the amplitude of the total compensation current l0, namely:
Figure imgf000009_0001
At the same time, the values of the angles φι, φ2,φ3 of the phase-shifts of the individual compensation currents l0i , I02, lo3 are controlled so that they have the same size as the value of the angle φ0 of the phase-shift of the total compensation current lo, namely: φ1 = φ2 = φ3 = φ0ι
In the case depicted in Figure 2, φ0 = 90°. Figure 2 is a phasor diagram of a 3-phase distribution system 1. according to Figure 1 , showing the voltages and currents in the complex (Gaussian) plane, where the x-axis (RE) shows the real part of the complex number and the y-axis (IM) shows the imaginary part of the complex number. The depiction assumes that the phase voltage (line-to-earth voltage) affected by the ground fault 6 is zero, i.e. ui = 0. In practice, the voltage u-i may have a minimum value. The remaining two phase voltages, then, have values of line-to-line voltage u2 = U21 , u3 = U31.
Figure 3, for comparison, shows the course of the control of the apparatus compensating ground fault currents 2 in a distribution system 1, with ground fault 6 by the current i.e. known method, in which a corresponding compensation current is generated against each vector component of the fault current lp. Given that ui = 0, U2 = u2i and U3 = U31 , then only two current sources 3^, 3^ generate individual compensating currents I02, I03 for which the following applies: - while '01 = 0
Figure imgf000010_0001
The current flowing through each controlled current source 3 , 3^ thus has an amplitude of size -^ and corresponding phase shift (φ2,φ3).
A comparison of values of the amplitudes of the current load (~ according to Figure
2 and i= according to Figure 3) then clearly shows that the current load of the controlled current sources 3, 3^, 3_^ is, in the known method of control according to Figure 3, about 70% greater than in the current sources 3, Z^, 3_^ controlled by the method according to the submitted invention according to Figure 2.
Figure 4 shows a further variant of the method of controlling the apparatus compensating ground fault currents 2 according to the invention, different from the variant depicted in Figure 2 and described above. The method of control of individual controlled current sources 3, 3^ is different in the sense that neither l0i = I02 = I03
= nor φι = Φ2 = Φ3 = φο applies. To improve the control and to reduce the current load of the controlled current sources 3, 3J., 3^ it is sufficient when the current amplitudes of individual compensation currents l0i , I02, I03 are not equal to but differ in an absolute value deviation of no more than 25% of the value ^ , and the
3
angles φι , φ2,φ3 of the phase shifts of the individual compensation currents l0i , I02, I03 show a difference of their value of no more than 30° against the angle φ0 of the phase shift of the total compensation current l0. Figure 4 shows a situation in which the first controlled current source 3 generates compensating current l0i with size of amplitude ^ , i.e. one third of the total compensation current l0 and has the same angle φι of phase shift, thus φι= φο· Compensation currents \02 and l03 generated from the other controlled current sources 3 , have an amplitude size about 15% greater than l0i and the phase shift angles φ2 = -30°and φ3 = 30° shifted by the indicated value from the vector of the compensation current l0i respectively of the total compensation current lo- Even in this case, the current load of individual controlled current sources 3, 3 , 3_^ is less than in the known method of control depicted in Figure 2, where the current load of the controlled current sources 3, y, 3 is 50% higher.
Figure 5 illustrates another implementation of the invention. This is an n-phase distribution system Λ with ground fault 6, as in Figure 1 , but the apparatus compensating ground fault currents 2 here is comprised of an n-phase controlled current source 4 instead of three controlled current sources 3, y, 2T_.
The method of control of the n-phase controlled current source 4 is completely the same as the method of control of the apparatus compensating ground fault currents 2 with three controlled current sources 3, 2 , 3^_ in the above-described examples, with the difference that the size of the amplitude of the individual compensation currents
(loi , lo2, lo3•••■ION) of the generated individual phase outputs is equal to— of the total n
compensation current l0. Industrial applicability
The method of controlling the apparatus compensating ground fault currents according to the invention can be used to compensate for fault currents that occur as a result of ground faults in an n-phase distribution system. Overview of the positions and symbols used in the drawing and in the description
1 n-phase distribution system
Li phase conductor
L2 phase conductor
L3 phase conductor
2 apparatus compensating ground fault currents
3 controlled current source
3' controlled current source
3" controlled current source
4 n-phase controlled current source
5 earth potential
6 ground fault
U1 phase voltage (line-to-earth voltage)
u2 phase voltage (line-to-earth voltage)
u3 phase voltage (line-to-earth voltage)
Ip1 parasitic current in phase
lP2 parasitic current in phase
Ip3 parasitic current in phase
lp fault current
Zi line-to-earth impedance
2.2 line-to-earth impedance
z3 line-to-earth impedance
lo total compensation current
loi compensating current in phase 1
102 compensating current in phase 2
'03 compensating current in phase 3
U12 line-to-line voltage
U23 line-to-line voltage
U31 line-to-line voltage
Φ1 compensating current l0i phase-shift φ2 compensating current I02 phase-shift
<t>3 compensating current I03 phase-shift
φο total compensation current lo phase-shift
LN n-phase conductor of distribution system
ION compensating current in a n-phase of controlled current source
UN phase voltage in a n-phase of distribution system
ZN line-to-earth impedance in a n-phase of distribution system

Claims

1. The method of controlling the apparatus compensating ground fault currents (2) to compensate for fault currents (lp), connected using (n + 1 ) outputs between phase conductors (l_i , L2, L3) of an n-phase electric distribution system (1 ) and site with earth potential (5), and equipped with (n) controlled current sources (3, 3', 3") or with one n-phase controlled current source (4) to generate the compensation current (l0) and its injection into the phase affected by the ground fault (6) characterized in that the total compensation current (l0) is formed as a vector sum of individual (n) compensating currents (l0i , I02, I03) generated by individual controlled current sources (3, 3', 3") or by individual phase outputs of the n-phase-controlled current source (4), while the current amplitudes of individual compensation currents (l0i , I02, I03) show, in absolute value, a deviation of no more than 25% from the value of l0/n, and the angles (φι , φ2, φ3) of the phase shifts of the individual compensation currents (l0i , I02, I03) show a difference in value of no more than 30° against the angle (φ0) of the phase shift of the total compensation current (l0).
2. The method according to claim 1 , characterized in that the current amplitudes of the individual compensation currents (l0i , I02, I03) have the same size in the value of 1/n of the amplitude of the total compensation current (l0) and the same angles (φι , φ2,φ3) of the phase shift, the size of which is the same as the value of the angle (φ0) of the phase shift of the total compensation current (l0).
PCT/CZ2013/000068 2012-10-25 2013-05-29 Method of controlling an apparatus compensating ground fault currents for compensating for fault currents in an n-phase distribution system WO2014063666A2 (en)

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CN105826940A (en) * 2016-06-01 2016-08-03 山东建筑大学 Three-phase unbalanced compensation point positioning method for low-voltage power distribution network
CN117277248A (en) * 2023-11-17 2023-12-22 昆明理工大学 Active arc extinction voltage-current conversion method, system and medium for power distribution network

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CN105826940A (en) * 2016-06-01 2016-08-03 山东建筑大学 Three-phase unbalanced compensation point positioning method for low-voltage power distribution network
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CN117277248A (en) * 2023-11-17 2023-12-22 昆明理工大学 Active arc extinction voltage-current conversion method, system and medium for power distribution network
CN117277248B (en) * 2023-11-17 2024-02-20 昆明理工大学 Active arc extinction voltage-current conversion method, system and medium for power distribution network

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WO2014063666A3 (en) 2014-06-12

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