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—ELECTRIC POWER NETWORKS; 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—ELECTRIC POWER NETWORKS; 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 feeding a single network from two or more generators or sources in parallel; Arrangements for feeding already energised networks from additional generators or sources in parallel
  • 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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• 2012
  • 2012-10-25 CZ CZ20120728A patent/CZ2012728A3/cs unknown
• 2013
  • 2013-05-29 EP EP13731266.6A patent/EP2912739A2/en not_active Withdrawn
  • 2013-05-29 WO PCT/CZ2013/000068 patent/WO2014063666A2/en not_active Ceased

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