WO1999057793A1 - Method and device for reducing the current in the neutral conductor - Google Patents
Method and device for reducing the current in the neutral conductor Download PDFInfo
- Publication number
- WO1999057793A1 WO1999057793A1 PCT/SE1999/000743 SE9900743W WO9957793A1 WO 1999057793 A1 WO1999057793 A1 WO 1999057793A1 SE 9900743 W SE9900743 W SE 9900743W WO 9957793 A1 WO9957793 A1 WO 9957793A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- current
- phase
- measuring
- load
- conductor
- Prior art date
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Classifications
-
- 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
-
- 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 present invention relates to an electric supply system having at least two phases and a neutral conductor and a controllable load for each phase, and to a method in such a system.
- the invention also relates to a single-phase electrical system comprising a first and a second load, said loads being serially connected, and two serially connected trans- formers connected in parallel with the loads, a point between the loads and a point between the transformers, being connected by a conductor, and to a method in such a system.
- controllable loads being, for example, rectifiers.
- any asymmetries in the phase voltages, or in the load will result in a current in the neutral conductor, causing a power loss in the neutral conductor. It is also possible to create a neutral point other than the neutral point of the neutral point of the three-phase supply system in the load in some way. In this case, a current in the neutral conductor will result in a power loss in the unit creating the neutral point.
- an electric supply system as initially defined, said supply system comprising means for reducing the current in the neutral conductor, and by a method as initially defined, said method including reducing the current in the neutral conductor.
- the size of the unit needed to balance the voltages of the system in case of an artificial neutral point being present is nrinirnized.
- the voltage drop that may occur in the unit creating the neutral point is reduced or prevented.
- said means for reducing the current in the neutral conductor comprises:
- Said apparatus may also comprise
- said method comprising the following steps:
- the apparatus also comprises filter means for normalizing the output by low-pass filtering.
- Said object is also achieved in a single-phase electric system as initially defined, said system comprising means for reducing the current in said conductor, and by a method in such a system, said method including reducing the current in said conductor.
- the system comprises
- first measuring means for measuring the current in the conductor - a second and a third measuring means for measuring the voltages across, or the currents through, said first and second loads,
- said method comprises the following steps:
- said method comprises the steps of: - measuring the current in the conductor;
- the invention utilizes the fact that the load having a greater current than the others will result in a current in the neutral conductor that is in phase with the curernt in this phase, or the voltage of the phase if cos ⁇ l, ⁇ being the phase angle. If the phase current or voltage is in phase with the current in the neutral conductor, the average value of the product of current and voltage will be at a maximum. If the neutral current and the phase current, or phase voltage, have phase angles in the range of 90° - 270°, the average value of the product will instead be negative, with a minimum at a phase angle of 180°.
- Figure 1 shows a three phase system in which the inventive method and apparatus may be applied
- Figure 2 shows the principles of an embodiment of the inventive method applied to a three-phase system
- Figure 3 shows the signal processing units applied in the feedback loop according to one embodiment of the invention
- Figure 4A shows a single-phase system in which the inventive method and apparatus may be applied
- Figure 4B shows the implementation of the inventive apparatus in the system of Figure 4A.
- Figure 1 shows an electrical system with three phases, R, S and T and a neutral conductor N.
- a first rectifier 1 is connected to phase R
- a second rectifier 3 is con- nected to phase S
- a third rectifier 5 is connected to phase T.
- the secondary input terminals of the rectifiers 1,3, 5 are interconnected in a connection point NL.
- a balancing unit 7 is connected to balance the voltages across the rectifiers.
- a balancing unit 7 may be implemented in several different ways.
- the balancing unit creates an artificial neutral point in the system. If the sum of the three currents differs from zero, a current will flow through this point. To nrimmize the size of the circuits needed to create a stable artificial neutral point, this current should be minimized. 6
- FIG. 1 is only one example of a system in which an apparatus according to the invention may be useful. It may also be used in a lighting system with lamps connected in a star configuration or a heating system. In such a system it will, for example, function to balance the phase voltages if the load is un- evenly distributed over the phases.
- Figure 2 shows the apparatus according to the invention applied in a three-phase network like the one in Figure 1.
- a first 11, a second 12 and a third 13 component are connected on the R phase, the S phase and the T phase, respectively.
- the com- ponents 11, 12, 13 may be the rectifiers shown in Figure 1.
- Each rectifier has a first and a second input terminal, a first and a second output terminal and a first and a second control input terminal.
- the components 11, 12 and 13 may be any kind of component having a controllable input current.
- An impedance Zll, Z12 Z13 between the first output terminal and earth represents the load on the first 11, second 12 and third 13 rectifier, respectively.
- the second output teirninal is connected to earth.
- the impedances Zll, Z 12 and Z13 can be connected in parallel (not shown in Figure 2).
- the respective phase voltage relative to earth is applied.
- the second input terminals are connected to the artificial neutral point.
- An interface unit 21, 22, 23 respectively, converting an input voltage or current to a control signal, which may be a digital signal or an analogue electric signal,
- each interface unit 21, 22, 23 is the respective phase voltage or current relative to earth.
- the output is a control signal having the same frequency and phase angle as the input voltage.
- the output signal of each interface unit 21, 22, 23 is fed to a multiplying unit, 31, 32, 33.
- the current in the neutral conductor is measured in a measuring unit 35 and applied to the input terminal of a fourth interface unit 37, converting the input current signal to an output control signal having the same frequency and phase angle as the input current.
- the output signal from the fourth interface unit 37 is fed to the multiplying units 31, 32, 33.
- the output signal from each multiplying unit 31, 32, 33 is the product of the respective phase voltage or current and the current in the neutral conductor. This product is fed back to the control input of the corresponding rectifier 11, 12, 13 through a processing unit 41, 42, 43, respectively.
- the processing units 41, 42, 43 may comprise several different units performing different functions, as will be discussed below in connection with Figure 3.
- the output signals from the multipliers 41, 42, 43 will be zero. If the current is different from zero, the output signals will be sine waves with twice the frequency of the mains and average values different from zero.
- the current in the neutral conductor will have sub- stantially the same phase as the phase voltage of the R phase, if cos ⁇ wl, ⁇ being the phase angle.
- the output signal from the multiplying unit 41 will be strong and positive.
- a strong and negative signal will be applied to the control input terminal of the first rectifier 11, to reduce the input current to this rectifier. This may be done, for example, by controlling the output current or the output power. If the phase voltage or current has the opposite phase of the current in the neutral conductor, the product of the phase voltage or current and the neutral current will be negative. Thus, the feedback signal in this phase will be positive and the input cur- rent to the rectifier will be increased.
- the processing of the output signals from the multipliers in the feedback loop includes the change of sign. In this way, a positive average output signal from a multiplier 41, 42, 43 will reduce the load on the corresponding phase.
- the processing of the output signals includes the following steps: - multiplication of the signal by a negative number
- FIG 3 shows an embodiment of a processing means, corresponding to one of the processing units 41, 42, 43 shown in Figure 2.
- An input signal from the multiplier which is a sine wave of twice the mains frequency, is first inverted in an inverting means 101, which may also be an amplifying means.
- the signal may also be subjected to other processing, for example, integration in an integrating means 103.
- the conversion to a direct voltage is carried out in a filtering unit, which may be implemented in any way known in the art.
- a filtering unit which may be implemented in any way known in the art.
- it is shown as an RC filter comprising a resistance 107 and a capacitance 109.
- the output from the RC filter forms the control signal which is fed to the control input of the appropriate rectifier.
- FIG. 4A shows a single-phase system in which the inventive idea may be utilized.
- a voltage is applied across two loads 201, 203 that are serially connected.
- Two transformer windings 205, 207 on the same core are connected in parallel with the loads 201, 203.
- the two branches are interconnected by a connection 209 between a point 210 between the loads 201, 203 and a point 211 between the transformer windings 205, 207.
- the windings 205, 207 ensure an equal distribution of the volt- age across the two loads 201, 203. If the currents through the loads 201, 203 are not equal, there will be a current in the connection 209 between the two branches.
- FIG 4B an apparatus according to the invention has been connected to reduce the current in the connection 209 between the branches.
- the loads 201, 203, the windings 205, 207 and the connection 209 are the same as in Figure 4A.
- the current in the connection 209 is measured and, if desired, converted to a control signal of the same frequency and phase angle, in a measuring device 212.
- the voltage across, or the current through, each of the two components 201, 203 is measured in a second and a third measuring device 215, 217, respectively.
- the output signals from the first 212 and second 215 measuring devices are input to a first multiplying device 219.
- the output from the first multiplying device 219 is inverted and processed in a first processing unit 223 as explained above and fed to the control input of the first load 201.
- the output signals from the first 212 and third 217 converting devices are input to a second multiplying device 221.
- the output from the second multiplying device 221 is inverted and processed in a second processing unit 225 as explained above and fed to the control input of the second load 203. 10
- two transformers comprising primary and secondary windings may be used instead of the transformers with duplicate windings on the same core.
- the outputs from the transformers should be connected in parallel, to force the primary voltages to be equal.
- the same principle can be used for three-phase systems.
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Supply And Distribution Of Alternating Current (AREA)
- Control Of Electrical Variables (AREA)
- Emergency Protection Circuit Devices (AREA)
- Rectifiers (AREA)
- Control Of Ac Motors In General (AREA)
- Measurement Of Current Or Voltage (AREA)
Abstract
Description
Claims
Priority Applications (7)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
CA002331710A CA2331710A1 (en) | 1998-05-06 | 1999-05-04 | Method and device for reducing the current in the neutral conductor |
JP2000547683A JP2002514036A (en) | 1998-05-06 | 1999-05-04 | Method and apparatus for reducing current in a neutral conductor |
BR9910214-5A BR9910214A (en) | 1998-05-06 | 1999-05-04 | Apparatus for use in an electrical supply system having at least two phases and a neutral conductor and a controllable load for each phase, process to reduce the current in a conductor in an electrical system having at least two phase conductors and a neutral conductor and a controllable load for each phase, single-phase electrical system, and, process to balance the voltage through two loads connected in series in a single-phase system |
HU0102324A HUP0102324A2 (en) | 1998-05-06 | 1999-05-04 | Method and device for reducing the current in the neutral conductor |
EP99948571A EP1092255A1 (en) | 1998-05-06 | 1999-05-04 | Method and device for reducing the current in the neutral conductor |
AU43047/99A AU4304799A (en) | 1998-05-06 | 1999-05-04 | Method and device for reducing the current in the neutral conductor |
DE1092255T DE1092255T1 (en) | 1998-05-06 | 1999-05-04 | Method and device for reducing the current in a neutral conductor |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
SE9801582-9 | 1998-05-06 | ||
SE9801582A SE513884C2 (en) | 1998-05-06 | 1998-05-06 | Device, method and system for reducing the zero current in electrical system |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1999057793A1 true WO1999057793A1 (en) | 1999-11-11 |
Family
ID=20411204
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/SE1999/000743 WO1999057793A1 (en) | 1998-05-06 | 1999-05-04 | Method and device for reducing the current in the neutral conductor |
Country Status (13)
Country | Link |
---|---|
EP (1) | EP1092255A1 (en) |
JP (1) | JP2002514036A (en) |
CN (1) | CN1308785A (en) |
AU (1) | AU4304799A (en) |
BR (1) | BR9910214A (en) |
CA (1) | CA2331710A1 (en) |
DE (1) | DE1092255T1 (en) |
ES (1) | ES2158836T1 (en) |
HU (1) | HUP0102324A2 (en) |
RU (1) | RU2000130721A (en) |
SE (1) | SE513884C2 (en) |
TR (1) | TR200003209T2 (en) |
WO (1) | WO1999057793A1 (en) |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US9244521B2 (en) | 2012-12-26 | 2016-01-26 | Intel Corporation | Supporting runtime D3 and buffer flush and fill for a peripheral component interconnect device |
KR102248724B1 (en) * | 2013-12-18 | 2021-05-07 | 오티스 엘리베이터 컴파니 | Control strategies for multilevel line regenerative drive |
Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CA2157307A1 (en) * | 1994-10-10 | 1996-04-11 | Luke Yu | Zero-Sequence Current Suppressor |
US5568371A (en) * | 1994-09-29 | 1996-10-22 | Texas A&M University System | Active harmonic power filter apparatus and method |
US5574356A (en) * | 1994-07-08 | 1996-11-12 | Northrop Grumman Corporation | Active neutral current compensator |
US5648894A (en) * | 1994-09-30 | 1997-07-15 | General Electric Company | Active filter control |
-
1998
- 1998-05-06 SE SE9801582A patent/SE513884C2/en unknown
-
1999
- 1999-05-04 TR TR2000/03209T patent/TR200003209T2/en unknown
- 1999-05-04 HU HU0102324A patent/HUP0102324A2/en unknown
- 1999-05-04 ES ES99948571T patent/ES2158836T1/en active Pending
- 1999-05-04 EP EP99948571A patent/EP1092255A1/en not_active Withdrawn
- 1999-05-04 WO PCT/SE1999/000743 patent/WO1999057793A1/en not_active Application Discontinuation
- 1999-05-04 AU AU43047/99A patent/AU4304799A/en not_active Abandoned
- 1999-05-04 CN CN99808342.9A patent/CN1308785A/en active Pending
- 1999-05-04 JP JP2000547683A patent/JP2002514036A/en active Pending
- 1999-05-04 RU RU2000130721/09A patent/RU2000130721A/en not_active Application Discontinuation
- 1999-05-04 DE DE1092255T patent/DE1092255T1/en active Pending
- 1999-05-04 BR BR9910214-5A patent/BR9910214A/en not_active Application Discontinuation
- 1999-05-04 CA CA002331710A patent/CA2331710A1/en not_active Abandoned
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5574356A (en) * | 1994-07-08 | 1996-11-12 | Northrop Grumman Corporation | Active neutral current compensator |
US5568371A (en) * | 1994-09-29 | 1996-10-22 | Texas A&M University System | Active harmonic power filter apparatus and method |
US5648894A (en) * | 1994-09-30 | 1997-07-15 | General Electric Company | Active filter control |
CA2157307A1 (en) * | 1994-10-10 | 1996-04-11 | Luke Yu | Zero-Sequence Current Suppressor |
Also Published As
Publication number | Publication date |
---|---|
TR200003209T2 (en) | 2001-03-21 |
RU2000130721A (en) | 2002-11-27 |
AU4304799A (en) | 1999-11-23 |
SE9801582L (en) | 1999-11-07 |
CN1308785A (en) | 2001-08-15 |
CA2331710A1 (en) | 1999-11-11 |
DE1092255T1 (en) | 2002-02-07 |
JP2002514036A (en) | 2002-05-14 |
HUP0102324A2 (en) | 2001-10-28 |
SE9801582D0 (en) | 1998-05-06 |
EP1092255A1 (en) | 2001-04-18 |
ES2158836T1 (en) | 2001-09-16 |
SE513884C2 (en) | 2000-11-20 |
BR9910214A (en) | 2001-01-09 |
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