WO2023285730A1 - Method and apparatus for eliminating voltage distortion in electricity distribution network - Google Patents
Method and apparatus for eliminating voltage distortion in electricity distribution network Download PDFInfo
- Publication number
- WO2023285730A1 WO2023285730A1 PCT/FI2022/050426 FI2022050426W WO2023285730A1 WO 2023285730 A1 WO2023285730 A1 WO 2023285730A1 FI 2022050426 W FI2022050426 W FI 2022050426W WO 2023285730 A1 WO2023285730 A1 WO 2023285730A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- voltage
- frequency
- band
- network
- ref
- Prior art date
Links
- 238000000034 method Methods 0.000 title claims abstract description 30
- 230000005611 electricity Effects 0.000 title claims description 45
- 238000005259 measurement Methods 0.000 claims abstract description 30
- 238000001914 filtration Methods 0.000 claims abstract description 20
- 230000001965 increasing effect Effects 0.000 claims description 6
- 230000010363 phase shift Effects 0.000 claims description 5
- 230000007423 decrease Effects 0.000 claims description 3
- 230000001939 inductive effect Effects 0.000 description 4
- 230000010355 oscillation Effects 0.000 description 4
- 238000001228 spectrum Methods 0.000 description 2
- 230000003321 amplification Effects 0.000 description 1
- 230000002238 attenuated effect Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 239000003990 capacitor Substances 0.000 description 1
- 230000000295 complement effect Effects 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000005485 electric heating Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 230000007257 malfunction Effects 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 238000003199 nucleic acid amplification method Methods 0.000 description 1
- 238000010248 power generation Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000003672 processing method Methods 0.000 description 1
- 238000007430 reference method Methods 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000011144 upstream manufacturing Methods 0.000 description 1
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
- H02J3/01—Arrangements for reducing harmonics or ripples
-
- 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
Definitions
- the invention relates to a method and apparatus for eliminating voltage distortion in an electricity distribution network according to the preambles of the independent claims directed thereto.
- AC power distribution in the electricity grid is generally based on a fundamental frequency of sine waveform, most commonly 50Hz or 60Hz. Electrical loads that draw sinusoidal current (power) at this same frequency are linear loads. Linear loads can be resistive, such as heating resistors used in direct electric heating. On the other hand, electrical loads that draw sinusoidal current (power) at the same fundamental frequency but have phase shift with the voltage are inductive (inductors) or capacitive (capacitors) linear loads.
- linear loads the most common electrical loads are electric motors. Motors connected directly to the mains network without speed control are linear loads, which are partially inductive with a power factor cos cp between 0.7 and 0.9. Such unregulated linear loads do not degrade the voltage quality of the electricity network. However, inductive and capacitive loads cause reactive power and degrade the efficiency of the electricity distribution network, while limiting the maximum of the electric power transmission.
- adjustable motor drives and other adjustable electrical devices have become more common on the electricity network to improve the efficiency of the use of electrical energy, for example in the form of inverters, rectifiers, computers and televisions. Such adjustable electric drives draw from the network not only the fundamental frequency, but also other frequencies that differ from the grid waveform and are called non linear loads.
- harmonic currents Currents that deviate from the fundamental frequency of the network are called harmonic currents, which are caused by harmonic components from non-linear loads. Harmonics cause a deviation in the fundamental sinusoidal voltage of the electrical energy distribution, i.e. a voltage distortion, wherein high-power electrical loads drawing harmonic current from the network cause a significant change in the local distribution waveform of the voltage. As a result, the quality of the electricity network no longer meets the requirements.
- the increasing number of non-linear loads and harmonic currents in the electricity network causes local problems, first of all by causing local distortion of the electricity distribution voltage near non-linear loads, and by overloading the electricity distribution network due to harmonic currents. Both of the above problems eventually cause malfunctions and equipment damage to electrical equipment.
- a conventional active harmonics filter works on the principle of measuring and controlling current.
- a current-controlled AHF measures the harmonic current caused by a non-linear load on the electricity network and generates a current that is in opposite phase compared to the harmonic current and feeding it into the electricity network. This reduces the sum of the harmonic currents at the connection point of the AHF and the resulting voltage distortion is reduced.
- the AHF must be adjusted and set (parameter setting) to the electrical environment of the application. Without expert commissioning setup, a conventional AHF can amplify certain frequency harmonics rather than attenuate them. Furthermore, if there are substantial changes in the local electricity network after commissioning, the current-controlled AHF must be reset to reflect the changed conditions.
- the addition of a high capacitance near the connection point of the current-controlled AHF will cause a resonant oscillation between the AHF and the capacitance, in which case the solution is to reset the parameters to produce less or no resonant frequency.
- Some current-controlled active harmonic filters have been developed with self-control features that allow the device itself to analyze the state of the local electricity network and, if necessary, reset itself accordingly. In some cases, changes in the electrical environment of the application can also be responded by measuring of the electricity network and setting the parameters of the AHF through a remote connection.
- the installation of current sensors for a conventional current-controlled AHF, the parameter setting based on measurements of the electricity network and the potential resetting is an availability-critical task requiring expertise and quality, which substantially increases the cost of network disturbances caused by the harmonics.
- Patent US 6320392 describes a solution to a problem when using a conventional active harmonic filter, where the response of the compensation current cannot be properly determined due to the constantly changing topology of the network.
- the solution describes a filter apparatus where the network response to harmonic currents is measured by feeding frequencies that are different from the harmonic frequency into the network and measuring the response caused by these frequencies and thereby determining the compensation response computationally.
- a single harmonic compensation using voltage measurement is described.
- the paper describes voltage measurement from the network and filtering with a band-pass filter to obtain the 3rd harmonic voltage and further to determine the amplitude and phase of the compensation current to be fed to the grid.
- the paper also describes the determination of the voltage distortion for the 3rd harmonic by removing the fundamental voltage from the computed harmonic voltage signal.
- the method and apparatus of the present invention for eliminating voltage distortion in an electricity distribution network are to provide a decisive improvement on the problems described above, and thereby to raise essentially the available prior art.
- the method and apparatus of the invention are principally characterized by what is presented in the characterizing part of the independent claims directed thereto.
- the basic idea of the invention is, first of all, to eliminate voltage distortion in the electricity distribution network caused by harmonic currents drawn by non-linear loads by means of an active harmonic filter that is based on a voltage measurement instead of a current measurement. In this case, no current measurement from the network is required, but the method and the device operate by measuring only the voltage at its connection point.
- the measurement of the voltage distortion in the electricity network is first of all carried out by the reference method, wherein, for example, the ideal sine- wave reference signal at network frequency is subtracted from the actual voltage value measured by-phase from the electricity network.
- the voltage distortion in the power grid is then obtained as the difference between the actual reference value and the ideal reference value.
- a high-pass filter an ideal band-pass filter, or a similar signal processing method may be used to help to measure the voltage distortion.
- the actual voltage value is measured from the electricity network, e.g. phase by phase, and then filtered by a high-pass filter that removes the lower fundamental frequency of the network signal and does not cause a phase shift in the remaining harmonic frequencies.
- the remaining signal after the high-pass filtering is the voltage distortion of the electricity network.
- the fundamental frequency of the network is attenuated to such an extent that no fundamental frequency component disturbing the control circuit is remained after summation of the parallel band-pass outputs. If there is still a residual fundamental frequency left after the band-pass filtering and summing, the fundamental frequency can also be compensated by arranging the adjustable power supply downstream in the control circuit so that it does not supply this current with fundamental frequency to the electricity network.
- the resulting voltage distortion in the electricity network is further divided by band-pass filters into frequency-band specific components, amplified and inverted.
- Inversion can be performed at any point along the control path, e.g. after the voltage measurement, after the band-pass filtering, after the adjustable gain, or after the signal summation. Further, the inversion may be performed before the voltage measurement, in which case the voltage to be measured is already inverted.
- a signal equivalent to the voltage distortion, but inversely biased is obtained, which provides the internal current reference of the active harmonic filter of the invention.
- This internal current reference is fed to an adjustable power supply in the AHF device, preferably implemented by power electronics, which supplies the current corresponding to the provided current reference to the electricity network.
- the current supplied to the network by the power supply is in the opposite phase compared to the voltage distortion, thus regulating the voltage distortion to a minimum.
- the main advantage of the method and apparatus according to the invention is, first of all, the simplicity of the voltage measurements of the method, which enables carrying out the measurements using conventional electrical measurement methods directly at the connection point.
- a further advantage of the method and apparatus of the invention is its adaptability to the variability of the electricity network at the connection point of the active harmonic filter.
- the network in the vicinity of the connection point may have local power generation, the electricity network at the connection point may be low or high impedance relative to the main grid, may contain a large number of parallel capacitive, inductive or non-linear load, or may contain loads down- or upstream the electricity network.
- Adaptability prevents instability and resonant oscillation of the control system if loads or characteristics of the electricity network change, amplifying some frequencies.
- Adaptivity is implemented by means of the said band-pass filters and adjustable amplifiers. If the control system becomes unstable, the amplitude of the voltage oscillation increases at the resonant frequency.
- the method and apparatus of the invention allow the system to be stabilized by adjusting the gain of the frequency-specific amplifier.
- Fig. la shows the general principle of a method and apparatus of the invention
- Fig. lb shows a complementary general principle of a method and apparatus according to a preferred embodiment of the invention.
- the invention relates first of all to a method for eliminating voltage distortion in an electricity distribution network, caused by the harmonic currents generated by nonlinear loads L, based on measuring and filtering the voltage distortion for example, phase by phase from an AC network by means of an active harmonic filter.
- the removal of voltage distortion is first of all based on the voltage measurement of the alternating current network AC with the voltage measurement scheme V as shown in Figure la, whereby the measurement results in the real actual value of the voltage of the electricity distribution network. From the measured actual value, the ideal sinusoidal control voltage signal V ref is subtracted, leaving after the voltage measurement arrangement a voltage distortion signal which is fed to at least one band-pass filter BP fi .
- Each band-pass filter BP f 1... BP fn has a specific frequency pass-band, i.e.
- band-pass filter BP fi only allows the signal in the frequency band fi to pass through.
- the signal of the specified frequency band is fed to amplifier A fi , whose gain G fi can be adjusted by a control.
- the filtered and amplified signal is inverted by an inverter Y fi .
- band-pass filtering is carried out, respectively, by a band-pass filter PB fn , amplified by the amplifier A fn with an adjustable gain G fn and inverted by the inverter Y fn .
- All filtered, amplified and inverted signals are combined in the adder S f into a single sum signal, resulting in an internal current reference i ref of the active harmonic filter.
- the current reference i ref is fed to an adjustable power supply I, preferably implemented with power electronics, which supplies the current corresponding to the received current reference without phase shift to the electricity network AC.
- the actual voltage value of the AC network is measured by a voltage measurement arrangement V, and the fundamental frequency component is removed from the actual voltage value, for example by a high-pass filter HP f or a similar method of filtering the fundamental frequency of the electricity network.
- harmonic distortions in the electricity network are eliminated by selecting filter-specifically the harmonic frequency bands of the electricity network, such as odd (3rd, 5th, etc.) harmonics, as the frequency bands of the band-pass filters, and by setting a separate, adjustable gain for each frequency.
- the resonant frequency oscillation of the control system is prevented by adjusting the gain G fi , G fn of the frequency band specific control amplifier A fi , A fn . If the amplitude of the resonant frequency signal fi, f n is found to decrease as the gain G fi , G fn of the control amplifier A fl , A fn is increased, the gain G fi , G fn is further increased. On the other hand, if the amplitude of the resonant frequency signal fi, f n also increases when the gain G fi , G fn is increased, the gain G fi , G fn of the control amplifier A fi , A fn is decreased correspondingly. In a further preferred embodiment of the method of the invention, the gain G fi , G fn of a frequency specific gain control amplifier A fi , A fn is automatically controlled based on amplitude measurement data when the control values reach their lower or upper limit.
- the inversion of the signal is carried out by an inverter Y fn at an arbitrary point of the control circuit, for example before the voltage measurement arrangement V, V ref ; before the band-pass filter PB fi , PB fn ; after the band-pass filter PB fi , PB fn ; before the adjustable amplifier A fi , A fn ; after the amplifier A fi , A fn ; or after the adder Sf.
- the invention relates to an apparatus for eliminating voltage distortion in an electricity distribution network, based on measuring and filtering voltage distortions, for example phase-by-phase, in an alternating current network.
- the apparatus for measuring and filtering voltage distortions comprises:
- V ref substantially connected to the AC electricity distribution network for measuring the real actual value of the voltage and the voltage distortion
- an adjustable power supply I to supply the current according to the current reference i ref to the AC electricity network without substantial phase shift.
- a high-pass filter HP f is connected to the network and arranged substantially in the connection with the voltage measurement arrangement.
- the adjustable power supply I does not produce the basic frequency of the electrical network for the current supplied to the network according to the current reference i ref ⁇
- the invention is not limited to the embodiments described or explained above, but can be modified within the basic idea of the invention, depending on the circumstances, by using in the method the most appropriate type of filter for filtering the fundamental frequency of the network, such as an RC, LC, LCL, Chebyshev, Butterworth, Bessel or Cauer filter or a similar signal processing filter.
- the implementation may be modified by component choices to increase cost- effectiveness and to emphasize and modify the required characteristics. It is clear that digital or analogue components can be used to measure and filter the voltage distortion, and automatic computer-controlled control solutions based on sensors or the like can be used.
Abstract
The invention relates to a method for active measurement and filtering of voltage distortion caused by harmonic currents drawn by nonlinear loads (L) in an electrical distribution network (AC). The measurement and filtering of the voltage distortion in nonlinear loads (L) is performed by voltage measurement: - by measuring the voltage (V) condition from the mains (AC) phase-by-phase and removing the undistorted, mains frequency reference value of the voltage, such as the fundamental component (Vref); and - filtering the resulting voltage distortion into one or more frequency-band specific components, such as odd harmonics or similar, wherein one or more components of the voltage difference are amplified (Afl, Afl) per frequency band using a separate adjustable gain (Gfl, Gfn) for each frequency band, inverted and summed to obtain a current reference ( iref ) to an adjustable power supply (I) which supplies the current reference (iref) to the mains (AC).
Description
Method and apparatus for eliminating voltage distortion in electricity distribution network
The invention relates to a method and apparatus for eliminating voltage distortion in an electricity distribution network according to the preambles of the independent claims directed thereto.
AC power distribution in the electricity grid is generally based on a fundamental frequency of sine waveform, most commonly 50Hz or 60Hz. Electrical loads that draw sinusoidal current (power) at this same frequency are linear loads. Linear loads can be resistive, such as heating resistors used in direct electric heating. On the other hand, electrical loads that draw sinusoidal current (power) at the same fundamental frequency but have phase shift with the voltage are inductive (inductors) or capacitive (capacitors) linear loads.
Further, among linear loads, the most common electrical loads are electric motors. Motors connected directly to the mains network without speed control are linear loads, which are partially inductive with a power factor cos cp between 0.7 and 0.9. Such unregulated linear loads do not degrade the voltage quality of the electricity network. However, inductive and capacitive loads cause reactive power and degrade the efficiency of the electricity distribution network, while limiting the maximum of the electric power transmission.
Over the past decades, adjustable motor drives and other adjustable electrical devices have become more common on the electricity network to improve the efficiency of the use of electrical energy, for example in the form of inverters, rectifiers, computers and televisions. Such adjustable electric drives draw from the network not only the fundamental frequency, but also other frequencies that differ from the grid waveform and are called non linear loads. Currents that deviate from the fundamental frequency of the network are called harmonic currents, which are caused by harmonic components from non-linear loads. Harmonics cause a deviation in the fundamental sinusoidal voltage of the electrical energy distribution, i.e. a voltage distortion, wherein high-power electrical loads drawing harmonic current from the network cause a significant change in the local distribution waveform of the voltage. As a result, the quality of the electricity network no longer meets the requirements. The increasing number of non-linear loads and harmonic currents in the electricity network causes local problems, first of all by causing local distortion of the electricity distribution voltage near non-linear loads, and by overloading the electricity distribution network due to harmonic currents. Both of the above problems eventually cause malfunctions and equipment damage to electrical equipment.
Problems caused by harmonic currents can be compensated by using harmonic filters. When the spectrum of harmonic frequencies at the problem site is invariant, filtering the highest power harmonic voltages and/or harmonic
currents with frequency-specific passive filters works well. Further, if the frequency spectrum and amplitude of the harmonics at the problem site vary, an Active Harmonics Filter (AHF) is commonly used as a solution to the problems caused by the harmonics.
A conventional active harmonics filter (AHF) works on the principle of measuring and controlling current. A current-controlled AHF measures the harmonic current caused by a non-linear load on the electricity network and generates a current that is in opposite phase compared to the harmonic current and feeding it into the electricity network. This reduces the sum of the harmonic currents at the connection point of the AHF and the resulting voltage distortion is reduced. To work effectively, the AHF must be adjusted and set (parameter setting) to the electrical environment of the application. Without expert commissioning setup, a conventional AHF can amplify certain frequency harmonics rather than attenuate them. Furthermore, if there are substantial changes in the local electricity network after commissioning, the current-controlled AHF must be reset to reflect the changed conditions. For example, the addition of a high capacitance near the connection point of the current-controlled AHF will cause a resonant oscillation between the AHF and the capacitance, in which case the solution is to reset the parameters to produce less or no resonant frequency. Some current-controlled active harmonic filters have been developed with self-control features that allow the device itself to analyze the state of the local
electricity network and, if necessary, reset itself accordingly. In some cases, changes in the electrical environment of the application can also be responded by measuring of the electricity network and setting the parameters of the AHF through a remote connection. Regardless of the method, the installation of current sensors for a conventional current-controlled AHF, the parameter setting based on measurements of the electricity network and the potential resetting is an availability-critical task requiring expertise and quality, which substantially increases the cost of network disturbances caused by the harmonics.
Patent US 6320392 describes a solution to a problem when using a conventional active harmonic filter, where the response of the compensation current cannot be properly determined due to the constantly changing topology of the network. The solution describes a filter apparatus where the network response to harmonic currents is measured by feeding frequencies that are different from the harmonic frequency into the network and measuring the response caused by these frequencies and thereby determining the compensation response computationally. Further in the paper "A Novel Voltage Control for Active Shunt Power Filters" (Zanchetta et al., Industrial Electronics, 2002), a single harmonic compensation using voltage measurement is described. The paper describes voltage measurement from the network and filtering with a band-pass filter to obtain the 3rd harmonic voltage and further to determine the amplitude and phase of the compensation current to be fed to the grid. In this
context, the paper also describes the determination of the voltage distortion for the 3rd harmonic by removing the fundamental voltage from the computed harmonic voltage signal.
The method and apparatus of the present invention for eliminating voltage distortion in an electricity distribution network are to provide a decisive improvement on the problems described above, and thereby to raise essentially the available prior art. In order to attain this objective, the method and apparatus of the invention are principally characterized by what is presented in the characterizing part of the independent claims directed thereto.
The basic idea of the invention is, first of all, to eliminate voltage distortion in the electricity distribution network caused by harmonic currents drawn by non-linear loads by means of an active harmonic filter that is based on a voltage measurement instead of a current measurement. In this case, no current measurement from the network is required, but the method and the device operate by measuring only the voltage at its connection point.
The measurement of the voltage distortion in the electricity network is first of all carried out by the reference method, wherein, for example, the ideal sine- wave reference signal at network frequency is subtracted from the actual voltage value measured by-phase from the electricity network. The voltage distortion in the power
grid is then obtained as the difference between the actual reference value and the ideal reference value.
If an ideal sinusoidal reference value is not available or cannot be used, a high-pass filter, an ideal band-pass filter, or a similar signal processing method may be used to help to measure the voltage distortion. When using one or more high-pass filters, the actual voltage value is measured from the electricity network, e.g. phase by phase, and then filtered by a high-pass filter that removes the lower fundamental frequency of the network signal and does not cause a phase shift in the remaining harmonic frequencies. The remaining signal after the high-pass filtering is the voltage distortion of the electricity network. In contrast, with ideal band-pass filters, the fundamental frequency of the network is attenuated to such an extent that no fundamental frequency component disturbing the control circuit is remained after summation of the parallel band-pass outputs. If there is still a residual fundamental frequency left after the band-pass filtering and summing, the fundamental frequency can also be compensated by arranging the adjustable power supply downstream in the control circuit so that it does not supply this current with fundamental frequency to the electricity network.
The resulting voltage distortion in the electricity network is further divided by band-pass filters into frequency-band specific components, amplified and inverted. Inversion can be performed at any point along the control path, e.g. after the voltage measurement, after the band-pass filtering, after the adjustable gain,
or after the signal summation. Further, the inversion may be performed before the voltage measurement, in which case the voltage to be measured is already inverted. As a result of the above, a signal equivalent to the voltage distortion, but inversely biased, is obtained, which provides the internal current reference of the active harmonic filter of the invention. This internal current reference is fed to an adjustable power supply in the AHF device, preferably implemented by power electronics, which supplies the current corresponding to the provided current reference to the electricity network. The current supplied to the network by the power supply is in the opposite phase compared to the voltage distortion, thus regulating the voltage distortion to a minimum.
The main advantage of the method and apparatus according to the invention is, first of all, the simplicity of the voltage measurements of the method, which enables carrying out the measurements using conventional electrical measurement methods directly at the connection point.
A further advantage of the method and apparatus of the invention is its adaptability to the variability of the electricity network at the connection point of the active harmonic filter. For example, in terms of control response, the network in the vicinity of the connection point may have local power generation, the electricity network at the connection point may be low or high impedance relative to the main grid, may contain a large number of parallel capacitive, inductive or non-linear load, or may contain loads down- or upstream the
electricity network. Adaptability prevents instability and resonant oscillation of the control system if loads or characteristics of the electricity network change, amplifying some frequencies. Adaptivity is implemented by means of the said band-pass filters and adjustable amplifiers. If the control system becomes unstable, the amplitude of the voltage oscillation increases at the resonant frequency. The method and apparatus of the invention allow the system to be stabilized by adjusting the gain of the frequency-specific amplifier.
Other preferred embodiments of the method and apparatus of the invention are presented in the dependent claims directed thereto.
In the subsequent description, the invention will be illustrated in detail while referring to the accompanying drawings, in which: Fig. la shows the general principle of a method and apparatus of the invention,
Fig. lb shows a complementary general principle of a method and apparatus according to a preferred embodiment of the invention.
The invention relates first of all to a method for eliminating voltage distortion in an electricity distribution network, caused by the harmonic currents generated by nonlinear loads L, based on measuring and
filtering the voltage distortion for example, phase by phase from an AC network by means of an active harmonic filter. The removal of voltage distortion is first of all based on the voltage measurement of the alternating current network AC with the voltage measurement scheme V as shown in Figure la, whereby the measurement results in the real actual value of the voltage of the electricity distribution network. From the measured actual value, the ideal sinusoidal control voltage signal Vref is subtracted, leaving after the voltage measurement arrangement a voltage distortion signal which is fed to at least one band-pass filter BPfi. Each band-pass filter BPf1... BPfn has a specific frequency pass-band, i.e. for example the band-pass filter BPfi only allows the signal in the frequency band fi to pass through. After band-pass filtering, the signal of the specified frequency band is fed to amplifier Afi, whose gain Gfi can be adjusted by a control. After amplification, the filtered and amplified signal is inverted by an inverter Yfi. For each desired frequency band fn, band-pass filtering is carried out, respectively, by a band-pass filter PBfn, amplified by the amplifier Afn with an adjustable gain Gfn and inverted by the inverter Yfn. All filtered, amplified and inverted signals are combined in the adder Sf into a single sum signal, resulting in an internal current reference iref of the active harmonic filter. The current reference iref is fed to an adjustable power supply I, preferably implemented with power electronics, which supplies the current corresponding to the received current reference without phase shift to the electricity network AC.
In a preferred embodiment of the method of the invention, referring in particular to Figure lb, the actual voltage value of the AC network is measured by a voltage measurement arrangement V, and the fundamental frequency component is removed from the actual voltage value, for example by a high-pass filter HPf or a similar method of filtering the fundamental frequency of the electricity network. In a further preferred embodiment of the method of the invention, harmonic distortions in the electricity network are eliminated by selecting filter-specifically the harmonic frequency bands of the electricity network, such as odd (3rd, 5th, etc.) harmonics, as the frequency bands of the band-pass filters, and by setting a separate, adjustable gain for each frequency.
In a further preferred embodiment of the method of the invention, the resonant frequency oscillation of the control system is prevented by adjusting the gain Gfi, Gfn of the frequency band specific control amplifier Afi, Afn . If the amplitude of the resonant frequency signal fi, fn is found to decrease as the gain Gfi, Gfn of the control amplifier Afl, Afn is increased, the gain Gfi, Gfn is further increased. On the other hand, if the amplitude of the resonant frequency signal fi, fn also increases when the gain Gfi, Gfn is increased, the gain Gfi, Gfn of the control amplifier Afi, Afn is decreased correspondingly. In a further preferred embodiment of the method of the invention, the gain Gfi, Gfn of a frequency specific gain control amplifier Afi, Afn is automatically controlled
based on amplitude measurement data when the control values reach their lower or upper limit.
In a further preferred embodiment of the method of the invention, the inversion of the signal is carried out by an inverter Yfn at an arbitrary point of the control circuit, for example before the voltage measurement arrangement V, Vref ; before the band-pass filter PBfi, PBfn; after the band-pass filter PBfi, PBfn; before the adjustable amplifier Afi, Afn; after the amplifier Afi, Afn; or after the adder Sf.
On the other hand, the invention relates to an apparatus for eliminating voltage distortion in an electricity distribution network, based on measuring and filtering voltage distortions, for example phase-by-phase, in an alternating current network. The apparatus for measuring and filtering voltage distortions comprises:
- a voltage measurement device V, Vref substantially connected to the AC electricity distribution network for measuring the real actual value of the voltage and the voltage distortion;
- at least one frequency specific band-pass filter BPfi to filter the frequency specific voltage distortion signal caused by a harmonic;
- an amplifier Afi, Afn with adjustable gain Gfi, G;n for each separate band-pass filtered frequency to increase or decrease the signal amplitude to compensate the changes caused by the variations in the electricity network at the connection point;
- an inverter Yfi, Yfn to invert the voltage signal;
- an adder Sf to sum the inverted signals f ... fn into a single sum signal and to further obtain the current reference iref; and
- an adjustable power supply I to supply the current according to the current reference iref to the AC electricity network without substantial phase shift.
In a preferred embodiment of the apparatus of the invention, a high-pass filter HPf is connected to the network and arranged substantially in the connection with the voltage measurement arrangement.
As a further preferred embodiment of the apparatus of the invention, the adjustable power supply I does not produce the basic frequency of the electrical network for the current supplied to the network according to the current reference iref¬ it is obvious that the invention is not limited to the embodiments described or explained above, but can be modified within the basic idea of the invention, depending on the circumstances, by using in the method the most appropriate type of filter for filtering the fundamental frequency of the network, such as an RC, LC, LCL, Chebyshev, Butterworth, Bessel or Cauer filter or a similar signal processing filter. In the design of the electronic circuitry implementing the basic idea of the method and the apparatus, the implementation may be modified by component choices to increase cost- effectiveness and to emphasize and modify the required characteristics. It is clear that digital or analogue components can be used to measure and filter the voltage
distortion, and automatic computer-controlled control solutions based on sensors or the like can be used.
Claims
1. A method for active measurement and filtering of voltage distortion caused by harmonic currents drawn by nonlinear loads (L) in an electricity distribution network (AC), wherein the voltage distortion measurement and filtering of the nonlinear loads (L) is performed by voltage measurement (V): - by measuring the actual voltage value by-phase from the electricity distribution network (AC) and removing the undistorted, network frequency reference value of the voltage, such as the fundamental frequency component Vref; and
- by filtering the voltage distortion obtained into one or more frequency-band specific components (fi...fn), such as odd harmonics or the like; characterized in that one or more components of the voltage distortion (fi, fn) are amplified (Afi, Afn) on a frequency-band basis using a separately adjustable gain (Gfi, Gfn) for each frequency band, inverted and summed to obtain a current reference (iref) for an adjustable power supply (I), which supplies the current corresponding to the current reference (iref) to the electrical distribution network (AC).
2. The method according to claim 1, characterized in that the fundamental component of the voltage is removed from the actual value of the voltage by a high-pass filter (HPf) , a band-pass filter (PBfi, PBfn) , or the like.
3. The method according to claim 1 or 2, characterized in that the gain ( Gfi, Gfn) of each freguency-band specific component (fi, fn) of the voltage distortion is adjusted to a higher value, if increasing the gain ( Gfi, Gfn) decreases the amplitude of the frequency-band component, and to a lower value if increasing the gain ( Gfi, Gfn) increases the amplitude of the voltage distortion component (fi, fn) .
4. The method of claim 3, characterized in that the gain of each frequency band specific component ( Gfi, Gfn) is automatically adjusted.
5. The method according to any of the preceding claims
1 to 4, characterized in that the voltage distortion measured from the electricity network is amplified and inverted to obtain a current reference (iref) that is passed to a power supply (I) which supplies a current corresponding to the current reference (iref) to the electricity network (AC) without substantial phase shift.
6. The method according to claim 5, characterized in that the power supply is most preferably implemented by power electronics.
7. An apparatus for the active measurement and filtering of voltage distortion caused by harmonic currents drawn by non-linear loads in an electrical distribution network, characterized in that the apparatus comprises means for measuring and filtering the harmonics by voltage measurement on a phase-by-phase basis,
comprising at least a voltage measurement arrangement (V, Vref) , at least one frequency specific band-pass and/or band-stop filter (PBfi, PBfn) , a frequency band specific amplifier (Afi, Afn) with adjustable gain (Gfi, Gfn) , a frequency band specific signal inverter (Yfn) , a signal adder (Sf) and an adjustable power supply (I).
8. The apparatus according to claim 7, characterized in that a high-pass filter (HPf) is arranged in connection with the voltage measurement arrangement (V) to filter out the fundamental frequency of the electricity network (AC).
9. The apparatus according to claim 7 or 8, characterized in that it comprises means for detecting amplitude changes of the frequency band specific signals (f1 ...fn) to determine the frequency band specific adjustable gain (Gfi, Gfn).
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FI20215806A FI130856B1 (en) | 2021-07-14 | 2021-07-14 | Method and apparatus for eliminating voltage distortion in electricity distribution network |
FI20215806 | 2021-07-14 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2023285730A1 true WO2023285730A1 (en) | 2023-01-19 |
Family
ID=84919617
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/FI2022/050426 WO2023285730A1 (en) | 2021-07-14 | 2022-06-17 | Method and apparatus for eliminating voltage distortion in electricity distribution network |
Country Status (2)
Country | Link |
---|---|
FI (1) | FI130856B1 (en) |
WO (1) | WO2023285730A1 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN117388569A (en) * | 2023-12-11 | 2024-01-12 | 浙江宏仁电气有限公司 | Electric energy metering method, electric energy metering box and medium under waveform distortion of power grid |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6075350A (en) * | 1998-04-24 | 2000-06-13 | Lockheed Martin Energy Research Corporation | Power line conditioner using cascade multilevel inverters for voltage regulation, reactive power correction, and harmonic filtering |
US20110260701A1 (en) * | 2008-12-29 | 2011-10-27 | Hoerger Wolfgang | Multilevel Converter as Reactive Power Compensator Having Active Power Symmetrization |
-
2021
- 2021-07-14 FI FI20215806A patent/FI130856B1/en active
-
2022
- 2022-06-17 WO PCT/FI2022/050426 patent/WO2023285730A1/en active Application Filing
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6075350A (en) * | 1998-04-24 | 2000-06-13 | Lockheed Martin Energy Research Corporation | Power line conditioner using cascade multilevel inverters for voltage regulation, reactive power correction, and harmonic filtering |
US20110260701A1 (en) * | 2008-12-29 | 2011-10-27 | Hoerger Wolfgang | Multilevel Converter as Reactive Power Compensator Having Active Power Symmetrization |
Non-Patent Citations (2)
Title |
---|
HIROFUMI AKAGI, HIDEAKI FUJITA, KEIJI WADA: "A Shunt Active Filter Based on Voltage Detection for Harmonic Termination of a Radial Power Distribution Line", IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS., IEEE SERVICE CENTER, PISCATAWAY, NJ., US, vol. 35, no. 3, 1 June 1999 (1999-06-01), US , XP011022563, ISSN: 0093-9994 * |
TZUNG-LIN LEE ; SHANG-HUNG HU: "Design of resonant current regulation for discrete frequency tuning active filter", 2010 INTERNATIONAL POWER ELECTRONICS CONFERENCE : IPEC-SAPPORO 2010 - [ECCE ASIA] ; SAPPORO, JAPAN., IEEE, PISCATAWAY, NJ, USA, 21 June 2010 (2010-06-21), Piscataway, NJ, USA , pages 2271 - 2275, XP031728324, ISBN: 978-1-4244-5394-8 * |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN117388569A (en) * | 2023-12-11 | 2024-01-12 | 浙江宏仁电气有限公司 | Electric energy metering method, electric energy metering box and medium under waveform distortion of power grid |
CN117388569B (en) * | 2023-12-11 | 2024-03-01 | 浙江宏仁电气有限公司 | Electric energy metering method, electric energy metering box and medium under waveform distortion of power grid |
Also Published As
Publication number | Publication date |
---|---|
FI130856B1 (en) | 2024-04-26 |
FI20215806A1 (en) | 2023-01-15 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US7301787B2 (en) | Active type harmonic suppression apparatus | |
US5345377A (en) | Harmonic controller for an active power line conditioner | |
RU2340075C1 (en) | Mode of transform circuit operation and related device for implementation thereof | |
Klempka | A new method for the C-type passive filter design | |
WO2023285730A1 (en) | Method and apparatus for eliminating voltage distortion in electricity distribution network | |
US5805032A (en) | Electrical filter for attenuating oscillations in AC mains | |
US5691626A (en) | Active damping control for active power filter | |
KR101819672B1 (en) | Power compensating apparatus including active dc-link circuit and method for compensating power using active dc-link circuit | |
Mboving et al. | Different approaches for designing the passive power filters | |
Khoor et al. | Simplified analogical control of a unified power quality conditioner | |
Unnikrishnan et al. | Hybrid series active power filter for mitigating power quality problems | |
CN113765348B (en) | High-voltage power supply and medical imaging equipment | |
Cheepati et al. | Performance analysis of double tuned passive filter for power quality | |
Pashajavid et al. | Efficient procedures to design and characterize passive harmonic filters in low power applications | |
Frisfelds et al. | Design of a three-phase bidirectional PWM rectifier with simple control algorithm | |
KR101039310B1 (en) | Hybrid Active Power Filter | |
Kumar et al. | Fuzzy logic controlled hybrid filter for power quality improvement | |
Zhuo et al. | Study on a control method of PAPF for resonance damping and harmonics compensation in power system | |
JP2003102127A (en) | Method for controlling active filter apparatus | |
Aravena et al. | Passive filters for high power cycloconverter grinding mill drives | |
Voncilă et al. | The influence of the connecting elements of the three-phase shunt active filters-in the Common Network Connection Point-on the efficiency of the filtering process | |
Yasin et al. | Adaptive Fuzzy Logic Control of Hybrid, Active Power Filters, for Harmonic Mitigation | |
CN114142718B (en) | Active power factor correction circuit, switching power supply and vehicle | |
Wu et al. | A novel control method of PAPF for resonance damping and harmonics compensation in power system | |
Adebisi et al. | Assessing the Performance of Harmonic Filters for Power Quality Improvement on Industrial Load: 7-Up Industry Plc Power Network as a Case Study |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
121 | Ep: the epo has been informed by wipo that ep was designated in this application |
Ref document number: 22841552 Country of ref document: EP Kind code of ref document: A1 |
|
WWE | Wipo information: entry into national phase |
Ref document number: 2022841552 Country of ref document: EP |
|
NENP | Non-entry into the national phase |
Ref country code: DE |
|
ENP | Entry into the national phase |
Ref document number: 2022841552 Country of ref document: EP Effective date: 20240214 |