Hybrid parallel active/passive filter system with dynamically variable inductance
First Claim
1. A parallel hybrid active filter for harmonic compensation of a non-linear load connected to a power supply, comprising:
- (a) a passive filter;
(b) an active filter responsive to control signals connected in series with the passive filter such that the series combination of the passive and active filter is connectable in parallel with the load and power supply;
(c) an active filter controller for generating control signals for controlling the active filter to generate a voltage in series with the passive filter which is orthogonal in phase to a current through the active filter at a selected harmonic frequency to synthesize a dynamically variable inductance at the selected harmonic frequency such that the passive and active filter in combination reduce an amount of harmonic current distortion produced by the load at the selected harmonic frequency that is returned to the power supply and reduce a harmonic voltage distortion at a filter terminal.
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Accused Products
Abstract
A parallel hybrid active filter system for harmonic compensation of large non-linear loads is provided. The hybrid filter includes a passive filter connected in series with an inverter that is controlled to produce a dynamically variable inductance at selected harmonic frequencies. The passive filter may include passive capacitive and inductive elements, or may include a power factor correction capacitor alone, with all the inductance for the hybrid filter provided by the active filter inverter. The active filter inverter is controlled to provide the dynamically variable inductance by a synchronous reference frame (SRF) based controller that generates active filter inverter voltage commands that are fed to a PWM or square wave modulated voltage source inverter (VSI). The SRF controller includes an inductance command generator that generates the inductance value necessary to provide harmonic compensation from measured three phase load and filter currents transformed into a two phase synchronous rotating reference frame. A single inverter may be controlled to implement variable inductances for compensation of multiple harmonic frequencies by superposition of active filter inverter voltage commands from multiple SRF controllers. The active filter inverter is also preferably controlled by a SRF based DC bus controller to provide for maintenance of a DC bus voltage providing power to the inverter without affecting the harmonic compensation of the hybrid filter.
78 Citations
46 Claims
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1. A parallel hybrid active filter for harmonic compensation of a non-linear load connected to a power supply, comprising:
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(a) a passive filter; (b) an active filter responsive to control signals connected in series with the passive filter such that the series combination of the passive and active filter is connectable in parallel with the load and power supply; (c) an active filter controller for generating control signals for controlling the active filter to generate a voltage in series with the passive filter which is orthogonal in phase to a current through the active filter at a selected harmonic frequency to synthesize a dynamically variable inductance at the selected harmonic frequency such that the passive and active filter in combination reduce an amount of harmonic current distortion produced by the load at the selected harmonic frequency that is returned to the power supply and reduce a harmonic voltage distortion at a filter terminal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A parallel hybrid active filter for harmonic compensation of a non-linear load connected to a power supply, comprising:
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(a) a passive filter; (b) an active filter including a voltage source inverter responsive to control signals connected in series with the passive filter such that the series combination of the passive and active filter is connectable in parallel with the load and power supply; (c) a synchronous referenced frame based active filter controller for generating control signals for controlling the active filter to generate a voltage in series with the passive filter to synthesize a dynamically variable inductance at a selected harmonic frequency such that the passive and active filter in combination reduce an amount of harmonic current distortion produced by the load at the selected harmonic frequency that is returned to the power supply and reduce a harmonic voltage distortion at a filter terminal, including means for generating active inductance command signals that define an amount of variable inductance at the selected harmonic frequency based upon a difference between a signal corresponding to a magnitude of a load current at the selected harmonic frequency and a signal corresponding to a magnitude of a current through the hybrid filter at the selected harmonic frequency, and means for generating active filter inverter voltage command signals for controlling the inverter to synthesize the dynamically variable inductance in response to the active inductance command signals. - View Dependent Claims (16)
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17. A parallel hybrid active filter for harmonic compensation of a non-linear load connected to a power supply, comprising:
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(a) a passive filter; (b) an active filter including a voltage source inverter responsive to control signals connected in series with the passive filter such that the series combination of the passive and active filter is connectable in parallel with the load and power supply; (c) a synchronous reference frame based active filter controller for generating control signals for controlling the active filter to generate a voltage in series with the passive filter to synthesize a dynamically variable inductance at a selected harmonic frequency such that the passive and active filter in combination reduce an amount of harmonic current distortion produced by the load at the selected harmonic frequency that is returned to the power supply and reduce a harmonic voltage distortion at a filter terminal, including means for generating an active inductance command signal that defines an amount of variable inductance at the selected harmonic frequency and means for generating active filter inverter voltage command signals including means for generating a signal representative of the derivative of a current through the hybrid filter at the selected harmonic frequency, and for multiplying the active inductance command signal and the signal representative of the derivative of the current through the hybrid filter at the selected harmonic frequency to produce an active inductor voltage command signal that is used to generate the active filter inverter voltage command signals. - View Dependent Claims (18)
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19. A parallel hybrid active filter for harmonic compensation of a non-linear load connected to a power supply, comprising:
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(a) a passive filter; (b) an active filter responsive to control signals including a voltage source inverter that responds to active filter inverter voltage command signals and that is connected in series with the passive filter such that the series combination of the passive and active filter is connectable in parallel with the load and power supply; (c) a synchronous reference frame based active filter controller for generating control signals including means for generating an active inductance command signal that defines an amount of variable inductance and means for generating active filter inverter voltage command signals in response to the active inductance command signal for controlling the active filter voltage source inverter to generate a voltage in series with the passive filter to synthesize a dynamically variable inductance at a selected harmonic frequency such that the passive and active filter in combination reduce an amount of harmonic current distortion produced by the load at the selected harmonic frequency that is returned to the power supply and reduce a harmonic voltage distortion at a filter terminal. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30)
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31. A parallel hybrid active filter for harmonic compensation of a non-linear load connected to a power supply, comprising:
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(a) a passive filter; (b) an active filter including a voltage source inverter having a DC bus capacitor, responsive to control signals, and connected in series with the passive filter such that the series combination of the passive and active filter is connectable in parallel with the load and power supply; (c) a synchronous reference frame based active filter controller for generating control signals for controlling the active filter to generate a voltage in series with the passive filter to synthesize a dynamically variable inductance at a selected harmonic frequency such that the passive and active filter in combination reduce an amount of harmonic current distortion produced by the load at the selected harmonic frequency that is returned to the power supply and reduce a harmonic voltage distortion at a filter terminal, including means for generating active inductance command signals that define an amount of variable inductance at the selected harmonic frequency, and means for generating active filter inverter voltage command signals for controlling the inverter to synthesize the dynamically variable inductance in response to the active inductance command signals; (d) a synchronous reference frame based controller for controlling the inverter to provide bi-directional flow of real power to the DC bus capacitor to maintain a voltage on the DC bus capacitor, including means for generating DC bus controller inverter voltage command signals from a product of the current signal through the hybrid filter at the fundamental frequency and a DC bus voltage command signal derived from a difference between a measured DC bus voltage and a DC bus voltage reference signal; and (e) means for adding the DC bus controller inverter voltage command signals to the active filter inverter voltage command signals.
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32. A parallel hybrid active filter for harmonic compensation of a non-linear load connected to a power supply, comprising:
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(a) a passive filter; (b) an active filter responsive to control signals including a voltage source inverter that responds to active filter inverter voltage command signals and that is connected in series with the passive filter such that the series combination of the passive and active filter is connectable in parallel with the load and power supply; and (c) a synchronous reference frame based active filter controller for generating control signals including means for generating an active inductance command signal that defines an amount of variable inductance, means for generating active filter inverter voltage command signals in response to the active inductance command signal for controlling the active filter voltage source inverter to generate a voltage in series with the passive filter to synthesize a dynamically variable inductance at a selected harmonic frequency such that the passive and active filter in combination reduce an amount of harmonic current distortion produced by the load at the selected harmonic frequency that is returned to the power supply and reduce a harmonic voltage distortion at a filter terminal, and means for adjusting the value of the active inductance command signal such that the active filter inverter voltage command signals generated in response to the active inductance command signal control the active filter to limit an amount of current through the filter to a selected amount of current at the selected harmonic frequency.
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33. A parallel hybrid active filter for harmonic compensation of a non-linear load connected to a power supply, comprising:
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(a) a passive filter; (b) an active filter responsive to control signals including a voltage source inverter having a DC bus capacitor, which responds to active filter inverter voltage command signals, and that is connected in series with the passive filter such that the series combination of the passive and active filter is connectable in parallel with the load and power supply; (c) a synchronous reference frame based active filter controller for generating control signals including means for generating an active inductance command signal that defines an amount of variable inductance and means for generating active filter inverter voltage command signals in response to the active inductance command signal for controlling the active filter voltage source inverter to generate a voltage in series with the passive filter to synthesize a dynamically variable inductance at a selected harmonic frequency such that the passive and active filter in combination reduce an amount of harmonic current distortion produced by the load at the selected harmonic frequency that is returned to the power supply and reduce a harmonic voltage distortion at a filter terminal, including means for generating a signal representative of the derivative of a current through the hybrid filter at the selected harmonic frequency, and for multiplying the active inductance command signal and the signal representative of the derivative of the current through the hybrid filter at the selected harmonic frequency to produce an active inductor voltage command signal that is used to generate the active filter inverter voltage command signals; and (d) a DC bus controller for controlling the inverter to provide bi-directional flow of real power to the DC bus capacitor to maintain a voltage on the DC bus capacitor. - View Dependent Claims (34)
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35. A method for providing harmonic compensation of a non-linear load connected to a power supply, comprising the steps of:
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(a) connecting a passive filter in parallel with the load and power supply; and (b) generating a voltage in series with the passive filter which is orthogonal in phase to a current through the passive filter at a selected harmonic frequency to thereby synthesize a dynamically variable inductance at the selected harmonic frequency such that the passive filter and dynamically variable inductance in combination reduce an amount of harmonic current distortion produced by the load at the selected harmonic frequency that is returned to the power supply. - View Dependent Claims (36, 37, 38, 39)
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40. A method for providing harmonic compensation of a non-linear load connected to a power supply, comprising the steps of:
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(a) connecting a passive filter in parallel with the load and power supply; and (b) generating a voltage in series with the passive filter to synthesize a dynamically variable inductance at a selected harmonic frequency such that the passive filter and dynamically variable inductance in combination reduce an amount of harmonic current distortion produced by the load at the selected harmonic frequency that is returned to the power supply, including the steps of; determining a current through the passive filter at the selected harmonic frequency in a rotating synchronous two phase d-q reference frame; determining a filter current magnitude value corresponding to a magnitude of the current through the filter at the selected harmonic frequency in a rotating synchronous two phase d-q reference frame; determining the current to a load at the selected harmonic frequency in a rotating synchronous two phase d-q reference frame; determining a load current magnitude value corresponding to a magnitude of the current to the load at the selected harmonic frequency in a rotating synchronous two phase d-q reference frame; generating an active inductance command signal that defines an amount of variable inductance at a selected frequency from the difference between the filter current magnitude value and the load current magnitude value; generating a signal corresponding to the derivative of the current through the filter at the selected harmonic frequency; multiplying the active inductance command signal by the signal corresponding to the derivative of the current through the filter at the selected harmonic frequency to form an inductor voltage command signal in the rotating synchronous two phase d-q reference frame; and converting the inductor voltage command signal from the rotating synchronous two phase reference frame to a three phase reference frame to form active filter inverter voltage commands for controlling an inverter to generate the voltage. - View Dependent Claims (41, 42)
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43. A method for controlling a voltage source inverter to synthesize a dynamically variable inductance in response to inverter voltage commands, comprising the steps of:
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(a) determining a current through the inverter at a selected harmonic frequency in a rotating synchronous two phase d-q reference frame; (b) generating an active inductance command that defines an amount of variable inductance; (c) taking the derivative of the current through the inverter at the selected harmonic frequency; (d) multiplying the active inductance command by the derivative of the current through the filter at the selected harmonic frequency to form an inductor voltage command in the rotating synchronous two phase d q reference frame; and (e) converting the inductance voltage command from the rotating synchronous two phase reference frame to a three phase reference frame to form the inverter voltage commands to control the inverter to synthesize the inductance. - View Dependent Claims (44, 45, 46)
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Specification