Power line harmonic reduction by hybrid parallel active/passive filter system with square wave inverter and DC bus control
First Claim
1. A hybrid active/passive filter system for harmonic isolation of a power supply providing a supply voltage and a supply current to a load, comprising:
- (a) a passive filter;
(b) an active filter inverter connected in series with the passive filter, the series connected active and passive filters adapted to be connected at a filter terminal in parallel with the load, the active filter inverter responsive to control signals to generate an inverter voltage signal in series with the passive filter; and
(c) an active filter harmonic controller means for generating control signals that are applied to the active filter inverter to control the active filter inverter to generate an inverter voltage signal such that a filter terminal voltage tracks the supply voltage at a selected dominant harmonic frequency to regulate the supply current at the selected dominant harmonic frequency to approximately zero.
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Accused Products
Abstract
A hybrid parallel active/passive filter system is provided which provides line power harmonic isolation and compensation for power systems connected to high power non-linear loads. The hybrid filter includes a passive filter connected in series with an active filter inverter. The active filter inverter is controlled to generate inverter voltages such that the filter terminal voltage tracks the supply voltage harmonics at a selected dominant harmonic frequency to regulate the supply current harmonics to zero. A synchronous reference frame (SRF) based controller is used to generate harmonic inverter voltage commands based on measured supply current values. A feed forward command signal generator may be used to improve the response of the control system. The active filter inverter is preferably implemented as a square-wave inverter. The active filter inverter DC bus is controlled to achieve power balancing and to provide real power to compensate for losses of the inverter. Power balancing is achieved by exchanging energy at the fundamental and dominant harmonic frequency of the active filter inverter. Control of the active filter inverter to achieve DC bus control and harmonic isolation simultaneously is accomplished using DC bus control inverter voltage command signals generated at the fundamental frequency in combination with harmonic inverter voltage command carrier signals at the dominant harmonic frequency to form low frequency switching signals for the square-wave inverter switching devices.
94 Citations
54 Claims
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1. A hybrid active/passive filter system for harmonic isolation of a power supply providing a supply voltage and a supply current to a load, comprising:
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(a) a passive filter; (b) an active filter inverter connected in series with the passive filter, the series connected active and passive filters adapted to be connected at a filter terminal in parallel with the load, the active filter inverter responsive to control signals to generate an inverter voltage signal in series with the passive filter; and (c) an active filter harmonic controller means for generating control signals that are applied to the active filter inverter to control the active filter inverter to generate an inverter voltage signal such that a filter terminal voltage tracks the supply voltage at a selected dominant harmonic frequency to regulate the supply current at the selected dominant harmonic frequency to approximately zero. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A hybrid active/passive filter system for harmonic isolation of a power supply providing a supply voltage and a supply current to a load, comprising:
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(a) a passive filter; (b) an active filter inverter connected in series with the passive filter, the series connected active and passive filters adapted to be connected at a filter terminal in parallel with the load, the active filter inverter responsive to control signals to generate an inverter voltage signal in series with the passive filter; and (c) an active filter harmonic controller means including a synchronous reference frame based controller for generating control signals that are applied to the active filter inverter to control the active filter inverter to generate an inverter voltage signal such that a filter terminal voltage tracks the supply voltage at a selected dominant harmonic frequency to regulate the supply current at the selected dominant harmonic frequency to approximately zero. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A hybrid active/passive filter system for harmonic isolation of a power supply providing a supply voltage and a supply current to a load, comprising:
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(a) a passive filter; (b) an active filter inverter connected in series with the passive filter, the series connected active and passive filters adapted to be connected at a filter terminal in parallel with the load, the active filter inverter responsive to control signals to generate an inverter voltage signal in series with the passive filter; and (c) an active filter harmonic controller means including a digital signal processor for generating control signals that are applied to the active filter inverter to control the active filter inverter to generate an inverter voltage signal such that a filter terminal voltage tracks the supply voltage at a selected dominant harmonic frequency to regulate the supply current at the selected dominant harmonic frequency to approximately zero.
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21. A hybrid active/passive filter system for harmonic isolation of a power supply providing a supply voltage and a supply current to a load, comprising:
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(a) a passive filter; (b) a square wave active filter inverter including a DC bus connected in series with the passive filter, the series connected active and passive filters adapted to be connected at a filter terminal in parallel with the load, the active filter inverter responsive to control signals to generate an inverter voltage signal in series with the passive filter; and (c) a synchronous reference frame based active filter harmonic and DC bus control controller means for generating control signals that are applied to the active filter inverter to control the active filter inverter to generate an inverter voltage signal such that the filter terminal voltage tracks the supply voltage at a selected dominant harmonic frequency to regulate the supply current at the selected dominant harmonic frequency to approximately zero and to achieve power balancing of the DC bus by exchanging energy at a fundamental frequency and at the selected dominant harmonic frequency. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29, 30, 31)
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32. An active filter system with DC bus control to provide harmonic compensation at a selected dominant harmonic frequency to a power supply connected to a non-linear load, comprising:
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(a) an active filter inverter responsive to control signals to generate an inverter voltage signal, the active filter inverter having a DC bus; and (b) an active filter harmonic and DC bus controller means for generating control signals that are applied to the active filter inverter to control the active filter inverter to generate an inverter voltage signal to provide harmonic compensation at the selected dominant harmonic frequency and to achieve power balancing of the DC bus by exchanging energy at a fundamental frequency and at the selected dominant harmonic frequency.
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33. An active filter system with DC bus control to provide harmonic compensation at a selected dominant harmonic frequency to a power supply connected to a non-linear load, comprising:
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(a) an active filter inverter responsive to control signals to generate an inverter voltage signal, the active filter inverter having a DC bus; (b) an active filter harmonic and DC bus controller means for generating control signals that are applied to the active filter inverter to control the active filter inverter to generate an inverter voltage signal to provide harmonic compensation at the selected dominant harmonic frequency and to achieve power balancing of the DC bus by exchanging energy at a fundamental frequency and at the selected dominant harmonic frequency; and (c) a passive filter connected in series with the active filter inverter, the series connected active and passive filters adapted to be connected at a filter terminal in parallel with the load, and wherein the active filter controller means includes means for generating control signals that are applied to the active filter inverter to control the active filter inverter to generate an inverter voltage signal in series with the passive filter such that a load terminal voltage tracks a supply voltage at the selected dominant harmonic frequency to regulate a supply current at the selected dominant harmonic frequency to approximately zero.
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34. An active filter system with DC bus control to provide harmonic compensation at a selected dominant harmonic frequency to a power supply connected to a non-linear load, comprising:
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(a) an active filter inverter responsive to control signals to generate an inverter voltage signal, the active filter inverter having a DC bus; and (b) an active filter harmonic and DC bus controller means including a synchronous reference frame based controller for generating control signals that are applied to the active filter inverter to control the active filter inverter to generate an inverter voltage signal to provide harmonic compensation at the selected dominant harmonic frequency and to achieve power balancing of the DC bus by exchanging energy at a fundamental frequency and at the selected dominant harmonic frequency. - View Dependent Claims (35, 36)
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37. An active filter system with DC bus control to provide harmonic compensation at a selected dominant harmonic frequency to a power supply connected to a non-linear load, comprising:
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(a) an active filter inverter responsive to control signals to generate an inverter voltage signal, the active filter inverter having a DC bus; and (b) an active filter harmonic and DC bus controller means including a digital signal processor for generating control signals that are applied to the active filter inverter to control the active filter inverter to generate an inverter voltage signal to provide harmonic compensation at the selected dominant harmonic frequency and to achieve power balancing of the DC bus by exchanging energy at a fundamental frequency and at the selected dominant harmonic frequency.
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38. A method for providing harmonic isolation of a power supply providing a supply voltage and a supply current to a load, comprising the steps of:
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(a) connecting a passive filter in parallel with the load; and (b) generating a voltage signal in series with the passive filter such that a load terminal voltage tracks the supply voltage at a selected dominant harmonic frequency to regulate the supply current at the selected dominant harmonic frequency to approximately zero. - View Dependent Claims (39, 40, 41, 42, 43)
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44. A method for providing harmonic isolation of a power supply providing a supply voltage and a supply current to a load, comprising the steps of:
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(a) connecting a passive filter in parallel with the load; (b) connecting an active filter inverter in series with the passive filter; and (c) controlling the active filter to generate a voltage signal in series with the passive filter such that a load terminal voltage tracks the supply voltage at a selected dominant harmonic frequency to regulate the supply current at the selected dominant harmonic frequency to approximately zero by transforming measured three-phase supply current signals into two-phase synchronously rotating reference frame signal values at the selected dominant harmonic frequency; extracting a DC component corresponding to the supply current component at the selected dominant harmonic frequency from the two-phase signals; comparing the extracted supply current component at the selected dominant harmonic frequency to supply current reference command signals to form supply current harmonic error signals; deriving two-phase harmonic inverter voltage command signals from the supply current harmonic error signals; and transforming the two-phase harmonic inverter voltage command signals from the two-phase synchronously rotating reference frame to the three-phase reference frame to form three-phase harmonic inverter voltage command signals. - View Dependent Claims (45, 46, 47, 48, 49, 50, 51, 52, 53)
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54. A hybrid active/passive filter system for harmonic isolation of a power supply providing a supply voltage and a supply current to a load, comprising:
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(a) a passive filter that is mis-tuned to a frequency near a selected dominant harmonic frequency; (b) an active filter inverter in series with the passive filter, the series connected active and passive filters adapted to be connected at a filter terminal in parallel with the load, the active filter inverter responsive to control signals to generate an inverter voltage signal in series with the passive filter; and (c) an active filter harmonic controller means for generating control signals that are applied to the active filter inverter to control the active filter inverter to generate an inverter voltage signal such that a filter terminal voltage tracks the supply voltage at the selected dominant harmonic frequency to thereby effectively tune the passive filter to the selected dominant harmonic frequency.
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Specification