Active filter for reducing non-fundamental currents and voltages
First Claim
Patent Images
1. An active filter connected to a power line between a power source providing power at a fundamental frequency and a load, the active filter comprising:
- current sensing means connected to the power line for sensing the current flowing to the load and providing a current sense signal representative of the sensed current;
voltage sensing means connected to the power line for sensing the voltage on the power line and for providing a voltage sense signal representative of the sensed voltage;
filtering means for filtering the fundamental frequency out of the current sense signal and for filtering the fundamental frequency out of the voltage sense signal; and
current generating means for providing a first current to the power line in response to the filtered current sense signal and a second current to the power line in response to the filtered voltage sense signal.
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Abstract
An AC power line is monitored for currents and voltages at non-fundamental frequencies (including harmonics). A controlled active filter injects compensating current into the AC power line. The injected compensating current is responsive to both the sensed non-fundamental frequency current and to the sensed non-fundamental frequency voltage residing on the power line. In one embodiment, the controlled active filter comprises a transconductance amplifier which obtains its operating power from a controlled flow of power from the AC power line being monitored.
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Citations
26 Claims
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1. An active filter connected to a power line between a power source providing power at a fundamental frequency and a load, the active filter comprising:
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current sensing means connected to the power line for sensing the current flowing to the load and providing a current sense signal representative of the sensed current; voltage sensing means connected to the power line for sensing the voltage on the power line and for providing a voltage sense signal representative of the sensed voltage; filtering means for filtering the fundamental frequency out of the current sense signal and for filtering the fundamental frequency out of the voltage sense signal; and current generating means for providing a first current to the power line in response to the filtered current sense signal and a second current to the power line in response to the filtered voltage sense signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. An active filter connected to a power line between a power source providing power at a fundamental frequency and a load, the active filter comprising:
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a current sensor connected to the power line which provides a current sense signal proportional to the current on the power line; a voltage sensor connected to the power line which provides a voltage sense signal proportional to the voltage on the power line; a fundamental frequency filter which receives the current sense signal and the voltage sense signal, filters the fundamental frequency from the signals and provides a filtered current sense signal and a filtered voltage sense signal; and a current generator connected to the power line at a location closer to the power source than the current sensor and connected to the fundamental frequency filter and which provides a first current to the power line in response to the filtered current sense signal and a second current to the power line in response to the filtered voltage sense signal, the first and second currents being provided at the point at which the voltage sensor senses the voltage on the power line. - View Dependent Claims (12, 13, 14, 15, 16, 17)
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18. A method of providing current to a power line connected between a power source providing power having a fundamental frequency and a load, comprising the steps of:
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sensing the current on the power line flowing to the load and providing a current sense signal representative of the sensed current; sensing the voltage on the power line and providing a voltage sense signal representative of the sensed voltage; filtering the fundamental frequency from the current sense signal and from the voltage sense signal; and injecting a first current into the power line in response to the filtered current sense signal and injecting a second current into the power line in response to the filtered voltage sense signal. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26)
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Specification