US6657322B2 — Control system for active power filters

Claim 1

Independent Claim 177 words

A filter for eliminating harmonic currents from three phase AC supply lines, the AC lines providing actual voltage waveforms and corresponding actual current waveforms including fundamental components and harmonic components flowing through the lines connected to a load, the actual voltage waveforms characterized by a peak value the filter comprising: current sensors linked to the lines to provide three phase current signals indicating the actual line current waveforms; a compensator for providing compensating harmonic signals on the lines as a function of control signals, the compensator including a DC bus voltage source that is charged by current sinked from the lines, the DC source characterized by a minimum charge value that is greater than the peak value; a voltage sensor linked to the DC bus voltage source to provide a voltage signal indicating the DC bus voltage; and a controller for generating the control signals as a function of the actual line current waveforms and the DC voltage difference where the DC voltage difference is the difference between the DC bus voltage and the minimum charge value.

Claim 2

Dependent Claim 177 words

A filter for eliminating harmonic currents from three phase AC supply lines, the AC lines providing actual voltage waveforms and corresponding actual current waveforms including fundamental components and harmonic components flowing through the lines connected to a load, the actual voltage waveforms characterized by a peak value the filter comprising: current sensors linked to the lines to provide three phase current signals indicating the actual line current waveforms; a compensator for providing compensating harmonic signals on the lines as a function of control signals, the compensator including a DC bus voltage source that is charged by current sinked from the lines, the DC source characterized by a minimum charge value that is greater than the peak value; a voltage sensor linked to the DC bus voltage source to provide a voltage signal indicating the DC bus voltage; and a controller for generating the control signals as a function of the actual line current waveforms and the DC voltage difference where the DC voltage difference is the difference between the DC bus voltage and the minimum charge value.

Claim 3

Dependent Claim 44 words

The filter of claim 1 wherein the controller runs a pulse sequencing program to determine the power associated with the actual current waveforms, modifies the power as a function of the DC difference and uses the modified power signals to generate the control signals.

Claim 4

Dependent Claim 154 words

The filter of claim 2 wherein the controller runs the program to determine the power by converting the three phase currents to two phase currents and using the two phase currents to identify both real and imaginary average reactive power components and both real and imaginary average resistive power components, the controller runs the program to modify the power by identifying a DC bus factor that is a function of the DC difference, mathematically combining the DC bus factor and one of the real and imaginary power components to generate adjusted power signals and the controller runs the program to generate the control signals by deriving effective sine wave currents from the adjusted power signals, subtracting the effective sine wave currents from the actual currents to generate two phase harmonic current signals, transforming the two phase harmonic current signals to three phase harmonic current signals and providing the three phase signals as control signals.

Claim 5

Dependent Claim 27 words

The filter of claim 3 wherein the controller runs the program to identify the bus factor by stepping up the bus DC difference via a PI regulator.

Claim 6

Dependent Claim 55 words

The filter of claim 4 wherein the filter is a hybrid shunt active filter and wherein the controller runs the program to mathematically combine by converting the bus factor into imaginary reactive and resistive bus factor components and adding the imaginary reactive and resistive bus factor components to imaginary reactive and resistive line power components.

Claim 7

Dependent Claim 79 words

The filter of claim 5 wherein the controller runs the program to mathematically combine by solving the following equations: Δ Q α =ΔQ· ( Q α /{square root over ( Q α 2 +Q β 2 )}) Δ Q β =ΔQ· ( Q β /{square root over (Q α 2 +Q β 2 )}) where Q α is the imaginary resistive power line component, Q β is the imaginary reactive power line component and ΔQ is the bus factor.

Claim 8

Dependent Claim 55 words

The filter of claim 4 wherein the filter is a pure shunt active filter and wherein the controller runs the program to mathematically combine by converting the bus factor into real reactive and resistive bus factor components and adding the real reactive and resistive bus factor components to real reactive and resistive line power components.

Claim 9

Dependent Claim 80 words

The filter of claim 7 wherein the controller runs the program to mathematically combine by solving the following equations: Δ P α =ΔP ·( P α /{square root over ( P α 2 +P β 2 )}) Δ P β =ΔP ·( P β /{square root over ( P α 2 +P β 2 )}) where P α is the real resistive power line component, P β is the real reactive power line component and ΔP is the bus factor.

Claim 10

Dependent Claim 59 words

The filter of claim 1 wherein the current sensor provides periodic current magnitude signals and wherein the controller runs a pulse sequencing program to use recent magnitude signals to determine an estimated next magnitude signal and generates the control signals as a function of the actual line current waveforms, the DC voltage difference ad the estimated next magnitude signal.

Claim 11

Dependent Claim 23 words

The filter of claim 9 wherein the controller determines the estimated next magnitude signal by extrapolating form the most recent three current samples.

Claim 12

Dependent Claim 152 words

A filter for eliminating harmonic currents from three phase AC supply lines, the AC lines providing actual voltage waveforms and corresponding actual current waveforms including fundamental components and harmonic components flowing through the lines connected to a load, the actual voltage waveforms characterized by a peak value the filter comprising: current sensors linked to the lines to provide three phase current signals indicating the actual line current waveforms; an extrapolator receiving the current signals and identifying an estimated next current magnitude for each of the current signals; a controller for receiving the current signals and the estimated next current magnitudes and using the signals and estimates to determine a harmonic-less current waveform matching the power characteristics of the actual current waveform, the controller generating control signals as a function of the harmonic-less current waveform; and a compensator for providing compensating harmonic signals on the lines as a function of the control signal.

Claim 13

Dependent Claim 152 words

A filter for eliminating harmonic currents from three phase AC supply lines, the AC lines providing actual voltage waveforms and corresponding actual current waveforms including fundamental components and harmonic components flowing through the lines connected to a load, the actual voltage waveforms characterized by a peak value the filter comprising: current sensors linked to the lines to provide three phase current signals indicating the actual line current waveforms; an extrapolator receiving the current signals and identifying an estimated next current magnitude for each of the current signals; a controller for receiving the current signals and the estimated next current magnitudes and using the signals and estimates to determine a harmonic-less current waveform matching the power characteristics of the actual current waveform, the controller generating control signals as a function of the harmonic-less current waveform; and a compensator for providing compensating harmonic signals on the lines as a function of the control signal.

Claim 14

Dependent Claim 33 words

The filter of claim 11 wherein the current sensor provides periodic current signals and wherein, for each line, the extrapolator combines the most recent three current signals to determine the estimated next signal.

Claim 15

Independent Claim 170 words

A method for eliminating harmonic currents from three phase AC supply lines, the AC lines providing actual voltage waveforms and corresponding actual current waveforms including fundamental components and harmonic components flowing through the lines connected to a load, the actual voltage waveforms characterized by a peak value, the method comprising the steps of: sensing the currents on the three lines to generate phase current signals indicating the actual line current waveforms; providing a compensator for providing compensating harmonic signals on the lines as a function of control signals, the compensator including a DC bus voltage source that is charged by current sinked from the lines, the DC source characterized by a minimum charge value that is greater than the peak value; sensing the DC bus voltage and providing a DC bus voltage signal; and generating the control signals as a function of the actual line current waveforms and the DC voltage difference where the DC voltage difference is the difference between the DC bus voltage and the minimum charge value.

Claim 16

Independent Claim 170 words

A method for eliminating harmonic currents from three phase AC supply lines, the AC lines providing actual voltage waveforms and corresponding actual current waveforms including fundamental components and harmonic components flowing through the lines connected to a load, the actual voltage waveforms characterized by a peak value, the method comprising the steps of: sensing the currents on the three lines to generate phase current signals indicating the actual line current waveforms; providing a compensator for providing compensating harmonic signals on the lines as a function of control signals, the compensator including a DC bus voltage source that is charged by current sinked from the lines, the DC source characterized by a minimum charge value that is greater than the peak value; sensing the DC bus voltage and providing a DC bus voltage signal; and generating the control signals as a function of the actual line current waveforms and the DC voltage difference where the DC voltage difference is the difference between the DC bus voltage and the minimum charge value.

Claim 17

Dependent Claim 46 words

The method of claim 13 wherein the step of generating control signals includes the steps of determining the power associated with the actual current waveforms, modifying the power as a function of the DC difference and using the modified power signals to generate the control signals.

Claim 18

Dependent Claim 148 words

The method of claim 14 wherein the step of determining the power includes the steps of converting the three phase currents to two phase currents and using the two phase currents to identify both real and imaginary average reactive power components and both real and imaginary average resistive power components, the step of modifying the power includes identifying a DC bus factor that is a function of the DC difference, mathematically combining the DC bus factor and one of the real and imaginary power components to generate adjusted power signals and the step of generating the control signals includes deriving effective sine wave currents from the adjusted power signals, subtracting the effective sine wave currents from the actual currents to generate two phase harmonic current signals, transforming the two phase harmonic current signals to three phase harmonic current signals and providing the three phase signals as control signals.

Claim 19

Dependent Claim 52 words

The method of claim 15 wherein the filter is a hybrid shunt active filter and wherein the step of mathematically combining includes converting the bus factor into imaginary reactive and resistive bus factor components and adding the imaginary reactive and resistive bus factor components to imaginary reactive and resistive line power components.

Claim 20

Dependent Claim 52 words

The method of claim 15 wherein the filter is a pure shunt active filter and wherein the step of mathematically combining includes converting the bus factor into real reactive and resistive bus factor components and adding the real reactive and resistive bus factor components to real reactive and resistive line power components.

Claim 21

Dependent Claim 59 words

The method of claim 11 wherein the current sensor provides periodic current magnitude signals and wherein the controller runs a pulse sequencing program to use recent magnitude signals to determine an estimated next magnitude signal and generates the control signals as a function of the actual line current waveforms, the DC voltage difference and the estimated next magnitude signal.

Claim 22

Independent Claim 184 words

A method for eliminating harmonic currents from three phase AC supply lines, the AC lines providing actual voltage waveforms and corresponding actual current waveforms including fundamental components and harmonic components flowing through the lines connected to a load, the actual voltage waveforms characterized by a peak value, the method comprising the steps of: sensing the currents on the three lines to generate phase current signals indicating the actual line current waveforms; identifying an estimated next current magnitude for each of the current signals; providing a compensator for providing compensating harmonic signals on the lines as a function of control signals, the compensator including a DC bus voltage source that is charged by current sinked from the lines, the DC source characterized by a minimum charge value that is greater than the peak value; using the current signals and the estimated next current magnitudes to determine a harmonic-less current waveform matching the power characteristics of the actual current waveform; generating control signals as a function of the harmonic-less current waveform; and providing compensating harmonic signals on the lines as a function of the control signal.

Claim 23

Independent Claim 184 words

A method for eliminating harmonic currents from three phase AC supply lines, the AC lines providing actual voltage waveforms and corresponding actual current waveforms including fundamental components and harmonic components flowing through the lines connected to a load, the actual voltage waveforms characterized by a peak value, the method comprising the steps of: sensing the currents on the three lines to generate phase current signals indicating the actual line current waveforms; identifying an estimated next current magnitude for each of the current signals; providing a compensator for providing compensating harmonic signals on the lines as a function of control signals, the compensator including a DC bus voltage source that is charged by current sinked from the lines, the DC source characterized by a minimum charge value that is greater than the peak value; using the current signals and the estimated next current magnitudes to determine a harmonic-less current waveform matching the power characteristics of the actual current waveform; generating control signals as a function of the harmonic-less current waveform; and providing compensating harmonic signals on the lines as a function of the control signal.

Claim 24

Dependent Claim 36 words

The method of claim 19 wherein the current sensor provides periodic current signals and wherein, for each line, the step of identifying includes combining the most recent three current signals to determine the estimated next signal.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	2006-12-01	2007-06-02	2007-12-02	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2010-12-01	2011-06-02	2011-12-02	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2014-12-01	2015-06-02	2015-12-02	$7700.00	Window Closed / Lapsed

Control system for active power filters

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