US6239997B1 — System for connecting and synchronizing a supplem…

Claim 1

Independent Claim 106 words

A method for connecting a supplemental power supply having three-phase output voltages to a power grid having three-phase grid voltages, the supplemental power supply having a DC power source, an electronic inverter, a controller, a three-phase AC line filter and a three-phase circuit contactor, said method comprising the steps of: detecting the three-phase grid voltages; converting the three-phase grid voltages into voltages on a d-q plane; detecting the three-phase output voltages of the supplemental power supply; converting the detected output voltages into voltages on a d-q plane; determining a voltage command to control the three-phase output voltages as close as possible to the three-phase grid voltages.

Claim 2

Independent Claim 106 words

A method for connecting a supplemental power supply having three-phase output voltages to a power grid having three-phase grid voltages, the supplemental power supply having a DC power source, an electronic inverter, a controller, a three-phase AC line filter and a three-phase circuit contactor, said method comprising the steps of: detecting the three-phase grid voltages; converting the three-phase grid voltages into voltages on a d-q plane; detecting the three-phase output voltages of the supplemental power supply; converting the detected output voltages into voltages on a d-q plane; determining a voltage command to control the three-phase output voltages as close as possible to the three-phase grid voltages.

Claim 3

Dependent Claim 37 words

The method as claimed in claim 1 further comprising the step of controlling the output voltages of the supplemental power supply in magnitude and phase angle for synchronization of the supplemental power supply and the power grid.

Claim 4

Dependent Claim 49 words

The method as claimed in claim 1 wherein said step of converting said grid voltages into voltages on a d-q plane further comprises the steps of: converting the detected grid voltages to a rotating vector on an α-β plane; and deriving a rotating angle from said grid voltage vector.

Claim 5

Dependent Claim 36 words

The method as claimed in claim 3 wherein said step of converting the three-phase output voltages into voltages on a d-q plane further comprises the steps of converting the detected output voltages into a rotating vector.

Claim 6

Dependent Claim 45 words

The method as claimed in claim 1 wherein said step of detecting the grid voltages further comprises detecting the grid voltages with a y-connected resistor network and the step of detecting the output voltages further comprise detecting the output voltages with a y-connected resistor network.

Claim 7

Dependent Claim 43 words

The method as claimed in claim 1 wherein said step of detecting the grid voltages further comprises detecting the grid voltages with a y-connected transformer and the step of detecting the output voltages further comprise detecting the output voltages with a y-connected transformer.

Claim 8

Dependent Claim 27 words

The method as claimed in claim 1 further comprising the step of calculating the change in a rotating angle over time to determine a rotating angle frequency.

Claim 9

Dependent Claim 28 words

The method as claimed in claim 7 further comprising the step of determining a phase sequence for the grid voltage from the sign of said rotating angle frequency.

Claim 10

Independent Claim 347 words

A method for connecting a supplemental power supply having three-phase output voltages, U a — p , U b — p , and U c — p , to a power grid having three-phase grid voltages, U a — g , U b — g , and U c — g , the supplemental power supply having a DC power source, an electronic inverter, a controller, a three-phase AC line filter and a three-phase circuit contactor, said method comprising the steps of: detecting the three-phase grid voltages, U a — g , U b — g , and U c — g ; converting the detected grid voltages to a rotating vector, U α — g , U β — g , on an α-β. plane; deriving a rotating angle, γ u — g , from said grid voltage vector; converting said grid voltage vector into three-phase voltages on a d-q plane according to: U d — g =U α — g *cos γ u — g −U β — g *sin γ u — g , and U q — g =U α — g *sin γ u — g +U β — g *cos γ u — g ; detecting the three-phase output voltages of the supplemental power supply; converting the detected output voltages to an output rotating vector, U α — p , U β — p ; converting said output rotating vector in three-phase voltages on a d-q plane according to: U d — p =U α — p *cos γ u — g −U β — p *sin γ u — g , and U q — p =U α — p *sin γ u — g +U β — p *cos γ u — g ; determining a voltage command, U d — com , U q — com , to control the three-phase output voltages as close as possible to said three-phase grid voltages; and controlling the output voltages of the supplemental power supply in magnitude and phase angle for synchronization of the supplemental power supply and the power grid.

Claim 11

Independent Claim 347 words

A method for connecting a supplemental power supply having three-phase output voltages, U a — p , U b — p , and U c — p , to a power grid having three-phase grid voltages, U a — g , U b — g , and U c — g , the supplemental power supply having a DC power source, an electronic inverter, a controller, a three-phase AC line filter and a three-phase circuit contactor, said method comprising the steps of: detecting the three-phase grid voltages, U a — g , U b — g , and U c — g ; converting the detected grid voltages to a rotating vector, U α — g , U β — g , on an α-β. plane; deriving a rotating angle, γ u — g , from said grid voltage vector; converting said grid voltage vector into three-phase voltages on a d-q plane according to: U d — g =U α — g *cos γ u — g −U β — g *sin γ u — g , and U q — g =U α — g *sin γ u — g +U β — g *cos γ u — g ; detecting the three-phase output voltages of the supplemental power supply; converting the detected output voltages to an output rotating vector, U α — p , U β — p ; converting said output rotating vector in three-phase voltages on a d-q plane according to: U d — p =U α — p *cos γ u — g −U β — p *sin γ u — g , and U q — p =U α — p *sin γ u — g +U β — p *cos γ u — g ; determining a voltage command, U d — com , U q — com , to control the three-phase output voltages as close as possible to said three-phase grid voltages; and controlling the output voltages of the supplemental power supply in magnitude and phase angle for synchronization of the supplemental power supply and the power grid.

Claim 12

Dependent Claim 45 words

The method as claimed in claim 9 wherein said step of detecting the grid voltages further comprises detecting the grid voltages with a y-connected resistor network and the step of detecting the output voltages further comprise detecting the output voltages with a y-connected resistor network.

Claim 13

Dependent Claim 43 words

The method as claimed in claim 9 wherein said step of detecting the grid voltages further comprises detecting the grid voltages with a y-connected transformer and the step of detecting the output voltages further comprise detecting the output voltages with a y-connected transformer.

Claim 14

Dependent Claim 37 words

The method as claimed in claim 9 further comprising the step of calculating the change in said rotating angle γ u — g , over time to determine a rotating angle frequency ω u — g .

Claim 15

Dependent Claim 28 words

The method as claimed in claim 12 further comprising the step of determining a phase sequence for the grid voltage from the sign of said rotating angle frequency.

Claim 16

Dependent Claim 170 words

The method as claimed in claim 9 wherein the supplemental power supply has a first and a second voltage regulator, said step of determining a voltage command further comprises the steps of: supplying said grid voltages on the d-q plane as references to the first and second voltage regulators; supplying said output voltages of the supplemental power supply on the d-q plane as feedback to the first and second voltage regulators; determining an error signal, U d — err , as the difference between the reference voltage U d — g and the feedback voltage U d — p ; determining an error signal, U q — err , as the difference between the reference voltage U q — g and the feedback voltage U q — p ; summing U d — g and U d — err to determine said command voltage U d — com ; and summing U q — g and U q — err to determine said command voltage U q — com .

Claim 17

Dependent Claim 98 words

The method as claimed in claim 14 wherein said step of controlling the output voltages further comprises the step of calculating reference voltages as: U a — ref =U d — com cos γ u — g −U q — com sin γ u — g U b — ref =U d — com cos(γ u-g −2π/3)+ U q — com sin(γ u-g −2π/3) U b — ref =U d — com cos(γ u-g +2π/3)+ U q — com sin(γ u-g +2π/3) for controlling the output voltages in phase angle, phase sequence, and frequency to follow grid voltages.

Claim 18

Dependent Claim 39 words

The method as claimed in claim 14 wherein said step of controlling the output voltages further comprises: determining when U d — err and U q — err reach a predetermined tolerance, thereby indicating when synchronization has been realized.

Claim 19

Dependent Claim 122 words

The method as claimed in claim 9 wherein the supplemental power supply has a first and second current regulator and current references i d — ref , and i q — ref , said method further comprising the steps of: sensing an output phase current i a and i b for the supplemental power supply; converting said sensed currents into currents on the α-β plane; converting said currents on said α-β plane into currents on the d-q axis; setting the current references to zero during connection of the supplemental power supply to the power grid; and increasing the current references after the supplemental power supply is connected to the power grid, the current references are increased according to a predetermined ramp rate.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	2004-05-28	2004-11-27	2005-05-29	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2008-05-28	2008-11-27	2009-05-29	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2012-05-28	2012-11-27	2013-05-29	$7700.00	Window Closed / Lapsed

System for connecting and synchronizing a supplemental power source to a power grid

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