Synchronous frame regulation to extract a positive sequence component of a line voltage

Claim 2

Apparatus for a power distribution system, the system including a distribution feeder line, the apparatus comprising: an active rectifier; and a controller for the active rectifier, the controller determining a positive sequence component of a Park vector representing line voltage, and using the positive sequence component to perform synchronous frame regulation.

Claim 3

The apparatus of claim 1 , wherein the controller samples the line voltage, samples lying on a locus of the Park vector; predicts major and minor axes of the locus of the Park vector; and extracts a positive sequence from the major and minor axes.

Claim 4

The apparatus of claim 2 , wherein the controller initially determines angle of the positive sequence from the major and minor axes; and wherein the angle is updated at discrete intervals.

Claim 5

The apparatus of claim 3 , wherein the controller updates the angle (α i+1 ) by α i+1 =α m +90° (ΔT)F, where F is the fundamental frequency of the positive sequence, ΔT is the time between samples, and α m is the angle of one of the major and minor axes.

Claim 6

The apparatus of claim 2 , wherein the controller updates the fundamental frequency at regular intervals.

Claim 7

The apparatus of claim 2 , wherein the controller predicts the major and minor axes from at least four samples of the line voltage.

Claim 8

The apparatus of claim 1 , wherein the controller measures a locus of the Park vector and varies the locus until the locus becomes circular, the positive sequence being a vector defined by the circular locus.

Claim 9

The apparatus of claim 7 , wherein the controller extracts a unit amplitude Park vector from a voltage Park vector, computes a vector cross product of the voltage Park vector v and a negative sequence unit vector, determines a negative sequence in a negative sequence reference frame from the vector cross product, performs a synchronous-to-stationary reference frame transformation, the result of the transformation being a negative sequence component of the voltage Park vector, and removes the negative sequence component from the voltage Park vector; whereby the positive sequence component of the voltage Park vector remains.

Claim 10

A controller for an active rectifier of a power distribution system, the power distribution system having a distribution feeder line, the controller comprising: first means for taking samples of line voltage, the samples lying on a locus of a Park vector representing the line voltage; second means for predicting major and minor axes of the locus of the Park vector; and third means for extracting a positive sequence component from the major and minor axes.

Claim 11

A controller for an active rectifier of a power distribution system, the power distribution system having a distribution feeder line, the controller comprising: first means for taking samples of line voltage, the samples lying on a locus of a Park vector representing the line voltage; second means for predicting major and minor axes of the locus of the Park vector; and third means for extracting a positive sequence component from the major and minor axes.

Claim 12

The controller of claim 9 , wherein angle of the positive sequence is initially determined from the major and minor axes; and wherein the angle is updated at discrete intervals.

Claim 13

The controller of claim 10 , wherein the angle (α i+1 ) is updated by α i+1 =α m +90° (ΔT)F, where F is the fundamental frequency of the positive sequence, ΔT is the time between samples, and α m is the angle of one of the major and minor axes.

Claim 14

The controller of claim 11 , wherein the fundamental frequency is updated at regular intervals.

Claim 15

The controller of claim 9 , wherein the major and minor axes are predicted from at least four samples of the line voltage.

Claim 16

A controller for an active rectifier of a power distribution system, the power distribution system having a distribution feeder line, the controller comprising: first means for extracting a unit amplitude Park vector from a voltage Park vector representing the line voltage; second means for computing a vector cross product of the voltage Park vector and a negative sequence unit vector; third means for determining a negative sequence in a negative sequence reference frame from the vector cross product; fourth means for performing a synchronous-to-stationary reference frame transformation on the negative sequence reference frame, the result of the transformation being a negative sequence component of the voltage Park vector; and fifth means for removing the negative sequence component from the voltage Park vector.

Claim 17

A controller for an active rectifier of a power distribution system, the power distribution system having a distribution feeder line, the controller comprising: first means for extracting a unit amplitude Park vector from a voltage Park vector representing the line voltage; second means for computing a vector cross product of the voltage Park vector and a negative sequence unit vector; third means for determining a negative sequence in a negative sequence reference frame from the vector cross product; fourth means for performing a synchronous-to-stationary reference frame transformation on the negative sequence reference frame, the result of the transformation being a negative sequence component of the voltage Park vector; and fifth means for removing the negative sequence component from the voltage Park vector.

Claim 20

The method of claim 15 , wherein the positive sequence is determined by taking samples of the line voltage, the samples lying on a locus of the Park vector; predicting major and minor axes of the locus of the Park vector; and extracting a positive sequence from the major and minor axes.

Claim 21

The method of claim 16 , wherein an angle of the positive sequence is initially determined from the major and minor axes; and wherein the angle is updated at discrete intervals.

Claim 22

The method of claim 17 , wherein the angle (α i+1 ) is updated by (α i+1 =α m +90° (ΔT)F, where F is the fundamental frequency of the positive sequence, ΔT is the time between samples, and α m is the angle of one of the major and minor axes.

Claim 23

The method of claim 18 , wherein the fundamental frequency is updated at regular intervals.

Claim 24

The method of claim 15 , wherein the positive sequence is determined by extracting a unit amplitude Park vector from a voltage Park vector representing line voltage; computing a vector cross product of the voltage Park vector and a negative sequence in a negative sequence reference frame unit vector; determining a negative sequence reference frame from the vector cross product, using the negative sequence to determine a negative sequence component of the voltage Park vector; and removing the negative sequence component from the voltage Park vector.