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United States Patent Application 
20180164379

Kind Code

A1

MARTIN; Denis Michel
; et al.

June 14, 2018

METHOD FOR DETERMINING A DROOP RESPONSE PROFILE OF AN ELECTRICAL MACHINE
CONNECTED TO AN ELECTRICAL GRID
Abstract
A method for determining a droop response profile of a rotating
electrical machine supplying electricity to an electrical network having
a network frequency varying on either side of a nominal frequency,
wherein a measured rotational speed value and droop response parameters
are defined. The droop response profile is a graph centered on the
coordinates ([X5; Y5]) of an origin point between 99% and 101% of the
measured speed value and defined by at least two coordinate points
([X4,Y4], [X0, Y0]) in the case of overspeed, each of the points having
as abscissa a speed value as a percentage of the measured speed value,
and for ordinates a filtered speed value as a percentage of the measured
speed value modulated by at least one of the droop response parameters.
Inventors: 
MARTIN; Denis Michel; (VieuxCharmont, FR)
; GROSSHANS; Sabastien Philippe; (Sermamagny, FR)

Applicant:  Name  City  State  Country  Type  GE ENERGY PRODUCTS FRANCE SNC  Belfort   FR
  
Family ID:

1000002747695

Appl. No.:

15/633930

Filed:

June 27, 2017 
Current U.S. Class: 
1/1 
Current CPC Class: 
G01P 3/44 20130101; G01R 31/34 20130101 
International Class: 
G01R 31/34 20060101 G01R031/34; G01P 3/44 20060101 G01P003/44 
Foreign Application Data
Date  Code  Application Number 
Dec 14, 2016  FR  1662419 
Claims
1. A method for determining a droop response profile of a rotating
machine supplying electricity to an electrical network having a network
frequency varying on either side of a nominal frequency, wherein a
measured speed value (Vm) of the rotation of the rotating machine
corresponding to the frequency of the electrical network and wherein
response parameters to the measured speed value are defined,
characterized in that the profile is a graph centered on a coordinate
point of origin ([X5; Y5]) between 99% and 101% of the measured speed
value and defined by at least two coordinate points ([X4; Y4], [X0; Y0])
in case of underspeed and by at least two coordinate points ([X6; Y6],
[X10; Y10]) in case of overspeed, each point having a speed value as a
percentage of the measured speed value, and for ordinates a speed value
filtered as a percentage of the measured speed value modulated by at
least one of the response parameters, the response parameters comprising
at least a high dead band (BMH) value and a low dead band (BMB) value on
either side of the point of origin ([X5;Y5]), a low droop, a median
droop, and a high droop (SB, SM, SH) of the rotating machine, a low and a
high droop limit value (LSB, LSH), at least one dead band output mode
(SBM1, SBM2, SBM3), and a low and a high breaking point (PCB, PCH) of a
nonlinear droop.
2. The method of claim 1, wherein the coordinates ([X4; Y4]) of a first
point in the case of underspeed correspond to the low dead band value
and have an abscissa (X4) equal to subtraction of 100% of the measured
speed value with the low dead band value, and for ordinates (Y4) equal to
100% of the measured speed value.
3. The method of claim 2, wherein a median droop gain (GSM) value and a
low droop gain (GSB) value correspond to a ratio between the intrinsic
droop of the rotating machine and, respectively, the median droop (SM)
and the low droop (SB).
4. The method of claim 3, wherein coordinates ([X3; Y3]) of a second
point in the case of underspeed correspond to the output of the dead
band as a function of the at least one dead band output mode (SBM), the
low limit droop (LSB) value, the low dead band (BMB) value, the median
droop gain (GSM) value, and the low breaking point (PCB) value.
5. The method of claim 4, wherein coordinates ([X2; Y2]) of a third point
in the case of underspeed correspond to the low breaking point of the
nonlinear droop as a function of the coordinates of the second point
([X3;Y3)], the low breaking point (PCB) value, the low droop limit (LSB)
value, and the median droop gain (GSM) value.
6. The method of claim 5, wherein coordinates ([X1; Y1]) of a fourth
point in the case of underspeed correspond to the low droop limit value
as a function of the coordinates of the third point ([X2; Y2]) and the
low droop gain (GSB) value.
7. The method of claim 6, wherein coordinates ([X0; Y0]) of a fifth point
in the case of underspeed correspond to a limit point of the response
profile as a function of the coordinates of the fourth point ([X1; Y1])
and the low droop limit (LSB) value.
8. The method of claim 7, wherein coordinates ([X6; Y6]) of a first point
in the case of an overspeed correspond to the high dead band value and
have the abscissa (X6) equal to the addition of 100% of the measured
speed value to the high dead band (BMH) value, and for ordinate (Y6)
equal to 100% of the measured speed value.
9. The method of claim 8, wherein the high droop gain (GSH) value
corresponds to a ratio between the intrinsic droop of the rotating
machine and the high droop (SH).
10. The method of claim 9, wherein coordinates ([X7; Y7]) of a second
overspeed point correspond to the output of the dead band as a function
of the dead band output mode (SBM), the high droop limit value (LSH), the
high dead band (BMH) value, the high droop gain (GSH) value, and the high
breaking point (PCH) value.
11. The method of claim 10, wherein coordinates ([X8; Y8]) of a third
overspeed point correspond to the high breaking point of the nonlinear
droop as a function of the coordinates of the second point ([X7; Y7]) of
the high breaking point (PCH) value, the high droop limit (LSH) value,
and the median droop gain (GSM) value.
12. The method of claim 11, wherein coordinates ([X9; Y9]) of a fourth
overspeed point correspond to the high droop limit value as a function
of the coordinates of the third point ([X8; Y8]), the high droop limit
(LSH) value, and the high droop gain (GSH) value.
13. The method of claim 12, wherein coordinates ([X10; Y10]) of a fifth
point in overspeed correspond to a limit point of the response profile
as a function of the coordinates of the fourth point ([X9; Y9] and the
high droop limit (LSH) value.
14. The method of claim 1, wherein the low dead band (BMB) value is
between 0.02% and 6% of the measured speed value (Vm).
15. The method of claim 1, wherein the high dead band (BMH) value is
between 0.02% and 1% of the measured speed value (Vm).
16. The method of claim 1, wherein the median droop (SM) value, the low
droop (SB) value, and the high droop (SH) value are between 2% and 20% of
the measured speed value (Vm).
17. The method of claim 1, wherein the low breaking point (PCB) value and
the high breaking point (PCH) value of the nonlinear droop are selected
from 0% to 10% of the measured speed value.
18. The method of claim 1, wherein the low droop limit (LSB) value is
between 96% and 100% of the filtered speed value.
19. The method of claim 1, wherein the high droop limit (LSH) value is
between 100% and 104% of the filtered speed value.
20. The method of claim 1, wherein the at least one dead band output mode
(SBM) is selected from the group comprising a first output mode (SBM1) in
which, once a dead band extreme value has been reached, the filtered
speed reaches the speed defined by the droop, a second output mode
(SBM2), in which, once the deal band extreme value has been reached, the
filtered speed is defined by the droop while maintaining a constant
offset of the dead band proportional to the measured speed value, and a
third output mode (SBM3), in which, once the extreme value of the dead
band has been reached, the filtered speed joins the speed defined by the
droop while following a ramp equivalent to a 2% droop.
Description
TECHNICAL FIELD
[0001] The present application relates generally to rotating machines
generating electricity in order to satisfy the electricity requirements
of an electrical network and more particularly relates to the control of
such rotating machines.
BACKGROUND OF THE INVENTION
[0002] An electrical network must ensure a constant balance between
electrical consumption and electrical generation. Thus, increasing
electrical consumption results in a drop in the frequency of the
electrical network. Conversely, a drop in electrical consumption results
in increasing the frequency of the electrical network.
[0003] In order to maintain a constant balance between electrical
consumption and generation, the output of the power generating groups may
be regulated to maintain the frequency of the electrical network at, for
example, around 50 Hz or so. The power output provided by each group of
generators producing electricity may be defined by its droop.
Specifically, droop may be defined as the ratio between power output
variation and frequency variation.
[0004] In addition, the use of renewable energy also affects the stability
of the electrical grid. Thus, the power generating groups may be required
to modify their response profile in droop to the frequency variations of
the electrical network. Also, there may be certain electrical networks
requiring different responses from the power generating groups when the
electrical network is operating in under or over frequency. The droop
response profile of such electrical production may be called an
"asymmetrical droop response profile."
[0005] In order to limit the frequency instabilities generated by network
compensating operations, it may be necessary to define a dead band within
the group of electrical production that may not provide compensation to
maintain the frequency, in spite of a continuous variation in the
frequency of the electrical network. The dead band range may be
determined by either the electrical producer or by the implementing rules
for the electrical network defined by a transport network administrator
(GRT) or by a transmission system operator (TSO). The administrator of a
transport network also may define the parameters of an operating profile
of the generator group such as the behavior at the exit of dead band, the
droop for the group of electrical production, or a droop limiter.
[0006] As an example, U.S. Pat. No. 6,118,187 describes a procedure for
implement a dynamic dead band in order to manage a dynamic frequency in
an electrical network in terms of frequency and amplitude. In addition,
U.S. Patent Publication No. 2014/0260293 describes a control device for a
gas turbine, including a system for droop response configured to detect
one or several operating features in a turbine. For this purpose, the
control device may include a multivariable correction method based on
operational characteristics such as a derivation of the load dependent on
the percentage of the speed, the percentage of the turbine frequency, and
the derivation of the ambient temperature at the intake of the turbine
compressor. The correction method thus may generate a series of
correction factors for the droop response that make it possible to
produce a graph of the behavior of the turbine with a correction on the
ambient temperature as a function of the input temperature of the turbine
compressor.
[0007] However, the known methods for configuring the droop response of a
turbine may not allow for the automatic integration of several functions
such as the dead band, the droop of the electrical generating group, the
output of the dead band, or limiting the droop response in order to
determine a response profile of the turbine to variations in speed. A
value of 100% of speed may correspond to about 50 Hz or 60 Hz depending
on the country.
[0008] Thus, an object of the present application is to remedy the
aforementioned drawbacks and to propose a method of defining a static
response profile of an electrical generation group capable of responding
to the frequency variations of the electrical network.
SUMMARY OF THE INVENTION
[0009] The present application relates to a method of determining a
response profile in droop or a speed profile of a rotating electrical
machine supplying electricity to an electrical network. A network
frequency may vary on either side of a nominal frequency in which a
measured value (Vm) of the speed of rotation of the rotating machine
corresponding to the image of the frequency of the electrical network and
the response parameters in dependence of the measured speed value are
defined. The static response profile may be a graph centered on the
coordinates of an origin point between 99% and 101% of the measured
speed, preferably equal to 100% of the measured speed, and defined by at
least two points in the case of underspeed and by at least two points in
the case of overspeed. Each of the points may have speed value as a
percentage of the measured speed and for ordinates a filtered speed value
as a percentage of the measured speed modulated by at least one of the
droop response parameters. The value of the filtered speed may affect the
fuel control loop.
[0010] The parameters may include at least the value of the high dead band
and the low dead band on either side of the original coordinate point,
the value of the low, the median, and the high droop of the rotating
machine, the value of the low and high limiter droop, at least one dead
band output mode, and the value of the low and high breaking points of
the nonlinear droop. Advantageously, the coordinates of a first point may
be calculated in the case of underspeed, corresponding to the low dead
band, having as the abscissa equal to the subtraction of 100% of the
measured speed value with the low dead band, and ordinates equal to 100%
of the measured speed.
[0011] To define the dead band output, the value of a gain of the median
droop and the value of a low droop gain may be calculated. The gain of
the droop may correspond to a ratio between the intrinsic droop of the
rotating machine, for example 4%, divided by the desired droop. For
example, for a desired droop of 4% the corresponding gain may be 1
(4%/4%). Thus, for a real speed delta measured by 0.2% at the dead band
output, the filtered delta may be 0.2%. Moreover, for a desired droop of
2%, the corresponding gain may be 2 (4%/2%). Thus, for a measured speed
delta of 0.2% at the dead band output, the filtered delta may be 0.4%.
For example, the coordinates of a second point may be calculated in the
case of underspeed, corresponding to the output of the dead band, as a
function of the dead band output mode, low droop limiter value, low dead
band value, median droop gain, and low breaking point value.
[0012] Advantageously, the coordinates of a third point may be calculated
in the case of underspeed, corresponding to the low breaking point of
the nonlinear droop, as a function of the coordinates of the second
point, the value of the low breakpoint, the value of the low droop
limiter, and median droop gain. Advantageously, the coordinates of a
fourth point may be calculated in the case of underspeed, corresponding
to the low droop limiter, as a function of the coordinates of the third
point, the value of the low droop limiter, and the low droop gain.
Advantageously, the coordinates of a fifth point may be calculated in the
case of underspeed, corresponding to the low limit point of the response
profile, as a function of the coordinates of the fourth point and of the
value of the low droop limiter.
[0013] According to another embodiment, the coordinates of a first point
may be calculated in the case of an overspeed corresponding to the high
dead band and having on the abscissa equal to the addition of 100% of the
measured speed with the value of the band 100% of the measured speed. To
define the dead band output, the value of a high droop gain corresponding
to the ratio between the intrinsic droop of the machine and the desired
droop, for example 4%, may be calculated. For example, the coordinates of
a second point may be calculated in the case of overspeed, corresponding
to the output of the dead band, depending on the dead band output mode,
the high droop limiter value, the value of the high dead band, the high
droop gain, and the value of the high breakpoint.
[0014] Advantageously, the coordinates of a third point may be calculated
in the case of overspeed, corresponding to the high breaking point of
the nonlinear droop, as a function of the coordinates of the second
point, the value of the high break point, the value of the high droop
limiter, and the median droop gain. Advantageously, the coordinates of a
fourth point may be calculated in the case of overspeed, corresponding
to the high droop limiter, as a function of the coordinates of the third
point, of the value of the high droop limiter, and of the high droop
gain. Advantageously, the coordinates of a fifth point may be calculated
in the case of overspeed, corresponding to the high limit point of the
response profile, as a function of the coordinates of the fourth point,
and of the value of the high droop limiter.
[0015] The value of the low dead band may be, for example, between 0.02%
and 6% of the measured speed value. The value of the high dead band may
be, for example, between 0.02% and 1% of the measured speed value. At
least one of the values of the median droop, the low droop, and the high
droop may be, for example, between 2% and 20% of the measured speed
value. At least one of the values of the low and high break points of the
nonlinear droop may be, for example, between 0% and 10% of the measured
speed value. The value of the low droop limiter may be, for example,
between 96% and 100% of the filtered speed value. The value of the high
droop limiter may be, for example, between 100% and 104% of the filtered
speed value.
[0016] According to one embodiment, the dead band output may be selected
from a group including a first output mode in which, once the dead band
extreme value has been reached, the filtered speed joins the speed
defined by the droop, a second output mode in which, once the extreme
value of the dead band is reached, the filtered speed may be defined by
the droop while maintaining the constant offset of the dead band
proportional to the measured speed, and a third output mode in which once
the extreme value of the dead band has been reached, the filtered speed
joins the speed defined by the droop while following a ramp equivalent to
a droop of 2%.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The other objectives, characteristics, and advantages of the
present application will become apparent on reading the following
description, given solely by way of nonlimiting examples, and made with
reference to the accompanying drawings, in which:
[0018] FIG. 1 illustrates a flowchart of a method of determining a static
response profile of a rotating electrical machine according to an
embodiment of the present application;
[0019] FIG. 2 illustrates a graph representing a set of functions of a
universal speed filter determined according to the method of FIG. 1; and
[0020] FIG. 3 shows in detail an example of the application of the
universal speed filter of FIG. 2.
DETAILED DESCRIPTION
[0021] In the following description, the term "measured speed value Vm" is
understood to mean the image of the frequency of the electrical network
as seen by the controller, the real value of the rotation of the shaft of
the rotating machine. The measured speed value Vm is expressed as a
percentage (%) of the speed of the electrical generating unit with
respect to the nominal speed of the rotating machine. A value of 100% of
speed corresponds to 50 Hz or 60 Hz depending on the country.
[0022] The power contribution to be provided by each power generating
group may be defined by its own droop, i.e., the ratio between the power
variation and the frequency variation of the power grid expressed as a
percentage (%). For example, a 4% droop means that a 4% change in the
speed of the rotating machine will result in a 100% change in the nominal
power of the rotating machine. Thus, an overspeed of the electrical
network of 1%, that means 0.5 Hz, will imply a 25% decrease in the
nominal power of the rotating machine.
[0023] The droop may be adjusted between 2% and 20%. Thus, with a droop of
20% and an overspeed of the electrical network of 1%, that means 0.5 Hz,
may imply a 5% decrease in the nominal power of the rotating machine.
Similarly, with a 2% droop and an overspeed of the power grid of 1%,
that means 0.5 Hz, may imply a 50% reduction in the nominal power of the
rotating machine.
[0024] FIG. 1 shows a flow chart of a method 10 for determining a static
response profile of a rotating electric machine connected to an
electrical network capable of responding to variations in the frequency
of the electrical network. Hereafter the droop response profile will be
called a speed profile or a universal speed filter.
[0025] As illustrated in FIG. 1, the control method of the rotating
machine may include a first step 12 for recovering a measured speed value
Vm and a second step 14 for determining a number of droop response
parameters, dependent on the measured speed Vm of the rotating electrical
machine.
[0026] in step 14, low and high parameters of the droop response
corresponding to underspeed and overspeed are determined: [0027] the
value of low dead band BMB and high dead band BMH, expressed as a
percentage (%) of the measured speed value Vm, [0028] the value of the
median droop SM, low SB and high SH, expressed as a percentage (%) of the
measured speed value Vm, [0029] the value of the low droop limiter LSB
and high LSH, expressed as a percentage (%) of the measured speed value
Vm, [0030] the dead band output mode for the underspeed and the
overspeed, selected from SBM1, SBM2, SBM3, it is also possible to choose
a different dead band output mode for under and over speed, [0031] the
value of the low breaking point PCB and high PCH of the nonlinear droop,
expressed as a percentage (%) of the measured speed value Vm.
[0032] A dead band BM is defined as an inhibition of the power response of
the power generation group within a given speed range. Thus, three types
of dead bands are defined: [0033] A minimal dead band, applied by
default, corresponding to the smallest acceptable dead band, for example
between +/0.02% of the measured speed value, that means+/10 mHz with
respect to the nominal frequency. This minimal dead band makes it
possible to avoid the load variations of the rotating machine for small
variations in the frequency of the electrical network. [0034] A variable,
symmetrical or asymmetric dead band referenced to the nominal speed, and
for example between +/1% of the measured speed value Vm, that
means+/500 mHz. [0035] A fixed, symmetrical or asymmetric dead band, for
example between 6% and 1% of the measured speed value Vm, that means
between 3 Hz and 0.5 Hz.
[0036] The choices of the BM dead band are exclusive, therefore if the
variable dead band is activated, then the fixed and default dead bands
are disabled. Similarly, when the fixed and variable dead bands are
deactivated, the default band BM.sub.1 is activated.
[0037] The value of the low dead band BMB is, for example, between 0.02%
and 6% of the measured speed value Vm.
[0038] The value of the high dead band BMH is, for example, between 0.02%
and 1% of the measured speed value Vm.
[0039] The values of median droop SM, low droop SB and high droop SH are,
for example, between 2% and 20% of the measured speed value Vm.
[0040] Droop response limitations makes it possible to limit the
contribution of the load from a percentage value of the measured speed Vm
to overspeed and/or underspeed by limiting the filtered speed to a
constant value. In addition, in the case of overspeed above 101%, the
droop response limitation may be deactivated to prevent the rotating
machine from operating at high load and speed. Thus, for example, a value
of the low droop limiter LSB of between 96% and 100% of the filtered
speed value may be selected, and a value of the high droop limiter LSH of
between 100% and 104% of the filtered speed value.
[0041] The SBM dead band output represents the behavior of the rotating
machine at the output of the dead band BM, that is, when the speed value
measured in % exceeds the predefined dead band BM.
[0042] Thus, three modes of dead band output are defined: [0043] The
first output mode SBM1, referred to as the step, in which, once the
extreme value of the dead band BM has been reached, the filtered speed
may have as a value the modulated speed according to the droop applied.
[0044] The second output mode SBM2, referred to as the rail, in which,
once the extreme value of the dead band BM has been reached, the filtered
speed may be defined by the droop applied in proportion to the measured
speed while maintaining the constant offset of the dead band. [0045] The
third output mode SBM3, referred to as ramp mode, in which, once the
extreme value of the dead band BM has been reached, the filtered speed
may have the value of the measured speed modulated by the applied droop
while following a ramp equivalent to a droop of 2%.
[0046] Thus, in overspeed and underspeed, it is possible to choose
identical or different dead band output modes.
[0047] The values for the low breaking point PCB and high PCH of the
nonlinear droop may be selected between 0% and 10% of the measured speed
value.
[0048] We define a variable droop by default of 4% and adjustable over a
range of between 2% and 20% applied over the entire operating range, and
a nonlinear droop composed of three speed ranges having their respective
droop and delimited by two points of inflection on either side of the
nominal speed.
[0049] The static response parameters may be determined either by the
socalled "TSO" transmission system operator ("TSO") or by the operator.
[0050] Some of the droop response parameters may be set up or changed by
the operator and other droop response parameters may be set in the
software or controller without being able to be modified.
[0051] The method 10 then includes a step 16 for determining the
coordinates [X5; Y5] of a point of origin of a graph illustrating a speed
profile or response profile in droop, illustrated in FIG. 2. The
coordinates [X5; Y5] of the point of origin are defined according to the
following equation:
{ X 5 = 100 % Y 5 = 100 %
( Eq . 1 ) ##EQU00001##
[0052] The speed profile, illustrated in FIG. 2, is a graph defined by a
set of points of coordinates [Xi; Yi], where "i" is an integer between 0
and 10, the abscissa being the value of the measured speed Vm, in %,
corresponding to the image of the frequency of the electrical network,
and for ordinates the value of the filtered speed Vf, in %, corresponding
to the measured speed Vm modulated by the response parameters in droop.
[0053] The term "measured speed value Vm" means the real rotational value
of the rotating machine shaft, expressed as a percentage (%) of speed
with respect to the nominal speed of the rotating machine which is
equivalent to 100%.
[0054] The term "filtered speed value Vf" is understood to mean the speed
value expressed as a percentage (%) of speed with respect to the nominal
speed of the rotating machine modulated by the various statistic response
parameters determined in step 14.
[0055] As shown in FIG. 2, the speed profile is centered on the
coordinates [X5; Y5] of the origin point corresponding to the measured
speed Vm nominal of 100%. The corresponding filtered speed Vf is also
100%. Alternatively, the point of origin [X5; Y5] may be adjusted in a
range between 99% and 101% of the measured speed Vm.
[0056] The method includes calculating the coordinates [X4; Y4] to [X0;
Y0] from the first to the fifth point respectively in the case of
underspeed and the calculation of the coordinates [X6; Y6] to [X10; Y10]
at the first to fifth point respectively in the case of overspeed.
[0057] As illustrated in FIG. 1, the method may include steps 18 to 32 for
calculating the points of coordinates [X4; Y4] to [X0; Y0] in the case of
underspeed and steps 34 to 48 for calculating the points of coordinates
[X6; Y6] to [X10; Y10] in the case of overspeed.
[0058] In step 18, the coordinates [X4; Y4] from a first underspeed point
as a function of the low dead band BMB.
[0059] Thus, for example, in the case of underspeed not exceeding the
selected low dead band BMB, the value of the filtered speed at point Y4
will correspond to the nominal speed of 100%. The coordinates of the
first point [X4; Y4] according to the following equation:
{ X 4 = 100 %  BMB Y 4 = 100 %
( Eq . 2 ) ##EQU00002##
[0060] Outside the BMB low dead band, the real speed delta corresponds to
a filtered delta of speed, that is to say to the delta of measured speed
multiplied by a gain of the droop. The gain of the droop may be the ratio
between the intrinsic droop of the rotating machine, for example equal to
4%, divided by the desired droop.
[0061] Thus, in step 20, the value of the gain of the median droop GSM and
the value of the gain of the low droop GSB may be calculated as a
function of the median droop SM and the low SB respectively according to
the following equations:
GSM = 4 % SM ( Eq . 3 ) GSB = 4 % SB
( Eq . 4 ) ##EQU00003##
[0062] For example, for a desired low or median droop of between 2% and
20%, the low droop gain GSB and the median droop gain GSM may be between
2 and 0.2 respectively, for example equal to 1, for example equal to 0.5.
[0063] In step 22, the coordinates [X3; Y3] of a second point underspeed
as a function of the mode of output of the SBM dead band selected in step
14.
[0064] If the dead band SBM1 output of step type has been selected in step
14, the coordinates [X3; Y3] of the second point according to the
following Equation Eq. 5:
{ X 3 = X 4 Y 3 = 100  MIN
( 100  LSB ; BMB GSM ) ( Eq . 5 )
##EQU00004##
[0065] The abscissa X3 of the second point may be equal to the abscissa X4
of the first point previously determined in step 18.
[0066] The ycoordinate Y3 of the second point may be equal to 100 minus
the minimum value between (100 minus the value of the low droop limiter
LSB) and the value of the low dead band BMB multiplied by the median GSM
droop gain.
[0067] If the railtype SBM2 dead band output has been selected in step
14, the coordinates [X3; Y3] of the second point according to the
following Equation Eq. 6:
{ X 3 = X 4 Y 3 = Y 4
( Eq . 6 ) ##EQU00005##
[0068] The second coordinate point [X3; Y3] may be coincident with the
first point of coordinates [X4; Y4] previously determined in step 18.
[0069] If the dead band output SBM3 in ramp mode was selected in step mode
14 and the gain value of the median droop is different from 2, then we
have the coordinates of the second point [X3; Y3] according to the
following Equation Eq. 7:
{ X 3 = 100  MIN ( 100  LSB 2 ; BMB GSM 2
 GSM ) Y 3 = 100  ( 2 ( X 4  X
3 ) ) ( Eq . 7 ) ##EQU00006##
[0070] If the value of gain of the median droop is equal to 2, the low
dead band cannot be ramped, thus we may retake the coordinates [X3; Y3]
of the second point defined in Equation Eq. 6.
[0071] In step 24, when the output of dead band SBM1 of step type has been
selected, the value of the low breaking point PCB may be compared with
the value of the low dead band BMB.
[0072] If the value of the low breaking point PCB is lower than the value
of the low dead band BMB, the we recalculate the coordinates [X3; Y3] of
the second point per the following Equation Eq. 8:
{ X 3 = X 4 Y 3 = 100  MIN
( 100  LSB ; BMB GSB ) ( Eq . 8 )
##EQU00007##
[0073] In step 26, we recalculate the coordinates [X2; Y2] of a third
point in underspeed, corresponding to the low breaking point of the
nonlinear droop, according to the following Equation Eq. 9:
{ X 2 = MAX ( 100  PCB ; X 3  Y
3  LSB GSM ) Y 2 = Y 3  ( X
3  X 2 ) GSM ( Eq . 9 ) ##EQU00008##
[0074] In step 28, the value of the abscissa X3 of the second point is
compared with (100PCB).
[0075] If the value 100PCB is greater than the value of the abscissa X3
of the second point, we recalculate the coordinates [X2; Y2] per the
following Equation Eq. 10:
{ X 2 = X 3 Y 2 = Y 3
( Eq . 10 ) ##EQU00009##
[0076] In step 30, the coordinates [X1; Y1] of a fourth underspeed point
may be calculated, corresponding to the underspeed droop limiter, per
the following Equation Eq. 11:
{ X 1 = MAX ( 90 ; X 2  Y 2 
LSB GSB ) Y 1 = Y 2  ( X 2 
X 1 ) GSB ( Eq . 11 ) ##EQU00010##
[0077] In step 32, we recalculate the coordinates [X0; Y0] of a fifth
point in underspeed, corresponding to the underspeed limit point of the
filter, per the following Equation Eq. 12:
{ X 0 = 90 Y 0 = MAX ( LSB ; Y
1 ) ( Eq . 12 ) ##EQU00011##
[0078] Thus, each segment defined by two points corresponds to a function
modulated by the functions that precedes it.
[0079] The steps 34 to 48 represent the steps of calculating the points of
coordinates [X6; Y6] to [X10; Y10] in the case of overspeed.
[0080] In step 34, the coordinates [X6; Y6] of a first point in
overspeed, as a function of the high dead band BMH.
[0081] Thus, for example, in case of overspeed not exceeding the selected
high BMH dead band, the value of the speed filtered at point Y6 may
correspond to the nominal speed of 100%. The coordinates [X6; Y6] of the
first point per the following Equation:
{ X 6 = 100 % + BMH Y 6 = 100 %
( Eq . 13 ) ##EQU00012##
[0082] Outside the selected BMH high dead band, the real speed delta
corresponds to a filtered delta of speed, that is to say to the delta of
measured speed multiplied by a gain of the droop. The gain of the droop
may be the ratio between the intrinsic droop of the rotating machine, for
example equal to 4%, divided by the desired droop.
[0083] Thus, the median GSM droop gain value, calculated in step 20, may
be applied.
[0084] In step 36, the value of the gain of the high droop GSH as a
function of the high droop SH may be calculated per the following
Equation:
GSH = 4 % SH ( Eq . 14 ) ##EQU00013##
[0085] For example, for a desired high droop between 2% and 20%, the high
droop gain GSH may be between 2 and 0.2.
[0086] In step 38, the coordinates [X7; Y7] of a second point, in
overspeed, as a function of the output mode of the dead band SBM may be
determined in step 14.
[0087] If the stepmode dead band output SBM1 has been selected in step
14, the coordinates [X7; Y7] of the second point may be calculated per
the following Equation Eq. 15:
{ X 7 = X 6 Y 7 = 100 + MIN
( LSH  100 ; BMH GSM ) ( Eq . 15 )
##EQU00014##
[0088] The abscissa X7 of the second point may be equal to the abscissa X6
of the first point previously determined in step 34.
[0089] The ycoordinate Y7 of the second point may be equal to 100 plus
the minimum value between (the value of the highdroop limiter LSH minus
100) and (the value of the high dead band BMH multiplied by the median
GSM droop gain calculated at 1 Step 20).
[0090] If the railmode SBM2 dead band output has been selected in step
14, the coordinates [X7; Y7] of the second point may be calculated per
the following Equation Eq. 16:
{ X 7 = X 6 Y 7 = Y 6
( Eq . 16 ) ##EQU00015##
[0091] The second coordinate point [X7; Y7] may be coincident with the
first point of coordinates [X6; Y6] previously determined in step 34.
[0092] If the ramp mode SBM3 output of dead band has been selected in step
14 and the value of the gain of the median droop is different from 2, the
coordinates [X7; Y7] of the second point may be calculated per the
following Equation Eq. 17:
{ X 7 = 100 + MIN ( LSH  100 2 ; BMH GSM
2  GSM ) Y 7 = 100 + ( 2 ( X 7  X
6 ) ) ( Eq . 17 ) ##EQU00016##
[0093] If the value of the gain of the median droop is equal to 2, the
high dead band BMH cannot be caught, we retake the coordinates [X7; Y7]
of the second point defined in the Equation Eq. 16.
[0094] In step 40, when the step mode dead band output SBM1 has been
selected, the value of the high breaking point PCH may be compared with
the value of the high dead band BMH.
[0095] If the value of the high breaking point PCH is less than the value
of the high dead band BMH, the coordinates [X7; Y7] of the second point
may be calculated per the following Equation Eq. 18:
{ X 7 = X 6 Y 7 = 100 + MIN
( LSH ; BMH GSH ) ( Eq . 18 ) ##EQU00017##
[0096] In step 42, the coordinates [X8; Y8] of a third point may be
calculated, in overspeed, corresponding to the high breaking point of
the nonlinear droop, per the following Equation Eq. 19:
{ X 8 = MIN ( 100 + PCH ; X 7 + LSH 
Y 7 GSM ) Y 8 = Y 7 + ( X
8  X 7 ) GSM ( Eq . 19 )
##EQU00018##
[0097] In step 44, the value of the abscissa X7 of the second point may be
compared with (100+PCH).
[0098] If the value 100+PCH is less than the value of the abscissa X7, the
coordinates [X8; Y8] of the third point may be calculated per the
following Equation Eq. 20:
{ X 8 = X 7 Y 8 = Y 8
( Eq . 20 ) ##EQU00019##
[0099] In step 46, the coordinates [X9; Y9] of a fourth point may be
calculated, corresponding to the overspeed droop limiter, per the
following Equation Eq. 21:
{ X 9 = MIN ( 110 ; X 8  LSH  Y
8 GSH ) Y 9 = Y 8 + ( X 9 
X 8 ) GSH ( Eq . 21 ) ##EQU00020##
[0100] In step 48, the coordinates [X10; Y10], of a fifth point may be
calculated, corresponding to the overspeed limit point of the filter,
per the following equation Eq. 22:
{ X 10 = 110 Y 10 = MIN ( LSH ; Y
9 ) ( Eq . 22 ) ##EQU00021##
[0101] Thus, each segment defined by two points corresponds to a function
modulated by the functions that precedes it.
[0102] As illustrated in FIG. 2, the output of the dead band beyond the
point of coordinates [X4; Y4] in the case of underspeed and beyond the
point of coordinates [X6; Y6] in case of overspeed, has three possible
functions. These different modes allow one to obtain distinct speed
profiles. FIG. 2 shows, in solid lines, the socalled ramp mode of the
output of the dead band SBM3, in dotted lines, the socalled step mode of
output of the dead band SBM1 and in bold dashed lines, the rail mode of
the dead band SBM2.
[0103] In the rail mode, the coordinate points [X7; Y7] of the dead band
may be coincident with the coordinate point [X6; Y6] defining the dead
band for overspeed. Similarly, for the underspeed, the point of exit of
the dead band of coordinates [X3; Y3] may be coincident with the point of
coordinates [X4; Y4] defining the dead band. Thus, outside the dead band,
a filtered delta of speed corresponds to a delta of measured speed
multiplied by the gain of the droop.
[0104] In the ramp mode, the output of the dead band may be set to
overspeed by the segment of coordinates [X6; Y6] and [X7; Y7]
corresponding to the segment between the first and second point or
underspeed by the segment of coordinates [X4; Y4] and [X3; Y3]
corresponding to the segment between the first and second point.
[0105] The filtered speed joins the real speed modulated by the droop gain
following a ramp equivalent to a 2% droop.
[0106] In the step mode, the output of the dead band may be set to
overspeed by the segment of coordinates [X6; Y6] and [X7; Y7]
corresponding to the segment between the first and the second point, or
underspeed by the segment of coordinates [X4; Y4] and [X3; Y3]
corresponding to the segment between the first and second point. The
filtered speed joins the real speed modulated by the droop gain along a
step from the coordinate point [X6; Y6] in overspeed or from the point
of coordinates [X4; Y4] at underspeed.
[0107] Thus, the two segments defined by the coordinates [X7; Y7], [X8;
Y8] of the second and third points and by the coordinates [X8; Y8], [X9;
Y9] of the third and fourth points for the overspeed, or the two
segments defined respectively by the coordinates [X3; Y3], [X2; Y2] of
the second and third points and by the coordinates [X2; Y2], [X1; Y1] of
the third and fourth points for the underspeed, combine two functions
related to the droop, namely: [0108] Nonlinear droop: between the
points of coordinates [X7; Y7] and [X8; Y8], the median droop gain may be
applied and between the points of coordinates [X8; Y8] and [X9; Y9] the
high droop gain may be applied. The point of coordinates [X8; Y9]
corresponds to the breaking point between the two droop segments. [0109]
Variable droop: in this case, the median and high droop gains may be
equal, creating a single segment between the points of coordinates [X7;
Y7] and [X9; Y9] in case of overspeed or between points of coordinates
[X3; Y3] and [X1; Y1] at underspeed.
[0110] The segment defined by the points of coordinates [X9; Y9] and [X10;
Y10] represents the high droop limiter, in which zone the filtered speed
may be constant regardless of the real measured speed variation.
[0111] The segment defined by the points of coordinates [X1; Y1] and [X0;
Y0] represents the low droop limiter, in which zone the filtered speed is
constant regardless of the real measured speed variation.
[0112] The graph illustrated in FIG. 2 represents the set of functions of
a universal speed filter obtained by the method described with reference
to FIG. 1.
[0113] FIG. 3 illustrates a particular case of the universal filter of
FIG. 2, in which a mode of output of the dead band in the ramp mode has
been selected. The set of points of coordinates [X4; Y4] to [X0; Y0] in
the case of underspeed and coordinate points [X6; Y6] to [X10; Y10] in
the case of overspeed may be calculated according to the steps 18 to 48
previously described.
[0114] As soon as the determination method illustrated in FIG. 1 has
elaborated the response profile in the form of a droop or universal speed
profile illustrated in FIG. 2, it may be displayed on a manmachine
interface (HMI). It would also be possible to display on this manmachine
interface a theoretical power response profile corresponding to the
universal speed profile displayed. It will be noted that the coordinates
of the points of this power response profile may be obtained from the
coordinates of the points of the universal speed profile and based on the
relationship between the filtered speed variation and the power variation
inherent in the definition of the droop.
[0115] In the method herein, it would be possible to provide a limitation
to a minimum power defined by the operator using the droop limiter. The
difference between the real power and the minimum power then may be
converted into a permissible variation to define this limitation.
[0116] In general, the method herein makes it possible to integrate a
number of functions related to the measured speed, such as in particular
the value of the dead band and the value of the droop. From this, the
method may determine a universal speed profile, also known as a universal
droop response profile or universal speed filter. This universal speed
profile according to the method herein is thus obtained in various ways:
either all of the parameters of the frequency response are predefined,
for example specified in the transport network manager or determined by
the operator. In some cases, a few or none of these parameters of the
frequency response may be unspecified, then the universal speed profile
may be developed using default parameters, for example a default dead
band of 10 mHz, with rail mode band dead output and/or a droop equal to
4%, or the parameters are defined according the two preceding ways.
[0117] According to the described method, if different parameters are
selected in overspeed and underspeed, the determined speed profile may
be asymmetrical around the coordinate origin point [X5; Y5]. It thus may
be possible to obtain a different behavior from the rotating electrical
machine in overspeed and underspeed. Asymmetry may be particularly
attractive for markets where overspeed and underspeed responses
represent different products and services.
[0118] The method herein thus makes it possible to calculate automatically
and independently the points of coordinates [X0; Y0] through [X4; Y4] at
underspeed with respect to the nominal speed and the points of
coordinates [X6; Y6] to [X10; Y10] at overspeed with respect to nominal
speed.
[0119] The independence of the calculation makes it possible to obtain the
asymmetry of the droop profile.
[0120] In addition, the simultaneous calculation of the coordinates of the
points makes it easy to integrate the modifications of the response
parameters into droop. When a parameter is changed, for example in the
electrical network manager, the method thus may recalculate the set of
coordinates of the points defining the universal speed profile, which
makes the method herein particularly flexible. By virtue of the method
herein, when at least one of the droop response parameters evolves, the
method readjusts or modifies this parameter and automatically
recalculates the set of coordinates of the points defining the universal
speed filter.
[0121] It should be apparent that the foregoing relates only to certain
embodiments of the present application and the resultant patent. Numerous
changes and modifications may be made herein by one of ordinary skill in
the art without departing from the general spirit and scope of the
invention as defined by the following claims and the equivalents thereof.
* * * * *