US2014036563A1PendingUtilityA1
Quadrature-Corrected Feedforward Control Apparatus and Method for DC-AC Power Conversion
Est. expiryOct 11, 2030(~4.3 yrs left)· nominal 20-yr term from priority
H02J 3/381H02M 7/48H02J 2101/24H02M 7/537H02J 3/44H02M 1/0016Y02E10/56
52
PatentIndex Score
0
Cited by
0
References
0
Claims
Abstract
An apparatus and method for controlling the delivery of a pre-determined amount of power from a DC source to an AC grid includes an inverter and an inverter controller. The inverter includes an input converter, an energy storage capacitor, and an output converter. The inverter controller includes an input converter controller and an output converter controller. The input converter controller includes feedforward controller configured to perform a calculation to determine a value for the duty cycle for the input converter such that: (1) the input converter delivers the pre-determined amount of power and (2) the magnitude of a ripple signal reflected into the input source is attenuated toward zero. The input converter controller may also include a quadrature corrector configured to determine the effectiveness of the calculation in attenuating the ripple and to adaptively alter the calculation to improve the effectiveness.
Claims
exact text as granted — not AI-modified1 . An apparatus for controlling the delivery of power from a unipolar input source to an alternating-current (AC) grid, the AC grid characterized by a grid voltage, V rms , a nominal grid frequency ω, and a grid phase θ, the apparatus comprising:
an inverter including (i) an input converter configured to deliver power from the unipolar input source to a unipolar bus, (ii) an energy storage element coupled to the unipolar bus and configured to supply energy to and absorb energy from the unipolar bus, and (iii) an output converter coupled to the unipolar bus and configured to deliver power from the unipolar bus to the AC grid in the form of a substantially sinusoidal current at the grid frequency; and
an input converter controller coupled to the input converter and comprising
(i) a feedforward controller configured to perform a calculation to determine a value for a duty cycle for the input converter such that a magnitude of a ripple signal reflected into the input source is attenuated toward zero and (ii) a quadrature corrector configured to determine the effectiveness of the calculation in attenuating the ripple and to adaptively alter the calculation to improve the effectiveness of the calculation.
2 . (canceled)
3 . The apparatus of claim 1 , wherein the energy storage element is a capacitor.
4 - 6 . (canceled)
7 . The apparatus of claim 1 , wherein:
the quadrature corrector is configured to deliver a phase correction term, δ, and a gain correction term, k, to the feedforward controller, and the feedforward controller calculates a duty cycle, d, of the form: d=d 0 −k·C·, wherein d 0 is indicative of the duty cycle that is required to deliver a pre-determined amount of power.
8 . The apparatus of claim 7 , wherein:
the energy storage element is a storage capacitor of value C bus ; and the feedforward controller is configured to receive (i) measurements indicative of the value of the rms value of the AC grid voltage, V rms , (ii) the rms value of the substantially sinusoidal current delivered by the output converter, I rms , and (iii) the value of the unipolar bus voltage, V bus0 ; and to set
C
=
(
1
-
d
0
)
V
rms
I
rms
2
ω
V
bus
0
2
C
bus
sin
(
2
ω
t
)
.
9 . The apparatus of claim 7 , wherein:
the energy storage element is a storage capacitor of value C bus , and the feedforward controller is configured to receive (i) a measurement indicative of the value of the power delivered by the inverter to the AC grid, P out , and (ii) a value, φ, indicative of a phase difference between the phase of the current delivered to the AC grid and the phase of the AC grid voltage; and to set
C
=
(
1
-
d
0
)
P
out
2
ω
V
bus
0
2
C
bus
cos
(
φ
)
sin
(
2
ω
t
)
.
10 . The apparatus of claim 7 , wherein:
the energy storage element is a storage capacitor of value C bus , and the feedforward controller is configured to receive (i) a measurement indicative of the power delivered by the unipolar input source, P s ; (ii) a value, φ, indicative of a phase difference between the phase of the current delivered to the AC grid and the phase of the AC grid voltage; and (iii) a value indicative of the operating efficiency of the inverter, η; and to set
C
=
(
1
-
d
0
)
P
s
2
ω
V
bus
0
2
C
bus
cos
(
φ
)
sin
(
2
ω
t
)
.
11 . The apparatus of claim 7 , wherein:
the energy storage element is a storage capacitor of value C bus ; and the feedforward controller is configured to receive (i) measurements indicative of the value of the voltage delivered by the unipolar input source, V s , (ii) measurements indicative of the value of the current delivered by the unipolar input source, I s , (iii) a value, φ, indicative of a phase difference between the phase of the current delivered to the AC grid and the phase of the AC grid voltage, and (iv) a value indicative of the operating efficiency of the inverter, η; and to set
C
=
(
1
-
d
0
)
V
s
I
s
2
ω
V
bus
0
2
C
bus
cos
(
φ
)
sin
(
2
ω
t
)
.
12 . The apparatus of claim 7 , wherein the quadrature corrector comprises a first low pass filter, the first low pass filter being configured to receive a measurement indicative of the magnitude of an input current delivered by the unipolar input source, i in , and to deliver a double-frequency signal, ĩ in indicative of the magnitude of the component of the input current ripple that is twice the frequency of the AC grid frequency.
13 . The apparatus of claim 12 , wherein the quadrature corrector further comprises a phase error detector configured to generate a phase error signal based upon a difference between the phase of the double-frequency signal and the grid phase, θ,
wherein the phase error signal has a zero average value when said difference is substantially zero.
14 . The apparatus of claim 13 , wherein the phase error detector comprises:
a first phase comparator that receives a signal indicative of the grid phase, θ, and delivers a signal, Q 2 , such that:
Q
2
=
{
1
if
π
4
<
mod
(
θ
,
π
)
<
3
π
4
-
1
otherwise
;
a first multiplier that delivers a phase error signal, e 2 =Q 2 ·ĩ in ;
a second low pass filter configured to deliver a signal e 2 indicative of the average value of e 2 ; and
a first proportional-integral filter configured to receive e 2 and deliver the phase correction term, δ.
15 . The apparatus of claim 14 , wherein the quadrature corrector further comprises a gain error detector that generates a gain error signal based upon the magnitude of the double-frequency signal,
wherein the gain error signal has a zero average value when said magnitude is substantially zero.
16 . The apparatus of claim 15 , wherein the gain error detector comprises:
a second phase comparator that receives a signal indicative of the phase of the AC grid and delivers a signal:
Q
1
=
{
1
if
0
<
mod
(
θ
,
π
)
<
π
2
-
1
otherwise
;
a second multiplier that delivers a gain error signal, e 1 =Q 1 ·ĩ in ;
a third low pass filter configured to deliver a signal e 1 indicative of the average value of e 1 ; and
a second proportional-integral filter configured to receive e 1 and deliver the gain correction term, k.
17 - 30 . (canceled)
31 . A method for controlling an inverter that is configured to deliver power from a unipolar input source to an alternating-current (“AC”) grid at a grid voltage and grid phase, comprising:
calculating a duty cycle for the an input converter of the inverter such that (a) the input converter delivers a pre-determined amount of power and (b) the magnitude of a ripple signal reflected into the input source is attenuated toward zero, and
determining the effectiveness of the calculation in attenuating the ripple and adaptively altering the calculation to improve the effectiveness of the calculation.
32 - 33 . (canceled)
34 . The method of claim 31 ,
further comprising providing to the inverter controller:
a value indicative of the size of a bus capacitor, C bus ,
a value indicative of the grid frequency, ω,
a measurement of the rms grid voltage, V rms ,
a measurement of the rms inverter output current, I rms ,
a measurement of the unipolar bus voltage, V bus0 ,
a measurement of the grid phase, θ;
wherein calculating the duty cycle for the input converter comprises calculating a duty cycle for the input converter by:
adjusting a nominal duty cycle, d 0 , to a value that is consistent with delivering the pre-determined amount of power,
calculating a correction term, {tilde over (d)}, for attenuating a reflected ripple signal, ĩ r , at a frequency 2ω:
d
~
=
k
(
1
-
d
0
)
V
rms
I
rms
2
ω
V
bus
0
2
C
bus
sin
(
2
ω
t
+
δ
)
,
and
setting the input converter duty cycle equal to:
d={tilde over (d)}+d 0 ; and
assessing the effectiveness of the calculation of the correction term in attenuating the said reflected ripple signal and adaptively altering the values of k and δ to improve the effectiveness.
35 . The method of claim 31 ,
further comprising providing to the inverter controller:
a value indicative of the size of a bus capacitor, C bus ,
a value indicative of the grid frequency, ω,
a value, φ, indicative of a phase difference between the phase of the current delivered to the AC grid and the phase of the AC grid voltage,
a measurement of the inverter output power, P out ,
a measurement of the unipolar bus voltage, V bus0 ,
a measurement of the grid phase, θ;
wherein calculating the duty cycle for the input converter comprises calculating a duty cycle for the input converter by:
adjusting a nominal duty cycle, d 0 , to a value that is consistent with delivering the pre-determined amount of power,
calculating a correction term, {tilde over (d)}, for attenuating a reflected ripple signal, ĩ r , at a frequency 2ω:
d
~
=
k
(
1
-
d
0
)
P
out
2
ω
V
bus
0
2
C
bus
cos
(
φ
)
sin
(
2
ω
t
+
δ
)
,
and
setting the input converter duty cycle equal to:
d={tilde over (d)}+d 0 ; and
assessing the effectiveness of the calculation of the correction term in attenuating the said reflected ripple signal and adaptively altering the values of k and δ to improve the effectiveness.
36 . The method of claim 31 ,
further comprising providing to the inverter controller:
a value indicative of the size of a bus capacitor, C bus ,
a value indicative of the grid frequency, ω,
a value indicative of the operating efficiency of the inverter, η,
a value, φ, indicative of a phase difference between the phase of the current delivered to the AC grid and the phase of the AC grid voltage,
a measurement of the power delivered by the unipolar input source, P s ,
a measurement of the unipolar bus voltage, V bus0 ,
a measurement of the grid phase, θ; and
wherein calculating the duty cycle for the input converter comprises calculating a duty cycle for the input converter by:
adjusting a nominal duty cycle, d 0 , to a value that is consistent with delivering the pre-determined amount of power,
calculating a correction term, {tilde over (d)}, for attenuating a reflected ripple signal, ĩ r , at a frequency 2ω:
d
~
=
k
(
1
-
d
0
)
P
s
2
ω
V
bus
0
2
C
bus
cos
(
φ
)
sin
(
2
ω
t
+
δ
)
,
and
setting the input converter duty cycle equal to:
d={tilde over (d)}+d 0 ; and
assessing the effectiveness of the calculation of the correction term in attenuating the said reflected ripple signal and adaptively altering the values of k and δ to improve the effectiveness.
37 . The method of claim 31 ,
further comprising providing to the inverter controller:
a value indicative of the size of a bus capacitor, C bus ,
a value indicative of the grid frequency, ω,
a value indicative of the operating efficiency of the inverter, η,
a value, φ, indicative of a phase difference between the phase of the wherein calculating the duty cycle for the input converter comprises current delivered to the AC grid and the phase of the AC grid voltage,
a measurement of the voltage delivered by the unipolar input source, V s ,
a measurement of current delivered by the unipolar input source, I s ,
a measurement of the unipolar bus voltage, V bus0 ,
a measurement of the grid phase, θ; and
calculating a duty cycle for the input converter by:
adjusting a nominal duty cycle, d 0 , to a value that is consistent with delivering the pre-determined amount of power;
calculating a correction term, {tilde over (d)}, for attenuating a reflected ripple signal, ĩ r , at a frequency 2ω:
d
~
=
k
(
1
-
d
0
)
V
s
I
s
2
ω
V
bus
0
2
C
bus
cos
(
φ
)
sin
(
2
ω
t
+
δ
)
,
and
setting the input converter duty cycle equal to:
d={tilde over (d)}+d 0 ; and
assessing the effectiveness of the calculation of the correction term in attenuating the said reflected ripple signal and adaptively altering the values of k and δ to improve the effectiveness.
38 . The method of claim 34 , wherein assessing the effectiveness comprises:
generating a signal, Q 1 :
Q
1
=
{
1
if
0
<
mod
(
θ
,
π
)
<
π
2
-
1
otherwise
;
multiplying Q 1 and the reflected ripple signal to generate an error signal,
e 1 =Q 1 ·ĩ in ; and
controlling the value of k to reduce the average value of e 1 towards zero.
39 . The method of claim 34 , wherein assessing the effectiveness comprises:
generating a signal, Q 2 :
Q
2
=
{
1
if
π
4
<
mod
(
θ
,
π
)
<
3
π
4
-
1
otherwise
;
multiplying Q 2 and the reflected ripple signal to generate an error signal,
e 2 =Q 2 ·ĩ r ; and
controlling the value of δ to reduce the average value of e 2 towards zero.Cited by (0)
No later patents cite this yet.
References (0)
No backward citations on record.