US 12,700,735 B1Granted

System-level low voltage ride-through control for the renewable power plant connecting to weak grid

AssigneeNorth China Electric Power University

InventorsTianshu Bi, Ke Jia, Yang Zhang, Hao Liu, Cheng Wang

Life of this patent

Estimating the term…

Abstract

According to an aspect of the present disclosure, a system-level low voltage ride-through (LVRT) control system for a renewable power plant (RPP) connecting to a weak grid is provided. The system includes a voltage boundary vector trajectory model that captures geometric relationships of system-side responses to determine voltage controllable boundaries. The system includes a discrete and clustering matrix-based calculation algorithm that computes optimal current commands within the constructed boundaries.

Claims1

Dependent claims

A method for system-level low voltage ride-through control of a renewable power plant connected to a weak grid and including a plurality of units, the method comprising:

determining voltage controllable boundaries by capturing geometric relationships of system-side responses using a voltage boundary vector trajectory model that accounts for transformer connection transformations, wherein voltage controllable boundaries are determined using:
V
lim
2
=
(
X
∑
⁢
I
Q
+
+
A
U
)
2
+
(
-
X
∑
⁢
I
Q
-
+
V
g
-
)
2
+
2
⁢
(
X
∑
⁢
I
Q
+
+
A
U
)
⁢
(
-
X
∑
⁢
I
Q
-
+
V
g
-
)
⁢
cos
⁡
(
γ
P
⁢
C
⁢
C
+
Δγ
-
k
⁢
π
3
)
A
U
=
V
g
+
2
-
(
X
∑
⁢
I
P
+
)
2
,
Δγ
=
X
∑
(
I
P
+
-
I
P
.
❘
"\[LeftBracketingBar]"
0
❘
"\[RightBracketingBar]"
+
)
/
V
g
+
k
=
0
,
1
,
2
,
3
,
4
,
5
wherein the XΣ, Vg+ and Vg− is measured by an online impedance estimator;
discretizing positive sequence reactive current IQ+ to an m-dimensional vector where m denotes discrete resolution, and wherein:
I
Q
.
des
+
=
[
0
:
I
lim
2
-
I
P
+
2
/
m
:
I
lim
2
-
I
P
+
2
]
(
16
)
where m denotes discrete resolution;
substituting the discretized IQ.des+ into voltage boundary equations to solve for vectors about negative sequence reactive current IQ−;
grouping the solved vectors into two matrices Bup and Bdown according to norm of each solution vector, wherein:
{
B
up
=
[
I
Q
.
des
1.1
.1
-
L
I
Q
.
des
⁢
1.1
.
k
-
M
O
M
I
Q
.
des
1.
m
.1
-
L
I
Q
.
des
1.
m
.
k
-
]
B
down
=
[
I
Q
.
des
2.1
.1
-
L
I
Q
.
des
⁢
2.1
.
k
-
M
O
M
I
Q
.
des
2.
m
.1
-
L
I
Q
.
des
2.
m
.
k
-
]
where:
I
Q
-
.
des
1.
m
.
k
and
I
Q
-
.
des
2.
m
.
k
denote the two solutions obtained from the k-th equation at the m-th discrete point;
and
M, L, and O are placeholders, indicating values of
I
Q
=
.
des
1.
m
.
k
and
I
Q
=
.
des
2.
m
.
k
across rows and columns;
calculating a maximum value of each row of the Bup and a minimum value of each row of the Bdown and combine them into Iup and Idown respectively, such that:
Iup.i≤Idown.i
computing optimal current commands within the voltage controllable boundaries using the grouped matrices;
transmitting the optimal current commands to all units within the renewable power plant, wherein the units include wind turbines, photovoltaics, and static var generators;
at a grid-connected inverter for each unit, mathematically transforming an optimal current command issued to the unit to obtain a switching signal of a thyristor;
and
controlling the output three-phase current of the unit using the switching signal calculated from the optimal current command issued to the unit.

303 more elements

Dependencies are inferred from the claim text.

Facts

Application: 19/321,403Filed 8 Sep 2025
Granted: 4 Aug 2026
Term ends: Not estimatedThe source records don’t support an estimate.

Classification7 codes

H02J 3/16
Arrangements for adjusting voltage in AC networks by changing a characteristic of the network load: by adjustment of reactive power
H02J 3/381
Arrangements for feeding a single network from two or more generators or sources in parallel; Arrangements for feeding already energised…
H02J 3/50
Controlling the sharing of generated power between the generators, sources or networks: controlling the sharing of reactive power
H02J 2101/28
Dispersed power generation using renewable energy sources: wind energy

Family

No related US applications are recorded in the indexed filing history.

Timeline

Citations

Open elsewhere

patentgrep

Loading patent…

Abstract

A method for system-level low voltage ride-through control of a renewable power plant connected to a weak grid and including a plurality of units, the method comprising:

determining voltage controllable boundaries by capturing geometric relationships of system-side responses using a voltage boundary vector trajectory model that accounts for transformer connection transformations, wherein voltage controllable boundaries are determined using:
V
lim
2
=
(
X
∑
⁢
I
Q
+
+
A
U
)
2
+
(
-
X
∑
⁢
I
Q
-
+
V
g
-
)
2
+
2
⁢
(
X
∑
⁢
I
Q
+
+
A
U
)
⁢
(
-
X
∑
⁢
I
Q
-
+
V
g
-
)
⁢
cos
⁡
(
γ
P
⁢
C
⁢
C
+
Δγ
-
k
⁢
π
3
)
A
U
=
V
g
+
2
-
(
X
∑
⁢
I
P
+
)
2
,
Δγ
=
X
∑
(
I
P
+
-
I
P
.
❘
"\[LeftBracketingBar]"
0
❘
"\[RightBracketingBar]"
+
)
/
V
g
+
k
=
0
,
1
,
2
,
3
,
4
,
5
wherein the XΣ, Vg+ and Vg− is measured by an online impedance estimator;
discretizing positive sequence reactive current IQ+ to an m-dimensional vector where m denotes discrete resolution, and wherein:
I
Q
.
des
+
=
[
0
:
I
lim
2
-
I
P
+
2
/
m
:
I
lim
2
-
I
P
+
2
]
(
16
)
where m denotes discrete resolution;
substituting the discretized IQ.des+ into voltage boundary equations to solve for vectors about negative sequence reactive current IQ−;
grouping the solved vectors into two matrices Bup and Bdown according to norm of each solution vector, wherein:
{
B
up
=
[
I
Q
.
des
1.1
.1
-
L
I
Q
.
des
⁢
1.1
.
k
-
M
O
M
I
Q
.
des
1.
m
.1
-
L
I
Q
.
des
1.
m
.
k
-
]
B
down
=
[
I
Q
.
des
2.1
.1
-
L
I
Q
.
des
⁢
2.1
.
k
-
M
O
M
I
Q
.
des
2.
m
.1
-
L
I
Q
.
des
2.
m
.
k
-
]
where:
I
Q
-
.
des
1.
m
.
k
and
I
Q
-
.
des
2.
m
.
k
denote the two solutions obtained from the k-th equation at the m-th discrete point;
and
M, L, and O are placeholders, indicating values of
I
Q
=
.
des
1.
m
.
k
and
I
Q
=
.
des
2.
m
.
k
across rows and columns;
calculating a maximum value of each row of the Bup and a minimum value of each row of the Bdown and combine them into Iup and Idown respectively, such that:
Iup.i≤Idown.i
computing optimal current commands within the voltage controllable boundaries using the grouped matrices;
transmitting the optimal current commands to all units within the renewable power plant, wherein the units include wind turbines, photovoltaics, and static var generators;
at a grid-connected inverter for each unit, mathematically transforming an optimal current command issued to the unit to obtain a switching signal of a thyristor;
and
controlling the output three-phase current of the unit using the switching signal calculated from the optimal current command issued to the unit.

303 more elements

Facts

Application

19/321,403Filed 8 Sep 2025

Granted

4 Aug 2026

Term ends

Not estimatedThe source records don’t support an estimate.

Classification7 codes

H02J 3/16
Arrangements for adjusting voltage in AC networks by changing a characteristic of the network load: by adjustment of reactive power
H02J 3/381
Arrangements for feeding a single network from two or more generators or sources in parallel; Arrangements for feeding already energised…
H02J 3/50
Controlling the sharing of generated power between the generators, sources or networks: controlling the sharing of reactive power
H02J 2101/28
Dispersed power generation using renewable energy sources: wind energy