# US 12,009,659 B1 · System and method of fault analysis of inverter-interfaced renewable energy source considering decoupled sequence control

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 12,009,659 B1
- Document ID: US12009659B1
- Status: Granted
- Kind: B1
- Application number: 18/203,474
- Filed: 2023-05-30
- Granted: 2024-06-11
- Earliest claimed: 2023-05-30
- Assignees: North China Electric Power University
- Applicants: North China Electric Power University
- Inventors: Tianshu Bi; Ke Jia; Qian Liu; Hao Liu; Cheng Wang
- Web page: https://patentgrep.com/patent/US12009659B1

## CPC

- H02J 3/001: Arrangements for handling faults or abnormalities, e.g. emergencies or contingencies
- H02J 3/381: {Dispersed generators}
- H02J 2101/24: Photovoltaics
- H02J 2103/30: Simulating, planning, modelling, reliability check or computer assisted design [CAD] of electric power networks
- H02J: ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY

## Abstract

A method for analytically studying fault responses of an inverter-interfaced renewable energy source (IIRES). The IIRES includes a decoupled sequence control (DSC) system, and the DSC system includes a converter, a current controller, a low-voltage ride-through (LVRT) control unit, and positive and negative sequence components calculation (PNSCC) structures. The method includes: determining a detailed fault model of the IIRES; determining a unified model of the PNSCC structures; determining a simplified fault model of the IIRES in a fault detection phase; determining a simplified fault model of the IIRES in a control transient response (CTR) phase; detecting a short-circuit fault; cutting off an outer loop of the DSC system; switching the DSC system to a current control mode through the LVRT unit by the current controller; analyzing the short-circuit fault; and designing an enhanced fault-ride-through control of the IIRESs to suppress an inrush current to protect the IIRES.

## Claims

### Claim 1

A method for controlling an inverter-interfaced renewable energy source (IIRES), wherein the IIRES includes a converter, a decoupled sequence control (DSC) system and a power filter, and the DSC system includes a current controller, a low-voltage ride-through (LVRT) control unit, and a positive and negative sequence components calculation (PNSCC) structure including a dual synchronous reference frame (DSRF)-based PNSCC structure, a dual complex-coefficient filter (DCCF)-based PNSCC structure; a dual second-order generalized integrator (DSOGI)-based PNSCC structure, a delayed signal cancellation (dsc)-based PNSCC structure, and a notch filter (NF)-based PNSCC structure, the method comprising:
determining the PNSCC structures in a synchronous reference frame (SRF), as
X
ˆ
d
⁢
q
(
s
)
=
H
φ
(
s
)
⁢
X
d
⁢
q
(
s
)
=
[
H
1
⁢
1
L
H
1
⁢
4
M
O
M
H
4
⁢
1
L
H
4
⁢
4
]
⁢
X
d
⁢
q
(
s
)
;
(
4
)
where s is a Laplace operator, Xdq(s)=[Xd+(s), Xd−(s), Xq−(s), Xq−(s)]T denotes a value of the grid current, an inverter output voltage or a terminal voltage, {circumflex over (X)}dq(s)=[{circumflex over (X)}d+(s), {circumflex over (X)}q+(s), {circumflex over (X)}d−(s), {circumflex over (X)}q−(s)]T represents an estimated value of Xdq(s), which is extracted by the PNSCC, Hφ(s) is an objective transfer function of PNSCC, H11˜H44 are elements of Hφ(s) H22=H33=H44=H11, H21=H34=−H43=−H12, H31=H42=H24=H13, and H41=−H32=−H23=H14, and superscript φ∈{DSRF, DCCF, DSOGI, dsc, NF};
determining transfer function HDSRF(s)=HDCCF(s) for the DSRF-based PNSCC structure and the DCCF-based PNSCC structure, as
H
1
⁢
1
=
ω
p
⁢
s
3
+
2
⁢
ω
p
2
⁢
s
2
+
4
⁢
ω
2
⁢
ω
p
⁢
s
+
4
⁢
ω
2
⁢
ω
p
2
s
4
+
4
⁢
ω
p
⁢
s
3
+
4
⁢
(
ω
2
+
ω
p
2
)
⁢
s
2
+
8
⁢
ω
2
⁢
ω
p
⁢
s
+
4
⁢
ω
2
⁢
ω
p
2
H
1
⁢
2
=
-
2
⁢
ω
⁢
ω
p
2
⁢
s
s
4
+
4
⁢
ω
p
⁢
s
3
+
4
⁢
(
ω
2
+
ω
p
2
)
⁢
s
2
+
8
⁢
ω
2
⁢
ω
p
⁢
s
+
4
⁢
ω
2
⁢
ω
p
2
H
1
⁢
3
=
(
s
+
2
⁢
ω
p
)
⁢
ω
p
⁢
s
2
s
4
+
4
⁢
ω
p
⁢
s
3
+
4
⁢
(
ω
2
+
ω
p
2
)
⁢
s
2
+
8
⁢
ω
2
⁢
ω
p
⁢
s
+
4
⁢
ω
2
⁢
ω
p
2
H
1
⁢
4
=
2
⁢
(
s
+
ω
p
)
⁢
ω
⁢
ω
p
⁢
s
s
4
+
4
⁢
ω
p
⁢
s
3
+
4
⁢
(
ω
2
+
ω
p
2
)
⁢
s
2
+
8
⁢
ω
2
⁢
ω
p
⁢
s
+
4
⁢
ω
2
⁢
ω
p
2
;
(
10
)
where ωp is a cutoff frequency of an adopted low-pass filter in the DSRF- or DCCF-based PNSCC, and ω=100π;
determining transfer function HDSOGI(s) for the DSOGI-based PNSCC structure, as
H
1
⁢
1
=
k
⁢
ω
⁢
s
3
+
k
2
⁢
ω
2
⁢
s
2
+
4
⁢
k
⁢
ω
3
⁢
s
+
2
⁢
k
2
⁢
ω
4
2
⁢
s
4
+
4
⁢
k
⁢
ω
⁢
s
3
+
2
⁢
(
k
2
+
4
)
⁢
ω
2
⁢
s
2
+
8
⁢
k
⁢
ω
3
⁢
s
+
2
⁢
k
2
⁢
ω
4
H
1
⁢
2
=
-
k
2
⁢
ω
3
⁢
s
2
⁢
s
4
+
4
⁢
k
⁢
ω
⁢
s
3
+
2
⁢
(
k
2
+
4
)
⁢
ω
2
⁢
s
2
+
8
⁢
k
⁢
ω
3
⁢
s
+
2
⁢
k
2
⁢
ω
4
H
1
⁢
3
=
k
⁢
ω
⁡
(
s
+
k
⁢
ω
)
⁢
s
2
2
⁢
s
4
+
4
⁢
k
⁢
ω
⁢
s
3
+
2
⁢
(
k
2
+
4
)
⁢
ω
2
⁢
s
2
+
8
⁢
k
⁢
ω
3
⁢
s
+
2
⁢
k
2
⁢
ω
4
H
1
⁢
4
=
k
⁢
ω
⁡
(
2
⁢
s
+
k
⁢
ω
)
⁢
ω
⁢
s
2
⁢
s
4
+
4
⁢
k
⁢
ω
⁢
s
3
+
2
⁢
(
k
2
+
4
)
⁢
ω
2
⁢
s
2
+
8
⁢
k
⁢
ω
3
⁢
s
+
2
⁢
k
2
⁢
ω
4
;
(
11
)
where k is a constant parameter used in DSOGI:
determining transfer function Hdsc(s) for the dsc-based PNSCC structure, as
H
1
⁢
1
=
1
+
e
-
sT
2
,
H
1
⁢
2
=
0
,
H
1
⁢
3
=
H
1
⁢
1
⁢
s
2
s
2
+
4
⁢
ω
2
,
H
1
⁢
4
=
H
1
⁢
1
⁢
2
⁢
ω
⁢
s
s
2
+
4
⁢
ω
2
H
2
⁢
2
=
H
3
⁢
3
=
H
4
⁢
4
=
H
1
⁢
1
,
H
2
⁢
1
=
H
3
⁢
4
=
-
H
4
⁢
3
=
-
H
1
⁢
2
H
3
⁢
1
=
H
4
⁢
2
=
H
2
⁢
4
=
H
1
⁢
3
,
H
4
⁢
1
=
-
H
3
⁢
2
=
-
H
2
⁢
3
=
H
1
⁢
4
;
(
13
)
where T=Tg/4 and Tg is a time cycle of the grid voltage;
determining transfer function HNF(s) for the NF-based PNSCC structure, as
H
1
⁢
1
=
N
⁢
F
⁢
(
s
)
,
H
1
⁢
2
=
0
,
H
1
⁢
3
=
H
1
⁢
1
⁢
s
2
s
2
+
4
⁢
ω
2
,
H
1
⁢
4
=
H
1
⁢
1
⁢
2
⁢
ω
⁢
s
s
2
+
4
⁢
ω
2
H
2
⁢
2
=
H
3
⁢
3
=
H
4
⁢
4
=
H
1
⁢
1
,
H
2
⁢
1
=
H
3
⁢
4
=
-
H
4
⁢
3
=
-
H
1
⁢
2
H
3
⁢
1
=
H
4
⁢
2
=
H
2
⁢
4
=
H
1
⁢
3
,
H
4
⁢
1
=
-
H
3
⁢
2
=
-
H
2
⁢
3
=
H
1
⁢
4
;
(
15
)
where NF(s) denotes a transfer function of a notch filter, and NF(s)=(s2+ωNF2)/(s2+2kNFωNFS+ωNF2), kNF and ωNF are constant parameters used in the notch filter;
determining from the equations (4), (10), (11), (13) and (15) a fault equation of the IIRES with the DSC, as
Idq(s)=Gm−1(s)(PI(s)JIdq*(s)+(Hφ(s)−J)Edq(s)) (18);
where Idq(s), Idq*(s) and Edq(s) denote a grid current equation, a grid current reference equation and a terminal voltage equation in a frequency domain, respectively, PI(s) is a transfer function of a proportional-integral controller, PI(s)=(kp+ki/s), kp and ki are a proportional gain and an integral gain, Gm(s) is a 4×4 matrix covering G11˜G44, G11=PI(s)H11+Pd(s)+ωLH21, G12=PI(s)H12+ωL(H22−1), G13=PI(s)H13+ωLH23, G14=PI(s)H14+ωLH24, and G22=G33=G44=G11, G21=G34=−G43=−G12, G31=G42=G24=G13, and G41=−G32=−G23=G14, Pd(s) is a damping term attributed to a power filter and Pd(s)=(Ls+R), R and L are total resistance and total inductance of the power filter, J is an identity matrix;
using the transfer functions HDSRF(s), HDCCF(s), HDSOGI(s), Hdsc(s) and HNF(s), determining from the equation (4) an equation of the PNSCC structures in the SRF, as
X
^
d
⁢
q
(
s
)
≈
H
S
φ
(
s
)
⁢
X
d
⁢
q
(
s
)
=
ω
f
s
+
ω
f
⁢
JX
d
⁢
q
(
s
)
;
(
23
)
where a cutoff frequency ωf depends on a type of the PNSCC structure;
from the equations (18) and (23) and by using an inverse Laplace transform, determining a fault equation of the IIRES with the DSC in a fault detection phase, as
i
d
F
⁢
D
+
⁢
(
t
)
=
A
⁢
e
-
(
t
-
t
0
)
/
τ
R
+
e
-
ξω
n
(
t
-
t
0
)
R
⁢
M
⁢
sin
⁢
(
ω
n
⁢
M
⁢
(
t
-
t
0
)
+
φ
1
)
φ
1
=
arctan
⁡
(
M
/
(
ω
n
⁢
τ
-
ξ
)
)
,
t
0
≤
t
≤
t
c
;
(
25
)
where idFD+(t) is a time-domain positive-sequence grid current equation in a fault detection phase, 1/τ=R/L, ωn=(ωcωf)1/2, ζ=ωn/(2ωc), M=(1−ζ2)1/2, 1/A=(ωn−τ)2+M2, and ωc is an open-loop cutoff frequency of a current control loop, ωc=kp/L=ki/R, φ1 is an initial phase angle of idFD+(t), t0 is a fault time, and tc is an end time of the fault detection phase;
from the equations (18) and (23) and by using an inverse Laplace transform, determining a fault equation of the IIRES with the DSC in a control transient response (CTR) phase, as
i
d
CTR
+
⁢
(
t
)
=
1
+
e
-
ξω
n
(
t
-
t
c
)
2
⁢
ξ
⁢
M
⁢
sin
⁢
(
ω
n
⁢
M
⁢
(
t
-
t
c
)
+
φ
2
)
+
i
d
F
⁢
D
+
⁢
(
t
)
φ
2
=
arctan
⁡
(
2
⁢
ξ
⁢
M
/
(
2
⁢
ξ
2
-
1
)
)
,
t
c
≤
t
≤
t
f
;
(
27
)
where idCTR+(t) is a time-domain positive-sequence grid current equation in a control transient response phase, φ2 is an initial phase angle of idCTR+(t), and tf is a start time of a fault steady phase;
detecting a short-circuit fault by the converter and analyzing the short-circuit fault using the equation (25);
switching the DSC system from a first mode to a current control mode through the LVRT unit by the current controller, and analyzing the short-circuit fault using the equation (27); and
suppressing an inrush current to protect the IIRES, wherein the inrush current is a maximum fault current with a peak value exceeding Ilim, which is caused by the existence of PNSCC structure as determined by equation (23) and an fault detection phase.