# US 10,871,795 B2 · Electric power system

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- Number: US 10,871,795 B2
- Document ID: US10871795B2
- Status: Granted
- Kind: B2
- Application number: 16/081,276
- Filed: 2017-02-24
- Published: 2020-06-11
- Granted: 2020-12-22
- Earliest claimed: 2016-03-02
- Assignees: DAIHEN Corporation
- Applicants: Daihen Corporation
- Inventors: Akihiro Ohori; Nobuyuki Hattori
- Web page: https://patentgrep.com/patent/US10871795B2

## CPC

- G05F 1/67: to the maximum power available from a generator, e.g. from solar cell
- H02J 3/32: using batteries or super capacitors with converting means
- H02J 3/38: Arrangements for feeding a single network from two or more generators or sources in parallel; Arrangements for feeding already energised networks from additional generators or sources in parallel
- H02J 3/46: Controlling the sharing of generated power between the generators, sources or networks
- H02J 7/35: with light sensitive cells
- H02J 13/00: Circuit arrangements for providing remote monitoring or remote control of equipment in a power distribution network
- H02J 13/1331: {using wireless data transmission}
- H02J 2101/24: Photovoltaics
- Y02E 10/56: Power conversion systems, e.g. maximum power point trackers
- Y02E 40/70: Smart grids as climate change mitigation technology in the energy generation sector
- Y02E 60/00: Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y04S 10/123: the energy generation units being or involving renewable energy sources
- Y04S 40/126: using wireless data transmission
- G05F: SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
- H02J: ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y04S: SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS

## Abstract

A power system includes a plurality of power conditioners, and a central management device that manages the plurality of power conditioners. The central management device includes a detector and an index calculator. The detector detects regulation subject power. The index calculator calculates an index for controlling individual output powers of the plurality of power conditioners such that the regulation subject power matches with target power. Each of the plurality of power conditioners includes a target power calculator and a controller. The target power calculator calculates the individual target power of the power conditioner based on an optimization problem using the index. The controller regulates the individual output power to the individual target power.

## Claims

### Claim 1

A power system connected to a power grid, comprising:
a plurality of power conditioners; and
a central management device that manages the plurality of power conditioners,
wherein the central management device includes:
a detector that detects regulation subject power;
an index calculator that calculates an index for controlling individual output powers of the plurality of power conditioners such that the regulation subject power matches with target power, the calculating of the index being based on the regulation subject power and the target power; and
a transmitter that transmits the index to the plurality of power conditioners,
wherein each of the plurality of power conditioners includes:
a receiver that receives the index;
a target power calculator that calculates the individual target power of the power conditioner based on an optimization problem using the index; and
a controller that regulates the individual output power of the power conditioner to the individual target power.

### Claim 2 (depends on 1)

The power system according to claim 1,
wherein the plurality of power conditioners include n photovoltaic power conditioners (n being a positive integer) that receive power from solar cells,
wherein the index calculator calculates a suppression index as the index for the photovoltaic power conditioners, and
wherein the transmitter transmits the suppression index to the photovoltaic power conditioners.

### Claim 3 (depends on 2)

The power system according to claim 2,
wherein when pr denotes the suppression index, Piref (i=an integer of 1, . . . , n) denotes the individual target power of each of the n photovoltaic power conditioners, Pilmt denotes a rated output of each of the n photovoltaic power conditioners, and wj denotes a weight for an output control of each of the n photovoltaic power conditioners, the individual target power Piref is calculated by solving an optimization problem defined by the following formula (1).
min
P
i
ref
⁢
{
w
i
⁡
(
P
i
ref
-
P
i
lmt
)
2
+
pr
⁡
(
P
i
ref
-
P
i
lmt
)
}
subject
⁢
⁢
to
⁢
⁢
0
≤
P
i
ref
≤
P
i
lmt
⁢
)
.
(
1
)

### Claim 4 (depends on 2)

The power system according to claim 2, wherein when Piout(t) denotes the individual output power of each of the n photovoltaic power conditioners, PC(t) denotes the target power, and P(t) denotes the regulation subject power, the index calculator calculates the suppression index pr by solving the following formulas (2) and (3),
d
⁢
⁢
λ
dt
=
ɛ
⁡
(
∑
i
=
1
n
⁢
⁢
P
i
out
⁡
(
t
)
-
P
c
⁡
(
t
)
)
,
ɛ
>
0
=
ɛ
⁡
(
P
⁡
(
t
)
-
P
c
⁡
(
t
)
)
(
2
)
pr
=
λ
(
3
)
Note that c denotes a gradient coefficient.

### Claim 5 (depends on 2)

The power system according to claim 2,
wherein the plurality of power conditioners include m storage cell power conditioners (m being a positive integer) that receive power from storage cells or output power to the storage cells,
wherein the index calculator calculates a charge/discharge index as the index for the storage cell power conditioners, and
wherein the transmitter transmits the charge/discharge index to the storage cell power conditioners.

### Claim 6 (depends on 5)

The power system according to claim 5,
wherein when prpv denotes the suppression index, PPViref (i=an integer of 1, . . . , n) denotes the individual target power of each of the n photovoltaic power conditioners, PPVilmt denotes a rated output of each of the n photovoltaic power conditioners, wPVi denotes a weight for an output control of each of the n photovoltaic power conditioners, and Pit denotes a design parameter indicating whether to prioritize suppression of the individual output power of each of the n photovoltaic power conditioners, the individual target power PPViref is calculated by solving an optimization problem defined by the following formula (4), and
wherein when prB denotes the charge/discharge index, PBkref (k=an integer of 1, . . . , m) denotes the individual target power of each of the m storage cell power conditioners, PBklmt denotes a rated output of each of the m storage cell power conditioners, wBk denotes a weight for an output control of each of the m storage cell power conditioners, and αk and βk denote parameters set according to a remaining amount of each of the storage cells, the individual target power PBkref is calculated by solving an optimization problem defined by the following formula (5).
min
P
PVi
ref
⁢
{
w
PVi
⁡
(
P
PVi
ref
-
P
φ
⁢
⁢
i
)
2
+
pr
PV
⁡
(
P
PVi
ref
-
P
φ
⁢
⁢
i
)
}
subject
⁢
⁢
to
⁢
⁢
0
≤
P
PVi
ref
≤
P
PVi
lmt
⁢
)
(
4
)
min
P
VBk
ref
⁢
{
w
VBk
⁡
(
P
Bk
ref
)
2
+
pr
B
⁡
(
P
Bk
ref
)
}
⁢
subject
⁢
⁢
to
⁢
-
P
Bk
lmt
≤
P
Bk
ref
≤
P
Bk
lmt
α
k
≤
P
Bk
ref
≤
β
k
⁢
)
.
(
5
)

### Claim 7 (depends on 5)

The power system according to claim 5,
wherein when prPV denotes the suppression index, PPViref (i=an integer of 1, . . . , n) denotes the individual target power of each of the n photovoltaic power conditioners, PPVilmt denotes a rated output of each of the n photovoltaic power conditioners, wPVi denotes a weight for an output control of each of the n photovoltaic power conditioners, Pφi denotes a design parameter indicating whether to prioritize suppression of the individual output power of each of the n photovoltaic power conditioners, QPVi denotes an output of reactive power, SPVid denotes a maximum apparent power that can be output, VPVi denotes a connection point voltage of each of the n photovoltaic power conditioners, and V0 denotes a connection point reference voltage, the individual target power PPViref is calculated by solving an optimization problem defined by the following formula (4′), and wherein when prB denotes the charge/discharge index, PBkref (k=an integer of 1, . . . , m) denotes the individual target power of each of the m storage cell power conditioners, PBklmt denotes a rated output of each of the m storage cell power conditioners, PSMklmt denotes a charge rated output of each of the storage cells, PSPklmt denotes a discharge rated output of each of the storage cells, wBk denotes a weight for an output control of each of the m storage cell power conditioners, αk and βk denote parameters set according to a remaining amount of each of the storage cells, wSOCk denotes a weight corresponding to a state of charge of each of the storage cells, QBk denotes an output of reactive power, SBkd denotes a maximum apparent power that can be output, VBk denotes a connection point voltage of each of the m storage cell power conditioners, and V0 denotes a connection point reference voltage, the individual target power PBkref is calculated by solving an optimization problem defined by the following formula (5′).
min
P
PVi
ref
⁢
{
w
PVi
⁡
(
P
PVi
ref
-
P
φ
⁢
⁢
i
)
2
+
pr
PV
⁡
(
P
PVi
ref
-
P
φ
⁢
⁢
i
)
}
subject
⁢
⁢
to
⁢
⁢
0
≤
P
PVi
ref
≤
P
PVi
lmt
⁢
⁢
(
P
PVi
ref
)
2
+
(
Q
PVi
)
2
≤
(
S
PVi
d
⁢
V
PVi
V
0
)
2
)
(
4
′
)
min
P
Bk
ref
⁢
{
w
Bk
⁢
w
SOCk
⁡
(
P
Bk
ref
)
2
+
pr
B
⁡
(
P
Bk
ref
)
}
subject
⁢
⁢
to
⁢
-
P
Bk
lmt
≤
P
Bk
ref
≤
P
Bk
lmt
⁢
⁢
P
SMk
lmt
≤
P
Bk
ref
≤
P
SPk
lmt
⁢
α
k
≤
P
Bk
ref
≤
β
k
⁢
(
P
Bk
ref
)
2
+
(
Q
Bk
)
2
≤
(
S
Bk
d
⁢
V
Bk
V
0
)
2
)
.
(
5
′
)

### Claim 8 (depends on 5)

The power system according to claim 5, wherein when PPViout(t) denotes the individual output power of each of the n photovoltaic power conditioners, PBkout(t) denotes the individual output power of each of the m storage cell power conditioners, PC(t) denotes the target power, P(t) denotes the regulation subject power, prPV denotes the suppression index, and prB denotes the charge/discharge index, the index calculator calculates the suppression index PrPV and the charge/discharge index PrB with use of the following formulas (6) and (7),
d
⁢
⁢
λ
dt
=
ɛ
⁡
(
∑
i
=
1
n
⁢
⁢
(
P
PVi
out
⁡
(
t
)
)
+
∑
k
=
1
m
⁢
⁢
(
P
Bk
out
⁡
(
t
)
)
-
P
C
⁡
(
t
)
)
,
ɛ
>
0
=
ɛ
⁡
(
P
⁡
(
t
)
-
P
c
⁡
(
t
)
)
(
6
)
pr
PV
=
pr
B
=
λ
(
7
)
where ε denotes a gradient coefficient.

### Claim 9 (depends on 1)

The power system according to claim 1, wherein the regulation subject power is a power at a connection point of the plurality of power conditioners and the power grid.

### Claim 10 (depends on 1)

The power system according to claim 1,
wherein the central management device further includes: an acquiring unit that acquires the individual output powers of the plurality of power conditioners; and a total output power calculator that calculates a total output power which is a sum of the individual output powers of the plurality of power conditioners, and
wherein the regulation subject power is the total output power.

### Claim 11 (depends on 1)

The power system according to claim 1, wherein a load that consumes power is connected to the connection point of the plurality of power conditioners and the power grid.

### Claim 12 (depends on 1)

The power system according to claim 1,
wherein a load that consumes power is connected to the connection point of the plurality of power conditioners and the power grid,
wherein the central management device further includes: an acquiring unit that acquires the individual output powers of the plurality of power conditioners, and that acquires power consumption of the load; a total output power calculator that calculates a total output power that is a sum of the individual output powers of the plurality of power conditioners; and a connection point power estimator that estimates a power at the connection point, based on the total output power and the power consumption, and
wherein the regulation subject power is the power at the connection point.

### Claim 13 (depends on 1)

The power system according to claim 1,
wherein the central management device further includes an acquiring unit that acquires an output command from a power company via wireless communication, and
wherein the target power is a target value based on the output command.

### Claim 14 (depends on 1)

The power system according to claim 1,
wherein the central management device further includes a setting unit that sets an upper limit value of power supplied from the power grid, and
wherein the target power is a target value based on the upper limit value.

### Claim 15 (depends on 14)

The power system according to claim 14, wherein when at least one of the plurality of power conditioners is connected to any of the solar cells, the index calculator calculates the index for the at least one power conditioner as 0.

### Claim 16 (depends on 1)

The power system according to claim 1,
wherein the central management device further includes a setting unit that sets a reverse power flow prevention target, and
wherein the target power is a target value based on the reverse power flow prevention target.

### Claim 17 (depends on 1)

The power system according to claim 1,
wherein the plurality of power conditioners are divided into a plurality of groups, and
wherein in at least one of the plurality of groups, a control is performed such that a sum of the individual output powers of all power conditioners in the group indicates a predetermined target value.